iTopSpin

Current Posts => Collecting, Modding, Turning and Spin Science => Topic started by: silvertop on August 26, 2014, 11:06:34 PM

Title: Educational size rotational molding machine
Post by: silvertop on August 26, 2014, 11:06:34 PM
This is the machine I used to create the large plastic tops like the one Mark Hayward uses.  It has been sitting around for quite a while, and I have not yet fired it up to make sure it is working, but I assume it will function fine.  It takes about 45 minutes to warm up, and cool down, as I recall. You can Google EMCO and rotational molding for more info.  I am including the mold I had made for making the large tops.  Other molds are available on-line, and this makes a great kid project.  The tops created take some effort to balance properly.  The machine is quite heavy, but I can skid it up on a small skid, and ship at your expense.  Make me an offer.  I just realized that I didn't measure it well... I'm guessing about 20x20x30 and probably about 75 pounds?  I'll put it on our local Craig's List in a couple of weeks in no nibbles here!
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on August 27, 2014, 09:25:00 AM
Neff would love to balance any tops that come out of that!

Keep that thing away from johnm.  The world may not yet be ready for any fantastic creations he would make with it.

Takeshi would enjoy moding those things to death.

Spinningray and Eric would love to talk way into the night on possible things they could do making top creations.

Hope you get a buyer silvertop.  And the whirled would be a better place if it was a top spinner.
Title: Re: Educational size rotational molding machine
Post by: ta0 on August 27, 2014, 11:48:05 AM
Would there be enough interest by members to send it to JohnM in Cincy? I think he could make more use of it than anyone else.
Perhaps we can make a group buy: John gets the machine, Don the money and each member who contributes gets one of these unique large tops? Plus the machine stays in the top community, where it belongs.

I don't know how much money you are looking to get, Don. Freight between Rochester and Cincinnati is probably around $250 (I am guessing).
For example, twenty members putting $50 each would be $1000.  Thirty members at $50 or twenty at $75 each would make it $1500.

This could be a win-win situation for everybody, assuming John wants to have the machine and do the work (and has space in the labs for it). We could even structure it as a donation to the physics lab (it is educational, after all).
Title: Re: Educational size rotational molding machine
Post by: Larry D. on August 27, 2014, 12:07:01 PM
Would there be enough interest by members to send it to JohnM in Cincy? I think he could make more use of it than anyone else.
Perhaps we can make a group buy: John gets the machine, Don the money and each member who contributes gets one of these unique large tops? Plus the machine stays in the top community, where it belongs.

I don't know how much money you are looking to get, Don. Freight between Rochester and Cincinnati is probably around $250 (I am guessing).
For example, twenty members putting $50 each would be $1000.  Thirty members at $50 or twenty at $75 each would make it $1500.

This could be a win-win situation for everybody, assuming John wants to have the machine and do the work (and has space in the labs for it). We could even structure it as a donation to the physics lab (it is educational, after all).

GREAT IDEA Jorge!!!!!   Sign me up!  :D
Title: Re: Educational size rotational molding machine
Post by: jim in paris on August 27, 2014, 12:26:37 PM
i'm in on the project

perhaps Don could donate the machine to the UC Physics Lab
that way we would only have to cover the shipping expenses
 :D :D
jim
Title: Re: Educational size rotational molding machine
Post by: Dick Stohr on August 27, 2014, 12:40:44 PM
I am in!!!!!!!!!!!!!  Maybe Don could donate it to a charity (UC Lab?) for a tax deduction and we pay shipping. Maybe we all buy a top from it and some of the money goes to Don, JohnM uses some for supplies. Several things come to mind Ta0 think it through so that it is a Win,Win,Win.
Title: Re: Educational size rotational molding machine
Post by: yollector on August 27, 2014, 01:30:31 PM
 keep us posted.
       RFC
Title: Re: Educational size rotational molding machine
Post by: Shootist on August 27, 2014, 03:00:06 PM
Good Idea.
Title: Re: Educational size rotational molding machine
Post by: ta0 on August 27, 2014, 04:18:35 PM
I think it is potentially too much money to expect Don to donate it (renting that big space to store the Toycrafter collection must be expensive). And I don't think he would be able to discount it from his taxes as it must be fully amortized. On the other hand, I am currently researching what is needed to establish a non-profit organization to promote tops and organize the contests (more about this in a few days) so the machine could become part of its assets (and everybody could discount his contribution).

Before we go any further with this, we need to know how much Don believes the machine is worth and if this arrangement would work for John.

Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on August 27, 2014, 05:17:11 PM
johnm is currently kind of silent about the idea!
Title: Re: Educational size rotational molding machine
Post by: Jack on August 27, 2014, 07:48:33 PM
johnm is currently kind of silent about the idea!

johnm is watching........waiting:

(http://i1.kym-cdn.com/photos/images/newsfeed/000/415/209/3b4.png)
Title: Re: Educational size rotational molding machine
Post by: johnm on August 27, 2014, 09:22:26 PM
Long busy day since classes are on and some of the seniors in lab are also math majors with a class conflict so our lab make the compromise and runs late for them (but the others start on time-- double hit)

So I’m not saying no, but there are lots of things to sort out, most of which I have not thought of but here are a couple concerns from my side.

Used equipment is often abused equipment.  I’m sure Don treated it well and it functioned properly at the time, but it is old, he got it used and these things often come from schools where non-experts learned how to do things and how not to do things by trial and errors.  In general this means abuse which shortens the useful lifetime of things.   Shipping can often be rough on equipment as well (how brittle are the heating elements?)   I’m not concerned with residual value of the machine for my contribution, but rather the situation if 20 people have invested and the unit experiences a significant failure after just 5 runs of one top at a time.  What is my responsibility to the remaining 15?

I’m not afraid of the work or the time commitment (this was likely a sub-zero return for Don’s time/money investment).  There will be a learning curve for me to get something to work.  I don’t know what plastics are appropriate, reasonable parameters at which the machine should be run, etc.  There will likely be a delay before the first delivery and a significant delay for those at the end of the list since only one is made at a time and at about 2 hours (???) per run production is slow.  I suspect the tip is not made in that machine so a different technique must be used to produce that (perhaps turning from delrin or steel?)  People have been honest in the past about the playability of this top (it is very light for its size and as pointed out requires balancing) so the possibility of disappointment at certain investment levels should be avoided by an upfront statement of what to expect and when to expect it.

There are likely other things to address before hand to CMA but it is late and I’m still tired from festing all weekend ;D, so that’s all for now.
Title: Re: Educational size rotational molding machine
Post by: Neff on August 27, 2014, 11:16:43 PM
This is all very interesting
Title: Re: Educational size rotational molding machine
Post by: silvertop on August 27, 2014, 11:33:38 PM
Wednesday is babysitting day, so haven't gotten around to the forum till now - 11:30 pm - tired.

I like the way this is going, and will come up with numbers, etc. and reply soon!

Thanks for all the interest - we will come up with a plan.
Title: Re: Educational size rotational molding machine
Post by: silvertop on August 28, 2014, 10:29:25 PM
OK - after some thought, pretty much all of the comments are right on the mark.  I will be glad to start it up and see if it heats up, and rotates. Damage in shipping is always a possibility.  I don't remember what plastic I used.  I bought some plastic jars of powdered plastic - I think polyethylene, and some small jars of colorant, but I have no idea where the powdered plastic ended up.  The tips would need to be machined by someone.  I'll be glad to throw in one of the big tops I have with the tip included.  The mold does leave a hole in the bottom to screw in a tip.  The hole is left by the hollow tube that vents the gas that would build up inside.  For whomever hosts the machine, other molds could be created to make all sorts of things.  The top mold is spun copper?

If some sort of group project is undertaken, I would be glad to accept $200. And I will skid it up on a small skid, and ship if the group pays the shipping.  I welcome any additional questions, comments, etc, but really need to move this machine on to someone else.  The same would go for any individual who might want to purchase it.
Title: Re: Educational size rotational molding machine
Post by: ta0 on August 28, 2014, 11:42:32 PM
Thanks Don!  It sounds like a very good price!

The quote I am getting online for sending a 100lb skid from Rochester to Cincinnati by FedEx freight is $160 (2-day freight economy). Say $200 with packing costs. This would make it a $400 total project, what is very doable. I guess we need final agreement by John and it is a go.
John: you need to think how much would be a fair amount to charge for the tops, considering your time and materials. Then we just commit enough "pre-orders" from members (we need very few).

Mark Hayward may have a few extra tips he made for these tops (I need one of those Mark!)

I am already excited thinking on the new things that John may be able to do with this machine!

Title: Re: Educational size rotational molding machine
Post by: johnm on August 29, 2014, 06:46:01 AM
Jorge I sent a PM to you.
Title: Re: Educational size rotational molding machine
Post by: Eric on August 29, 2014, 10:52:38 AM
If johnm wants to do it, I'll definitely contribute to the project!
Title: Re: Educational size rotational molding machine
Post by: Shootist on August 29, 2014, 11:05:18 AM
If John wants the equipment, I'm In!!! With or Without a SpinTop
Title: Re: Educational size rotational molding machine
Post by: Sabaspin on August 29, 2014, 11:50:57 AM
I'm pretty new here, but I'll also contribute and like Shootist, even without a Spintop.
Title: Re: Educational size rotational molding machine
Post by: ta0 on August 29, 2014, 12:25:11 PM
Ok, I got a go from John!  These will be the conditions:

We will accept donations of $20 (no more than 3 donations per person) to send the machine for JohnM so he can experiment with it. If one day he successfully makes some tops using Don's mold, the donors would have first pick and would get a credit of $25 on the top price. It is understood that this may or may not happen, so the money should be considered a donation. In the worst case, we auction the mold among collectors, sell the machine, and any money obtained will go to the future spintop association.

You can post your donation below. There are 20 spots ($20 x 20 = $400).

Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on August 29, 2014, 12:40:09 PM
Yippee!  I just cashed my check and I have some money.  I'm in.
Title: Re: Educational size rotational molding machine
Post by: Larry D. on August 29, 2014, 01:55:30 PM
Great!

Sign me up for 3.  That should be $60.00.
Title: Re: Educational size rotational molding machine
Post by: Sabaspin on August 29, 2014, 02:06:28 PM
A magical and communal rotational top molding machine,
You gotta admit, it sounds like a dream.

Were giant tops will be born and learn to spin,
To play, to mod and see were that leads.

Who knows what marvelous top contraption will be invented,
To whirl away like it's creator intended.

It's a proposition were we all win,
So I won't hesitate to count myself in.

One spot
Title: Re: Educational size rotational molding machine
Post by: Shootist on August 29, 2014, 02:21:29 PM
Put me down for 2 $40.00 dollars. Just let me know where to send the money.
Title: Re: Educational size rotational molding machine
Post by: ta0 on August 29, 2014, 03:44:36 PM
I forgot to say that I am in with $40.

So far:

LarryD $60
Shootist $40
Dick $40
Trompos del Mundo $40
ta0 $40
Sabaspin $20
Jim $20
lincolnrick $20
Earl $20
Eric $20
Kirk $20
Neff $20
Ludo $20




Total committed so far $240 $260 $280 $300 $320 $340 $380
Title: Re: Educational size rotational molding machine
Post by: Dick Stohr on August 29, 2014, 05:47:37 PM
I'll take two = $40.00
Title: Re: Educational size rotational molding machine
Post by: mailman on August 29, 2014, 06:54:18 PM
Not to hijack the thread, but....

Don (silvertop), I sent you a PM a week or so ago.  Did you see it?  If not, let me know, and I'll resend....
Title: Re: Educational size rotational molding machine
Post by: jim in paris on August 30, 2014, 03:44:32 AM
hi all
i'm very glad that this good ol'machine turns out to the root of a community project.../////
like most of you I was on the" with or without a top" line

big thank you john, and be sure that no pressure will be put on you whatsoever ;D ;D
i smile in advance when the delivery takes place >:D

jim
Title: Re: Educational size rotational molding machine
Post by: ta0 on August 30, 2014, 11:12:01 AM
hi all
i'm very glad that this good ol'machine turns out to the root of a community project.../////
like most of you I was on the" with or without a top" line

big thank you john, and be sure that no pressure will be put on you whatsoever ;D ;D
i smile in advance when the delivery takes place >:D

jim
I am with you Jim. Although no tops may come out of this, I have a good hunch that will not be the case. I cannot stop thinking in Don's almost 5-inchers in swirl colors, even though it is not clear if recycled plastic could be used. Also I dream on weird shapes and specially on one that is bouncy (but a rubbery material that can be used in this process would have to be found first). Donors should also get first pick at these  ;D

One unique thing about this rotary molding is that you get a hollow top with no hollowing and just a little hole for outgasing. These tops would float and would be safe to used around rivers and fountains ::)
Title: Re: Educational size rotational molding machine
Post by: lincolnrick on August 30, 2014, 11:58:10 AM
I'm in for 1 - $20
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on August 30, 2014, 12:00:43 PM
Interesting that you should say this, ta0....

"These tops would float and would be safe to be used around rivers and fountains"

But if there would happen to be a strong current on a river (like maybe the Seine in Paris) one would wonder what new possibilities there might be on developing top spinners down river.
Title: Re: Educational size rotational molding machine
Post by: ta0 on August 30, 2014, 02:20:11 PM
Interesting that you should say this, ta0....

"These tops would float and would be safe to be used around rivers and fountains"

But if there would happen to be a strong current on a river (like maybe the Seine in Paris) one would wonder what new possibilities there might be on developing top spinners down river.
Perhaps it was good that the Chico top did not float or I would have risked falling into the Seine to rescue it.
This was not the first time one of my tops met the waters of Paris: ta0 in Paris, 2009 (http://youtube.com/watch?v=Echh_TFtNGQ)

Talking about floating and bouncing tops, I think next time I will take my Wyandotte top:

(http://ta0.com/museum/images/other_tops/Wyandotte-bouncing-top_box-water.jpg)

 ::) ::) ::)
Title: Re: Educational size rotational molding machine
Post by: silvertop on August 30, 2014, 03:37:14 PM
Sounds great!  This group is awesome.

Message sent to mailman with apologies for slow response!
Title: Re: Educational size rotational molding machine
Post by: mailman on August 30, 2014, 04:57:39 PM
Sounds great!  This group is awesome.

Message sent to mailman with apologies for slow response!

Got it!  Thanks!  Hope to see you in the near future....
Title: Re: Educational size rotational molding machine
Post by: Kirk on August 31, 2014, 01:35:48 AM
I'm in for one.
The material must be powdered for rotomolding. There are many resins that have rotomold grades. I did some work a while ago on rotomolded chemical feed systems. I will dig in the files for the material info.
Title: Re: Educational size rotational molding machine
Post by: Jack on August 31, 2014, 02:46:29 AM
The material must be powdered for rotomolding. There are many resins that have rotomold grades. I did some work a while ago on rotomolded chemical feed systems. I will dig in the files for the material info.

good grief kirk what exactly is your line of work?!?!?!?!?
Title: Re: Educational size rotational molding machine
Post by: Kirk on August 31, 2014, 08:40:45 AM
good grief kirk what exactly is your line of work?!?!?!?!?
I do product development consulting. Clients come to us for help on an incredibly wide range of products, including consumer products, surgical instruments, industrial machines and more. It is very rarely boring. Usually we get to work on things that will make a positive difference in people's lives.  My background is Mechanical Engineering with a bit of Electrical.
Title: Re: Educational size rotational molding machine
Post by: ta0 on September 01, 2014, 02:02:13 PM
Here is a photo of the almost 5" wide top The Toycrafter used to make on this machine (the mold is included), besides a regular size Monarch top for comparison:

(http://ta0.com/museum/images/Toycrafter/rotomold-top_Monarch_comparison.jpg)

Of course, John would put a more playable tip.

There are 5 spots left for contributing.

I would not be surprised if there are some nice surprises involved . . .  :-X
Title: Re: Educational size rotational molding machine
Post by: Jack on September 01, 2014, 06:49:36 PM
im considering investing in this but i have a question: if all goes well and tops do get produced from this in the future, what sort of price range would be talking about? i mean a discount of $25 sounds very good but in relation to what total cost?
Title: Re: Educational size rotational molding machine
Post by: ta0 on September 01, 2014, 10:57:48 PM
im considering investing in this but i have a question: if all goes well and tops do get produced from this in the future, what sort of price range would be talking about? i mean a discount of $25 sounds very good but in relation to what total cost?

I don't think the price can be known at this time, but I am sure you will have a taker for your $25 certificate if you don't want the top.
I would say that the odds that your investment will give you a great return (in more than one sense) are very good . . .
Title: Re: Educational size rotational molding machine
Post by: Neff on September 02, 2014, 12:39:55 AM
I am in for one, please.
Title: Re: Educational size rotational molding machine
Post by: silvertop on September 02, 2014, 09:22:57 PM
I've lost track of the $, but this is looking good!
Title: Re: Educational size rotational molding machine
Post by: jim in paris on September 03, 2014, 01:01:23 AM
hi all

Ludo tells me he is in for 20

thanx

jim
Title: Re: Educational size rotational molding machine
Post by: Trompos del Mundo on September 03, 2014, 10:52:46 AM
I am in for 2 $40

Really looking forward to it.
Title: Re: Educational size rotational molding machine
Post by: ta0 on September 04, 2014, 12:47:44 AM
We have basically met our fundraising goal (just one $20 spot left):

LarryD $60
Shootist $40
Dick $40
Trompos del Mundo $40
Earl $40
ta0 $40
Sabaspin $20
Jim $20
Eric $20
Kirk $20
Neff $20
Ludo $20
JNeff $20

Total = $400

Congratulations everybody!

Now please, send your paypal payment to "paypal(at)iTopSpin.com".
IMPORTANT: If you are in the US select the option that says that you are sending a payment to a friend. That way paypal will not charge a commission.
If you don't use paypal, send me a pm and I'll give you my address for sending a check (I already got Larry's!). I'll send the money to Don and we will get the machine on the way to Cincinnati.

I have the feeling that extraordinary things will come from this machine in the hands of John (no pressure  ;D ). It may just take a while.
Title: Re: Educational size rotational molding machine
Post by: JNeff on September 04, 2014, 08:37:42 AM
I'm in for last 20$
Title: Re: Educational size rotational molding machine
Post by: dazzlingdave on September 04, 2014, 09:31:08 AM
I want in for 1 if possible.
Title: Re: Educational size rotational molding machine
Post by: ta0 on September 04, 2014, 10:39:31 AM
I want in for 1 if possible.

I guess we should not turn away any monies. So you are in!
After Don confirms the actual shipping cost, any leftover will go to Johnm to buy consumables.

Thanks!
Title: Re: Educational size rotational molding machine
Post by: silvertop on September 04, 2014, 11:00:29 PM
GREAT!
Title: Re: Educational size rotational molding machine
Post by: ta0 on September 13, 2014, 03:36:42 PM
Thanks to everyone who contributed to this project. I have received a total of $280 (plus $20 were literally lost in the mail  :( ). I am still missing pledges from 5 people ($100).

Don: have you been able to test the machine?
Title: Re: Educational size rotational molding machine
Post by: Neff on September 16, 2014, 12:21:04 PM
I will pay this coming Monday,  sorry for the delay.
Title: Re: Educational size rotational molding machine
Post by: ta0 on September 22, 2014, 11:27:39 PM
Don tested the machine yesterday and everything works including the oven light  :)
He is putting it in a skid and we are figuring the shipping.

I have already in hand $340 of the money pledged and some more is in the mail. The machine should be on its way to John soon  8)
Title: Re: Educational size rotational molding machine
Post by: silvertop on September 27, 2014, 08:31:08 PM
Machine skidded - will call for pick-up tomorrow.

As ta0 posted - everything works at this point.
Title: Re: Educational size rotational molding machine
Post by: ta0 on September 28, 2014, 08:58:46 AM
Excellent!
One more machine to the Cincy mad spintop labs!

These types of project give the forum an extra dimension.
Title: Re: Educational size rotational molding machine
Post by: ta0 on October 03, 2014, 01:27:46 AM
The molding machine on the pallet weighted around 200 lb and the quote came at $290.67. But Don asked around and found an independent shipper that quoted $150. He comes recommended. The only thing is that we need to wait until he travels to Ohio in about 2 weeks.

I updated the list of contributors on the thread above. Thirteen members contributed a total of $400. The actual amount received after Paypal fees on the international transfers was $398.14. Thanks everybody!
Title: Re: Educational size rotational molding machine
Post by: Larry D. on November 29, 2014, 03:33:39 PM
BUMP

But Don asked around and found an independent shipper that quoted $150. He comes recommended. The only thing is that we need to wait until he travels to Ohio in about 2 weeks.
 

2 weeks?
 ???
Update?
Title: Re: Educational size rotational molding machine
Post by: ta0 on November 29, 2014, 04:28:57 PM
This is what I got a few days ago from Don:
Quote
Trucker still has not picked up the machine.  Guess that comes with the discount price?  My topman e-mail is giving me trouble, so hold off on the payment for now.

So the machine is still waiting skidded at Don's place and the money is still in the spintop Paypal account. Hopefully the project will proceed soon.
Title: Re: Educational size rotational molding machine
Post by: poptop on December 03, 2014, 03:34:47 PM
I've been away for a few days and missed this, but glad to pitch in for 1 spot too.

Shipping and powdered plastic funds...

:)
Title: this just in
Post by: johnm on December 20, 2014, 10:41:39 AM
The rotomolder arrived at UC this morning.

(http://farm8.staticflickr.com/7559/16061930021_97f85890b9.jpg)

and I've just opened the box (nice packing job Don, Thanks)

(http://farm8.staticflickr.com/7468/15876428698_e6f5974156.jpg)

Things look in good order, the shippers handled it with care.

Thank everyone, now well see where things will go...
Title: Re: Educational size rotational molding machine
Post by: Neff on December 20, 2014, 06:52:32 PM
YAAAAAYYY!
Title: Re: Educational size rotational molding machine
Post by: ta0 on December 20, 2014, 08:07:40 PM
This is wonderful! I am very excited!

Don did not want to charge any packing expenses, so the total amount I sent him was $350.
There are still about $48 on the paypal account. I will send John a check to pay for supplies.

Thanks to everybody who contributed to this project and specially to Don and John for making it possible!
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on December 20, 2014, 08:08:08 PM
Merry Christmas, johnm.  And Merry Christmas to the rest of the top spinning world.  I think we all may have just received a top gift!!!
Title: Re: Educational size rotational molding machine
Post by: jim in paris on December 21, 2014, 02:46:08 PM
YIPPEE!!

I image a night at the physics lab

close up on
FranKenJohn busy and pausing on molecular tea
slow pan on
the Roto Molder in full action
low angle shot
the were-tops suddenly getting back to life
blurred view of
more coffee mugs waiting for re-incarnation

.....................////////////////////////cut


jim :-X
Title: Re: Educational size rotational molding machine
Post by: silvertop on December 23, 2014, 10:51:07 PM
So glad it arrived safe and sound.... have you plugged it in yet?  Be sure to call if you have any questions.  As I recall, it takes a bit of creativity to get the top mold between the plates.  I had it made as big as I possibly could could fit.  My less expensive trucker took a while to get a run to Ohio, but once he picked it up it was there in under 12 hours!
Title: Re: Educational size rotational molding machine
Post by: johnm on December 24, 2014, 09:25:33 PM
Here is an update on the rotomolder at its new home in Cincinnati.

On Saturday afternoon (it arrived around 10:00 am), I did give the electricals a once over and was comfortable giving it a test run.  The motor worked fine and without the motor on I tested the heating elements to map out the control range of the thermostat.  It seems the original dial type thermometer had long since disappeared so I stuck a thermocouple sensor into the chamber through the port with the thermostat sensor.  The control temperature range for the system is from roughly 125 C to about or slightly above 190 C so it is designed for polyethylene plastic as suspected.  I say about or above because at that temperature the evolving smoke got a bit worrisome so I stopped testing and opened the oven door next to the fume hood.   Turns out someone had been following the instructions to lubricate once a day all the bearings inside the chamber with light oil (printed on the aluminum casting of the rotational arm and again on a decal on the control panel) so there was oil on most surfaces.  Additionally there was a lot of plastic residue on most surfaces as well.  This is not surprising since static electricity it a real problem when dealing with these powders, and the mold flanges have sizable gaps when together  (not to mention a vent hole) so a lot of powder can fall out (and perhaps be thrown around as the mold is spun) before it melts.  So with all this contamination and the smoke issue, I thought it prudent to take everything apart and clean it up before proceeding.  With a lot of hand scraping, glass bead blasting, and some sanding everything cleaned up pretty well.  I also spent some time flattening the mold flanges to get a better joint but it is not close enough to seal so it will get used with a gasket in place to seal that joint.  I also modified the mount in the rotary assembly somewhat to more conveniently hold the mold.  Here are a couple before/after cleaning photos of the oven and the removed rotary parts.

(http://farm8.staticflickr.com/7528/16099067195_c94d8745c6_c.jpg)

(http://farm8.staticflickr.com/7579/16098346292_2d0d069017_c.jpg)

I finished the last of the first round of modifications today and this evening had the initial test run with plastic in the mold.  As source plastic, I’m using lathe swarf from making HDPE tops.  Starting out this is a stringy mess but a little time with a scissor/shear it becomes fairly small flakes and 4 or 5 times the mess.   I was pleased to see the effort was not a complete failure, but it is not a total success either.  The vent tube is stuck in the top so I’ll be redoing the whole capping plug differently for the next run.  The surface of the top is not particularly smooth.   The small flakes have not bonded completely at the surface so it is a bit fuzzy and there are small voids plus one significant void at the flat where the tip goes.  Perhaps with a bit higher temperature and maybe a bit more time at melt temperatures these surface conditions could improve.  The void at the tip is likely going to be hit or miss because the size of the flakes may prevent material from getting to that narrow section before it melts and forms a dam, but I can probably patch that after the fact.   Anyway the exercise served its purpose of testing the machine and pointing out some needed design modifications to make using it a little easier.  Again a sort of before and after with a top body that Don had cut in half and the first attempt from UC.
(http://farm8.staticflickr.com/7530/15913319937_21b09277d5_c.jpg)
Title: Re: Educational size rotational molding machine
Post by: ta0 on December 25, 2014, 01:34:44 AM
On the after photo the mold looks brand new!  :o

It could not be in better hands!
Great things will come from this machine!
Title: Re: Educational size rotational molding machine
Post by: johnm on December 25, 2014, 09:42:12 AM
The top mold is spun copper?

After cleaning it is easy to recognize how the mold halves were made.

The body is a 1/8 inch thick brass ring flange silver soldered to a 0.040 inch thick brass sheet rolled into a cone which has been silver soldered at the seam.  If you look carefully at about the 4 to 5 o'clock position in the picture you can see a solder line from the ring to the small opening on top where the cone was butt joined to itself.

(http://farm8.staticflickr.com/7569/15916964707_c68b3370c1_b.jpg)

The cap is a 1/8 inch thick brass ring flange silver soldered to a 0.040 inch thick brass sheet metal-spun into its shape (like the Trompos Space Mercurio and Neptuno top bodies are metal spun).

(http://farm8.staticflickr.com/7484/16100792751_bc83ea7d04_b.jpg)
Title: Re: Educational size rotational molding machine
Post by: lincolnrick on December 25, 2014, 11:32:12 AM
You're doing such great work with this machine.  The before/after shots are amazing.  Just reading what you've done and what your ideas are for upgrading the workings of the machine make me believe that indeed, great things could be coming.  Thank you for preserving this piece of technology.
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on December 25, 2014, 10:41:43 PM
Wow!  Like lincolnrick said, those before and after shots are stunning.  Very very nice work johnm.

Thanks for sharing your progress.  It is fun to hear.  Good luck as you continue on with this project!

This is certainly another wonderful Christmas message along with Daveid's superglue/string tops.  What a great finish to a great day.
Title: Re: Educational size rotational molding machine
Post by: Dick Stohr on December 25, 2014, 11:42:17 PM
Ditto from me too! WOW !!!!
Title: Re: Educational size rotational molding machine
Post by: johnm on December 26, 2014, 08:15:41 PM
The second round of modifications is finished.  I've replaced the threaded rods and nuts frame work for the inner rotational frame with aluminum standoffs/spacers to make things a little more rigid and easier to get parallel and now the installation/removal of the mold requires just moving 4 wing nuts before pulling the spider and upper clamping plate.  The new capping plug has an alignment hub which fits into the upper clamping plate so the form is now fully confined and aligned by the two plates when installed.  The plug also has a 1/4-20 screw extending into the top body instead of the venting tube thus eliminating the venting feature which I think is not necessary.  The threaded hole left behind in the plastic may or may not be used for mounting the tip.

(http://farm8.staticflickr.com/7555/15929260567_8b6f0331a5_z.jpg)

I didn't notice before the previous update but upon pulling the vent tube from the first top and shaking the top it is obvious there is un-melted plastic remaining inside.  With a slight increase in the thermostat set point and doubling the time at the set point to one hour (the built in timer is only for 30 minutes which is I why I tried that time first) several issues have cleared up.  All the plastic melted and the surface quality is greatly improved.  There was still a bit of a void where the tip installs but I'm not sure there will be a fix for that, so I'll try again with these parameters to check the reproducibility of the result.  I had weighed out about 220 grams of raw materials but the top is about 200 grams so I suppose during the filling process I had lost more than I realized in spillage.  The material was packed in rather tightly so I'm not sure the extra 20 would have fit.  For reference the body that Don sent along is 120 grams--anyone else have a weight for a top body without a tip?

(http://farm9.staticflickr.com/8611/15927589758_6bb8179600_z.jpg)

If I get some consistent results with the new parameters and the tip region is reproducible, I'll begin thinking about the tip design.  I'm not sure what material the tip will be.  The top is on the light side in my opinion, so I don't want to over weight the tip end with a really heavy tip.  Some possibilities include steel, aluminum, or a hybrid based on HDPE melted onto a piece of steel all-thread.
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on December 26, 2014, 10:22:02 PM
Wow!  So cool.  I do have a top like that without a tip.  I do not have a scale nearby, though.  I will have to look around.

Thanks for all your work johnm.  Thanks, also, for all your reporting.  After a long day of trying to catch up, I found it very relaxing to see your post!
Title: Re: Educational size rotational molding machine
Post by: ta0 on December 26, 2014, 11:16:03 PM
Those sound like great updates to the machine.

I wonder if by closing up the venting hole there would be a partial vacuum inside the top when it cools down.

I weighed one of Don's tops without the tip and it measured exactly 130 grams.
Do you think he used less material or lighter plastic? On the one he cut the walls look pretty thick.
Title: Re: Educational size rotational molding machine
Post by: jim in paris on December 27, 2014, 01:55:32 AM
thank you very much for the report , John !
beautiful work, i'm elated ...
and the prototype came out really nice
does is smell a lot ? do you wear a protection during the cooking time ?
about the tip : the " HDPE melted onto a piece of steel all-thread" works really well on your other tops : on mine, the plastic at the tip is barely scratched after a year of use

wishing you the best for the next steps ;)

jim

Title: Re: Educational size rotational molding machine
Post by: johnm on December 27, 2014, 08:16:43 AM
Those sound like great updates to the machine.

I wonder if by closing up the venting hole there would be a partial vacuum inside the top when it cools down.

I weighed one of Don's tops without the tip and it measured exactly 130 grams.
Do you think he used less material or lighter plastic? On the one he cut the walls look pretty thick.

If the plastic envelope is complete, in principle there should be a slight vacuum, but I suspect along the screw there may be some openings and air could leak in around the threads. 

I don't know the density of the material Don used (plus different dyes may add different weights).  The HDPE varieties I'm using certainly have different molecular densities.  The sample that Don cut in half has a thick wall because a significant amount of the powder did not melt together completely, it just lightly fused together suggesting longer time in the oven was needed.  The cross-section is quite open except for the outer shell of about 0.09 inch thick.  It doesn't show well in the picture but the inner surface displays lots of little evenly spaced air bubbles just below the surface (the surface is actually quite smooth).

(http://farm8.staticflickr.com/7544/15496514504_71ca96bcf8_c.jpg)

does is smell a lot ? do you wear a protection during the cooking time ?

Since the cleaning, the smell is minimal and really only noticeable for me right next to the machine.  I think this is mostly from various parts of the machine getting warm and not from the material being melted.  Just in case, I have the oven on a cart in front of a chemical exhaust hood and don't spend much time right next to it.

I do have a top like that without a tip.  I do not have a scale nearby, though.  I will have to look around.

So... I've got a scale and the University is officially closed until Jan. 5 so I'm really on vacation all next week.  Just sayin'.   ;) ;D



Title: Re: Educational size rotational molding machine
Post by: Kirk on December 28, 2014, 01:48:07 AM
  The plug also has a 1/4-20 screw extending into the top body instead of the venting tube thus eliminating the venting feature which I think is not necessary.  The threaded hole left behind in the plastic may or may not be used for mounting the tip.
Rotomolds that I have seen (only a few) have vents that extend into the center of the opening. Thus no powder spills out.

  There was still a bit of a void where the tip installs but I'm not sure there will be a fix for that, so I'll try again with these parameters to check the reproducibility of the result. 
The pros have tricks to locally thicken or thin the walls.  The rate that a spot of the mold heats up affects the fraction of the plastic that melts and sticks to the mold.  Small insulated sections have thin walls. Pin fin heatsinks will locally heat that area faster and add to the wall thickness.

I will try to beg some powder from a supplier.
Title: Re: Educational size rotational molding machine
Post by: johnm on December 28, 2014, 09:13:39 PM
Thanks Kirk for the insights.

Don's original vent tube did go into about the center of the mold but was more or less completely blocked with plastic inside.  I drilled it out before my first run and after the first run it was mostly blocked again so I'm not real confident that no powder would spill out although I didn't notice any of my "flakes" in the oven.  There doesn't seem to be any problem with this particular mold not having a vent.

As far as the tricks go, the mold seems rather well designed with the heat-sink like assembly flanges hopefully causing the walls at this largest diameter to be thicker than the rest and the mass of the plug and clamping plate hopefully adding material to the tip section.  So far the tops have been nice enough that I'm reluctant to saw one open to inspect the cross sectional thicknesses of various regions.  If they continue to be of good quality, I'll probably not sacrifice one until I have at least one for each of the contributing members unless the balance is particularly bad in one of them.  I think my void problem is not a material collection issue due to poor heat distribution but is rather due to the material being completely packed into the mold and initially not being able to roll around and tumble as powder would in a partially filled mold.  The lathe swarf chips or flakes kind of bind together and if there is an unfilled spot while it heats up, that spot could remain empty throughout the process because none of the loose material has an opportunity to fall into it.

Here are some pictures of the materials I'm using.  The swarf in the bags is just the waste from shaping and hollowing the cast HDPE tops.  In the bin is material from the bags selected to fill the mold and then cut up into small bits or flakes to make loading and packing easier.

(http://farm8.staticflickr.com/7526/15945976588_a69e92fa36_b.jpg)

The bits and flakes are loaded into the mold through a funnel via the opening in the body of the mold where the tip will mount.  I use a 1/2 inch dowel to ram in the plastic to maximize the material charge.  The mold is filled and packed to the brim and the end plug with screw then gets pressed in.

(http://farm8.staticflickr.com/7495/16131518421_1e9e97f378_c.jpg)

Here are a couple of the tip mounts where the voids generally appear.  The blue one (third from the left) is nice and complete while the others are not unreasonable and should be reparable with a little hot air filler welding.

(http://farm9.staticflickr.com/8655/15947338489_4ef2ed4797_c.jpg)
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on December 29, 2014, 09:34:26 AM
I am becoming more and more familiar with lathe swarf from my HDPE efforts.  It is pretty special stuff.

What I do not have any experience with is hot air filler molding.  I have seen some pictures of it but have yet to move into that area of HDPE work.  Are you using a hot air blow dryer?

By the way, thanks for your recap and all your pictures.  They look fascinating!!!
Title: Re: Educational size rotational molding machine
Post by: ta0 on December 29, 2014, 11:24:58 AM
Yes, it is very interesting to see the details of your work. Thanks a lot!

I imagine the photograph showing how you fill just half of the mold was only for photographic expediency ???
Title: Re: Educational size rotational molding machine
Post by: jim in paris on December 29, 2014, 12:07:29 PM
oh oh John!
if i understand well , you have already cooked 4 tops ?!!
the mix of colours is incredible
 8) 8)
jim
Title: Re: Educational size rotational molding machine
Post by: johnm on December 29, 2014, 01:05:57 PM
What I do not have any experience with is hot air filler molding.  I have seen some pictures of it but have yet to move into that area of HDPE work.  Are you using a hot air blow dryer?
Since I'm just using hot air welding to fill voids, I want good localized control of the heat and am using a hot air soldering station we bought a long time ago when I had to do a lot of surface mounting of electronic components for one of the experiments.  I'm not sure if a hair dryer gets hot enough for melting HDPE but a heat gun like plumbers etc. might use would certainly have enough power.

I imagine the photograph showing how you fill just half of the mold was only for photographic expediency ???

Sorry for my lack of photography skills and the selection of an ambiguous angle, twice. :-[ ::)  The mold halves are assembled before the loading process, the cap half is just obscured in the picture but you can see the securing nuts, otherwise I'd be filling from the larger opening. ;D  There really is not a practical way to fill the halves and then assemble them since the packed HDPE would just spring back out and go everywhere while trying to fill an open vessel and it certainly would not tolerate tipping up side down to make the assembly.  That was an actual load and became the last top in the row of four.


if i understand well , you have already cooked 4 tops ?!!

The log book says run number 9 is cooling right now. :)  Three tops in one day is possible but it makes a loooong day.  I need to get back to work to recover from my vacation. :P
Title: Re: Educational size rotational molding machine
Post by: ta0 on December 29, 2014, 02:20:43 PM
Quote
. . . otherwise I'd be filling from the larger opening. ;D
I hope so!  ;D
The nuts should have been a giveaway, but the optical illusion that the cone was sitting on the table was very strong. By the way, your photographs look great. I specially like the one you took of the cross section showing the solid external layer and the honeycomb below.
Title: Re: Educational size rotational molding machine
Post by: JNeff on December 29, 2014, 08:05:05 PM
Amazing John. The pictures look great. The technical aspects involved with this are way beyond me. What size are these tops? Are you able to make different sized tops with the molding machine?
Title: Re: Educational size rotational molding machine
Post by: johnm on December 29, 2014, 09:24:33 PM
Amazing John. The pictures look great. The technical aspects involved with this are way beyond me. What size are these tops? Are you able to make different sized tops with the molding machine?

I haven't cleaned up any of the surfaces of the raw tops yet to get any final size measurements.  The cap portion where the string gets anchored is normally where I would hold a top like this in the lathe but this region is sloped a bit and doesn't allow easy chucking so I'll need to think a bit about holding these properly.  I'll probably make a little mount that registers the tip side where the screw was molded in and square up the cap side first so that it can then be turned around to true the tip side.

Anyway the approximate size without tip should be around 5.25 inches tall and about 4.75 inches at the largest diameter.  An appropriate tip will add at least another inch to the overall height giving a final overall height above 6 inches.

Here is one pictured next to a standard Spintastics Trompo Grande.

(http://farm8.staticflickr.com/7520/16143072085_6c1b5bf839_c.jpg)

The rotomolder could function with any size mold that could be mounted into the inner rotating frame but currently there is just the original mold that Don had made.
Title: Re: Educational size rotational molding machine
Post by: johnm on December 30, 2014, 09:33:36 PM
I made a little mandrel to mount the tops to the lathe using the threaded hole left behind by the mold plug and register the top against the 1/2 inch diameter flat inside the tip pocket.  The mandrel has a little relief to allow tool clearance so that the tip end can be machined square and ready to seat the tip.  The cap end of the top is clamped against a flat disk with pressure from a live center in the tailstock.  The cap is lightly clamped and the outer diameter of the cap is indicated to get that diameter running as true as I can for something that is not completely round and slightly wavy.  For this operation, the dial on the indicator moves around like a hand on a clock when the plunger contacting the top moves in and out while the top rotates.  The "high" spot is located and the top is tapped over and the procedure is repeated until the dial moves very little meaning the test surface is centered with respect to the lathe rotation axis.  Once the cap is running true, the tip end is machined so that these two reference surfaces are square.  Then the excess material at the seam between the cap and body of the mold is removed using a file while it spins in the lathe.  This does not ensure that this diameter runs true with the reference surfaces but it is the easiest way to remove that waste material and profile the top to a somewhat pleasing shape without removing a lot of material.  Finally the whole body is rubbed with steel wool while spinning to get rid of most tooling marks and polish it a bit.

(http://farm8.staticflickr.com/7542/16151369182_cdbef6ee79_c.jpg)

(http://farm8.staticflickr.com/7528/15966052969_e09923092e_c.jpg)
Title: Re: Educational size rotational molding machine
Post by: Daveid on December 30, 2014, 09:46:08 PM
those are unbelievably gorgeous...
Title: Re: Educational size rotational molding machine
Post by: ta0 on December 30, 2014, 11:59:50 PM
Sooo nice!  :)

We should all be proud for helping the machine end up in the right hands.
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on December 31, 2014, 02:22:59 AM
wow...Wow...WOW!!!

Merry Christmas and a Happy New Year to us.

Many thanks for your inspiring posts, johnm.  I feel like I am making some good progress up here in Miamisburg with HDPE but then I read what you are doing and cannot help but gasp.

Great work.  Just simply, great great work!!!
Title: Re: Educational size rotational molding machine
Post by: lincolnrick on December 31, 2014, 11:22:54 AM
wow...Wow...WOW!!!

Merry Christmas and a Happy New Year to us.

Many thanks for your inspiring posts, johnm.  I feel like I am making some good progress up here in Miamisburg with HDPE but then I read what you are doing and cannot help but gasp.

Great work.  Just simply, great great work!!!

I cannot add anything to Mikes message as he's said exactly what I would have said. Thank you John for your work.
Title: Re: Educational size rotational molding machine
Post by: poptop on December 31, 2014, 02:23:18 PM
Wow, fantastic work John!  Cant wait to see how you finish them out with tips.

Neffy must be just itching to poke a hole in that cap :)

Carry on man....and happy New Year!
Title: Re: Educational size rotational molding machine
Post by: Dick Stohr on December 31, 2014, 08:54:16 PM
Those are supper looking and I can not wait to see one up close, and LOVE the mostly blue color. VERY WELL DONE JOHN!!!!!!!!!!
Title: Re: Educational size rotational molding machine
Post by: silvertop on January 01, 2015, 10:42:51 PM
WOW!  I'm impressed, and very pleased that someone more knowledgeable that myself is now in charge of the machine!  All I ever did was fill one half of the mold, and then assemble it.  I did always add three or four small C clamps around the rim to better seal the connection point - not sure if I included the little C clamps when I sent the machine.  Not sure where I got the info, but my understanding was that the vent hole was necessary to vent the hot gas from the process, and needed to extend to the center of the mold to avoid powder getting into the tube.  I'm amazed at how good the parts of the machine look after whatever you did to clean them.  I pretty much just used the machine as it came to me, and I had no plastics experience or knowledge.  I know I used some bottles of very finely powdered plastic - I think supplied by the folks who made the machine???  Your attention to detail should give you much better balanced tops than I was ever able to achieve.  Hope I can get one of the tops when you get it all worked out!  Thanks to all who contributed to this project, and especially to John!
Title: Re: Educational size rotational molding machine
Post by: cecil on January 02, 2015, 02:02:34 PM
I have to do the same thing with the Koma, top that I got for Christmas. Put the hole I want in and make a new tip. I'm waiting for my son to go back to work then I have access to the machine shop. You have to know how to do this kind of work, and have the equipment to do it. You have to follow the rules PERPENTICULARITY AND TRUE POSITION AND CONCENTRICITY. And that makes it close to having a good top.
Title: Re: Educational size rotational molding machine
Post by: Neff on January 02, 2015, 11:46:49 PM
poptop you are right, i want to see a hole... nevertheless, the closed crown does look pretty slick!

Awesome work as usual John, I wish I could witness first hand
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on January 03, 2015, 07:15:12 PM
I was questioning johnm about hot air filler molding.

He wrote back "Since I'm just using hot air welding to fill voids, I want good localized control of the heat and am using a hot air soldering station we bought a long time ago when I had to do a lot of surface mounting of electronic components for one of the experiments.  I'm not sure if a hair dryer gets hot enough for melting HDPE but a heat gun like plumbers etc. might use would certainly have enough power."

I have been looking around and doing a little research.  Some are not that expensive.  I sure would like to get one and try it.  It would open up some more doors for me.

Thanks for your help, johnm!!!
Title: Re: Educational size rotational molding machine
Post by: johnm on January 05, 2015, 08:51:37 PM
Your attention to detail should give you much better balanced tops than I was ever able to achieve. 

Don't sell yourself short Don.  The tops you made and the balance you achieved were at the limit of success for this technique.  My success ratio will not be better than yours.  Without complicated features for heat control at various places on the mold as Kirk suggested, the tumbling action of the material inside the mold provides only an approximately uniform distribution of material around the mold.  In reality there is no control over how the material contacts and bonds to other material during the melt cycle.  Vast differences in wall thickness are likely which in addition to providing unbalanced weight distribution, causes non-uniform shrinkage which can distort the shape and contribute to a poorly spinning top.

As Poptop and Neff suggest, these tops are begging to have the crowns opened up (the diet mod).  The novelty of the sealed hollow top is nice so any that are coincidentally balanced will not be opened, but those with poor balance will get the cap turned opened to allow the installation of balancing putty or perhaps even the removal of obviously misplaced plastic.

My attention to detail is most likely unnecessary and over kill.  Think about having a mile of highway to pick up litter and working with a toothbrush to clean up one foot. ::)

On Wednesday the molder displayed an issue with one of the chains that drives the rotation mechanism.  I took that as a sign to move on to the tips for a while.  I made a prototype tip from steel to check the play and decided that steel was the right choice.  The step at the joint between the top body and the tip will be filed flush with the tip before everything is complete.

(http://farm8.staticflickr.com/7560/16208120581_db55636bd3_c.jpg)

To continue with the description of the construction, my approach to making a batch of tips for these top followed the sequence in these pictures of the tip evolution and the basic set up on the lathe.  For making one tip at a time I would machine the whole tip in one mounting on the lathe and machine it out of the bar of stock.  For a lot of them it is faster to cut a bunch of blanks from the stock, set up for each profile, and perform that profile cut on each blank before proceeding to the next profile.  My first set up was to machine the hub that fits into the top body and drill and tap a hole to accept a threaded stud.  Next was to cut the first sloped surface which will match the body angle of the top.  Third was to cut the second angle which defines the other side of the diabolo style neck.  Last was to machine the point.  The point was actually machined to a sharp which was filled to a round such that is felt good spinning in the hand.

(http://farm9.staticflickr.com/8596/16022487948_bc46f3d8e4_o.jpg)

(http://farm8.staticflickr.com/7492/16184128246_c5bdfac207_o.jpg)
Title: Re: Educational size rotational molding machine
Post by: ta0 on January 06, 2015, 11:02:53 AM
Those metal tips are nice! I was expecting plastic tips on these: you have worked hard! You should price them accordingly.

I prefer mine with a closed crown so next time I visit Jim I can use it near a body of water without fear ;D

Title: Re: Educational size rotational molding machine
Post by: dazzlingdave on January 06, 2015, 11:14:26 AM
Awesome work!
Title: Re: Educational size rotational molding machine
Post by: Larry D. on January 06, 2015, 11:16:05 AM
I prefer mine with a closed crown so next time I visit Jim I can use it near a body of water without fear ;D

Even though the top may float you should take a net along with you just in case. 
Unless of course you are willing to go for a swim in the Seine river.  ???
Title: Re: Educational size rotational molding machine
Post by: Sabaspin on January 07, 2015, 03:37:11 PM
WoW.
This is an awesome thread!
Really enjoy reading about the process.
Thanks for posting.
Title: Re: Educational size rotational molding machine
Post by: johnm on January 13, 2015, 07:54:13 PM
I have depleted my swarf supply and done a performance cull based on balance in the hand and on string.  Although most of the tops made are quite playable, these pictured are the ones with a balance that I'm comfortable sending out to project contributors.  Many have surprisingly good balance and the remainder have a noticeable vibration in the hand but not upsetting (to me at least).  I will point out (or warn depending on your perspective) that many of them have an interesting wobble to the motion of the volume of the top as it spins but minimal vibration suggesting the distribution of mass is quite different from that which the shape implies.  This visual wobble does not seem to interfere with play but could be distracting to some players. 

(http://farm9.staticflickr.com/8663/16273527271_d9d3306f15_c.jpg)

(http://farm8.staticflickr.com/7493/15652897734_98b820f100_c.jpg)

(http://farm8.staticflickr.com/7569/16089200919_9efe7444d1_c.jpg)

I'm waiting for some cord that I hope will be appropriate for these tops.  In the next few days I'll be sending a personal message (PM) to the contributors with more details about how thing will likely proceed.  Thanks for following along.
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on January 13, 2015, 08:35:29 PM
So cool.  Or, as I have learned on the Spanish forum, muy chulo!!!

Thanks for that great display and the great pics.
Title: Re: Educational size rotational molding machine
Post by: ta0 on January 13, 2015, 08:48:10 PM
What a gorgeous group of tops!
You should be very proud of your work John!
Thanks for taking over this project and rescuing this part of spintop history (and in the process writing a new chapter)!
Title: Re: Educational size rotational molding machine
Post by: Sabaspin on January 13, 2015, 09:00:34 PM
Incredible work Johnm!
Beautiful tops.
Many thanks for your dedication to this project.
Title: Re: Educational size rotational molding machine
Post by: Dick Stohr on January 13, 2015, 09:53:32 PM
Awesome, just WOW!!!!!!!!!!!!!!!!!!
Title: Re: Educational size rotational molding machine
Post by: cecil on January 13, 2015, 11:07:22 PM
I could see how you cleaned up all the equipment before you started the project, that you are a craftsman. I can't believe you took that big mess of plastic and created so many beautiful tops. The Tips and colors are excellent. When I cut a tip I use Mo max Cobalt with a lip. I turn the body then I cut the neck with the compound set at 45 deg. then out the door at 38 deg. My wood top I made took me about twenty hours. I'm old and slow. Also I put one hole in for the lead, my teacher taught me to use two holes, the Y balance. Now I will have three holes?
Title: Re: Educational size rotational molding machine
Post by: Neff on January 13, 2015, 11:41:25 PM
Great googly moogly those look sweet!
Title: Re: Educational size rotational molding machine
Post by: jim in paris on January 13, 2015, 11:47:09 PM
oh la la !! what an amazing display !beautiful work !
thanks very much John , and thank you again more for having let us follow the whole process step by step.


Big Up  ;--))


jim
Title: Re: Educational size rotational molding machine
Post by: Eric on January 14, 2015, 12:55:06 PM
Amazing work (and pictures) John!!!
Title: Re: Educational size rotational molding machine
Post by: JNeff on January 14, 2015, 01:43:08 PM
Terrific job John. We definitely put the molding machine in the right hands.
Title: Re: Educational size rotational molding machine
Post by: johnm on January 14, 2015, 07:58:49 PM
Some general numbers for these tops with tips installed.
nominal overall height is about 6.3 inches (160 mm)
nominal maximum diameter is about 4.7 inches (120 mm)
average weight is about 313 grams (0.7 lbs) but extends over the range from 272 grams to 353 grams which is a variation due to how much material I packed into the mold.  The earlier tops are lighter.

I've finally cut one top in half to see the distribution of material inside.  The balance on this one was quite playable but there was a significant vibrations and a noticeable visual wobble.  I marked the "high" side of the wobble while spinning with a sharpie and made the cut across that spot to the opposite side.  One side is noticeably thicker than the other and a clear lack of symmetry is seen where the tip would be installed.  I suspect that for this example the collection of extra material all on one side is coincidence and that on others the distribution might be more randomly spread around.
The inside surface is fairly smooth but there are some small shallow voids (hard to see in the picture).  The material exposed in the cross section is well merged and should provide a durable top.

(http://farm8.staticflickr.com/7471/15660203454_b58d323294_c.jpg)

(http://farm8.staticflickr.com/7468/16095261440_baf43908ed_c.jpg)
Title: Re: Educational size rotational molding machine
Post by: Kirk on January 14, 2015, 08:31:01 PM
John,
They look superb.
By the way what size threads are you using for the tip?  We probably have some spare brass inserts that are designed for plastics floating about the office that I could send you.
Kirk
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on January 14, 2015, 10:14:37 PM
Those pictures are wild.  It is like looking at an x-ray of tops!  Very fascinating.

I shared this thread with an adult in our youth program to show him why this forum means so much to me and others.  He sat there and looked at all the pictures with mouth wide open amazement.  We are a bunch of fortunate individuals who have found each other and to work with this genius!!!
Title: Re: Educational size rotational molding machine
Post by: Kirk on January 15, 2015, 12:31:05 AM
I have just been informed that I will not be throwing one of these in the kitchen.  :)
Title: Re: Educational size rotational molding machine
Post by: Shootist on January 15, 2015, 12:43:32 AM
I have been following this thread since it started. I enjoy reading the post and seeing the photos of John's amazing progress with making these Spintops.

John they are truly amazing to see.
Title: Re: Educational size rotational molding machine
Post by: cecil on January 15, 2015, 05:45:06 AM
11 OZ is very light, I like 13 OZ. If you put a tip with a half inch neck it would be a fantastic wire walker. Maybe 110 feet. I cant Waite to see one in action. I'm so happy to see big tops in the picture now. Some of my tops have a aluminum lighting rod in them, so I can pull them in with a 6-32 screw. To me it's allways easier to add weight than take it off. My son runs C.N.C lathes, and that's the way they check some of there parts. Cut them in half. I never thought I would see a big top cut in half.
Title: Re: Educational size rotational molding machine
Post by: poptop on January 21, 2015, 02:22:08 PM
The middle "group photo" is hereby nominated for the 2015 photo contest...

Such a nice bunch of good looking tops!  :D
Title: Re: Educational size rotational molding machine
Post by: ta0 on January 21, 2015, 03:11:31 PM
The middle "group photo" is hereby nominated for the 2015 photo contest...

Such a nice bunch of good looking tops!  :D

Mm, I prefer the first "honeycomb" group photo for the contest.
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on January 22, 2015, 08:08:23 PM
wow!  Wow!!  WOW!!!

I just spent three hours at the University of Cincinnati with the one, the only johnm.  My head is spinning with all I saw and heard.....and I have been there several times before!  Don has to be so happy with what he has done with the rotational molding machine.  I picked up lots of HDPE tips, lots of turning tips and lots of new items for the hall of fame.  What a day.  What a good friend!!!

Thanks for all your extra time and loving care with those tops.  I still cannot believe all the work and effort they took.  They look beautiful.  I cannot wait to throw mine.
Title: Re: Educational size rotational molding machine
Post by: jim in paris on January 23, 2015, 01:51:05 PM
good news , Mike
UC is on my list for the ultimate spin trip


jim
Title: Re: Educational size rotational molding machine
Post by: Dick Stohr on January 24, 2015, 04:16:58 PM
JOHN!!!!!!!!!!!!!!!!!  #15 & 17 arrived today in terrific condition. Throws well, boomerangs well, but as expected in the hand they wobble like a dogs hind leg on crack. Do not remember where I heard that expression but I have been waiting a long time to use it. When we find the balancing process (Neff?) these will be amazing. No Cecil, there will be NO battling with these, they are too pretty. Only for play over carpet. John thanks again!
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on January 24, 2015, 05:03:18 PM
Thanks for posting about this, Dick.  I wanted to hear someone else talk about these before I did.  I got #3 and #20.  I did not look at colors, I just asked for the heaviest ones left.  Personally, I was stunned.  I can do a lot more with these than the original first batch, which were pretty light.  Don't get me wrong, I had so so so much fun with the original one that Mark Hayward had back almost 20 years ago at a juggling festival in Cincinnati.  When I finally got that one to boomerang I was so thrilled and excited.  How nice to revisit this style and size with a different material.

I am anxious to hear everyone else's comments!
Title: Re: Educational size rotational molding machine
Post by: Larry D. on January 24, 2015, 05:12:52 PM
My tops arrived today also…they are beautiful!
Thanks John for all the long hours and hard work you put into making these gorgeous tops!
Title: Re: Educational size rotational molding machine
Post by: cecil on January 28, 2015, 12:06:51 AM
If I can save a Koma, top I'm sure I could make one of these tops do a double body corkscrew? I hope all of these tops are enjoyed. Will some one make a video and show off one of these beautifully tops?
Title: Re: Educational size rotational molding machine
Post by: Kirk on January 28, 2015, 12:41:33 AM
Still Photos here Cecil.   http://www.ta0.com/forum/index.php/topic,3727.0.html   Sorry no video yet.
Title: Re: Educational size rotational molding machine
Post by: Eric on January 28, 2015, 12:12:34 PM
I got mine and they are wonderful!!!  John did a truly spectacular job on this project!
Title: Re: Educational size rotational molding machine
Post by: ta0 on January 28, 2015, 12:44:29 PM
I got mine yesterday and could play a little bit this morning.
What nice looking tops! They look like marble sculptures!  8)
The little swirls also remind me of pictures (with a filter) of the hot sun surface.

One thing that surprised me is how hard they feel, kind like glass. And when they land on the side and specially on the tip on a thin carpet over a hard surface the sound is high pitch: I instinctively fear they may shatter (but I don't think they will).

And they also play well. They do have some wobbling in the air, but very little on the hand and more importantly they feel good on the string (cord). I got a light one and a heavy one to compare them. I thought the light one might be too light but no, it had enough weight (although the weigh distribution on these tops is a little to top-heavy).

These are wonderful tops to display and play!

THANKS JOHN!
Title: Re: Educational size rotational molding machine
Post by: mailman on January 28, 2015, 07:12:09 PM
I'm so glad everyone is receiving their new tops!  I know that you are all those who financially supported the relocation of the molding machine, and it is only right that you all get to receive tops first.

My question is....will there come a time when others can purchase one of these?  I might be interested, and I know a friend of mine would be, too....
Title: Re: Educational size rotational molding machine
Post by: ta0 on January 29, 2015, 08:00:01 PM
I had a chance to play a little more with my tops today:

(http://ta0.com/Button-n-String/rotomold-pair.jpg)

The wobbling in the air is actually less than what I first thought. It comes back from the boomerang spinning nicely. What mislead me is that when roller coasting the top at low speed it tends to wobble a lot. My guess is that it happens because of the weight distribution far from the tip where the force is applied.
Title: Re: Educational size rotational molding machine
Post by: johnm on January 29, 2015, 08:30:50 PM
My question is....will there come a time when others can purchase one of these?  I might be interested, and I know a friend of mine would be, too....

It is likely but not guaranteed that a selection of HDPE rotomolded tops will be on offer in person at the 2015 Whirled Festival of Tops in Miamisburg, Ohio in late August. :)
Title: Re: Educational size rotational molding machine
Post by: Kirk on January 29, 2015, 10:58:47 PM
I have August 22, 2015 marked on My calendar!
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on January 30, 2015, 07:13:50 AM
Yippee!!!  How exciting to see the party already developing.  Last year the party included a birthday cake and celebration for JNeff.  Wonder what the will happen this year?  I am guessing some smiling faces as people spin their ESRMMHDPET (Educational Size Rotational Molding Machine HDPE Tops)!.
Title: Re: Educational size rotational molding machine
Post by: Kirk on January 30, 2015, 08:32:40 AM
ESRMMHDPET (Educational Size Rotational Molding Machine HDPE Tops)!.
Every top we own has a name Cobra, Sidewinder, Trompo Grande, Chico 2, Watts, Jupiter ....  Now the heretofore unnamed top has an easy to remember, easy to pronounce name!  :)
Title: Re: Educational size rotational molding machine
Post by: Eric on January 30, 2015, 12:26:02 PM
Why not name them Rototops?
Title: Re: Educational size rotational molding machine
Post by: Larry D. on January 30, 2015, 12:45:23 PM
Good name Eric.  I'll second that.
Title: Re: Educational size rotational molding machine
Post by: ta0 on January 30, 2015, 01:37:56 PM
Why not name them Rototops?
Good name Eric.  I'll second that.

It is such a good name that it has been used before. 

The Roto Top (http://www.ta0.com/forum/index.php/topic,2472.msg25291.html#msg25291):

(http://www.ta0.com/forum/index.php?action=dlattach;topic=2472.0;attach=849;image)

or the Ro-To-Top (http://www.ta0.com/forum/index.php/topic,2896.msg29650.html#msg29650):

(http://www.ta0.com/forum/index.php?action=dlattach;topic=2896.0;attach=1054;image)

Title: Re: Educational size rotational molding machine
Post by: Ludo on January 30, 2015, 04:28:28 PM
TOPS ARRIVED BEAUTIFUL FINISH
EASY BOOMERANG BUT ROPE SHORT
THANX AGAIN JOHN

JIM LUDO
Title: Re: Educational size rotational molding machine
Post by: silvertop on January 31, 2015, 09:13:05 AM
Got mine!  #10 - spun every time so far.  My old hands would like it a bit less slippery, but it sure is pretty!  Definitely a carpet only spinner!  Many kudos and thanks to John for his work, and I am so pleased that my old machine is getting a new life, and that everyone is pleased with the group's investment!
Title: Re: Educational size rotational molding machine
Post by: Kirk on January 31, 2015, 06:37:29 PM
ESRMMHDPET (Educational Size Rotational Molding Machine HDPE Tops)!.
Why not name them Rototops?
Rototop, ESRMMHDPET....  Rototop, ESRMMHDPET....  Rototop, ESRMMHDPET....  Hmmm.
After much deliberation Eric's name seems just a bit easier to pronounce.

Thus, Rototop it shall be.
Title: Re: Educational size rotational molding machine
Post by: johnm on February 05, 2015, 07:52:52 PM
I’m happy and relieved to report that the final top from this adventure was received by its owner today.  :)

I’d like to thank all the original donors for participating.  A special thanks to Don for all he has done to keep tops available through the years and for offering the rotomolding system to the forum before Craig’s list.  Also a special thanks to ta0 for all he has done for top spinning and in particular, directing and handling a lot of the details to complete this project.

Here are individual pictures of the tops that now have new homes.

(http://farm8.staticflickr.com/7480/16302303842_b322e71abc_h.jpg)
(http://farm8.staticflickr.com/7477/16303163385_db146d0197_h.jpg)(http://farm9.staticflickr.com/8584/16277237796_a7c5d52c7a_h.jpg)
(http://farm9.staticflickr.com/8594/16302303742_c5c1c0a722_h.jpg)
(http://farm8.staticflickr.com/7471/16301380231_8b9d0546d6_h.jpg)(http://farm8.staticflickr.com/7533/16117023909_95b2f8702f_h.jpg)

EDIT: added the missing link for #13-#16 per observations in follow up posts
Title: Re: Educational size rotational molding machine
Post by: Sabaspin on February 05, 2015, 08:30:06 PM
Yes! As JohnM said I got mine today.
Spent the late afternoon playing and I really love the top and the tip that was made for them.
Thanks again Johnm and all who helped make the project possible, for  this gift to the top community.
Title: Re: Educational size rotational molding machine
Post by: Jack on February 06, 2015, 04:11:12 AM
Yes! As JohnM said I got mine today.
Spent the late afternoon playing and I really love the top and the tip that was made for them.
Thanks again Johnm and all who helped make the project possible, for  this gift to the top community.

i lold  ;D
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on February 06, 2015, 11:39:56 AM
Congratulations johnm for all your fantastic and quick work.  You did not need to rush through this process as quickly as you did, but many many thanks for all the excitement you brought to this forum.  It is fun to watch people's reactions to their tops and to watch the creativity that is spurred on by these roto tops.  I look forward to hearing more from everyone.

I am also quite impressed with the picture of your 19 beauties!
Title: Re: Educational size rotational molding machine
Post by: Neff on February 10, 2015, 09:59:06 PM
I can't help but notice 13, 14, 15 and 16 are missing in the collage?
Title: Re: Educational size rotational molding machine
Post by: jim in paris on February 10, 2015, 11:28:54 PM
# 13 Right
was on this table next to
 # 5 Left

jim
Title: Re: Educational size rotational molding machine
Post by: cecil on July 25, 2019, 09:38:00 PM
I’ve waited a long time to see one of these tops do the basic tricks. Can any one make a video showing wire walkers, stairway to heaven, cork screw, and Texas cowboy? John, did such a beautiful job on these - It would hurt to see these turn into duct bowls - like the wood turners make. The two videos made are fantastic, I just would like to see more PLEASE.


Ericks Roto spin top https://youtu.be/xz7Ti9mh6Wc
Tao roto top https://youtu.be/8DZu6MWHIUw
Title: Re: Educational size rotational molding machine
Post by: ta0 on July 26, 2019, 01:34:23 PM
Thanks Cecil for reposting these videos: I had forgotten about them!

The roto-molded top project was great, thanks to John's technical knowledge and commitment.
He might still have a couple of those unique tops left.

I have wondered if a rubber roto-molded top would be possible . . . :-\  Recycled tennis shoes soles?  ;D
Title: Re: Educational size rotational molding machine
Post by: jmadrigal on July 26, 2019, 04:32:05 PM
I have wondered if I could print a top out of a soft material. They have ninja flex. I wonder if it would deform while spinning🤔
Title: Re: Educational size rotational molding machine
Post by: cecil on July 26, 2019, 07:34:38 PM
If they do the basic tricks - I would like to buy one. Cork screw - stair way to heaven - wire walkers - and Texas Cowboy. I have been telling all these bowl makers on you tube to make a big nice top. If I can make a couple of flower pots - they can make some tops? I like the way I can make friends every where?
Title: Re: Educational size rotational molding machine
Post by: ta0 on July 26, 2019, 07:36:54 PM
I have wondered if I could print a top out of a soft material. They have ninja flex. I wonder if it would deform while spinning🤔
I have a couple of different flex materials but have not been able to optimize the 3D printing yet. I upgraded the extruder to the latest version to do this, but I still have to work on it. Right now I can print very nice flexible mats  ::)
Diabolos have soft shells but, of course, spin much slower.
My guess is that the top would work.  Centripetal force would tend to keep it round. The concern would be that it develops some vibration/flex modes.
Title: Re: Educational size rotational molding machine
Post by: jmadrigal on July 27, 2019, 07:30:38 AM
Possibly some internal cross bracing would be needed to prevent deformation during the spin?
Title: Re: Educational size rotational molding machine
Post by: Jeremy McCreary on July 29, 2019, 02:50:43 AM
I have wondered if I could print a top out of a soft material. They have ninja flex. I wonder if it would deform while spinning🤔

My guess is that the top would work.  Centripetal force would tend to keep it round. The concern would be that it develops some vibration/flex modes.

Some of my LEGO tops have more flexible structures than others. When these deform under the abrupt acceleration of spin-up, they can "ring" for some time after release. Especially susceptible to these vibrations are tops carrying much of their mass in spokes with outer ends free to flap and twist.

By structure and material stiffness, metal, hard plastic, and wooden throwing tops are generally much more rigid than my tops. But I can see a hard landing or a jerk of the string exciting lasting vibrations in a throwing top of softer materials.

LEGO precision molding guarantees static balance when all parts are fully seated in a symmetrical arrangement. In addition, tops with parts designed to move under centrifugal force usually self-balance quite nicely. (Might also be true of a flexible throwing top.)

So most of my wobbles end up coming from excited vibrations. Gentle spin-ups can help, but the only real cure is to change the mass distribution or structural stiffness or damping to shift mode resonances away from operating speeds. Problem is, that may not be possible when you're going for a certain look or behavior.
Title: Re: Educational size rotational molding machine
Post by: Jeremy McCreary on July 29, 2019, 03:13:49 AM
I have wondered if a rubber roto-molded top would be possible . . .

Some of my LEGO top rotors are based on wheels. And I sometimes fit them with rubber tires to increase AMI. (The rubber is a good bit denser than the ABS plastic.)

Problem is, tops like this don't recover from scrapes. The rotor grabs the ground or the hand instead of bouncing/slipping, and the spin comes to an abrupt halt.

May be more of an issue in finger tops, but it might come up when correcting a throwing top. String coming in contact with the body might also grab on instead of sliding smoothly toward the notch in the tip.

Still, if anyone could overcome these challenges, it would be you.
Title: Re: Educational size rotational molding machine
Post by: the Earl of Whirl on November 24, 2020, 10:02:29 PM
Here is a blast from the past.  I did not realize it has been six years since we started working on this and helping Don get started on downsizing.  It is very interesting to reread how it all went down.  I forgot a lot of it.

I bring this up because I now have a few more of these large plastic tops that Don originally made with the rotomolder.  It makes me laugh to see them all in a row!!!