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[johnm]

I would love to see a photo of one of your final melted blocks if you should turn another.  Do you think it would be possible,  or helpful even,  to pound the melted plastic mass as one might do to cake mix to prevent air bubbles/voids or is the plastic not liquid enough?

Here's a pic with a container full of raw material chunks which gets melted and additional chunks added several (maybe 6) times next to a cooled 'fully' combined block of HDPE plastic in a similar container.  You can see the surface is continuous and smooth but not a nice uniform shape.  The shrinkage is reasonably visible.  The inner diameter of the container is about 4 inches and while at temperature (360 F) the material fully fills the diameter.  The shrinkage is so nonuniform around the circumference of the resulting cylinder that after cleaning up the outer diameter, I get a suitably round turning blank to make a top of 3 inches diameter, which is the nominal size of the white top in the size comparison picture posted earlier.


Not going to high enough temperature will probably result in a very skeletal block unless some real pressure/compressing force is used.  Here's my very first test of the mold with milk jug plastic.  Of course I underloaded the base form (due to fear of terrible adhesion) but regardless, the material didn't flow together under gravity and it really didn't mash together very well when the inner part of the mold was pressed in.


Pounding may do something, but it probably will be rather difficult.  Even when hot, the material is very 'stiff' and when removed from the heat, the surface quickly cools and solidifies thus making it hard to work.  On the top of the block you can see neat tight 'swirls' of red/white/blue which are due to my stabbing a rod into the melt several time in the hope of venting and collapsing any large voids--don't know if it worked yet, may have created more.  I think stabbing is still a good idea because it provides a test of the melt in the center.  The material melts from the outside to the inside so the surface can look very nice while the chunks in the center are barely warm and therefore still just individual chunks.  I think with a little experimenting you can not only wish for reasonable uniformity but you can expect it, but don't be disappointed when they aren't perfect.

Maybe Neff will be making his own custom discs for golf.

[hemingsoft]

Maybe Neff will be making his own custom discs for golf.

Well if that's what you're thinking, maybe we should!   

[SpinQueen]

John, thanks so much for the photos.  Very interesting and helpful.  I love the red/white/blue, awesome for a 4th of July top

[ta0]

Mike left a Cincy recycled black top (got chocolate?) on lease until I fulfill the conditions for ownership. I love the shape of this guy! That mold is perfect! The tip regens and wirewalks well (I just did staircase to heaven). If this was a commercial top it would be hot regardless of the green perspective which just adds extra coolness to it. I am impressed!

[johnm]

Mike left a Cincy recycled black top (got chocolate?) on lease until I fulfill the conditions for ownership. I love the shape of this guy! That mold is perfect! The tip regens and wirewalks well (I just did staircase to heaven). If this was a commercial top it would be hot regardless of the green perspective which just adds extra coolness to it. I am impressed!

Glad you like it.  We've had great success with them, in particular Tai-Min can now rollercoaster with ease, Aaron is really progressing on suns, and Bryan and I can quickly regen (Joker Choker mainly) to well beyond maintenance speeds to do double and Mexican wirewalkers and corkscrews.  I think part of our progress is due to a lack of fear of damaging or breaking our pressous tops since these already have some flaws from the casting process, they are tough and we can make more.

In addition to the guilt  it may give to encourage your trip to Ohio, I had an additional motive to sending one along with Mike:

In the last pic, the shape reminds of a Gates.

Perhaps you could snap a pic of them side by side for comparison.

[ta0]

Your wish is my command. Here it is:



The shape is indeed similar to a Gates and I have always been a big fan of that top. But, maybe because of the open crown, the top it reminds me when I have it in my hand is the STB.

Wow! The Cincy group is progressing fast in their playing abilities. I better go there soon or I will not be able to teach you anything!

[johnm]

Thanks ta0, nice shot.  That's a perfect angle to display some of the shrinkage problems.  In particular the profile of the cap in the mold has a circular shape which continues along the body to blend to a tangent line extending to the tip (thus the shape would be an even closer match to the Gates), but the plastic has a rather collapsed contour on the cap giving it a shape slightly reminiscent of the Mexican tops.  Less obvious are the shorter overall height, smaller maximum diameter, and slightly larger angle to the body.  Also the cap should install with a slight press fit but it actually required a single wrap of tape to compensate for contraction.
The mismatch between the top body and the steel tip is my fault.  I typically have a generic tip which I intall on each top just to test the balance to determine if that individual top 'deserves' its own tip and then make a tip to match that top (no real mass production here because the end diameter of the plastic is generally not consistent) but the initial balance of that particular top was really nice with no adjustment so I refused to pull the tip to replace it.  If/when you pull the top apart, that internal tape ring may slip off and need to be replaced.  Also you should somehow mark (on the non-black tops a Sharpie line inside works but may not show well on that one) the orientation of the cap so it can be reinstalled in that balanced position--try the cap rotated to see how bad the balance can be due to the unsymmetrical shrinkage and random voids.

If you make your own preferred style tip, the mounting hole is tapped for 10-32 thread.

[hemingsoft]

Wow! The Cincy group is progressing fast in their playing abilities. I better go there soon or I will not be able to teach you anything!

I have a feeling, call it a hunch, that I still have a lot to learn from a master spinner 

[pplgrande]

Making your own trompo, in plastic, wow now thats impressive
Very very nice............

[johnm]

and I love the matching milk cap button   

Turns out that the milk jug cap buttons have a lifetime.  Today two of them failed by cracking radially outward from the center hole allowing the knot to pull through.  Kind of a surprise to see the top fly away when you know you remembered to hold on to the string during the throw.   I may consider casting a button, that is a little thicker and hopefully more robust.

[johnm]

With Aaron the top destroyer administering the death blow, our combined efforts have finally broken one of our HDPE tops.  The ring which aligns the cap and base snapped completely off the cap.  This orange material from a bread crate seems to be a little more brittle than some of the others since when cutting it into small bits, it tends to break and blow apart at the end of the cut rather than cut all the way like most of the rest of the sources we have.  The break revealed a number of voids in the casting which probably contributed to weakness in that region.  It had survived a tremendous amount of abuse from all of us and now will hold a place of honor on the shelf.

[poptop]

I'd call that good data...sounds like those bad boys take a beating!  Did you give 'em a name besides HDPE tops?

I'm wondering if resin could be used in the mold?  Be cool to cast some like the old Duncan Mardi Gras Yo-Yo with big colorful chunks and spangles.

[ta0]

Considering all the trouble players had over the years with tops breaking, it is amazing how durable your recycled tops are. I think now there is no excuse for manufacturers not to make indestructible tops (at least fixed tip).

[johnm]

 Did you give 'em a name besides HDPE tops?

I'm wondering if resin could be used in the mold? 

I know it's not very clever but at this point I guess we're locked in on HDPE.

I'm reluctant to use other stuff in the mold for fear of adhesion and then damage to the mold during removal.  Call me a coward but for now I'm sticking (pun intended) with what works and what I know.

[poptop]

If it aint broke...