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Author Topic: Giant Top 2014 Full Test  (Read 23994 times)

JMauk

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Re: Giant Top 2014 Full Test
« Reply #60 on: September 20, 2014, 02:34:19 AM »

Latest idea: no budget for it at present, these things are expensive, might be able to make them ourselves, but how about four wind machines focused on the four "corners" of the perimeter to blow in a counter-clockwise direction?  I see from net search that some 25 hp models can hit 50 mph winds. ($3,000 each) or monster movie effects versions can hit 80 mph ($13,000).  Easier than a bell jar!
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Kirk

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Re: Giant Top 2014 Full Test
« Reply #61 on: September 20, 2014, 08:42:30 AM »

I had joked to myself about 30 guys standing around with leaf blowers :)
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JMauk

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Re: Giant Top 2014 Full Test
« Reply #62 on: September 23, 2014, 11:25:20 PM »

Posting a pic of the new paint job on Bumblebee to suit his different orientation on the cart as compared to the old tower drop.  Will post video of today's repeat of full-load test when YouTube is finished uploading. Some interesting things I will talk about then.
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JMauk

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Re: Giant Top 2014 Full Test
« Reply #63 on: September 24, 2014, 12:50:02 AM »

Second test of full weight spin for biggest top in the world. This morning. Faster but discovered a few more things we need to work on.

http://youtu.be/gI9MP4BZhrg

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JMauk

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Re: Giant Top 2014 Full Test
« Reply #64 on: September 24, 2014, 01:10:03 AM »

Bumblebee's Roll Down

http://youtu.be/4PlnV41eL-A

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JMauk

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Re: Giant Top 2014 Full Test
« Reply #65 on: September 24, 2014, 02:39:35 AM »

Another view Sept 24,2014 test

http://youtu.be/rwhXdXaPYZA


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JMauk

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Re: Giant Top 2014 Full Test
« Reply #66 on: September 24, 2014, 08:10:03 AM »

Okay, evening and I will try to give a better report on this morning's test.  It appeared to us that we achieved higher rpm than first full load test.  We did a little extra lubrication on the pulleys but other than that we had everything the same as first attempt. We thought Bumblebee pulled a little better and it went further up the end ramp, didn't hit the crash bunker but rolled back slowly to start position.
We had sand bags available if we decided we wanted to try more weight, which is why the video of Bumblebee shows a tarp in position to receive the sand bags if decided.  We decided we got increased rpm's without more weight so wanted to analyze everything first before trying anything else.

I was pleased we repeated everything as in first test because we had some damage to the inner plywood disk of the spool and so we know it was not due to increased weight but the existing weight of Bumblebee.  The reason the sheath at the end of the rope got stuck in the spool is that the plywood disk inside started to disintegrate.  We are going to remove it all and replace it with thick rope base wound tight around to same diameter as destroyed disk. The top rope will then wind on top of this base.  Or, we could wrap directly to shaft but would need a rope length adjustment or would not wind out to the full 24" diameter preferred pulling start.

Also, on the incredibly strong blue synthetic rope/cable we noticed some tiny spots of melting, like frayed end strands being burned off, we assume from the heat involved in the friction passing through the pulley.  It seems to have only been like split ends not the main strands themselves and very small, but interesting!

We didn't time out the full spin but I don't think it would have made 15 minutes.  There was probably additional slowing cause by the sheath flapping around from the spool.  The jumping around of the end of the shaft on the steel plate was tremendous.  There was significant scoring caused by this on the plate and apparent flattening of the point at the same time.  I think we will need to fabricate a hardened steel point to attach to the shaft to prevent this type of wear. Probably will need a hardened steel plate as well.  I may work on this along with the shortening of the length of the bottom shaft.  I feel it will give more stability and better appearance.  Of course what we don't know, especially after what happened today with the center plywood disk, if too many spins will cause the whole top to start disintegrating!  Oh well, if so, we will have fun while it lasts!
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ta0

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Re: Giant Top 2014 Full Test
« Reply #67 on: September 24, 2014, 11:24:32 AM »

Good second test. I am glad that you tried the same weight as the spool was about to fail.

I will analyze more the videos later, but I can tell you got about the same revolutions as before: 193 RPMs with a margin of error of not more than 2 RPMs.

The good news is that the spool is the easiest part to modify and may have the biggest impact. A low friction material would be a good choice. I need to think about the core size.

This time it looked to me that it was really free spinning. An added advantage of shortening the tip is that it will lower the center of mass and the critical spin for free spinning will also decrease.

It was great that you had two cameras on the top and one on the bumblebee (nice paint job!) More later, when I have time to look some more at the videos.

I am fascinated by this project!
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ta0

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Re: Giant Top 2014 Full Test
« Reply #68 on: September 24, 2014, 07:47:00 PM »

Quote
We are going to remove it all and replace it with thick rope base wound tight around to same diameter as destroyed disk. The top rope will then wind on top of this base.  Or, we could wrap directly to shaft but would need a rope length adjustment or would not wind out to the full 24" diameter preferred pulling start.

I suspect using a coil of tightly wound rope to replace the core may not be stable under revolving tension, but I may be wrong.
Wrapping the pulling rope directly on the shaft gives you the maximum theoretical conversion but also high deceleration at the end and therefore larger stress. On the other hand, I don't see a problem with decreasing a little the 24" start diameter, except for a proportional increase of the sidewise force on the bearings at the start.

I am thinking I will give it a try to simulate your system in a computer, including the drag.
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JMauk

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Re: Giant Top 2014 Full Test
« Reply #69 on: September 24, 2014, 09:43:40 PM »

Pic of the rope replacement center.  No testing yet.  Just seeing what it looks like.
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JMauk

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Re: Giant Top 2014 Full Test
« Reply #70 on: October 03, 2014, 09:35:51 PM »

Hi friends,
In three hours a crew from a national television network (ABS-CBN) will be here to shoot a segment for a science show.  The host is a long-time acquaintance and he has requested a public spin of the giant top. So, hard to refuse such a request, we will give it a try.  Have the temporary rope-wind core in place to replace the original plywood of the inner spool.  Will be a good test of that idea!  Don't know how much video I will be able to get of it with everything else going on but will post what I can.  I hope also a link will be available for the show segment after production.  Appreciate prayer from those so inclined and positive vibes from those not so inclined!
Joe
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ta0

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Re: Giant Top 2014 Full Test
« Reply #71 on: October 03, 2014, 10:23:26 PM »

Good luck! 

A lower load may be a good idea . . .

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JMauk

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Re: Giant Top 2014 Full Test
« Reply #72 on: October 03, 2014, 10:45:09 PM »

A lower load may be a good idea . . .

Yes but Bumblebee is already on the cart and can't get him off without a crane truck, which is not on site!  Yes good luck may be the order of the day!
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JMauk

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Re: Giant Top 2014 Full Test
« Reply #73 on: October 04, 2014, 04:57:41 AM »

All went well. Thankful.  Will post some stuff when I can get it organized.
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czyoyo

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Re: Giant Top 2014 Full Test
« Reply #74 on: October 04, 2014, 05:19:25 AM »

All went well. Thankful.  Will post some stuff when I can get it organized.

[Exhaling...]
That's great! ;)
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