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[hemingsoft]

So more fun has been had in Cincinnati.  We finally got around to making a few tweaks to our QuickSilvers.  John had cleaned up the outsides and smoothed the ridges a bit.  Also he smoothed out the ridges on one completely.  We also had the bearing seatings cleaned up by our professional machinists so the tip is sturdier.  John also designed new tips with both fixed and bearing modes.  Here's a picture!



We also took Ta0's video of magnetic induction and made a physics demonstration about it.  Check out the setup.



We had a fun day walking around seeing if any of the professors would explain some of the oddities about the demo.  We've been thinking about possibly letting the tops float on an air table to see the full effect.

[ta0]

Wow!

Are there magnets inside the Trompo Grande with blue and green dots?

. . . if any of the professors would explain some of the oddities about the demo

Sounds like a true experiment to me . . .

By approaching a magnet to a QS spinning on my hand I had the illusion that the top and the magnet attracted each other instead of repelling each other. My explanation was that the repulsion force pushed the top to the side because of the spin and then it had to precess, therefore getting closer to the magnet.

Nice job polishing that QS!

[the Earl of Whirl]

Wow is right!  I am amazed again at what you guys are doing at UC.  It's more amazing than your undefeated football team!

[Spinningray]

Great Job! I would love to see some photos of the tips mods. Are they convertible between fixed and bearing similar to how I mod them?

[johnm]

Great Job! I would love to see some photos of the tips mods. Are they convertible between fixed and bearing similar to how I mod them?

Yes, the convertible tip "design" (as Bryan wrote) is not mine but stolen by me from Spinningray.
http://www.topspinning.com/toptalk/viewpost.php?post=9911

Thanks for all the ideas you've shared with us.

Assembly pictures will be added when I see Bryan again since he is my go-to guy for posting pix.  (I was on the clock and had to go do some real work while he posted the original--hence the lack of credit to Spinningray initially.)

One difference is that for fixed mode Spinningray's nut anchors the tip by contacting the body of the top while ours contacts the outer race of the inside bearing.  I wasn't worried about the bearings spinning in their seats since our machinist was able to make a nice press fit on the tops where the bearing initially didn't fit, and I secured the bearings in the originally oversized pockets with thick partially dried finger nail polish (easy to remove with acetone from the metal tops and not runny at all so it doesn't flow onto the balls).  Although the surface area contact with the small outer race is rather minimal, I haven't noticed any slipping problems doing RCS.  Our nuts are Delrin because I like the way a tapped hole in Delrin tends to collapse on the inner diameter giving a nice tight fit to the die cut threads (10-32).  The tips are stainless steel since the original brass tips had several problems such as the diameter match to the top body was poor, the step to contact only the inner bearing race was not long enough to avoid contact between the main part of the tip and the body of the top, and on several the 'play' portion of the tip was not concentric with the axle which created a fair amount of wobble.

I'd also like to point out the 'clean' body look was previously presented by Eric and Spinningray.  I did all the body work on a lathe with files.  Clearing all the steps was a little tedious since this aluminum alloy is extremely soft and quickly loads the files, but rounding off the sharps at the steps and at the joint between the cap and base and wiping out the tool marks is not bad and well worth the trouble.  After polishing, those first few new dings and scratches really stand out though. 

EDIT::
-----------------------
Here a picture of our quicksilver convertible tip--thanks Bryan.

[johnm]

Wow!

Are there magnets inside the Trompo Grande with blue and green dots?
Sounds like a true experiment to me . . .

By approaching a magnet to a QS spinning on my hand I had the illusion that the top and the magnet attracted each other instead of repelling each other. My explanation was that the repulsion force pushed the top to the side because of the spin and then it had to precess, therefore getting closer to the magnet.

There are eight (2 each of blue, green, yellow, purple) plastic coated rare earth magnets (1/2 inch diameter) mounted to a plastic disc which replaces the weight ring.  The magnet poles alternate to maximize the change in field with time as it rotates.  This geometry is very effective.  Just spinning either the magnet top or the aluminum top with fingers is enough to get the other spinning.  With the rip cord its very nice (our machinist squared up hole in the Quicksilver).  The colors make it very clear when that top is spinning but the Quickslivers and the 'empty' top need some decorations to make the motion more obvious.

The physics of this system seems very complicated and challenging to pick apart--I can't do it.   The faculty here seemed to ignore the details of the magnetic interaction which transfers energy from one top to another and were more concerned with Bryan's question about the apparent lack of conservation of angular momentum since if one top rotates clockwise the other will rotate counterclockwise.    We simply forgot the third top involved in the demonstration--the earth.  Hence the thought of testing it on an air table or putting the bases on pucks of dry ice to decouple from the earth--there could be sort of an orbiting effect of the tops depending on initial conditions.

I was surprised to see how unballanced these tops are when the axle is anchored.  In the hand the vibrations are minimal, I guess due to the forgiving compiance of skin.  We'll try to tune up the balance soon with sticky tak.

[ta0]

. . . were more concerned with Bryan's question about the apparent lack of conservation of angular momentum since if one top rotates clockwise the other will rotate counterclockwise. .

Yeah, that would be a true stumping question to give the students!  The reaction force at the tips is not obvious and I was puzzled the first time I encountered the "problem".

Your setup reminds me the "Magnetron" from Andrews Mfg. It shows periodic exchange of energy back and forth between the wheels. Do you see that with the tops?

What is the purpose of the empty Trompo?

[johnm]

Your setup reminds me the "Magnetron" from Andrews Mfg. It shows periodic exchange of energy back and forth between the wheels. Do you see that with the tops?

Nice toy!
No this effect is not apparent in our setup.  My first guess is this doesn't happen because the aluminum top has no fixed poles and therefore there are no distinct equilibrium orientations for the rest state.  We can spin an aluminum top with the rip cord to initiate opposite rotation in the magnet top which in turn (pun intended ) initiates rotation of the second aluminum top with the same direction as the first aluminum top.  Giving the magnet top an initial rotation to match the direction of the aluminum top displays the independence on initial conditions for the direction as the magnet top will slow, stop and reverse directions to be opposite the aluminum top.

What is the purpose of the empty Trompo?

The empty top is to show that the magnets need to be there.  There is no response when that top is used.  There seems to be a misconception about the roll of gravity between the two tops so the situation of the empty top and the aluminum top is available.

[jim in paris]

john ! you're a poet !

jim

[ta0]

I agree John, I wouldn't expect it as the induction is instantaneous (compared to the rotational speed) and there cannot be a phase shift.

The Magnetron is fun to watch. I generally start one rotor at high speed and the other one at slow speed with the opposite spin (same tangential direction.) That maximizes the number of oscillations.

[hemingsoft]

Thanks John for the picture of our tip in your edit.  Apparently edits don't bump.

[SpinQueen]

I love how many nerds we have on this forum 

Good stuff!

[hemingsoft]

I love how many nerds we have on this forum 

We experimentists in the department always joke that the theorists were those who weren't good enough to be experiementalists.  Well, in this case we are "top theorists"  who are not good enough at spinning tops! 

[the Earl of Whirl]

This is very late but I have a break in my schedule and I see where the weather is supposed to be nice tomorrow (Tuesday the 20th).  Do any of you Cincy guys think might have some time in the morning to throw?  I could be there from 10-noon if you have any time. 

Thanks for your consideration on such short notice.

[John Buechele]

Hey Mike I'm in town. I might be interested in going down tomorrow. Let me know what you find out.

[johnm]

This is very late but I have a break in my schedule and I see where the weather is supposed to be nice tomorrow (Tuesday the 20th).  Do any of you Cincy guys think might have some time in the morning to throw?  I could be there from 10-noon if you have any time. 

Thanks for your consideration on such short notice.

Hi Mike and John,
The big tops are always available for a throw, I on the other hand have to provide some equipment training to a faculty member from around 9:00 to 2:00 but maybe could sneak away for about a half an hour depending on when things time out (there's an interval while we wait for the system to achieve a high vacuum level.)  I don't know what the other guys have scheduled but you could always stop by Bryan and Tai-Min's lab to grab some tops. 

I'll send the guys an email to check the board, but no guarantee that they'll be checking.

[the Earl of Whirl]

Thanks johnm!


I had an opportunity to throw one of those quicksilvers.  Wow, it is really nice.  And it is exciting to see everyone at UC make great progress with them!!!