Author Topic: Making an impossible to juggle juggling club  (Read 2067 times)

0 Members and 1 Guest are viewing this topic.

Offline MrPrezidentTopic starter

  • Jr. Member
  • **
  • Posts: 8
  • Helpful? 0
Making an impossible to juggle juggling club
« on: November 29, 2014, 11:13:17 PM »
I'm trying to make a juggling club that looks like a regular juggling club, but has moving parts inside of it such that the moment of inertia changes randomly making it extremely difficult to juggle.  I was thinking that I would use some sort of linear actuator for the dowel that would move the weight back and forth between the center of the club and the end of the club.  The problem is that the linear actuator would need to small enough to fit inside of the club, strong enough to be a structural part of the club and be able to withstand dropping on the ground etc, and would also need to be fast.  Accuracy is not needed at all.  I would even be fine with pulling the weight on a spring and then letting it go or something like that.  The power source would also have to fit inside the club.

Here is an example of what the club would look like.  This club has a wooden dowel inside that runs the length of the club from top to bottom.  I would probably be replacing the wooden dowel with something that would be able to move the weight around and also replace the function of the dowel.

Offline Schlayer

  • Full Member
  • ***
  • Posts: 57
  • Helpful? 3
Re: Making an impossible to juggle juggling club
« Reply #1 on: December 02, 2014, 01:26:39 PM »
This seems like an interesting project but I think there might be a far simpler solution than building a tiny robot weight mover: Magnets. I think you can probably accomplish a fair level of random center of mass movement by replacing your wooden dowel with a smooth, metal rod, and get strong disk magnets at either end of the rod and another strong disk magnet in the middle oriented to be repelled by both of the other two. Buy magnets with holes the diameter of your rod in the center so you can slide them easily all over the rod. Viola: a super-annoying-to handle-club whose center of mass semi-randomly bounces from one end of the rod to the other.
No need to worry about any fragile electronics and complicated random movement code!

http://www.mcmaster.com/#ring-magnets/=uunre1
http://www.magnet4sale.com/112-lb-holding-power-neodymium-cup-magnet-1-57-magnetic-round-base/

Offline MrPrezidentTopic starter

  • Jr. Member
  • **
  • Posts: 8
  • Helpful? 0
Re: Making an impossible to juggle juggling club
« Reply #2 on: December 02, 2014, 05:06:35 PM »
I like the idea.  The simpler, the better.  However, I'm not sure that it would work so well.  The club spins when you throw it, so centrifugal force will push the center magnet toward the end.  I suspect that it would just hover near the end magnet the whole time.

Offline Schlayer

  • Full Member
  • ***
  • Posts: 57
  • Helpful? 3
Re: Making an impossible to juggle juggling club
« Reply #3 on: December 03, 2014, 10:00:02 AM »
That is not necessarily true. Most of the mass of the club is centered in the bulging section, and all object rotate only around their center of mass when thrown. This is why is is possible to catch an ordinary spinning club so easily-- the handle sticks out far beyond the body of the club when it is spinning in the air.



This juggling club has LEDs all over it, you can see the path the center of mass, around the blue lights, follows after it is thrown, and how the red/yellow handle lights are twirling confusingly through the air. Since the magnets are able to slide freely along the length of the bulge in the club, so long as the weight that is movable makes up, say, 50% or more of the whole weight of the club, the club will actually be rotating almost solely around the weight. The handle will be rotating around this point while oscillating back and forth due to the repelling force of the magnets.
The fact that when the club is parallel to the ground it is now impossible to tell where the handle is relative to the center of mass would make it incredibly hard to catch! You will need to do as much as possible to make sure the friction between the ring magnets and center dowel is minimized for the oscillation to continue throughout the entire throw, however.

Offline MrPrezidentTopic starter

  • Jr. Member
  • **
  • Posts: 8
  • Helpful? 0
Re: Making an impossible to juggle juggling club
« Reply #4 on: December 04, 2014, 01:34:38 PM »
Hmm... that's a good point that the position of the weight would probably influence the club more than the club would influence the position of the weight.  Now I am very confused as to what would actually happen.  I still suspect that the system might come to some sort of equilibrium, but if it doesn't that would be really cool.  It is worth a try :)

Offline MrPrezidentTopic starter

  • Jr. Member
  • **
  • Posts: 8
  • Helpful? 0
Re: Making an impossible to juggle juggling club
« Reply #5 on: December 04, 2014, 04:36:30 PM »
I'm wondering if I should get some linear ball bearings for this.

Offline Schlayer

  • Full Member
  • ***
  • Posts: 57
  • Helpful? 3
Re: Making an impossible to juggle juggling club
« Reply #6 on: December 05, 2014, 08:16:42 PM »
I am unsure what exactly the benefit of a linear bearing might be; I have a feeling that given the right sized, properly smooth dowel, or even a relatively loosely sized (as in a considerably smaller diameter than your rings' internal diameter) rod, might prove to have a very small frictional effect on a magnet. The magnet will likely be made out of something like neodymium which itself is quite smooth in my experience, and strong enough that even considerable friction tends to be negligible compared to the forces between two of such magnets. That said, it can't hurt to cover your bases by getting something which would sill leave space for a linear bearing if need be.

Offline MrPrezidentTopic starter

  • Jr. Member
  • **
  • Posts: 8
  • Helpful? 0
Re: Making an impossible to juggle juggling club
« Reply #7 on: December 11, 2014, 01:37:09 PM »
So I finally got the magnets.  These things are strong!  I had one of them on my desk and accidentally got one of the other magnets too close.  The one on my desk flew off and smashed into the one I was holding and chip a piece off of it.  Anyway, I made a prototype with some magnets, and PVC pipe, and some duct tape.  When I try to throw the thing, the center magnet ends up hovering near one of the end magnets and stays there.  I was kind of expecting that.  The whole throwing and catching process jostles the magnet a little bit, but it really wants to stay in that spot.  It seems to be especially stable while it's spinning.  I was wondering if electromagnets could force it to move around more??  Maybe that would require a lot of power though.

Offline Schlayer

  • Full Member
  • ***
  • Posts: 57
  • Helpful? 3
Re: Making an impossible to juggle juggling club
« Reply #8 on: December 13, 2014, 08:56:40 PM »
If you were to replace one of the magnets at the end of the club with an electromagnet, I think you might be able to accomplish some randomness with some clever 'pulsing' circuitry, but to equal the magnetic field strength of a neodymium magnet with an electromagnet which can be easily tossed around would be incredibly difficult, to say the least. You may want to replace both side magnets with something weaker like ceramic magnets, and if that doesn't fix the problem from there you probably could make or buy an electromagnet which equals the strength of a small ceramic magnet far more easily.

 


Get Your Ad Here

data_list