Let's Make Robots!

Ball bearing motor


(Update II: New video, we managed to make it run on a standard racing pack 7.2V (no clue to how many amps - but not enough to kill a large elephant, only enough to melt wires slowly))


(Update: A SlowMo edit of the video, especially for "mogul" - that's lack of intelligence for you, frame by frame :D)

 


Original post:

 

A ball bearing motor needs a lot of amps.

We knew that.

We estimated that this one would do well with 10-15 amps.. But the LiPo battery I had around was a 6600 40C (Estimated 264 amps in the burst).. which turned steel into flying plasma.. a little faster than expected.

Note how close I am to severe burns - the table, floor etc got badly burnt - sometimes I am just lucky :)

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birdmun's picture

It would seem current control would be a good thing. Maybe these motors have similar characteristics to steppers, in that they only deal with a constant current, but, can handle many multiples of their stated voltage? For instance, steppers for hobby CNC machine usage are often times run at 10x and sometimes up to 15x their stated voltage, but, the current is judiciously controlled by the driver.

fritsl's picture

This is not a motor in the normal understanding. There's just two ball bearings, common axle, and a short circuit. No magnets, no detected magnet field other than from the wire, no coils. Just a short circuit on wheels. And that short circuit needs to be heavy on amp. It can run either way, but needs a high speed to get started accelerating. 

guillermobarbadillo's picture

Nice Video :)

lumi's picture

@SkeptiKal: Yep, that would be a definition :-)

@Bajdi: well, as you can see, Frits used the metal axle as a fuse to protect the LiPo :-) So the PiPo was never in danger to catch fire

SkeptiKal's picture

Just love the reactions!

I'm sure this could be linked to lumi's & MarkusB's discussion on oddbots Robot A.I. blog regarding attraction and curiousity ;-)

fritsl's picture

"Does a piece bounce off your leg?" That's what we thought when looking as well.

But we only found a small piece of metal on the table - smaller than it appears on the video, very light. And nothing else, puff!

Bajdi's picture

You're mad shorting a Lipo. You run the risk the battery catches fire, and I don't want to be around when that happens. But I love to see videos of other people fooling around with them :)

Maxhirez's picture
The look on your face in the photo is priceless! It has recognition of danger, wonder, excitement and determination, but it's all still somehow under the umbrella of curiosity! I'm glad your home is still standing!
fritsl's picture

I tell you: we shot it in 60fps (youtube is less than 25, I guess) - on my computer it's a fantastic study into human reactions,when eyes are blinking, and when disbelief is changing to marvel and fun. Amazingly,the reaction of laughter appears in a split second, even while the situation is under development and eyes are blinking. I thought one needed more than perhaps 3/60 second to see the fun factor in a situation.

mogul's picture

Any chance that you would pick a few of the cool frames and post them here along with their relative time stamp.

The study into our reaction on amazing "incidents", which we all experience once in a while, could be interesting.  Why do we shoot videos of our contraptions if the real fun is watching our faces while the action is going on?