Author Topic: Prevent Weapon shaft from spinning when running drum?  (Read 1642 times)

iidrushii

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Prevent Weapon shaft from spinning when running drum?
« on: September 23, 2016, 05:46:18 pm »
Hi Friends,

Not sure what info exactly you need to help with this issue, but I'll try my best.

I've got a Weta 2 Kitbot. Like an idiot I took the drum off to explore and see how it was working a little better. Pete runs the Weta 2's drum as an inrunner. Since then the weapon shaft slowly spins and is also gradually pushed to one side every time the weapon is switched on. The shaft is 6/16th diameter and 6 1/2 - 7" in length (I think). The drum has 2 needle roller bearings on each end. The weapon shaft is held in place through the UHMW Chassis and locked in with some metal wiring at the end of the shaft. Basically it seems like the weapon shaft can't grip the UHMW very well and I fear I am losing some valuable KE.

It's worth noting that when I put the drum back together, I ended up with 2 extra nylon washers and didn't know where they were supposed to go. On the non-motor side of the drum, there are 2 nylon washers and a smaller metal washer. There is also a bit of extra space...if the extra 2 washers did in fact go there, would that help prevent the shaft from moving?

Jeff Gier

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Re: Prevent Weapon shaft from spinning when running drum?
« Reply #1 on: September 23, 2016, 06:04:29 pm »
Don't own a weta, but have built something similar:

Those washers are probably supposed to go between the stator (motor coils) and the drum.  this keeps the drum from rubbing directly on the motor coils.  You may have to take off a side plate to get this to fit together properly.

You could probably just use a bit of tape on the ends of the shaft.  The shaft moving a bit isn't really a problem. 

PS:  The type of motor used in the drum is called a "brushless outrunner".  The setup that the new weta has is often called a direct drive or a motor-in-drum setup by robot people. 

PPS:  The "metal wiring" that holds the shafts on are called cotter pins.
« Last Edit: September 23, 2016, 06:06:19 pm by Jeff Gier »

iidrushii

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Re: Prevent Weapon shaft from spinning when running drum?
« Reply #2 on: September 23, 2016, 06:15:28 pm »
Thanks for the terminology clarification! I had a feeling I used a word or 2 incorrectly.

I'll try to use some tape. should at the very least keep it from being pushed to one side.

rcjunky

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Re: Prevent Weapon shaft from spinning when running drum?
« Reply #3 on: September 25, 2016, 03:35:46 pm »
the weapon shaft is just kinda floating and nothing to worry about, gluing it or taping it to be stationary won't help anything.
Andrew Burghgraef
Canadian Carnage Robotics