Re: Modular Drive System
 

Since we’re designing around the Andy Mark (AM) 8” Mecanum wheel, I’m going look closely at the assembly of the delivered kit.

1. I know there are issues with binding in the rollers if extra work isn’t done to prep the parts. I’ve looked at the video provided by AM: AM Video
   
   I found the all middle rollers very sticky. This was not metal-to-metal interference but plastic or rubber to the brass shaft. I tried the AM video method but had no luck and don’t understand what it’s supposed to do.
   
   I tried an 0.251” reamer to get a better fit (roller ID is ~ 0.0252”). This did not act as expected: once through with gentle rotation would reduce interference. What I found was rubber or adhesive like particles (no metal) on the reamer flutes (see photo below).
   
   
   
   Here's an AM drawing of middle roller with my mark-ups of dimensions I measured (approx. avg.):
   
   
   
   The metal bushing's ID is about 1 to 2 thousandths over the brass axle 0.250". The axles I measured have pretty good tolerances; eccentricity within about 0.0005". I don't think the binding I've found is a result of metal interference tolerances but from Polycarbonate
   Core molding operation. I used a 3/16" reamer, inserted up to the far bushing and scraped between bushings. This method combined with reaming bushings with 0.251 reamer, resulted in a fit where the axle would fall through with no force.
   
   
2. I want to reduce the play in the middle roller and make the outer rollers spin better. See video:
   
   
   

More to follow...

Re: Modular Drive System
 

Re: Modular Drive System
 

Is this designed for there to be a hopper or other structure in the open space connecting the two sides? If not, I'd recommend adding crossbars there as well for added support.

But looks good otherwise

Re: Modular Drive System
 

Trying to use the space on the side and rear perimeter for electronics. The front is left open for game systems. The forward structure will be determined later by geometry of game systems. The wheel wells/gearboxes form the structural base for the box trusses on sides and rear ( truss bracing using 1/4" Al rod not drawn yet).

Re: Modular Drive System
 

Changed gearbox to protect encoder

Previous:



Current:

Re: Modular Drive System
 

Received the Matex planetary gear set:



Am ready to machine housing:

Re: Modular Drive System
 

Re: Modular Drive System
 

Oh boy! This year's game is very interesting regarding drive design. We're still scratching our heads over game play strategy. At first read of the rules, I thought this was going to be a heavy contact Hockey game where chassis strength would be essential. I had images of robots checking each other, pushing and shoving to get/deny the ball.

Our Regulatory Affairs Officer ;) says there will be almost no defense, but I'm still optimistic...

From our initial brain-storming, it looks like a ground level opening in the front could be a real asset. I also think a low clearance/CoG has very desirable. If they didn't cost so much, I'd switch from the 8" Mecanums (already purchased) with 6" size.

Our drive team are leaning toward using the AM KOP drive chassis with regular wheels. I'm trying to steer them away from 4-wheel tank drive because of ugly turning and pivoting performance. But, I'll continue working on the modular setup as a design exercise.