30-08-2009 20:41

Jared Russell

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

I'm curious if you've had a chance to test these out. I'd be worried about side loads on the wheel modules (for example, when turning rapidly at full speed).

30-08-2009 23:00

sdcantrell56

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

I don't see any method for tensioning the chain either. WHat do you have planned for that?

30-08-2009 23:26

AdamHeard

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

With shorter chain runs and decent manufacturing tolerances you can do exact Center to center distances. Both 118's and our crab modules work this way I believe.

30-08-2009 23:33

EricH

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

330 does this in 6WD skid steer... And then puts a tensioner in to make sure.

31-08-2009 03:08

Cory

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

If you need a tensioner, then it doesn't actually work, right?

31-08-2009 03:17

EricH

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

Actually, it does... The tensioner is usually an encoder's sprocket. The only way to tension the chain is to move the encoder...

Also, remember that the chain can stretch slightly if it's used in a high-stress area like the drive.

31-08-2009 06:45

sgreco

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

I personally wouldn't be too concerned about the chain, my team went the entire year with a swerve drive and no chain tensioning in the modules and never oncer had a problem with it. My team used 25 chain, which appears to be what it is in the picture, the Robonauts use 35, but either way it shouldn't make a difference. My team's chain did stretch, but through 3 competitions, they never stretched enough to require that they were changed.

It looks really nice though. (Any estimate on cost?)

The only concern I would have whould be on how thin the modules gets at the bottom. I'm not too good at eyeballing, but I'm guessing the side plates are 1/4 inch.

31-08-2009 08:59

ajlapp

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

These units have not been tested, but I know from experience working and talking with frc118 that they have had module damage due to side loads. Some other designs have addressed this by using much larger cross-sections or creating the wheel saddle from billet....I'm not sure how I'll proceed with this design.

There is no chain tensioning feature designed in. A certain amount of sprocket wear is expected. There is plenty of sprocket wrap to deal with it in my opinion.

Robonauts used #25 chain this season for the final drive without a tensioner.

There is no price on these units. Initial estimates make these far to expensive to manufacture. Miter gears are quite expensive, as are the large turned components.

31-08-2009 15:21

Tom Line

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

What supports the side loads on the horizontal shaft caused by the bevel gear?

You normally don't want to side-load axial bearings, so I've been scared of using e-clips on the ends of the shaft and having them pushing against the inner race of the axial bearings at each end.

31-08-2009 15:28

ajlapp

Re: pic: Revolution Co-Axial Swerve Module - Team 221 LLC.

The frc118 plan calls for thin walled bushings that hold the miter gear in location and push the thrust loads against the inner race of the bearing.

The prototype pictured has snap rings holding the miter gear in place. The same will be true for the drive sprocket, though they are currently not in place.