Pneumatic Wheel Swerve

[jkelleyrtp]

On our team's list of goals to achieve, we obviously wanted to be able to cross the defenses, but also align properly in the limited space in the neutral zone. We really want to do pneumatic wheels to get over the rough terrain, but swerve to navigate easier and lock our wheels in for shots.

So how does a pneumatic wheel swerve sound? I put together a little something in CAD to illustrate the concept. I forgot to disable the transparency on the sprockets in the first image, but the second one shows it.

"Why is the sprocket so big?" you ask. One of our mentors considered traditional modules to experience significant loads when on just a few wheels and unable to hold up. I attempted to mitigate this problem by using a slotted delrin ring strapped onto the bottom the tube. This helps by having a grove to keep the module in place as well as distributing load on around 15 square inches of slick plastic.

So what do you think? I tried to keep the complexity down so only 4 gears per module and versaplanteries with encoders to turn the modules. Would this be too complicated or just outright unable to work?

Also is there a better way of turning the modules without adding another 4 motor controllers?

[Peyton Yeung]

If you haven't done a swerve before I would be hesitant on embarking on that challenge during the build season. Based on our initial testing, powering through obstacles will be relatively strenuous on your drive train so take that into account.

[gerthworm]

I helped with a pneumatic wheel swerve in college. We had a much higher weight limit and greater freedom in the choice of parts which helped a ton. Definitely possible, in general. However, the whole mechanism was still somewhat fragile - I'd be super worried this year about a module getting wedged in one of the defenses and burning out a motor. I wouldn't do it, but that's just me.

Edit: Here's some pictures of what we did: http://imgur.com/a/JkeBG

[dmorewood]

I actually ended up building a pneumatic swerve earlier in the fall. It worked but was heavy and really big. The wheels I ended up using were 8" diameter wheels from McMaster-Carr

[jkelleyrtp]

So we might not be doing swerve, but for my own edification I'd like to know the key areas of stress in a swerve module. I assume there will be a cantilever force through the central axle as well as loads into the chassis and into the retaining bearings.

There will also be a force acting down and away from the axle protruding into the module, creating a pivot point.

I plan to isolate vertical shaft displacement with retaining clips and maybe even shaft collars, but I really don't know the numerical loads it will face. What have I missed? How in Solidworks can I get a stress analysis based off of the loads?