pic: My First 6WD

This is what I have recently come up with, a 6WD with a center wheel that’s dropped 1/8". I have some CAD training but this is my first complete project on my own and my first 6WD or any drive train. So any comments/suggestions would be greatly appreciated. (please note this is my first drive train to CAD so I might have a few mistakes in there)

Not bad for a first run. It’s especially cool that you’ve visualized the chain paths.

If you are running the sprockets on the outside, next to the wheels, you can bolt the sprockets to the wheels themselves and use a dead axle instead of a live axle.

Looks good, except for one thing: Chain routing.

For a rear-mounted drive system like this, I’d suggest chaining one run to the rear wheel from the transmission and one to the center wheel from either the rear wheel or the transmission, depending on how much of a redundant system you want.

I would recommend supporting those Super Shifters with more than just two bolts each.

Agreed. Try adding some alum angles to connect the tops of the transmissions.


A long rod of 1/4" all thread also works nicely.

Dropping the shifters down, and direct driving the rear wheels off the transmission shaft is another option to reduce unneeded chain/improve bulletproof-ness

Basic frame looks quite good though, keep it up!

This looks really good! The only suggestion I have is to give some consideration to how you plan to mount bumpers on future drivetrains.

One thing to always think about when drawing is how your parts are actually going to be put together. Are you welding your tubes together? If so, consider that there will be a weld bead on those tubes unless you want to take the time to grind them down flat (which can also reduce their strength). You have your super-shifter bracket sitting directly on top of one of those weld points.

Next, why do you have the super-shifters in that orientation? Why not turn them so that the sprocket is higher off the frame to offer more accessability in case you want to make changes or need to do a hasty repair?

How are you going to tension the chains? Specifically the change from the center wheel to the super-shifter. I would suggest putting a push/pull block there or at least a jack-bolt to use to move the supershifter if you plan on slotting the connecting plate.

Why does your mounting bracket on the supershifter go so high that it you have your drive shaft going through it? This will require you to pull the sprocket if you ever need to remove the supershifter. Pulling sprockets with keys can be VERY hard to do if they’ve been on for any length of time.

Is there a particular reason you’ve put the supershifters so far back on the frame? By putting them near the middle wheel you can save weight on that chain run.

I would also suggest cut-outs that allow you to reach in to work on your middle bearing blocks from under the robot. From experience, the guys of FRC robots can get very congested and any easy-access to things like drive-trains will only be praised when you get into a tight spot.

Is there a particular reason for that structural beam just forward of the “back” of the bot? You don’t really need it just to support the supershifters.

The absolute key to good cad is to understand exactly how your design will be made. If you don’t, you’ll likely get yourself into a situation where what you’ve drawn is impossible or improbable to manufacture.

Very nice job for a first try!

Along the same ideas as Tom, I’d recommend orienting the SuperShifters so that the output shafts are concentric with each other. That way you have identical chain runs on both sides of the drive train frame and can mount the chain tensioners in the same exact way.

Alright. Here it is a little late but oh well. I took all the suggestions in and they worked out very well. But for the chain issue on the first one, there was a spacing issue but I worked it out. (sorry this took so long but i haven’t been on the computer recently and i just learned how to attach photos. http://www.chiefdelphi.com/forums/attachment.php?attachmentid=9500&d=1292383225