pic: Cheap 6WD

[s_forbes]

Originally Posted by Madison

Can you describe the power transmission components in more depth?

Assembling reliable power transmission schemes is the most difficult part of building a FIRST robot's drive train. Without learning more about why you've selected an unorthodox series of chain paths and wheel locations, I would be hesitant in recommending this to any teams with few resources.

Well I wouldn't recommend it yet... I would hope that others could offer some criticism and improvements.

Starting at the transmissions, we have two AM toughboxes with the extended output shaft option. The face of the transmission is attached directly to the wooden framerail. On the output shaft, there is a spacer, then a sprocket (12 tooth AM), and then a 5" Banebots wheel. These are held on with a cotter pin and a washer.

The other axle assemblies are similar, with the sprockets and wheels held onto the 1/2" keyed axles by washers and cotter pins. At the moment, I have the flanged bearings sitting right in a 1.125" hole in the hardwood, but this part that worries me the most at the moment. (maybe an aluminum insert?)

That's where I have it at the moment, if you see any problems please point them out.

Originally Posted by Alan Anderson

I don't see your reasoning. The way I'm looking at it, the rear wheels carry more load than if the center wheel were not lowered (up to half the robot's weight or even more, depending on the center of gravity). They just do it intermittently -- which seems likely to cause greater shock loads on the axle when the robot rocks backward.

I was making the comparison between two 6WD frames with a dropped center wheel (I might not have made that clear enough in my first post). With this configuration, the end wheels support a much smaller portion of the total robot weight, especially if it's center of mass sits right over the center wheels.

That is a good point about the shock loads to the transmission, though.

Originally Posted by sdcantrell56

Overall I like it but why wouldn't you just run all the chain on the inside? Also Maybe look into 8wd with the transmission centered and chained to the center pair of wheels. It would increase ramp-climbing ability while keeping the same center of gravity.

I considered this too, but for this particular version I wanted the transmission face to be flush with the framerail and the wheels to be close to the frame. In its current configuration, the rear wheel is about as close as you can get it to the transmission. (although, it could probably be made to work as you stated as well)