pic: Cheap 6WD

[sdcantrell56]

I don't think using another tube in the hole will really help the problem. You need to have the bearings in some type of plate and then the plate fastened to the wood with bolts or t-nuts to spread the load. The best thing to do that I can think of is to have to plates of aluminum sandwiching the wood and then have them bolted together with bearings in each plate. Also, why use hardwood? Baltic birch is more than strong enough and is a lot more uniform than hardwood lumber. You can always layer 2 pieces of plywood to get a thicker piece.

On a side note. I have been designing a ton of drivetrains with wood and I just keep coming back to aluminum. Wood although cheaper, seems to be a bit more difficult to build and design with to get the same functionality. Maybe I just haven;t come up with the right thing yet but so far my aluminum designs are winning in my mind.