pic: 6wd Chassis Design

[Aren Siekmeier]

Originally Posted by Alex.q

But if I eliminated the axle brackets, I wouldn't be able to slide the axles to tension the chain. That was the idea behind using them as I did.

Can't you slot both sides of the box tube like you did in one side of c-channel?

Originally Posted by Alex.q

Would box tube really make it much more rigid?

Yes. At 1/8" wall it's less likely, but C-Channel will still collapse on the open side much much sooner than box tube. Think about just the profile of each of them and which would hold up better. Closed rectangle > open c.

Originally Posted by Alex.q

Do you mean a cam that pushes the chain down, or do you mean a cam that rotates to push the axle brackets farther out? Assuming you meant the second thing, then I was wondering why that keeps it tight. Couln't the force just cause the cam to rotate an pull the brackets together as you described before? (I'm not saying it doesn't work, just that I don't understand why it does)

You can do either. The principle is that of the inclined plane. The angle of the cam and the friction between it and whatever it moves are such that no force exerted back onto the cam will turn it, but you can still turn the cam. Thinking of just a block on an inclined plane, given a downward force, the static friction force <= mu*tan(theta)*mg, so if mu*tan(theta) is greater than 1, then the frictional force will always be sufficient to keep the block in place, no matter what force you exert straight down. However, if you push sideways (up the ramp), you don't get the same force of friction and can move the block farther up (or farther down) at will. The block moves when you want it to, and not at all otherwise.