Cantilevered drive wheels?

[sanddrag]

696 has used cantilevered wheels for the past three years. It ends up saving a good deal of space and weight, as well as giving a wider footprint for better stability and turning moment, and it allows the wheels to come off easily for replacing tread. The only downside is if someone pushes a bumper up against your wheels, you might be stuck goin no where. But you can put in gaurds for that if you'd like.

[meaubry]

Team 47 has had both types of wheel to frame designs.
Both have worked out okay, but we prefer supporting the wheel axle on both sides.

Reasons include -
Loads are supported better.
Wheels and chain are protected better.
Easier to mount bumpers with an outer frame.

Mike

[kramarczyk]

One thing that hasn't come up yet is the loading on the axles. Cantilevered axles have a much higher load bending loads on on them than axless that are supported on both sides. We opted to go with cantilevered shafts for the wider base and ease of maintenance (which proved to to be the right choice for us.) But we looked at the math and planned accordingly when picking shafts - 5/8" Igus shafting.
Despite some of the other problems we had relating to keyways and such, we never bent a shaft.

This spreadsheet should help clarify the math...

[dbell]

Thanks for your advice everybody.
If you use cantilevered drive wheels you probably a live axle(right). But how do you attach the wheel to the axle, and have good support? And keep the wheel from falling off?

[Gabe]

Assuming you have a key or use hex shaft, then transferring rotation to the wheel is done by rotating the shaft, There are two common ways of fastening the wheel to the axle: the first is by attaching a hub with a flange onto the axle, then the wheel is screwed on or off when needed. The second way is to machine an integral hub onto the axle, like this
(Yes, CD members, I know this picture is for a different part of the robot) Then the wheel with a matching hole profile is put on the shaft/hub.

As for keeping the wheel on the hub, you can use retaining rings that clip into a circular groove around the end of the shaft, or screw the wheel onto the hub.

[Qbranch]

Our 2006 shooter bot used cantalievered wheels on our track systems, If any of you remember us having issues with tracks getting walked off if we were being pushed around a turn, we fixed that in the off season.

The fix was, always use two ball bearings, not one, even if the specs say it can take the torsional loads...

Anyhow, yes, cantaliever wheels do take a little more work (we had to design and machine our axles) but they make the robot extremely easy to work on.

-q

[Daniel_LaFleur]

We use non-Cantilevered drive wheels because as a defensive robot we expected a lot of torque and shock running through our drive system.

We used pneumatic tires so we did not have to worry that much about tread wear (like those that use roughtop).