Has 6 wheeled designs surpased tank treads

[ShadowKnight]

Well, treads will actually provide a better traction system than wheels on very high torque low speed robot simply because they distribute the weight. Asuming coefficent of fricition is constant for any wheel/tread in contace with the ground, if the treads are distrubuting the pushing force on a greater surface area, the tread system will allow the drive train to provide greater overall force before the treads slip than a wheeled design. This is not because surface area affects friction, but because the force is distributed.

The decision to go with treads as opposed to wheels is depenent on the force exerted by the wheels/treads on the carpet. If in fact the force of the drive train will cause the wheels to slip, than a tread design may be preferred.

[Paul Copioli]

ShadowKnight,

The force being distributed along the tread has absolutely nothing to do with the ability to push, unless... the surface that your treads contact fails due to the contact. If the wheel design is wide enough such that the force imparted on the carpet does not make the carpet fail (i.e. tear apart like in 2002), then it will provide the exact same pushing force as a tread made of the same material provided the robot is the same weight.

Mike Norton's post is very accurate, but notice that the advantages of the tread design (disadvantages, too) really are not related to pushing force. Regarding Mike's point #3, I guarantee that if his team put a six wheel design with the same tread material they would still be in the top 5% of pushing robots.

Now, specifically regarding 2002: treads had a much better chance of not tearing the carpet than wheeled designs because they distributed the load. Tearing the carpet leads to less traction. The carpet of 2002 related to the possible weight of a fully loaded robot (around 500+ lbs) was like sand to a construction vehicle. Treads helped dissipate the pressure on the carpet to a point where the carpet would no longer fail. Wider wheels would provide similar functionality.

-Paul