Quote:
Originally Posted by staplemonx
Totally agree, problem we do not have any pneumatic wheels at the moment. So we are looking for other teams to share some of their testing results. We are expecting to have wheels in early feb if we make the purchase in the next round, but we need data now for a decision.
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Okay, let me take a different tack then based on my experience, this is how I'd answer your questions.
1: Assuming the two robots in the interaction are full weight and have enough torque to break traction the result of this interaction will depend largely on bumper position as well as if the pushing robot entered the interaction at any speed.
The robot with the lower relative bumper position should have a pushing advantage, because it tends to generate a force vector that serves to diminish your opponent's traction and enhance yours. A robot using a defensive strategy will probably want the lowest bumpers possible while still maintaining clearance for obstacles.
If the "T-boning" robot enters the interaction with enough force to cause the "T-boned" robot to begin sliding sideways it may continue to push the robot (dynamic friction vs static friction), but this has a lot to do with how drivetrain software works and driver skill. If the "T-boning" robot breaks traction with the impact, you end up in the same place (Dynamic friction vs dynamic friction).
2: Team indiana Ri3D used 15-17 psi in our pneumatic wheels and saw excellent driving performance. We didn't do any testing for pushing force though and our robot was significantly underweight. Basically if there is a traction advantage with deflated tires, as long as your opponent in this scenario doesn't know that, you win. If your opponent knows: stalemate.
3: Let's look at the traction limit. The basic physics model is a pretty safe place to start (Traction = Coefficient of friction * Normal force). Let's say you can get a 10% increase by deflating the tires some known amount, which is probably a safe, high estimate for what you might be able to achieve by adjusting air pressure. If your robot is full weight (147 - 148 is about the max unless you use something to generate extra downforce) we assume a 1.397 coefficient (AndyMark stated 1.27 coefficient of friction * 1.1) you can generate 206.7 lbs pushing force. Your stated gearbox and wheel configuration can produce 370.34 lbs pushing force at stall. You'll only ever be able to use 206.7 lbs of that force.
That said, the current draw is low, which isn't a bad thing, but you may be able to go faster safely. Here again, you can simply maximize your own performance. If you don't want to be pushed sideways or to be able to push another robot sideways there may be wheels with better traction options and that would be the way to go if that is a goal for the team.
4:Head to head pushing matches are a funny thing. Unless you implement some kind of "traction control" this is going to come down to your driver. If the contact the other robot and slam the controls forward, they'll just spin the wheels.
I hope this is better, more useful info. Again, if you have questions, let me know.
Also, the JVN Mechanical Design Calculator is your friend.