Chief Delphi - Going over 6 inch step with 12 inch wheels

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Re: Going over 6 inch step with 12 inch wheels

Quote:

Originally Posted by Al Skierkiewicz

Joe,
I think if you watched closely, the robot front tires are actually being pushed into the step edge. The resulting force combined with the turning ability of the tire results in the tire climbing the edge. The robot front wheels would climb even if they weren't powered. (Think of a bike going up a curb.) There is just more point friction on the front tires. Lowering the air pressure in the rear tires should help quite a bit. Some teams have added some friction enhancers, i.e. teeth or grippers, to the tires. These grip the edge during climbing and do not allow the tires to slip on the platform edge. I have seen grippers mounted right on the tire and on a wheel attached to the tire.

Thanks for all the replies from everybody.
You Guys are the best.

Joe P

Re: Going over 6 inch step with 12 inch wheels

I have a similar question about the smaller wheels:

We were considering replacing our dysfunctional swerve drive with a wheel setup that might actually give us the mobility to perform on the field. We were wondering if it might be feasible to, at the same time, climb up the steps. So my question is, can we manage to clim the 6 inch step with 8 inch wheels, given that we have a 3 inch foot? I know that theoretically, we should be able to, because with the foot down, the center of our 8 inch wheels are over 7 inches off the ground, and with a little shove, we should be up. I was wondering if anyone actually tested this themselves, as this would help us decide between what replacement we should select.

Re: Going over 6 inch step with 12 inch wheels

it's probally a balance problem, we had the same problem until we decided to flip the sticks around and drive the robot backwards. when we got the weight to the front we got up fine

Re: Going over 6 inch step with 12 inch wheels

My teams robot has 4 16in wheels and we found that putting extra weight on the front helps. Also, we keep them all a little deflated but it took a while to find what the optimum amount of air was. Maybe during practice rounds you could experiment with the pressure a little; make sure to have the same amount on either side or you won't be able to drive straight!

Re: Going over 6 inch step with 12 inch wheels

I don't know if you guys have any type of arm, but thats the key. In NJ, our robot would bounce and bounce and bounce for about 40 seconds until it got up the ramp, and then we had to do it all over again...wasn't pretty. This way was with the hook in the back. Next match we turned the bot around and extended the arm in front of our robot, we were on the top step hanging in 15 seconds...the start of our success.....try it with an arm if not...might i recommend zip ties and pneumatic tubing....

Re: Going over 6 inch step with 12 inch wheels

If you guys can get the front wheels on easily and are having trouble with the back wheels, have you considered using a small piston on the back end to lift the rear of the robot enough to clear the platform. If you lift the back of the robot, you can pull the robot forward with the front wheels until the back wheels are on the platform, then retract the piston and continue on.

Re: Going over 6 inch step with 12 inch wheels

We also use 16" wheels, and had a little trouble getting up the step. We added some weight to the front (on the bottom) and now have no trouble. A lot of the other suggestions are good too, if you don't have weight to spare.

Re: Going over 6 inch step with 12 inch wheels

My team quickly realized that so much can happen on the platforms. (tested out our tread drive subsystem and flipped every time) What I would suggest is add another 2 feet to your arm/hanging mechanism so that you can hang from the floor. We have a light (4 lb) 12' telescoping arm, the extra 2 feet was well worth it for us. I realize this might not be possible, but just tossing another idea out.

Re: Going over 6 inch step with 12 inch wheels

for all teams that have problems with turning and the like - in the future, use 6 wheel drive. all your problems will be solved

Re: Going over 6 inch step with 12 inch wheels

Quote:

Originally Posted by jjdebner

This may sound silly. But if you reduce the pressure in the tires to get more traction then if it is a four wheel drive system won't it jerk and jump when turning alot more. So it is basically a trade off between turning and climbing. Unless you have "special wheels". So just make sure you can still turn when you have some pressure taken out.

We use a pnuematic cylindar with a delrin skid on the end to lift the robot's rear two wheels while turning. This enables us to have a 3 point turn, 2 being powered, the other being a skid. The piston ONLY engages (theoritically) during a turn, as defined by software. While going foreward (i.e. pushing, climbing), all four kit wheels are engaged on the ground for full torque/traction.

Definetly take some pressure out of the tires to climb. I'm also thinking more weight towards the front of the robot will help. We've found its not so much the diameter issue on the wheels, but the traction the tires get on the diamond plate. Our robot could climb up the side of a diamond plate wall until it reached the point where it would flip (around 12" high). By decreasing the pressure, you'll increase surface area of the wheel against the diamond plate. More surface area = more traction = more climbage (climbage a word?...dunno..)

If what I said makes sense, ALRIGHT! If not, lemme know!

Re: Going over 6 inch step with 12 inch wheels

My team looked into doing this early in the year, here was our ideal. Put a skid leading to the back wheels, and put the weight in the front, creating a fulcrum along the skid, the weight on the front wheels will pull the front wheels to the platform, and pull you up the step. Simple, yet effective.
Ivey