Re: "Hopping" With tank style turning.
 

I disagree. It might take a while for them to arrive, they are moderately expensive, and the downside to omni-wheels is that you lose a lot of pushing power. If someone wants to push you at an angle, you might as well throw in the towel. A much better solution is just to get yourself a bit less traction on 2 or 4 of your wheels by applying zip-ties, tubing, nylon, whatever you have lying around (experimentation will be needed here). Like I said, we just picked a different tread for two of our wheels last year and it drastically cut down on hoppage.

EDIT: sorry for the not-so-good wording, I'm talking about loss of pushing power in directions other than forward, which will probably end up being a high percentage of the total pushing.

Re: "Hopping" With tank style turning.
 

How so? Omniwheels are designed to have little resistance to sideways motion, but they have plenty of traction in the forward/backward direction. They don't make you lose any power. In a straight pushing match, you won't automatically be outmatched just because you're using omniwheels.

You might be thinking of a holonomic drive configuration, where the wheels are mounted at an angle to the direction of travel and thus use up some of the power to spin the rollers during normal operation, but that's not the case being suggested here.

Re: "Hopping" With tank style turning.
 

I think he means if the opposing team sees omniwheels in the back, that's where they're going to bump you (from the side) to screw up your aim ;)

Re: "Hopping" With tank style turning.
 

You can add some deployable skids on one side of the robot.

Anyobody ever experimented with toe?

Re: "Hopping" With tank style turning.
 

Guys,
So everyone understands, the "hopping robot" is a symptom of a potentially serious problem for the electrical health of the robot which is why I address this issue in a number of threads. Your robot will stop hopping when the battery becomes so drained it can no longer cause the motors to overcome the friction with the floor and break loose their hold with earth. During turns with this type of drive design, we have recorded currents above 250 amps. (Remember that the small Chalupa motors have a stall current in excess of 100 amps each, and you are forcing the motors to near stall in a turn.) Electrically speaking, the battery has an internal resistance of about .011 ohms. Doing the math on Ohm's law, that amounts to almost a 3 volt drop on a good battery. Since the RC will cutout below 8 volts, your robot is in danger of going to sleep every time you turn. By now the main and branch circuit breakers have warmed to the point of failure. Add a few more amps for other accessories on your robot and you won't need to worry about getting into a pushing match. Your alliance partners will just push over to the side to get your hardware out of the way of operating robots.
Yes, that is an extreme situation but it does happen all too often. If you ask me for help, you might not like the answer but I am going to give it to you straight. If you come to play, I am bound to help you play.

Re: "Hopping" With tank style turning.
 

Heres an idea, put two casters on the end of pneumatic cylinders and mount the cylinders in one corner of the robot near the front or back. Then when you want to turn extend the pneumatic cylinders and you will raise up the front of your robot a little so those two wheels don't touch the ground. Then when you want insane traction you can retract the cylinders and your robot is back on the ground. We did something like this in 2004 to help get on the ramp and it worked quite well.

Re: "Hopping" With tank style turning.
 

raise one of the wheels about 1/8". You will drive on 3 under normal circumstances. This is why mant teams have gone to 6 wheels with the middle set of wheels slightly lower than the four outer corner wheels.

Re: "Hopping" With tank style turning.
 

This year our 4 WD robot has a tendency to hop because the tires are very sticky and we reduced air pressure slightly to better climb the ramp. We used this to advantage in a scrimmage yesterday to free up a ball jam in out hopper. It makes it a real bear to drive, but we were able to push any other robot on the field quite easily.