Hey FIRSTers!
We’re planning on using a 6 wheel drive train with 2 plaction wheels in the centre of the bot and we’re wondering whether rubber or plastic treads on the other 4 would be better for maneuverability.
Opinions, advice?
It depends on your gear ratios, wheel diameter, and whether or not your frame is set up for dropped center wheels which all affect the friction against turning. If you are doing dropped center wheels you should have no problem overcoming the friction from side scrub when turning. If you don’t have the engineering mentors to calculate these forces, you can always rely on building and testing your robot on carpet similar to the playing field. Make sure your drive base is weighted to the final maximum weight allowed. I’ve seen rookie teams build and test on linoleum or similar hard surfaces only to find that when the robot was fully assembled or placed on carpet it couldn’t handle the turning loads.
We’ve had no problems with turning with any of our 6WD robots with traction wheels at all positions. They were dropped center designs.
Remember that the easier it is for your robot to turn itself, the easier it is for other robots to turn you. The slicker your outside wheels, the quicker you will turn - at the cost of some pushing power (since the outside wheels touch the ground when you push) and the ability to “hold your ground” against somebody pushing the front or back of your bot sideways.
Well if you used Omni-Wheels in the front 2 and the back 2 wheels of your 6 wheel drive system then you can easily turn around without skidding and then you won’t need to drop the center wheels. This also allows enough traction in the front and back wheels to counter-act the pushing you can recieve from other teams in attempts to turn you.
I agree… add one set of omni-wheels and link them to the drive chain for redundancy then add a pair of slicks for stability. Two sets of omni wheels seems overkill.
Can anyone second this? Is there a video of a configuration of 1 set of omni’s, 1 set of plaction and 1 set of slicks?
I actually came up with the idea of a 6x6 configuration with omni-wheels in the front and back 2 days ago for one of the teams I am mentoring. It was quickly brought to my attention that even with the center wheels there for traction, no matter how wide they are and how much traction they may have, it will still open you to being a much easier push should you get nailed from a corner. I am not sure how correct this information is, but it is sensible none the less. A suggest that was made was just to put omni-wheels in the front. However, if I were to put them on one side only, they would surely be in the back as we are likely to put a manipulator on the front.
This is my take. Also, I was pondering the idea of the dualie omni’s.