Re: 4-wheel drive trouble
 

Try wrapping a pair (one from each drive train) of tires with something radially. I understand this is kind of a dumb solution, it makes more sense to just get wheels or tires with the right treads, but its easy, cheap, and quick.

At first we tried 1/16" steel cable, but it wasnt big enough to lift the wheels off the ground. We probably shoulda have tried again with thicker cable, but that stuff is REALLY tedious to work with (think 100+ ft per pair and something like 130 individual wraps). So we had some zip tries lying around... They are excellent at reducing cross-wise friction (it turns on high gear now) but they did take away significantly from traction in the direction we need. Regardless, we can climb 6 inches with our two drills and 12.5" skyways, so im happy.

Re: 4-wheel drive trouble
 

How bout this:
Replace 2 wheels with omni's...
Probably the rear wheels. This will retain your 4 wheel strength while making your turning much slicker. I also think that with a small chamfer on the front wheels should do the trick.

Re: 4-wheel drive trouble
 

are there any off the shelf 12 in omni or transwheels? i'd love to have them. never seen any big sized ones tho. probably too heavy. we can't machine our own, but id really like them

Re: 4-wheel drive trouble
 

Why not try zip ties? They're cheap, slick, durable, and quick to install!

Re: 4-wheel drive trouble
 

Is that tuesday or thursday?

Re: 4-wheel drive trouble
 

It is both, yet neither. :P

Re: 4-wheel drive trouble
 

Please read my whole post....

Zip ties are really a half-assed solution. They kill probably more than half of your forward traction for the wheels you put them on.

Re: 4-wheel drive trouble
 

Well, I didn't have much luck finding an actual 12" omni... but...
You could make a small plate (doesn't even need to be circular) and bolt or lock an omni at each corner. Basically you're making a bigger omni with off the shelf omni's that are smaller. All it means is that you need more small ones.
You should be able to do this with common tools.

Re: 4-wheel drive trouble
 

Another solution that does not involve changing you robot dimensions or wheels is to place more wieight on either the front or rear wheels. If either end has more weight than the other, you will be able to turn easier because the heavy end will have more traction than the light end, and will be able to slide the light wheels around the corner.

Re: 4-wheel drive trouble
 

Quickest way is to lose some traction from one end or the other. Any chance at resurfacing one set of wheels with something slipprier? Possibly the edge profile is very square and sharp, and will snag more than slide when you are trying to pivot sideways. If you can bevel one or both sets of wheels to a more rounded profile it could help. We did the 2:1 gearbox last year and had to combine one pair of the sticky pneumatic Skyway wheels with one pair of the (slipprier) Polyurethane wheels, but it was still very difficult to turn with about an 18 inch wheelbase. It required a different driving style. Sometimes we had to actually reverse one side while driving forward on the other in order to get it to turn. I couldn't get it to turn well while driving normally, but some could do it while another sat on top...on pavement!

Beautiful craftsmanship on your robot, by the way. Love it!

Re: 4-wheel drive trouble
 

Stop stealing my lines.

Re: 4-wheel drive trouble
 

It may sound bad but it truly works...or at least it did for my team.but of course if you can find an Omni or more torque in your drive you would want to go with that and only use zip ties in a last minute, between matches solution

Re: 4-wheel drive trouble
 

it might be helped if you also describe how you are turning it. if you have 2 joysticks for each of the sides for tank drive, are you moving one back on the y axis, while moving the other forward on the y axis?

our team had a similar problem a while back, and what helped was with the drivers, instead of full forward and full backwards on both sticks, alternate the sticks, going one forward, and the other backwards, it will be a slightly slower turn, but it might help.

Re: 4-wheel drive trouble
 

Problem solved, check this thread

http://www.chiefdelphi.com/forums/sh...ad.php?t=25482

thank you all !