Tank tread

[Lil' Lavery]

Originally Posted by DeepWater

Maybe but I find it hard to believe that the two omni wheels (driven in the same direction) would have enough traction to overcome any "decent" traction wheel. Maybe 2 AndyMark Omnis vs. 2 of the KoP Skyway wheelchair wheels but then wouldn't it just be much more efficient to just use 4 omni wheels?

Omni-wheels (theoretically) have no less traction in their "Y axis" (forward/reverse) than regular wheels do, so they would have the same slippage point as the drive wheels. In practice this is not always true (particularly with traction wheels and omni-wheels with plastic rollers), but with the right wheels it could be. Say they use AM Trick Wheels with the black EDPM rubber rollers and lower traction drive wheels.

[chs1368]

but if we get hit from the side, if we have 4 omni wheels, we're gonna move in the direction we're hit in

[AV_guy007]

Originally Posted by chs1368

the reason i put motors on the omni wheels is that if were stationary and turning we could turn a lot faster, also this would allow us to turn while we were in motion (like moving forwards) another is say for last years game if we had a stationary turret to shoot those balls, we could make precise adjustments to where our robot was facing

you said the extra motors (on the omni wheels) were so you could turn faster but a 2 wheel drive setup will turn very quickly whether you have 2 un-powered omni wheels or ball casters and i am not sure you would be able to make more precise turning with them unless they were geared to drive slower

[ChuckDickerson]

Originally Posted by chs1368

but if we get hit from the side, if we have 4 omni wheels, we're gonna move in the direction we're hit in

The whole point of an omni-directional drive train is that you can out maneuver a pusher type robot like a tank tread, 4WD, 6WD, 8WD, etc. so you never have to worry about getting pushed around. A non-omni directional robot (typical FIRST type 4WD, 6WD, tank tread, etc.) is designed to push it's way around but will not usually be as maneuverable as an omni robot. I think you are trying to do both but in doing so you may not succeed in doing either very effectively. My suggestion is to think about two separate designs (one made for maneuverability and one for pushing) and then on Saturday decide what your game strategy will be and go with whichever design you feel will best match your game strategy.

[A_Reed]

one more note on treads : if they are properly tensioned(not overly tight and not loose) they can be very reliable. in 2006 we only broke only one tread, any other replacements were do to wear over the two previous regionals, compare that to 2004 when we snapped 4 over three regionals and nationals on account of losing tension in the middle of a match.

[eshteyn]

Hey guys, ive read all your posts and i have to say alot of you have great arguments for your reasoning, and i agree with most of you. Everythign in the end comes down to the game and the history of design of the teams you will be opposing at regional events. For team 1368 i suggest analyzing the game as well as the opponents then decide what you want to do, also as for belt drives the friction force of the belt on the pulley is less than the force put out by a pushing robot, so if you get hit and pushed, you WILL get pushed and your belt system WILL slip on the pullies. Also i suggest a simple rocker drive system with powered wheels in the center powered by CHAINS with 2 omnies on at the sides of the robot, this configuration works best.

[A_Reed]

Originally Posted by eshteyn

Hey guys, ive read all your posts and i have to say alot of you have great arguments for your reasoning, and i agree with most of you. Everythign in the end comes down to the game and the history of design of the teams you will be opposing at regional events. For team 1368 i suggest analyzing the game as well as the opponents then decide what you want to do, also as for belt drives the friction force of the belt on the pulley is less than the force put out by a pushing robot, so if you get hit and pushed, you WILL get pushed and your belt system WILL slip on the pullies. Also i suggest a simple rocker drive system with powered wheels in the center powered by CHAINS with 2 omnies on at the sides of the robot, this configuration works best.

With Splined(Toothed) pulleys,from brecoflex, you will not get pushed from the front and with the correct belt profile(V shaped profile in the center, TK10-K13) your belts will never slip sideways, this mixed with the long contact patch basically means you won't get pushed sideways either. the only pushing weakness of treads is due to your gearbox, if you don't have enough torque you will get pushed front to back or if the opponent catches a corner of your robot you can be spun.

[eshteyn]

Originally Posted by A_Reed

With Splined(Toothed) pulleys,from brecoflex, you will not get pushed from the front and with the correct belt profile(V shaped profile in the center, TK10-K13) your belts will never slip sideways, this mixed with the long contact patch basically means you won't get pushed sideways either. the only pushing weakness of treads is due to your gearbox, if you don't have enough torque you will get pushed front to back or if the opponent catches a corner of your robot you can be spun.

There seems to be a mix up, i meant that the belts will lose grip on the pullies they are driving and will slip on them, even if the belt is toothed, there will be a point where it is stretched out a little bit from use and will no longer grab on to the pulley like it used to, then it will slip on the pulley.

[Protronie]

Track drive / tank treads have there good points and bad.
On a light unit the tracks will tend to come off the idler wheels... and they will be a lot of adjusting to make them work right. They great for climbing ramps and pushing other bots out of your way (if you got the motor and gearing for it) but other than that there just a headache.
I think speed gonna be needed for this game... wheels the answer.

[GVDrummer]

Hey, just some quick insight if u do decide to use a tred system. I am on team 288 and we have been using treds for the past 7 or 8 years and it takes ton of time to get everything to work properly. If you still decide it will take a long time which will take away from the other problems you'l face like scoring. It took us 3-4 years including the off season to perfect it. If you can get it to work efficeintly in 6 weeks... you eather were lucky or very smart people.

[Mike Norton]

team 61 has been doing tracks for over 10 years and we stop due to Breco flex could not make us a belt that would not rip. the power we where using where ripping the belt. at $340 a belt we went with wheel last year. Had some good results. Track are great and are better than wheels only if you can keep them from breaking. the power that is given to us now is way to much for the Breco flex belts.


we go with 6 wheel system almost the same results as a tank drive system

if you want to see the tracks go to our web site

http://www.valleytech.k12.ma.us/robo...photos2004.htm

[team 1094]

if you are going to use a tank tread desing you mite want to keep in mind that it is very hard to ketp a tank tread on with out giving it tooo much slack. also im couries on how you plan to trun your robot.

kyle from (team 1094)

[Andrewpbhs]

If your Robot is made correctly, and centered in it's weight the robot should have no problem turning around in a 360 degree....