do tracks and wheels together make a better robot?

[gondorf]

is it true that having both tracks and wheels together make you more likely to be picked for the better teams. i just heard that they might be better for traction.

which brings up another rumor: do tracks increase ball accuracy?

[KenWittlief]

Tank tracks are one of those things that keep showing up on FIRST robots, in ways that I dont understand.

Friction requires a downward force. If you look at an army tank, or a bulldozer, there are idler wheels all down the side that push the track into the ground.

but I have never seen a FIRST robot with those idler wheels. If you dont have them, then what is pushing the tread into the carpet between the wheels?

ans: nothing!

I might be wrong on this, but a robot that has two wheels on each side with a tank tread, and a robot that has two wheels on each side that use the tank tread wrapped around the wheels instead (as tire material) should have exactly the same pushing force

and way less complexity

[Ken dons his fire retardant suit and hides under desk]

[sburro]

Originally Posted by KenWittlief

Tank tracks are one of those things that keep showing up on FIRST robots, in ways that I dont understand.

Friction requires a downward force. If you look at an army tank, or a bulldozer, there are idler wheels all down the side that push the track into the ground.

but I have never seen a FIRST robot with those idler wheels. If you dont have them, then what is pushing the tread into the carpet between the wheels?

ans: nothing!

I might be wrong on this, but a robot that has two wheels on each side with a tank tread, and a robot that has two wheels on each side that use the tank tread wrapped around the wheels instead (as tire material) should have exactly the same pushing force

and way less complexity

[Ken dons his fire retardant suit and hides under desk]

lokk at 663 robot last year
http://www.wcsrobotics.com/multi.htm

The idlers on the bottom could have been spring loaded but since it was a flat field there was no reason to.

[KenWittlief]

wow! hats off to you!

I think that is the 1st time Ive tank treads done 'right' on a FIRST robot

is your team sponsored by General Dynamics by any chance?

or Catapiller? :^)

regarding launcher accuracy - if a robot is able to turn slowly and precisely, then it is easier to target the goal

since tank treads have a lot of side friciton, they are usually geared down more than a robot with two wheels and castors (for example) - so a typical bot with treads will turn slower

and be easier to aim.

[henryBsick]

Originally Posted by KenWittlief

Tank tracks are one of those things that keep showing up on FIRST robots, in ways that I dont understand.

Friction requires a downward force. If you look at an army tank, or a bulldozer, there are idler wheels all down the side that push the track into the ground.

but I have never seen a FIRST robot with those idler wheels. If you dont have them, then what is pushing the tread into the carpet between the wheels?

ans: nothing!

I might be wrong on this, but a robot that has two wheels on each side with a tank tread, and a robot that has two wheels on each side that use the tank tread wrapped around the wheels instead (as tire material) should have exactly the same pushing force

and way less complexity

[Ken dons his fire retardant suit and hides under desk]

Ken,
I would like to thank you for finally bringing this into the light. I am pretty frustrated with teams that design drive-trains based on poor physics beliefs. From treads to unnecessary three motor drive trains...
Anyway, knowing vectors of force and co-efficients of friction are HUGE keys to building a competitive robot.

-Henry

[RogerR]

Originally Posted by Henry_222

Ken,
I would like to thank you for finally bringing this into the light. I am pretty frustrated with teams that design drive-trains based on poor physics beliefs. From treads to unnecessary three motor drive trains...
Anyway, knowing vectors of force and co-efficients of friction are HUGE keys to building a competitive robot.

-Henry

i'm curious about what you mean by 'poor physics beliefs'. both of those examples have valid reasoning behind them. and i'm pretty confident that their designers have at least a rudimentary grasp of Co.F. and vectors.

[KenWittlief]

we were talking about tank treads that do not have idler wheels. The photos posted in this thread are the 1st bots Ive seen that do have idler wheels (the right way to use threads)

un-necessary 3 motor designs are designs that dont need 3 motors on each side -it depends on what else the drive train can do. If a bot can spin its wheels against a wall, then putting more motors on it does nothing but spin the wheels faster

and spinning the wheels faster does not give you any additional pushing force.

[Ken hides back under his desk :^) ]

[greencactus3]

Originally Posted by KenWittlief

we were talking about tank treads that do not have idler wheels. The photos posted in this thread are the 1st bots Ive seen that do have idler wheels (the right way to use threads)

un-necessary 3 motor designs are designs that dont need 3 motors on each side -it depends on what else the drive train can do. If a bot can spin its wheels against a wall, then putting more motors on it does nothing but spin the wheels faster

and spinning the wheels faster does not give you any additional pushing force.

[Ken hides back under his desk :^) ]

but it lets you gear higher and = faster top speed. depending on how well you can control it.. but same with cars. who needs a car that goes 200mph... but people still buy because it has a high top speed. the potential. and just because they can... which we cant.. boo

[Jay Trzaskos]

http://firstrobotics.uwaterloo.ca/dr...insgallery.php

Take a look around on this site to see how tank treads have been implemented over the years. Actually, this is a great resources for any part of your robot.

JT
229

[gondorf]

tank treads may be a good thing for a robot but they are a pain to make.

from how i tried to do it tank treads are sort of like 4 wheel drive with a chain connecting it.

my team is having trouble with just 4 wheel drive, let alone a tread

[Mike Norton]

http://www.valleytech.k12.ma.us/robo.../2004VIEW5.jpg

http://www.valleytech.k12.ma.us/robo...2004track3.JPG

This is hard ? It is pretty easy to do. with BrecoFlex pulleys and timing Belt

[gondorf]

Originally Posted by Mike Norton

http://www.valleytech.k12.ma.us/robo.../2004VIEW5.jpg

http://www.valleytech.k12.ma.us/robo...2004track3.JPG

This is hard ? It is pretty easy to do. with BrecoFlex pulleys and timing Belt

you know if my team knew what brecoflex pulleys and a timing belt were we would probably pat ourselves on the back and act all proud.

i could probably figure out a tread if it wasnt for the fact that it has to be a team decision and othere dont agree on treads

[Jay Trzaskos]

Hey guys, let's stick to the discussion at hand.

If you would like to learn more about brecoflex timing belts take a look here . If you would like to learn more about how treads have been used in the past try searching the forums for old threads discussing the issue. I would also advise everyone to take a look at this website. It's a really great resource to use when dicussing designs, as I stated earlier.

JT
229

[Sean Schuff]

To accomplish a downward force on the track between the rear/front drive/idler does not require idler wheels. A rail (similar to older snowmobile designs prior to popular use of bogey wheels) will accomplish the same thing. It has to be designed right so as to not cause unnecessarily high amounts of friction. Without running numbers my hunch is that the bogey wheels are more efficient in the area of reducing friction.

With regards to the logic of using treads versus wheels - I think this year's game is a perfect example of the usefullness of tracks. Why? If your team wants to climb the ramp to score the points at the end of the match you need either ground clearance to the tune of roughly 4.5 inches on a 38" long drive with 6 inch wheels. This approach causes two problems that our team has identified - less space in the 28x38x60 box for robot "stuff" and a higher center of gravity. Tracks eliminate the need for ground clearance by providing contact all along the robot.

With that being said, our team is still using wheels this year but in a slightly different configuration than years past. Our team has not put much effort into tracks and if I keep mentioning them, Mike Johnson will kick me again!

My 2 cents - take them for what they're worth.

Sean

[Jonathan Norris]

Originally Posted by Sean Schuff

With regards to the logic of using treads versus wheels - I think this year's game is a perfect example of the usefullness of tracks. Why? If your team wants to climb the ramp to score the points at the end of the match you need either ground clearance to the tune of roughly 4.5 inches on a 38" long drive with 6 inch wheels. This approach causes two problems that our team has identified - less space in the 28x38x60 box for robot "stuff" and a higher center of gravity. Tracks eliminate the need for ground clearance by providing contact all along the robot.

Sean

My team did a test today with a extra kit frame with 6" 6 wheel drive, and only needed 2.5" of clearance. This is with 6 wheels not 4.