Success with Tank Treads

[Gary Dillard]

Originally Posted by Andy Baker

Treads are not trivial to design, build, and maintain. While they might not be to the level of "nightmare", they sure cause some sleepless nights.

The advantage of treads are:
1. Increases your ability to climb things
2. Provides a bit more traction, depending on the playing surface

The disadvantages of treads are:
1. Requires more weight allotment compared to wheels
2. Reduces your driving power due to a less efficient drivetrain (the belts must be pulled very tight in order to stay on, causing high side loads on your pulleys and bearings)
3. The cost is very high (more expensive bearings, numerous pulleys, costly treads, more spare parts).
4. They take longer to design and build. Our team has never been able to get a tread system driving before week 4. Prepare to have very little drive practice.
5. Losing a tread = losing a match

If you are putting treads on your robot, keep your belt tight, keep your pulleys aligned, and be sure to put a "bow" on the bottom surface of your tread (middle pullies should be lower than outer pullies).

That's just my opinion. Others might have had an easier time with these treads, but after putting them on team 45's robot for 4 out of the last 5 years, this is how I see things.

Andy B.

I agree with most of Andy's post - SPAM has had a tread drive system since our second year and it's evolved every year. It's hard to break down the design / manufacturing time in the drivetrain - our gearboxes are always very complex and switching them to a wheeled system wouldn't have saved much time. We were never power limited, always traction limited. Most people would agree that in 2002 we could push any other robot with impunity (except Mike Norton - still waiting for that video where you claimed to dominate us); last year we made some changes that apparently had major impacts because we lost / locked treads several times when being pushed from the side, including important matches such as the Division Finals.

I think we actually did win a qualifying match in 2002 with a broken belt, but we were already in pretty good position when it snapped.

The bow in the bottom (middle wheel lower) is a gotta have - we call that the "boogie wheel" because it allows you to turn on a dime without dragging / slipping the belts. Ours is spring loaded.

A couple other down points to consider:

Brecoflex belts (by far the best we've used) are very expensive and have a long lead time (probably why we were never driving until week 5)

Maneuvering takes longer and is harder to do in short spaces because of the added side drag.

Metal-in-Motion made the Finals with belts last year, so as far as success is concerned this is only one aspect that you need to make work for you if you choose.

[Mike Norton]

(except Mike Norton - still waiting for that video where you claimed to dominate us);

I found that video. What was happening was your robot would stall or stop running and we would pull you. then we would stall and you pulled us then we pull and you ended up letting go and went for another goal. But what happen we turn sideways and you couldn't push us out of your way so time ended with you not back in your zone.


I would say both robots were quite equal in power. but I think you had 2 speeds becuase you were quick off the mark.

I hope to see you this year in UCF.


Back to the tracks the best thing about them is if you do turn sideways not many if any could push you.

[Mike Norton]

Take a look at the new tracks for this year. a nice new look with a strong 1" shaft. Last year we spun 4 of our drive shafts, to much power so we are running with 1" this year.


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

[Cory]

Very spiffy looking pulleys you have there. Looks like we'll be seeing another powerful bot from 61 this year

Cory

[Gary Dillard]

Looks sweet again Mike - and to the point of this thread, you can see how much design and machining time goes into making a tread system work. The sprocket you see there comes solid stock, just the teeth and the bore cut; all the weight reduction getting to the cool looking spokes and the attachment holes plus the drive shaft takes design, NC programming and machining time.

[Greg Perkins]

Originally Posted by Gary Dillard

Looks sweet again Mike - and to the point of this thread, you can see how much design and machining time goes into making a tread system work. The sprocket you see there comes solid stock, just the teeth and the bore cut; all the weight reduction getting to the cool looking spokes and the attachment holes plus the drive shaft takes design, NC programming and machining time.

BAck in 95 when Nashua was a well known team, we used tracks for our bot...they were so well designed and made that they did not need to be replaced until after nationals! adn they were on it since around week 3! now the bot did horrible, but the drive was a tank!


Our team this year(134) has taken advantage of the awesome breckoflex tracks, they are totally amazing, a self tracking feature? who woulda thunken! and hey CD...Pembroke this year will be a force to be reckon with.

[Mike Norton]

http://www.valleytech.k12.ma.us/robo.../2004VIEW1.jpg

http://www.valleytech.k12.ma.us/robo.../2004VIEW2.jpg

http://www.valleytech.k12.ma.us/robo.../2004VIEW3.jpg

http://www.valleytech.k12.ma.us/robo.../2004VIEW4.jpg

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


Here are some pictures in cad to give you a better look at a simple track design

[Gary Dillard]

Hmmmm...... notice in my post I haven't said anything about this year's drive system. Could it be that team SPAM has abandoned its 5 years of development of a tank tread system in favor of something more....exciting?

[Tytus Gerrish]

Originally Posted by Gary Dillard

Hmmmm...... notice in my post I haven't said anything about this year's drive system. Could it be that team SPAM has abandoned its 5 years of development of a tank tread system in favor of something more....exciting?

I know, its a ...

Knoldge is a burden
Dont wory Gary, they wont hear it from me ,that is if your doing what i think your doing.

either way your going to take it out of the crate at UCF and everybodys going to be like WOW!

[Warren Boudreau]

Originally Posted by Tytus Gerrish

I know, its a ...

Knoldge is a burden
Dont wory Gary, they wont hear it from me ,that is if your doing what i think your doing.

either way your going to take it out of the crate at UCF and everybodys going to be like WOW!

Shhhhhhh... Let's make sure it works first. Afterall, antigravitic drive systems are still kind of hard to control. But we'll get something working by regionals.