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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.
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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.