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Unread 01-11-2003, 04:31 PM
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Question tank treads vs. threaded wheels

which is better for the task at hand, having a tank tread system set up or a system of wheels in which the tank tread material is glued to the outside of the wheels?

thanks
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Unread 01-11-2003, 10:22 PM
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It's illegal to modify wheels by adding material to the outside.
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Unread 01-11-2003, 10:23 PM
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errrr I know what your thinking of and it isn't illegal. You can' t glue the treads onto the wheels. You'd have to use pulleys and then have the belts wraped around it. Glueing it wouldn't work
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Unread 01-11-2003, 10:37 PM
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Tank Treads

Definatelly treads, but, dont waste your time trying if youve never done it before, its expensive, and difficult to do.
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Unread 01-11-2003, 10:50 PM
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Quote:
Originally posted by srjjs
It's illegal to modify wheels by adding material to the outside.
Please elucidate yourself better.

It is illegal to add material to the outside of purchased wheels.

If you manufacture your own wheels, you may add material to the outside.
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Unread 01-12-2003, 12:23 AM
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If that is true, was it true last year?

Cause we bought skyway wheels (actually the same ones that came with the kit this year) and we screwed more grippy rubber belt onto them. We had no problems with any rules of "not adding things to the outside of purchased wheels".

...and I don't recall ever reading a rule that said anything like that.
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Unread 01-12-2003, 12:41 AM
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Quote:
Originally posted by M. Krass
It is illegal to add material to the outside of purchased wheels.
Yeah, that's what I meant. If you made your own wheels, how could it be determined whether the protrusions were "added" or part of the "original" wheel? The only time FIRST has a baseline to compare with is when you have purchased your wheels from an outside source.
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Unread 01-12-2003, 12:50 AM
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its a new rule, to encourage you to make your own wheels this year. we've always done it in the past since 2000, and its really worth it to take the extra 3 days and make wheels. many of you probably remember our chromed wheels last year, took us about 3 days to complete the whole thing
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Unread 01-12-2003, 02:01 AM
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Wheels are by far easier, especially now with the pre-fab gearboxes. Tank treads are not always as advantageous as they may seem. I've been on a team that used them before, it worked, it worked at a moderate speed, but it ate power like nothing else.


In a situation of a steep grade or changing terrain, a well distributed force can also act somewhat as a suspension. 2 years ago, most of the treaded robots were designed to go over the 2 x 6" platform under the bar. This was advantageous because even when the bot was begining to balance it's weight on that beam, it still had lateral force against the beam.

My personal belief for this game is that wheels are more effective than treads, a 14º grade is not too steep where treads are required and there are no obstacles to climb over.

The most power can be gained from wheels while the most traction can be gained from treads. A high-traction system will mostly only need in place when fighting for king of the hill.

The big difference between wheels and treads, the Friction does not change but Traction does. Friction doesn't care about surface area, as per nominal equations. Traction however increases as more points of a friction surface are engaged.

The big downside that I see against it for this type of competition is the forces that go into it. I'm no engineer but this is what I assume from what i've seen..
in black, surfaces that contact the ground/belt
in grey, round surface that interacts with ground/belt
in red, my opinion of how motor power is distributed.

Also note the number of moving parts. More moving parts = higher chance for failure.
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Unread 01-13-2003, 01:38 PM
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?

you cannot add material to teh wheel outside ? can u subtract material ?
or does the rule state...simply "no modification" ?
even with the 1" crappy skyway wheels, its possible to cut otu a good design on them, for traction.....
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Unread 01-16-2003, 10:45 PM
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new rule

PAGE 20, RULE M17
This rule was drafted to attempt to prevent damage to our playing field, which includes the
ramp structure, field borders, etc. Because we allow you to fabricate a wheel, it really doesn’t
make much sense for us to say:
“The outer surface of off-the-shelf wheels may be modified by removing tread material only.”
Please delete this sentence; however, now we need to address the issue of “anti-traction”
devices or anchors, i.e., devices designed to hold you firmly in one place. Anchors cannot
use metal in contact with the carpet to “stay put.” Similarly, metal traction or anchor surfaces
are not allowed on the ramp surfaces.
Add the following to Rule M17:
Anchors, i.e., devices that are deployed/used to attempt to keep one’s robot in one place and
to prevent from being moved by another robot, cannot use metal in contact with the carpet to
“stay put.” Similarly, metal traction or anchor surfaces are not allowed on the ramp or
platform.

so now you can add stuff to you wheels, or take it off, it's your pick.
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Unread 01-17-2003, 08:59 PM
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basically, all that first really wants (same thing last year, and i believe the years before) is that the robots aren't made in a way that messes up the rugs and stuff, cause then its bad for everyone who plays after... the refs normally won't bother you unless your tread is made of metal chain links or your wheel has hooks or pointy things
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Unread 01-17-2003, 10:25 PM
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Do any engineers have any rebutals to my post earlier? (With the picture of Wheels vs Treads). Because if I'm wrong on why treads are generally slower, I would like to know the real reason
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Unread 01-20-2003, 11:01 PM
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Here's my take on it:

Treads can provide more traction, but don't always.

Treads are a tricky thing to do right. (I've seen many a good throw off a tread in a match) In fact team 68 abandoned them alltogether midseason in 2001.

Treaded machines usually move slower because the differential torque required to steer them is very high (it's also pretty big for 4 wheel skid steers).

My prediction: Well designed treaded machines will dominate the ramp scene, while higly mobile wheeled machines will dominate the stacks. Oh wait really fast wheeled machines with suction cups might dominate the ramp, assuming they get there first.
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Unread 01-24-2003, 12:30 AM
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but my team, a basically rookie team, had perfectly working treads last year, our problem was with bad bearings (they popped out whenever a robot hit us, and half the time when we hit a goal) and with gearing... for some reason no one, not any of our engineers (who we love) nor our teachers (mostly physics teachers too) could help us figure out the right gear ratio for the drive train - ended up being the fastest the chip motors could put out, provided the robot weighted nothing...

on topic: the treads normally take a little extra work, but if done right, can be hell on wheels, (i mean treads).
wheels are easier, but normally have less traction

bottom line ? either works, just get something with moderate traction and ok speed, and then tinker until its good, because as long as the robots well designed (over all), an ok drive train will still murder (i mean beat in a friendly manner) most other teams
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