Toughbox vs KOP Toughbox Mini

[Chris is me]

I think the KoP drive speed is very good this year and I don't see much of a reason to go more slowly, especially with the KoP drive using relatively precise belts. It's a good balance of speed and "pushing power".

[JamesCH95]

Originally Posted by nathan_hui

Increasing the gear ratio (making the drive slower) would make it harder for someone else to push you around, but you run the risk of popping breakers.

Again, what Christopher said, though I think the PG71 was also restricted last year.

Taking a little time to read and understand this chart, and even doing some of the basic math for myself, I learned a lot about drivetrains and their limiting factors.

[Taylor]

Originally Posted by nathan_hui

Probably, since the big toughboxes were originally paired with the old KoP chassis (which is now illegal, I believe). But what do I know?

Originally Posted by Trish Fisher

Does this mean that it is illegal to use a toughbox on this year's robot? I looked through the rules and I didn't see anything saying it was illegal, where would it be?

There are no restrictions on gearboxes or aluminum.
From reading <R13> and <R19>, it appears to me that structures/gearboxes from previous years' robots are legal as long as
A. The structure/gearbox is unchanged from original purchase
OR
B. The structure/gearbox has been adapted specifically for this year's game
(which is to say if you have a piece of C-Channel from 2011, unchanged, it's legal. If you have a piece of C-Channel used on your 2011 robot and you cut it again for the 2013 robot, it's legal. If you custom-cut a piece of C-Channel for your 2011 robot and are using it unchanged from 2011, it's illegal.)
Although the motors allowed are restricted to the table in <R32>, there are no restrictions on gearboxes provided they meet <R16> and <R19>

[FrankJ]

If your are stalled (0 RPM) the gear ratio has no effect on motor current. You will have a higher pushing force available with the higher ratio. (Newton will insist that if you are not accelerating the net force between the robots is 0). Other wise for a given output torque a higher (numerical) reduction will have the motor spinning faster at a lower torque therefore less current.

[Xenozero]

Originally Posted by nathan_hui

Probably, since the big toughboxes were originally paired with the old KoP chassis (which is now illegal, I believe). But what do I know? I suspect you could, but do the math (you need to make sure that the output shaft of the toughbox doesn't interfere with the wheels, and that's pretty much it.)

hey, i would like to know where you found out that the old kop chassis is illegal, would you mind showing me where it says it? my team was thinking about using an old channel that we had lying around the shop.

[FrankJ]

There is a section in the rules about reusing KOP from previous years. For the channels you basically have to account for the cost in the bill of materials.

It also has not to have been "modified" before kickoff. It is up to your GP to decide just what that means.

[nathan_hui]

The old KoP chassis will not fit the frame perimter rules. COTS materials from the KoP chassis are still legal, just not the entire kit.

And Ether, thank you for clearing up my confusion. I believe I understand the relationship between motors, torque, and current a lot better now.

[Ether]

Originally Posted by nathan_hui

And Ether, thank you for clearing up my confusion. I believe I understand the relationship between motors, torque, and current a lot better now.

You are most welcome.

If you haven't seen it yet, here's a little motor calculator I wrote a while back that may give you further insight.

[Chris is me]

The chart James posted is a GREAT introduction to drive design, and I recommend everyone read it. That said, if you don't plan on continuous pushing, you can safely bring a single speed into the 10-13 feet per second range without too many problems. Just remember the faster you gear, the less versatile you are in terms of pushing.

[Donut]

Originally Posted by Chris is me

That said, if you don't plan on continuous pushing, you can safely bring a single speed into the 10-13 feet per second range without too many problems. Just remember the faster you gear, the less versatile you are in terms of pushing.

I'll second this with some anecdotal experience. Back in 2008 (Overdrive) we geared a 4 CIM single speed drivetrain for 13.5 fps. We did not pop a breaker once throughout competition but you will notice that at high speeds like this your motors run quite a bit hotter.

Nothing substitutes doing the math if you're uncertain or want to try something unconventional. In 2009 we ran our drivetrain on 2 Banebots RS550 motors because the math worked out.