Toughbox vs KOP Toughbox Mini

[valkyrie2240]

I've been looking at the differences between a normal 12.75:1 Toughbox and the KOP 10.71:1 Toughbox Mini for my team's chassis this year. I've been looking through the quick build chassis guide to see if using the Toughbox vs the Toughbox mini would change the assembly at all. I'm specifically looking at how to mount the toughboxes. Would anyone happen to know if we would have to make any changes to the KOP chassis to mount a normal Toughbox instead of the Toughbox mini?

[Gregor]

I've been looking at the differences between a normal 12.75:1 Toughbox and the KOP 10.71:1 Toughbox Mini for my team's chassis this year. I've been looking through the quick build chassis guide to see if using the Toughbox vs the Toughbox mini would change the assembly at all. I'm specifically looking at how to mount the toughboxes. Would anyone happen to know if we would have to make any changes to the KOP chassis to mount a normal Toughbox instead of the Toughbox mini?

Any particular reason? We have quite a few Toughboxes. They weight a lot, and you can get a decent speed out of the Toughbox Mini.

[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.)

[Jon Stratis]

Your biggest concern is problem spacing with the output shaft... you'll need to make sure you get proper alignment and tension with the belts the KoP drive train has now! It may be a little trial and error, but I think those old Toughbox gearboxes had enough adjustment capability built in to make this possible.

[Trish Fisher]

The team is exploring ideas. Would using the toughbox make it harder for robots to push you around?

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?

[Christopher149]

I don't think there has ever been a restriction on gear boxes (other than with window motors)

[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.

[Shane 2429]

nope my team has been using standard tough boxes for a long time and i haven't seen anything about toughboxes being removed from available usage

also yes they do slow you down quite a bit but if you want to play defense its whatcha gonna need

also easiest way to mount tough boxes drill holes in the casing mount that t the chassis and and then use all-thread and or a piece of 1in by 1in square bar and basically bolt them together. you need to do this because the amount of torque outputed will bend the bolts holding your gearboxes in place over time

also go steel its much better to know you wont have to strip apart gearboxes in the middle of a comp

[Ether]

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.

Don't you have that backwards?

[nathan_hui]

Do I? Increasing the gear ratio means the motors turn more to get a single rotation of the output shaft, which slows down the drive, which allows more torque, which wins pushing matches while drawing more current. But I'm an EE, so what do I know?

[Jon Stratis]

Do I? Increasing the gear ratio means the motors turn more to get a single rotation of the output shaft, which slows down the drive, which allows more torque, which wins pushing matches while drawing more current. But I'm an EE, so what do I know?

It allows more torque at a higher motor speed... But your forgetting that the other robot is sitting there stalled. Stall = much, much higher current draw.

And seeing Ethers past contributions, like his recent tests on the speed controllers at Whirlpool's motor lab, I'm going to go with him on this one.

[pfreivald]

We used four 9:1 BB p80s on our Octocanum drive last year, then geared down a further 5:1 (net -- between the smaller traction wheels and a Gates belt with appropriately sized sprockets) when we got into pushing matches.

We got into lots and lots and lots and lots of pushing matches last year, and never once popped a breaker with a 45:1 reduction on four CIMs. Indeed, even with using pneumatics for the first time last year, and some extremely aggressive driving, we had better battery life than any other year thus far.

[Taylor]

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

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.

[Donut]

Do I? Increasing the gear ratio means the motors turn more to get a single rotation of the output shaft, which slows down the drive, which allows more torque, which wins pushing matches while drawing more current. But I'm an EE, so what do I know?

I think what Ether was pointing out is the part at the end about current. Increasing your gear ratio does increase motor revolutions relative to the output shaft, and increases torque. But this lowers overall current draw for the equivalent torque output, which would reduce breaker trips.

[nathan_hui]

I see. I guess you'd only see the current problem in a pushing match, or when you start flooring the accelerator. But for the purposes of the OP, extra motors (to the limit of the Toughboxes) shouldn't make a difference.

[Ether]

extra motors (to the limit of the Toughboxes) shouldn't make a difference.

Extra motors on a drivetrain make a difference when it comes to not popping breakers:

http://www.chiefdelphi.com/forums/showpost.php?p=1211448&postcount=8

[Xenozero]

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.

[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]

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.

http://team358.org/files/mechanical/FRC_DrivetrainRefTables.jpg

[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]

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 (http://www.chiefdelphi.com/media/papers/2432) 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]

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.