pic: Four Speed Three CIM Gearbox

[asid61]

Originally Posted by zinthorne

Sorry for me asking, but what is a PTO gearbox?

They're used to transfer power from the drivetrain, which usually has a lot of power to spare, to other mechanisms, usually for an endgame.
Lifting oneself in 2013 could be accomplished using all 6 cims in a drivetrain, for example.

[Ryan Dognaux]

This is really cool. If you can find the machining resources to make one I would totally do it as an off-season project. Sure it may not be the most practical thing for the competition season but you'll learn a lot while doing it. You could also design up a 2 speed variant and make that too and do a comparison - maybe even post a white paper so we can all learn about it. Good stuff!

[Cory]

Originally Posted by GeeTwo

At 3:1 per shift, it would be a massive 27:1, which could be a real game changer in some highly defensive games or games with steep ramps. Especially if you want to reserve some CIMs for manipulators!

Under what scenario would that be useful? Once you can break traction you see no benefit to moving slower, unless somehow you needed to very precisely position your robot with fine movements.

[GeeTwo]

Originally Posted by GeeTwo

At 3:1 per shift, it would be a massive 27:1, which could be a real game changer in some highly defensive games or games with steep ramps. Especially if you want to reserve some CIMs for manipulators!

Originally Posted by Cory

Under what scenario would that be useful? Once you can break traction you see no benefit to moving slower, unless somehow you needed to very precisely position your robot with fine movements.

Who says that your robot always has the same weight? I seem to recall that there was a game in which robots extended a ramp to lift their alliance partners. I also "blue skied" a robot for Ultimate Ascent which would have literally grappled its alliance partners and made a 90 point outside climb (code name Fezzik, for fans of The Princess Bride). If you wanted that same robot to also fly around the field scoring frisbees for the first hundred seconds of the match, having a multi-speed PTO transmission with a total span of 20+:1 would have been epic.

[magnets]

Originally Posted by GeeTwo

Who says that your robot always has the same weight? I seem to recall that there was a game in which robots extended a ramp to lift their alliance partners. I also "blue skied" a robot for Ultimate Ascent which would have literally grappled its alliance partners and made a 90 point outside climb (code name Fezzik, for fans of The Princess Bride). If you wanted that same robot to also fly around the field scoring frisbees for the first hundred seconds of the match, having a multi-speed PTO transmission with a total span of 20+:1 would have been epic.

I always love these hypothetical crazy gearboxes and ratios people come up with. Practical, maybe not, but definitely awesome.

Assuming your robot was geared for 18 feet per second in high gear, and 0.67 feet in low gear (a 27:1 spread), you'd need to have a 1800 lb robot (or group of robots) to take advantage of the gear ratio and never trip the breaker in a pushing match. If the robot weighed any less, you could get away with a smaller spread and never worry about tripping a breaker.

That sounds like my kind of game!!

[thatprogrammer]

Originally Posted by magnets

I always love these hypothetical crazy gearboxes and ratios people come up with. Practical, maybe not, but definitely awesome.

Assuming your robot was geared for 18 feet per second in high gear, and 0.67 feet in low gear (a 27:1 spread), you'd need to have a 1800 lb robot (or group of robots) to take advantage of the gear ratio and never trip the breaker in a pushing match. If the robot weighed any less, you could get away with a smaller spread and never worry about tripping a breaker.

That sounds like my kind of game!!

2002 meant your robot could be several hundred pounds due to how heavy the movable goals were. 71 could drag over 900 pounds that year!

[TJP123]

Originally Posted by Kevin Leonard

Ever considered taking that third and fourth position and turning it into a PTO? That wouldn't be very important in a game like 2015 whatsoever...

503 found them quite useful, so much so that we had two separate PTOs. 4 CIMs to power our can grabbers and 2 for the elevator. The drivetrain could use 2, 4, or all 6 CIMS.

[Kevin Leonard]

Originally Posted by TJP123

503 found them quite useful, so much so that we had two separate PTOs. 4 CIMs to power our can grabbers and 2 for the elevator. The drivetrain could use 2, 4, or all 6 CIMS.

I mean to be fair, there was no reason to have 6 CIMs in the drivetrain this year either. I know of a team on Einstein that was running two motors. I heard it was two Mini's at one point, but I don't recall.

[TJP123]

Originally Posted by Kevin Leonard

I mean to be fair, there was no reason to have 6 CIMs in the drivetrain this year either.

Not one reason? Hint: I just gave you one.

Don't think of it as a 6-CIM drivetrain, think of it as a 6-CIM powertrain, powering three very different motorized mechanisms in an extremely effective and efficient manner. Many ways to skin a cat.

[hectorcastillo]

Originally Posted by TJP123

503 found them quite useful, so much so that we had two separate PTOs. 4 CIMs to power our can grabbers and 2 for the elevator. The drivetrain could use 2, 4, or all 6 CIMS.

That's very interesting. I've only thought of PTOs as using all of the motors at once for one function or another. It hadn't yet crossed my mind that you could be running multiple functions simultaneously by splitting up the motors like that and being able to control these functions independently.

Although what advantages would it serve to have power coming from the same place if you could just use more motors for a different mechanism? The only reason I can think of is because there is a limit on the amount of CIMs you can use and it's hard to get that kind of power from other motors, so for climbing or stacking you'd want to be able to tap into those motors. But for example there wouldn't be much of an advantage from using a PTO to also power an intake system that could easily be powered by a smaller motor. It would actually be kind of wasteful.

[GeeTwo]

Originally Posted by hectorcastillo

Although what advantages would it serve to have power coming from the same place if you could just use more motors for a different mechanism? .... It would actually be kind of wasteful.

The ultimate FRC PTO would have six CIMs each running at a bit under 20A, each generating about 150W. A slice of this massive 900W (that's about 1.2 HP) would then be available to whatever functions the robot needed to perform, whether it was drive, lift, pickup, place, throw, can grabber, or whatever screwy function the GDC required that year. If tapping the "correct" amount of energy off of a rotating shaft and applying it to a task was easy, this would definitely be the way to go. And OBTW, if you weren't using all 900W, perhaps you could spin up a flywheel, which would allow you to draw a few hundred extra watts later when you need to "go to eleven" for a bit. Theoretically, this sort of PTO sounds like heaven for a game like Aerial Assist which involved defense, driving, shooting, and (at endgame) climbing. The devil's in the details, as always!

And, for the record, my prediction: The first FIRST team to execute this sort of PTO will join 71, 118, 254, and 1114 as one of the top five teams of all time (unless, of course, it's one of those four who do so).

[Kevin Leonard]

Originally Posted by GeeTwo

The ultimate FRC PTO would have six CIMs each running at a bit under 20A, each generating about 150W. A slice of this massive 900W (that's about 1.2 HP) would then be available to whatever functions the robot needed to perform, whether it was drive, lift, pickup, place, throw, can grabber, or whatever screwy function the GDC required that year. If tapping the "correct" amount of energy off of a rotating shaft and applying it to a task was easy, this would definitely be the way to go. And OBTW, if you weren't using all 900W, perhaps you could spin up a flywheel, which would allow you to draw a few hundred extra watts later when you need to "go to eleven" for a bit. Theoretically, this sort of PTO sounds like heaven for a game like Aerial Assist which involved defense, driving, shooting, and (at endgame) climbing. The devil's in the details, as always!

And, for the record, my prediction: The first FIRST team to execute this sort of PTO will join 71, 118, 254, and 1114 as one of the top five teams of all time (unless, of course, it's one of those four who do so).

First of all, you obviously can't make a list of the top FRC teams of all time without including 67.

Second of all, the ultimate PTO would use every motor available and just shift however many motors necessary to any function.
(However you'd have to have some crazy programming scheme or something to keep from browning out like crazy)

I also think the first team to do this won't be one of the greats; I think the first team to try it won't get picked at their event. That's insanely complicated, even for a team like 254 or 118. I would love to see someone do it successfully though. it would just be a mechanically sick robot to check out.

[GeeTwo]

Originally Posted by Kevin Leonard

the ultimate PTO would use every motor available and just shift however many motors necessary to any function.

I also think the first team to do this won't be one of the greats; I think the first team to try it won't get picked at their event.

The reason for stopping at 6 CIMS is that they are capable of efficiently turning every amp you can get through the main breaker into mechanical energy. Once you do that, any additional motors are meaningless.

And I did mean the first team to successfully execute it, not the first to attempt it.

[Knufire]

https://www.youtube.com/watch?v=h3l6Xqts4to

[The other Gabe]

Originally Posted by Lil' Lavery

What advantage(s) do you expect from having a four-speed, 3CIM gearbox over a two-speed 3CIM gearbox? A four-speed 2CIM gearbox? Heck, even a single-speed 3CIM gearbox?

Basically, why? This seems like overkill.

in 2014, a 3 CIM gearbox helped my team be the most dominant team in the PNW for the first 3 weeks (ish). no one could catch up to us, and our rams on defense rekt teams with loose ball carry. we didnt have a 4 speed though... it was just all fast, all the time