This year my team has been considering the power take off option for the WCP gearbox this year if there would be an application where it would be useful, and there was one thing we could not find out about it. Does it take away from you ability to shift from low to high gear? Or do you keep the ability shift?
If you add the pto you can still shift into low or high gear, when your climbing/hanging the wheels will still spin. So please take that into account, if you want to disengage the wheels you need to use a 3 pos cylinder.
Just looking at how it’s supposed to work, you either have to remove a speed from your shifter or run the drivetrain while the PTO is running. 254 did that in 2013, but IIRC they later recommended not to do it.
[STRIKE]Plan on needing to remove a speed from your gearbox.[/STRIKE] 3 position cylinders exist I guess.
That being said, with the new 30t dog gear they have, you could probably make your own dual-speed shifter/PTO if you have a manual mill.
With the vast array and unrestricted quantities of high power motors now available in FRC, I’m struggling to imagine cases where PTOs are still the best option. Back when there were far fewer high powered motors and their quantities were limited, it made sense for your drivetrain CIMs to pull double duty. In 2016, teams had access to up to 6 CIMs and there were no rules restrictions placed on the quantity of 775 Pros or MiniCIMs used, so needing to hunt for that additional mechanism power from your drivetrain seems far less rewarding.
Personally, I have found that with the right planning, a PTO lets you add endgame mechanisms (i.e. climbing) with less space. For most teams, however, I agree that a PTO is an unnecessary expense.
Good point. Once you take into account the PTO, pancake cylinder and power transmission method to the thing you want to rotate you can probably have a custom gearbox or VP with a 775pro or two for the same weight.
Main advantage of the PTO would be if you identified that you needed to do a task extremely quickly( if you had a 6CIM drivetrain having another 6 775pros( also at this point a PTO is lighter) for a climber/blah/endgame etc… would probably end up being a little taxing on PDP slots available. But if you plan well you can get superior packaging, especially if you don’t have the capability to manufacture custom gearboxes( for smaller motors like 775’s).
As Anand said, if you plan your robot well you can have the PTO take up very little space.
I agree. For 1.6 lbs (plus transmissions and electronics…let’s say ~3 lbs total) you can have (2) 775pros generate enough mechanical power to lift a full-weight robot with battery and bumpers vertically at ~3.5 ft/sec (neglecting losses). That’s crazy fast, and it gets faster as you add more motors for <1.5 lbs a pop.
You very well may be able to get it lighter/smaller using a PTO, but the coupling between mechanisms means both the drive and the PTO’d mechanism are going have additional design constraints that need to be satisfied (read: less room to adapt if you need to change something down the line).
Can give a source/part number/etc on that 3 pos cylinder? A PTO that still drives the wheels is really a non-starter…
Well, there are only 16 breaker spots on the PDP. That is one reason to use a PTO. I know some teams are right up to the max of breaker spots.
6 motor drive leaves 10 spots for other stuff. Sometimes that other stuff uses more than 1 motors.
Right at 16 this year!..
You can use the FabCo one: P3D2-0.250/0.250-TFM
or the Bimba Version: FOP-040.250/0.250-LMT