Does anybody know where we might be able to get one of those nice 3 speed dewalt xrp transmissions? Also, what’s the maximum amount of torque that these things can handle? I think it’s P/N N211313 (this is another 3 speed dewalt gearbox??), but I’m not sure.
We’ve found used Dewalts on Craig’s List before… you can usually find them real cheap without a battery or if the motor is fried, take them apart, and use the gearboxes as you need.
I have a couple I could sell you. PM me if you are interested.
More than enough to snap a hardened steel output shaft (without shock-loading). Ask me how I know…
In 2005 we used an XRP transmission with two FP motors geared down something like 10:1 or 20:1 in low gear to actuate our arm. Emperical data suggests that output torques of 500-1000in-lbs are doable. One must figure that, at a minimum, they could handle a 775-18 operating at 18V, which in low gear is around 490in-lb of output torque.
The Drill is a DW980K, although many other drill models will also work.
The XRP drills are good because they are easy to mount with the extension ring for the optional handle.
You can order parts from DewaltServiceNet
BTW, RS-775 motors will drop right into this drill with no modifications at all if you have the tools to swap the pinion gear.
Thanks. If we do go this route, I’ll send you a message. It may be after next build season starts.
We we’re looking at them for a drive system after seeing what 118 did in 2008. I understand that they never changed direction, but that they used one gearbox for the entire drive system. From that data, it doesn’t look like more than one CIM is a good idea, at stall they’re over 300 in-lbs each.
That’s really nice. I’ve been reading through the NBD whitepaper, and these look like the perfect gearboxes for an arm/lift. The slow speed can be used to raise a heavy object, the fast speed can be used to move the unloaded arm. Not backdriving and having an adjustable slip clutch is also pretty great.
We used XRP drills a number of years and in our experience they are pretty well bullet-proof. We bought brand new discontinued versions off EBay for $45 (then). We cut off the pinion gear that came with it and got an EDM shop to drill a hole in it for the correct size of the motor we planned to use. We mounted small fans close to the motor to help get the heat out of the brushes etc. The 3 speeds of the transmissions were great for prototyping. Design for the medium speed and if it turns out too slow or fast switch to the better speed. We mounted the dewalt via a standard muffler clamp around the handle mount.
We reused the drill speed controller for a variable speed reversible motor tester which is part of our test tool kit. We put an amp meter and a 40 amp circuit breaker in line with it and connected it to a standard battery connector.
Indeed. These transmissions are designed for 775-sized motors. They simply aren’t designed to handle a CIM motor, let alone two! Though empirically using a single CIM with an XRP trans seems to be fine.
This can be problematic when trying to drive a loaded arm downwards at slower rates. The anti-backdrive pins lock up the arm intermittently, causing very erratic and sometimes dangerous arm behavior.
Yet 118 ran 4 CIMs and two 775’s through one.
A bit more expensive then modifying the gearboxes yourselves, but this seems like a decent option for some teams.
Robotmarketplace’s product DeWut?!
Impressive. More so if it lasted throughout competition. Even more so if that could last in a more modern competition environment.
Like I said before (but re-worded): in my experience the output shaft is the transmission’s weak link. If we could snap an output shaft made of hardened high-grade steel with two (6V) FP motors I can only imagine on how easy it would be with four CIMs and two 775s.
I agree. I too was surprised, but I read that instead of reversing their drive motors, they turned the swerve modules around, so they never had the load of reversing the motors. Also, they have more reduction after the transmission in the swerve modules, so there’s less torque than if they direct drove the wheels That being said, I still wouldn’t be surprised if they had to limit themselves in low gear. 6 motors is a ton of power.