DeWALT Transmission After Action Report

[CyberWolf_22]

Team 647 the Cyber Wolf Corps is asking for any team that used the DeWALT Transmissions in this year's game, or prototyped with them, to post any modifications they made to the Transmissions, any problems you had making the transmissions or reviews of how they performed for you. With this information we going to release a sequel to "Nothing but DeWALTS" that will include example of other teams modification to the Transmissions.

I have started a forum on our website dedicated to this After Action Report and would like for all the suggestions and responses to be placed here.

The forum is open so that anyone can post on it but it would be helpful for everyone to register on the website before they post.

We are hoping that these transmissions will become the standard of many teams and allow them to build a cheap transmission that can be easily modified in several ways to do many different tasks.

[Kevin Sevcik]

I'll post in both places. We've had good luck with the FP DeWalts with one modification. A .1250-.1245 hole in the pinion makes for an incredibly hard press fit on the FP shaft. We bent several FP shafts trying to get the pinion on. We even had a spectacularly buckled shaft from the LSR machine shop trying to press one on. Our solution was to move up to a .1255 reamer, which makes for a much easier press fit that's still plenty tight, even running 2 FPs back to back.

Second, we dremel modified the front plate to make some slots for a little airflow since the FP sucks air from the front. The trick is getting the slots close enough to the outer edge that they clear the body of the motor.

Oh yeah. I'll post the details of running FPs back to back if the Killer Bees don't show up and take credit for their idea.

[Joe P]

Originally Posted by Kevin Sevcik

I'll post in both places. We've had good luck with the FP DeWalts with one modification. A .1250-.1245 hole in the pinion makes for an incredibly hard press fit on the FP shaft. We bent several FP shafts trying to get the pinion on. We even had a spectacularly buckled shaft from the LSR machine shop trying to press one on. Our solution was to move up to a .1255 reamer, which makes for a much easier press fit that's still plenty tight, even running 2 FPs back to back.

Second, we dremel modified the front plate to make some slots for a little airflow since the FP sucks air from the front. The trick is getting the slots close enough to the outer edge that they clear the body of the motor.

Oh yeah. I'll post the details of running FPs back to back if the Killer Bees don't show up and take credit for their idea.

Kevin,
I agree with you that the hole on the pinion is a little tight. The first one that I tried to press on bent the Fisher Price motor shaft also. The second pinion gear that I pressed on the FP shaft went on fine using a little different method, but I do agree that a .1255 inch hole would make a better press on fit.

Joe P

[Richard Wallace]

931 built two NBD units using 2004 FP motors and 10-tooth #35 sprockets, following the white paper recipe almost exactly. We did adjust the pinion hole diameter slightly to get an easier press fit. Based on gage pin tests I think we ended up with about 0.1255".

One NBD-FP is on our robot actuating the arm pivot chain, the other is a spare that we have not needed yet. Arm radius measured sprocket-to-hook is about 4 ft. Sprocket reduction is two stages for 36:1 and then the XRP gearbox in low. Motor current measurements while lifting a vision tetra indicate less than 25A average draw [note: motor current is discontinuous with instantaneous peaks to about 45A, chopped at Victor modulation frequency], and our PWM code limits the average motor voltage to about 9V max. So far no problems, but we did have to remove the anti-backdrive pins to permit stable lowering; having the pins out makes our arm operator much happier while capping.

I'll report again after the championship.

[Andy A.]

This thread gives a good look at what 95 did with an XRP.

The exact details of the gear ratios escape me, but I can try to flush out any details that are unclear if someone wants to ask.

-Andy A.

[Andy Brockway]

Team 716 built this in the off-season but did not run in 2005. We have several hours on a pair of them used in a defensive robot in practice.

Here

[Mike Martus]

Chief Delphi uses NBD on as many motors as possible. After two seasons we have had only one failure and that was on last years robot after three additional competitions one set of pins failed to lock out. Still worked but slipped.

This year we have the 4 chips, 2 FP's with NBD. We are also using the Hubs as idlers and mounts for the pots and encoders.

Stop by the 47 pit at the Championship and take a look at our applications. They have made our robot very dependable. Especially shifting "On the fly" with a foot activated servo.

[ZACH P.]

I used two DeWalt XRP transmissions to create a set of two dual-CIM transmissions. The CIMs each have a 16 tooth gear drives a 35 tooth gear. The 35T gear is on a shaft that inputs to the XRP transmission. I used the secondary stage sun gear as the input. But to drive it I did not enlarge the hole and press it on a shaft. Instead, I modified a shaft collar with notches around the circumference to drive the pins on the back of the sun gear. The shaft collar attaches to the shaft and worked beautifully. Thus no high-cost EMDing needed.
The only problem I had was with the output sprocket. The sprocket was attached by threading the bore and screwing it on the transmission output with a washer and left-hand screw to top it off. Once, the chain was stuck during a match and I continued to drive. The transmission actually stripped the threads from the inside of the sprocket. It was both devastating and amazing.