official dewalt thread

Technical Technical Discussion
1

There are many threads about dewalts and yes i have read through most of them. There are still a few questions unanswered about them. How do you increase the shaft length on the dewalts. Is there any better method of shifting available. How to securely mount them. Can this mount work? :

http://www.teamdelta.com/products/prod5.htm

Is there anything that needs to be reinforced inside the actual transmission? Should you use 4 single cim dewalts on the drivetrain or 2 dual cim dewalts? Is there anyone who could kindly put together of a video of assembling the dewalts with all the necessary modifications. What are the most important mods not mentioned in the white paper?

Thank-you CD

2

Tough one… depends on the application. Supershifters get the nod for durability and reliability, but Dewalts are much cheaper. Personally, I think if you do something, you should do it right. Andymark all the way.

By the way, that wouldn’t be a bad company motto for Andymark.

3

You have to go all out and make sure your drive is your best constructed part of your bot, or you won’t be able to use your appendages, so don’t go cheap. AndyMark Supershifters all the way.

4

Best Constructed is a relative term. I have seen teams be successful with both DeWALTs’ and AndyMarks’. There are many cases where price does not indicated quality. The major point in this argument for me is if you want an out of the box solution or something that you need to modify in order to make work.

I recommend going with the solution that fits your team’s requirements after weighing the trade offs. *cost, *time, * Form factor, *accessibility, *performance, etc.

Each team has their own requirements which will determine which solution will work for them. Even as the leader for Team DeWALT next year we will be looking at the game and what our strategy is before we decide on our transmission/ drivebase. AndyMark and DeWALT transmissions are both on the table for us.

5

You can go to this thread on CD, post 14, on our mods for the DeWalt transmission, supplementing Joe Johnsons NBD white paper.

We turn down a 3/4 steel shaft to 3/8, leaving a 1 inch long full diameter, which we thread internally onto the threaded end of the DeWalt tranny. It is pinned with a 1/8 hardened pin, retained with safety wire, to prevent it from loosening. fI have some pics that I can EMail to you, if you want. The mount consists of 4 plates, and one base plate. Plate 1 supports the end of the shaft extension, Plate 2 locks the boss of the DeWalt housing, plate 3 accepts the spacer ring and 4 screws to retain the transmission and adapt the CIM, and plate 4 supports the end of the CIM motor. We remove the anti-backdrive pins, clutch mechanism and adjustment ring, as well as speed shifter springs.

6

From Teched3

"Just to clarify, Buzz has been using DeWalts with a single CIM for the main drive for three seasons now, without any failure of motors or transmissions. However, we made modifications to the Joe Johnson NBD white paper to arrest certain concerns we had with the initial NBD design recommendations.

1- We do not cantilever the output sprocket/shaft, but support the output shaft on the outboard end with an additional bearing.

2- We fasten the output shaft to the end of the original transmission output shaft with 1/2-20 thread cross drilled and retained with a 1/8 hardened pin. We use the LH chuck retaining screw installed in the DeWalt output shaft, cut off flush to fill the void, so you won’t break the carbide drill as it comes through the inner wall.

3- Where the 3rd stage is removed from the DeWalt, we insert an alumininum spacer ring against the transmission shoulder that acts as a depth spacer as well as to maintain the transmission/motor shaft on the drive axis.

4- We turn down the output shaft of the CIM to .250, and bore out the sun gear to .2505 for a sliding fit onto the CIM output shaft. The length of this reduced shaft diameter should be equal to, or slightly longer, (for clearance) than the length of the sun gear.

5- We machine the “top hat” of mild steel, index four 5-40 tap holes to match the pin locations of the sun gear, and tap for 5-40 FH socket screws. We also broach a 2mm keyway in the 5/16 bore of the top hat to match the 2mm key on the CIM shaft, and key it. We also cross drill (1/8) the top hat/CIM shaft and insert a 1/8 roll or tension pin.

6- We clearance drill and countersink the sun gear with a carbide 82 degree #2 centerdrill (5/16 OD, 1/8 point) and then drill the four holes out with a #30 (.128) cobalt or carbide drill to provide clearance for the #5 screws.

7- We add a stiffening 1/8 x 1 3/4 tension pin to the shifter rod to prevent the 1/16" shofter rod from bending.

We are planning to experiment with a 2 CIM adaptation to the above to reduce the amp draw of the single CIM setup, which limited our “gearing up” the drive for speed this season for Overdrive. The only tradeoff is the weight added for the CIMs and adapter ot mount them. Based on the weight of the robot, friction coefficient of the wheels, and amperage available to power the motors, additional motors for the drive only help to reduce the amperage drawn to the motors. In other words, if you don’t trip the breakers, and the wheels slip on the carpet, more motors won’t equate to more push.

I have also included some pictures of the DeWalts taken after a season of two regionals, lots of shifting, two tough after-season Invitationals, and demos to elementary school groups. They are tough, light, cheap, and easy to shift. Everyone always asks how we get so much on our robot. DeWalts go a long way to lightening for more capability in other areas of the robot. PM me if you have any questions.

Looks like the pics didn’t attach, so PM me with your regular EMail address and I will send them to you if you want to look at them"