Nothing But Dewalts Issue

[phrontist]

We have been implementing the shifting transmissions described in the seemingly very popular "Nothing But DeWalt's" whitepaper. While some of the instructions are a bit ambiguous (I'm a programmer, so I'm just passing this on), we've had no issues until now. Following the instructions to increase the bore size of the "carrier sun gear" (the one which attaches to the output shaft of the CIM) we sent said part to a machine shop (we didn't trust ourselves to do it, as the metal is so thin after this operation is completed). One of them came back just fine, but on the other the small portion of the sun carrier gear (what I suppose is the "sun") came clean off when the machinists tried to machine it. We're going to run the other one some time this week and see if it too fails, and we've ordered replacement parts to give it another go.

Has anyone else had this issue?

[bombadier337]

Our four went perfectly, though our machinist broke several bits trying to get through the gear (it's extremely hard stuff). I will once you get them on though, they really are awesome. We probably won't shift because the work so darn well in first, we don't need to.

[Joe Johnson]

Thanks for pointing this problem out.

This is one of the trickiest parts to make.

The part is hard and the wall that is left is very thin*. The machinist needs to take very small cuts with a carbide boring bar or (my perference) you need to find a good wire EDM source.

Joe J.

*in fact it was so thin, there is no engineer I trust that says it should work, I myself doubted it would hold up, but thankfully, testing is the ultimate authority.

[sanddrag]

Rather than creating a new thread, I'll post here. We are using a fisher price and Dewalt tranny. Is it backdriveable from the factory? If not, how do we make it backdriveable? Does doing so have any bad event on robustness or anything?

[Joe Johnson]

Originally Posted by sanddrag

Rather than creating a new thread, I'll post here. We are using a fisher price and Dewalt tranny. Is it backdriveable from the factory? If not, how do we make it backdriveable? Does doing so have any bad event on robustness or anything?

If you leave the 5 rollers (or any 1 of the 5) in the front end of the transmission, it will not be backdriveable.

I have had an experience where the outside ring of the transmission cracked and the no-backdrive feature failed. Notice it is not the RING GEAR that cracked but a special ring made to provide the no-back feature required for a keyless chuck. The transmission still worked, it just did not remain in place after power failure.

It was definitely a high stress application and it only failed once (and I think that Dewalt subsequently changed the design of the ring to reduce a stress riser in the part -- if memory serve me well), but it did fail.

It can cause your feedback loops to go into fits if you leave them in, especially with large arms that are not well counter balanced.

Bottom Line: if I can, I take them out.

Joe J.

[groves]

Originally Posted by Joe Johnson

Thanks for pointing this problem out.

This is one of the trickiest parts to make.

The part is hard and the wall that is left is very thin*. The machinist needs to take very small cuts with a carbide boring bar or (my perference) you need to find a good wire EDM source.

Joe J.

*in fact it was so thin, there is no engineer I trust that says it should work, I myself doubted it would hold up, but thankfully, testing is the ultimate authority.

This is what we do. we have this cut and we remove the planets and the four smaller holes go on those little shafts that the planets had fit to. plus if you mess up this piece you can just cut another one. we have had no problems with this mount (on eight drive platforms) at all! now as far as machining Dr. Johnson is correct these should be cut with a wire EDM or a water cutter works for these disks.

[Richard Wallace]

Originally Posted by Joe Johnson

If you leave the 5 rollers (or any 1 of the 5) in the front end of the transmission, it will not be backdriveable....

It can cause your feedback loops to go into fits if you leave them in, especially with large arms that are not well counter balanced.

Bottom Line: if I can, I take them out.

Joe J.

931 experienced this problem using the DeWalt transmission with an FP motor to lift an arm last year. With the anti-backdrive rollers in the arm was stable while raising and erratic while lowering. Removing the anti-backdrive rollers cleared the problem.