[jimfortytwo]

We too are using a dewalt on our arm, and it is working very well for us. Let me relate our experience, and maybe some of it might apply to your case. We have a 60" arm that takes a tetra on the far end of it, and is driven by a 6" sprocket bolted to the arm. Initially that sprocket was linked 1:6 to a small pinion on the dewalt. We discovered that we were pulling too many amps in this format, and the arm was way too fast. Additionally, it seemed like the arm would slip and catch when power was taken away-- the backdrive pins were holding, but it wasn't confidence inspiring.

To lower our speed and amp draw, we added a second 1:5 reduction. Now the large drive spocket on the arm leads to a small sprocket on an intermediate axle, which is common to a second large sprocket which is then linked by chain to our dewalt. In other words, two loops of chain as reduction between the arm and the dewalt. Now our speed is right where we want it, and we can run our motors on the 20A breakers without poping them.

We had a binding problem. We could lift fine, but things got jammed up when we tried to lower the arm. It turns out that the tension on the tight side of the chain when supporting the arm was so tight that the feed side was completely slack. When we tried to lower, this slack was causing the chain to not feed smoothly onto the small pinion, which was causing the momentary binds-- which could then be cleared by jerking the arm up and then comming back down. Every one in a while you'd hear a loud popping sound, which was the bound chain suddenly settling into the sprocket teeth.

We realised that we had actually managed to flex our intermediate 5/8" axle. After supporting this axle closer to the sprocket, and retensioning the chain, the problem has been removed.

Bear in mind, we're using two fisher price motors, reduced 5:1 _and then_ fed through a dewalt _and then_ reduced by 1:5 _and then_ reduced by 1:6. Thats a much bigger reduction that it sounds like you're dealing with, but we are perfectly happy with the arm speed of our system.

One unrelated thing to check at some point would be taking your dewalt appart and looking at the inside of the aluminum gear case assembly. We were seeing worrysome signs of wear (aluminum shavings) until we added our second reduction.