View Full Version : Double Eagle gearbox questions

12-12-2014, 02:01 PM
I've had some failures by the double eagle gearboxes recently, and wanted to compare notes.

First, one gearbox seems to have stripped itself (or otherwise lost its gear meshing) such that the gear trying to pull back the action just shakes, and some gear further up the gearbox chain keeps slipping (with a nasty sound.) I've tried inspecting the gears through the plastic, but it's kind-of fuzzy, and there's some lubricant gunk in the way, and I can't see anything obviously broken. Yet, it doesn't work. Has anyone else seen this, or is it uncommon?

Second, when battery powered (11.1V LiPo, charged, about 11.4V) the gearbox motors fail to actually pull the action completely and stall, using a 50%-60% PWM duty cycle. Meanwhile, when using a 11V/5A power supply (that drops voltage for over-current) and the same duty cycle it works fine. It also works fine when using 6V voltage and no PWM. The power supply and the battery join at the same power entry plug, so there's no difference in wiring (actually, the power supply has longer/thinner wires to that point.) The battery is rated 20C and can run fourteen MX-64 servos just fine.
The failure acts like a stall of the motor -- nothing turns. Touching 6V +/- straight to the motor will make it turn past the stalling point.
What am I missing here; why is the battery different from the power supply?

12-12-2014, 10:22 PM
The second question has an answer: I have wired my feed/un-jammer to switch 1, and fire to switch 2, on the Onyx Fire board.
However, I wrote the registers to set the duty cycle to 25% on switch 2, and 50% on switch 1, reverse from what I intended.
An oscilloscope quickly showed me what the problem was; I should have hooked it up earlier :-)

First question is still outstanding: How durable are these gear boxes, really?

12-14-2014, 07:28 PM
First question is still outstanding: How durable are these gear boxes, really?

From what I have seen, not very. I have broken them just by running them too fast (11v). I remember stripping a gear on 1 or 2 of them doing that.

12-15-2014, 10:30 AM
Thanks! At least that validates my experience :-)