Planetary gearbox problemI

[bogcrawler]

I need some help ! I got a 1:5 planetary gearbox and a 55T motor. I bolted the motor on to the gearbox and powered up but the motor couldn't budge the gearbox, I disconnected the power and tried to turn the driveshaft but it was locked solid. I then took the motor away from the gearbox and tested it, it is perfectly ok, then I turned the driveshaft and everything in the gearbox spins ok, I tried the pinion and it too is a perfect fit, it's only when the motor and unit are bolted together everything locks up, I also slightly tightened the 4 screws holding the gearbox as I saw on a another thread that over tightening the screws could cause the problem but that I think was a Tamiya problem. I have spent ages trying to find a solution to this. It's probably something simple, but I just can't get it. I thought it was just a simple matter of bolting on the motor.
Thank you !

[aeiou]

Make sure your motor screws aren't too long, making contact with the armature.

[Tom Ivar]

You could try som spacers between the gearbox and the motor if the screws are too long.

[RiderZ]

Or just cut them down with a Drexel cutoff wheel and a fine file.

[littletoyboy]

Or maybe just use the right length screws if they are indeed to long.

[bogcrawler]

Thank you all for your suggestions, when I was bolting the part of the gearbox that fits on to the motor it was obvious the screws were too long so I used much shorter ones, the motor works fine with that plate in position, it's when I bolt on the rest of the gearbox everything locks up, when I try to move the drive there is no moving it, I can see no reason why it should be like that, the gearbox on its own is perfect, no binding, the motor driveshaft is free. I even bolted the motor pinion on to the end of an Allen key and inserted it into the gearbox and there was no binding so all the gearing is fine, it's just when its bolted together it doesn't work, driving me nuts !!!!

[OSRC]

Pinion gear might be too long when bolted to the motor and rubbing/locking up against another gear. Happens on my GRU'S with certain motors. Would explain why its only when it's bolted together.

[aeiou]

Not knowing which planetary gearbox you have, a photo or two might help. If it's the pinion or armature shaft binding against the gearbox side, you may notice the armature shaft on the end bell side being pushed out slightly when you bolt things together. Something may also be pinching the planet/sun gears, disk, etc.. Does it spin freely when you mate the two pieces together and only bind when you snug up the bolts? While I'm a fan of solving problems at the source, if this is the case, shimming may get you going in the short-term.

[bogcrawler]

Hiya all ! Problem solved thanks to a combination of your suggestions, the motor spindle was indeed a fraction too long and I cut it a tiny bit shorter and bolted everything together again, while I got a little movement it was very tight, so undid it all again and removed a flat washer from the motor end of the gearbox, although it is very thin, removing it gave me better movement but still tightish, I then backed off the long screws that bolt up the gearbox, a 1/4 turn was enough, everything worked perfectly. Hard to believe it could lock up so badly with a little extra turn on a screw !
AEIOU ! it is I would say a copy of the rc4wd disrupter planetary gearbox, got it from China, it comes with separate fixing brackets and for the price is a sturdy heavy piece of kit.
Thanks again everyone for giving me ideas to solve the problem.

[aeiou]

Nice! Glad to hear you figured it out. The rules state that you must post pics of your rig whenever a problem is solved.