Gearbox Locking Down

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sgtryan
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Gearbox Locking Down

Post by sgtryan » Tue Dec 23, 2014 6:06 pm

I've been using the same setup for over a year now, and last week my M14's gearbox decided to lock down and has been doing so ever since. After tweaking with the gearbox I can usually get anywhere from 5 to 30 shots off and then it will lock down again. I changed pistons, removed the ball bearings from the piston, re-shimmed, re-lubed, and it still would lock down. But i changed the spring from a Prometheus M135 to a Guarder SP120 and so far it hasn't locked down. The spring seems to have a slight curve in it, but I didn't think this would lock it down. I figure it has to be either the spring, spring guide, or motor issue. I just don't see how I can get some shots off before it locks down. The motor seemed to be making a weird noise before all this happened, and I can smell a sort of burning when engaging full auto for a long period of time. This has all happened since I let it sit for about 6 months while I was in school and didn't know if the spring and motor just happened to be failing, and need to be replaced. As of now I believe it must have been the spring locking it down. I would really like to run the M135, but I don't want this to happen again. I never had any problems running this setup before, so any help is appreciated, and I can take pictures or videos if needed.

AGM M14
Guarder V2 Gears
Guarder V7 spring guide with ball bearings (tabs grinded thinner so it would fit in the gearbox)
King Arms M14 tappet plate
Guarder Piston Head (recently removed 2nd tooth and removed ball bearings)
Added a rubber washer to fix AOE (done after first lock down, lock downs continued to occur)
Guarder Air nozzle
Matrix Magnum motor (has been sounding a little different, and is beginning to smell)
Prometheus M135 spring (removed and replaced with Guarder SP120, so far it hasn't locked down again)

My goal is to have a sort of DMR build, but still have the ability to have full auto.

So has anyone ever had a spring wear to wear it locks down the gearbox? Or maybe was it the spring guide misaligning and I happened to fix it installing the second spring? And does the motor sound like it may need replacing soon?

Sorry for such a long post, I'm just trying to be as detailed as possible so I can figure this out and get it running so I can install a rhop.
- The Citadel, November Company, Class of 2017

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sgtryan
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Re: Gearbox Locking Down

Post by sgtryan » Wed Dec 24, 2014 6:18 pm

Update: so after around 500 rounds the gearbox locked up again, so I'm ruling out the spring. I'm going to take a video soon to help figure out the problem
- The Citadel, November Company, Class of 2017

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Re: Gearbox Locking Down

Post by Star_folder » Fri Dec 26, 2014 8:18 am

It's most likely the motor going bad. I would consider a replacement.
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sgtryan
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Re: Gearbox Locking Down

Post by sgtryan » Sat Dec 27, 2014 1:19 pm

So I have narrowed it down to two things. Either the motor is bad, or it was the spring that deals with the motor height. I forgot to use the stock spring when I installed my new matrix motor after the old one burned up (mosfet went bad I believe). The spring that came with the new motor was just a bit longer and thicker than the original, putting strain on the housing and gears until it locked down. The only other possibility is just the motor has gone bad, which didn't seem right because when I removed the motor and ran it without anything attacked to it, it ran fine. What I have right now is the housing of the old burnt matrix motor mixed with the insides being the stock motor, creating a Frankentorque. So far it works great, and is a bit overkill for what I need, but its getting the job done. I may try to switch back to the matrix motor one day, but for now I'm going to use the Frankentorque due to the increased trigger response. The matrix motor however, is far superior in rof. To anyone who may want to use a matrix magnum short motor in a TM clone M14, here are some pointers:
1: The screws on the motor are too thick on the end and must be dremeled or ground down so they fit.
2: Use the stock motor spring as the matrix one is longer and thicker
3: Overall it is a great motor with an even balance in rof and torque
4: The frakentorque was really easy to make, but is really made to pull heavy springs
- The Citadel, November Company, Class of 2017

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Re: Gearbox Locking Down

Post by Dominum » Thu Jan 08, 2015 8:34 am

I'll put money on the motor being mounted too high. What battery have you been using through all of this? Have you been able to manually cycle the gearbox immediately following a "lock up"?
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sgtryan
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Re: Gearbox Locking Down

Post by sgtryan » Sun Jan 11, 2015 12:39 am

I'm using a 10.8v battery. I never had it lock up with the Franken torque motor, and it never locked up on the first matrix motor I had. And what usually happens with the new matrix is the gears seem to be sitting on the motor when it locks up and when I remove the motor, the gears then move a bit and sit on the anti reversal latch. I can then reset the gearbox by moving the latch out of the way and i can move the gears just fine. After reset I can put the other motor in and it works fine. It may have to do with the pinion gear because one half of it looks like it has a little damage to the teeth, but the other half looks brand new. It's weird because it's like little chucks are missing on the one side, but not worn down at all.but it could be due to motor height or something like that. I'm taking a break for now with school starting back up so I won't get to work on it til summer, but the first thing I'll do is replace that pinion gear and see what happens. I'll probably go ahead and buy a 11.1v lipo, and maybe a new print as the prometheus one is beginning to lose its weird coating, and I don't want that stuff in the gearbox.
- The Citadel, November Company, Class of 2017

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