AOSC Forum Archive

Hey all so I am currently working on a DMR project using a CA AUG. I know everyone and their grandma wants to have a DMR, and I gave up on my last DMR project which was an M16A4 because I decided that I didn't like the platform. It was to heavy and too long. :/ Anyway on the to heart of the issue. After assembling my gearbox I go to test it and it pulls back the spring but it wont release it. Once it pulls the spring all the way back I start hearing a grinding noise from the motor. There doesn't appear to be any damage to the pinion gear or bevel gear, so I'm assuming the grinding could be coming from inside the motor. Anyway here is the list of parts that I currently have in the gun:

CA stock piston
Systema piston head
Matrix M140 spring
CA stock gears
CA stock motor
Ball bearing bushings

That's the important stuff that I can think of off the top of my head. Anyway I'm using the stock CA motor and gears because I was told that they should be able to handle the M140 spring no problem, if you guys think otherwise feel free to share. Anyway I could really use any input you guys can give also if you need more details on anything just let me know! Also thanks again for your help in advance!

Have you opened the gearbox back up? It could be a motor height issue... Or, that piston might already be toast. I don't have a lot of experience with CA pistons in DMR builds.... But I don't really hear of them being used often. Did it have metal teeth?

Yes I have opened up the GB several times. I have checked to make sure that the piston is on the rails and that everything is lining up correctly. The piston has one metal tooth on the end, like i said before or tried to say was that the piston and spring are pulled back but are not released to finish the cycle. I'm curios if the motor has enough strength to to pull it all the way back and finish the cycle.

What battery are you using?

The grinding sound you are talking about has me worried, I think your motor might be dead.

Do you have bearings or a spacer on the piston head and spring guide? It might be that the spring is too large.

I have bearings on the spring guide, also I'm using an 8.4 just to test the gun I'm planning on upgrading very soon

The 8.4v could be the issue...

Is it a stripping sound, or is it just like the motor is vibrating or clicking because its locked up

Its more of a stripping noise fro m inside the motor. Also it appears that there is no damage to the bevel or pinion gear.

Sounds like your motor is dead. Could also be the pinion slipping, but that is usually a very loud screech. Can you see if the motor sparks much when it gets stuck? I don't know how open your pistol grip may or may not be.

Its a V3 gearbox and its an AUG so there is no pistol grip. Any way i believe the motor is dead because i remember hearing a spark and seeing a puff of smoke, i thought it was just shorting from the solder i just used on the connections. I tested it after this incident tough and it apparently worked fine, separate from the GB it works fine

Yep, your motor is dead. It's annoying because it does seem to work fine outside of the gearbox, but once it's actually got a load, it won't do anything but make that grinding noise.

Dang...well ok easy enough to fix I guess

I'd go ahead and upgrade your wiring to handle a bigger battery while you're at it

Well the stock CA wiring doesn't seem like bad stuff, but I do have some 18 awg laying around that I can use if i do need to replace it.

Check your gears, I just deal t with this for an AK, the sector gear was stripped. Half its teeth were missing, but the piston was fine