Gearbox jamming

[Cheeky vimto]

I've upgraded my EBB GR16 gearbox and found after a few shots it would jam up. Taking the gearbox out shows it always jams with the spring pulled back under tension. A little history on what I've changed;

 

- Disabled EBB by changing cylinder to SHS ported.

- Cut off 2 teeth on piston for AOE

- changed cylinder head for a red SHS double o-ring

- installed 70D sorbo pad

- Changed spring guide for one with a bearing

- Changed gears for SHS 13:1

- Changed to 8mm bearings

- Shimmed gears

- Installed mosfet

- Changed motor to Lonex A1+

 

 

I've managed to open the gearbox and the first thing I've noticed is the end of the spring guide has unscrewed itself;

 

Closer inspection shows as it's all come loose the washer covering the ball bearings rattled around and the spring has damaged the bearing runner, making it useless. Could this cause the whole thing to jam though? I still have the stock spring guide, I'll try it with that in it.

[Cheeky vimto]

It's not jamming now but it's screeching like a mofo..

[Hibernator]

Looks like your anti-reverse latch is in the wrong place. I'm assuming you move it back under the bevel gear when you reassemble? Or is it a special one to release spring tension?

 

Screetching is usually motor height too low.

[Spatch]

Screeching is motor height, your anti reverse latch looks to be in backwards and you seem to have jammed the rotating washer from your spring guide into your spring making it pointless and I'm trying to work out what exactly is sitting inside your spring behind the piston?

[straffham]

Screeching is motor height, your anti reverse latch looks to be in backwards and you seem to have jammed the rotating washer from your spring guide into your spring making it pointless and I'm trying to work out what exactly is sitting inside your spring behind the piston?

From the OP the bit inside the spring appears to be the front part of the spring guide which has come unscrewed from the rear.

 

The screeching does indeed sound motor height related, unless a ball bearing or something else is floating around the GB, or maybe piston stripped caused by jamming?

[Unrustle_Thine_Jimmies]

Screeching is either bevel-Pinion shimming related,or a bearing part has fallen into the geartrain- Clean out the GB fully,any metal shavings in grease. My personal method for shimming(With M4s) Is to first install the motor and bevel only-I have a custom M4 pistol grip just for bevel-pinion shimming,It's a ABS plastic Marui grip- ABS plastic since it's less liable to have tolerance errors from casting. It also has a window cut out for viewing motor meshing.

 

Anyway,I put the whole thing together. Then move use one of the holes in the shell to check bevel movement. I allow 1mm-1.5mm of up/down movement and 2mm max for side to side movement. Too much side to side will mean poor meshing,too little will mean screeching. It's all trial and error after that. Take off one half,add or remove shims,check alignment with pinion. I hope I've made my self understandable I got all of this from AirsoftMechanics, a video called 'Shut up Gears!' and A shimming guide by 'kalashnikob1'

 

Spring guides with bearings love to come apart. I always loctite the threading to keep it together. AR latch is out of place but I assume it's because you've released it from the bevel.

[Cheeky vimto]

Thanks for the responses. I kept firing it last night while it was screeching and then took it apart. I think I found out what I did wrong. when I installed the 70D sorbo I simply glued it to the pad on the cylinder head. This knocked the AOE well out. The teeth on the piston were worn quiet badly. I think the noise was coming from the gears sliding past the teeth.

 

The washer in the spring was from the spring guide that came loose. It was a guide off ebay, just a cheap one. I guess the end cap wasn't thread locked on. I just stuck the original one back in it.

 

The anti reverse latch has two arms on it, it's weird. It'll only go on one way and if it were on wrong it wouldn't shoot all together.

 

Here's what I've done this morning;

 

- Took the original rubber off the cylinder head and attached the sorbo back on.

- followed a different guide for AOE

- reshimmed it

- bought a new piston ( and piston head as I couldn't get the other one off)

- greased everything

 

It seems to be firing fine again. One of the screws that clamp the GB together was stripped at the head so I'm going to get another screw from work before proper testing it out.

 

To me it looks like all this started from being lazy with the sorbo and not checking the spring guide. Live and learn I guess!

[Cheeky vimto]

Took me awhile but I found a picture of the anti reverse latch;

 

 

 

Link;

http://www.airrattle.com/G-G-Top-Tech-Anti-Reversal-Latch-for-Metal-Gearbox-p/g-10-082.htm