Properly shimming a gearbox.

.K.A.L.I.M.A.

As the title says, how do I properly shim a gearbox. I've never had any experience when it comes to this. I've tried once and I shimmed the gear very tight (They wouldn't move side to side). I pulled the trigger and the piston went half way (Pressure started to kick in), then back a quarter, then another quarter (It should have released on the trigger pull, but it didn't), and stopped.

I'd like to know every part of my gearbox and how to maintain it, but I hate it when it comes to shimming.....

Stercus Accidit

Take all the bits out of the gearbox, put in the gears and close it, see how much play is in the axles as you push them side to side. Shim it, close it again and test again, try to get just a tiny bit of sideways movement and no more, close it tight for the final test and you should have a tiny bit of play, the gears should spin smoothly too.
Try to shim either side of the gear, and ensure that the sides of the gears don't touch each other, only the teeth. That's it, then you can put everything else back in. As gear, gearboxes and bushes all vary in dimensions there is no right number of shims to use, you just do it by trial and error.

glicster

also start with the spur gear as low as possible without it hitting the bushing of the bevel gear.and dont forget after shimming EACH gear EACH time screw the box closed.it makes a big differance on tightness.
when you have the spur and sector gears done and gearbox closed,useing a torch you can look up through the bottom of the box and see how close they are,you dont want them too close(or too far away either) so to allow for sideways movement of either gear under pressure.
and dont shim the sector too high or you risk catching on the cut off lever

.K.A.L.I.M.A.

glicster wrote: »

also start with the spur gear as low as possible without it hitting the bushing of the bevel gear.and dont forget after shimming EACH gear EACH time screw the box closed.it makes a big differance on tightness.
when you have the spur and sector gears done and gearbox closed,useing a torch you can look up through the bottom of the box and see how close they are,you dont want them too close(or too far away either) so to allow for sideways movement of either gear under pressure.
and dont shim the sector too high or you risk catching on the cut off lever

What about the Bevel gear?

glicster

.K.A.L.I.M.A. wrote: »

What about the Bevel gear?

well you dont want it too low because you want the pinion to have good contact area with it and not too high so it goes too far in.
and you want the reverse latch to have a good bit to catch on.and as stercus said just a tiny tiny bit of play on it should be fine

JFAirsofter

best advice i can give you is look it up on youtube, that where i learned about shimming

and be patient when your doing it, its a long and tidious process but its so worth it

Inari

There is the other school of thought which requires a, erm, more destructive approach - shimming from the pinion gear (since it is the only constant).

However, to do so can be tricky. You can see the method and explanation here:

https://www.youtube.com/watch?v=1F0zpkmNux4

It is certainly interesting, and gives food for thought - personally I still subscribe to the more traditional method

JFAirsofter

i've never seen or even heard of that done before, thats definately interesting man, favourite on youtube and i'll definately be tryin that myself