gearbox not pulling piston back?

Jimmy bo 186

I have a gearbox here and when i plug in the battery and pull the trigger It attemps to pull back the piston but cant. As a result, it makes a grinding noise. When i take out the spring it is able to pull the piston back. I then changed to a more powerfull motor but made no difference. I stripped the gearbox down to the bushings and everything inside is perfect.

I then noticed movement of the motor when inside the motor cage and slight movement in the gears. Do you think this is the problem? I have spent hours and hours at the gun and am considering taking it all apart once more to try and stop the movement inside the mechbox. I have fixed gearboxes before but i am unsure about how the bushings are placed. How many need to go in each side etc.

I would greatly appreciate it if you can get back to me on this.

Thanks

Inari

You basically need to shim your gearbox - shims are spacers put on the gears to ensure that they only move along the proper designed planes of movement.

There are two schools of thought - one is to shim from the spur gear; it should just clear the bottom of the gearbox shell. Then move to the Sector gear - it should just clear the bottom of the spur gear. Then you move to the final gear, the bevel gear; once again you want to make sure that is properly aligned to the spur gear.

Another method involves modifying the gearbox and shimming from the motor and bevel gear - this is more mechanically sound, but requires additional work, whereas shimming from the spur gear tends to do just fine.

There is no specific number of shims to add each side. You just want to reduce the ability of the gears to move outside of their designated plane of movement BUT! you don't want to shim it too tight either, as otherwise it will not turn.

Jimmy bo 186

Inari wrote: »

You basically need to shim your gearbox - shims are spacers put on the gears to ensure that they only move along the proper designed planes of movement.

There are two schools of thought - one is to shim from the spur gear; it should just clear the bottom of the gearbox shell. Then move to the Sector gear - it should just clear the bottom of the spur gear. Then you move to the final gear, the bevel gear; once again you want to make sure that is properly aligned to the spur gear.

Another method involves modifying the gearbox and shimming from the motor and bevel gear - this is more mechanically sound, but requires additional work, whereas shimming from the spur gear tends to do just fine.

There is no specific number of shims to add each side. You just want to reduce the ability of the gears to move outside of their designated plane of movement BUT! you don't want to shim it too tight either, as otherwise it will not turn.

Cool, Thanks alot for the quick reply. Will try to get a good video up on you tube of that.

Do you think, the fact that there was slight movement in the gears was causing the problem, considering the piston could be pulled back without the spring?

Inari

Yup. The spring gives the gears resistance, which means if there's any play (i.e. if they can move in any way outside of their ideal axis) they will move, and not mesh properly, which means they won't pull the piston back.

Just a Plinker

Check out this site great video tutorials

www.mechbox.com

Jimmy bo 186 wrote: »

I have a gearbox here and when i plug in the battery and pull the trigger It attemps to pull back the piston but cant. As a result, it makes a grinding noise. When i take out the spring it is able to pull the piston back. I then changed to a more powerfull motor but made no difference. I stripped the gearbox down to the bushings and everything inside is perfect.

I then noticed movement of the motor when inside the motor cage and slight movement in the gears. Do you think this is the problem? I have spent hours and hours at the gun and am considering taking it all apart once more to try and stop the movement inside the mechbox. I have fixed gearboxes before but i am unsure about how the bushings are placed. How many need to go in each side etc.

I would greatly appreciate it if you can get back to me on this.

Thanks

Jimmy bo 186

Just a Plinker wrote: »

Check out this site great video tutorials

www.mechbox.com

Will take a look at that now. Thanks a lot guys