Gears Tight in Gearbox

[SheriffHD]

I have  Cyma project gun that im working on. I recently got some new gears for it (13:1 SHS) without any shims in place and only the gears in the gearbox i cant get them to spin freely. I have to push hard with my fingers to get all 3 gears to rotate 360*

I cant see any bowing in the gearbox and i removed all shims to make sure nothing else was interfering. I dont know what I should do next as I dont want to start cutting away bits only to find ive cut the wrong thing. 

Any ideas?

 

[Misery]

is it a quick change spring cyma gearbox or the non quick change?

 

[SheriffHD]

is it a quick change spring cyma gearbox or the non quick change?

Its a non quick change.

Like i say theres nothing else in the gearbox while im trying to spin it other than the gears and bushings.

 

[Speedbird_666]

 gears and bushings.

Are they stock CYMA bushings or have you upgraded those too?

Have you checked each gear individually to see how they spin?

Is the GB one of those 'reinforced' types with the extra metal around the spur gear and rear of the 'box?

 

[SheriffHD]

Are they stock CYMA bushings or have you upgraded those too?

Have you checked each gear individually to see how they spin?

Is the GB one of those 'reinforced' types with the extra metal around the spur gear and rear of the 'box?

Stock Bushing, it seems the spur gear is the issue as I started on the bevel which span fine after a shim. I then moved onto the spur gear and it all seemed tight. removed all shims and was still tight but wasnt sure if it was my fat fingers not getting in to spin it well so added the sector gear all without any shims in place and I could only get the gear set to spin about 90* before something locked up and it required more forced to spin full 360*

I would think to remove material from the bushing but not sure if that would be the best call as I fear the gear would rub against the body.

and no, its not a reinforced gearbox.

 

[Misery]

its the gearboxx itself u need to file back a bit of the arch  for the gears to be free moving

View attachment 72821

 

[Skara]

Some spurs aren't 100% flat, unfortunately.

I have the same issue with a gearbox shell I bought a while ago, the spur doesn't want to spin freely.

Bevel and sector are fine.

You should also check if the bushings are parallel to the shell and to each other, the gearbox shell might be slightly warped or they haven't been installed correctly.

Also, those reinforced gearboxes are useless, there should be extra material at the front, not the back....

The marketing ideas people come up with are amazing

 

[Iceni]

You might have a warped shaft on the spur gear.

If you lightly clamp the spur in a drill by the bit that goes in the bushing. Then let the drill spin but only slowly you should be able to see if the shaft is warped or not. If it is send the gears back manufacturing defects happen.

 

[ak2m4]

post up a pic of the inside shell just to be on the safeside, if you have another shell to test the gears would be a good idea.  also post up a pic of the gears, are they legit shs?

 

[SheriffHD]

post up a pic of the inside shell just to be on the safeside, if you have another shell to test the gears would be a good idea.  also post up a pic of the gears, are they legit shs?

I'd hope so, I brought them off you lol

 

[ak2m4]

I'd hope so, I brought them off you lol

you said SHS, i sell Rocket ones ?  bent spur gear shafts can happen but I've not come across it for a long time.  the spur gear definitely isn't getting caught on the case right?

- check there's no separation between the layers of the spur gear

- check all teeth are intact, no burrs or anything like that

- do you have another shell you can test them in?

- have you got another set of gears to try?

If not send em back to me and I'll test them here, occasionally I do get customers where shs / rocket gears just don't work for one reason or another, generally we swop to a set of ZCI and that fixes the problem.  it's very rare but it happens

 

[SheriffHD]

I'll have the gearbox open later to see what they are looking like. I wouldn't bother sending them back if its something I can resolve myself but thats kind of you.

I didnt notice any separation or issues with the teeth as I inspected them before fitting them.

 

[SheriffHD]

So I finally got around to taking my gun apart and after a bit of tinkering and actually paying attention I was able to figue my issue out. 

The gears I had (Rocket not SHS i just misread the sales page) They were slightly thicker than the OEM gears and they were catching on the bushings. Thinning out the bushing on the bevel gear solved the issue and now the gears are spinning freely.

Thanks for all your suggestions :d