Gears locking during shimming

[LazzurusMan]

So my new shs 13.1 gearset arrived today, and Ive started to get eh gb shimmed and hopefully I'll have it alkl finished today. Or so I thought.

Gears are shimmed to the GB shell, and shimmed with a very small gap between each gear, but when I test to see if the gears are meshing well they seem to spin fine then get stuck/caught on something. Appears to be a problem between the bevel and spur gear. Anyone had a problem like this before?

[Davegolf]

Just in case you didn’t know:

Shim each gear individually, fully screwing the gbox case together to check for clearance / free spin.

 

Once you’ve done them all add one at a time a re screw gbox and test.

That way if you get a tight spot or meshing issue you’ll know what caused it.

 

If you get a tight spot check teeth don’t have any burrs, sometimes there are manufacturing errors.

With the bevel and pinion roll them in your fingers, some combos don’t get on.

PS it’s worth fitting the bevel only, then the motor with pinion to setup the height etc, then also power the motor to check fine tune.

[LazzurusMan]

Looks to be the teeth on the bevel gear and spur gear not meshing properly. I can actualy put the two together and hold one up, and the other will stay attached. I'm not sure if this is a production issue, or something I'm not getting right.

[Adolf Hamster]

sounds like one of the gears isn't running true.

 

surprisingly common issue, you need to figure out which gear it is (usually the idler) and how much it needs to be moved up/down (or the gears around it) to have enough clearance. look at the gap between it and the sector when spinning to see if it's moving in/out.

 

it's one of the reasons to not start with the bevel gear, as things like the idler being off mean you might be limited as to how much you can raise/lower the bevel by whilst still having sufficient clearance for the other gears.

[LazzurusMan]

59 minutes ago, Adolf Hamster said:

sounds like one of the gears isn't running true.

 

surprisingly common issue, you need to figure out which gear it is (usually the idler) and how much it needs to be moved up/down (or the gears around it) to have enough clearance. look at the gap between it and the sector when spinning to see if it's moving in/out.

 

it's one of the reasons to not start with the bevel gear, as things like the idler being off mean you might be limited as to how much you can raise/lower the bevel by whilst still having sufficient clearance for the other gears.

Not sure what you mean, but when I take the spur and bevel gears out and just mesh them together and turn them as if they are in the GB, I can see and feel at least one tight spot where the teeth don't match up well

[ak2m4]

take a pic of the inside of the gearbox shell please

[LazzurusMan]

2 minutes ago, ak2m4 said:

take a pic of the inside of the gearbox shell please

Empty or with gears? Stupid question I know but I'm at work so brain not in gear 🤣

[Adolf Hamster]

12 minutes ago, LazzurusMan said:

Not sure what you mean, but when I take the spur and bevel gears out and just mesh them together and turn them as if they are in the GB, I can see and feel at least one tight spot where the teeth don't match up well

 

I really ought to know the proper word for it, but essentially the gear can be slightly off-square compared to the shaft, so if it's running very tight to say the sector gear then at the high point it'll hit the edge and have a tight point.

 

Look at the overlap of the teeth (ie that the middle of the tooth overlaps its neighbor when viewed from the top)

[ak2m4]

2 minutes ago, LazzurusMan said:

Empty or with gears? Stupid question I know but I'm at work so brain not in gear 🤣

 empty pls

[LazzurusMan]

11 minutes ago, ak2m4 said:

 empty pls

Will do in the morning after work.

[LazzurusMan]

7 hours ago, ak2m4 said:

 empty pls

This is the GB with no gears.

 

 

Honestly the teeth on the spur and bevel gear don't seem to match/mesh very well.

[ak2m4]

on the other part of the shell is there any reinforced material ? sometimes this blocks 13:1 gears from working due to the size of the sector gear

[LazzurusMan]

This is the other side, but the problem isn't with the sector gear, cause the sector and spur gears run perfectly together. It's only when I put the bevel gear in that I get issues.

[ak2m4]

some brands of gearbox just don't like certain ratios and certain types brands of gears I've found over the years, it's why I stock both SHS and ZCI.   If you can, try the gears in another shell you might have, or if you got the gears from me then feel to send them back to me and I'll try them out.

[LazzurusMan]

5 minutes ago, ak2m4 said:

some brands of gearbox just don't like certain ratios and certain types brands of gears I've found over the years, it's why I stock both SHS and ZCI.   If you can, try the gears in another shell you might have, or if you got the gears from me then feel to send them back to me and I'll try them out.

I've already short stroked the sector gear. I'll try adjusting the shimming, and I'll try them in a spare V2 gb I've got laying about too.

[LazzurusMan]

Managed to get a video that shows what I mean a bit better. This is just the spur gear and bevel gear in the shell, no shims or anything. As you can see, the gears lock up with each other and it takes a bit of force to move them, more than should realistically be required.

[Floperator]

Have you got a correctly sized rod you can put through the bushes to see how square they are?

[Rogerborg]

Well, this suddenly became very relevant to my interests.

 

I've just been putting a set of (can you guess?) SHS 13:1 gears in, and ran into the same problem.  Or rather, it was the spur and sector not meshing correctly in my case.

 

It's not the shell, nor the shims, and the gears weren't fouling on anything but each other.  I shimmed the spur, put in the sector deliberately undershimmed, it had loads of side-to-side free play, then it hit a consistent sticky spot and rode up, losing all free play.  I ruled out everything except the gears themselves.  There were no visible flaws with the teeth.

 

I've fixed it now by scraping between the teeth on both spur and sector with a small awl, then forcing the gears back and forth past the sticky point, rinse (well, brush) and repeat.  I didn't see any significant chunks of material come out, but after a few iterations, the gears unstuck, feel fine now, and could all be properly shimmed.

 

Airsoft QC, is all I can assume.  "Upgrades", eh? 🙄

[LazzurusMan]

I haven't got an awl, but I might try and gently scrape with a hobby knife or one of my tiny files. 

 

Glad (in some ways) to know I'm not the only one, and that I'm not crazy. Hopefully now I can sort it and get the Sig back together again.

[Rogerborg]

Well, when I say "small awl", I mean the pointy thing from a Poundland precision screwdriver set.

 

Yes, I was questioning my sanity too, as I couldn't see any problems. I was convinced it must be the gears fouling on the shell, but ruled that out with a sharpie (no witness marks left), wiggling and loupe-work.  It's actually a wonder that sintered monkey metal in worn out moulds comes out as well as it does.

[LazzurusMan]

All together, shimmed and tested. Doesn't screech, hits 31/32rps, and my FPS is entirely inconsistent.

 

BUT IT LIVES.

[ak2m4]

For context I had lazz send the gears back to me for testing, not sure he mentioned this in his videos. I tried them in an e&c, lonex, and v3 JG gearbox and the spun perfectly, no issues at all, videos are up in anyone is interested.  All I can put the problem down to is either some incompatibility with certain brand of 13:1 or as @Floperator says ensure the bushings are level.  Seems like @Rogerborg has a neat solution. I wonder if its only 13's that cause the issue?