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G11 Spur Gear Removal to Access Gearbox

 

I've been chasing down some periodic resistance in my 2017 G11 drivetrain. I think I may have isolated it to the gearbox, so I'd like to remove it and pop it open to see if I can tell if there are problems in there. In order to remove the gearbox I first need to pull the spur gear off of the shaft, but so far I have been unsuccessful.

Questions I haven't been able to find answers to from my searching so far:
  1. Are there any disassembly guides for recent G11s that cover the spur gears and gearbox?
  2. Anyone know the exact allen key size to use with the set screw? In my kit, 0.05" was the largest SAE size that would fit, but it did not feel as snug as I would expect. 1/16" is too large. (Similar story for metric; 1.3mm fit but poorly; 1.5mm is too large) When I applied enough torque with the 0.05" it skipped a step...I don't want to strip it out.
  3. Any other hints on how to remove this spur gear? Do I need a gear puller or anything else?
Thanks in advance! Some photos below to illustrate what I'm talking about.

Gear on the left is what I'm trying to remove. The shaft for that gear is shared with the gearbox that is on the other side of the machined plate.


The stubborn set screw with unknown hex key size.
 

Hi Brett,

Clearly you have a modern Tucked Motor G11.? Earlier direct drive version G11 (I call them "Straight out motor" versions) don't have these big aluminum transfer gears.??

Like you said, it's not easy to get some of these gears off.? I don't think you want to pull on the gear or it may bend.? You might be able to get a gear puller's fingers down behind the hub, so you don't pull on the gear teeth area.? But if the setscrew is locked down...it might be impossible to get the gear off.??

I agree that when I tried once to get a gear off, its setscrew was stuck very strongly.? When I talked to Mr Losmandy a few years ago for advice he said it normally uses a 0.05 inch allen wrench. But I never got that to work on that stuck gear.??

(You might call or email Brian at the company to ask for more recent advice.? )

I think the problems are:
? ?a) corrosion can form between the two metal surfaces....the black steel oxide surface and the aluminum gear ID surface. Over time more oxygen gets in to that interface.? When aluminum (or steel) oxidizes at the surface, the added oxygen atoms form a very hard Al2O3 surface.? The Al2O3 is thicker than the Al metal, and this surface layer therefore pinches more strongly on the hard black steel setscrew surface. (See... .? ? )
? ?b) the setscrews that are black are a hardened steel.? Maybe the Fe and Al atoms at the surface mix (friction welding).? See this article about galvanic corrosion of the aluminum and friction welding.? (It's why steel sparkplugs in aluminum engine block must use an anti-seize compound else the plugs won't come out)...:




When facing a similar problem with stuck tiny black steel setscrews:?
? I took the next larger hex wrench and slightly filed down the flat edges until it fit snugly in the stuck setscrew, where the standard 0.05 inch tool was too loose.

? Next get some "Liquid Wrench" and apply that to the threads area.? It will take time to seep in and hopefully reduce some corrosion.? Let the chemical sit for awhile to give it time to penetrate.

If I get the black setscrew out, I often replace it (especially in the Oldham Coupler where this same stuck setscrew problem can occur) with one made of stainless steel.? That's less likely to corrode, or cold weld. The stainless steel setscrew forms it's own chrome oxide surface that won't oxidize further and thicken the aluminum surface like a black steel setscrew might.?

If I don't have the exact one fitted in the gear, I also have drilled and tapped in the tiny setscrew with a slightly larger one so a bigger sizes Allen wrench will be more able to drive it in and out. The 0.050 Allen wrench will just twist like a wire.? ?I use either 4-40 or 6-32 thread ( easy to obtain in the US... metric easier to find everywhere else on earth).

Anyway, just take your time getting a solution to the stuck gear.? Definitely call or email.Brian to inform him of the removal issue and ask for guidance.??

Best of luck,
Michael



On Wed, Dec 16, 2020, 3:01 AM Gottula, Brett <bgottula@...> wrote:
I've been chasing down some periodic resistance in my 2017 G11 drivetrain. I think I may have isolated it to the gearbox, so I'd like to remove it and pop it open to see if I can tell if there are problems in there. In order to remove the gearbox I first need to pull the spur gear off of the shaft, but so far I have been unsuccessful.

Questions I haven't been able to find answers to from my searching so far:
  1. Are there any disassembly guides for recent G11s that cover the spur gears and gearbox?
  2. Anyone know the exact allen key size to use with the set screw? In my kit, 0.05" was the largest SAE size that would fit, but it did not feel as snug as I would expect. 1/16" is too large. (Similar story for metric; 1.3mm fit but poorly; 1.5mm is too large) When I applied enough torque with the 0.05" it skipped a step...I don't want to strip it out.
  3. Any other hints on how to remove this spur gear? Do I need a gear puller or anything else?
Thanks in advance! Some photos below to illustrate what I'm talking about.

Gear on the left is what I'm trying to remove. The shaft for that gear is shared with the gearbox that is on the other side of the machined plate.


The stubborn set screw with unknown hex key size.
 

Michael,

Thanks so much for the detailed reply and suggestions! I will give some of those a try. I'll give the Losmandy folks a break for holidays and to recover from COVID before I pester them but thanks for suggesting that as well. I re-assembled things for now to see if I can catch this conjunction on Monday.

Best,
Brett
 

Brett,

My first post to the forum!? Sorry for the post to an old thread.

I found this thread when I ran into the same problem as you.? Did you resolve your issue?? I have a Sept-2018 vintage G11 RA with the tucked motor design, and I was able to break the set screw loose using the advice from Michael below.

I first attempted to remove the set screw using a Bondhus 0.050 in ball driver hex key.? It was a snug fit, but the hex key was too long and would act like a torsional spring.? I gave up after the key slipped.

After seeing Michael's advice below, I put a single drop of liquid wrench in the gap between the gearbox shaft flat and the spur gear.? My thinking was that the fluid would be drawn through the flat and to the underside of the set screw.? I didn't want fluid on the top of the set screw, since it could cause the driver to slip again.? I left the set screw to soak for about 4 hours.

Instead of using the hex key again, I bought the driver pictured below.? Before using the driver, I measured it using a micrometer to make sure it was the right size and wouldn't slip.? The set screw was still difficult to remove, but it finally let go with a loud ping.

The spur gear was a snug fit, but it wasn't too difficult to pull off of the gearbox shaft with my fingers after I loosened the set screw.? I replaced the black oxide set screw with a "316 stainless steel, 4-40 Thread, 1/8" Long" from McMaster-Carr.

If anyone is still following this thread, I can elaborate on why I was replacing the gearbox in the first place.? It probably deserves a separate post.

Thanks,
Dwight

Amazon link to 0.050 driver:
 

Brett,

I'm sure you have solved this problem already, so this is for others with similar issue if stuck Allen key screw. I've found a driver works the best. You can buy driver hex key sets easily online. The hammer action does the trick without stripping the key hole.

Peter.
 

Peter,?

What do you mean by "hammer action"?

--

Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

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