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Old Feb 16, 2012, 06:44 PM
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sixty9mustang's Avatar
United States, Mt, East Helena
Joined Oct 2005
1,489 Posts
Gearbox pinion problems

Hello All,

I have a frustrating problem with a GWS gearbox, or the pinion really.

What I have is a Carl Goldberg Husky (which really doesn't matter). It requires a post mount gear box for an inrunner brushless motor. Great Planes/Tower Hobbies recommend a GWS 3.00/1 gear box and the AMMO 24-33-4040 inrunner. Being on the cheap side I tried buying a Turnigy Aerodrive B2435-4400 instead of the AMMO motor. Unfortunately the the shaft size is too small for the GWS pinion. So I broke down and bought the AMMO and the shaft is too big for the pinion. So now what can I do? The pinion is supposed to be 3mm, but the LHS says it is 2.8mm, the shaft on the AMMO is also supposed to be 3mm and the shaft on the Turnigy is supposed to be 2.5mm.

Is there a pinion I can buy to replace the GWS one (it is a 22 tooth) or is there a gear box that I can buy that will fit either of these motors?

Thank You in adavnce
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Old Feb 16, 2012, 10:11 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,475 Posts
Drill out the pinion with a 3mm drill.

Harbor freight sells small mm drills. You'll need a drill press and a small vise.
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Old Feb 16, 2012, 10:21 PM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,208 Posts
Walter A. Wood also has a good selection of metric drill bits. Maybe you can find a 2.9+mm as well to start the hole with. 19/64" is 0.296mm. ACE hardware has those Irwin "numbered" drill bits which might suit.

As Hoppy says, drilling out that extra 0.1mm or 0.2mm will be easy enough IF you use a drill press.
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Last edited by Dr Kiwi; Mar 12, 2012 at 06:12 PM.
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Old Feb 17, 2012, 12:00 AM
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Challenger 413's Avatar
Dickinson, Tx.
Joined Sep 2004
5,404 Posts
http://www.e-flightline.com/ sells Cobri gear boxes. They have 3mm pinions although it looks like they don't sell individual pinions anymore. That is an oddball size motor (24mm), does it line up in the GWS gearbox?

I checked BP Hobbies (this is where I've been buying 20mm motor gearboxes lately) and they don't sell 3mm pinions. I checked a couple other vendors with no luck. Seems like Tower Hobbies would sell the pinion for their motors?

Sounds like your best bet would be to drill it out. Otherwise buy another inrunner with a 2mm shaft.

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Old Mar 12, 2012, 04:39 PM
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Gordysoar's Avatar
USA, KY, Louisville
Joined Oct 2002
790 Posts
Drill it out

You can silver solder the new gear on if its a bit loose. Simple to do. Just don't over heat the gear or shaft. If the pinion is a bit loose you just warm it with a hobby pen torch and let the solder wick in. Thats a solid fix.

Per a friend who's been doing it on his high performance sailplanes turning 18" props.
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