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Tamiya KV-2 Gearbox

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Old 12-23-2011, 12:49 PM
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Alpha Male
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Default Tamiya KV-2 Gearbox

The left gearbox in my KV-2 stopped working so I took it out and apart. The problem is that on one of the axles has a brass gear (with a hex end - like a nut) that seats inside a 32 tooth plastic gear. That plastic gear wallered out so that the two spin independently of each other. I know its a long shot, but if there is anyone out there who has recently replaced a gearbox and does not need the old one, I would like to buy the 32t plastic gear in the photos or even the entire non-functioning gearbox. It doesn't have to be from a KV-1 or KV-2, but I don't know which others might be similar enough to work.

I hate to buy a brand new transmission for one gear, so any help would be appreciated.
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Old 12-23-2011, 02:19 PM
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Default RE: Tamiya KV-2 Gearbox

Have you tried to CA the hex head back into the plastic gear?
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Old 12-23-2011, 04:36 PM
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Default RE: Tamiya KV-2 Gearbox

No, but I think it would only be a temporary fix and I don't want to have to go back into the gearbox again. I thought about JB Weld, but I'm not sure if I can get the brass and plastic to bond strongly enough. [] I might try it anyway, though.
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Old 12-23-2011, 04:58 PM
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Default RE: Tamiya KV-2 Gearbox


Is it the gear in your 3rd and 4th photos? It looks as if the plastic gear hub cracked? Can't be certain from your photos as they aren't
clear or illuminated well. If the hub isn't cracked I'd run a small pin through the plastic gear, brass piece and shaft to keep them
all together.

I know they're less expensive for Tamiya to use but this is why I don't like plastic gears in such an application; especially
cheaper inexpensive injection molded gears.

An alternative, don't know it it would be appropriate, is to put a proper sized washer on the shaft next to the gear that wants
to go awol then use a small collar next to the washer to keep the gear from moving but keeping it captive against the brass piece.

Jerry
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Old 12-23-2011, 05:09 PM
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Default RE: Tamiya KV-2 Gearbox


Is it the gear in your 3rd and 4th photos? It looks as if the plastic gear hub cracked? Can't be certain from your photos as they aren't
clear or illuminated well. If the hub isn't cracked I'd run a small pin through the plastic gear, brass piece and shaft to keep them
all together.
The third photo shows the two gears that should turn as one. I thought about a pin, but the plastic 'lip' that couples with the brass is too thin.

An alternative, don't know it it would be appropriate, is to put a proper sized washer on the shaft next to the gear that wants
to go awol then use a small collar next to the washer to keep the gear from moving but keeping it captive against the brass piece.
Unfortunately, the brass gear turns inside the black plastic gear like a bearing. []
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