AXI Mini AC 1215/20 with VMGM planetary 4.64:1 gearbox - RC Groups
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Sep 30, 2010, 01:27 AM
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AXI Mini AC 1215/20 with VMGM planetary 4.64:1 gearbox

I recently purchased, what looked like a bargain powered glider from a swapmeet. It has a AXI AC 1215/20 connected to a VMGM planetary 4.64 gearbox.

Not quite sure how much power the setup would have I removed the propellor to avoid raising the dust in my workshop. The motor\gearbox runs but sometimes it ramps up to a scream whilst sometimes it just rumbles along very slowly. I'm no expert but thought it might be the gearbox causing the issue and thought separating the two might provide an answer. This is where my problem started, it's not clear how the motor releases from the motor.

The gearbox has 4 M3 screws on the face which were keeping it attached to the bulkhead of the glider. They come out so the motor can go on the bench but I can't see any other screws to release the gearbox from the motor. The website does not give much of a clue and I don't want to break anything expensive.

The internet show both motor and gearbox has 4 mounting holes on a 16mm diameter accepting a 2.5mm bolt. Has anyone got some advice?
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Sep 30, 2010, 01:53 AM
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The front section of the gearbox unscrews and then you can reach the mounting screws inside.

Sep 30, 2010, 06:16 PM
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Dr Kiwi's Avatar
Mike has the correct answer for getting the box apart. I tried one of these gearboxes and was disappointed in that there seems to be a very large amount of friction within... one cannot alter the mesh and even masses of lube and a regime of long slow running to break it in, did not ever free it up.
Oct 01, 2010, 09:05 AM
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I have a vmgm gearbox on a himax 2045 if you turn it over buy hand you can feel a little bit of binding at the same spot every revolution , it's in a glider for about 3 yrs. now and the bind is still there . I've greased it 2 times and it's no help. I'll live with it.
Oct 02, 2010, 04:11 AM
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Thanks Mike & All,

It was tight, and I had to use a cloth and pliers but it came apart to reveal the workings. The motor spins without the gearbox; not as quick as I would have thought for a high class brushless; and does not bind. Put the gearbox back on again and sometimes the motor stalls.

I'll clean it down and lube it up but It's probably a long shot. If that fails it looks like I'm going to have to make an investment.

All the best

Oct 03, 2010, 10:37 AM
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Joel Shreenan's Avatar

Instruction sheet...

Howard, here's a copy of the instruction sheet for that gearbox. I feel the same way you do about the 1215 series of motors. Not much power from a reputable manufacturer. I think they were only rated for 10-15 Amps.

In a previous post, Andy W said he runs the motor while he screws the gearbox case down onto its mount. He does this to ensure that the pinion develops a proper alignment with the planetaries and the outer gear ring in the case. I assume he did that by running the motor at a low RPM and without a prop attached. However, the instructions call for a 30 minute break-in run with a prop attached.

Once the GB has been broken in, it needs to be opened up and cleaned and re-lubed, but without removing the mounting flange. Otherwise you'll lose that precise alignment of the pinion and the other components that you worked so hard to achieve.

The gearbox should work fine with any other high Kv Speed 400-type motor that has the proper shaft diameter and 16mm mounting bolt spacing. Notice in the diagram that the motor shaft can be no longer than 13mm from the front face of the motor.

Best regards -- Joel
Last edited by Joel Shreenan; Oct 03, 2010 at 10:50 AM.

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