Comet GB1/20 gearbox

[Clearwater]

Hi

 

I’m looking for some advice.  I’m trying to assume a comet gb1/20 gearbox.  However, try as I might, the worm doesn’t bite with the first of the gears (38:1).  Am I missing a trick on what to do?  The box is square, the motor screwed in with the larger screws, the motor hole, and those for thr screws, have been carefully broached out.  Before I adopt a more drastic solution, eg broaden the hole/screw points to move the motor down a fraction, I wondered if there was any other things I should look at?

 

Thanks

 

David

[30368]

I'm not familiar with that gearbox but assuming you have assembled the gearbox correctly (is it two stage?) then it sounds like a simple meshing issue so elongate the motor fixing holes to drop the worm gear into the first gear but don't overdo it!

 

Kind regards,

 

Richard B

[relaxinghobby]

I've assembled similar 2 stage gear boxes and guess the procedure is the same for them all.

Once the brassetch is folded into a box and the bearings soldered in add the wheel axle, then the inbetween axle both with there gears on and check they turn freely. Then the motor and worm, and I would elongate the motor holes downwards to allow the motor to be lower slightly. Just a little at a time.

Another idea is to check if the worm is the correct one for the box, is it fat enough and is not miss-supplied?

[Carnforth]

Built plenty of these. I always make sure that 1st stage is directly under the worm by use of washers but to enable this I fit the top left hand (viewed from top) bearing from the outside in then dress back from the inside. This allows precise placement of 1st stage. Then fit the other bearings as per instructions. Should say that I do this prior to folding for ease of access. HTH

 

Edited June 30, 2020 by Carnforth

[hayfield]

From memory the last Comet gearbox I built I had to fettle the motor mount slightly. Now runs ever so well

 

I guess this is what you are doing but I was advised by a kit manufacturer always to build their motor mounts out of the loco first to set up the meshing and run in the gears. High Level gearboxes do spoil us for buildability, setting standards others have difficulty achieving