Bachmann G scale shay

[Brian Harrap]

Has anyone come up with a solution to the tendency of a battery powered Bachmann G scale shay to surge or hunt when going downhill.

It's driving me nuts.

Best and stay well, brian.

[Sturminster_Newton]

Can you ease the gradient?

 

Reduce the consist length/weight.

 

Does the loco have the same issue when light engine or does it get progressively worse as the load rises?

 

The various universal joints adding to the backlash of the gear-sets which may cause some oscillation back and forth along the transmission. As the loco 'brakes' and frees and the consist runs free and is braked.

 

I assume the loco has a worm drive somewhere in the system which 'loads' and 'unloads' to start the problem.

 

The live steamers don't do it as they are a more direct drive at around 4 or 6:1.

 

The electric might be an overall 40:1 by the time it gets to the foremost/rearmost drive point. The transmission is trying to drive the motor worm faster but all it can do is force the drive gear into tighter mesh with the worm.

 

As the worm leaves one tooth for the next the whole system unloads the motor spins up and then the weight forces the gear hard against the worm track providing some braking until it disengages for the next tooth.

 

Eventually the worm will chew through the drive gear as at some point a gear tooth will fail, if the pins on the universals don't fail first.

 

Steep grades and high worm gear reductions are poor bed fellows and surging is the outcome.

 

There won't be a problem going up as the load is fairly constant but down, whole new ball game.

[lankyphil]

I had a similar problem with surging on my Bachy Railtruck. Managed to mostly cure it by adding a "brake" on the front bogie from a bit of brass strip. It adds just enough drag so that it has to actually drive down grades so the UJ bevel box is always under a load of some sort?