Engine trips breaker in forward, not in reverse

[Tom4884]

I installed a TCS CN decoder in an Atlas GP35 (have done several successfully before), and it reads and writes fine on the programming track.  When I put it on the main line, lights work as expected,  it runs in reverse just fine, but when running forward it moves a little,  trips the breaker momentarily,  starts again and moves a little bit,  then trips the breaker again. If I run it at very slow speed it does not trip the breaker.   There are no unusual sounds such as gear grinding,  no magic smoke,  nor any other cues to indicate what is going on. Any help,  thoughts,  wild ideas greatly appreciated!

Thanks,  Tom

[tehachapifan]

What do you mean by trips the breaker? Are you getting a short message on your handheld throttle?

[Tom4884]

Each power district is circuit breaker protected, and you can hear and audible click when it detects too high of a current draw, such as in a short.

[Tom4884]

Problem resolved!   I had removed the forward bearing blocks per the Bearden article, but it seems with this particular GP35, it caused the drive train to bind and draw to much current,  causing the circuit breaker to trip.  I put the bearing blocks back, and it now runs fine in both directions,  just a little more noisy than I would like.   I have done this procedure on a dozen other Atlas Geeps and never had a problem.   Not sure why this one is so picky, but if it ain't broke...

Tom

[mkearns]

I’m sure the master himself may weigh in shortly - but did you adjust the length of the hex nut/flywheel joint interface to complete the Bearden Bearing Block Magic mod? You need to help control the movement of the worm after the removal of the inner bearing block. This may be the source of your bind and you might be able to have a locomotive that is quiet and doesn’t trip the breaker.

http://u18b.com/wp-content/uploads/2013/03/Bearingblock.pdf

[Tom4884]

I'll have to go back and read the instructions on that, but for now  going to claim victory and start on my next project.

Thanks,   Tom

[Maletrain]

It seems odd that a stalled motor would be able to trip a breaker by just the stall current.

What was the breaker trip setpoint?  What scale are we talking about?

[peteski]

It seems odd that a stalled motor would be able to trip a breaker by just the stall current.

What was the breaker trip setpoint?  What scale are we talking about?

The model is Atlas GP-35 with TCS CN 2-board decoder (designed for those N scale locos) with the worm's inner bearing blocks "Beardenized" (removed).

That does seem odd to me too.  Even if stalled under full 12V I would think that the motor shroud not consume more than 0.5A which is usually less than the trip current of most breakers. 

I'm also curious what DCC system is used and what the breaker's trip point is set to.  The clicking sound seems to indicate a relay-based breaker (Digitrax?)

[jagged ben]

A possibility is that the frame halves were somehow just barely making contact when the motor torqued the motor saddle in one direction but not the other.  And that this was happening in a spot where re-installing the bearing blocks kept the frame halves separated.   May sound unlikely but I've see this sort of thing happen.  It doesn't involve any significant motor shaft binding, just enough to shift the motor saddle when the direction reverses, which is quite normal.