Bo-Bo running problem

Thanks to Ron Dodd’s videos I am taking more interest in the mechanical side of my engines. I had a poor running Bo-Bo which on investigation seemed to need new brushes as they were very worn. New brushes were fitted nothing else was touched.

On test, upside down with crocodile clips attached to the pick up and earth it ran smoothly. I let it run for about 10 minutes to bed in the new brushes.

Put it on a straight bit of track and off it went but stopped dead at the first curve, push it and it starts but stops almost immediately. Pushing it around the half circle it came to the straight and off it went but after about 4 lengths it stopped again. Reversing the direction of the engine made no difference. Pick ups were cleaned including the inner sliding mech with a cotton bud and neither seem to be sticking at all.

All wiring checked and the earth was resoldered as it looked flimsy. Engine still runs without any problems on test bed.

There is no sparking that I can see when the engine stops.

As explained when on test upside down the engine runs perfectly but won’t run on the track around curves or even on some straight bits.

I set up a small test track with two curves and a straight. Cleaned the track and checked it with an N2 – track OK. Then the Bo-Bo stutters then stops. I left the front bogie on the track with its pick up and lifted the rear bogie to the side of the track and it ran well but when I moved the front bogie a little it stopped.

My theory is that the insulating washer on the front pick up which is very loose and when the bogie moves it produces a dead short as the pick up washer touches the chassis. So I need to remove the pickup and replace the washer although I will have to make one up from some plastic. The questions are – is this likely and how do I remove the plunger pick up to replace the washer? Is it in Ron’s videos?

This theory explains the upside down running as the insulating washer and the connector would not be able to touch the chassis.

More testing has indicated that my pet theory might well be wrong.

Engine on track, controller on – no movement. With screw driver put pressure on front bogie pick up piston – motor starts running. Take pressure off motor stops.

Seems that the pickup is not making contact with the third rail. Might still have to dismantle the pick up but will try cleaning etc.

White spirit and a cotton bud cleaned the pickups and they now drop down the full extent.

I then remembered that I had fitted a Neo magnet as well as new brushes. If things can be put in 2 ways I usually choose the wrong way first. So the Neo was taken out and turned round – it looked square to me but I turned it round anyway.

Net result is that the engine can now complete a circuit of the track without stopping. What was the Neo doing to make it keep stopping? It was one that was specially supplied for a Bo-Bo.

Final conclusion after all this work, including new tyres is that the engine runs no better than before and still hesitates occasionally just as before.

Put it down to experience


6 thoughts on “Bo-Bo running problem”

  1. Hi Tony,
    Hard to tell what’s wrong without it on my bench, but it does sound like a dirty track problem. Otherwise, assuming you have followed my service video, especially making sure the gaps in the commutator are clean, then I would suggest looking for another “dry” solder joint.
    The wires do protrude from the motor bogie and can push against the body on the bends adding pressure to the solder joints (if not properly centralized) , sometimes this can cause derailments too.
    Good luck solving your problem, you will also be gaining experience as you work at it.
    Regards Ron

  2. I have this problem with a Bo-Bo I converted to 3 rail from 2 using new plungers.
    It runs ok on the Wrenn 3 rail track but stops on the Dublo that I use for curves in a deep cutting where they cannot be seen well. My (little) people agree with me that diesels are more trouble than they are worth. We have 4 0-6-2T that run a treat.

  3. Re Bo-Bo running—I have two thoughts: possibly the plunger housing needs to be lowered to allow further downward travel of the plunger itself, or could it be that a wheel has moved out along its axle causing binding when leaving a straight and riding a curve. Usually these problems are caused by a simple problem—-finding it is the challenge!

    1. Denis,

      I can confirm that it was the plunger housing that was not down far enough for good contact. A bit of brute force, the ignorance comes free with it, to push the plunger housing down a bit has fixed the problem. Thanks for your interest.

  4. Some years ago when I received an inheritance, my partner and I looked into buying a vintage car for days out in fine weather. One dealer advised that buyers/owners had to be prepared to ‘do some tinkering, mechanically, to keep the vehicle running properly.’
    That put us off and we bought a new VW Golf. Seems to me that the fault-finding and problem solving that we have to do on our model railways is no different to the old car ownership problems. Of course our engines and motors are both much smaller and much simpler. But tinker we must to get the best performance (especially when visitors are present!).

    1. David,

      For many years I had a series of sports cars as weekend cars and “fettling” was a frequent occurrence. The worst of times was when the battery was flat and the spin I expected to take was much delayed or lost as as the car was not ready. Jumping it was OK if you weren’t going to stop again.

      Great fun when all was good but speed limits excess traffic took away much of the pleasure and currently living without my weekend car – perhaps one day I will get one again.

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