austerity short circuit problem

[streak1]

this loco is one of the original batch and has run fine since new.

it now shorts out on left hand bends but not right hand ones.

I've removed the body and underkeep but I cant see anything wrong. If inverted and I test the wheels it runs fine and pick ups work on all wheels.

i've checked all motion for fouling and cleaned and very lightly oiled it.When not shorting out it runs very smoothly.

I've run out of ideas so I'm hoping that someone here can help.

Thanks in advance

[RedgateModels]

run it in the dark with the controller wound right up - you might see a spark?

[G-BOAF]

Bachmann locos (unlike some/all Hornby steam locos) have an isolated chassis, with insulated bushes on each wheel centre. You want to ensure that the pickups are not coming into contact AT ALL with the chassis. Assuming the picksup are riveted to the keeper plate, and wires soldered on, check the solder height. Also check the pickups are not 'arching' off the keeper plate, and somehow contacting the chassis. If they are, a bit of electrical or masking tape should be applied along the top of the pickups to isolate them. Similar to any solder or wire contact points

I sounds like the one side of pickups may be touching the underside of the chassis block, such that on curves, the springing of the contact on the other side contact the chassis block and short. Or they could be rubbing on the axles.

These are worth investigating.

I did have an issues with an 8750 pannier where a dodgy circuit board resulted in a screw making the chassis block live, and a insulating the screw from the circuit board solved that. But the early WDs did not have circuit boards I believe.

[streak1]

Thats very interesting and thanks very much for the suggestions from you both. I'll have another look tonight and maybe even put a strip of tape on the tops of the pick ups to eliminate any possible issue with them. i wonder why now , perhaps something is a bit aged and not as flexible (bit like me!).

[34theletterbetweenB&D]

Most likely cause is the driving wheel axles bridging across the pick up strips riveted to the inside of the keeper plate. These may bow up slightly as the model ages; as the wheels move sideways to take up curves, the pick up fingers can also slightly flex the continuous strip inside the keeper plate. A careful inspection may show lightly burnished patches indicating where axle contact has occurred on the pick up strips. Don't forget it can be more than one axle involved. I have simply put a carefully shaped piece of insulating tape the full length inside the keeper plate.

 

(My WD's have the sprung axles given slightly more downward travel by filing small cutouts in the keeper plate sides. After a couple of years I started getting random shorts by axle contact: and always on curves.)

[streak1]

Well I examined it last night and did exactly as 34C recommended. The pick up strips were slightly bowed either side of the driven axle so I covered the entire strip with insulating tape and hey presto no more issues.

Thanks very much chaps for all of the suggestions. G-BOAF you were spot on too.

The upside is because I had it apart and cleaned and relubed everything the loco now runs extremely well! Probably more smoothly and quietly than it ever has. I'll have to do the same to the other one now.