Bi-motored Class 56 synchronisation problems

[96RAF]

This is an old Class 56 that couldn't pull the proverbial skin off a rice pudding, so I added a new second motor bogie and also replaced the old one with a new one.

 

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The decoder is an R8249 which oddly is capable of handling both motors at full chat, and directional and cab lights without tripping out. Swapping the decoder for a Sapphire makes no difference Tomthe problem below. Both motor bogies have been serviced to ensure gears run smooth, etc.

 

The problem I have is one motor kicks in before the other  and drags the dead motor round the track until the power setting gets high enough to run both, when it takes off like a scalded cat but under control.

 

What would people suggest to overcome the problem. The end game I suppose is two decoders, with the tardy motor Vstart set to kick it off at the same time as the keen motor. This would be extra work I dont really want to do but if needs must then I will.

thanks Rob

[Fozzy Bear]

Could only be a high resistance connection on the motor which lags. Or broken strands inside the wire.

[37lover]

Rob,

Not ideal but if Fozzy Bear is right, and you cannot improve the poor connections, could fitting a resistor in series with the good motor resolve the problem. I have no idea what value resistor or whether this is method has merit but if it works it should be a lot simpler, and cheaper, than a second decoder. 

[96RAF]

Thanks guys.

I have plenty of spare basic decoders and I'm sure the wiring is sound, but I dont have a variable resistor handy to determine a value for the hot motor slug.

[Fozzy Bear]

Another possible point of resistance is the commutator or the brushes. 

Do you have a multimeter that you can check resistances with?

[96RAF]

I have several avos but didnt particularly want to strip a new motor down, but i suppose i can get some reading across poles via the brushes and turning the wheels.

[Fozzy Bear]

Yep, I didn't really think it would be internal as the motors are new, just a stab in the dark basically.

If its not a connection.........I got nothing... 😢

[Fishmanoz]

Don't think a series resistor will get you far.  Remember on DCC, full volts is applied all the time with varying mark space ratio determining average to the loco.  Then again, it may do.  You are right about 2 decoders and Vstart but you will need more than basic to have this adjustment.

[Fozzy Bear]

RAF, can you confirm some things?

The DC output from the chip is connected in parallel to the motors?

Is the chip mounted in a socket?

The blue wire to the motors is just one you used and not the common positive for the functions.

Does the lagging motor run at the same speed as the good one, once it gets going?

I am leaning back towards a dirty commutator. It has a high resistance connection from brush to plate and once the motor spins just a little, the resistance drops to zero.

[96RAF]

I will look at bemf hadnt thought of that - If the decoder supports it.

 

Had not thought that basic decoder would not have Vstart, so may have to be a Sapphire if I go to two decoders.

 

Ah yes, my wiring colour code, whatever I have in the box, but to a noted pattern Of the day, in this case,  blue and white are parallel motor feeds, with red and black from the front and rear bogie pickups. 

 

Yes I have a standard 8 pin socket in there somwhere under the rats nest, The middle four wires from it go to that small plug which attaches to the express lights kit in the body.

 

Both motors seem to run at the same speed when they are up and running as far as I can tell by sound and vibration, so it does seem to lead to an electrical problem on the one motor, maybe just brushes not bedded in yet.

 

Ill give it a good run in in both directions then pull the slow motor for bench check. I guees the train room air con is going to have to be cranked up later today.

[2e0dtoeric]

I'd turn the 'blue air' filter on, as well!  😛

[96RAF]

After running it for an extended time on the rolling road the R8249 decoder tripped out, so I replaced it with a Sapphire, which also tripped out after about 15 minutes and had to be reset to get it back on its feet again.

 

After another extended session in both directions one motor is getting hotter than the other so its a strip down to see where the problem is.

[Fozzy Bear]

Thanks for the info. I know what you mean about "whatevers in the box". All my track droppers are red and white wire, only because I happened to pick up a 100m roll of the stuff.....

Sounds like the hot motor is a dud. 

[96RAF]

I reckon Ive got a flaky motor, and as Ive got it all in bits Ill look at putting a second socket in and run sound from one and lights from the other.

 

I was comparing the Class 56 motor bogies with my TTS Class 37 and it could be a possible switch to the much better motor bogie, if I can find some or I may replace the old ringfield innards with slim DVD motor - cheaper option.

[Rog RJ]

The hot motor could be caused by a weak magnet.

[Fishmanoz]

Rob says both motors are new, at least the bogies are.

[96RAF]

They were both new either from Hornby or Peters Spares, but can a magnet deteriorate on the shelf as I dont suppose new means made last week, probably years ago.

 

Neither has been stripped down yet so I cant blame it on being that.

 

I have a neo magnet for this version ringfield but cant get it to work on the old motor bogie, too notchy to start or run slow, will only run almost flat out after a helping hand, so I gave up, put the original magnet back in and it sits in the spares box.

[ff2nd]

I think, if it was me, I'd go with twin decoders, but I would give them separate numbers, then create a consist in the controller. That way, they will only ever run as the weaker one runs.

[96RAF]

Its all in bits at present aiming for the double decoder route, one looking after sound and the other looking after the lights, each with a motor to run. Workbench has been covered up pending gardening leave to spruce the place up a bit.