Railbus shows 'jerky' drive while driving at low speed

[Hobojohn]

My railbus 'jerks' while driving at low speed.
It runs with dcc.
Any thoughts on what may cause this?
John Baron
Netherlands.

[Hunt]

Disassemble and closely inspect the gears. Carefully remove any rough places found.

Properly lubricate as you reassemble.

Check electrical pickup points for good contact. Clean the wheels and track. Place a very, very small amount of conductive contact lube on each metal driving wheel tread and electric pickup rub points.


Still jerking... Did you change decoders? If so, check with the manufacturer of the decoder now installed in the Railbus to determine if the decoder is compatible with the capacitors on Bachmann's PCB board. If the decoder installed is not compatible, then if legal in Netherlands, cut one leg of any capacitor on the PCB board.

[Hobojohn]

Thank you Hunt for your tips.

I have checked parts of the drive already. No binds there.
Perhaps is is the decoder.
I will find out.

John Baron

[Steve Magee]

John, did you try the railbus on pure DC? Dual mode decoders can run on either DC or DCC so it could be a way of checking things out - although I would preferably use a by-pass plug in the socket instead of the decoder, to take the decoder right out of the picture. Then it would only be - if still jerky - mechanical or electrical pickup. One question though - what are the lights doing while the jerkiness is going on? Flickering lights are a sign of pickup problems - either in the pickup path, or on the track itself.

Steve Magee
Newcastle NSW Aust

[Hobojohn]

Hello Steve
Hello Hunt,

Ok, you both got me going. I took the new installed decoder out and tried it on 'regular' dc. The old fashioned way. What a different type of power. That we accepted that in the years behind us!
But, more important: I was happy to see no jerking showed anymore and thus: no binds in the mechanism !.

((Remember the discussion here on jerky Climaxes. That turned out to be  a mechanical problem)).

I also have to buy a different decoder. I will order an appropriate Austrian ZIMO with a susi plug because I have installed sound also.
In Europe these decoders are top of the bill.

I should have taken one in the first place.

Thank you both for your much appreciated replies.
You will be informed on the results (will take a couple of days).

Anyway: narrow gauge greetings to you from this side of the globe.

John Baron
Harderwijk
Netherlands.

[Hunt]

John,
If you have the time before installing a new decoder...  I would like to know what happens to run performance if you reinstall the Bachmann decoder. Set the Bachmann decoder CVs to their factory value by programming 8 to CV8.

Also what DCC system are you using?

[Hobojohn]

Hello Hunt,

I installed the original decoder again with the standard settings. It powered the bus without jerking. Proof again that this jerking was not caused by a mechanical shortcoming but by the other decoder I used. I was glad to see that again.

Point is though that de original decoder is a bit noisy one. In use with my cab it even let the bus 'jump' a couple of times when I let it run for some time at the most lowest speed possible. The original decoder also ashuts on/off the front lights and the markerlights the same time (wires ond the decoer are cross-wired). With another decoder (with the green wire attached to the plug) you can shut them on/of seperately.

No problem for all those users who do not mind this, but if your personal standards are higher, like me, another more expensive decoder should be considered.
But make a good choice. I am going to do that now. The bus is more than worth it. Great little machine for which all the credits go to 'our'  Bachmann.

I use the Lenz LH 100 system.

John Baron

[Hunt]

Hi John,
You did not state upfront, but; I surmised you had replaced the factory installed Bachmann decoder. We now know the unidentified decoder you used to replace the Bachmann factory installed decoder is not compatible with the install suppression capacitors and inductors on the Bachmann PCB.

Make sure the next decoder is compatible with the Bachmann PCB or you will have to cut the leg of any capacitor across the motor circuit and jumper the inductors to obtain best possible slow running speed. Or... remove the Bachmann PCB and hard wire the decoder of your choice. If you hard wire, remember to include a proper resistor in the light circuits.

[Hobojohn]

Hello Hunt,

In the meantime I have installed a new (motor)decoder, it is the Austrian built Zimo MX 64, readily available here in Europe, top of the bill, but it is not a cheap one.
Through a 'Susi' (solderingpads) connection on this decoder I could keep my (seperate) Uhlenbrock sounddecoder attached. And the sound works with this Zimo decoder also fine.. 

The other unidentified decoder was a german made Uhlenbrock DCC.
I use these a lot on my lay-out and to my satisfaction. Therefore I did not see that the jerky performance, this time, was caused by this decoder. I thought it to be a mechanically problem in the first place. 
But , as was concluded, in this case -with the Bachmann PCB/Bühler Motor- it did not turn out to be a good 'marriage'. 
With the Zimo the bus now runs as a sewing-machine, so to speak.
Thanks again for your support.

John

[Hunt]

You are welcome John.

Thanks for the additional decoder information.

Glad to hear the 'jerky' issue is resolved and the Rail Bus is now running to your satisfaction. All is well that ends well.