Juttery mover

[VicZA]

Hi All,

 

What would be the most likely issue with a loco that has a juttery movement at slow speed using DCC? I figured it is probably one of the following but not sure:

1 - sticky gears

2 - bad motor

3 - poor track structure

4 - bad voltage distribution

 

Any advice would be great. I have a Class C loco from Buchmann fitted with a Zimo DCC chip which is very jittery at slow speeds but runs incredibly well at faster speeds.

 

Also, what is the issue with swopping poles on the DCC track (swopping positive and negative) ... I have done this by mistake and noticed no issue.

 

Thanks

Victor

[chris p bacon]

First job would be to give the wheels and track a good clean to eliminate poor pick up.  If it works at speed it's unlikely to be the motor (in my experience) and the same goes for the gears being 'sticky' 

[VicZA]

24 minutes ago, chris p bacon said:

First job would be to give the wheels and track a good clean to eliminate poor pick up.  If it works at speed it's unlikely to be the motor (in my experience) and the same goes for the gears being 'sticky' 

How would you clean the wheels and track - do you use any sort of solvent or product?

[chris p bacon]

1 minute ago, VicZA said:

How would you clean the wheels and track - do you use any sort of solvent or product?

 

For the wheels I use a cotton bud with some IPA or lighter fluid on, this will lift the dirt off without scratching the wheel face (scratches will give dirt a key to grip the wheel face in future) you'll need to turn the wheels so that you get all the faces, don't forget any pony wheels as they'll carry dirt and deposit it on the track.

 

For the track I use a pad of kitchen roll with the same IPA or lighter fluid. I think you might be able to use white spirit or meths but i've never used them.

[Right Away]

On 20/06/2019 at 09:02, VicZA said:

Hi All,

 

What would be the most likely issue with a loco that has a juttery movement at slow speed using DCC? I figured it is probably one of the following but not sure:

1 - sticky gears

2 - bad motor

3 - poor track structure

4 - bad voltage distribution

 

Any advice would be great. I have a Class C loco from Buchmann fitted with a Zimo DCC chip which is very jittery at slow speeds but runs incredibly well at faster speeds.

 

Also, what is the issue with swopping poles on the DCC track (swopping positive and negative) ... I have done this by mistake and noticed no issue.

 

Thanks

Victor

My first C class purchased around 4 years ago has always been a smooth, quiet runner. However, my second C class, a more recent acquisition, although smooth in operation was not very quiet at all. Although a "new" model, I now suspect this was a result of extended time in storage  (these models have been around a while) and poor initial lubrication at manufacture.

 

Having spent much time adjusting CVs in both Zimo and Lenz decoders in the loco with a view to finding the "sweet spot" without success, I lifted the engine body and saw that the mechanism was very dry. No sign of grease or oil in the gear train. The motor ran quietly when released from the gear wheels suggested there was nothing awry with either decoder.

I very carefully applied oil to the gear wheels, motor bearings and while I was at it, the coupling rod bushes and axles with a pin applicator.

On reassembly, the loco is now much quieter.

 

 

 

[34theletterbetweenB&D]

On ‎20‎/‎06‎/‎2019 at 09:02, VicZA said:

... I have a Class C loco from Bachmann fitted with a Zimo DCC chip which is very jittery at slow speeds but runs incredibly well at faster speeds...

If none of the above suggestions resolve it, some adjustments to decoder CV's are likely to fix the jitter. I have had a couple of Bachmann motors that were altogether too efficient - started on a breath of current - and these needed changes to the BEMF regime to obtain smooth dead slow operation.

 

On ‎20‎/‎06‎/‎2019 at 09:02, VicZA said:

Also, what is the issue with swopping poles on the DCC track (swopping positive and negative) ... I have done this by mistake and noticed no issue...

Nor should you. The decoder rectifies the DCC track supply to provide DC for the motor, and supplies that DC to move the loco front end leading 'forward', rear end leading 'backward' in response to the appropriate command. You can see this easily by lifting a running DCC loco off the rails, turning it around, and replacing it on the rails: if the loco was running forward, it will resume running forward, now travelling the other way on the track. The DCC track supply connections do not determine direction of movement in DCC, this is achieved by the DCC decoder responding to a command.