Mallet motor sync.

[Slawman]

I have recently started using a rolling road for loco maintenance and fiddling. For the first time I am able to closely observe my locos drive mechanism and have noticed the two motor sets of my mallet run at different speeds....

The one in front starts before the rear set and is noticeably faster than the rear.

Over time I am sure this will lead to a premature failure of relevant bits.

Is there anything to do about this? I am not aware of any individual adjustments to calibrate the motors.

 

[Greg Elmassian]

The short answer is that under load, they normally equalize well... the faster one will take more load and current and the slower one will keep up.

Greg

 

[Zerogee]

From similar experiences, I'd agree with Greg. Both of my Trainline45 Harz Mallets exhibit similar behaviour on the test rollers, but once on the track they seem to run just fine.
However if you still notice any significant wheelspin from one power unit while actually on the track, it might then be worth the trouble of checking the amp draw from each motor, just to make sure one isn't on the way to failing....

Jon.

 

[Slawman]

Thanks Gents, Its been one of my best runners for many years, strong and smooth.

 

[PhilP]

'Factory fitted' Mallet had two 55021 decoders fitted..
The prototype has less weight on the front unit, and if the driver gives it some welly, the front will break-away..
Anecdotally, the two decoders had differing settings, so if you accelerated hard, the front bogie would spin. - If you took things more gently, this would not happen.

Personally, I think this was a case of one motor not working as well as the other.. The 'urban myth' built up to explain the effect. - I do not think LGB would have gone to the trouble..

Theoretically, you could 'play' with the speed-step curves to even the speeds.. But life is just too short, so just run and enjoy!

 

[Slawman]

'Factory fitted' Mallet had two 55021 decoders fitted..
The prototype has less weight on the front unit, and if the driver gives it some welly, the front will break-away..
Anecdotally, the two decoders had differing settings, so if you accelerated hard, the front bogie would spin. - If you took things more gently, this would not happen.

Personally, I think this was a case of one motor not working as well as the other.. The 'urban myth' built up to explain the effect. - I do not think LGB would have gone to the trouble..

Theoretically, you could 'play' with the speed-step curves to even the speeds.. But life is just too short, so just run and enjoy!

All my action these days is taking place at scale prototypical speeds (around 30km/h for the Mallet), so no wheel spins..

 

[Zerogee]

'Factory fitted' Mallet had two 55021 decoders fitted...........

Not wholly true in all cases...... the one I bought (factory serial sound board and very early factory-installed DCC) had a horrible lash-up of a single 55020 decoder and a 55030 "booster" to run the second motor.... given that I'd never even heard of a 55030 until I got this loco, I suspect they didn't do this for very long.....
All quickly ripped out and replaced with a Massoth XL, which works just fine of course.

Jon.