Problems with DCC After Ringfield Motor Upgraded

[Merlin The Wizard]

Hello all.... In order to give my Class 86 a bit of pulling power I decided to upgrade the Ringfield motor to a "CD" motor. The installation was very straightforward and I looked forward to a smooth running engine. The unit was already converted to DCC with a hard wired Hornby R8249 decoder.

However at very low speed the train judders violently and if pulling coaches/trucks inevitably causes derailments, once speed is increased by the controller the juddering disappears. The same problem happens when the train comes to stop after slowing down.

I complained to the supplier who provided a replacement motor but this has made no difference.

I have tried adjusting "Startup Voltage", Acceleration/Deceleration rates via my Elite but I'm a little out of my depth.

Today I have removed the decoder and returned the train to analogue and ran it my DCC layout as "Train 0" and it runs perfectly at all speeds.

I'm not sure what the voltage rating of the motor is as there doesn't seem any markings relating voltage on the motor casing

I'm contemplating borrowing another decoder from another engine but seem to remember I'd already tried this some months ago with no success.

Any suggestions would be welcome.

Thanks

[96RAF]

Likely the motor is 6 volt, at wort 3 volt meaning it is never going to run smooth at low revs.

The R8249 decoder does not support changing start voltage CV2 or CVs 5 and 6 top and mid speeds, so that will not help either.

The ringfield gear train is not the smoothest of designs so combined with a poor motor you can get the backlash equivalent of cogging.

[ntpntpntp]

It's likely the decoder really needs re-tuning with different PWM frequency, back-EMF sensing, start voltage etc. to better suit the different motor characteristics. It sounds like the Hornby decoder maybe doesn't support that level of adjustment?

I'd stay well away from running un-chipped locos on a DCC layout even if the system does support running an analogue loco via zero-stretching of the DCC signal. It's an old part of DCC technology/capabilities that fell out of favour many years ago, it can be really bad for small loco motors. Some brands of DCC system specifically warn against using it with N gauge locos (for example).

[P-Henny]

Even in Hornby's current documentation, where they state that Address 0 (zero bit stretching) is supported, they now also put in an additional caveat that it is not recomended. The later Select firmwares now have it disabled by default. As others have said, using Address Zero really does risk permanently damaging the motor.

[ColinB]

I must admit when I did the same to my class 29 I had no such issues but there again I used a CD drive from Horns and Whistles workshop. I used Zimo decoders as I wanted to add "stay alive" because of the shortage of pickups on the tyred wheels. The only issue was the noise, quieter than a ringfield but still noisy. I watched charlie's video on Chadwick Model Railways which recommended this one. It is a lot more expensive than the cheap ones but works a lot better and the guy seemed to know what he was doing. It is a 12 volt unit. What I did with my class 86s with ringfield motors was to convert them to the latest Hornby specification. The old body fits the new single driven bogie chassis and you can buy the other bits as spare parts, it works much better. I couldn't do that with my old Hornby class 25 and class 29, as Hornby don't seem to have ever rereleased them.

[Barry-350851]

Hi Nigel,

I've done my old 'Frank Hornby' class 86. I'd have to have a look at what is in it decoder wise, I think a LAISDCC decoder from memory.

I know I used a 12v CD motor for the conversion on Frank and it runs fine.

From memory again, you can get a 12v for the Bo-Bo (2-axle bogie) motors both Lima and Hornby ringfields, but only a 6v motor is slim enough to fit the Co-Co (3-axle bogie).

I haven't had any problem with the 6v in a Lima cl37 on DCC either. Fairly smooth, maybe lacking top speed and a little noisy, but not what you described.

I'd try a different type of decoder, but could be you've got a duff motor.

[Merlin The Wizard]

Thanks Barry 350851, I don't think it's a duff motor as it works sweetly when run in analogue mode.

I'm going to try another (non Hornby) decoder to see what that does.

[Merlin The Wizard]

HOORAY!

After fitting (what I believe is) a Gaugemaster DCC25 Opti decoder (bought second hand with no instructions/packaging) the unit runs extremely well at low speed and also coming to a rest..... NO JUDDERING.

Not sure if the Hornby R8249 is faulty or just incompatible with the CD motor.

Thanks to all for your responses.

[ColinB]

I am not surprised, I have had so many issues with decoders not driving the motor properly. I tend to stick to Zimo or Train o Matic ones.