DCC Decoder Settings for Open Frame Motor

[thegreenhowards]

Hello,

 

I wonder if anyone can help me tune a decoder to suit an old open frame motor. I believe the motor is a Romford Bulldog. It is fitted in a Nucast V2 and the loco runs nicely on both DC and DCC. It is powered by an old 5 pole open frame motor which I believe to be a Romford Bulldog (similar to an X04 but smoother).

 

I have hard wired in a Zimo MX617 decoder. It runs well enough, but I believe that it is possible to tune decoders to suit the motor’s characteristics and thereby improve the performance. Is this correct? If so, can anyone point me to a guide on how to do so? I have looked in the decoder manual, and while it suggest settings for coreless motors (which I have used for Portescaps in the past) There is nothing for open frame motors.

 

Thanks

 

Andy

[Nigelcliffe]

Page 19 of Zimo Small Decoder Manual English translation.  On right hand side are tips for for CV56.   CV9 is also relevant, and again experimentation to find optimal value.  

 

The old manual for the MX620, MX62,MX63, MX64,MX64D has a much longer section on motor setup, pages 22-26.  You may find reading that useful.  Scroll down the manuals page on the Zimo website to find it in the older manuals section. 

 

I assume you checked the max current draw of the motor before fitting the decoder.  Old motors can sometimes draw a lot of current, and you may be marginal on the MX617.  

 

 

[WIMorrison]

I run the loco on the layout and keep the room quiet and listen for changes in the sound of the loco as I change the CVs using POM. This has enabled me to work out that CV56=55 or 33 on my locos and CV9 is generally sat at 95.

 

These are the setting that I use on the MX617 and other than changing min and max speed to get realistic operation I find that these are the only 2 that I play around with.

[34theletterbetweenB&D]

36 minutes ago, Nigelcliffe said:

...I assume you checked the max current draw of the motor before fitting the decoder.  Old motors can sometimes draw a lot of current, and you may be marginal on the MX617.  

Strongly seconded. My experience is that decoders with a continuous current capability better than 2x the motor's  12V stalled current are noticeably better performers, particularly observable in starting and slow speed refinement. (I only have one Romford Bulldog now, and it pulls 700mA stalled at 12V.)

[JST]

2 hours ago, 34theletterbetweenB&D said:

Strongly seconded. My experience is that decoders with a continuous current capability better than 2x the motor's  12V stalled current are noticeably better performers, particularly observable in starting and slow speed refinement. (I only have one Romford Bulldog now, and it pulls 700mA stalled at 12V.)

 

Good point. I have a couple of old locos on my layout but the motors have had the armatures re-wound and the magnets re- magnetised. Worth the effort as it pulls the stall power down.

[thegreenhowards]

Thanks for all your help. I will explore the manuals. 
 

I hadn’t considered the current draw as it’s never been a problem, but I take the point that an older motor might draw more current. I think that should be possible on the programming track with my NCE power cab. I’ll check tomorrow. Having said that, it runs fine hauling 30 wagons road my circuit - I just wanted to see if I could make it any better.

 

Andy

 

 

 

[34theletterbetweenB&D]

20 hours ago, thegreenhowards said:

... Having said that, it runs fine hauling 30 wagons round my circuit - I just wanted to see if I could make it any better.

So now the question: just what is the 'better' you are looking for?

[Nigelcliffe]

5 minutes ago, 34theletterbetweenB&D said:

So now the question: just what is the 'better' you are looking for?

 

hauling 50 wagons round the circuit...

[Derekl]

20 hours ago, thegreenhowards said:

Having said that, it runs fine hauling 30 wagons road my circuit - I just wanted to see if I could make it any better.

 

There is an old adage - "If it ain't broke, don't fix it". One I occasionally forget to my cost....

[thegreenhowards]

53 minutes ago, Derekl said:

 

There is an old adage - "If it ain't broke, don't fix it". One I occasionally forget to my cost....

That’s a fair point. I think my aim was twofold:

1. Not to damage the motor by running it on settings for a modern motor; and

2. To see if I could get it to to run any quieter.
 

Andy

[thegreenhowards]

56 minutes ago, Derekl said:

 

There is an old adage - "If it ain't broke, don't fix it". One I occasionally forget to my cost....

That’s a fair point. I think my aim was twofold:

1. Not to damage the motor by running it on settings for a modern motor; and

2. To see if I could get it to to run any quieter.
 

Andy

[34theletterbetweenB&D]

32 minutes ago, thegreenhowards said:

1. Not to damage the motor by running it on settings for a modern motor; and

2. To see if I could get it to to run any quieter.

You won't damage it.

 

Noise output, is it any different if run on DC from a PP9 ('real DC') with that load on your layout? If not then that is the noise it makes, and nothing to be done unless you are prepared to engage in mechanism redesign.

 

(Let me guess, direct to axle drive, metal worm on a metal axle gear? Combined with the weight typical of a whitemetal body, all the mechanism noise is quite efficiently transmitted to the rails, with the resulting acoustic signature.)

[thegreenhowards]

I’ve done a number of experiments today. The stall amperage seemed to fluctuate between about 0.4A and 0.8A on my power cab readout, so I guess its a bit close to the MX617’s capacity and I ought to swap it over. Although having said that it runs well enough. 

 

I also read the old manual which Nigel recommended. Sadly none of the examples were for anything as old as this, but I tried experimenting with CV56 and CV9 and nothing seemed to make a difference, so I’ve left it on the defaults where it runs well enough. 

 

It’s equally noisy on DC so no complaints, I just thought I may be able to ‘magic’ a reduction. 34’C’ ‘s point about the old chassis is well made.

 

 

This was before I fixed the valve gear and chipped it. It’s probably similar but marginally better than a Hornby X04 era chassis. I can certainly live with it.

 

Thanks for all your help. 

 

Andy

[Izzy]

41 minutes ago, thegreenhowards said:

I’ve done a number of experiments today. The stall amperage seemed to fluctuate between about 0.4A and 0.8A on my power cab readout, so I guess its a bit close to the MX617’s capacity and I ought to swap it over. Although having said that it runs well enough.

 

The MX617 has a continuous rating of 0.8A and a peak of 1.5A so I think that it's just fine to use it as the readings are well within it's limits.

 

Izzy

 

p.s. meant to add that cv58 controls the BEMF intensity. It's 0-255 and you could try reducing it from the max to see if it has any noise reduction effect without reducing the motors performance. It looks like an Airfix/MRRC 5-pole motor to me, and they could vibrate quite a bit just loose in your hand, so vibration noise through the chassis would not be surprising.

Edited June 12, 2020 by Izzy
to add a further comment

[melmerby]

Is that definitely a Romford Bulldog?

 

Looks like an Airfix version to me

[thegreenhowards]

49 minutes ago, melmerby said:

Is that definitely a Romford Bulldog?

 

Looks like an Airfix version to me

It could be I'm no expert. I have one in a box which says Romford Bulldog on the outside, and this one looks the same.

[melmerby]

12 minutes ago, thegreenhowards said:

It could be I'm no expert. I have one in a box which says Romford Bulldog on the outside, and this one looks the same.

They are similar but elsewhere I have seen quoted that the Airfix one has the brush holder below the frame rather than above as with the Bulldog & X04.

I've got a 5 pole motor that looks like that but the brush springs are different.

 

https://www.rmweb.co.uk/community/index.php?/topic/146969-can-anyone-identify-these-5-pole-motors-please/

[34theletterbetweenB&D]

14 hours ago, melmerby said:

Is that definitely a Romford Bulldog?

I have a twin to it in one of my old models, and that was definitely purchased as a Romford Bulldog and came in a Romford Bulldog box near 50 years ago. It's a  very effective motor in terms of making the wheels turn smoothly and controllably, and near unstoppable if the power supply can give it sufficient current.

 

15 hours ago, thegreenhowards said:

...It’s equally noisy on DC so no complaints, I just thought I may be able to ‘magic’ a reduction. 34’C’ ‘s point about the old chassis is well made...

Since it is a model of a properly designed steam loco there's all the room required to substitute a modern can motor and multistage gearbox, should you get weary of 'wow-wow-wow'. Having worked on it recently I expect you want to just enjoy it for now?

[melmerby]

I'm confused.

In a RMWeb discussion recently on motors, the Bulldog was supposed to have the brush holder above the frame and the Airfix below.

And a picture I found of a Bulldog shows no oil pads.

 

 

 

[thegreenhowards]

3 hours ago, 34theletterbetweenB&D said:

I have a twin to it in one of my old models, and that was definitely purchased as a Romford Bulldog and came in a Romford Bulldog box near 50 years ago. It's a  very effective motor in terms of making the wheels turn smoothly and controllably, and near unstoppable if the power supply can give it sufficient current.

 

Since it is a model of a properly designed steam loco there's all the room required to substitute a modern can motor and multistage gearbox, should you get weary of 'wow-wow-wow'. Having worked on it recently I expect you want to just enjoy it for now?

As I said this motor is the same as one which came in a Romford Bulldog box. But that is my only experience of them.

 

When I bought it (about two weeks ago) I was assuming that I’d pop in a modern motor/ gearbox. But the chassis is not two brass sides, more like an old Hornby one (which may be the basis of it) as you can probably see here.

 

 

I don’t know how i could fit a modern motor gearbox in that.

 

Having said all that it’s quieter than a whining Portescap, so not too bad, and it looks good as I hope this video on my layout thread shows, so I’ll live with it. If I need to replace the motor in future, I think it would be a whole new chassis.