CV Settings to improve slow speed running - Zimo Mx645

[rgsmg53]

Having solved the front headlight problem on my LGB Otto with the help of the experts on this forum, I reckoned I could have a go at solving a slow speed running problem by myself. Well, I've failed so far so it's time to seek more advice from you experts out there!

As the MX645 is a sound decoder certain of the acceleration / deceleration settings are 'non-standard' to synchronize with the recorded sounds. This means my Otto has quite realistic inertia but at crawl speeds (at start of acceleration and the end of deceleration), the loco does not run smoothly at crawl speed and emits a 'growling' sound. I also get the same behavior in both directions at constant speed for a very low throttle setting.

The motor appears to be a normal permanent magnet type with a through shaft with a worm gear on each end driving each axle.

I've gone through the Zimo manual and made adjustments to the CV settings they recommend but without much success. I have been fairly cautious and tried adjusting one CV at a time to try to understand what effect each has on this loco. However, I suspect the only way to solve the problem is to adjust two or more CVs together and, at the moment, working out which ones is beyond my capabilities.

Has anyone had this experience with setting up the Otto or solved a similar problem with another loco? Any advice very welcome.

Thanks in advance,
Richard

 

[stockers]

Most motors seem to 'growl' when run very slowly. I guess they are just going a bit too slow for the armature to keep spinning smoothly.
That said, you probably have a CV to adjust the motor frequency (on Massoth its CV9).
Massoth default is 16Khz, which is usually OK for LGB buhler motors. There are only 4 settings available on Massoth so easy to try each one. I have heard that Piko run better in an alternative frequency but I'm not sure which one.
Alternatively, the jerkiness might be power pickup - a power buffer might help here. Not sure if Zimo provide for this though.

 

[rgsmg53]

I've added 4800 micro-Farads capacitance for energy storage which I decided to do whilst I had the loco dismantled.

The one thing I haven't tried yet in changing the motor frequency. On Zimo this is Bit 5 of CV112 and the choice is limited to 40 or 40 kHz. I'll try this later today.

Thank you.
Richard

 

[rgsmg53]

Sorry, I meant 20 or 40 kHz.

 

[PhilP]

If you can run it without the body..
When you change the motor frequency: run it for (say) 20 minutes, at a low-medium speed, and see how hot the motor gets..
Some motors do not like certain frequencies and get 'chuffin' hot!

 

[shropshire lad]

Have you done a motor load dependance run Richard?
That will optimise motor emf and synchronise sound, CV 302 set to 75 for forward and if different to 76 for reverse.
Make absolutely sure you have enough track in front of the loco tho, at least 5 metres, as it will really move off.
Section 5.3 in the manual if you want to check first.
Cheers Colin

 

[rgsmg53]

Thanks for the suggestion, Colin. No, I haven't tried this yet. In fact, I'd missed section 5.3.

However, there is one slight problem - I'm not sure I've got enough straight track for 5 metres yet! I've got plenty of curves but they are all Radius 1 so presumably a bit too tight for a good calibration.

Just to explain to you experts out there, I decided to spend out on DCC before I went too far as I realised that a) it will determine how I wire up a layout (very simple) and b) it will allow me design flexibilty as a layout grows. What started this was the birth of my grandson a year ago now and I'm gradually building up a layout bit by bit as and when I can justify the expense. The trouble is, being an engineer, the technical aspects of DCC have really taken my interest.

So, forgive me if it is a week or so before I try this.

Many thanks,

Richard

 

[shropshire lad]

I've got to agree with you regarding dcc being fascinating Richard. I invested in some wheel rollers a while ago which I find makes makes testing and programming a lot easier. I bought Bachmann ones as the Massoth weren't available at the time.