Top and Mid Volts CV's - Do I Need Them?

[Stephen in Kerry]

So, finally got my first loco with DCC sound fitted. It's a Bachmann Brachline model (see 'latest acquisition' thread). Apologies if this is not an appropriate forum subject, but the question may apply to Hornby DCC locos.

CV's 5 and 6 are Top Volts and Mid Volts. I hadn't heard of those before - to be honest, I haven't heard of most things related to Railway Modelling before - so I'm wondering what they do and if I need them?

Thanks again.

[96RAF]

They are part of the speed curve that runs the motor.

There is a start voltage CV2, a middle of range voltage Cv6 and the max voltage CV5. If supported by the decoder you can adjust these to say limit the loco top speed, you do however need to adjust mid voltage accordingly. Start voltage is normally only adjusted to kick start a tardy motor.

These three CVs comprise the simple speed curve. A complex speed curve allows other CVs to be adjusted to provide a different throttle response, i.e. linear if all the points are proportionally ‘straight’ or low end or top end responsive if the points are adjusted for a steep initial rise flattening out at higher throttle, or a flat initial response rising sharply at higher throttle.

A picture is worth a thousand words here.

[Stephen in Kerry]

@96RAF Thank Rob, sounds a bit too steep on my learning curve. I think I'll walk before I can run and leave them as they are.

I don't even know what settings were made, as it's a pre-owned loco. But it seems to be running very well so far.

It certainly crawls much better than the Hornby Aberdonian I have. But that might need running in.

[Fishmanoz]

These CVs and speed curves are definitely in the ain’t broke don’t fix it category. If running well, no need to worry about them today.

[Cathurga]

They are very useful if you have a CD Can motor conversion on a ringfield motor. Most of the CD motors are 6V so limiting voltage out of the decoder is likely to limit speed and save the motor

[96RAF]

@SiK

If you ever want to fiddle with speed curves as part of DCC-101>> DecoderPro is a free download as part of JMRI which allows you to quickly adjust and assess effects on the complex speed curve as simply as you would use a sound mixer / graphic equaliser. If it all goes belly up then just press reset.