Bachmann 'Voyager' motor speed limit on DCC...?

[Jack374]

Hi,

 

After a couple of years out of service due to poor (namely slow) running, I've finally got round to having a look at my Bachy Virgin Voyager (220018). After taking the body off, I found my Dad had converted it to DCC by hard wiring a Bachmann decoder in. I duly stripped the curcuit board and added a new 'socket' (used loosely) comprising of 4 pins as there are separate decoders in the driving cars for the lights.

I swapped the decoder for a Hornby one as the original may have been faulty but the problems persisted. I then jumped the socket to allow analogue operation and it ran sweetly and I could achieve prototypical speeds on a Hornby analogue controller.

 

So my question is, is there some kind of 'speed limiter' on decoders? Is the Voyager just not meant to run on DCC? Or is another manufacturer's product better for this kind of conversion?

 

Here's some piccies to illustrate the set up:

 

Many thanks in advance,

Jack.

[smokebox]

What DCC controller are you using?

 

Many decoders are able to have the top speed limited but the basic Hornby decoder doesn't have that capability. I think most Bachmann ones do. Straight out of the packet, the decoders will be set for max speed.

 

The NCE powercab can often cause slower running as the power supply supplied with some of them is a bit low on voltage.

[Jack374]

What DCC controller are you using?

Many decoders are able to have the top speed limited but the basic Hornby decoder doesn't have that capability. I think most Bachmann ones do. Straight out of the packet, the decoders will be set for max speed.

The NCE powercab can often cause slower running as the power supply supplied with some of them is a bit low on voltage.

Thanks for the info, and I do use an NCE Powercab so maybe this is the cause. What voltage should it be then? It says it's a DC 12v, 1.5a output, is this correct? It is true as I've measured 12.05v on the rails with an ammeter.

 

Thanks again,

Jack.

[34theletterbetweenB&D]

...What voltage should it be then? It says it's a DC 12v, 1.5a output, is this correct? It is true as I've measured 12.05v on the rails with an ammeter...

 

Caution 1. You will not get a meaningful voltage reading from a DCC system output using an ordinary meter, as they are not set up for the near square wave output of a DCC system.

 

Caution 2. The voltage on the rails - whatever it may be - is not what is supplied to the motor by the DCC decoder. The decoder first rectifies the track supply - a voltage loss occurs there - then controls the motor with a modulated output -  more voltage loss -  and exactly how much loss depends on the decoder's control system design.

 

By simple trial and error with the system I use which offers DCC track voltage adjustment, I have found that with the decoders I have standardised on, a nominal 18V output setting of the DCC system was required to match the maximum speed of the same locos without decoders operated using standard 12V DC controllers (old H&M units).

[Jack374]

Good shout, I hadn't thought about the final output (decoder) to the motor, I shall have to investigate....but not for the next two weeks (holiday).

 

Many thanks,

Jack.

[34theletterbetweenB&D]

You should be able to get a decent estimate of the voltage over the motor terminals with the decoder at full output and motor running, and a similar estimate for the same loco without decoder, driven from a DC controller. Don't take the numbers as accurate - neither will be correct as the DC supply is not continuous in either case - but they should serve for comparison purposes.