Loco speeds and cv settings?

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centenary
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Loco speeds and cv settings?

Postby centenary » Thu Apr 25, 2019 4:50 pm

Hello again. Ive currently 2 DCC fitted locos and neither of them seems to run very quickly.

My OS is the Gaugemaster Prodigy Express (I think it's a great bit of kit) which, I believe chucks out 2 amps. Im currently only test running the locos on a small oval about 5 foot long. All connection between the Express and track are good. The track is clean. Reading the instructions, the Express defaults the speed steps to 28 but on each loco, Ive used the Express' Speed Step button to change this to 128. The manual says this doesnt change the speed step cv on the decoder.

The two locos are a brand new Hornby TTS Earl of St Germans which has been run in and a 2nd hand Bachmann Fairburn. The seller told me this had a Gaugemaster 8 pin chip in it.

When I run each loco one at a time on the track, neither seems particularly quick. Even with the speed whacked up on the Express, neither is in danger of flying off the 2nd radius curves, not that Id want them to! They run at a nice pace, smoothly just not at what you'd call 'express' speed considering they are on full chat. Id say both locos maximum is probably just over what Id expect half full speed to be.

Seeing as it's only a small oval track, 2amp output and each loco current draw being about 100ma, I cannot think supplied power is the issue and it is a question of CV settings. Can anyone give me information on which cv or cv's I should check and change to increase the running speed, please? Any other suggestions would also be helpful.

Thank you.

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Flashbang
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Re: Loco speeds and cv settings?

Postby Flashbang » Thu Apr 25, 2019 6:51 pm

Top speed is CV5. Check the decoders manual for the range of values a particular decoder make may use. Frequently 0 to 63 or 0 to 255
Once CV5 is set, set CV6 to between 1/3 and half of the value of that in CV5. However, I don't believe Hornby TTS decoder have CV5 and CV6 available!
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Bigmet
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Re: Loco speeds and cv settings?

Postby Bigmet » Thu Apr 25, 2019 8:19 pm

Voltage may be the issue. Many DCC systems don't put enough voltage on the rails, and by the time its been through rectification in the decoder (and then there's the 'off power' back EMF sampling periods to reckon with too) the model isn't capable of galloping along like it will on 12V DC. I run my system with the track voltage 'turned up) so that there's equivalent15VDC at the motor terminals.

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Flashbang
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Re: Loco speeds and cv settings?

Postby Flashbang » Thu Apr 25, 2019 8:50 pm

You cannot alter the output rail volts of a Prodigy DCC system. It is preset with the Express at 13.8 volts at 2.0 Amp and the Advance2 at 14.5v at 3.5Amp
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Re: Loco speeds and cv settings?

Postby Byegad » Fri Apr 26, 2019 2:17 pm

As a DC dinosaur, I'm often impressed at shows with the low speeds reliably possible on DCC. However at show after show I see mainline expresses ambling along at a scale crawl. If 60mph = 88ft/sec, which it does, and your OO scale is 1/76, then at 1ft/sec you are travelling at just over 50mph, a not unusual speed for a fast passenger train. All too often a model with a stretch of mainline will see an A4 moving at much less than 1ft/sec.

I'm not advocating trainset speeds at exhibitions, but I'd love to see an express pass by with an impression of speed.

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Re: Loco speeds and cv settings?

Postby Dad-1 » Fri Apr 26, 2019 3:27 pm

Just a thought, The OP say's he has a small
oval track. There is no way any top-link
locomotive would expect to take 2nd radius
turns at even 50 mph - more like 5 mph.

So I wonder why would you want more speed ?

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Re: Loco speeds and cv settings?

Postby Bufferstop » Fri Apr 26, 2019 4:13 pm

Actually trying to judge one foot per second with any degree of accuracy is quite difficult. The simplest is to measure the length of a circuit and count the number of laps in 30sec or a minute and do your sums.
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RAF96
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Re: Loco speeds and cv settings?

Postby RAF96 » Fri Apr 26, 2019 8:27 pm

CV5 is not adjustable on a TTS decoder, also you must have both the controller and the decoder (fiddle with CV29) set to 128 speed steps for the sound chuffs to follow the speed correctly.
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centenary
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Re: Loco speeds and cv settings?

Postby centenary » Sun Apr 28, 2019 1:28 pm

Hi folks. Sorry for the delay getting back. I'll look into the cv settings on the Fairburn as this has a Gaugemaster chip in it so would expect the relevant cv's to be editable.

The current track loop is just a test track and Ive no intention to run either loco at speed such that they do come off the track. Yes, Id say the current top speed is more scale like.


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