Assorted DCC issues

[RW&C]

A few years back I got an MRC Prodigy Express system, which seems to work just fine. I'm having some trouble with decoders though.

The first one I installed, I did it wrong, and it fried. D'oh. So I swapped it out for a new one in the same engine, and it works now, but slow speeds are very noisy. With the torque compensation on it sounds a bit like an analog modem at low speeds. With the compensation off it's still noisy but not much noisier than it was on DC. The engine is a Model Power 462 semi-streamliner. (If you're trying to install DCC in one... be prepared for a long fight with the headlight.) Past experience with RC cars tells me to put a ceramic capacitor on the motor leads to filter out some of the current fluctuations that are making the noise, but I'd like to be sure beforehand that there isn't an easier way. The decoder is an NCE Z14SRP 1.3 amp four function.

For my second conversion I'm trying to upgrade an older locomotive, a cheap C liner from Life-Like. The decoder seems to be functioning, but the motor won't turn over. It'll twitch, it'll sort of pull like it wants to spin, but it's like the decoder can't give it enough power to make it go. It's a five-pole skew and it ran decently on DC, although it did get a bit warm (which suggests to me that it draws a lot of power). Should I just replace the motor with something smaller? The driveline turns by hand, and with the decoder disconnected the thing will run on DC. The decoder is an NCE N12SR rated for 1 amp.

Thanks in advance, all this digital stuff is more confusing that it has a right to be.

 

[bnsf971]

One thing nobody mentions, and they should is to check the stall speed of the motor you are trying to power.
DCC uses pulses of DC to the motor to turn it, which means it is trying to move the motor from a standing start, or stall with every pulse. If your decoder's maximum output is an amp, and it takes 1.1 amps to stall the motor, it'll never run.
Those old C liner motors are power hogs, and do draw a lot of current, you may be simply overloading the decoder. A new motor, along with the decoder, is probably much more than the C liner is worth. Maybe you can watch for one of the newer ones with all-wheel drive and can motor factory installed on Flea-Bay, and put a decoder in that. HO isn't my primary scale, but I think Life Like made them in their Proto series.

 

[RW&C]

That was kinda what I'd figured. I've got a smaller motor from a life-like shunter that bit the dust (five pole skew wound with a tiny flywheel), I'll hack that in and see if it runs any better. Thanks.

 

[RW&C]

Well, the small motor didn't work either. I partially suspect that the C-liner chassis, with binding trucks and giant hunks of lead riding around, bound up the motor. So I went back to another engine, another life-like model, that's significantly better quality. But when I opened it up, same motor as the C liner.

I'm assuming I just need to get a 3 amp decoder. But is there anything I can use the 1-amp for? A scale-sized sewing machine maybe?

Anyone know a way to up the amperage? In radio control vehicles I've seen people double or triple up the transistors to allow greater current flow, but looking at the decoder I'm not even sure where to begin, and the last thing I need is another fried decoder.

Thanks for your help.

 

[Espeefan]

A few years back I got an MRC Prodigy Express system, which seems to work just fine.

SNIP

works now, but slow speeds are very noisy. With the torque compensation on it sounds a bit like an analog modem at low speeds. With the compensation off it's still noisy but not much noisier than it was on DC. The engine is a Model Power 462 semi-streamliner. (If you're trying to install DCC in one... be prepared for a long fight with the headlight.) Past experience with RC cars tells me to put a ceramic capacitor on the motor leads to filter out some of the current fluctuations that are making the noise, but I'd like to be sure beforehand that there isn't an easier way. The decoder is an NCE Z14SRP 1.3 amp four function.

You'll need to adjust the PWM (pulse wave modulation) on the motor to get rid of the whine. I've hit this on Bachman Spectruum engines with sound. It should be cv 9 on your NCE decoder (but check the data sheet that came with it). Adjust the value until the whine stops. Try a value of "0" first

For my second conversion I'm trying to upgrade an older locomotive, a cheap C liner from Life-Like. The decoder seems to be functioning, but the motor won't turn over. It'll twitch, it'll sort of pull like it wants to spin, but it's like the decoder can't give it enough power to make it go. It's a five-pole skew and it ran decently on DC, although it did get a bit warm (which suggests to me that it draws a lot of power). Should I just replace the motor with something smaller? The driveline turns by hand, and with the decoder disconnected the thing will run on DC. The decoder is an NCE N12SR rated for 1 amp.

Thanks in advance, all this digital stuff is more confusing that it has a right to be.

If it's a pancake motor, throw it away & remotor the loco. Chances are you'll fry it ofter a short amount of time on DCC anyway. Those old C Liners are K-Mart trainset quality and don't take DCC well anyway. I converted one in the early days and it lastes a grand total of a few minutes before the motor went poof.

If your decoder's maximum output is an amp, and it takes 1.1 amps to stall the motor, it'll never run.

Not quite You'll just fry the decoder if you load the loco heavily enough. Stall speed is the amperage draw when you physically stop the motor from turning at maximum voltage. This should never happen on the layout if you model has a correctly sized motor. The wheels will slip instead, but it is a good rule of thumb practice to make sure you never fry a decoder. Most modern cans will draw between .25 and .5 amp at normal running loads, so I mostly worry about this with older models. Anything made in the last 10 years or so will have a good can motor in it, or if it is open frame, it will be more efficient (like the P2K Alco S-2/S-4 switchers)

Don't bother to try an up the amperage, just get a decent motor

 

[Selector]

Said another way, get a motor that has at least as much power as the engineering department would want for the engine, but that doesn't require so much darned amperage to produce it at the drawbar.

You could have a motor that would make the wheels spin, or you could have a 'better' motor that could also make the wheels spin, but its more efficient design allows it to draw maybe only .75 of the volts and amperage of the first one. If you could actually stall either engine long enough to really heat up the decoder, which motor would you rather have stalled under your shell?

The one that wants the least amount of current to do the same work. Less current means less heat in any motor, but especially in an efficient motor design.

-Crandell

 

[RW&C]

Thanks guys, I'll pitch the Life-Like monster motors into the parts bin and look for something better.

Espeefan, thanks, I'll give that a try.