Permanent Multi-unit lashups

[Jim Costello]

I have come to a point where I want to DCC some lashes ups..I have a number of Life-Like FA1/FB1, full metal chassis versions that I want to make as ABA and ABBA units in various New Haven Paint schemes.  What is the general consensus amongst  modellers in DCC..ing
these units. The ABBA  unit could be split into two units and consisted to operate as one unit, and I can use these as A-B  units if necessary . Now do I put a decoder in each unit or is it practicable to use one decoder for each A-B set..would a decoder also feed 3 units. The 3 units sets I intend to operate as one set.  I am not looking at doing 'sound' at this point
Any comments or other references would be appreciated.

Jim
Modelling the NH down under

[C855B]

I broached this subject in another thread last week, though in my case it was a single loco with separate, unlinked motors for each truck. Concerns were BEMF and current capacity. BEMF turned into a heated debate, where the practical conclusion was to try it and then turn it off if it hampered performance.

Current capacity is going to be your issue, and in your case probably more than mine. The smallest decoders are good for 1 Amp. Those FAs are great pullers being that they're heavy, but that heaviness and the big motor means stall currents are going to be on the high side - I would hazard >500mA at stall. Two of those would probably fry a decoder, three is out of the question.

You have piqued my curiosity with this question, however. I haven't converted my A-B pair just yet, so I might put them on the layout with a big train and measure current as they struggle up the 2% grade. But this is a couple of days away at best; maybe somebody will come along in the meanwhile already having done this.

[rrjim1]

Jim,     I own a three unit set of, FA2/FB2/FA2. I installed a early Digitrax decoder in the dummy B unit and ran wires just above the couplers to both powered A units.   These are older Life Like locos with plastic frames and lead weights. The stall current for these two powered locos is well below the 1 amp rating of the decoder. I would test your locos to see what the stall current is and if both locos add up to well below the 1 amp rating then your good to go for a two unit, one decoder set.       

[thomasjmdavis]

Thanks all, this is a very timely thread- I have many of the same questions being addressed here.  One other thought I have had is whether I could not save some power by "dummying" some B units in passenger consists.  I have tested many of the trains I will be running on 2% grades (as steep as any I will likely have on the layout being planned) and 2 units (Kato EMD Fs, for the most part) will pull these trains without problems, but in some cases, 4 units will be necessary to be accurate to prototype.  This could allow me to use a wider variety of decoders, space for bigger speaker if I go with sound, etc- because the decoder could be fit into the "dummy."

Which leads to another question- is there a difference in power rating between an HO and an N scale decoder? Or is the difference just physical size? In a consist of 4 units (3 powered units and one dummy) would there be any advantage to shoehorning an HO decoder into the dummy?  And is this one of those cases where the HO might be less expensive because it is less "miniaturized" and higher sales volume?

Thanks all

[jdcolombo]

Which leads to another question- is there a difference in power rating between an HO and an N scale decoder? Or is the difference just physical size? In a consist of 4 units (3 powered units and one dummy) would there be any advantage to shoehorning an HO decoder into the dummy?  And is this one of those cases where the HO might be less expensive because it is less "miniaturized" and higher sales volume?

Thanks all

In general, larger physical size = more current handling capability.   But don't rely on a manufacturer's designation that something is HO or N or Z.  Instead, just look at the specs.  Every manufacturer tells you what the maximum current capability is for their decoders, regardless of physical size.

As for using a single decoder to power an AB or ABA engine set, remember that in addition to the motor, you'll want to add in any lighting effects.  Usually, this isn't much - maybe another 20 - 40ma.  But if you have headlights, Mars lights, beacons, etc. all going at once, it can add up.  Also, I'd only use a single decoder if the engines in question are already decently-matched speed wise.  This ought to be true for AB sets from the same manufacturer, but not always - sometimes they change motors between model runs, and sometimes you just get one that runs faster/slower than anything else.  I have a nearly-complete set of NS Heritage units from Fox Valley, and while most of them run at pretty much the same speeds, my Wabash unit tops out at about 60% of the top speed of the others.  I have no idea why - I've disassembled it, cleaned it, checked to make sure the trucks roll freely, checked the driveline (it doesn't make any more noise than the others), etc.  My conclusion is that this one just got a "slow" motor.  If you can run two units together on DC successfully, then you shouldn't have problems running them from a single decoder.  But you can't always assume that this will be true, even when dealing with similar models from the same manufacturer.

John C.

[woodone]

Tom, don't know if you are working with HO or N scale with these.
I have done N scale units ( A &B ) with decoders in each. I just address them to the same address and speed match.
I have a friend that wanted to make a Kato B unit into a dummy. I did that by removing the motor and all of the gears in the trucks.
I ended up machining most of the metal from the chassis to remove weight. The dummy B unit was too heavy to pull with out losing too much power that the A unit had.
Has for decoders= look at the amp ratings of the decoder- Some of the new ones are very small with a 1 amp rating.

[Jim Costello]

  I agree with all the comments above. A decoder in each unit would be easier to install,they just have to be matched.
  All of the locomotives I have are powered and being wide bodies a larger decoder could be placed in a unit. My little research at this time shows that the majority of decoders that would fit are rated at 1amp continuous with 2 amps peak.
  I doubt that in my situation I would being pulling a lot of current( still have to test of course) as the layout is reasonably flat and not big loads...I just want to give the effect.
 
  Thanks
  Jim
Modelling the NH down under


 

[peteski]

Decoders (non-sound) are so inexpensive nowadays that having a decoder in each model would not be a big financial burden. It would also maximize the flexibility and tuneability of each loco in the consist.

[Greg Elmassian]

You state as a downside of a decoder in each loco: "A decoder in each unit would be easier to install,they just have to be matched. "

But not all identical locos run identically, so just running a bunch from the same decoder does not guarantee they are all moving at the same speed.

Greg

[thomasjmdavis]

My thinking was not so much to save on expense of decoders, I had 2 other reasons for wanting some non-powered locos.
1. My newer F units are DCC compatible, but several older ones are not, plus some Atlas "classic" GP and RS units.  So the plan was to mix and match shells on the DCC frames, and then create dummies from the non-DCC frames.  I realize that I could have the frames machined, but that seems a lot of trouble to go through for 30 year old locos.
2. Concern that if I have several 3 and 4 unit consists, and a couple switchers, RDCs, running simultaneously, plus train lighting (lots of passenger trains)- it is going to take a lot of power (by N scale standards)- so thinking about power supply size and number of power districts required.

I had not thought about the weight of the non-powered units as being a problem, but thanks for the heads up on this.  I will do some testing before I commit to be sure that the loco consists can handle the trains and grades.

Lots of good advice, thanks everyone.

[peteski]

We are in N scale. Each loco usually uses less than 0.2A under load and full throttle.  LED car lighting usually doesn't need more than 0.05A per car (usually even less).  That should not be a problem for most DCC boosters or circuit breakers.  Of 0 gauge modelers can run multi-unit lashups on DCC (with each loco using up probably couple of Amps), we should not have a problem in N.