Power balanced DCC Motor Wiring

[gman1]

Howdy All,
Could use some advice on how to properly wire motor blocks to a dcc decoder. Up till today, I've always replaced all Aristocraft or USA Trains boards (Traditional Method) and just wired lights and motors directly to the dcc decoder. This has worked "pretty well", but I think the motor install has been flaky and I wondering if I've inadvertently by passed needed components to keep the motors "power balanced"...meaning that both motor blocks turn at the same rate, despite more load on either block. I use Soundtraxx TSU4408 or LokSound 5 decoders, no errors as far as I can tell. My current locomotive I'm working on is an Aristocraft SD45, from 2004. I saw a mention of voltage regulators on Greg Elmassian's site and now think that maybe voltage regulators are need to be in the circuit. Any pointers, schematics, etc any has would be so helpful.

Thank you,
Greg
ps. Im not an EE so please don't judge me for my rookie'ness ;-)

 

[PhilP]

If you take an old, worn loco, with old worn motors, pitted wheels, etc.
Then DCC won't fix the fundamentals..

Regulators are used to give a known supply to things like smoke generators, sound cards, and the like.

I think you may have found an old motor, which may have caused whatever your problems have been?

PhilP

 

[gman1]

Phil...many thanks for the note. I put new motor blocks in and result is the same. Here's a graphical representation of my situation.

I hope this makes sense. thanks, Greg

 

[PhilP]

Thanks for the diagrams, I understand what you mean now..

Short answer, you can't do this with a single decoder, and without clever programming, could not do it with separate decoders for each block.

In the real world, there is sophisticated feedback and motor control, and individual drive-chains are all 'drive by wire'.
As an example: Here in the UK we have loco's where the electronics will allow about 3% slip, without axles breaking-away and spinning out of control.
Seeing one of these loco's pulling a ballast train out of the quarry, at night, with sanders and wheelslip is spectacular!

Without each motor-block being controlled independently, and the controllers 'talking' to each other, you won't be able to achieve this on your model.

Best you can do, is get the loading (weight) about the same over each motor-block.
It should not do any damage to motors, or decoder, and the 'magic' of the back-emf generated in each motor will help to balance the load.

The friction / rolling-resistance (with both blocks on the track) will also tend to even things out.

You can also check coupling heights:
If the coupling on the loco is higher than the formation being pulled, it will produce a downward force, loading the rear truck, and slightly unloading the front one. - Thick badly balanced trailer-load behind a road vehicle.

Hope that helps?

PhilP

 

[Diesel2000]

The decoders you are using are single input motor connections - meaning they only have 1 set of terminals for motor wires regardless of how many motors you have the loco. Therefore as you can imagine there is really nothing the decoder can do independently in terms of load controlling the individual motors, and there is no circuitry that you can install between the motors and decoder that will accomplish this dynamically. In the situation where 1 motor block might have more 'load' I'd imagine that would be incredibly brief, unless at very slow speed, which has its own decoder challenges, unless there is some drastic weight difference over top the motor blocks.

Over time motors will wear differently and thats usually why when doing conversions of older/well-used 2 motor block locos both motors will need to be replaced so as to bring them back in line to behaving with the same characteristics at the same voltage. I've seen situations where 1 motor is turning at a much slower speed, which obviously causes drag.

Some decoders do support separate connections for 2 motors (Marklin LGB MSD3, Massoth Onboard), but thats more just for ease of wiring. I'm not aware of decoders that are actually controlling the motor outputs independently and dynamically together. I'm sure, however, that this could be a future possibility down the road for some decoder manufacturer.

 

[Software Tools]

meaning that both motor blocks turn at the same rate, despite more load on either block.

Unless something very usual is happening, the mechanical load on each motor block is just not going to be materially different in normal model running. Perhaps you are overthinking this!??

 

[gman1]

Thanks to you all for the suggestions and helping to reset my expectations for getting both motor blocks to always "pull" with the same vigor.

 

[Paul M]

Unless something very usual is happening, the mechanical load on each motor block is just not going to be materially different in normal model running. Perhaps you are overthinking this!??

Unless you've done something drastic, surely the locos manufacturer has made some sort of allowance for this

 

[LGB333]

Thanks to you all for the suggestions and helping to reset my expectations for getting both motor blocks to always "pull" with the same vigor.

Greg - I just now read this topics threads. To reiterate what's already been mentioned, there's no adjustments using one decoder (the normal method) to compensate for a locomotive's two motor blocks not operating at the same speed. I always test a locomotives motor blocks' movement on a roller wheels test stand prior to starting the DC to DCC sound conversion, and if I find a problem with one motor operating slower than the other, I replace both motors.......you can't normally replace just the slower motor since it will likely operate faster than the other motor now. For long-term operating reliability when converting a well used locomotives to DCC sound, the best preventive maintenance approach is to install new motors which are not that expensive, @$53 in the USA. You don't want to have to disassemble your locomotive again, time and effort, to replace a used motor down the pike when you could have done it during the initial DCC conversion process.

 

[pugwash]

As above, I had a LGB 'Nicki + Frank S' which had a motor in the loco plus one in the tender. Being a two motor loco I was expecting some serious pulling power, but it didn't. I seperated the loco from the tender, put both on the rails and applied power, the loco ran but the tender stood still. I took the body off the loco and saw why, even though the loco and tender had motors plus power pickups the wiring showed that the tender power pickups were sending the power to the loco where there was an electronic board, this took the power from the loco and tender then sent the same power to each motor via the wiring between the loco and tender. Thus the tender was picking up power and sending it not to its own motor but to the electronics board in the (unattached) loco. I attached the loco and tender using only the wiring and tried again. Oh dear, the loco motor was faster and dragged the tender along, even though the tender motor was running. Simple fix, replace both motors with brand new ones (but keep the old ones as neither was dead) and everything worked perfectly.
Note this was analogue using EPL (I hadn't discovered digital back then) but I think the same principal applies here.