Synchronizing Loco Speeds in a Multi-unit Diesel Consist

we need more info Ed. are you referring to DCC or DC or some other control system?

you can speed match DCC equipped engines by adjusting each engines speed tables for start voltage, speed curve, etc. through programming. it will be a hit and miss procedure with each engine. you'll have to determine a baseline with one engine and adjust others to it.

for DC engines the simple solution is to have indentical drives, adjusting speed then becomes an issue of adding resistance to the faster engine, usually with a resistor.

You could re-equip your Diesels with three-phase motors and run them from one synchronizing circuit. The motors you need are called "brushless" in the vernacular of the Radio Control model train crowd.

PRR Man,

The engines are DCC equipped.

Thanks,

Ed

then dig out your DCC system's documentation on adjusting speed tables and reprogram the decoder.

Ed

If you are thinking about speed matching several units of an ABA set from the same manufacturer with the same decoders, most time there is nothing you'll need to change. I've installed QSI Rev-U's in ABA or AB sets from Overland, AtlasO, and Weaver and didn't have to change a thing speed table wise. But if you need to speed match diesels with different drive trains/motors, such as a AtlasO China drive diesels with a single motor horizontal drive Overland, you will need to play with DCC speed table settings.   (I don't worry about this as in my 1952 era the PRR ran diesels in matched sets.

 Should you wish to speed match DCC equipped locomotives with different drives (gear rations or motors),you’ll need to set up one locomotive as your standard (you could have one for freight and another  passenger).  Tune your “standard” locomotive  using the speed table CV’s so that it starts at speed step 1 and travels at a top speed you desire on speed step 28.  Then performance match your other locomotives to it by playing with their speed table CV's.   Put the locomotive you want to configure on the same track as you "standard speed" locomotive.  Set up a DCC consist for the 2 locomotives with the one to be adjusted as the lead unit.  Run the two locomotives back and forth  (uncoupled)  to see what changes you need to made to bring the new unit close to the performance of the “standard” one.  Use Programming on the Main (Ops mode) adjust  the CV’s.  Verify your adjustments by again running the 2 units consisted but uncoupled - they should chase one another around the railroad at approximately the same speed.

MTH's DCS optical tachometer technique for speed regulation is decidedly better than  DCC's .  Matching speed of consisted (lashed) locomotives is inherent in the MTH system as you enter the desired speed on the DCS throttle - not a speed step.   MTH has patented it’s DCS speed setting design, so DCC manufacturers are unable to revise their systems to match measured  motor RPM to scale track speed .  Those of us who value DCC’s broad market availability and lower price over DCS’s features will just have to play with CV's for speed matching. Fortunately it's isn't difficult once you've done it a time or two.

Ed Rappe

You do not need to match the speeds of individual locomotives a multi-unit consist. All you have to be sure of is that none of the units are spinning their wheels.

If you MU a "fast" engine with a "slow" engine, all that happens is that the faster locomotive pulls on the train a little harder than the slow one. As long as the "fast" engine is not slipping its wheels, you can run engines like this together all day long.