Most of what I've read about powered FB units involve the engines' ability to pull more cars. However, I wonder if there are other differences. For example, I like to run trains at very slow speeds. Does running a train at a slow speed with two powered engines make it run more smoothly?
That's a tough question. If you are running your trains with DC, it would depend on how well the A and B units are matched. Are they the same make, the same generation of the model, how well have they been maintained, etc. [semi-smooth]
If you are using DCC, all the above apply, but you can tune each locomotive to match each other. This can get time-consuming. [smooth]
If you are using RailPro, once you 'link' the locomotives, RailPro does all the speed matching and tuning for you, on the fly. [smoothest]
Shock ControlDoes running a train at a slow speed with two powered engines make it run more smoothly?
.
My experience is that a single locomotive with good flywheels and electrical pickup will run perfectly smooth.
Adding a second locomotive cannot make this better, and could make the consist operate jerky.
-Kevin
Living the dream.
My 2 cents in addition to the experts: it depends on the drive.
If you cannot fine-tune the slow motor speed (or one or both motors cogs outside the physical ability of motor control or flywheels to overcome it, which if so means you need a final-drive gear change to give higher rpm at slow speed) then it is likely 'two is not better than one' especially if your equipment is light and longitudinally loose so it shows the effect of the drive fluctuations.
As with duplex steam locomotives, two 'jerky' engines out of phase can smooth out effective torque at the rear drawbar where it counts. The problem, also as with duplex steam locomotives, is that with both engines IN phase you get much worse surge...
My opinion is that if you like running at very slow speed you rework both the FA and FB to where, say, top speed at 128 steps corresponds to prototype 65mph; less if you have a 'drag' or helper prototype, which will be smooth down to almost indistinguishable HO speed (the tip of the minute hand on a wall clock may move faster) and incidentally improve TE.
I have been a great fan of coreless motors since reading an article in MR circa about 1971, which covered not only using the motor type but the use of Delrin chain instead of just gears in a slow-speed final drive. All these years later that is still a high-water mark for glass-smooth running right down to 'too slow to see'.
Meanwhile, remember that any Alco cab would have significant restrictions about running slow while developing any significant TE due to DC traction-motor restrictions. This might call for 'more units' not for the added engine horsepower but the larger number of motors (Alco to my knowledge not having marketed road slugs or the alternative to MATEs). Now, that's prototype only and there are plenty of joys in Carly-Simon-ketchup-commercial-slow model running, so use your own judgment.
Shock Control Most of what I've read about powered FB units involve the engines' ability to pull more cars. However, I wonder if there are other differences. For example, I like to run trains at very slow speeds. Does running a train at a slow speed with two powered engines make it run more smoothly?
Another thing to take into consideration is that a dummy locomotive is the same as a powered unit, minus the drive mechanism. Compare the weight of the dummy compared to a powered unit. Pulling a dummy can/will reduce the number of cars the powered unit can pull; it's just dead weight.
Marlon
See pictures of the Clinton-Golden Valley RR
When your track or wheels start to get dirty the dirty spot is where your locomotive will stop while you are stopping your train. Then when you try to start it moving again you have to give a nudge to your locomotive to move it past the dirty spot. One of the best reasons to have two powered locomotives is that one locomotive can give the nudge to the other for you. If you have matching locomotives then their speed should be the same, until one starts to get dirty, but that is what happens with electric trains. If you can afford powered units then buy them. They do add horsepower so you can pull longer trains and go up grades. Dummies were meant to be a low cost alternative. I myself have both but I try to always have two powered units together with some dummies as well. Most of my trains have three or more locomotives. Some as many as five or six because I model a mountain pass.
Lone Wolf and Santa FeWhen your track or wheels start to get dirty the dirty spot is where your locomotive will stop while you are stopping your train. Then when you try to start it moving again you have to give a nudge to your locomotive to move it past the dirty spot. One of the best reasons to have two powered locomotives is that one locomotive can give the nudge to the other for you. If you have matching locomotives then their speed should be the same, until one starts to get dirty, but that is what happens with electric trains.
If you have matching locomotives then their speed should be the same, until one starts to get dirty, but that is what happens with electric trains.
Thanks, this reinforces what I'd suspected.
doctorwayneI'm also curious as to what you consider to be very slow speed, and why it's desireable.
I would consider the target speeds to be prototypically reasonable for what you may expect during the 1950s in an area with a combination of street crossings, curved tracks, and commercial/residential zoning.
As far as desirability, I have a relatively small space to work with, and I find the slower speeds create an illuson of greater distance. Also, I like to listen to music while the train is running, and it is quieter at a slow speed. Finally, seeing the train go by slowly, with all the railroad names and slogans easily readable, offers a calming contrast to our short-attention-span society in which everything moves too rapidly.
All my engines are powered. Most of my trains have multiple engines.
The only dummy on my layout is me.
Shock ControlI would consider the target speeds to be prototypically reasonable for what you may expect during the 1950s in an area with a combination of street crossings, curved tracks, and commercial/residential zoning. As far as desirability, I have a relatively small space to work with, and I find the slower speeds create an illuson of greater distance. Also, I like to listen to music while the train is running, and it is quieter at a slow speed. Finally, seeing the train go by slowly, with all the railroad names and slogans easily readable, offers a calming contrast to our short-attention-span society in which everything moves too rapidly.
Okay, that makes sense. There are those who strive to get ultra-low-speed operation, where the locomotive takes minutes to move from one tie to the next. I do appreciate the quest for improved performance, so I'm not criticising that approach, but for my layout, it's not something I'd find useful.Modern locomotives, with computer control of engine power and of the electrical distribution to traction motors, are capable of extremely slow movement. I've ridden in the cab of one which was pulling a coal train through a continuous loader: looking at the scenery out the side window, there was no sensation of movement unless you looked down at the ground right below the window.
The photo below shows some street running, and speed was comparable to walking...
...and is similar to what I'd run when servicing local industries.
Wayne
Like Wayne I run DC, and like Wayne I have no need or concern for ultra slow speed.
Using Aristo Train Engineer wireless throttles I find that all my locos start and run at speeds in the 2-4 smph range.
More importantly, they will continue running at what ever speed they start at, and not be subject to stalling at every slight increase in resistance as I have sometimes seen with DCC.
I run lots of multiple unit diesels, most are matched in that they are same brand/drive. No special effort is taken to make them run exactly the same speed, they all run smoothly enough as sets and most of my trains require more than one loco.
I also double and tripple head lots of steam. Sometimes matched identical locos, sometimes not.
It is all about gear ratios and starting voltages. If those two factors are close, they will run together.
Example: my Spectrum 2-6-6-2's run just fine with Proto2000 2-8-8-2's.
Sheldon