I was wondering: in real life, more locomotives on a train equals additional pulling power. Does that carry over into model railroading? For example, if I have two Athearn C44-9Ws elephant style, will they haul a longer or heavier train than just a single one?
Sure.
Just keep an eye on your power consumption requirements.
yes it works great for added pulling power…I use the tech II 240 MRC power pack and i can run 3 powered locomotives in the consist without over working the power pack…I do run them no more than about 30 minutes then pull them onto a siding to cool off for a few minutes before running them again…keeping the motors cool can really extend the life of the locomotives…I have an Athearn GP35 that is about 20 years old and is still running strong in a consist of 3 locomotives…chuck
It does up to a point - according to those who’ve tested such things you don’t necessarily get twice the haulage ability (won’t haul twice as many cars), you will get a distinct improvement though over one loco.
If the locomotives are extremely well matched, especially with respect to speed, then the pulling power of the two should equal the sum of the pulling power of the individual locos. Usually, however, there is enough difference between locos, even from the same manufacturer, that some of the tractive effort available is lost as the locomotives “fight” against each other. Unless the two are really mismatched you will get improved pulling power and it should be noted that speed, not individual pulling power is the governing factor. I have a small, brass 2-6-0 that has been remotored with a good quality can motor. While it pulls respectably for its size, it has nowhere near the pulling power of a pair of modified Bachmann 2-8-0’s. However, because it runs at a similar speed to the bigger locos, it can be used as an effective helper when a train is a few cars over the tonnage rating of the Consolidations.
Also, check out the poll on adding weight to locomotives.
Wayne
ive tried this on my DC 4x8-- just make shure the front loco doesnt go faster than the back one! you might break a coupler.
You want engines that are well-matched, if not identical. I commonly use my pair of Bachmann 44-tonners to haul freight around–on the prototype, 44-tonners and other small switchers were often MU’d to move larger numbers of cars.
You sure can. The biggest consist I run regularly is my AC6000 and 3 SD70MACs. Three giants and I’ve never put enough cars on them to even slow them down. However I was feeling a little silly one time and put the AC6000, the 3 SD70MACs and a GP20 on the front of the train. A Dash 9 and a SD45 in the middle and an SD60 pushing up the rear. This was at a guy’s HUGE layout and i was moving about 175 cars. A consist like that can’t be done on the average layout as it would overload the power supply, but this guy has about 20 amps available.
Oh by the way, this was on DCC so you can program all the locos to run at the same speed. I dont think you could do a consist like that on analog.
Actually Gearhead, you DO want the front loco to run faster than the trailing one, but not much faster. Having the faster one in front will maintain tension on the couplers so the slack isn’t banging in and out, especially on a downgrade. If you’re breaking couplers, you need to switch to the Kadee 40 series.
The other thing to consider on double heading is the cars and how well they track in long strings, plus your grades and curves. Too long and heavy a train can easily “clothesline” on a curve. You’re talking about double heading two 6 axle Athearn diesels, so you’ve got substantial pulling power there.
It is also interesting to try to match locomotives to be used as pushers on the rear of a long train. Excessive slack action or buff forces can quickly cause massive derailments, so it is helpful to have closely matched engines: in the event that there is a speed mismatch, the faster locos should go on the head end. This way, they will pull the part of the train that they are able to move and as they are slowed by the cars in excess of their capabilities, the rear units will “catch up”. I sometimes run an excess length coal train up a fairly long (about 45’) 2.8% grade, laid out on two horseshoe curves connected by a long straight and topped by a very wide radius (48") “S” bend. The cars are mostly Athearn 34’ twin hoppers with “live” loads with a car weight of 8 oz. per car. When the proper locomotives are used, 2 on the head end and 1 pushing, close observation of the train in motion reveals that the couplers of the front 2/3 of the train are in tension while the couplers of the rear 1/3 are under compression. This ratio varies depending on which part of the train is on a curve, etc. Unfortunately, when the train reaches the top of the grade, it has to stop as the track comes to an abrupt end. This winter I hope to install the upper deck of the layout and lay steel (nickel silver) to the end of the line. Until then, the train is forced to back down the hill.
While my railroad is a medium size, around the room type of layout, and the aforementioned operation works well, this pusher operation is the only place that I could see DCC being of use to me, and then only if there was a separate operator to run the pusher. In the meantime, I’ll continue to modify and tune locomotives to wring the best performance out of them.
Wayne
BNSF - I find there are two very distinct issues in double-(or more) heading.
One is when locos don’t have the sheer power to pull the cars (i.e. they slow down or just won’t go). It’s about the little electric motor’s power. It’s not good to ‘stall’ the engine, by the way, it strains the motor, and can create significant current draw on your electrical system.
The other is wheel slippage (typically seen more on grades). This is not so much about electric motor power – it’s that the wheels are slipping. The locmotive lacks the traction (not necessarily the power) to pull the cars. One solution for this is to add weight to the loco to pu***he wheels down on the track more. But the loco also has to haul that added weight, so this can be a bit of a balancing act – the whole “just enough, but not too much” thing. You can fix your ‘slipping’ problem so effectively that you create a ‘stalling’ problem for yourself as above!
But you asked about doubleheading - adding locos.
For the first - motor fade - adding locos distinctly helps. I saw this more with older locos with open-frame motors and worm-drive mechanisms. I have a couple old Varney engines that practically bog down trying to haul their tenders along! I rarely encounter this with modern 5-pole type motors: I have to add a truly excessive number of cars to have an engine start choking before wheel-slip sets in.
For the second - wheelslip - adding locos also helps, but I find not as much. I certainly encounter wheel-slip quite a bit more often than motor bog-down. And often what I see when double-heading this way is that the wheels are still slipping on both locos, but less so: enough weight is taken off for them to have some tractive effort come through. I’ve been able to eliminate wheel-slip only by coupling an inordinate amount of locos to the cars (e.g. I had 4 BLI K-4s coupled to 12 spectrum pullman cars and no wheel slip going up a 2.5% grade, but with 3 still had some minor wheel sli
I’ve read that the magnets on open-frame motors can become weakened over time. This may explain why a loco bogs down under load. I’m told that it’s possible to remagnetize them, but I don’t know how. I had a couple of instances where an Athearn diesel, remotored with a large Sagami can motor, bogged down on a long grade with an excess tonnage train. I was running tests to determine tonnage ratings for various locomotives on different divisions of my layout and instead of adding one car at a time, i added several. The loco started the train but began to slow as it got into the grade and finally stopped. However, it didn’t spin its wheels at all and I quickly shut off the power. ( While wheel slip is not desireable, it is more of an annoyance than anything. A stalled motor is not good at any time, and it doesn’t take long to damage or destroy a motor.) Now it so happened that I was also testing different throttles at the same time. When the stall occurred, I was running an SCR throttle ( A.C. in, D.C. out and contrary to what I’ve heard, never a problem with motor heating). It turned out the the reason the motor had quit was not enough electrical power going in. The A.C. power source was both too low in voltage and amperage output: after going through 25’ of throttle cable for conversion to D.C., and then back another 25’ to the buss wire, there wasn’t much left. I switched throttles to a MRC handheld powered by a Controlmaster 20, and while the loco still couldn’t climb the grade, at least it sat there spinning its wheels. I have since upgraded the A.C. power supply and have not had the problem re-occur. However, the SCR’s will neither accept nor put out enough current to power long, heavy trains handled by multiple units capable of moving the train, so these throttles, with their precise control, are limited to light trains or switching moves.
Wayne
MU’ing a train does indeed increase the pulling power of the train. As has been noted you have to worry about matching up the locomotives together for similar performance and speeds.
If the locomotives are matched up to approximately the same speeds, and most importantly hit wheel slip at approximately the same throttle setting, then you’ve got a good match. Once the wheels start to slip on one, then the performance of the entire combinations starts to dramatically drop off. It’s into a weakest link calculation type of thing.
As long as you can spin the wheels under full throttle, you can add more weight to a locomotive. So far I haven’t hit that limit. If I used die-cast lead bodies on my diesels then maybe I’d get there… 
Mark in Utah
Yes as many people have pointed out, the closer the two (or more) engines are to running at exactly the same speed (and on DCC, having the same rate of acceleration and decelaration) the more power the combined units will generate. An added bonus I find is two + engines that are fine tuned to run together also seems to make a train run smoother. I find if I take a train (like say a short wayfreight) that one engine can pull, it will be more affected by grades (slowing down going uphill, speeding up going downhill) than will two engines together on the same train. (This is in situations where neither engine has Back EMF, obviously that would affect things too.)