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What Train Gradients for Double Header Locomotives?
Although Scott focuses on HO scale, the answers to his question will no doubt be of interest to folk using other scale. Scott asks readers:
“Can double locomotives help out in steeper grade? Can you have two trains hauling many boxes? What is maximum number of boxes can one train can haul? Two trains? On gradients? Thanks.”
12 Responses to What Train Gradients for Double Header Locomotives?
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Hi Scott a lot depends on gradient and what brand of loco you run. I run n scale and my layout is the Rocky Mountains,I try not to make my gradients steeper than 2.5%.The hieght of my track ranges from base level to 16 inches high.i use Kato diesel F7A coupled with F7B, I run 4 seperate set ups of 2 F7A+ 2 F7B joined together and they haul upto 50 wagons each set up.The reason I use Kato is reliability, weight of loco and pulling power which I find far superior to most other brands they are also very smooth and quiet.
Exactly as with real trains, having more locos pulling means more wagons can be pulled.
Steeper grades require more force to pull a long train, so extra locos will help.
Locos are generally “over-powered”, in the sense that the wheels will spin (not stall) if there is too much weight holding them back.
But a loco’s traction can be increased distinctly by adding weight to it, which increases the force holding the wheels onto the track. (Many cheaper locos have lead weights inside for this purpose.)
(Better locos have a more solid metal chassis, which does the same job.)
If you have a force meter (like a small spring balance), you can determine the traction available from a loco (the amount of force it will exert horizontally).
(This experiment can also be done with small weights hung on thread, the loco on a level section of track, seeing what weight can be lifted.) Record each loco’s traction in gram-force units.
You can weigh your freight and passenger cars, and using the basic principles from your school physics text book (inclined planes etc), you can calculate the force required to pull a certain weight of train up a certain slope. (But allow some extra force to overcome frictional losses and inertia.)
Just a little more study, and you will soon be a fully qualifed (model) railroad engineer !
A small point – the weight a loco can lift vertically, using a pulley, thread & weights, is a lot less than it can haul up a given slope or even on the level; it’s simply a measure of the loco’s adhesion that can be compared to that of other locos using the same rig.
There is always the method I use. Give a go and if only one loco is used, and it stalls, reduce the number of wagons. Similarly with two locos. The one thing you need to watch out for is if a train is very long and the curve is sharp, the locos can pull wagons off the rails trying to straighten the line between first and last wagon.
As well as risking derailments on sharp curves, you will find that any curve will introduce more friction than a straight incline – the tighter the curve, the greater the friction.
Scott,
In much of today’s modern railroading you will find at least 2 engines pulling on level ground even if the load is small. First it gives more traction power if the rails are slick and second each engine has it’s own compressor and that means a spare if a compressor goes out But for long trains it just means more air for volume for for the train load in an emergency braking situation . AMTRAK for instance runs 2 engines even in the mountains in the summer times but even for the same 9 cars during the winter the train will many times have a third engine. It just makes each engine not have to work as hard and gives more traction power. Now the City of New Orleans has been spotted running with only one engine even with snow but it also runs on pretty level tracks.
But for model railroading the model engines even the best of them do not have the power,weight, or traction of the real thing. ROSE HULMAN University students in their model railroad club decided to scale weight 2 fully loaded hoppers Those 2 cars took all one engine could do to pull them by themselves. I occasionally will pull some long 30 and forty foot model trains and those are usually needing another engine if more than that on level ground 30 or 40 cars is only a half or third of the real trains using 2 engines. So I am going to need a couple of helpers on a grade if the load is more than the engine I am using can handle. Just put the second or third engine on and team them up. You are not wrong even for a short road and if you are running DCC then setting them up as a team or consist is even better. I have seen 8 Union Pacifics pulling a totally empty 80 car stack train carrying only heavy air (most likely shifting cars and engines to areas where needed) But whether you are running DC or DCC you want the team of engines pulling the same or nearly so otherwise the engines will buck each other yanking on the couplers in other words you want engines that will run nearly the same all through the speed scale.
The actual Ringling Brothers Circus Train will have 2 engines but the train is a mile and half long. That would be a about equal to 80 auto rack cars that are 86feet long each. It not just the amount of cars you pull, it is the drag and friction.
I pull a Auto rack train the length of my garage and it pulls fairly easy. But I pull a 38 car Caboose Train on New Year’s Eve that is shorter but because of the wheels even though the cabooses are shorter and the train is shorter there are more wheels meaning more drag.
Put the extra engine on and have fun with it. Newman Atkinson
As far as gradient/rise and run/slope, incline, decline definitions goes the idea is the same.
The track work has to be perfect to maintain a near linear climb with head end locomotives.
If you can use “Frog Snot” to coat the wheel sets it will help you maintain traction your local hobby shop should carry it, if not you can order it directly from them.
The least amount of curvature in a 2-4 percent grade is your friend. If you can climb the side of a mountain with a switchback it will help you with any size consist as the locomotives will not be
fighting with each other during the climb.
If you can put three or more locomotives on a grade with the proper amperage and voltage to feed the locomotives without causing issues with the remote controls if used to operate the train on a grade.
Mountain grades have been conquered with switchbacks using manual labor, picks and shovels and horse carts.
If switchbacks were built today using modern civil engineering methods and construction materials tunnels would be a thing of the past.
Being a retired miner by profession I can tell you railroad tunnels are a waste of money and all of them even the newer tunnels( bvuilt after 1950 are one earthquake/roof failure) from ruining all the Class One Railroads.
The problems of operating 2 or more locos on the same train apply to level track as well as inclines; mid-train or tail-end helpers (“bankers” here in UK) need to be matched carefully to the head-end power units. I’ve watched a fellow club member practically pulling his hair out at the last 2 meetings trying to do this with his DCC models; it’s practically impossible with DC or analogue locos, I think. The central problem of how to deal with gradients is one of multiple variables:
Severity of the grade
Number of powered axles
Weight on the powered axles
Number of axles in the train
Weight of the train
Nature of the bearings in the train’s axles
Material (therefore coefficient of friction) of which the rail is made (steel, plated steel, brass, nickel silver)
Material of which the wheels on the powered axles are made (as above)
Material of which the train’s wheels are made
There may well be other factors; the point I am trying to make is that there can be no simple answer to your question – you simply have to experiment. People do use gradients as steep as 1:30 (3.3%), but I think 1:40 (2.5%) is a desirable maximum. However, there is an interesting product you can use to improve adhesion of a given loco on a given gradient; it consists of very thin pieces of steel that you lay under the track, together with small magnets that you attach to the underside of your locos. Tests conducted by a magazine in the UK have shown that trailing loads can be increased by between about 10% and at least 40% (I have forgotten the precise numbers, and they seem to depend largely on the nature of the locomotive being treated). The system is called PowerBase and is produced by an Australian firm called DCCconcepts (no connection).
One more thing: make sure your controller is sufficiently powerful to run two (or more) locos together. Some small cheap controllers will overheat and cut-out if too many locos are driven by them at one time.
The controller output current must be equal to, or greater than, the maximum current taken by the locos it is driving. So for example, a controller cabable of supplying 1/2 amp will run up to two locos each taking 1/4 amp.
Hi Scott I posted earlier on you wanting your loco to pull more wagons up gradients.there is a product out that will eliminate your problem with ease,I have tried it and it has doubled the pulling power of my locos it’s made by DCC Concepts in Western Australia it’s called Powerbase check it out its worth a look.
I like this question because I probably run some of the heaviest HO trains out there. I love all of the older die cast metal cars and Loco’s: Varney, Hobbytown, Joe English, Penn Line, Bowser, Gilbert, Ulrich, Model Die Casting, Model Power Metal Train Series, New One, & Brass. Almost all include metal wheels and trucks (more weight & drag). My layout also has two steep grades made with Woodland Scenic’s Foam Grade kits. When running DCC, if a train stalls on the grade, I command helper engines to come to the rescue, and when the train reaches the summit, the helpers can go back to the siding. Many of my trains run multiple engines anyways. The best traction locomotives are the ones that have “Sprung” drivers, or traction tires. When running multiple Loco’s the biggest challenge is matching the loco’s speed, as many will be out of sync. With DCC, you can adjust the decoders speed tables & parameters to better accommodate consisting, though I have not done that. You get to know what your equipment can handle after much use, and just how much train they can pull up a grade. With DC, pretty much the same identical locomotives ( Same Mfr & models) can be run together just fine. Running multiple units makes for a more interesting train, better too much pulling power, that not enough. It’s almost like a tractor pulling contest.
I like having the hills on my layout and found out the hard way that my little engines can’t pull the hills when pulling a number of cars and solved the problem by cheating , I raised up the lower end of the hills by shimming the platform , reducing the grade , takes a good eye to see that my layout isn’t level but now my little engines car pull the hills ,