My previous post drew some really helpful answer and the next one will probably bring another round the same so here goes. OK, lets say I have the room large enough to put a mainline of 4 miles in HO, for practical purposes what would be about the limit using the diesels like the Alcos, EMDs, or even the new genration now been used??? Second part would because I have seen one advertised as able to pull 99 cars on a straight and level section but wondered would it pull all of them as it went around even a slight curve??? thanks in advance
How many cars you can run depends on the cars and the power and the trackwork. If it is level, with big 40" radius or bigger curves, you could run very long trains, 150 cars or more. Just keep adding engines until you can pull it.[;)] The cars need to be free-rolling.
As for pulling around a curve, it depends on the tightness of the curve, and the cars. Friction increases going around curves, as one of the wheels will be sliding or dragging a bit. An automobile has a differential to allow for the different wheel speeds caused by the different distances traveled, but a railroad wheel set doesn’t. If the curve is too tight, you could stringline the cars. They would fall towards the inside of the curve. You probably wouldn’t be able to pull as many cars around the curve.
Interesting.
In HO, I have a 44 inch radius curve on a level surface. I chose to elevate the curve about .030.
I run short consists - around 8 cars + caboose + steamer. The steamer has sound and I can hear it “struggling” slightly as it rounds that curve.
Regards,
A little documented facet (trivia?) about railroad wheelsets is the differential factor. If you look closely at the wheel profile you will see that there is a slight taper from the rim to the flange. Essentially what happens is that centrifugal force on the car pushes the wheel sideways a little bit, so the outer wheel is running on a slightly larger diameter than the inner wheel. This results in a slightly larger circumference which in effect reduces wheel slip, and compensates for the slightly greater distance around the curve.
But for your concerns I would suggest that all of your cars are properly weighted and have metal wheelsets for smooth free running. I have pulled 65 car trains with 4 unit Stewart FT set on a club layout having many 24"r curves and 1.5% grades with no problems. jc5729
Don’t like to contradict a working railroader, but this ain’t necessarily so. The equivalent of the automotive differential is the three degree tread taper molded into railroad wheels. On a curve, the entire axle and both wheels shift outward. This effectively changes the radii of the wheels, larger outward, smaller inward, causing the wheel set to roll in a curve - hopefully, a curve of the same radius as the curve in the track.
If the curve is sharp enough, the taper can’t take up the slack and the flanges contact the railhead. On the prototype, this announces itself to the world with a characteristic screech of metal on metal if flange oilers haven’t been installed. Unfortunately, in model practice, most curves are sharp enough to bring the flanges into play. That causes all of the results described in the quote above.
As far as how many cars can be pulled on a model railroad, The Model Railroad Club, in New Jersey, once ran a multi-hundred-car monster in HO. In N scale, the founder of the N-trak system pulled an equally preposterous train with specially modified locomotives. The prototype record was set by the Norfolk and Western. IIRC, the limiting factor in all of these efforts was coupler/drawgear failure. Anyone who knows exactly how many cars were involved in each is welcome to share that info with the rest of us
Although another user recommends “properly weighted” cars - probably he is thinking of NMRA recommended weights - I am doing exactly the opposite. My smallest curve is 80" radius/ 160" diameter - H0scale - so I was very happy being able to remove all extra weights from all of my cars, or to simply ignore them by building kits. I am using metal wheels and metal couplers - that adds weight where it is needed - and am running 120+car trains with ONLY ONE engine. All my engines are steamers, and so I am probably as prototypical as one get up to date. And I feel that even somewhat smaller curves - say down to about 60" wouldn’t be any problem as well. And since you wrote that you have 4 scale miles you should use such large curves.
FOUR MILES?? that’s 243 feet HO around a basement 40’X80’. Thats 81 pieces of flextrack mainline alone. SIZE of ROOM limits layout (if $$ don’t). SIZE of LAYOUT limits curves, and
SHARPNESS of CURVES is what limits locomotives. ALL locos run on straight track. It’s primarily a law of physics. WEIGHT and traction of engine vs. WEIGHT and friction of what’s being pulled. GRADE dramatically increases weight being pulled
The REAL WORLD will have OUR train length determined by the length of our ‘passing sidings’. An 8’ passing section will be 6.5’ when clearing turnouts. Thalt’s 5 full length passenger cars.
It was common in the heavyweight passenger era for one engine assigned to 6 - 8 cars
I say run what you want to see, and what your trackwork will allow. I run on a club layout, and most of the trains I run are up to 30-40 cars, and with 30" curves, use 3 locomotives (to reduce engine draw). When I feel like running a 100 car train, It can be done with 3 locos, but they tend to heat up under load, so I run 5 up front, or place two helpers in the middle or at the end of a long train.
I can pull a cut of about 20 cars with a four axle SW1500 switcher on flat and level track, though if I am navigating a number of turnouts, the wheels begin to slip.
Jeremy
Don Gibson put his finger on the crux of the issue. The limiting factor in train length on a MRR tends to be siding capacity unless you’re dealing w/ grades in excess of 2.5% (that is to say, unprototypical except a a very few very exceptional cases). Most of us want a train length that APPEARS prototypical (yet another case of selective compression). I’ve decided that a good length to give the appearance of a full size train is 40-50 cars. we’re obviously talking frt trains here. I run actual car count psgr trains from a 3 car Pioneer Zephyr to a 16 car Empire Builder. To ascertain the power requirements, I build a test helix on a 1.5% grade (pretty steep on the prototype). I found that 3 powered Athern F-7s (the old Blue Box “Super Power” with the bigger wieghts) would comfortably handle 50 car trains up the grade around the 42" curves. If I decide I want an extra unit for appearance I add a dummy.
I am aware of the tapered tread on the wheels. I figured that with the sharp curves us modelers have, it doesn’t help enough. You are still using the flanges to keep it on the track, with the resultant drag. Anybody try a HO scale flange oiler?[%-)]
I have run 90 cars at the club, with 3 Atlas GP40s, or 2 Athearn SD40-2s ballasted to about 21 oz each. At Trainfest we ran about 150 ore cars behind 2 P2K SD45s. 150 ore cars or 100 regular cars is about the limit we can run at the club without midtrain helpers. Too many curves and hills at the same time. About 360 degrees of curveature in a “P” shape while pulling up 1 to 1.5% grade. Free rolling cars are a must. Sometimes I will run a Centerline cleaner car at the rear, to keep the train streched out coming down hill.
The N & W used 6 SD45s, either 300+ or 600+ cars, I don’t remember offhand. The Austrailians currently hold the record.
I keep my consists under 30 cars. I have built 30+ cars but it tends to “Consume” all of the availible railroad to deploy it. You are going to be limited by how much money is on hand for the track, switches etc etc…
You can horsewhip a switcher into shoving 15+ cars up a slight grade if you wait long enough for the wheelslip to take hold. I have a team of two switchers that will have no trouble with 15 cars but they are also road switchers and might as well keep going out of the yard to Falls Valley with it’s train =)
I know of a local HO scale railroad that keeps it’s lengths down to about 8 cars or so. They run in a earlier time and dont need such long trains. A 4-4-0 pulling 5 cars to town is a train. Imagine trying to hop car to car setting brake wheels to stop the train at the next station with one of today’s 70 mph consists with over 60 cars?
I have moved 70 cars with double headed articulateds and since I was dealing with a mixture of horn-hooks and kaydee’s along with the awful plastic wheels (Anchors) and ground the rails to fine powder only to see the slack run in shove both engines out of control =) Now it’s been 20 years and my ABBA unit will take care of that onery train no trouble at all… except for power. I wont try it on the Tech 4 1.6 amp throttle =)
On our club N scale layout, we use a formula that gives manageble trains that we feel are realistic to watch and handle, we have a flat division and a mountain division, the ruling grade on the mountain is 3%, in looking at prototype practices and model dynamics we found that a 1500 HP F unit will easily outpull a 3000hp SD40, real weight and tractive force doesn’t figure into the equasion in the model world.
Basically, we have settled on a formula of two wagons per locomotive powered axle on the mountain division, and four wagons per powered axle on the flat division, overall this balances the characteristics that the models have, given differences in car sizes, lengths and weights and overall locomotive performances we find a very realistic pattern in this.
This is also in working within siding and yard length criteria, but when we do run extra long trains, (and give the dispatcher nightmares), this formula ensures that they will traverse the terrain with the appropriate power.
We do however run some quite long trains for display purposes (and just fun) but (for instance), a coal train we run of around 70 cars with three six axle units traverses the whole layout with ease - but - the train is carefully set-up with free rolling cars, heaviest cars at the front, and tapering to lighter car weights towards the rear, this on a 2 1/2% uncompensated Tehachapi inspired loop and 15inch radius curves.
You can run what you want, but sometimes trying to run long trains can be very frustrating and impractical.
I think something over 500 ore cars was run in Western Australia as a test train, but as spectacular as it may have been, the regular trains are about 200 cars, but they are not on 3% grades or 15inch radius curves (or their equivalents).
Teditor
The real answer depends on many other factors that need to be determined, such as length of the passing sidings, the number of passing sidings, the length of staging area and the number of staging tracks that make up that area, to name a few.
Joe Fugate gives a great explanation on Layout Design Statistics that will help you to answer the question more accurately. I used his calculations to determine my average consist length for my HO layout and arrived at 28 cars, and I can tell you that my layout has 2.5 miles of HO scale mainline runs total.
My mainline curves are 36" minimum (HO) and with a 1.75% ruling grade, I try to keep my train length to 25 cars max. Above 15 and I need helpers to get up the hill. That is very short by prototype standards but looks very long on a model railroad. The eye can’t really take in the full length of the train so I don’t see any point in trying to run anything longer.