The electric locomotives you mention are also equipped with span bolsters--or if not, then articulated frames which are functionally the same thing. And the reason why is and is not exactly the same as the reason it's done on models. Much rolling stock with span bolsters have bodies that do not extend all the way over the trucks, because if they did they'd swing too wide to the outside on curves, and there would be clearance problems. This type of design makes body mount couplers impossible, because the end of the body is not the end of the car. The trucks poke out from underneath. Yes, that excess swing to the outside would cause alignment problems if the car was long enough for body-mounted couplers. So, in that sense you are right. Span bolsters are not necessarily the same thing as truck-mounted coupler pockets. A span bolster-mounted coupler is more like a body-mounted coupler. The pulling or pushing forces do not try to twist the truck on the rails. Oh, they may push one truck up against the right rail and the other truck up against the left rail. But a car with body-mounted couplers can do that too. In essence, with a four-truck, span bolster-equipped car, each span bolster acts as a separate car with one body-mounted coupler. The actual car is carried on these two frames. But a span bolster-mounted coupler is still not a truck-mounted coupler. There are some models of four-truck cars that do use truck-mounted couplers at each end, and they tend to have the same trouble when pushed through curves as any other truck-mounted coupler. Now, I'm not saying a four-truck car with bolster-mounted couplers does not have the same problems, to some degree. They do. The force is transmitted through the span bolster, then through the car, then through the other span bolster. That's a lot of hinges to have in something that you're using to push on something else. It is. But that force is still not trying to twist any individual trucks sideways. Which is why I don't like truck-mounted couplers. With an eight axle heavy flat, you have to put up with the force being transmitted through pivot points. With a normal four axle car, you don't have to put up with that. I actually converted my one span bolster-equipped heavy duty flat from end truck-mounted couplers to body mounts, by the way. Yes, that does result in a lot of coupler swing. But it still gives me a lot less trouble when I shove it into the yard. This is an insightful conversation. It isn't exactly on topic, though, is it? Well, it's a good thread and deserves to be bumped...
I'm with you. I think those who use 9 3/4 radius curves are doing something like trying to haul a bulldozer in a pickup. But if you can do it and you are not disturbed by the appearance, then knock yourself out. But to say that truck mounts are inherantly more reliable is indefensable. And yes, there are some special reasons they are used on a very few prototypes doesn't mean that, just that the prototype has gotten themselves backed into a corner and that got them out. Name a single boxcar, flatcar, hopper car, etc. operating on today's railroads with truck mounted couplers. I know I'm a prototype modeler, rivet counter, whatever, but I would think we all would like to reproduce the real thing's rolling stock to the best of our abilities.
"Minimum curve radii for railroads are governed by the speed operated and by the mechanical ability of the rolling stock to adjust to the curvature. In North America, equipment for unlimited interchange between railroad companies are built to accommodate 350-foot (106.7 m) radius, but normally 410-foot (125.0 m) radius is used as a minimum, as some freight cars are handled by special agreement between railroads that cannot take the sharper curvature. For handling of long freight trains, a minimum 717-foot (218.5 m) radius is preferred" If someone is going to be 'prototypical' those kind of radii are going to be impossible to obtain...unless you have a 'basement empire'. Due to compression and compansations in model railroad track work...we need to compensate body mounted couplers and truck mounted couplers to work on the largest radius we can work into our layouts. As non-prototypical as it sounds and looks...sometimes truck mounted couplers are the only option we have. JMO...thnxs
Well, 410 feet in N scale is only a bit more than 15 inch radius. Not really large and attainable by most model railroaders. 717 is a little more than 26 inches. Probably possible in your RV.
Everyone tries to run the longest trains they can. I would think that 717m would be the rule not the exception. Again...JMO BTW...passenger trains look 'wonky' on 15 in radius track...which I do run...
15 inch radius is 30 in diameter on a turnaround with 32 deep layout top. It takes your breath away when its even a short drop to the floor...like 36 inches 26 inch radius is 52 in diameter. I can't even get close to that in THE RV
Actually, the 410ft in the original post is radius, not diameter. That's 30.75" radius in N. While researching steel mills, I found a 1920's article on trackwork for an open hearth furnace. It stated that open hearths used the tightest track possible including #6 turnouts and 320' radius curves. That's 24" in N.
Even I forgot the 410 I quoted was radius not diameter. Can you imagine a 717-foot radius in N scale !!!
I would like to keep the truck-mounted couplers, but wouldn't I have to make a cut out at the bottom of each end in order to give the coupler space to move as the truck goes around a curve?
Yes, but if you're lowering the car that much, you'll have to cut the end to body mount too. The big difference is you'll have to cut a wider slot for truck mounted where body mount only needs an opening the width of the coupler box.
The shots I'm showing you from the beginning of the thread preserved the truck mounts. I removed probably .015 on the end above the box. Stock car has a lot of space there it really doesn't need between the box and car end. Mostly, my point is that after you're done, you'll notice neither the truck mount nor the flanges, but you will note that the car looks 'right' in terms of height. There's been a feeling that to lower the car you also had to go to body mounts, and that's just not true. I'm simply advocating that it's easier than you think to deal with the height issues, and has a really nice payback in terms of time vs. benefit. If you're backing a long train through switches and piling up because the trucks are forcing to the side and jumping the points or frogs - and you've already cleaned up both of them, then you really have a pretty darn good reason for going to body mounts. Other than that, I'm convinced the entire argument is pretty much irrelevant, and if you're also trying to do magnetic uncoupling anywhere near curves or a diverging switch, won't work at all. If I had the kind of space to be working above 18" radius, I probably would have stayed in HO instead of converting to N, although it wouldn't be modern equipment. I'm regularly backing 25 cars through my Atlas switches on diverging route, I'm not derailing, so I generally tend to be rather suspect of the claims more to those that have never really cleaned up switchpoints and frogs properly, or just have longer, heavier physics here. I know there's just no benefit at all for body mounts to me, but if I buy a car that way, I'm not changing it unless I run afoul of uncoupling issues or the ONE case of stringlining I mentioned due to lack of shank length & swing. Everything we design in here for current work is now with a 14-degree standard minimum radius (410 ft. or 31" radius in N) and a #10 turnout to keep NS and CSX happy. Since they went to a lot of six-axle power they really don't even like #8's. So anything less than that is actually a compromise, it's only on how far you're compromising from the actual. I can show any number of absurdly tight design situations from the past, they are everywhere. I'm working with a steel mill right now that's having a heck of a time because they just can't handle standard 65' mill gons - the entire site was designed for 55' max, and the long ones derail on several tracks on the site due to tight curvature. In case you haven't noticed, the 52/55' cars are dying out due to age. So while wider is always better, even if your scale is 12"=1 foot, you only have so much space to work with. In this case this is such a serious problem it may result in the mill being closed as it is so rail-dependent, so trying to redesign it has become quite the project. Most of you know I'm also heavily into N logging, and if you look at the locomotive builders catalogs on minimum radius, grade, etc., you'll choke on something. Climax, in particular, prided itself on being able to run on anything a horse team could negotiate. One of my favorite shots: http://www.climaxlocomotives.com/catalog/?pg=11 And while there's no photograph, there's at least mention of 15% grades and 40-degree curves here: http://www.climaxlocomotives.com/catalog/?pg=14 That pretty much works out to 10" radius. "Body mounts" with link & pin typical, WIDE shank slop, and normal equipment lengths were 25-30 feet maximum.
