trailrider
Well-Known Member
Correction, the 2-10-4's are M4's, not M3's.The Mantuas are sure heavy haulers. If I can find a pull gage, I'm going to try to measure the drawbar pull on this hog. There is supposed to be a formula or something that will indicate the number of "free-rolling" boxcars (whatever that means) on a level track. It would be kinda neat to know what train it would haul on a modular club layout, if those modellers get back to having shows after the pandemic subsides. Sure can't do it on a layout in a 14' x 14' room layout.
Been doing some experiments and calculations. Using a spring-loaded scale, I measured the drawbar pull of the M4 at 3 oz, with the drivers almost ready to slip. According to a review of Athearn's SD60M in RMC, the drawbar pull of that was 4.8 oz. They state that that is the equivalent of pulling 67 "freerolling freightcars" (whatever those might be). 3/4.8 = .625 x 67 cars = 41.875 or 41 cars on a straight and level track. Considering that only the end drivers on my kitbashed models actually contact the rails, that isn't bad. IIRC, the starting tractive effort of steam locomotives is not as great as diesels, which is why steamers bunch the slack in a train before starting. Diesels OTH don't do that as they would probably break the drawbars somewhere in the train. But I might be wrong about that.