I'll try and measure it tomorrow after work. It looks to be about the thickness of one of the diaphrams.
Thanks Tony. I did a bit more research on the RPO that I have, and it looks like the factory body mount coupler on that car is a MT 1025. I'm guessing that is also the case with the Pullmans, but I don't have one to check. Can somebody confirm this? The MT 1025 is the configuration with the reverse-springy effect (opposite the common 1015, the spring compresses when being pulled instead of pushed). The bad news is that conversion to the short shank body mount 1027 would only reduce the gap by .118" (much less than one half of the as delivered .286"). So much for an easy drop in fix..... Also, since the RPO doesn't have a vestibule/steps, there is much less space to relocate the coupler away from the end of the car. I also found that unlike the pullman car shown in Tony's original post, the RPO already has the bolster pin located toward the end of the car (not the middle). Nate: with the installation of the Z scale couplers, was there room to drill a new hole and mount them closer to the truck?
Jack, At full compression (no tension on the couplers), I measure right at 1 scale foot between diaphrams. At full tension on the couplers, I get just under 2 scale feet between the diaphrams. Yes, there is room to drill new mounting holes and mount the couplers further back from the ends of the car (you may even get away with not having to flip the trucks - the Z scale coupler box is pretty small). The next time I send in an order, I'm going to get a couple sets of the American Limited diaphrams. I think that with their added thickness, the method I've used here will be perfect and they should touch while still giving you enough play to go around curves without derailing. Interesting discussion guys; lots of good options here. Nate
The sleepers and parlor come with 1015's on them. Different than the 1025 on the RPO. A Z scale coupler has a longer box than a 1015 so you really don't gain anything there.
I have a CBQ RPO would this be needed, did they have the same length coupler to match passenger cars or would it matter since the ends don't have through acess.
Unfortunately, both my RPO's are town down right now for kitbash and paint projects. I don't think the spacing was as bad as the sleepers though. They have a much larger mouting pad if you want to redrill and move the couplers back though.
The won't. Unimates are designed to fit in place of a Rapido coupler. They won't fit the MT coupler box and the screw mount versions are probably not flexible enough.
The only change that could help tight radius is more distance. The curent production spacing seems to be a compromise between performane on tight curves and acceptable gap between cars. You will always have folks who can't have all wide curves so the manufacturers try to accommodate them.
The method showed at the begining of this topic both improves tight radius performance and gets the coupling spacing closer together. By putting longer shank couplers with more swing the cars can handle more offset between ends. Moving the bolster pin location minimizes the overhang on the ends of the cars which also helps. All this with getting much closer coupling of the cars by moving the coupler mounting point farther toward the center of the car.
For the heck of it I dug out a Pullman and one of my RPOs to check with American Limited Diaphragms. The new diaphragm is just tacked onto the RPO while the Pullman on the left has the MT diaphragm. It does close up the gap some but I have seen a few issues. At the base of the bottom sill on the RPO the American Limited does not fit in the gap without some trimming on each side. This does not appear to be an issue with the pullman because of no protruding bottom sill. Mounting the diaphragms could be an issue because of the design and the springs clearing the inside ledge around the door which would have to be removed. The A L diaphragms for lightweight cars don't have that issue but still don't fit because of the differences in roof design between light and heavyweight cars. What may be needed is a spacer which they have with the F unit conversions. That takes care of any diaphragm spring clearance issues on them so I may dig out a set tommorow and try them with the spacer. Also the RPO and Pullman have different couplers with the RPO being a low profile coupler while the Pullman appears to be a 1015. The truck swing of the RPO is limited by the end steps and the steps below the car doors and it does not appear that anything can be gained by moving the trucks. But it is a much shorter car and should negotiate a 9 and 3/4. The pullman and probably my GN obs have a much wider truck swing on the longer cars. In short probably finding a good way to mount American Limited Diaphragms and adjusting the coupler spacing will improve the appearances some. There is plenty of space to mount just about any coupler that offers a wider coupler swing on the longer Pullman cars and adjust them in maybe a smidget.
I think they are the ultimate solution for this. There was another thread, either here or on another forum, where somebody used the screw mount ones with great success. I think this is just like with the rear of Intermountain F units. Due to space limitations, the best solution is the Unimate dummy. Maybe someone can post the link to the thread I'm referring to.
I have seen and tried all the different solutions suggested since these cars came out. None work as well and couple the cars as close as what I came up with. My cars will couple close enough that the diaphrams will touch each other when backing but still go aound 11" curves with no problems. As is the cars struggle on anything less than 13" curves unless you have easements. My method is a little more work but the improvement is well worth it. If you are running on a layout with large radius curves, then most of this is not needed and the unimates are probably the easiest answer but most people don't have 18" R curves on their N scale layout. Review - Coupling distance, straight line - Coupled on a 11" R Curve - I need to take a picture of them on a crossover to show where the real problems start with the stock setup and anything the brings them closer without changing the coupler mounting position.
I just obtained a Kato Amfleet car. And when testing it, I noticed that it always derailed when going around curves when coupled to a MT heavyweight. When coupled to another car, it had no problems. So there is something about the MT design that may cause problems. (of course the Kato car has very low profile wheels which may contribute to the problems).
Tony do you think just doing the bolster trick will work with using z-scale couplers? I'm only have on Heavy Weight observation, It will always be on the tail end.
It really depends on the radius you will be running on. Flipping the bolster helps a lot. I haven't tried that combo but the Z couplers don't couple as close as moving the mount and using 1016's so I think it work better than stock regardless.
Revisiting this thread again having finally had the time to pull out these cars and do some seroius looking and tinkering. Absolutely forget about these cars if you have any 9 and 3/4 curvature. You may get away with the RPO on that but I serously doubt it. After messing with some 11 inch curved on the workbench last night and today even 11 inch is iffy if you are running a long train. I used Skipgear's modification on the truck mounting with a lot of improvement in running on 11 inch. I didn't see it in the original post but there are two truck retainer posts, behind the bolster, that keep them from swiveling too far and they need to be shaved off in this procedure. That said the biggest obstacle to a tighter radius is the coupler. Again I followed Skipgear's lead and replaced the couplers with wider angle MT #1016s. I also moved the coupler back but in this I dared to be a little different. I actually drilled my new coupler mounting hole right in the gap between the undercarriage and the coupler pad. There is a solid plastic bottom under this plastic undercarriage insert. The original plastic coupler mounting pin cannot be used and instead I used the provided screw in the 1015/16 package which has the length and strength to reach that plastic car bottom where the plastic pin does not. That moved the coupler back and shortened the distance some. On another one I drilled a new hole at the back of the mounting pad. The former pulls the coupler in further while the later is okay I think the drilling between the pad and the insert is the optimum. The brake hangers on the truck just clear the coupler box. Even with this modification if you are in 11 inch curvature and come out and change direction the opposite way I can pretty much assure that there will be a derailment unless there is enough straightaway for at least a full car length or more before heading into opposite curvature. I short these cars are nice cars but even with modifications look like crap on 11 inch. And even with the 1016 couplers there is still a strain on the lineup. Hopefully in the next few days I will get the time to play with some different radius but I suspect that 12 inch or above is what will be best. The coupler on the right is mounted in a new hole between the pad and the insert. The left in a new hole at the absolute rear of the coupler pad but still in the pad. This is as far as I could go back and not have the brake hangers on the truck hit the coupler box. In my modifications the trucks now will swing completely to the side of the car since I also trimmed a bit off the center sill. Still looks like crap on 11 inch though. Fortunately my designed mains have 16 and 17 inch radius curvature.
