Here is my crack streamliner making the 22 inch Creamery Curve. It can be done, but it’s pushing it. The cars are IHC corrugated side streamliners painted for the B&M. The consist is sorta fantasy. The B&M did own some corrugated side coaches and sleepers, I don’t believe they ever owned a boat tailed observation or a diner. I do have a photograph to support the red thru-the-windows stripe.
The secret to managing 22 inch curves is truck mounted couplers. They need lots of swing, from side to side. It took a bit of Dremel work to clear away the bottom of the end sills. I also had to weight them right up to NMRA RP 20.1.
Here is the same train exiting Bunk Bed tunnel. The motive power is P2K.
There is an additional trick that Rivarossi/AHM used for their 85’ cars to go around 18" curves. In addition to the truck mounted couplers, they did not mount the truck in its center. They offset the truck mounting hole more toward the inside axle. This allowed the pivot of the truck to be closer to the center of the car essentially making it “shorter” as far as the tracking was concerned.
The problem with truck mounted couplers is that there is more lateral stress is put on them in the curves. Instead of just tracking the car they are tracking the entire weight of the train behind them. In forward motion the more stress that is put on them the more they want to bind (the same concept as a whole train wanting to string-line) in the curves. In reverse they want to do the equivalent of a train doing the accordion.
There is also more vertical stress put on the kingpins. Once again they have to deal with the entire force of the train behind them instead of just the force of the one car.
Most of all this is irrelevant for passenger cars because the trains don’t get long enough or heavy enough to have these factors become very large. Rivarossi / AHM also hedged their bets and decreased the chances of this being a problem with their .039 (pizza cutter) flanges that they put on the wheels.
Where is that member who wanted a science fair project? - The maximum and ideal length/mass of a model train using truck mounted couplers vs body mounted couplers.
As has been pointed out above, just about any radius curve – heck, even a tangent – will pose a challenge to truck mounted couplers when a train is being backed up. A few things might slightly help out in reducing derailments.
First is adding weight above NMRA standards and concentrate it above the trucks (and center it perfectly). One old trick is to wrap thin solder around the axles to make for a very low center of gravity. Since you are unlikely to mix these cars with other trains, this modest deviation from the NMRA weighting standards should be harmless. Of course excess weight might lead to problems when going forward so don’t overdo it.
Second is to consider the coupler used and how much side swing is allowed. This can be tricky because it is that side swing that allows them to go through the 22" radius to begin with.
Third, and this is perhaps now impractical for you, is to consider an easement curve into the 22" radius because probably where the curve meets the tangent is the area of greatest stress.
Fourth is to make sure your trucks are exceptionally free rolling, and perhaps a go with the “truck tuner” is in order. I only have one IHC passenger car and was not impressed with its rolling characteristics out of the box (where it remains by the way).
Fifth is that your track laying on that curve needs to be perfect and don’t be afraid to tinker with shims and the like if it improves trackability.
Sixth – what I call the “Wisconsin Norwegian” approach – is to not back up your train. Uff da!
Your lead photo shows something that more people should be aware of. Seen from the inside of the curve, long cars don’t appear problematical. Seen from the outside (the free-end curve of a peninsula comes to mind) they look ghastly.
My own long cars (20 scale meters, 250mm over end sills) are shorter, but I had to open up the end curve on one peninsula to improve their appearance. They also have clearance issues, which is why my concentric curves have 60mm between track center lines.
All in all, a good compromise. As for the problem in reverse, maybe a powered observation car? (All of my passenger couplers are body mounted. A lot of my freight stock has truck-mounted couplers - but the ‘trucks’ are four wheel freight vans, so they don’t have the problems associated with bogey stock.)
I love that. I really do. I have often wondered about powering the rear car. Of course, it you did that, what becomes of the loco that was leading the way in forward?
The slightest hiccup on either power unit will pretty much instantly stringline or accordian the train, depending on which end stalls. Even if they were free-wheeling spur gear locos so the trailing one would just be pulled - that’s more drag that a bunch more of the cars and I don’t think it would work out too well.
One thing that helps greatly - not using X2f couplers. The design of those puts a constant side force on the coupler shank and thus the trucks, skewing them and causing binding and also helps them pick every point. part of the reason N scale was more reliable back in the day (besides the BIG pizza cutter flanges) was that the Rapido couplers, oversize and clunky looking though they may be, don;t exert any side forces on the trucks. That big square box even helps keep the trucks from skewing when pushing back.
When the X2F was widely used we had no real issues even when backing long string of cars-I have first hand experience with that since I use to work the Portsmouth(Oh) passenger terminal and freight yard on the old Columbus HO Model RR club back in the 60s.
The key was body mounting the X2F on freight and passenger cars at the correct height with no droop.
The X2F was a smooth working coupler in its day…
As far as stringling over a locomotive hiccup I don’t see that happening in HO.
I’ve gotten Walthers passenger cars around 18" turns. Very ghastly looking, and can only run one at a time account the car bodies would hit each other on the S-curve. (Click on the picture to watch the video.)
I reworked a string of RTR Athearn streamlined 80’ cars by body mounting Kadee couplers and installing IM metal wheel sets. Also added additional weight inside the cars. I even put American Beauty diaphrams on them. They work great on my layout which has a mimimum 28" radius curves. They back up pretty well too. The truck mounted couplers that came with them was a constant problem on one of my 32" curves that was also on a grade; closelined almost every time.
That looks good, but I also perefer the Body Mounted couplers.
I have purchased some KaDee #451 Extended Swing Couplers for some Older Amtrak Kits I have that have been brought to market by IMR.
I have not been able to find the time to finish these, but I am hopeful they will be able to take some tighter test corners.
I do not have a layout yet, but a couple of Switching 2’ x 6’ plates, & I do some testing for Looks & Function on a temporary plywood plate with nailed in track.
This will let me plan & HOPEFULLY, design a nicer layout when the time comes.
Has anyone else tried the newish 451’s from KaDee?
Yes, body mounting fixes many ills - but so much stuff then came with truck mounted couplers and they WERE a problem.
The discussion was putting a powered unit at the front and back of the train, ostensibly so you could back it up as well as run it forward, since you’d always been pulling and never pushing - of course that requires some sort of method of having the ‘rear’ loco coast like a car. But if you put a powered unit on each end of the train and one of them stops dead while the other keeps going - on curves already kinda too sharp for the equipment - it’s coming off. On a train heavy enough to NEED the extra power, probably not. We’ve run 150 car coal trains on the club layout and had them die around a curve, on a grade, through a crossover - and suddenly restart, and not stringline, but they are HEAVY cars, exceeding NMRA RP weight. ANd with just one steam loco on the front, or else about 3 diesels.
I’m sure consisting 2 locomotives with matching CVs that could be possible after all I did that once in DC with no issues.Lucky? Maybe,but,I kinda doubt it.
Although this is not something I am considering at this moment, I ‘could’ apply the current Tech to do this, many of my my RC counterparts have one way ‘clutch’ bearings, in their now very small hand held RC Helicopters.
So I feel, I could design a ‘one way powered truck’ to do such a helper function.
Again, although a sidetrack, it is not out of the question.
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