Model Coupler Height and Car Height

Model Railroader General Discussion (Model Railroader)
1

I’ve been seeing several posts about coupler height problems and car height(bottom of car to top of rail)problems on new models.Sounds to me like plain old not-doing-their-research issues at the manufacturers.This shouldn’t be with all that’s available in print and on the internet.These problems arise from one of three factors.1)Centersill dimensions.2)Car bolster.3)Truck bolster.

Problem 1.Centersill.This is the main support beam running down the center of the length of the car.If you look at it from one end it looks like a square ‘n’.The inside dimensions of this ‘n’ are 13.5" wide by 12" high.This equates to .155"X.138" for HO and .284"X.250" for O.Any severe tolerances(greater than .010")is going to cause a coupler height problem.

Problem 2.Car Bolster.Where the bolster crosses the centersill is a plate bridging the bottom of the centersill.It is roughly the width of the bolster and about 2’ to 2’6" long.Centered on that plate is a centering plate that sits in a ring on the truck bolster.It is 14" in diameter(.161" in HO and .294" in O).Both the bridge plate and centering plate are about 3/4" to 1" thick(HO .009"-.012" and O .016"-.021").

Problem 3.Truck Bolster.The truck bolster has a ring with an inside diameter of slightly more than 14"(.161" HO and .294" O).It has the same thickness as the centering plate on the car bolster.I haven’t checked too much on truck bolster dimensions and overall truck height as that changes with wheel diameter.Maybe someone can help out here.

Another issue is couplers.So many types,copies,clones,rip-offs,etc.Why not just a model of the real thing?In HO in the 50’s and 60’s there were some model couplers produced before the NMRA X2F(horn-hook) fiasco.MDC and Varney had operating scale knuckle couplers that I’ve seen.Now Sargent has introduced some in a couple of scales.There are also many non-operating

2

I agree completely about the coupler height. They should at least be able to get that right. I’ve got 2 Athearn BB locos that are about 1/16" off from each other and 3 Bachmans that aren’t even close to each other. It’s pretty bad when coupler manufacturers have to come out with a whole line of offset heads to compensate for a lack of a standard.

3

There are standards and most companies try to adhere to them. Unfortunately it is not possible to just scale prototype dimensions for many reasons, the most important being the tight curves we use, FAR FAR tighter than prototype. If the wheels were made exact scale the things would never stay on the track. Couplers need far more clearance for the curves. Model components are used on many models so may not come out to the exact right height all the time.

4

In the 39 years that I been using KD couplers I never found the need to use a over or under shank coupler on any brand of locomotive including Athearn BB.Like all things I inspect my models and have found the coupler mounting pad slightly bent on a Athearn locomotive…This I straighten by GENTLY bending the coupler pad…Then I file or grind the pad and add a #5 coupler in its box fasten by a 2-56 x1/8 screw…

Like so:

The end results is a coupler that is solidly mounted and properly guage…

As far as the BB cars care must be taken in assembling these cars to include the weight and frame being straight-straighten if needed.

By doing so here will be your results.