Ride Height

[milw156]

I made a set of clearance cards out of styene that correspond to the scale max height over the rails for each plate, so I have ones for Plate B, Plate E (sincd the height of things like roof ribs may not be perfectly to scale) and Plate F.

*****I put a car on a flat surface the the top of the workbench when using my clarance plates so I don't have to account for the height of the track (Kato unitrak vs Atlas sectional fof example) when checking cars*****(asterixs added).

This works for getting the roof of the cars at the right ridd height, but you may still need to adjust coupler height and for some cars that are vertically compressed (like MTL FMC 50' boxcars and 60' waffle side cars) the side sills may be still too high when veiwed against other cars.

I thought prototype car height was figured from the TOP OF RAIL to height of car (at max width and max height). This in itself would take the rail code variable out of the equation, or am I missing/forgetting something?

[peteski]

Yes - for boxcars, covered hoppers, tank cars, this is already the case.

Not so much for 89' flats/autoracks and passenger cars; hence their need for underslung couplers. The solution would be to redesign the space for the coupler box "sunken in" more to allow this. Fortunately ScaleTrains already had the sense to do a semblance of this for their recent N scale Multi-Max autoracks.

Unfortunately I suspect (without doing any research) that N scale couplers (probably starting with rapidos, and then Kadee Micro-Trains knuckles) were designed to be located higher than 1:1 prototype  couplers.  Plus as I mentioned, the N scale couplers are oversize, adding to the problem. That's probably what messed things for all of us, and that height continues to be used for backwards compatibility reasons.

[Lemosteam]

I thought prototype car height was figured from the TOP OF RAIL to height of car (at max width and max height). This in itself would take the rail code variable out of the equation, or am I missing/forgetting something?

I had the same question after the post.  I am lucky as a PRR modeler that there are so many drawings and diagrams available to get as close to prototype dimensions as I design.  First thing I create is a sketch of the top of rail with wheel diameter tangent to that.  This way I can always measure back to top of rail as I proceed.

The common things to look out for is maximum truck swing (also critical for knowing the min radius of a car), wheelset axle clearance to coupler box and its screw head (flat head 00-90 screws come in handy for lowering) as it swings under the coupler box.

Since I also design my trucks, I can set the truck frame bolster surface where I want provided the MT bolster pin head isn't too low.

Seriously though in this age of printing and self-design, I wish MT would share non-proprietary, basic step file models of their critical parts: boxes, lids, coupler halves, etc., or even just an envelope package of each coupler, especially the Z.  It would allow for perfect design of mating cars with respect to the coupler height from the top of rail and proper fitment of the couplers to the car, as designed.

[Mark5]

I thought prototype car height was figured from the TOP OF RAIL to height of car (at max width and max height). This in itself would take the rail code variable out of the equation, or am I missing/forgetting something?

Absolutely correct! 

[squirrelhunter]

squirrelhunter,
Did I miss something? When you set the car on the table top how to you compensate for different the flange heights?
Also the plates consider an empty car on new wheels. Not that it really makes a difference at 1/160.
Would having cars look prototypical by side sill height look better than roof height which varies with loading?

I don't compensate  for flange height, but I also generally use newer BLMA/Atlas/MTL trucks and wheel sets, and the flanges among those don't appear to have that much variation in height.

[peteski]

I had the same question after the post.  I am lucky as a PRR modeler that there are so many drawings and diagrams available to get as close to prototype dimensions as I design.  First thing I create is a sketch of the top of rail with wheel diameter tangent to that.  This way I can always measure back to top of rail as I proceed.

I wonder then if you could address my speculation that the N Scale couplers are located too low compared to 1:1 scale couplers?  I guess I'm asking whether the centerline of N scale couplers is located at a height (from the rail top) 160 times  smaller than a centerline of a 1:1 coupler?

[randgust]

The entire railroad world functions from 'top of rail'.   You'll find clearance diagrams for a lot of vintage equipment online, and while they aren't very detailed, the critical height and width dimensions always are.

PRR in particular has almost every piece of equipment online, that's an excellent reference.    I know for my ATSF stuff, the "Iron Horses of the Santa Fe Trail" has every locomotive clearance diagram in it.    Railway Cyclopedias usually have equipment diagrams as well.  It's a real challenge to try to fight down those height dimensions, I ended up lowering the boiler on my Jamco 4-6-2 over a scale foot by taking it off the cylinder saddle.   Similar issues with building my PRR D16 4-4-0.

I've lowered a lot of MT cars, and still kept the truck mounted couplers, mostly by savaging the ends and getting the floor further up in the bodies.   It's really, really noticeable on flatcars and gons, some boxcars much worse than others.   I've replaced the bolsters on all gons and flats after cutting out the metal bolsters and end floors.  That's pretty radical, but it works quite well, and the coupler height is consistent.   

[squirrelhunter]

Absolutely correct! 

I guess I should have been more clear about what I'm controlling for by using a flat surface- I'm worried more about the total height of the stuff below the rail top, like the ties or the base in the case of stuff like Unitrak, as well as the code of the actual rail.  I wanted to make a template that I didn't have to use with a specific piece of track.

I also agree my method incorrectly "counts" the flange height in the clearance diagram. For me personally I don't mind since all my equipment I swap trucks/wheelsets to lower profile flanges if they have older pizza cutters on them, and I don't have any cars that ride on 36" wheels on my layout. If you have a mix of flange types or wheel sizes you'd need to account for that.

The 6" difference between a plate B and a Plate C car in max height is .0375", and that they 3" max height difference between a Plate C and a Plate E car is .01875. I suspect that some of the roof details on our boxcar roofs like the ridges between seams are overscale so if you wanted to be exact that would have look at that as well.

I wanted a quick way to check if a car that was ostensibly a Plate B boxcar didn't have the roof height up at Plate E, especiallyif I had already swapped the trucks or wheels. I think I could put together a more accurate clearance plate setup permanently attached to a test track.

[peteski]

I guess I should have been more clear about what I'm controlling for by using a flat surface- I'm worried more about the total height of the stuff below the rail top, like the ties or the base in the case of stuff like Unitrak, as well as the code of the actual rail.  I wanted to make a template that I didn't have to use with a specific piece of track.

Your explanation makes me even more confusing.  Maybe I'm misunderstanding your statement. First of all, I think for most modelers correcting (usually lowering) the ride height do it for appearance reasons (not overall clearance).

Second, if you are worried about "total height below rail top" then wouldn't you be using wheel treads on the rail top and the rail top as a reference.  The only things that can see causing below the rail clearance issues are coupler trip pins or any other things hanging under the car.  Nothing except flanges should extend below the rail top, and the rail top would to me still be the "gold" 'reference point.

[wcfn100]

I wonder then if you could address my speculation that the N Scale couplers are located too low compared to 1:1 scale couplers?  I guess I'm asking whether the centerline of N scale couplers is located at a height (from the rail top) 160 times  smaller than a centerline of a 1:1 coupler?

The Micro-Trains diagram that shows a centerline of .216" is the same as the prototype of 34.5".  I don't know if the truck mounted couplers actually sit at that height.


Jason

[squirrelhunter]

Your explanation makes me even more confusing.  Maybe I'm misunderstanding your statement.

Sorry, I'm not trying to talk past everyone on this. I'm adjusting ride height base on where the roofline of the car sits. Here are the clarance cards I made:


To use them I hold them vertical and roll the particular car through the opening.

For example, a stock FVM PS 5344 boxcar, which is a plate C prototype, won't go through the Plate E card. If I swap the underframe for one from an Atlas FMC 5077 boxcar and replace the trucks with BLMA ones, it will fit through the Plate E card.

My goal is to have the roofline of all my Plate C cars be at the same height, and the same for all my Plate B cars, etc.

[Lemosteam]

The Micro-Trains diagram that shows a centerline of .216" is the same as the prototype of 34.5".  I don't know if the truck mounted couplers actually sit at that height.


Jason

I know the MT gauge is set to that height, and that the mounting height surface on it is also at the correct height for a 1015/6.

So if a truck lines up to the gauge, then it should be at the 0.216" (5.5mm) height.

[NtheBasement]

I am by no means an expert but I was under the impression that the plate dimensions were maximums, so one plate C car's roof could be six inches lower than another's.

[peteski]

Sorry, I'm not trying to talk past everyone on this. I'm adjusting ride height base on where the roofline of the car sits. Here are the clarance cards I made:
. . .
My goal is to have the roofline of all my Plate C cars be at the same height, and the same for all my Plate B cars, etc.

Ok, so basically you are not worried about how the cars look like viewed from the side (whether they are sitting too high or low in the trucks), but just how tall they are.

I also don't understand why your reference reference would be the surface or the bench-work (since that is what flanges are resting on?  Why does that matter? 

Even if you want the cars to be the same height, why not measure them from the rail top?  I guess I'm just too dense to comprehend this.

[peteski]

The Micro-Trains diagram that shows a centerline of .216" is the same as the prototype of 34.5".  I don't know if the truck mounted couplers actually sit at that height.


Jason

Thanks!  Well, that answers that question.  So I guess the unprototypically thick materials used for the N scale coupler (draft gear) boxes,and the thickness of the decks is the reason why flat car's couplers need to be underslung.