Wheelset standards

[Anonymous]

Has anyone developed a list of prototypical wheel sizes used on freight cars and if so, would they be willing to share this information? I've been unable to locate a source that will tell me what size wheel is used on a specific type car. I'm wanting to convert my rolling stock to metal wheels and I've discovered many discrepancies between manufacturers regarding the size of wheels they supply. An example - Manufacturer "A" supplied 28" wheels for a 100 ton Center Flow hopper, Manufacturer "W" supplied 33" wheels, I'm pretty sure the prototype has 36" wheels. Any help you more advanced modelers can provide would be greatly appreciated. Thanks in advance!

[Anonymous]

This is not an easy answer but I will give it a shot.
First, on this home page, Trains.com across the top,
select model trains and click. Scroll down to 'Use the right wheelsets' and this will take you to the April 2002 MR April 2002 wheetset article.
Second, there are 28",33",36",38"
Third, some wheels are ribbed back, some are smooth.
Fourth, there are many model wheelset manufacturers and there are the exceptions to the
general rules of thumb.
Passenger cars normally require 36", but my Rivarossi heavy weights take 33"
Freight cars, some model manufacturers have made mistakes but I would match the stock size with the
replacement.
Pre WWII used 33" ribbed back wheels.
After WWII, cars built generally use smooth back.
70 ton, 100 ton and 125 ton are common weights for
trucks.
70 ton, generally 33"
100 ton, probably 36"
125 ton, probably 38"

Exception, 40' cement hopper 36", but a 40' granules hopper will use 33"
Common uses of 70 ton frames and 33" wheels are boxcars, flatcars, open 40'hoppers, gondolas & cabooses.
50' open hoppers will probably use 36" wheels.
Most tank cars and covered hoppers are the proble
cars.
Auto racks may use 28" for clearence reasons.
Tank cars are sized for the density of the cargo.
Anhydrous ammonia cars will be, generally 125 ton truck with 38" wheels.
If you change into a different size other than the stock size, you also change the coupler height.

There are Blunt axle,Flush axle and Pointed axle
sets and the acceptance of the truck frame will vary.
Athearn cars may vary from roundhouse etc.
As a generally rule I have found that modelers prefer Proto 2000 metal sets that come in smooth &
ribbed backs and are moderately priced.
Metal sets will increase your free rolling ability.
Intermountain sets are 100% metal and also come with ball bearings and are the most expensive.

Changing couplers styles are a lot easier to figure out than wheel sets.
Happy railroading.

[Anonymous]

Charles,
I appreciate all of the information you've provided me concerning the wheel diameters to use. If I'm reading your answer correctly, if I put prototypical sizes on my cars, such as 36" on covered hoppers and 33" on box cars and others that require them, my couplers will now be out of spec with regards to distance from the railhead? Does this mean that the bolster heights on the cars is incorrect from the start? Makes me wonder why the NMRA has standards when the manufacturers don't want to follow them....... I guess it's back to the drawing board now. Thanks again,
Don - Austin, TX

[Anonymous]

I have not personally experienced incorrect original
stock sets but others have with some athearn & roundhouse models. Perhaps just a fluke and there are a few exceptions to the general rules of thumb.