Model Railroading > Question about 28"-33" and 36" wheels...

   I have a question, I don't understand how it is determined what inch wheel goes on cars. Does it go by the length? empty weight or gross weight?
I'm always asking friends what Intermountain wheel goes on a car I'm working on. I'm sorry but I don't have a clue...

   Thanks for your help

   Steve H...



Edited 1 time(s). Last edit at 01/22/20 04:16 by hartrick24.

 Basically, 33" wheels were used on cars in the 50-70 ton range---cars rated for 100 tons received 36" wheels. The 28" wheels were best suited for autoracks to keep them as low as possible for clearance reasons.

In my experince, cabeese and tank cars use 36" wheelsets and the rest of my rolling stock use 33" wheelsets. 

D0wnt1me Wrote:
-------------------------------------------------------
> In my experince, cabeese and tank cars use 36"
> wheelsets and the rest of my rolling stock use 33"
> wheelsets. 

Every caboose I've ever seen was on the standard 33 inch wheels.

As noted in the first response, wheel size for freight cars is based primarily on weight. And I've never heard of a 100-ton caboose.

The larger the diameter of the wheel, the lower the contact pressure on the wheel/rail interface.
If you load up a small diameter wheel to high loads it damages both the wheel and the rail.
Autoracks, being rather light, can get away with 28" wheels.
Road engines use 40-44" wheels to avoid damaging the rail.

As a rule of thum i use 36'' wheels if car weight rated over 200,000 lbs  cheers D.

toledopatch Wrote:
-------------------------------------------------------
> As noted in the first response, wheel size for
> freight cars is based primarily on weight. And
> I've never heard of a 100-ton caboose.

How about the occasional 100-ton conductor? :D

tiltone Wrote:
-------------------------------------------------------
> As a rule of thum i use 36'' wheels if car weight
> rated over 200,000 lbs  cheers D.

Good rule, same here. 

In the olden days freight cars had 33" wheels and passenger cars had 36" wheels though I don't know if passenger cars under 60' long got 36" wheels or not. There are 100 ton freight cars with 33" wheels with larger bearings but those seem rare.

I never saw a caboose with 36" wheels though there may have been some built with passenger trucks that had them.

fbe Wrote:
-------------------------------------------------------
> In the olden days freight cars had 33" wheels and
> passenger cars had 36" wheels though I don't know
> if passenger cars under 60' long got 36" wheels or
> not. 

Passenger car wheels start out at 36.5".  They have a thick tread that can be turned to compensate for wear like locomotive wheels.  The minimum that they can be turned is 33.5".  Lower than that they are condemmed.  So in reality passenger car wheels can be anywhere from 36.5 to 33.5".  I pointed this out on an SP forum one time and it answered a question as to why the striping on Daylight cars didn't line up exactly.  If the mating cars are at the extremes of wheel size then the pinstripe can be off by as much a 1.5" (clearly noticable to the eye).  The reason passenger car wheels are designed this way is for cost savings by being able to reprofile the wheels.   Passenger cars, like locomotives, are designed to be moving all the time.  This puts a lot of wear on the wheels.  Wheels get dished or get sharp flanges from wear.  This is an unsafe condition as a sharp flange can pick the points on a switch causing a derailment.  So wheel inspection and maintenance critical for passenger cars. 

Freight cars on the other hand rarely wear out their wheels.  Most freight cars spend most of the time sitting still, either being loaded, unloaded or sitting in yards.  So they can have the same wheels for their whole lives.  Usually the reason to change them out because they have been flat spotted or have bearing issues.  So freight car wheels are usually round numbers like 33" or 36".  When you look at them the tread profile is thinner because when they do get worn out they are scrapped.  They cannot be reprofiled.  

ghemr Wrote:
-------------------------------------------------------
>  Basically, 33" wheels were used on cars in the
> 50-70 ton range---cars rated for 100 tons received
> 36" wheels. The 28" wheels were best suited for
> autoracks to keep them as low as possible for
> clearance reasons.

38" wheels are used on tank and covered hopper cars using 125-ton trucks. I'm not sure if any 125-ton trucks are currently available? The old Eastern Car Works trucks are the only ones I'm aware of and they really don't stand up to modern truck models.

Also, many articulated well cars use 125T trucks with 38" wheels at their articulation points.  70T trucks with 33" wheels at their ends.

Lighter Wrote:
-------------------------------------------------------
> ghemr Wrote:
> --------------------------------------------------
> -----
> >  Basically, 33" wheels were used on cars in
> the
> > 50-70 ton range---cars rated for 100 tons
> received
> > 36" wheels. The 28" wheels were best suited for
> > autoracks to keep them as low as possible for
> > clearance reasons.
>
> 38" wheels are used on tank and covered hopper
> cars using 125-ton trucks. I'm not sure if any
> 125-ton trucks are currently available? The old
> Eastern Car Works trucks are the only ones I'm
> aware of and they really don't stand up to modern
> truck models.

It all depends on the weight upon each wheelset. Cars that have higher hauling capacity need more contact area on the railhead to avoid excessive wear and deformation on the railhead and wheel tread, but the downside is that it inceases the rolling resistance of the car. So lightweight spine cars had 28" wheels, and most modern freight cars have 36" wheels.

Ted Curphey
Ontario, OR

wingomann Wrote:
> Freight cars on the other hand rarely wear out
> their wheels.  Most freight cars spend most of
> the time sitting still, either being loaded,
> unloaded or sitting in yards.  So they can have
> the same wheels for their whole lives.  

That might have been true at one time, but freightcars in unit train and intermodal service today are constantly on the move and do wear out their wheels on a regular basis. It's become such a issue that some class 1 railroads have developed systems for changing out wheelsets without ever removing the car from the train. They are placed at key points along busy mainline.

https://www.youtube.com/watch?v=h6SAnp5V8sc

https://www.facebook.com/unionpacific/photos/a.374531983505/10155813786528506/?type=1&theater

Ted Curphey
Ontario, OR

Love the "100-ton conductor" comment... LOL

Greg Stadter
Phoenix, AZ