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Rolling stock wheel size

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  • Member since
    January 2019
  • 2,572 posts
Rolling stock wheel size
Posted by John-NYBW on Friday, January 10, 2020 11:03 AM

Walthers sells both 33" and 36" diameter metal wheels. When I first began replacing the plastic wheels that come on most freight car kits, I just bought the 36" without giving it much thought. Recently in my spare wheel drawer I noticed that somewhere I got the smaller wheels. I didn't think a difference of 3 scale inches (HO) would be that noticeable but it's easy to tell them apart at a glance. I know I don't want to mix wheel sizes on the same car but I'm wondering if in the future I should buy the 33" wheels instead. Is one more prototypical than the other and does one operate more reliably than the other. 

Most of my passenger car fleet is RTR that came with metal wheels so I haven't had to replace any but if I should acquire some with plastic wheels, which size would be the better choice for passenger cars. 

  • Member since
    May 2010
  • From: SE. WI.
  • 8,253 posts
Posted by mbinsewi on Friday, January 10, 2020 11:45 AM

I think it matters on what time period your modeling.  I model "modern", so just about everything gets 36", except the A and B ends of a container car set.

Not 100% about this, but any car that grosses 100 ton gets the 36", and 33" for 70 ton cars, which can be time period related.

Also, depending on the time period, is the wheels with the fluted backside, or the smooth.  Fluttered wheels not allowed after a certain time.

When I am unsure, I do a search for the prototyp that I am modeling.

The difference in diameter can also affect the couplers.

Mike.

  • Member since
    January 2017
  • From: Southern Florida Gulf Coast
  • 18,255 posts
Posted by SeeYou190 on Friday, January 10, 2020 1:01 PM

mbinsewi
any car that grosses 100 ton gets the 36", and 33" for 70 ton cars, which can be time period related.

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That is about as good an explanation as I could give.

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Generally cars 70 tons and less are 33 inch wheels, cars 100 ton and up as well as most passenger cars are 36 inch wheels.

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Once the wheel is in a truck, I doubt anyone would ever notice.

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I have been known to put 36 inch wheels in 50 ton trucks to raise coupler height just a bit.

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-Kevin

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Living the dream.

  • Member since
    September 2014
  • From: 10,430’ (3,179 m)
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Posted by jjdamnit on Friday, January 10, 2020 1:23 PM

Hello All,

As a general rule of thumb the larger the wheels the smoother the ride.

In the prototypical world, most passenger cars use 36-inch wheels.

As has been noted freight cars, depending on capacity, will use either 33- or 36-inch wheels.

Intermodal cars typically use 28-inch wheels. The smaller wheel size gives a bit more height clearance and the ride quality is not as important as on passenger cars.

Kadee and Intermountain both make 28-inch wheels.

Using different wheel sizes can compensate for misaligned couplers without having to use shims between the trucks and the frame making the car too top-heavy or "tippy".

Hope this helps.

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

  • Member since
    November 2013
  • 2,775 posts
Posted by snjroy on Friday, January 10, 2020 1:39 PM

Size matters for sure, especially if you try to fit 33 inch wheels in trucks designed for 36 inch wheels. They might fit, but the trucks will drag and hit things on the track. Generally speaking, 3 axle trucks will require 36 inch wheels. Anything longer than 60 scale feet usually requires 36 inch wheels as well. But the best method is to basically measure the wheel diameter (not the flanges) of what you want to change, and match them with the replacing wheel set. I always have spares of both sizes on hand for that purpose.

Simon

  • Member since
    January 2017
  • From: Southern Florida Gulf Coast
  • 18,255 posts
Posted by SeeYou190 on Friday, January 10, 2020 4:29 PM

snjroy
Size matters for sure, especially if you try to fit 33 inch wheels in trucks designed for 36 inch wheels. They might fit, but the trucks will drag and hit things on the track.

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Yes, and if the trucks are metal, you will end up with a very difficult to isolate intermittent short circuit.

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-Kevin

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Living the dream.

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