Replacing modern stock freight car trucks (HO) - wheel diameters ...

[steveNCB7754]

This is really a 'supplemental' to the general query I raised back in March;

 

http://www.rmweb.co.uk/community/index.php?/topic/97739-replacing-the-stock-freight-car-trucks-and-couplers-ho-worth-doing/?hl=replacement&do=findComment&comment=1839556

 

Looking at a few of the freight cars I have already accumulated (box cars, centerbeam flatcars, etc.), many (most) seem to be factory-fitted with roller-bearing trucks with three prominent bolster springs.  Not surprising, as when I check-out reference photos online, of the full-size versions, they too have identical trucks.  As it happens, 'Model Railroader' magazine has a 'Guide To Freight Car Trucks' in the April 2015 issue, which identifies these trucks as ASF 100-ton Roller-Bearing (Ride Control) trucks.

 

Which is all well and good, but when I measure the various model's wheel diameters, they scale out at 33 inches, whereas Kadee only seem to supply the ASF 100-ton trucks, with scale 36 inch diameter wheels.  What's the deal here?  Do ASF 100-ton trucks ever have 33 inch diameter wheels, or are the manufacturers using a bit of licence here?

 

Does it make a meaningful difference, or is it nothing to worry about?

[Zomboid]

I don't know about the real thing, but where I've just bought some wheelsets, I made sure to get the same size as the ones that'll be heading to the bin (magnetic, no use...), so as not to compromise the coupler height. It'll only be about 0.5mm difference between 33 and 36 inch wheels though.

 

And since I don't know about the real thing it doesn't bother me. Yet.

[doctor quinn]

Check this thread out - http://model-railroad-hobbyist.com/node/3692

 

100ton cars usually have 36" wheels, but be aware that manufacturers may only make one roller bearing truck and use it under everything modern so you need to check the data printed on the side of the car.

 

 http://trn.trains.com/railroads/abcs-of-railroading/2006/05/freight-car-markingsmay help

 

I recall on Athearn Centerflow and Pullman Standard 100T covered hoppers Kadee #5s are too low with the stock 33" wheels so you need to change them out for the correct 36" ones.

 

Nick

[jasond]

Short answer - type of car: 100-ton = 36" whls, up to 70-ton = 33" whls.  Waffling starts here - sideframes.  I think 100-ton tks with 36" whls have a bigger curve of sideframe over the bigger bearings, so a more pronounced dip in the top centred on the bolster.  To excuse myself from any blame, I'm in O-scale.  33" US Hobbies r/b trucks had a straight sideframe top and Weaver/Atlas/etc with 36" have that dip.  Mind you the Atlas 33" r/b trucks have a bit of a d...... ah well, HO, it won't show so much, it's the car weight that's important.

 

I was looking at a few sites to see if Standard Car or others would have useful diagrams, but all that did was confirm the more I (get to) know, the more (I realise) I don't know. Oh and 125-ton cars get 38" wheels....

Great hobby

Jason