Axle Lengths on Wheelsets

Rocket Jones Apr 27, 2016

  1. Rocket Jones

    Rocket Jones TrainBoard Member

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    Silly question time. I notice that FVM wheelsets (for example) have axle lengths of .526, .540, .553, and .576. Why the differences? I guess my question is if these are direct replacements for various manufacturers, or is there something I don't know?
     
  2. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

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    Different manufacturers made trucks requiring different axle lengths.
     
  3. retsignalmtr

    retsignalmtr TrainBoard Member

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    Several months ago I bought FVM resistor wheelsets for Micro Trains trucks. They also fit supposedly Athearn. FVM and BLMA trucks. 33" wheels .540" axle length.Haven't used them yet. The package should tell you what MFG the wheels will fit.
     
  4. Rocket Jones

    Rocket Jones TrainBoard Member

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    Thanks. They're pricey - not surprising considering the precision - and I didn't want to be surprised if I bought a bunch to save a few bucks.
     
  5. Maletrain

    Maletrain TrainBoard Member

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    Bachmann, in particular, seems to have had a great deal of variation in their own wheel set axle lengths. They have typcally been on the long side, around .56[something]", but those on my roster ranged from 0.547" to 0.584", averaging about 0.565". (That 0.584" axle would not roll no matter what truck I put it into.)

    Fox Valley had some manufacturing problems with their 0.563" wheel sets somewhat over a year ago. See http://www.trainboard.com/highball/...le-lengths-not-as-expected.78751/#post-898215 . It affected both their 33" and 36" wheel sets in N scale, but only for the 0.563" axle length. The sets were advertized/marked as 0.563" but were really 0.572", which was about half way to the 0.576" models from the 0.563" model. Unlike the Bachmann wheel sets, which were all over the place on axle lengths in a single truck, even the off-spec Fox Valley wheel sets varied by only +/- about 0.001" from their average values. So, they seem to have been precisely manufactured to the wrong length, rather than poorly manufctured. Matt went through a lot of his wheel sets trying to find me sets that were so far off the 0.0572" average that they came within his acceptance tolerance of 0.005'" from his advertized value of 0.563" (which is what I had ordered). He was able to find enough of those in 36" wheels, but not in the 33" wheels. Matt was supposed to get back to me when he got new wheel sets from China that are actually 0.563" diameter, to replace those off-spec 33" sets. But, that must have gotten lost in the time-lag, because I have not heard anything from Matt since the end of the thread linked above.

    So, take-aways for you are that (1) you cannot decide what axle length you need for Bachmann trucks with "pizza cutter" wheels just by the manufacturer's name or even by measuring one or two of their wheel set axles from one of your cars, and (2) there are probably still a bunch of Fox Valley wheel sets for sale out there in both 33" and 36" models that actually have 0.572" axles marked as 0.563" axles. So, you are probably going to need a caliper that measures in 0.001" increments to make sense of the wheel replacement issues as you go through your roster. The important thing is to find a wheel set for each position in each truck that rotates easily without a lot of slop back and forth. Since the trucks are not very precise in most cases, you can probably find a new wheel set that fits well enough if it is within about 0.005" of optimum for a particular position in a particular truck, if you have a variety of axle lengths to choose from in your new wheel sets. The issue is to know what to order, and why a particular wheelset that you thought would work when you ordered it is not working OK when you actually installed it. You really need to be able to measure, because you can't rely completely on published averages or even package markings for axle lengths.
     
  6. Rocket Jones

    Rocket Jones TrainBoard Member

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    Thanks for the excellent explanation!
     

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