Drive wheel axle gauge variation

[TVRR]

Hi, Been checking over a Proto 0-8-0 switcher and measured the width of each pair of drivers at the rim.
   1st axle 0.4415
   2nd       0.440
   3rd        0.4388
   4th        0.435 axle with TT
How much variation in gauge should there be between pairs? I'm inclined to try and widen the rearmost axle to close to the 1st pair's. How have you approached similar issues?

[nickelplate759]

Hi, Been checking over a Proto 0-8-0 switcher and measured the width of each pair of drivers at the rim.
   1st axle 0.4415
   2nd       0.440
   3rd        0.4388
   4th        0.435 axle with TT
How much variation in width should there be between pairs? I'm inclined to try and widen the rearmost axle to close to the 1st pair's. How have you approached similar issues?

Are you really referring to gauge?   If so, get yourself an NMRA gauge in whichever scale you are working.  In theory they should all be the same, and they should match the NMRA gauge.

[TVRR]

Thanks for the input, could not think of the appropriate term. What is NMRA standard for N scale? I'll have to dig out my gauge.

[nickelplate759]

You want one of these.  Use the notches where it says "wheels" on the left side of the picture.
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Model Train Stuff sells them:
https://www.modeltrainstuff.com/nmra-98-8-standards-gauge-n-scale/?gclid=CjwKCAjwoP6LBhBlEiwAvCcthMFP7ScNLda63gcbuWai8dvEgSIFS79JUPwtGtmL1IYrbmFrST9O8RoCtoEQAvD_BwE

[peteski]

The NMRA gauge does come in very handy for checking and adjusting wheel gauge.  No need for measurements, just a visual check.

[mmagliaro]

A much more important measurement would be the back-to-back distance between the wheels, which according to the NMRA spec, here:
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/S-4.3%202010.02.24.pdf

should be 0.294" in N Scale.

The nice thing about using the NMRA gauge plate is that it also implicitly checks for flange depth and flange thickness.  And of course, it's just drop-in easy to use.

[peteski]

A much more important measurement would be the back-to-back distance between the wheels, which according to the NMRA spec, here:
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/S-4.3%202010.02.24.pdf

should be 0.294" in N Scale.

The nice thing about using the NMRA gauge plate is that it also implicitly checks for flange depth and flange thickness.  And of course, it's just drop-in easy to use.

That might not be the ideal measurement to check.  The new Rapido Comet wheels are perfect example.  Here is a photo of Kato and Rapido wheels.
As you can see Rapido has much deeper (and much "fatter") flange.  If we gauged the wheels using the back-to-back distance, the Rapido wheelset would be wider at the point where the flange merges into the tread.



Back-to-back measurement is good to use when the wheel profile also adheres to the NMRA specs (and the new Rapido wheels clearly do not adhere to those specs).  As you said Max: use the NMRA gauge.

[TVRR]

Thank you guys, gotta dig out my gauge. In the event that they require adjustment, what is the approved method(s)?

[nickelplate759]

If the gauge is too wide, you can tap gently on the wheel to move inwards.   Use a piece of tubing to go around the end of the axle (tapping on the axle won't help), and tap on the tubing.   You must support the far end of the axle on something hard. Check gauge frequently.   Be gentle and use a light hammer (not a 10lb sledge)!   

If the gauge is too narrow, I prefer to use a gear puller, but that usually means removing the wheelset from the car or engine.  For steam engine spoked drivers,  there's a risk that the gear puller will damage the spoked part of the wheel - depends on the gear puller. 

The NWSL gear puller has a slotted plate and should be OK, but the watch-gear pullers that grab the edge of the wheel might not be so good.

In that case,  hang the wheelset through a slotted plate (like you would use with a jeweler's saw), and tap on the axle end (not the wheel) to widen the gauge.

Again - check gauge frequently!

[mmagliaro]

I would argue that if the flanges are sloped that severely (like that Rapido set), your dead.  The back-to-back distance is important in order to correctly clear through switch frogs and guard rails.  If you pulled them in narrower to compensate for that heavy slope on the flanges, you can start having other problems with the treads dropping in off the insides of rails.  And note that the NMRA plate notches will be fitting on the outer edges of those flanges, so the gauge will still mostly be setting the width according to outside edge, not taking that heavy slope down to the tread into account.