"Back to back" wheel gauges and track gauges (particularly N gauge)

[Justin Smith]

On my N gauge layout my diesels run well, de-railing wise, but steam engines tend to be less reliable (particularly front bogie de-railing) and a Dapol A4 I have just bought is especially poor.
I have been doing a bit of research and it seems advisable to buy a "track gauge" (roller type ? ) and "back to back" wheel gauge.

A few of questions please !

Are these items worth getting ?
Are any particular types / models the best ?
If derailing occurs in the middle of points how can track gauge be checked with a roller type gauge and how can the gauge in the middle of a point be altered anyway ?
On the subject of "back to back" wheel gauges, surely their accuracy depends on the thickness and shape of the flanges ? How can the internal dimension "back to back" dimension be a reliable indicator of the more important distance between the flanges ? Plus it's not just about the thickness of the flanges its their shape, where does the rail head actually touch the flange ?

 

[edwin_m]

The back to back is an important dimension, on real railways as well as models. It essentially determines whether a wheelset can pass through a set of points, where one wheel needs to go through the crossing gap and the other goes between the checkrail and the running rail. If the wheels are too close together then they can't both do that at the same time and one will derail.

The geometry of the outside of the wheel is less critical, because the coned shape of the tread means there is some tolerance on where it sits on the rail. All but the very oldest N gauge wheels should be to a similar profile anyway, so if the back to back is right the front of the wheels should take care of themselves.

I have a back to back gauge which came from the N Gauge Society I think, not sure if they still do one. It's just a brass cylinder with perpendicular slots so it can be used on a wheelset with a drive gear. It's possible to push the insulated wheel outwards (I think there's a special tool for this but I found normal tools were fine, can't remember exactly how I did it) then squeeze them in against the gauge (I used a vice I think).

I doubt a roller track gauge is much use except in the construction of hand-made track. If you're using Peco or similar then the track gauge is what it is and should be accurate.

 

[Justin Smith]

The back to back is an important dimension, on real railways as well as models. It essentially determines whether a wheelset can pass through a set of points, where one wheel needs to go through the crossing gap and the other goes between the checkrail and the running rail. If the wheels are too close together then they can't both do that at the same time and one will derail.

The geometry of the outside of the wheel is less critical, because the coned shape of the tread means there is some tolerance on where it sits on the rail. All but the very oldest N gauge wheels should be to a similar profile anyway, so if the back to back is right the front of the wheels should take care of themselves.

I have a back to back gauge which came from the N Gauge Society I think, not sure if they still do one. It's just a brass cylinder with perpendicular slots so it can be used on a wheelset with a drive gear. It's possible to push the insulated wheel outwards (I think there's a special tool for this but I found normal tools were fine, can't remember exactly how I did it) then squeeze them in against the gauge (I used a vice I think).

I doubt a roller track gauge is much use except in the construction of hand-made track. If you're using Peco or similar then the track gauge is what it is and should be accurate.

Excellent, I hadn't thought of that so much !

Is there any advantage to using a back to back gauge over a set of verniers ? Is it 7.5mm the "back to back" should be ?

On the subjact of the track gauge there may be some use for one. I have found if my track suffers derailments, particularly on plain track, it's often cured by tweaking the ends of the tracks (possibly where two different makes of track join) where the gauge at the join has changed, esp if sleepers have had to be removed to get the rail joiner on. But farting about with a set of verniers, esp if there's scenery / buildings about, can be awkward so a roller gauge sounds like it'd be handy to easily check the alignment.