OO-SF tolerances and RTR wheel profiles

[Captain Kernow]

3 hours ago, PMP said:

The specific thrust here is that @Captain Kernow wants to use RTR products on track built to a set of OO society (I presume), specifications for OO-SF.

Alas, it's not quite as planned or as logical as that, Paul!

 

I felt at the time that the narrower flangeways would provide an improved appearance and I obtained a set of OO-SF gauges from C&L, as I recall. I certainly did not look any further into published OO-SF standards or any other OO standards for that matter.

 

Others had told me (certainly implied, in my interpretation) that 'any OO stock' would run on OO-SF.

 

I simply thought that it would all be as simple as that, although I was certainly not naive enough to just lay these points down first, without testing a range of my existing stock on them, before things got beyond the (practical) point of no return.

 

3 hours ago, polybear said:

Certainly there are numerous people using 00-sf (which shares the same flangeway gap of 1mm) with RTR Locos (Eastwood Town, for example).

One of the two examples of OO-SF track that I have checked one of the affected manufacturers locos on, was built by Gordon Stolliday (of Eastwood Town fame). The dimensions seem true to OO-SF, yet this loco binds on the 16.2mm gauge. I couldn't test the other two manufacturers locos on Gordon's track, because one had already been returned to the retailer by then (ran very poorly) and the other manufacturers' locos had already had their wheels substituted for others by that time.

 

 

[Captain Kernow]

3 hours ago, PMP said:

RTR models have never been supplied to be specifically compatible with OO-SF.

There’s no backward step, if an RTR release is/was compatible with a set of specifications not used by the manufacturers, it’s purely down to good fortune.

I agree that you can't blame any of these manufacturers for this, but it does introduce a frisson of uncertainty for me now when a new RTR release appears, especially if from one of the manufacturers I have noted (unless there is evidence that the new release has a different wheel profile).

 

This debate has also enlightened me to the other OO standards that some people are using out there.

 

Having said that, 'each to their own' seems to be the safest mantra. I don't build OO stock to run on other people's OO layouts, although it's nice if you can do so. I've always built or acquired stock to suit my own layouts, which seems to be a safer bet.

 

Perhaps it was naive of me, after all, to assume that all RTR products would be OK on OO-SF, but at least I know better now.

 

[polybear]

20 minutes ago, Captain Kernow said:

Others had told me (certainly implied, in my interpretation) that 'any OO stock' would run on OO-SF.

 

It would be safer to think "most recent** RTR stock" - though be prepared for the risk of disappointment/having to make adjustments at times. 

 

**By recent I'm guessing perhaps the last 15 years or so - at a guess I'd say the first release of the Horny Merchant Navy might mark the transition to finer wheelsets. 

 

For anyone not wishing to have any messing about then its commercial RTR Trackwork or, if you wish to go for a finer looking appearance then I suggest it'd be the DOGA Intermediate Standard.

[martin_wynne]

6 hours ago, Jeremy Cumberland said:

the aim is to have the back of one wheel on an axle hard up against the check rail and the flange of the other wheel being in the middle of the crossing flangeway

 

@Jeremy Cumberland

 

Hi Jeremy,

 

Not so. On both the prototype and model in 00-SF, when the flange on one side is running hard against the edge of the rail (i.e. not in the middle of the flangeway), the back of the opposite wheel should just kiss the check rail.

 

For RTR wheels (NMRA RP-25/110 profile) on 00-SF, the back-to-back should be in the range 14.3mm min - 14.4mm max. Many modern RTR models comply with this, but not all. An occasional rogue wheelset may need adjustment.

 

14.5mm b-t-b will be too wide on many RTR models, and may cause binding between the rails in 00-SF.

 

The 00-SF dimensions and advice on setting various wheels is at:

 

 https://85a.uk/00-sf/

 

The 00-SF standard (then called "EM minus 2") was invented by the late Roy Miller in 1973. It is just a happy accident that most modern RTR models run nicely on it. That wasn't the original design intent -- at that time RTR models were children's toys.

 

Martin.

Edited December 17, 2023 by martin_wynne