Wheel-rail interface including back-to-backs

[Mountain Goat]

The gentleman (From what he relates to via the stock he runs) uses finescale track. Now he does mention the wheel profile. There is a little more to it as if any of you have tried them on ordinary code 100 00 gauge track, nothing seems to run as well as a metal wheeled Lima coach or a silver seal wheeled Hornby coach (If they dont have wheel wobble. The round axled silverseal wheels are less prone to issues) if the code 100 track has the flange ways of a suitable depth and tolerance to accept them. Why? Because the wheel profiles get to work on thew corners. The sideways play is necessary to allow the wheel profile to do its work. Little play means the curved profile can't tilt the coaches inwards at the corners and therefore doesn't get to do much.
It is interesting how things have changed. True, today's metal wheels keep lovely standards where it is rare to get wheel wobble. One does however still get poor wheel profile causing issues, and of course, the back to back issue.
Today's pointwork, even in code 100 is less tolerant to older wheels as they try to cater for modern finer wheels. Now flange depth does matter for two reasons. Too deep and ones wheel will ground on the bottom of the flangeways causing the wheels to jump when they hit frogs. Too shallow and they can't cater for any misalignment at the track joins. Any slightly larger gap between the joints or anything which may need a more sudden direction change will be less likely to stay on the rails if there is not sufficient flange depth to hold the wheels on the rails. Its a bit of compromise between too much or too little.
While I say nothing runs as well as the old Lima coaches with metal wheels (00 gauge), if one doesn't have track which is built to cater for them (Finescale track does not) then they won't run well, and likewize, modern finescale stock built for finescale track may not like running on non finescale track.
Here is where the horses for courses comes into play. Why dont we all adopt finescale wheels and finescale track? Well, we can if we want to. But why were models made with deeper flanges and a more pronounced profile in the first place, not to mention more play for the profile to do its job?
Well consider this. The older standards were made so that layouts could fit in a small space. The first radius curves were (And still are) a Godsend to many who simply dont have the space to use larger radius curves. Now with finescale wheels and curves, they really need second radius as a minimum to be happy. They will run on tighter curves if the design of the loco or rolling stock allows them to, but try running them at speed! Yet older stock with their more generous allowances will run at speed round sharp curves.
That's why I say horses for courses.

Plastic wheels. We all prefer metal wheels so why were plastic wheels so popular? Well, years ago in 00 gauge the majority of modellers who could afford them ran Hornby Dublo 3 rail. These were all metal regarding their wheels so didn't need isolating from one wheel to another. However, with the push to adopt 2 rail, plastic wheels were one of the main solutions to keep one wheel isolated from the other. They became so popular that for years plastic became the main material used with rolling stock despite their issues. Some say that plastic wheels are prone to attracting the dirt but to be fair, the dirt comes from dirty track. Plastic wheels are more likely to pick up this dirt from the track while metal wheels are more likely to leave the dirt on the track rather then pick it up. The dirt still needs dealing with be it on wheels or be it on track as if it is not on plastic wheels it will be preventing the locos from running...
Here is the larger issue with plastic wheels. Untrue wheels. Just like metal wheels being good or bad depending on their quality, plastic also varies. I've seen some very good true running finescale plastic wheels and I've seen others which even puzzles me how the things stayed on the track!
Generally metal wheels are better for their nice rolling weight and their metal pin point axles. Better quality plastic wheels mostly have metal axles but they are normally lighter in weight. The weight does make a difference. Metal Lima wheels run well (On siutable track) because they have good rolling weight (If one isn't taking account of other aspects). Romford wheels are lovely and heavy (The disc and 3 hole disc wheels. Spoked less so) and are finescale with lovely profile mixed in and run well both on finescale and non finescale layouts. Is a shame Romford dont still make wheels as they used to be a good price as well.

[Brian]

A lot of information can be found on UK OO standards on the Double O Gauge Associations web site... http://www.doubleogauge.com/standards/index.htm Intermediate measurements are the UK standards for Hornby/Bachmann/Dapol/Heljan etc and Hornby & Peco track systems