It’s been around along time, though not mass-produced until recently. Quoting from http://www.doubleogauge.com/history/History2.htm
‘Almost certainly the BRMSB had begun with HO and with the 1936 EF Carter/Constructor wheel set and standards. Carter had probably started with a 1mm flange way, then derived his wheel thickness using the formula “twice the flange way plus 0.3mm”.’
Today HO fine scale wheels are being provided on many ready to run models. These models run on existing coarse scale track. We can make fine scale track to match the fine scale wheels, thus improving the appearance of our track. This fine scale track will also work for many coarse scale wheels. Fine scale wheels combined with properly designed fine scale track gives superior performance compared to the coarser ready to run track, including track built to any of the old standards from the NMRA, BRMSB, AMRA or MOROP. The track and wheels are easier to make compared to the Proto 87 standard, yet the appearance is nearly as good, the most noticeable difference is the wider track flange way. Because the wheel flange is double the prototype, compensation or spring suspension is not necessary. Fine scale wheels also result in close to scale distance from the front face to front face of the wheels, allowing scale width of models to be built. Hennery Greenley, the person who defined H0 as 3.5mm/ft gave this as one reason to model UK models to 4mm/ ft using 16.5mm track, but that is another story. The only other standard that achieves this in H0 is Proto 87.
The problem with HO fine scale is up to now there has been no widely used standard. The NMRA fine scale recommended practice is not compatible with ready to run fine scale models and also does not achieve close to scale front-to-front wheel face distance. The fine scale standards published by the BRMSB were not well toleranced, causing potential rough running and lack of clearance between the wheels and track check faces.
The solution was to take a similar approach to those who developed the exact scale standards back in 1966, and develop a properly toleranced and defined standard. I did this back in 1994 after coming across a commercial website http://www.railwayeng.com/ offering fine scale track which used track with a gauge under 16.5mm. I looked at the ready to run fine scale wheels, and concluded they mostly used the NMRA wheel minimum back-to-back dimension and the NEM check gauge. This makes the wheels compatible with the coarse scale standards from most manufacturers of ready to run track. I looked at complex track rather than just simple turnouts, and developed standards which used the broadest possible tolerances to make manufacture of complex track easier. Below is the result, 2 fine scale standards, which are compatible with each other and with most ready to run H0 models.
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H0 Fine scale 1.00mm to 1.05mm flange ways |
H0 Fine scale 1.10mm to 1.20mm flange ways suitable for
mass production |
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Track Standard Design Notes
Because both these fine scale standards use the NMRA minimum wheel back to back, they also use the same NMRA maximum check face to check face dimension (NMRA span) of 14.3mm. This gives a minimum scaled down prototype clearance. The track gauge maximum and minimum only applies to the crossing V (frog) area. The theoretical maximum possible wheel outside flange to outside flange dimension is 16.02mm. This means the clearance between fine scale wheels and the track is larger than the prototype with gauge widening. This allows smaller than scale curves through the crossing V if you only use fine scale wheels.
A large variety of wheels will run through the above fine scale track, including wheels of coarse proportion. The coarsest wheels I have successfully run through fine scale track with 1mm 1.05mm flange ways is MOROP ‘cookie cutter’ wheels with a flange thickness of 0.9mm, 1.2mm flange depth with a regauged back to back of 14.4mm. NMRA RP 25-110 wheels usually work well, however the wheels need to be set close to the minimum back-to-back dimension. The KD HO wheel is one brand of these. These coarse scale wheels generally have flanges that are theoretically to wide if you measure the check gauge of the wheel at the same location on the flange that the prototype uses. For our model wheel profiles this measuring point can be different and depends on the flange profile. For example the straight cookie cutter flange profile’s check gauge can be measured close to the tip of the flange, without increasing the risk of derailment, however running wide flanges does decrease the absolute minimum clearance between the track and flanges. Correctly gauged for HO NMRA RP-88 wheels make a nice looking fine scale wheel, however the NMRA wheel profile is difficult to manufacture correctly, and the NMRA RP 25-88 flange depth is to small for long wheel base ridged H0 models on most layouts. My preference is to use the NMRA standard maximum for flange depth of 0.7mm. Wheels with a flange depth of 0.9mm will run on code 55 rail, but you only need one bit of ballast to cause the flange to bump
