On2 Mounted Wheel Standards

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The picture above shows a selection of Maine Two Foot prototype wheelsets at the Sandy River Museum in the mid 1990’s.

In the following table, we show three different wheel standards compared to prototype dimensions derived from measurements of photographs and also a sample of measurements taken from commercial wheelsets. The ¼AAR for Two Foot Gauge – 1966 and the NMRA – 1974 Standards are included for historical purposes, as they reflect the standards in place when many of the brass locomotives and rolling stock were first produced.

Experience has shown that the back to back measurement of the wheels is most critical single dimension that affects the running of On2 trains through pointwork, and paradoxically this is also the dimension which is most likely to vary outside the control limits of the various specifications.

The table can be enlarged by clicking on it.

On2 wheel standards 2016-01

Notes

1/. Scaled from known object placed on central plane of wheelset.

2/. Scaled from track gauge with allowance for perspective.

3/. Measurements based on set of 4 wheelsets bought in the mid 1990’s. Measurement accuracy estimated at +/- .002 inches.

5/. By calculation.

7/. Back to back variation in a wheelset: three wheelsets had no measurable variation, one had .006” variation. This wheelset showed wobble on the insulated wheel.

8/. Back to back variation in a wheelset: all four wheelsets showed variations ranging from .002” to .005”. Three wheelsets showed wobble on the insulated wheel, one on the un-insulated wheelset.

9/. Back to back variation in a wheelset: one wheelset had no measurable variation, three wheelsets showed variations ranging from .002” to .003” and wobbled. Larger variations in measurement between set of four wheelsets, as expected by use of injection moulded axle with double shoulders. (Range of .018” versus .010” for NWSL and Portland Products).

10/. Back to back variation in a wheelset: wheelsets showed variations ranging from .003” to .024” and wobbled. Larger variations in measurement between set of four wheelsets, as expected by use of injection moulded axle with double shoulders. (Range of .027” versus .010” for NWSL and Portland Products).

Grandt Line Wheelsets.

The original Grandt Line On2 wheelsets consisted of metal rims with cast plastic centres featuring ribs on the back of the wheel and a moulded half axle outer profile with a steel functioning axle.

A later version was produced using the metal rims and cast centre only with a moulded plastic functioning axle. This combination can give problems with true running of the wheels, and most serious operators at the time chose to upgrade to NWSL wheelsets.

Grandt followed suit and supplied their freight truck with NWSL wheelsets. More recently Grandt has chosen to supply their freight truck without wheels.

Sample locomotive back to back wheel dimensions.

The following data was provided by Terry Smith from his own locomotives;-

Portland Products, F&M #1, from the front;-   .422 – .426 – .430 – .432

Putnam & Stowe, SR #2,     .417″

The Car Works, WW&FR #7, from the front;-   .417 – .4145 – .4205 – .4105 – .4105

The Car Works, B&SR #6, from the front;-   .410 – .412 – .4165 – .4115 – .4115

The Car Works, B&SR #7, from the front;-   .4025 – .4175 – .4135 – .408 – .4135

The Car Works, B&SR #8, from the front;-   .415 – .4165 – .422 – .413 – .413

Custom Brass, SR&RL #6 (1) , from the front;-   .4195 – .425 – .418 – .4165

Custom Brass, SR&RL #6 (2) , from the front;-   .420 – .421 – .421 – .419

Custom Brass, SR&RL #6 (3) , from the front;-   .424 – .421 – .415 – .4155

Custom Brass, SR&RL #6 (4) , from the front;-   .421 – .426 – .416 – .4155

Custom Brass, SR&RL #24,   .413″

 

Is “On2” P48, Proto 48 or Finescale? No, not according to current NMRA definitions or Standards. Click here for more details.

Updated 22 – May – 2016, 28 – May – 2016 and 20 – August – 2016.

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