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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More interesting websites – locomotive suspension and performance

Here are a couple of non “On2” scale websites that may be useful to viewers interested in improving locomotive suspension and performance;-

http://www.clag.org.uk/41-0rev.html

This is a UK site which presents an overview of the work done by various individuals and groups on advanced but practical locomotive suspension methods used by the UK Fine Scale and Prototype based groups primarily in 4mm scale. It’s quite a site, with a lot of content, and probably more than most modellers will ever need or feel comfortable with. The physical size of these models is close to Maine On2, and many commercially available parts (such as motors, gearboxes, axles and hornblocks etc.) can be used.

http://hon2jeff.blogspot.co.uk/

This is a link to Jeff Bissonette’s blog where he posts mainly about his work on making chassis’s for various locomotives in the smaller scales such as Sn2, HOn3, HOn2 and OO9. There is a wealth of practical information (and inspiration I hope!) in the older posts, much of it applying the principles of the site above. Jeff’s comments about Sn2 loco’s and their performance and how he improved these are worth reading for their close similarity with products offered commercially in On2.

Enjoy if you visit.

Coupler offsets and angular mis-alignments on curves

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The picture above shows a model of a B&SR 26 foot boxcar (left) and a model of a B&SR 34 foot flatcar (right) on a piece of Precision Scale flex track curved to a 48″ radius on the centreline.

The table below lists the calculated coupler offset (radial displacement from the nominal centreline) and angular mis-alignment (angle between the coupler centreline and the track centreline at the coupler position) for a selection of Maine Two Foot rolling stock on curves of various radii. Note some pieces of information are missing. Modellers in scales other than 1:48th should note that the figures below have been calculated from scaled dimensions and geometry only. They do not include any allowance for wheel-set clearance within on the track gauge, and can therefore be scaled up or down for different modelling scales.  

The intention is to show how these parameters increase with decreasing radii.

Curve Coupler Coupler Coupler Coupler
radius Radial Radial Angle (F) Angle (R)
(ins) offset (F) offset (R)

(degrees)

(degrees)

Boxcar #47

30

0.138

7.05

Boxcar #73

30

0.161

8.82

Coach #17

30

0.367

12.32

Coach #18

30

0.313

11.40

Loco, #7 & #8

30

0.137

0.450

5.61

10.02

Boxcar #47

33

0.125

6.41

Boxcar #73

33

0.146

8.01

Coach #17

33

0.334

11.18

Coach #18

33

0.285

10.35

Boxcar #47

36

0.114

5.87

Boxcar #73

36

0.134

7.34

Coach #17

36

0.306

10.24

Coach #18

36

0.260

9.48

Loco, SR&RL #6

36

0.065

0.224

3.55

6.46

Loco, #7 & #8

36

0.114

0.375

4.67

8.35

Boxcar #47

42

0.098

5.03

Boxcar #73

42

0.115

6.29

Coach #17

42

0.263

8.76

Coach #18

42

0.224

8.12

Loco, SR&RL #6

42

0.056

0.193

3.04

5.54

Boxcar #47

48

0.086

4.4

Boxcar #73

48

0.100

5.5

Coach #17

48

0.229

7.66

Coach #18

48

0.195

7.1

Loco, SR&RL #6

48

0.049

0.168

2.66

4.84

Loco, #7 & #8

48

0.086

0.282

3.51

6.26

Boxcar #47

60

0.069

3.52

Boxcar #73

60

0.080

4.4

Coach #17

60

0.180

6.12

Coach #18

60

0.156

5.67

Loco, SR&RL #6

60

0.039

0.135

2.13

3.88

Loco, #7 & #8

60

0.069

0.226

2.8

5.01

Boxcar #47

120

0.034

1.76

Boxcar #73

120

0.040

2.2

Coach #17

120

0.092

3.06

Coach #18

120

0.078

2.83

Loco, SR&RL #6

120

0.019

0.067

1.07

1.94

Loco, #7 & #8

120

0.034

0.113

1.4

2.5

1/. Rolling stock refers to B&SR/B&HR examples unless otherwise noted.

2/. Boxcar #47 is a 26 foot long boxcar with 18ft 6in truck centres. This is the shortest example of normal revenue carrying freight car found on the B&SR/B&HR. Similar sized freight cars were common to all Maine Two Footers.

3/. Boxcar #73 is a 34 foot long boxcar with 27ft 6in truck centres. This is the longest example of revenue carrying freight car found on the B&SR/B&HR, and on any of the Maine Two Footers.

4/. Coach #17 is a 48 foot 9 inch long coach with 34ft 9in truck centres. This is the longest member of the passenger car fleet of the B&SR/B&HR, and is fairly representative of a number of B&SR/B&HR and SR&RL stock.

5/. Coach #18 is a 46 foot long coach with 32ft 6in truck centres. This is the shortest member of the passenger car fleet of the B&SR/B&HR.

6/. Loco #7 & #8 are Big 2-4-4T Forney type locomotives, prototypes weighed 32/35 tons and measured just over 33 feet long. These are the largest of the Two Foot Forneys and similar sized locomotives were found on the SR&RL system.

7/. SR&RL Loco #6 is a small 0-4-4T Forney type locomotive, the prototype weighed around 15/18 tons and measured 25 feet 6 inches long. This is a typical Maine Two Foot Forney, and similar sized examples were found on all lines.

Couplermis02

The picture above shows the front of SR&RL Locomotive #6 (left) and a B&SR 34 foot flatcar (right) on a piece of Precision Scale flex track curved to a 48″ radius on the centreline.

Couplermis03

The picture above shows the rear of SR&RL Locomotive #6 (left) and a B&SR 34 foot flatcar (right) on a piece of Precision Scale flex track curved to a 48″ radius on the centreline.

Minimum radius, big Forneys and tight gauges, – some numbers!

Terry Smith’s Historical Maine On2 loco and track curving experience,     2013 version 3.

Terry Smith has provided the following historical data from his own tests and experience. It is a more complete version written up for these FAQ’s in October 2013 from additional notes, dating from 1995 to 2004, which were recently re-discovered and both supercedes and finishes his series of previous posts to the MaineOn2 Yahoo! Group on this subject.  

Minimum radius: in my On2 “tyro” days (around 1988-90), I did a lot of tests on different locomotives and their curving ability as part of my layout design. My then available space had a restriction close to one corner which meant that being able to use a 36″ minimum radius would be particularly “useful”.

I had attended a number of the early Whitman meets, and in talking with other On2 modellers, I was aware that if I wanted to run the Big Forneys (B&SR/B&H #7 & #8, SR&RL #10) that the advice was to try to use a 42 or 48″ minimum radius.

I set up test radii using Precision Scale flextrack on Sundeala board (our UK favourite for proper track pin retention, believed to be denser than Homasote). I laid out different radii (60″, 48″, 42″, 36″, 33″, 30″) and repeatedly ran each loco forwards, backwards, curving to left and to right, with and without freight cars attached.

Based on these series of tests I selected 36″ as my minimum radius, and then started to build the layout proper with hand-laid track, code 83 rail, Clover House ties, Railcraft spikes plus turnouts using #6 frog angles and constant radius curvature through the point/switch……..and then started having running problems!.

The problems arose with both the Car Works B&SR #7 & #8 derailing fairly regularly on the first point/switch after the particular corner when running in a “clockwise” direction. I was disappointed to say the least. There were no kinks in the curve and it had sort of transitions into it.

 After a lot more testing and observations, I found that the problem was that one of the rear drivers was consistently riding up onto the inside rail and ran like this on the plain track until de-railing at the first point/switch. I put this strange behaviour down to some artefact of vertical stiffness/motion problems between the drivers and the rear truck, and possibly not enough weight on the drivers. On one of the loco’s, probably the #8, I packed the springs with shims and reduced but never eliminated the derailing tendency.

 The table below lists the summary of experience to that point

 Loco type          Example                       Track                                        Experience

 

Small Forney     CB SR&RL #6               Precision Scale flex 36″ rad        OK

Big Forney        Car Works B&SR #7        Precision Scale flex 36″ rad        OK

Big Forney        Car Works B&SR #8        Precision Scale flex 36″ rad        marginal

Big Forney        Car Works B&SR #8        Precision Scale flex 48″ rad        OK

Prairie               CB SR&RL #16              Precision Scale flex 36″ rad        OK

 

Medium Forney Car Works B&SR #6         Precision Scale flex 48″ rad        OK (*)

Medium Forney Car Works WW&FR #7     Precision Scale flex 48″ rad        OK (*)

Big Forney        Car Works B&SR #8        Precision Scale flex 48″ rad        OK (*)

 

Small Forney     CB SR&RL #6               Hand laid 36″ rad                       OK

Big Forney        Car Works B&SR #7        Hand laid 36″ rad                       marginal

Big Forney        Car Works B&SR #8        Hand laid 36″ rad                       not OK

Prairie               CB SR&RL #16                Hand laid 36″ rad                       OK

Small Forney includes the Putnam & Stowe 0-4-4 locos, the Portland Product 0-4-4 locos and CB SR&RL #6. 

Medium Forney includes the more recent 2004 production Car Works B&SR #6 and Car Works WW&FR #7. I have no experience with the CB Eustis Forneys.

(*) Tests done in 2013

Big Forney includes the Carworks B&SR #7, Carworks B&SR #8 and by close similarity the equivalent SR&RL #10.

Prairie includes the CB SR&RL family such as #16, #18 & #24, but does not include The Car Works #23.

Experience definitions:

Ok; suitable for layout operations.

Marginal; occasional failure, loco either stalled or derailed frequently enough to give raised concerns when operating layout.

Not OK; consistent failure, loco either stalled or derailed frequently enough to give sufficient concerns for it not to be used when operating layout.

What went wrong?

My original thoughts in the 1990’s were that perhaps the original tests were flawed, in that the flex-track was pinned down, but perhaps not in enough places, and it could have retained sufficient lateral “displacement capability” to allow the big Bridgton engines to get round a nominal curve of 36″. By comparison, the hand-laid track on the layout was rigid.

Sometime later (around 2006-2008) I got around to measuring the track gauge at various places with a two point dial calliper.

Results;-

Hand-laid track

My handlaid straight track measured .495-.510″ gauge, the transition curve measured .505″ and the 36″ radius curve measured .500″ to .514″, but most measurements were grouped in the .500″ to .502″ range.

In comparison Precision scale flex track measures around .510-.515″, and does not get below .508″ when curved to 36″ radius.

For reference, the current NMRA standard (S-1.2 dated July 2009) for On2 plain track gauge is .500-.522”,  and for “Guarded work” (presumably pointwork in my language) (S-3.2 dated February 2010) the gauge at frog is .500-.511″. I believe that Fast Tracks set up their switch building jigs to a nominal track gauge of .510-.512”.

My current conclusion based on the gauge measurements and repeated tests is that the problem with the hand-laid track on the former layout was that it was too tight in gauge for the curve radius, and particularly so for the Big Forneys.

And finally what went right with the pointwork?

The curious thing with all this testing and problems is that I do not recall ever (apart from above exceptions) having problems with any loco’s derailing or having problems with negotiating my pointwork, which initially were based on #6 frog angles and constant curvature through the point/switch.

Inspection has showed that my handlaid pointwork measured .493-.505″ gauge with the two point dial calliper. However, each point was individually built in a home made jig using the same code 83 rail as for the plain track except that I used Clover House PCB ties so that the rail could be soldered to the ties. Each point was tested and adjusted during building on the workbench and also when fitted in place on the layout.

I now suspect that this testing and adjustment regime explains why the locomotives could successfully negotiate the pointwork.

As an experiment, two points were made to larger radii. These measured close to #8 frog angle and had a constant radius of around 48”. They gave much smoother running and operation than the #6’s.

Personal conclusion

I had tried some modifications to the rear trucks of both my #7 & #8, these may have been successful for #7, but not #8 in terms of consistently getting round a 36″ radius.

When I experimented with a laminated spline roadbed (from Sundeala) I used a 48″ inch radius with a decent transition curve on entry and was surprised at just how well #8 looked and operated.

curv04

Rather than spend more time trying to persuade these iconic loco’s round tighter curves, I have chosen to use Precision Scale flex track, a minimum radius of 48” and pointwork built on a Fast Tracks #8 jig for the new layout.

Click here to view the related topic “Locomotive model minimum radius” on another page.

Click here to view the related topic “Coupler offsets and angular mis-alignments on curves” on another page.

Written by Terry Smith 12-10-2013, amended 14 & 17 & 22-10-2013. Updated: 25-May-2016 and 26-08-2016.

 

What is “On2”?- plus NMRA Standards

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The picture above, taken at Edaville, Massachussetts shows typical Maine Two Foot style track and rolling stock amid a collection of other gauged items.

What is “On2”? By customary US model railroad terminology, On2 is the term used to denote the modelling of two foot (narrow) gauge railways in American O scale (1/4″ scale or 1:48th).

As used in these FAQ’s, it means modelling the Maine Two Footers in American O scale (1/4″ scale or 1:48th), resulting in a nominal model track gauge of 0.500″ (half an inch).

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

Whilst the actual nominal track gauge modelled is an accurate translation of the prototype practise by the scale, the other track and wheel standards are not derived from prototype practise as required by current NMRA definitions.

Click here to view the NMRA Proto Scales pdf TN 1 1 2 for S-3.1 and S- 4.2 which gives a listing of proposed dimensions for Proto Scales track and wheel standards – note the absence of On2!

View the NMRA documents which do list On2 dimensions for further information;-

Click here to view NMRA S 1.2 – General standard scales, which gives a listing of modelling scales and the basic track gauge used.

Click here to view NMRA S 3.2 – Scale track, standard scales, which gives a listing of track dimensions controlling pointwork etc.

Click here to view NMRA S 4.2 – Scale wheels, which gives a listing of mounted wheel dimensions.

 

Written by Terry Smith 13-Aug-2013, updated 03-12-2013, 01-05-2016, 20-08-2016 and 08-February-2017.