Gorre and Daphetid

Good luck then, Erik. :-)

"I will continue to extract satisfaction"? What is he, the villain in a nineteenth century penny dreadful? Snidely Whiplash? I didn't think wrote in such archaic language anymore. More evidence that Flynn lives in another dimension.

Yeah, someone who sees right through Flynn's nonsense antics.

A bloke with Asperger's syndrome, methinks.

That worked. Thanks. Gene ABV61-1043.001.HCB

"Skinny Dipping and Other Stories" On the web at or and look for "Into Joy From Sadness" soon.

What I am telling you is the way you have interpreted and defined the prototype dimensions on your web page is incorrect. You have made the mistake of using the overall gauge variation without correctly including the maximum check face to check face dimension. If I build to your dimensions as described on your web page I can get a clearance problem. The prototype will have different track gauge dimensions for each type of crossing. It still does not change the fact your standard on your web page has a fundamental mistake and therefore I conclude it exceeds the Danish maximum check face to check face dimension. There are common sense reasons why the P-45 standard is slightly different to exactly scaling down the prototype, it should make things easier to build. The Scale seven standards also are not exact..

Using your check gauge values and wheel back to back the following numbers work for all track.

Lets call it Danish proto 45

Track gauge 32.05mm to 32.1mm Flange way gap 1.1mm to 1.05mm

Minimum clearance between check faces and wheel back to back is 0.2mm, double what is proven to work in HO for scale curves. That's it. I still don't like the small margin for error in the check gauge.

Is your wheel profile a scaled down Danish profile? Just interested.

Which exact scale track standard are you talking about. So called exact scale standards deviate from exact scale by a small amount. Scaling down to small scales exactly is impractical, that's why Eric's numbers on his web page don't add up.

No practical model railway track standard works to such tight tolerances.

Terry,

In my case it is the UK S scale standards where the only deviation from an exact scaling down from prototype is a difference of ONE thou in the gauge - i.e. 0.884" instead of 0.883". Otherwise every other measurement on track and wheels is the prototype divided by 64. Those standards have been in existence for 40 years and have been proved to work by the appearance at exhibitions of many working layouts built to the standards over the last few decades.

The only 'compromises' that creep in are usually where it is accepted that measuring and manufacturing to an accuracy of more than three decimal places of inches or two decimal places of millimetres is usually beyond the capabilities of the hobbyist, but these compromises are within the tolerances used on the prototype when scaled up. The 'compromise' in UK S Scale was to allow for 0.010" clearance between flange and rail rather than the 0.0095" of the prototype, which gives the additional thou on the gauge.

I also model in UK Scale7 which is the exact scale standards for 7mm (0 Scale) modelling. The standards are published on the web at

It's a framed web site so I can't point you at the exact web page, but follow the 'About S7' menu link on the left to get to the standards pages. There you will see that we use the prototype measurements to the nearest two decimal places of millimetres. These standards have been in existence for well over thirty years and do work - again proven by the construction of stock and layouts to prove the point.

So it depends on what you mean by deviation. The deviation in UK S Scale is very minimal and the deviation in UK Scale7 is, basically, getting rid of the third decimal place in scaled down measurements. But looking at the standard of Erik Olsen's modelling, you might deduce that he has the capability to model to 1:45 scale exactly.

Jim.

They are not meant to be compatible with earlier standards.

Absolute check rail face to wing rail face maximum is 32.11 - 0.91 -

1.09 = 30.11 mm.

No.

Check rail face to wing rail face maximum was 1355 mm for Danish State Railways (DSB) circa 1930. The current UIC check rail face to wing rail face maximum is 1356 mm.

Wheel set back-to-back minimum is 1357 mm. This corresponds to the UIC value for wheel diameter 1000-840 mm.

It is, from DSB about 1920. The current profiles match the UIC profiles.

For your information, I have compiled the following specifications for DSB and UIC track and wheel sets (a few values have been changed during time):

Track standards: Track gauge nominal 1435 mm (31.89) Track gauge minimum 1432 mm (DSB) (31.82) Track gauge maximum (rail crossings) (DSB circa 1955) 1445 mm (32.11) Track gauge maximum (rail crossings) (DSB circa 1980) 1440 mm Track gauge maximum (plain track) (DSB) 1470 mm (32.67) Gauge widening (299-250 m curve radius, DSB) 5 mm (0.11) Gauge widening (249-160 m curve radius, DSB) 10 mm (0.22) Gauge widening (159- m curve radius, DSB) 15 mm (0.33) Crossing flangeway minimum 49 mm (DSB circa 1930) (1.09) Crossing flangeway minimum 45 mm (DSB circa 1980) (1.00) Check rail flangeway minimum 41 mm (DSB) (0.91) Check rail flangeway minimum 40 mm (UIC) Check gauge nominal 1395 mm (UIC) Check gauge minimum 1393 mm (UIC) Check gauge nominal 1394 mm (DSB) Check gauge minimum 1391 mm (DSB) (30.91) Over check/wing rail faces maximum 1355 mm (DSB) (30.11) Over check/wing rail faces maximum 1356 mm (UIC)

Wheel set standards: Flange width maximum *) 33 mm (UIC) (0.73 mm) Flange width minimum *) 22 mm (DSB) (0.49 mm) (outside flanges minimum also apply) Outside flanges maximum *) 1426 mm (UIC) (31.69 mm) Outside flanges minimum *) 1410 mm (wheel diameter 1000-840 mm, UIC) (31.33) Outside flanges minimum *) 1415 mm (wheel diameter 840-330 mm, UIC) Flange height minimum (wheel diameter 1000-760 mm, UIC) 28 mm (0,62) Flange height minimum (wheel diameter 760-330 mm, UIC) 32 mm (0.71) Flange height maximum (rolling stock, DSB) minimum +5 mm (+0.11) Wheel width nominal 135 mm (UIC) (3.00) Wheel width minimum new 134 mm (UIC) (2.98) Wheel width maximum new 136 mm (UIC) (3.02) Wheel width minimum 133 mm (UIC) (2.96) Wheel width minimum 130 mm (DSB circa 1920) (2.89) Wheel width maximum 140 mm (DSB circa 1920) (3.11) Back-to-back nominal 1360 mm (UIC) (30.22) Back-to-back minimum 1357 mm (wheel diameter 1000-840 mm, UIC) (30.16) Back-to-back maximum 1359 mm (wheel diameter 840-330 mm, UIC) Back-to-back maximum 1363 mm (UIC) (30.29) Check gauge nominal 1393 mm (UIC) (30.96) Check gauge maximum 1395 mm (DSB) (31.00)

*) measured 10 mm below running circle (0.22)

(snip)

Oh dear, Erik. Responding to Flynn with facts and figures is not a good idea. What will now follow is the familiar verbose and convoluted diatribe. He will forcibly repeat his mantra that:

"Exact scale wheel and track standards CANNOT work! Exact scale standards are NOT EXACT SCALE! Nobody can work to SUCH FINE TOLERANCES! See my web page for details of the ONE TRUE WAY!"

Good luck! :-)

Perhaps so. Luckily my models don't read this newsgroup so they don't know that they should not behave well.

Thank you ;-)

I discovered last night that I hadn't updated the drawings in the earlier article

I originally wrote it (in Danish) in 1981 and since then I have revised the standards a few times when I had more precise information on the prototype measurements.

I wrote a new article

with new drawings a few years ago but it is not yet translated into English.

The drawings are now updated.

Sorry about that, I should have known when Terry mentioned the rounded-off values.

Well, who'd have thought that Flynn could read Danish? Is there ANYTHING he cannot do?

He can't get Newton to apologize..........

Bloodywell right, he can't!

But as a matter of interest, what would I be apologising for?

I am sure he would think of something for you to apologize for. I know you have upset him and he has upset you.

The MRSG standards for Proto 64 published in 1970 are not exact scale. I assume your standard is different, and has not been around for 40 years.

The S7 standard clearly shows the prototype dimensions have not been simply scaled down. The designers of the standard have made it practical without major deviations from scale. You cannot have it both ways, you have either scaled down the prototype dimensions exactly or you make minor compromises so it becomes practical to do. I note the S7 standard on the web leaves out one important dimension, the minimum back to back wheel dimension. Unnecessary dimensions on the web page cloud the important dimensions to make complex track. The important S7 numbers are track gauge at the crossing V

33.08mm to 33.03mm and flangeway gap of 1.00mm to 1.05mm.

Working to track tolerances less than 0.3mm is impracticle for most hobbists. The larger the scale, the closer to exact scale you can go. Smaller standards deviate greater than the 7mm and S scale versions you quote. The 1970 MRSG P4 manual has an S acale standard which is not simply divide the prototype by 64. Minor compromises have been made to make it practical. I agree, Erik probably has the capability to model 1:45 exactly, but I doubt it is possible in smaller scales such 00 and H0 with common tools and methods. Other than saying it is possible, one should be saying is the extra precision required providing any visual or operational advantage. The answer is no.

Your dimensions below indicate different dimensions between each standard. Other prototypes vary as well.

The prototype clearance scaled down between the minimum wheel back to back and track and check face to check face (UIC scaled to P-45 is only 0.022mm). This is tight and will limit your models to scale curves only. I notice you are mixing 2 standards to broaden your tolerances slightly. It is correct to only use one or the other. By just using these scaled down prototype dimensions you are making life harder then necessary without any visual or operational gain. Wheel dimensions need very tight tolerances to comply with the prototype rules. The extremes cannot be simply used and scaled down. For example using UIC numbers, maximum flange width 33mm, check gauge minimum

1393mm, leaves a back to back maximum of 1360mm. Minimum back to back allowed is 1357mm. This leaves only 3mm total variation for back to back and flange width, that scales down to 0.067mm. If we machine flanges to a tolerance of 0.03mm that leaves a maximum back to back variation of 0.037mm. Not easy to do. That's why all the MRSG Proto scale standards are close but not exact prototype dimensions.

slightly. It is correct to only

I have only mentioned older DSB /Danish State Railways), newer DSB and/or UIC where there are differences. Where I mention only UIC values they agree with both older and newer DSB values. In general, I have based my Proto:45 on DSB 1930 or earlier.

Minimum wheel set back-to-back is 30.15 mm. Absolute maximum check rail face to wing rail face is 30.11 mm. This gives an absolute minimum clearence of 0.04 mm which is tight.

It is, however, very unlikely that check rail face to wing rail face should reach 30.11 mm. The probable maximum can be calculated:

Measurements are expressed as nominal values plus/minus a symmetrical tolerance. If total tolerance on the flangeways are 0.10 mm, we have:

Track gauge 31.965 +/-0.145 Check rail flangeway 0.96 +/-0.05 Crossing flangeway 1.14 +/-0.05

The nominal check rail face to wing rail face is 31.965 - 0,96 - 1.14 =

29.865 mm, and the probable symmetrical tolerance is SQR(0.145^2 + 0.05^2 + 0.05^2) = 0.161 mm.

Hence the probable maximum check rail face to wing rail face is 29.865 +

0,161 = 30.03 mm and the probable minimum clearence is 30.15 - 30.03 = 0.12 mm.

This is one reason that I have set 0.68 +/-0.03 mm for flange width so that the maximum is 0.71 mm, a bit narrower than the maximum prototype

33 mm (0.73). The absolute maximum check gauge is 30.29 + 0.71 = 31.00 mm.

The maximum check gauge for the wheel set (31.00 mm) may be a little larger than the minimum check gauge for the crossing/check rail (30.91 mm) in Proto:45 just like on the prototype.

I have thoroughly tested that this works in practice, and I feel that the reason is the much narrower flanges and check and wing rail flangeways in Proto:45. In a 1:7.5 point where the curve continues through the crossing and with the check rails removed, I could not derail a short-wheelbase wagon with standard wagon wheel sets neither in the straight nor the curved road.

NEM standards are not that forgiving, I can tell you.

This article can now be found in English at

It doesn't matter; Flynn will tell you it doesn't work in theory.

You can tell him until you're blue in the face, but if it isn't on his web page, it can't be correct.

:-)

Mark.