(Backwards this is srebmunehtgniod, which may mean something in a long dead language, but I doubt it.)
I've been looking at some numbers and measurements for track and wheels. From the NMRA web site comes the following measurements for different weights of rail in TT scale (in thousandths of an inch. I still can't understand why you would make the 1/2 arsed step of decimalising an imperial measure)
Rail weight height
40 pound 0.029
55 pound 0.034
70 pound 0.039
90 pound 0.047
110 pound 0.055
What this boils down to is that code 40 rail is roughly equivalent to 70 pound rail, and code 55 is equivalent to 110 pound.
I've also been taking a look at driving wheel diameters from the 2mm society.
wheel diameter real equivalent loco classes
7.5mm 3 F
8mm 3'2" W, Wa, Wb, Wd
9mm 3'6" B, Ba, Bb
9.5mm 3'9" Wf, X
10mm 4' Ww, Aa, Q, U, Ub, Uc
11mm 4'4" A, Ab, Wab, K, Ka, Kb, J, Ja, Jb
12mm 4'9" G
(This only counts steam loco classes that survived into the 1950's. A slightly narrower wheel is required for the 4'6" locos to fit into the correct 5' + 5' wheelbase).
From this we can see that its possible to 'accurately' model the wheels for all the steam loco's from the 50's and 60's. I'll follow his up in the next few posts.
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7 comments:
do you know how the spokes compare or are you looking at a table of sizes?
So if code 40 is equivlant to 70 lbs rail in TT, my question is what pound rail does NZR have in the given time frames, of steam era and modern era.
Roughly speaking - feel free to correct me if my dates are a bit wide of the mark - 40lb was the first rail laid on the NZGR, 52/55lb became the standard for new construction in about 1890, 70lb in 1905, 85lb in 1935. However, this was only for NEW construction, so the heavier rail took a while to appear over the system, only being laid on existing lines as they came due for renewal, and only then if it was deemed absolutely neccessary. I recall reading somewhere that even on the NIMT, the introduction of heavier locos such as the X was hampered for many years by the presence of 55lb and even 40lb rail on some of the older sections. A bit of almost useless info: General rule of thumb for axle loading is divide the rail weight in pounds by four to get maximum allowable axle load in tons; however, NZGR engineers took a more conservative approach and used a factor of five, hence 70lb/5 = 14 tons, the axle load of the K/Ka/Kb class, 55lb/5 = 11, axle load of J-class (give or take, it's actually nearly 12 tons)
whot about 90lbs + rail, whot date?
Soon after 85lb rail, I believe....
So what pound rail does NZR/Kiwirail use now adays.
The last time I saw mention of a standard, it was 50kg/m, which equates to 100.8lbs/yard. Not sure if any US standard 110lbs/yard has been used here.
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