Flymo748 wrote:Nope, you're definitely not just talking to yourself
Keep it up - it's interesting to discuss these things amicably and understand more about the hobby that we have.
Cheers
Flymo
Thanks Paul. Yes, exactly what I am trying to do, with people's help, understand more about this hobby. I have learnt a lot from this Forum
Terry Bendall wrote:
There will probably be some track experts on here who can discuss this point but my copy of British Railways Track, fourth edition 1971, states "... all curves with a radius of 10 chains or less must be provided with a check rail, (fitted to the inside rail of the curve)." According to the book this was a Ministry of Transport requirement which also required that check rails were fitted to flatter curves if high speed is contemplated.
At the LBSC station at Midhurst, West Sussex, now long gone, there was a 10 chains radius curve on the line leading south to Chichester which had a check rail fitted all the way round the curve and a 20 mph speed limit imposed.
Just for interest, 10 chains equals 8 feet 8 inches in our terms. Do we run our trains at a maximum of 20mph round such a curve, and does it have a check rail?
Flymo748 wrote:but what size (length) do other members have in their toolbox?
I don't want to sound like Frankie Howerd, still less like my namesake Mr Clary (!), but this question is exactly the point of this thread, if the Mint gauge is used for anything other than straight track. Not to get personal Paul (Townsend), how long is yours, and do you use it just on straight track on "Highbridge"?
Terry Bendall wrote:"Roger Sander's 'Mint' gauge for fine tuning pointwork" which gives the name of the person who invented the gauge and its intended purpose. Some people may have used it to give gauge widening but that was not what it designed for.
Flymo748 wrote:The question was more "why are the current Mint gauges the size they are?".
Because that is the dimension stated on the drawing.
My mint gauge is a very early one, probably one that Roger had made and measures 34 mm long. The drawing used for the manufacture of the current ones gives a dimension of 40mm. I produced that drawing, and all the dimensions were taken from an actual gauge that Jeremy had in stock at the time - and that was in 2012. I have no idea why the length was changed.
The mint gauge was devised following an extensive period of checking the track on Pulborough, probably around 1990. When this was done it was found that there was a need for a gauge to check the parts that other gauges could not reach and in particular the area around the common crossing where it can be slid through the vee. It is also useful for checking the distance between the switch rail and the stock rail. The checking was necessary because running was not good enough so Roger and one of the other members of the group started at one end of the layout and literally checked every inch of the track and in 25 feet of scenic section that is quite a lot.
If you use the gauge for its intended purpose, then the overall length is not really relevant. The Mint gauges for 5ft 3 ins and broad gauge track are also 40mm long
Terry Bendall
I don't get all this. I understand that the gauge will be very useful to check the straight road of a turnout, though I don't see how it is so useful for the curving road, but you are saying it was used for every inch of the layout. Presumably "Pulborough" is not entirely made of straight lines? If not, then it sounds like the gauge is being used for curving lines, and in that case surely its length is not irrelevant, but fundamental, in which case, how can there be such question marks over how long it is meant to be?
Alan Turner wrote:
However if we take the prototype gauge widening of 10 - 7 chains = 1/4", 7 - 5.5 chains = 1/2" and less than 5.5 chains = 3/4" then the results for the length of mint gauge (set to the track gauge of 18.83mm) to produce these are:
10 chains, length of gauge required =24.35mm (1/4")
7 chains, length of gauge required =20.42mm (1/4")
7 chains, length of gauge required =28.88mm (1/2")
5.5 chains, length of gauge required =25.65mm (1/2")
5.5 chains, length of gauge required =31.41mm (3/4")
I absolutely am not qualified to make any mathematics correction to anyone. But I am not sure this can be correct. The thread opened with Russ Elliott saying that the Society Gauge Widening Tool gives half the widening the prototype might have done for a given radius. The gauge is a bit difficult to measure, in that the legs have a thickness, but the rectangular one which has the same function is 29.75mm long. My friend Chris calculated that prototypical widening of 3/4" at 5.5 chains or in our terms 0.25mm at 4 foot 9 inches, would be obtained with a length of 54mm, thus pretty much corroborating Russ' statement.
Will L wrote:In summary, re the Mint gauge, it seems to me....
Unlike the traditional 3 point gauge, the mint gauge was never intended to be used for creating/checking* gauge widening. So it has no relevance to this thread and its length was a distinct red herring.
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Well as you can see Will I don't quite understand whether the Mint gauge is being used beyond its original purpose. But might I suggest that if it is, and is being found to be useful in picking up faults that other gauges don't, it might be partly because it is longer than the Society gauge?
Which is where I came in, might not a 54mm gauge giving prototypical widening, though not used for curves below 4 foot 9ins, give better running? The 40mm gauge is nearly half way from P4 to prototype. In such a scenario, below 4 foot 9 a roller gauge set at +0.25 would emulate the prototype, with no further widening.
Earlier I said Tony suggested the P4 0.22mm maximum widening could have been a typo. But looking again at the Digest, the 0.22 is plainly written several times, for the three gauges (standard, Irish and Broad).
Looking at the "chronology of P4" on
http://www.clag.org.uk/protofour-chronology.html I see that the first triangular gauge was devised by Brook Smith in 1956 and is thus fundamental to our hobby, and my questions are not meant to rock this boat unless my question, whether running could be improved with prototypical widening, was found to be answered in the affirmative.