EM Gauge Block Gauge with Crossing Alingment Aid

paratom

Western Thunderer
I have just received an order of track components from The EM Gauge Society and hoping to start building points and track for my layout. Amongst the items I ordered was an EM gauge block by D.D.Wheelwrights which I tested on a short length of Ratio EM gauge track and to my surprise it did not want to sit between the rails. I thought maybe the track was slightly out of gauge so I measured the block gauge with my digital vernier gauge and found it to be 18.26 mm. I know it is only 0.06 mm out but is this regarded as acceptable or should it be exactly 18.2mm for it to be of any use. The DCC Concepts EM gauge track gauges that I also ordered fit on the Ratio track perfectly and are 18.2mm as measured with my vernier gauge. Have any modellers out there encountered the same problem with these gauges?

DD-Wheelwrights-EM-Block-gauge.jpg
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AJC

Western Thunderer
Have you taken a Vernier to the Ratio track bases? It's not clear from your original post. They're known to be slightly under gauge (the sample I have to hand comes out at 17.95/6), but work perfectly well, though I can see that it might cause problems with more accurate gauges.

Adam

EDIT: Chris Pendlenton reported that the P4 Ratio bases were also slightly under gauge in an early MRJ as I recall - Yeovil MRG used some of the P4 track to give gauge widening on curves, nearly 40 years ago now. Still going and works well.
 
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Martin Shaw

Western Thunderer
If you asked me to make something exactly 18.2mm in width, I would have to ask what tolerance is allowable as exactly is difficult, expensive, and often as not, not necessary. I would hope that even with my basic machine tools and limited skillset I could get within 0.02mm or 1 thou ish as a one off, repeatability probably less consistent if hand operated. I think on the next wet day a bit of time on an exercise might be illuminating. I would have thought that a track gauge would be better to be a tad over size rather than under in any case.
Regards
Martin
 

AJC

Western Thunderer
Presumably the EMGS publish standards?

Indeed they do, supplied as part of the Manual. What @paratom hasn't confirmed is the gauge of the Ratio track he cites. I strongly suspect that his sample, as mine, is under gauge. 0.06 of a mm will make no difference to running in EM, I'm absolutely certain of this as EM stock runs perfectly happily on P4 (plain) track and the Ratio track I have which is 0.25mm under spec'. The gauge is certainly within tolerance as described.

Equally, it would be interesting to know what the tolerances are of the other gauges he describes.

Adam
 

Martin Shaw

Western Thunderer
Well it wasn't wet today but a loose end allowed me some time in the workshop where the task was to machine a cube 18.2mm.
IMG_1131.JPG
This is the result which by vernier measures 18.2mm in all three planes. A more accurate measurement with a micrometer suggests tolerances of between 18.19 and 18.22, I can't measure more accurately than that and the number varies by about 0.01 depending where on the cube the measurement is taken which may well be down to the tramming of the mill and the order of the sides I did the machining in. So I conclude that it is entirely possible to make something that is as near an exact size as is practical but it isn't a way to make any money and a small tolerance error won't have any adverse impact on how the trains run.

BTW if this is of any use to our EM friends drop me a PM with your address and I will post it to you, gratis. Otherwise the scrap bin beckons.
Regards
Martin
 

paratom

Western Thunderer
Even the most accurately machined block will alter in size depending on the room temperature but who has a micrometer that can measure those differences.
 

simond

Western Thunderer
Even the most accurately machined block will alter in size depending on the room temperature but who has a micrometer that can measure those differences.

so will the micrometer, which poses some challenges.

Any self-respecting inspection room is temperature controlled for precisely that reason!
 

Martin Shaw

Western Thunderer
All I can say is that the block and the micrometer/vernier had been in the same room all afternoon and therefore temperature derived variations would have affected everything, or nothing! As it is if you need anything to a tighter tolerance than half a thou in connection with anything railway based, model or full size, then it's grossly over engineered and therefore more expensive than it need be.
I could if I was at all interested find out the coefficient of expansion of the particular aluminium alloy I used and calculate the dimensional alteration for any given temperature change, bloody small I expect.
Regards
Martin
 
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