Galagars

I thought that I would take a closer look at “Sir Gilbert Claughton”, the Metropolitan Junction loco based on a Jidenco kit, to get a better idea of how much of the kit had been used. Most of the loco body does appear to be from the kit, the identifiably scratch built items being the valences, the footsteps and firebox front and back. There is evidence of cutting away of a large area of the footplate and part of the boiler barrel in order to obtain clearance for the driving wheels and Portescap motor. The chassis appears to have etched main frames but is otherwise scratch built, including new coupling rods provided following an incidence of a broken rod at expoEM! The tender has a scratch built sub frame. In short, the claim of “80% scratch built” appears to be somewhat exaggerated. On the subject of “OO” trac k standards, surely increasing the check rail flangeway to 1.5 mm cannot be right? This would reduce the check gauge. What would happen at an obtuse crossing where the flangeways have to be symmetric?

D. A. Williams, the builder of Metropolitan Junction, described the Claughton as “80% scratch built”. Amongst other faults, the slots in the valences were not at the same centres as the axles. Galagars

A little arithmetic on the dimensions supplied by Graham Muz confirms that the dimension of 19 ft 7 1/2 in is the length of the body side and not the rave. The kit is therefore accurate if the body is assembled end over side. If the dimension had been the length of the rave the error would have been over 2 mm. hence my concern.

I am interested in Brightspark's comments about the length of the tender body. I have a Crownline kit for the 4500 gal tender which I have not assembled because the body sides appeared to be too short. They measure just over 78 mm. The tender rear is slightly wider than the front bulkhead and it appears from the locating slots in the floor that it is intended to fit end over side. This seems to me to be a strange form of construction. I got as far as preparing an inner rear bulkhead to assist with assembly before putting the kit to one side. Fitting the end over the side would bring the length up to about 78.5 mm, but I was not satisfied that this was correct. The best drawings I have are those published in Modellers' Back Track Vol. 1 No.1 As drawn, the length of the body side is 79 mm. The diagrams in Southern Locomotives by J. H. Russell are in agreement. The rave is a little over 2 mm less. Scaling from a side on photograph (a dangerous thing to do!) of 21C125 being coaled at Wadebridge in1948 indicates a length of body side of about 19 ft 10in. Does any RM Webber have a copy of the general arrangement drawing for these tenders to confirm what the 19ft 7 1/2in dimension refers to? If I knew the answer I might be prompted to assemble the kit!

I posted some details of my experience of operating “Presson” on the expoEM Spring 2022 thread. This was at an exhibition organised by the Leicester Model Railway Group in about 1970 after the layout had passed to a new owner. Apart from a set of PC Models LNWR coaches which would have had finer profile wheels, the locos and stock were fitted with the “OO” profile wheels generally available at the time, i.e: Romford, K’s, Jackson and possibly Hamblings. I contributed a pair of scratch built LSWR coaches and some vans fitted with Nucro or Jackson wheels. As I remember the layout performed reliably notwithstanding the varied wheel profiles. One of the locomotives in use was a Tri-ang 3F 0-6-0 with a scratch built Midland pattern tender. It was fitted with Romford driving wheels. I have just checked some vintage Romford 21 mm driving wheels and find that the flanges are about 0.6 mm thick. “Presson” did not have sharp curves and most of the curves on the layout were the diverging roads of turnouts. I have speculated that there may have been a small amount of gauge widening in the curved roads of the turnouts. If the width of flangeway was maintained at 1 mm, the check gauge may have been increased sufficiently to allow smooth passage of the Romford flanges. Alternatively, there may have been sufficient taper on the flange faces to allow guidance. I think that it should be emphasised that 18.0 mm gauge with 0.8 mm flangeways requires a very accurate standard of pointwork construction. With 16.5 mm back-to-back the running clearance over check rails is only 0.1 mm. The scaled down prototype clearance is about 0.2 mm! Galagars

I have had some further thoughts concerning my experience of operating “Presson” half a century ago. One of the locomotives in use at the Leicester exhibition was a Tri-ang 3F 0-6-0 with a scratch built Midland pattern tender. It was fitted with Romford driving wheels. My early experience with a scratch built six-coupled chassis fitted with Romford wheels was that it would not enter an 18.0 mm gauge 3-foot radius curve without derailing. “Presson” did not have such sharp curves and most of the curves on the layout were the diverging roads in turnouts. I think that there must have been a small increase in check gauge, allowing the thicker Romford flanges to pass smoothly and I wonder if this was done by constructing the turnouts with a small amount of gauge widening, perhaps 0.1 – 0.2 mm, while maintaining the width of flangeway at 1 mm? The above is speculation on my part, but based on the observed successful operation of the layout with a variety of stock, much of which had not run on the layout prior to the exhibition. Galagars

I was the individual who recalled his experience of operating “Presson”, during a break from my stewarding duties. The layout had been sold and renamed “Dunmoor” as I remember. It was shown at an exhibition organised by the Leicester Model Railway Group in about 1970. I do not recall the flangeways being any different to the BRMSB 1951 standard usual at that time, and certainly wider than those on T-B-G’s demo. A considerable variety of stock was used, including some of my own early efforts, fitted with the wheels available at the time, i.e: Romford, K’s and Jackson. I remember a set of PC Models LNWR coaches. PC Models wheels were to a finer profile and may have been the only wheels in use that bore any resemblance to the “Manchester” profile. I recall that the layout performed well notwithstanding the different wheel profiles. The fiddle yard consisted of a motorised sector plate with a turntable at the end. This was prone to jamming if allowed to overrun. As the youngest and most agile member of the team it fell to me to crawl underneath to free the mechanism by winding it back by hand. It is perhaps fortunate that my more recent experiences have been with layouts which lack such advanced technology! I have acquired two GWR “Toplight” coaches. These are of wood construction and have fine profile brass wheels with a 2 mm wide tyre. These are not reprofiled “Nucro” or “Jackson” wheels. I suspect that they are the almost legendary “Zenith” coach wheels, the only wheels commercially available to the original “EMF” standard. I should have remembered to bring these coaches to expo in order to try them out on T-B-G’s demo. I did make a few purchases at expoEM, including a “King Arthur” class nameplate from the Members' Sales. Galagars

I think that the real bone of contention here is about the claim that OO-SF will accept ready-to-run models. I mentioned Hornby coaches up thread with a back-to-back of 14.25 - 14.3 mm. The distance over check rails in OO-SF is 14.2 mm which allows a running clearance of only 0.05 – 0.1 mm. The prototype clearance scales to about 0.2 mm! Much OO RTR has thick flanges which are tight in a 1 mm flangeway. OO-SF can undoubtedly be made to work, but requires much more precise setting of the back-to-back measurement than RTR manufacturers seem capable of and some (many?) RTR wheels may not be suitable. It is necessary to allow tolerances in the setting dimensions which does not appear to be the case in the OO-SF dimensions. Also, the OO-SF check gauge is marginally less than the DOGA Intermediate minimum. If we assume that the 0.05 mm tolerance of the 18.83 mm gauge standard is the best that is reliably achievable, we have a check gauge of 15.25 – 15.3 mm. A 1 mm flangeway has to be the absolute minimum and we need some tolerance here, another 0.05 mm. The minimum track gauge is then 15.3 mm plus 1.05 mm which equals 16.35 mm. If we decide that a tolerance of 0.05 mm is too tight to be achievable by ordinary mortals and go for 0.1 mm, the track gauge has to increase to 16.45 mm, almost back to standard OO. And this does not include an allowance for manufacturing tolerances in the track construction and back-to-back gauges! Galagars

Peter Denny did not introduce gauge widening by accident. His article: “Permanent Way on the Buckingham Branch Line”, which appeared in the Ocyober 1950 issue of the Model Railway Consytuctor includes the following: “I planed my own up from two pieces of stripwood 1ft. 6 in. x ¾ in. square, cutting slits in the “curved” section 1 in. apart so that it can be bent to any radius. … This type of gauge has the advantage of automatically increasing the gauge on curves from 18 mm. to 18.5 mm.” However, the increase was not quite as intended as Tony Gee stated that he found the gauge to vary by quite a bit more than 0.5 mm! I am presently converting some Hornby coaches to EM, using the original wheels. Some were recently purchased new and others – low window Maunsells – are older. It occurred to me to check the back-to-back measurements before adjusting the wheelsets. I found the measurements were quite consistent at 14.25 – 14.3mm. This is less than the DOGA standard, but would seem to be satisfactory on Peco points with 1.39mm flangeways, although smoother running with less wheel drop at the frogs could be obtained with a slightly wider back-to-back. Why does The Johnster feel it is necessary to reduce the back-to-back to 14.1mm? Am I missing something? Or is it that my experience of EM simply does not transfer to OO gauge? A back-to-back of 14.1mm risks jamming on check rails to DOGA intermediate standards if the check gauge approaches the upper limit. Galagars

I would like to add a few comments regarding the early history of EM gauge and BRMSB standards. Ravenser suggests that A "compromise gauge" of 18mm was the pet idea of Mr Chubb, but it was actually proposed some years earlier and was taken up by at least one modeller. In its May 1926 issue, the Model Railway News published a Paper which had been read before the Manchester and District Model Railway Club by Theodore Horn, M. A., entitled “Scales and Standards in the Smaller Gauges”. The author expressed surprise that no one had objected to the use of an under scale gauge for 4mm scale and suggested a gauge of 18mm. This pre-dated the well-known proposal for the slightly over scale gauge of 19mm which appeared in the July 1926 issue. Stan Garlick, better known in later years for his “S” gauge models, built three 18mm gauge model locomotives during the 1930’s: a 3F 0-6-0, a 2-6-2T and a Stanier 2-6-0. . Mr Chubb’s contribution was contained in an article entitled “Scales and Gauges”, which appeared in the July 1936 issue of the Model Railway Constructor. This followed the formation of the British Model Railway Standards Bureau (not to be confused with the 1941 organisation) by the MRC in April, which proposed fine scale standards for 16.5mm and 19mm gauges. Mr Chubb noted that increased clearance was necessary to allow for the swing of bogies on coaches and outside cylindered locomotives on sharper-than-scale curves, and recommended 18mm gauge using similar standards. Back-to-back was to be 16.5mm and wheel width 2.25mm, almost identical to the current EM standard. By WWII, 18mm gauge was becoming established. Some exhibition reports published in the Model Railway News include descriptions of 18mm (and 19mm) gauge models on static display. In the February 1937 issue of the MRN, S F Sewell placed an advertisement entitled: “Pointwork to Measure”. It was for “OO” pointwork, and included the statement: “The above can be had in 19 mm or 18 mm Gauge at a Slight Extra Cost.” The City Model Company had 18mm gauge track on display at the 1939 Model Railway Club exhibition. In the June 1939 issue of MRN, Multi-Models Ltd advertised 4mm scale Southern Railway bogie and 4-wheel utility vans. These were available ready-to-run for 16.5, 18 or 19mm gauge tracks. Unfortunately the BRMSB failed to work out the required construction and setting tolerances correctly, which created a conflict between the wheel and track dimensions. This was tolerable in “OO” where clearances were more generous but led to a situation where 18.0mm gauge was virtually unworkable with commercially available wheels. The BRMSB also failed to specify gauge widening on curves. Peter Denny had advocated 0.5mm gauge widening on curves in his 1950 article in the MRC on track building. When I built my first six-coupled chassis I was unaware of Peter Denny’s article with the result that my chassis refused to enter a curve without derailing. The EMGS later resolved the situation by increasing the track gauge to 18.2mm and the check gauge to 17.2mm, but failed to specify tolerances. In practice, the dimensions allow a tolerance of 0.1mm, i.e. the check gauge can be up to 17.3mm without brisk of wheelsets binding on check rails. DOGA has resolved a similar, but less critical, situation in “OO” by adding a plus tolerance of 0.1mm to the BRMSB nominal check gauge of 15.25mm in its intermediate standard. I find it curious that DOGA ignores the BRMSB wheel standard which is well suited to the intermediate track standard and not entirely obsolete. The Hornby Maunsell coach wheel is closer to the BRMSB profile than the wheels available back in the day, or would be if quality control of the back-to-back measurement was better! Galagars