NWNGR Cleminson coal wagon
Six-wheeled wagon with flexible wheelbase to James Cleminson's patent.
This wagon was drawn by the Metropolitan Railway Carriage & Wagon Co, in 1878, and so was probably built by them (but not necessarily, it seems that the original brake-composite carriages for the NWNGR, drawn by Brown Marshalls in 1872, are now believed to have been built by Ashbury in 1877). The drawing was redrawn by J. M. Lloyd and reproduced in Boyd and the wagon differed from the FR Cleminson wagon in that it had wooden underframe and sides. It was intended for coal traffic. Edouard Vignes published his book  in May 1878 where (after describing Cleminson's system and the NWNGR 6-wheel coaches) he wrote There are coal wagons similarly constructed; they weigh 2,800 kg and can carry 8,210 kg. He had visited the line and the FR the previous September before the coaches were delivered in December, so he would have relied on information from Cleminson for both, and nothing can be read into the implication that there was more than one (no photograph shows more than one), but the carrying capacity is of interest - 8,210 kg being 8 tons.
In Cleminson's patent the end wheelsets are mounted in trucks pivoted on vertical axes and the central wheels in a truck allowed to slide sideways according to the curvature of the track. Lateral displacement of the central axle caused linkages to steer the end axles so their wheels remained tangential to the track on a circular curve.
It can be seen in a photo taken at Rhyd-ddu (South Snowdon) in 1893-4 and discussed on the welshhighland Forum. It is clearly higher than the Large Coal wagons and almost twice as long. Part of it is also visible in a photo taken at the foot of Bryngwyn incline when it is next to Large Coal wagon NWNGR No 2, and it is higher than that. It also has six planks in the sides unlike the drawing which shows five.
There is a photograph of a demolition train at Glanrafon in 1941 showing a large flat wagon. This has a heavy wooden underframe, set low, with the running gear invisible behind. It is loaded with sleepers, known to be 4' long and 9" wide. They cannot be counted exactly but the approximate number gives about 17-18 ft long, which, allowing for gaps between them, is close to the 18'4" body length shown on the drawing. This could be the remains of the Cleminson minus sides and ends. In 1972 Boyd thought the wagon in this picture was a WD wagon, which it clearly is not. In 1989 he thought it was a bogie coach frame, but from the estimation above it appears too short for the 25' of the Ashbury brake-compos, the shortest of the coaches. One of these was indeed used as a timber flat (see WHR Carriages (Pre Preservation)), and could well be the long wagon in this shot - note the timber sideframes seem higher yet shallower than the wagon in the Glanrafon shot. The bogies are visible but the angle is too acute to estimate the length.
The remains of the Cleminson wagon did not survive the 1941 scrap drive. It is not known if any more than one were built.
- Boyd, James I.C. (1972). Narrow Gauge Railways in South Caernarvonshire. Lingfield, Surrey, England: The Oakwood Press. ISBN 9780853611158. OCLC 707587. 1972 edition, p212
- Vignes, Edouard (1986) . Technical study of the Festiniog Railway and some other narrow-gauge railways of England. Translation:D. Boreham. London: P.E. Waters & Assoc. ISBN 0948904038. OCLC 17354030.
- Keylock, J. The Welsh Highland Railway - An Historical Guide part 1 (WHR Heritage Group 2005, p10. This picture sometimes reproduced elsewhere but with the coal wagons cropped out.
- Boyd, James I.C. (1972). Narrow Gauge Railways in South Caernarvonshire. Lingfield, Surrey, England: The Oakwood Press. ISBN 9780853611158. OCLC 707587. 1972 edition, after p320, picture 31
- Boyd, James I.C. (1989). Narrow Gauge Railways in South Caernarvonshire, Vol. 2, The Welsh Highland Railway. Blandford: The Oakwood Press. ISBN 0-85361-383-4. after p102, picture 2