The Thompson Q1 0-8-0T Locomotives

Withdrawal of the Q4 goods locomotives started in 1934, but was delayed by a wartime shortage of goods locomotives. Between 1942 and 1945, Thompson would rebuild thirteen of these Q4s as tank engines for use as heavy shunters. The rebuilds were given the classification of Q1, which had been made vacant by the withdrawal of the last Ivatt Q1 in 1934.

Initially, Thompson's standardisation plans did not include an 0-8-0T class, but by late 1941 plans were drawn up for an 0-8-0T to replace an order for new J50 0-6-0T shunters. This 0-8-0T was based on a rebuild of the Q4, and rebuilding started almost immediately. The frames, cylinders, and connecting rods were kept. The boiler was shortened to provide space for an fully enclosed cab and the bunker. With the firebox further forward, the valve gear eccentrics had to be moved forward from the third axle to the second axle. Building had already started on some of the parts for the cancelled J50s. Some of these parts were incorporated into the side tanks, cabs, and bunkers of the first Q1s. Usually the weight was distributed so that it was highest on the main driving axles, but the first four Q1s were unusual in that the weight was mainly on the two front axles (19tons maximum axle load).

The first four engines entered service between June 1942 and March 1943. At a very early stage, there were complaints about the very small water capacity. Hence, the later engines had a longer bunker and were designated Q1/2 whilst the original four were designated Q1/1. The Q1/2s had their frames extended by 6 inches to enable the larger bunkers. The coal capacity of the new bunkers was reduced by half a ton. The end result was an increase in water capacity of 500 gallons. The larger bunkers also influenced the weight distribution. Unlike the Q1/1s, the maximum axle load was on the rear two axles. Nine locomotives were built to the Q1/2 specification.

Although many of the original Q4s had superheaters, these were removed during rebuilding. Steam brakes were fitted as standard, with a gradable steam brake fitted to all members of the class between 1947 and 1948.

The new Q1s were tried in a number of places requiring heavy shunting work. They were more powerful than the J50s, but not as powerful as the S1 and T1 heavy shunters. Most were distributed in the Southern Area, although a couple worked in the North Eastern Area and a couple worked in the Scottish Area.

The Q1s were considered to have roughly equal power abilities as the O4s but were seriously restricted by their lack of water capacity. Although the Q1s showed mixed results at most of the yards where they worked, they were used very successfully at Frodingham. Most of the traffic in the area serviced Scunthorpe's steel mills, and a typical 0-6-0T shunter was far from adequate at shunting these heavy loads. A Q1 could handle them very well, and there were plenty of opportunities to refill the limited water tank.

Withdrawals started in 1954 and were completed by 1959.

Technical Details

Locomotive Nos. 9925-9928 (BR Nos. 69925-69929) were built as Q1/1. The remaining locomotives (Nos. 9929-9937, BR Nos. 69929-69937) were built as Q1/2.

		Q1/1	Q1/2
Cylinders (x2):		19x26in.	19x26in.
Motion:		Stephenson	Stephenson
Boiler:	Max. Diameter:	4ft 9in	4ft 9in
	Pressure:	180psi	180psi
	Diagram No.:	17A	17A
Heating Surface:	Total:	1209 sq.ft.	1209 sq.ft.
	Firebox:	141 sq.ft.	141 sq.ft.
	Tubes:	1068 sq.ft. (228x 1.75in)	1068 sq.ft. (228x 1.75in)
Grate Area:		23.62 sq.ft.	23.62 sq.ft.
Wheels	Coupled:	4ft 8in	4ft 8in
Tractive Effort:	(@ 85% boiler pressure)	25,644lb	25,644lb
Total Wheelbase:		17ft 1in	17ft 1in
Engine Weight:	(full)	69 tons 18cwt	73 tons 15cwt
Max. Axle Load:		19 tons	19 tons 15cwt
Water capacity:		1500 gallons	2000 gallons
Coal capacity:		4 tons 10cwt	4 tons

Preservation

None of the Thompson Q1s survived into preservation.

Models

A 4mm scale kit of the Thompson Q1 is available from Millholme.

Gladiator produce a 7mm scale (O gauge) kit of the Thompson Q1.

Acknowledgements

Thank you to the P.H. Groom collection for permission to use the above photograph of Q1/2 BR No. 69931.