In 1904 Mr. Ivatt began to turn his attention to the provision of rail motor coaches suitable for local traffic, and designed some steam coaches which were built at Doncaster and elsewhere. Before these were completed, however, he made experiments with a petrol motor coach, which began work by making a series of trial trips between Hatfield and Hertford. Two other petrol coaches, Nos. 3 and 4, built by Messrs. Kerr, Stuart & Co., Ltd., worked the service until early in 1909, when they were withdrawn.
Early in 1905 orders were booked with the Avonside Engine Co., Ltd., and Messrs. Kitson & Co., Ltd., for two steam rail motor coaches from each firm. In the meantime Mr. Ivatt put two in order at the Doncaster works, as follows:
| Date. | Doncaster No. | Rail Motor No. |
|---|---|---|
| 1905 | 1107 | No. 2 |
| .. | 1108 | No. 1 |
The design of these coaches consisted in making the locomotive and carriage body detachable, thus rendering it easy to withdraw either part for repairs, so that should the engine of one complete coach, and the body of another, be laid aside at one time, the other sections might be utilised together during the interval.
The engine bogie was therefore made complete in itself as a small four-wheeled locomotive with a loco-type boiler 4-ft. 0 1/2-in. in diameter, containing 178 tubes, and working at a pressure of 175 lb. per sq. in.; the firebox measures 3-ft. 6-in. long by 4-ft. 0 1/2-in. wide. The total heating surface is 382 sq. ft., and the grate area 91 sq. ft. The cylinders are placed outside the bogie frames, and are 10-in. in diameter by 16-in. stroke, actuated by Walschaerts valve gear, and the coupled driving wheels are 3-ft. 8-in. in diameter.
The car body is 49-ft. long, and is carried at the other end on a standard G.N.R. four-wheeled carriage bogie. It is divided into a luggage compartment next to the engine, third-class smoking and non-smoking compartments, a first-class saloon (the total seating accommodation being for 53 passengers), and a guard’s compartment, which is fitted with duplicate controlling gear so that the car can be operated from that end when running carriage first.
Some of these engines were first put to work on the Louth-Grimsby section of the G.N.R., a section of 14 miles in all with four intermediate stations, to which were added six additional “halts,” at Fotherby, Utterby, Grainsby, Holton Village, Weelsby Road and Hainton Street. Others were intended for the local services between Finchley and Edgware, Hatfield and Hertford, Hatfield and St. Albans, Hitchin and Baldock, etc.
The coaches built by outside makers differed in some details from those built by the Railway Company itself. Thus, Nos. 5 and 6, the locomotive bogies of which were built by Messrs. Kitson & Co., Ltd., and the carriage bodies by the Birmingham Carriage & Wagon Co., Ltd., had the following leading dimensions: Cylinders, 10-in. by 16-in.; heating surface of boiler, 505.64 sq. ft.; working pressure, 200 lb. per sq. in.; diameter of coupled wheels, 3-ft. 7-in.; length over buffers, 66-ft. 5 1/8-in.; extreme width overstep boards, 8-ft. 101-in.; extreme height, 12-ft. 6-in.; seating accommodation for 57 passengers; total weight, 40 tons 2 cwt.
Nos. 7 and 8, built by the Avonside Engine Co., Ltd., have the following leading particulars: Cylinders, 10-in. by 16-in.; diameter of coupled wheels, 3-ft. 8-in., with 3-in. by 5 1/2-in. tyres; wheel-base of engine bogie, 8-ft.; heating surface: firebox 6o sq. ft., tubes 330 sq. ft., total 390 sq. ft.; grate area, 10.3 sq. ft.; working pressure, 200 lb. per sq. in.; total wheel-base of coach, 53-ft. 9-in.; total length over buffers, 66-ft. 1 5/8-in.; extreme width over carriage body, 8-ft. 6-in.; accommodation for 10 first-class and 40 third-class passengers; total weight, 40 tons 9 ¾ cwt. The water tanks are placed below the carriage body, and contain 650 gallons of water.
These coaches are fitted with the automatic vacuum brake, having two 18-in. cylinders. The tractive effort with a 7o % cut-off is 5,500 lb., and a motor of this type and power is capable of taking a trailer car as well up gradients of 1 in 40, and of averaging a speed of 20 miles per hour up gradients of 1 in 50.
