DHR class D
| DHR class D | |
|---|---|
 Factory photo of the DHR class D No. 31 on a test track at the Beyer-Peacock factory.
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| Numbering: | 31 |
| Number: | 1 |
| Manufacturer: | Beyer-Peacock |
| Year of construction (s): | 1910 |
| Retirement: | 1954 |
| Type : | B'B 'n4 (Garratt) |
| Gauge : | 610 mm |
| Service mass: | 28.4 t |
| Friction mass: | 28.4 t |
| Wheel set mass : | 7.5 t |
| Driving wheel diameter: | 660 mm |
| Control type : | Heusinger |
| Cylinder diameter: | 280 mm |
| Piston stroke: | 355 mm |
| Boiler overpressure: | 110 N / cm² |
| Grate area: | 1.63 m² |
| Radiant heating surface: | 5.95 m² |
| Tubular heating surface: | 56.02 m² |
| Train brake: | no |
The locomotive of the class D of Darjeeling Himalayan Railway (DHR) was the world's third Garratt -Dampflokomotive and the first with the normal arrangement of the cylinders at the outer ends of the motor bogies. It was in service from 1911 to 1954.
history
Up to the procurement of class D, the DHR only used two-axle tank locomotives , in 1910 mainly class B locomotives , as they are still used today.
In that year Beyer-Peacock delivered a Garratt locomotive , the engine dimensions and drive wheel diameter of which corresponded to those of class B, which theoretically gave about twice the pulling power. The locomotive was given the class designation D and the road number 31.
After eliminating some teething troubles, the locomotive proved itself to the extent that it could meet the expectations of the train performance; however, it turned out that the long trains that were now possible derailed more easily in tight turns. In addition, some sidings and butt tracks at the switchbacks were too short for these trains and should have been lengthened at great expense. Some of the clutches were too weak and should have been replaced.
This never happened, and no further Garratt locomotives were ordered, although Beyer-Peacock had offered a second locomotive at a lower price. Instead, the DHR procured additional class B locomotives. Nevertheless, the Garratt remained in service as a single unit until 1954, mainly on the flatter branch line to Kishanganj , where the problems mentioned did not play a role.
The locomotive was scrapped in 1954 after this branch line was closed and replaced by a meter-gauge line.
technology
In 1909 Beyer-Peacock delivered the very first Garratt locomotives to the Tasmanian Government Railways ( TGR class K ). These machines had the cylinders on the inside of the bogies and were also constructed according to the compound principle . The locomotive built for the DHR, on the other hand, was the first "normal" Garratt, with four single expansion cylinders that were arranged at the outer ends of the bogies. From then on, this design was retained almost without exception.
The arrangement of the reversing in the form of a cardan shaft running alongside the right locomotive was unusual , a design that Beyer-Peacock did not repeat. The additional water tank attached under the boiler was also rarely found on later Garratt locomotives.
Like the class B, the Garratt motor bogies had external frames and external cylinders with Heusinger controls , but the cylinders were arranged horizontally. The driver's cab was open except for two draft shields; the rear one was later removed and the roof extended to the rear.
Because of the tight counter-curves of the DHR, the locomotive was built in such a way that the motor bogies could twist against each other without causing tension (see illustration).
literature
- AE Durrant: Garratt locomotives of the world . Birkhäuser Verlag ISBN 3-7643-1481-8
- Terry Martin: The Iron Sherpa - The Story of the Darjeeling Himalayan Railway, Volume 1 , ISBN 978-1-900622-10-3