Haarmann's twin and triple splint
The Haarmann'sche double and triple track was one of August Haarmann in Osnabrück steelworks developed superstructure system for horses - trams , which was used from 1880 to 1910.
Twin splint
In Haarmann's twin rail system, two rails, usually 9 m long, with a symmetrical profile were used, which were held together by means of flux -iron or cast-iron spacers , which were usually 50 to 60 cm apart, and screw bolts. The intermediate pieces transferred the pressure of the wheels to the feet of both rails. The joints were offset from one another by 50 to 60 cm and had a larger intermediate piece that acted as a bracket, while the rail was also secured by strong outer brackets. Instead of using an intermediate piece, four smaller ones with two bolts each could be used. Eight link bolts, each 15 mm in diameter, created the connection, in which the counter rail was viewed as a continuous second link.
The height and shape of the rails were designed differently, often a height of 130 mm was chosen, while the width of the head was 42 mm and that of the foot 70 mm and the web was 5 mm thick. The cross connection was formed by upright flat iron 45 mm high and 8 mm thick, which were 90 mm high and 10 mm thick at the ends and bent at an angle so that it could be fastened with screw bolts through the webs. The groove between the two rail heads was 30 mm wide and 32 mm deep, the lower part of the space was filled with sand and was given a top layer of cement or bitumen . The cavities between the bridges and paving stones were filled with matching shaped clinker bricks that were glued to the rail with asphalt pitch. The joint between clinker and stone was also filled with cement or bitumen. In this way, a rectangular cross-sectional shape could be made from the rails and clinker bricks, which adjoined every type of paving excellently.
In Berlin , by order of the municipal civil engineering administration, the cube pavement had to be fully connected so that the total foot width was only 120 mm, a dimension that would otherwise have been better chosen a little larger. The rails initially installed were 130 mm high, the difference in height compared to the neighboring paving stones was compensated for by clinkering, which was later omitted. The splints were produced with a height of 155 mm and a web thickness of 5.5 mm, the head width remained 45 mm.
Attempts carried out in Berlin and Posen to use the advantages of Haarmann's construction by driving on with symmetrical bandage, i.e. to have both rails as running surfaces, which enabled the carriages to roll more evenly without hitting the rail joint, failed because of the greater frictional resistance, which resulted in a significantly higher demand for animal traction. To protect the horses, the one-sided bandage had to be used again.
Triple splint
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The use of triple rails prevented the horse's hooves from getting stuck in the groove. In the case of Haarmann's twin rails with relatively small head walls, on the other hand, in cities where horses often had badly designed horseshoes for walking on the rails, the horse's hooves occasionally got stuck in the groove of the rails. This was later avoided by the higher inner walls of the rail heads.
Since one-piece rail systems with too weak a joint often had an unfavorable influence on the pavement and thus hindered vehicle traffic, the Association of German Contractors, in a statement addressed to the Reichstag , emphatically advocated the so-called triple rails . With the one-piece and two-piece sleeper rails with guard rails, the height of the rail head ensured that accidents caused by jamming of the horse's hooves could not occur.
Some tram administrations preferred to give the guardrail a head shape that closed the groove at the bottom. In other places, interchangeable web rails with guard rails were used. If the downward metal closure of the groove was dispensed with, the cavity between the running rail and guardrail was filled with cement or bitumen after laying, which led to increased positional stability of the rails.
Due to the unusually heavy traffic on the Berlin horse-drawn railway tracks, the rail joint connection of the twin rails was heavily used. The 330 mm long bracket on the running rail was not robust enough because the long bracket bolt was insufficiently strong.
The impact that the second rail in the direction of travel received when the wheel passed the gap had a damaging effect on the butt plate and the intermediate pieces, so that these were knocked out more and more.
The thin 5.0 to 5.5 mm thick rail web was often too weak and cracked when the bracket screws were tightened sharply. However, these cracks were difficult to detect through the covering flap and their presence was only noticed through the impacts during operation. Since exchanging the intermediate pieces required the rails to be clamped on over a length of 2 to 3 m, a change in the butt joint was introduced: The running rail was then given two tabs and the protective rail one tab. The two inner tabs were pressed firmly onto the rail by wedges to be driven in from above. The plates were replaced by removing the wedges, whereby the road paving was only required in the area of the length of the plate.
Individual evidence
- ↑ a b c d e f g h Friedrich Müller: Basic features of the small railway system. 1895. p. 265.
- ↑ Max Buchwald: The sleeper rail superstructure. In: The superstructure of the trams and small railways. Wiesbaden, 1903. p. 56.
- ↑ a b c d August Haarmann : The small railways. 1896.