Trapeze fork
The trapezoidal fork or Parallelogrammgabel or Druid fork (engl. Girder fork), is a type of front wheel suspension for motorcycles . The trapeze fork had been the standard design on motorcycles for two decades from the 1920s until the telescopic fork became popular .
history
On December 30, 1907, Axel Levedahl patented a trapezoidal fork from Aurora Automatic Machinery Company, which was then installed in Thor's single-cylinder model . The Peugeot 500 Sport from 1913 had a trapeze fork based on what was later called the "Druid" system, for which Arthur Drew applied for a patent on August 31, 1914. Posthumously the patent for Drew was registered in 1917, the trapeze fork was named Druid fork . After the First World War , the trapeze fork was offered by many manufacturers in different versions, including:
- Brampton fork (also Biflex fork)
- Druid fork
- Girdraulic fork (with hydraulically damped springs, including Vincent , Rudge )
- Tiger fork (made by Allright in Cologne)
- Webb fork ( e.g. at Velocette , Rudge , Moto Guzzi , Norton )
One-armed parallelogram fork on an Imme from 1949
Parallelogram fork on an NSU Kettenkrad HK 101 from 1943
Trapeze fork with a compression spring (NSU)
Webb fork (Triumph)
Girdraulic-Gabel (Vincent) 1949
After the Second World War , hardly any motorcycles with parallelogram forks were built. The telescopic fork completely replaced the trapezoidal fork in the early 1950s. The last motorcycle to be redesigned in Germany with a so-called “one-armed parallelogram fork” was the innovative Imme by Norbert Riedel , which came onto the market in 1949. Other manufacturers began post-war production initially with almost unchanged pre-war models that were still equipped with trapeze forks. Examples of this were the DKW RT 125 W and the NSU 251 OSL.
technology
The wheel is encompassed by a rigid wheel carrier, which is attached to two to four rotatably mounted struts near the steering head and is supported against one or two coil springs . The struts form a trapezoid or a parallelogram with the wheel carrier and the steering head in a side view . In the case of the parallelogram fork - which is the exception - the pairs of joints are of the same length, in the case of the trapezoidal fork they are of different lengths and therefore have a different lever path. The wheelbase is reduced during the compression process of the trapezoidal fork . The advantage of the trapezoidal fork compared to earlier designs was the greater rigidity of the closed combination of wheel axle and wheel carrier, as well as the brake buckling compensation with a corresponding arrangement of the struts. The disadvantage of the trapezoidal fork - compared to the short swing arm - was the higher moment of inertia around the steering axis and the sensitivity to maintenance.
In accordance with the state of the art at the time, mechanical friction dampers were used as vibration dampers , the effect of which was insufficient due to the principle involved. In rare cases, trapezoidal forks had hydraulic shock absorbers , including the NSU - Kettenkrad and the Girdraulic fork from the Bristol Aircraft Company (1949).
Web links
Individual evidence
- ^ Helmut Werner Bönsch: Introduction to motorcycle technology . 3. Edition. Motorbuch Verlag Stuttgart 1981, ISBN 3-87943-571-5 , p. 50
- ↑ U.S. Patent 913961
- ↑ Thor trapeze fork
- ^ Christian Rey and Harry Louis: Famous Motorcycles . Heyne Verlag 1977 ISBN 3-453-52062-9 , p. 49
- ↑ U.S. Patent 1223572
- ↑ motorcycleclassics.com (accessed September 28, 2013)
- ↑ US Patent 1397850 (1921)
- ^ Helmut Werner Bönsch: Introduction to motorcycle technology . 3. Edition. Motorbuch Verlag Stuttgart 1981, ISBN 3-87943-571-5 , p. 51
- ^ LJK Setright: The Guinness Book of Motorcycling. Facts and Feats. 1982, ISBN 0-85112-255-8 , p. 31
