DISRAELI GEARS

Gradient

UK Patent 1896 1,570 - Gradient main image Gradient 3 speed main image UK Patent 1899 5,317 - Gradient main image

Although the French like to claim that Jean Loubeyre’s La Polyceler was the first derailleur, Union-Jack-Waving-Yorkshire-Pudding-Eaters can make a case for claiming that Edmund Hugh Hodgkinson’s Gradient gear system as the first commercially available derailleur system. Whereas it may possibly be questionable whether Loubeyre’s La Polyceler ever made it into serious production, the Gradient undoubtedly did.

Edmund Hodgkinson was a London based engineer who applied for a patent for his first ‘Gradient’ derailleur system in 1896 (see UK patent 1896 # 1,570). The system involved a two speed cassette of cogs sliding sideways on the rear hub, while a chain was changed across them using a chain lifting device. The patent describes two different ways of operating the chain lifting device, one by a lever and rod linkage system operated by the rider, the other by pedaling backwards. I believe it was the back-pedaling option that was first adopted for production - but I am not sure about this! As I understand it, the sequence of operation was as follows; first the rider back-pedaled to lift the chain, then the rider shifted the cogs using a lever and rod linkage system, then the rider pedaled forward and the chain was moved back into contact with the new sprocket that was now in line. This fantastical device was successfully sold commercially, and I believe that it was on sale before the (much simpler) Whippet New Protean system.

In 1897 and 1899 Edmund Hodgkinson applied for two further patents, greatly refining his basic design (see UK patent 1897 # 16,715 and UK patent 1899 # 5,317). His later designs were three speed systems, which, in defiance of modern convention, had the small cogs on the inside and the large cogs on the outside. Frank Berto comments that a three speed Gradient system made quite a splash at the 1899 Stanley Show. By 1899 the chain lifters were definitely operated by back pedaling.

However, in the early years of the 20th century British cyclists became infatuated with the new epicyclic hub gears produce by companies like Sturmey-Archer, and derailleur systems became hard to sell. In 1904 Edmund Hodgkinson sold his patents to the Terrot bicycle concern in Dijon in France.

Terrot went on to manufacture two designs that were closely based on the Gradient - the 1905 Terrot Modèle H and the 1910 Terrot Modèle HE. Both of these included chain lifters and maintained a straight chainline by sliding the freewheel sideways.

The relative success of the Terrot Modèle H also inspired a raft of other, simpler, French designs that did maintain a straight chainline by sliding the freewheel sideways, but did not include the complex and fragile chain lifters. Notable examples are the Audouard and Terrot’s own Terrot Modèle HT. Finally it is hard to think that TriVelox were completely unaware of all this earlier work on such systems.

However, although the Gradient can make some claim to be the first commercial derailleur, its basic design represents something of a dead end. It gradually became clear that the gains from maintaining a straight chainline were trivial - and were greatly outweighed by the complexities of sliding freewheels with increasing numbers of cogs from side to side.


see also UK Patent 1896 # 1,570

see also UK Patent 1896 # 1,570

UK Patent 1896 1,570 - Gradient thumbnail


see also UK Patent 1897 # 16,715

see also UK Patent 1897 # 16,715

UK Patent 1897 16,715 - Gradient thumbnail


see also UK Patent 1899 # 5,317

see also UK Patent 1899 # 5,317

UK Patent 1899 5,317 - Gradient thumbnail


see also The Science Museum - Gradient 1899

see also The Science Museum - Gradient 1899

The Science Museum - Gradient thumbnail


see also Terrot & Cie. Cycles & Motorcyclettes 1905

see also Terrot & Cie. Cycles & Motorcyclettes 1905

  • Publisher: Terrot
  • Date: 1905
  • Derailleur brands: Terrot
  • Derailleurs: Terrot Modèle H
Terrot & Cie - Cycles & Motorcyclettes 1905 front cover thumbnail


see also Terrot poster - 1905?

see also Terrot poster - 1905?

  • Publisher: Terrot
  • Date: 1905?
  • Derailleur brands: Terrot
  • Derailleurs: Terrot Modèle H
Terrot poster - 1905 thumbnail


see also Terrot poster - 1906?

see also Terrot poster - 1906?

  • Publisher: Terrot
  • Date: 1906?
  • Derailleur brands: Terrot
  • Derailleurs: Terrot Modèle H
Terrot poster - 1906 thumbnail


see also French Patent # 422,255 1910

see also French Patent # 422,255 1910

French Patent 422,255 - Terrot Modele HE thumbnail


see also Terrot & Cie. Cycles & Motorcyclettes 1910

see also Terrot & Cie. Cycles & Motorcyclettes 1910

  • Publisher: Terrot
  • Date: 1910
  • Derailleur brands: Terrot
  • Derailleurs: Terrot Modèle H, Terrot Modèle HE, Terrot Numéro 1
Terrot & Cie - Cycles & Motorcyclettes 1910 front cover thumbnail
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