In 1930, Simplex made this further addition to French Patent # 669,030. The design continues to use the double pulley configuration adopted in French Patent # 669,030 Addition # 37,231. But now the main mounting bracket is fixed and the pulley cage is sprung to provide chain tension - in the style of a Cyclo.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Lucien Juy
• Country: France
• Date: French application January 1930
• Derailleur brands: Simplex
• Derailleurs: Le Simplex