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Constrictor/Simplex hybrid

Posted: Monday 21st September 2020

Author: Robin Walker

I thought folk might be interested in the modifications I have done to a Constrictor gear to improve it’s effeciency :-

The Constrictor gear is, in my opinion, beautifully made and rather underated. It is worth remembering, that as a deformable parallogram gear, it preceeded the ubiquitous Campagnolo Gran Sport by 3 years! However, despite it’s upper sprung pivot, it’s performance is let down by a single roller. This can be easily modified by removing the single jockey wheel and adding the cage and two jockey rollers from a Simplex Tour de France derailleur as seen in the photos. This is a “period correct” modification as both Simplex and Constrictor marketed these gears at the same time. Chain gap and chain wrap around the freewheel are now much improved, resulting in a faster and snappier change. The gear will easily handle a 4 speed 3/32 frewwheel 24 – 14. I am now working on how to spring load the lower pivot and incease capacity to 5 speed – watch this space!

Thanks for reading

Posted: Monday 21st September 2020

Author: Robin Walker

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