Frame Bridges

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SEAT STAY BRIDGE DETAIL

Four different style of seatstay bridge, evolved over the life of the company ;

Mid 1930's to 1948	Straight Only
	A Simple tubular bridge with flanged (swaged) ends and an internal support for the brake mounting bolt. This support was a small additional piece of tubing, fitted to prevent the bridge from collapsing when the brake was fitted and tightened up.

1949 - 1951	Curved Only (Ver.1)
	Again a simple tubular bridge with an internal support for the brake mounting bolt. This change introduced the curved shape that remained unchanged for a long number of years, however the ends were not flanged but simply mitred to fit the seat stays.

1952 - ? (Approx. 1954)	Curved with Brake Support (Ver.2)
	The first change, was the extension of the internal bridge support by 3/16" outwith the bridge towards the front of the frame. This was introduced to provide better support to the brake assembly and to prevent it from pivoting under hard braking. It is not unusual to find frames without this support having the bolt hole enlarged / opened out

? Approx. 1954 - 1980	Curved with Brake Support & Strengthening Pieces (Ver.3)
	The final change made was by the addition of diamond shaped strengthening pieces. these were brazed to the seat stay's and to the bridge.

Both the straight and curved bridges including the version with the strengthening plates, can be found without a brake bolt hole. This applied to some path frames and all pure track frames where there was no requirement for a rear brake, hence a plain bridge was used.

Where a frame has been modified by an owner to allow a rear brake to be fitted, the hole will generally not have the small internal support, used to prevent the tube from collapsing. If you can see the open edges of the bridge tube through the bolt hole, this has probably been the case.

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