Chater-Lea chainwheel adaptors
Author Chris Grange1929
A provisional-patent cast iron adaptor was introduced for use on Chater-Lea 12A Race and 15A Lady-back tandems with straight-through drive. This was to replace the existing riveted double-chainwheels with two standard chainrings enabling riders to "dissemble and fit alternative chainwheels expeditiously".
The gap between the chainrings was 7/16" for use with 1/8" or 3/16" chainrings and used a bolt 'A50P': 126/1 15/16" long under head.
1931
The same adaptor (now fully patented No 317171) used on Chater-Lea tandems 12B, 22, 26 and 15A and given a part number 1307. Bolt as above.
1931
Adaptor 1307-1 used on Chater-Lea tandems 14A, 42, 46 and 47 with a gap between the chainrings of 11/32" and using bolt A44: 126/1 13/16" long under head.
1934
Materials for both the above changed to cast aluminium.
1938
A special narrow adaptor 1307-2 was produced for Claud Butler for their Chater-Lea equipped race tandem with a 1/4" gap between the chainrings and a bolt A41:126 3/4" long under head.
POST-WAR
Right: Chater double 3/32 adaptor- click for larger image
Spacer 7mm - 'ears' 3mm
Adaptor 1307-1 was changed to a shell mould casting by Starling Foundries Limited of Croydon. The patterns weremade for them by Chater-Lea, who then machined and drilled the castings.
1953
A new solo-cycle adaptor 1689 was produced by Starling Foundries Limited for use with the post-war cranks. The gap between the chainrings was now 1/8" with bolts 9/16" long under head.
1954
Adaptor 1689 now produced by pressure die-casting and completely manufactured by Morris Ashby Limited of London E8. This adaptor was fully finished requiring no machining or drilling. The outer face was polished by Chater-Lea.
1968
Morris Ashby destroyed the dies as the machine they fitted was scrapped. Mr Chater-Lea's notes state "we did not want anymore anyway".
Notes:
The above adaptors were for use with Chater-Lea bottom bracket shells with the following axles:
Tandems
1307 Axles 805 Front and 802 Rear
1307-1 Axles 1007 Front and 1240-1 Rear
Solos
1689 Required axle 1615-1 for brackets with 1/4" balls and axle 1240-1 for the earlier bracket with 5/16" balls.
The post-war machined Chater-Lea cranks had 1/8" thick arms as against the pre-war forged ones which were 3/16". The bolts on all Chater-Lea cranks have a thread size 17/64" x 25TPI Whitworth