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Chater-Lea chainwheel adaptors

Posted: Thursday 11th June 2020

Author: Chris Grange

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.

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.

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.

Materials for both the above changed to cast aluminium.

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.

Chater double 3/32 adaptor - click for larger image Spacer 7mm - 'ears' 3mm
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.

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.

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.

Morris Ashby destroyed the dies as the machine they fitted was scrapped.  Mr Chater-Lea’s notes state “we did not want anymore anyway”.

The above adaptors were for use with Chater-Lea bottom bracket shells with the following axles:

1307      Axles 805 Front and 802 Rear
1307-1   Axles 1007 Front and 1240-1 Rear

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

Thanks for reading

Posted: Thursday 11th June 2020

Author: Chris Grange

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