New Camshaft and Crankshaft sprockets for Sunbeam Talbot Ten sidevalve engine

New Camshaft and Crankshaft sprockets

Original sprockets on car

I'd never been happy with the timing chain setup on the Ten, it was noisy with a large amount of slack in the chain with plenty of wear to both sprockets. It also included a later Hillman rubber tensioner which seemed an odd fit having not seen any mention of it in the parts book. It did remove some slack in the trailing edge to a degree but did nothing for the wear in the sprockets and stretched chain.

Speaking to others in the club and the usual suppliers it became clear replacements were no longer available and my best option was a “used set” with less wear, downside any used set will be of a similar age.

We looked at later Rootes cars but couldn’t see anything directly compatible or that could be easily modified.   Some early MG cars came close and we looked at modifying the centre from an upgraded MG vernier pulley but just seemed overly complex.

That left us with the idea of manufacturing from scratch. For either of these options we really needed the original drawings.

A huge thanks is due to James Spencer at the https://www.rootesarchive.org/ who kindly forwarded copies of the original engineering drawings for both sprockets.

I only need 1 set but a small batch could lower the cost assuming I can sell on the remaining spares. With printed drawings in hand I approached some local machine shops, in fairness to them; an enthusiastic owner arriving in an Austin 7, waving printed drawings probably didn’t help matters but ultimately my lack of budget was the limiting factor. I’m extremely grateful for the time and ideas they suggested to simplify the manufacturing process.

20 Tooth Sprocket

   

40 Tooth Sprocket

Their main suggestion was to move away from the idea of creating from scratch and modify an off the shelf sprocket. These sprockets are available from bearing suppliers as single, duplex, triplex etc in a range of diameters, pitch and tooth count. 

For the Ten we chose a basic pilot bore which leaves almost enough material to turn it into what we need.

Chatting about old cars with an even older friend, while being ribbed on the lack of progress re-wiring the Ten, my poor life choices and general state of the garage the discussion moves to sprockets.  “Oh, why don’t you speak with Dafydd at DGL”, if only he had said this at the start!  

20 Tooth Blank

40 Tooth Blank

Dafydd’s plan was to re-create the drawings in CAD, remove the bulk of the material on a manual lathe before finishing on a CNC Milling Machine.

4 further sets are available to purchase. Price at £200 + £10 UK postage per set. It includes both the Camshaft and Crankshaft Sprockets. I'd recommend sourcing a new timing chain, the chain is not included,  Happy to post abroad if required.  

Email jollysoutherner@gmail.com