Caprotti valve gear

This slow pan allows you to look at the detail

 

 

This is of course 'British' Caprotti

 

 

If your wondering how it works then the

drawing above should give you an idea

 

Thanks to National-Preservation.com I include a description of

how this gear works.

Caprotti gear uses two cams per inlet valve, each with a constant profile giving lift over maybe 40% of a complete revolution. There's a rocker lever between the two of them, so the valve is only lifted if both the cams are lifting. By changing the phase angle of the cams relative to each other, you can get anything from 0% to 80% admission for a given power stroke. Numbers illustrative only. Anyway, because the cam profile is constant, it's nice and easy to keep contact stresses manageable. The complexity is in the cam phasing gear, although I suppose the rocker could be a weak point too.