We have a few Ruston & Hornsby PT's in South Africa but they are mostly "tank cooled" versions. For shows (Rallies) we prefer hopper cooled engines as they need less water carried (often with a bucket from quite a distance away from the engine display area) and they take up less space on the back of a "bakkie" (truck/ute/pickup) allowing us to take more engines to a show.

I have a tank cooled model <Here> and acquired a hopper cooled model for restoration about a year ago. It was unfortunately without a magneto and magneto gear. Perchance I came across another collector in Natal who had a spare magneto and gear but needed a hopper. A deal was struck and off to my old friend Neville Botha who had an unrestored hopper model. We removed the hopper and cut it in half (with an extreme amount of difficulty).

The two halves were taken to our "friendly local casting plant" who produced the new hopper shown in the pics below.
I am aware that castings made from the original do shrink but in a case like this it is not important as it only really affects the holes for the fastening bolts and allowance can be made for this shrinkage when drilling the new holes. If the hopper is a few millimeters smaller overall - what the heck! As a point of interest, my "tank cooled" PT (link above) was missing the "top water jacket cover" and I had a new one cast by the same method (also using an original supplied by Neville Botha). Shrinkage was not a problem.

Converting the Ruston PT to a "hopper cooled" engine is very easy as it only involves taking the 6 fastening bolts out and removing the "top water jacket cover" from the tank cooled engine and bolting the new hopper in place. The cylinder head remains in place unlike the Rustons successor the Wolseley WD range which had the cylinder head and hopper incorporated into one casting.

Here are a few pics of the raw casting as we got it back from the casting shop today.