Re: McCulloch VS57 on a 359 Straight Eight

Posted by Rusty O\'Toole On 2011/6/3 21:05:34

The impeller of the McCulloch supercharger is a pinwheel 4 or 5 inches in diameter. In operation it spins up to 50,000 RPM.

This was achieved by a double gearing up. First there was a variable speed pulley arrangement. This could go from 1:1 or less up to 2:1 or a little more. There was a fixed pulley on the engine crankshaft, a variable speed pulley on the end of the supercharger and a spring loaded jockey pulley. The variable speed pulley was controlled by an electric solenoid built into the supercharger, and internal air pressure.

Second was a sort of planetary gearing using 5 ball bearings about an inch in diameter in place of gears. The ball drive was arranged to give a step up gearing of 5:1. It worked by friction.

So, there was a possible total gear ratio of 10:1. The impeller never spun the full 50,000 RPM because the engine would have to be revving 5000 RPM and at that speed the supercharger would be backing off to prevent over boosting.

I don't know about reliability issues. They were considered reliable enough to be installed at the factory as optional equipment by Kaiser, Studebaker and Ford. Studebaker used them the longest, from 1957 up to the early sixties.