How much time do you have??
Yes, I worked in Bad Homburg.
Here is an abridged history:
Harry Vickers in California invented the "balanced vane pump" in 1925
The first industrial application was found as a power steering pump and was used on a 1929 Oldsmobile.
Harry moved to Detroit and founded Vickers Inc
In 1938 (? maybe) Vickers was taken over by the Sperry Corporation and became known as Sperry Vickers.
After WWII, Vickers expanded the manufacture of p/s pumps and became the major supplier of hydraulic power steering pumps to all U.S. car manufacturers.
In the late 50s, GM tried to persuade Vickers to invest on a greater scale in order to supply the growing demand of pumps as the p/s option took off.
Vickers was very concerned about GM's treatment of suppliers as in 57/58 they had convinced Timken to build new plants to supply all of their wheel bearing requirements and then turned around and bought New Departure Hyatt and made the bearings in house. This almost caused Timken to go under.
Vickers refused to expand and licensed GM to build the pump. They did at their Saginaw Steering Gear divsion in Saginaw, MI. In the 80s you could visit Saginaw Steering and you would see in the museum the first pump they ever made was a Vickers design pump.
In the following years, GM played the usual "strong arm" game when all production fluctuations were taken out on the Vickers share.
As a result, Vickers , who by that time was a full-line industrial pump manufacturer, decided to get out of automotive in the late 50s/early 60s.
In 1962, Daimler Benz decided to introduce power steering as an option on their passenger car lines and turned to Vickers to supply the pump.
At that time, Vickers had a plant in Bad Homburg, close to Frankfurt, where they manufactured and serviced hydraulic equipment for industrial equipment for GM's Opel plant in nearby Russelsheim. This plant was the defunct "Horex" motorcycle plant which Vickers had acquired in 1958.
Vickers agreed to supply DB, but restricting themselves to this being the only automotive supplier. The first year, the pumps came from the U.S. until production started in 1963. (I was still in bad Homburg, when we celebrated the supply of the 1 millionth pump to DB.)
When p/s became standard on many vehicles, DB required a second source and demanded Vickers to share the design with ZF. In the beginning, ZF bought the vane type rotating group from Saginaw
As a result of losing some of the business, Vickers local management in Bad Homburg decided to turn to other German OEMs and as engineering was in Germany, they were able to design pumps for BMW and later Porsche. (The infamous 959 had a Vickers pump)
There is much more to say, but it would make for a nice book, which I may decide to write one of these days....
But you see, this explains your original question why the pumps had SAE threads....
As mentioned in the thread you link to, the U.K. "Vickers" company is different from Vickers Inc in the U.S.
Vickers in the U.S. was divested by Sperry in 1984 and merged into LOF - Libbey Owens Ford. When LOF sold theur glass division to Pilkington Plc, the name went with them and the remaining companies Vickers, Aeroquip and Sterling Engineered Products (Plastics) renamed themselves "Trinova".The Vickers Automotive portion with main assets being the plant in Bad Homburg was sold in 1991 to German automotive supplier LuK (mainly clutches back then). In 2006, Luk Automotive Hydraulics was sold to Private Equity and renamed "ixetic"
In 2012 "ixetic" was purchased by Magna International and the hydraulic engineering and expertise around power steering in Bad Homburg was dismantled.
