The Blundell Vector - Extremely Rare and Complex 1950s Slide Rule

A very rare and complex slide rule designed by Erich Friedlander for the General Electric Company who applied for patent on 3rd July 1951 No. 15792. The complete specification was published No. 713,655 in 1954. It was made by Blundell Rules Ltd. of Luton. They wrote to the original owner, Mr. K. A Yeomans in December 1954 with sales literature and noted that one of their customers, “A well-known firm of aerial designers” had expressed the opinion that the vector slide use had resulted in a time-saving of 75%. It was offered for sale at sixteen guineas which, at current value, is approximately £437 (2020). In the event Mr. Yeomans waited until January 1955 and purchased the rule for the development laboratory he worked for using their discount at a price of twelve pounds, twelves shilling and ninepence - quite some saving, but still a significant sum.

The Blundell Vector allows usual slide rule operations together with transformations required in the use of real and complex electrical networks and enables conversion between polar and rectangular co-ordinates; multiplication/division of complex quantities; expressions of the form: sqrt (A12 + A122 + ...); trigonometric functions.

There are very few of these slide rules known to exist and this example comes on its original green board, contained within its original hinged case, the top of which which can be removed. Accompanying this wonderful instrument is the original B.R.L. brochure, the 1954 letter, typed instructions from Blundell for the use of the Vector Slide Rule, a printed copy of four pages from the G.E.C. Journal by E. Friedlander dated April 1953 and the original sales receipt from the institution. This is certain to be one of the finest to appear on the market with complete provenance.

This massive rule 380 x 210mm would make an impressive centrepiece to any collection of such instruments.

Further information, photographs and questions answered upon request.