Mystery Gearbox

[Bob Culver]

Top marks David.
I often wonder how the draughtsman fathomed how to get the innards out of later boxes. Would be a task even with computer manipulation. Decades since I last did but Something of a puzzle even in the flesh.

[Chris KC]

Part of my engineering training, even in the late 70's / early 80's, was modelling parts from thin card. It was considered an essential skill, though it has never been called upon in my career. Nowadays 3D printing has taken over.

[Colin Morgan]

On page 40 of A7CA magazine 2019D there is an article by Jon Edgar about Freddie Henry's Nippy AOG 947.  This quotes a letter from A7CA 1980D from Freddie Henry in which he states: 

"The first trials car Wallis and I shared was a 1931 fabric saloon with one of the Ulster T.T. engines and prototype 4 speed box.  It was faster than the road holding could cope with."

I wonder if this has relevance to the four-speed gearbox above?

[jr2766]

This gearbox design could stem from Percy Riley's design for crash boxes which was introduced in the mid '20's and was widely adopted by the Nuffield group in the late 30's.
Its a clever and space saving design that in the Rileys delivered third gear via the helical gears at either end if the layshaft and top gear by a sliding dog which locked the input and output shafts
Jim Runciman
Perth
Australia