Dominator 99 gear box

Hello again George - That's a coincidence. I had a 1955 Ariel Red Hunter with an Ariel gearbox  that began with GB8 ---- .  Apparently the gearbox was an Ariel produced, licensed copy, of a Burman B52 box.  I wonder if  Burman had anything to do with the Norton Laydown series ?  Or is that just a really weird ?   Unlike yours, my 1956 Dominator 88 had an AMC offering.   Sorry I can't offer anything more substantial.  Kind regards, Howard

Raleigh (of bicycle fame) used to make motorcycles.  If their engines, and particularly gearboxes and clutches, were sold as proprietary parts to other makers of motorcycles, they were sold as Sturmey Archer - eg the boxes in Brough Superiors and Nortons.  In 1932, Raleigh stopped making motorcycles.  Norton were the biggest customer for SA gearboxes, and they bought the design rights to it.  They had no experience, expertise or tooling to make the gearboxes, so they commissioned Burman to make the gearboxes for them.  The Norton gearbox of 1934 onwards, known as the 'Dolls head' box is a slightly modified Sturmey box. 

All subsequent Norton gearboxes are developments of the SA box.  The post WW2 box had the end cover enlarged so that the clutch lifter worm was enclosed, but was otherwise the same box.  The horizontal box had a greatly improved gear selection by moving the positive stop mechanism to a forward position.  It eliminated the external linkage between positive stop mechanism and the cam plate sector, which removed a bad source of wear and lost movement.  It also had different mounting method, being between engine plates on featherbed models instead of the slotted upper mount which was prone to wear and fracture if neglected.

After the featherbed debacle (the frame-makers were Reynold (coincidentally, in later years they were part of the same group as Raleigh and Sturmey Archer), and for some reason were incapable of ramping up production to useful quantities), Norton went bust in 1954, and got bought by the Collier brothers and became part of AMC.  They liked the Norton box, and decided to adopt it for all their 'heavyweight' models. The gear cluster remained the same basic design, but there were a number of useful developments.  The positive stop mechanism is a very neat clever item, and the cam plate has a very rounded index profile giving high lift to the cam plate plunger.  This has the effect of pushing the box into gear if the rider does not fully depress the lever.  Another change is that instead of relying on a bronze thrust washer between the 3rd gear mainshaft pinion and the sleeve gear, it clenches the mainshaft against the outer cover.  A less-well liked feature is the clutch lifter mechanism, which has a heavy action and high lift ratio particularly at the beginning of lift.  But it can be modified....

So there you have it.  All Nortons (apart from Jubillee and deriviatives) from 1934 to end of Commando production had a box descended from the Raleigh / Sturmey Archer vintage box.

Amusing factoid.  The classic Sturmey bicycle hub gear has ratios 1.33:1 from each other (0.75:1, direct, 1.33:1, making an overall ratio of 1.78:1).  The SA racing 3 speed motorcycle box had ratios 1.33:1 from each other, viz direct 1:1, 1.33:1, 1.78:1.  Exactly the same as a bicycle box, still used today in the 3-speed AW hub gear.  The SA racing 4 speed motorcycle box got an extra ratio below direct top, of 1.1:1, but retained the same lower ratios.  That's your racing International and Manx box, to the end of production.

Another amusing factoid:  The early AJS 7R got a magnesium-cased racing Burman box.  It used a Manx Norton gear cluster, different only in the mainshaft length.  It's a long time since I saw one, so I would be interested to know what gear shifter mechanism was used

Paul