HRD: Started by famed racer Howard Raymond Davies in 1925, after which he won the 1925 Senior TT on one of his own machines. HRD created three initial models using JAP engines, all designed for racing. Despite their quality, the bikes were expensive, so he tried to make lower-cost models, but he went bankrupt in 1928. OK Supreme acquired the name briefly only to sell it to Phil Vincent shortly after. The HRD name was dropped in 1950.
Never one of the giants of the industry, this small company based at Stevenage, Hertfordshire, had achieved quite a reputation for the quality of the machines it produced.
Their engine design was unorthodox in quite a number of respects, and it was perhaps this that suggested they had the capability of designing an engine that might rival the all-conquering JAP. Initially the company had concentrated on updating their 998cc vee twin that had shown considerable promise in 1939 but they were also anxious to revamp their pre- war 500 cc Meteor and Comet single cylinder models. From their point of view the opportunity to design a speedway engine would have fitted in well with these latter plans, as Phil Irving was then working for the company.
A brilliant designer and a first class mechanical engineer from Australia, Phil had already made quite a name for himself in Britain, especially when working for Veloce Limited in Birmingham. He and Philip Vincent worked in perfect unison to become the driving force behind the many successes the company would achieve in the years to follow. To get the speedway engine project under way 25 sets of Elektron crankcases were ordered. The use of this magnesium alloy was necessary to help keep the overall weight of the engine as low as possible. Basically, the bottom end of the engine was that of their 500cc Series A single, although it differed in having a total loss lubrication system.
Grafted on to it was a cylinder head and barrel from a Rapide vee-twin shorn of most cooling fins. Like the pre-war Meteor and Comet singles the engine was mounted vertically. A duplex Pilgrim oil pump mounted externally at the top of the timing chest provided the unmistakable sign that it was destined for speedway use. The engine weighed 54 lbs complete with magneto and carburettor (16 lbs less than a JAP) and it is understood to have produced about 40 bhp.
The first engine had its flywheels drilled and tapped so that balance weights could be added or subtracted to arrive at the correct balance factor. Usually an engine has to be completely stripped and rebuilt when each change is made, but in this engine the crankcase was also tapped on either side so that screwed plugs could be inserted. This meant changes could be made with ease. It needed only a day at the West Ham track for the two Vincent engineers present to eliminate engine vibration.
The test riding was carried out by Malcolm Craven, who subsequently was given a couple of engines to use through an entire season. Another went to Eric Chitty. It is alleged the engines proved remarkably reliable, the only attention needed being the replacement of broken valve springs, and, in one instance, an exhaust valve.
A total of 13 engines were made, but despite signs of early promise the engine never achieved the level of success intended and the whole venture proved a commercial disaster. All the remaining crankcases were scrapped bar one, which was used to form the basis of the 'speedway special' short circuit racing bike. Ridden by Vincent's George Brown it achieved considerable success at Scarborough and other venues.
NOTE: Looking through the archives, we now suspect that the Vincent "Vampire" and the Vincent HRD were in fact the same machines, the name "Vampire"
being used to add a little glitter. Maybe someone can clarify on this further.