The Vincent Girdraulic fork legs are an instantly recognisable feature of later Vincent HRD motorcycles. The legs are handed but cleverly machined from a single forging. Some people say that they were produced for Vincent by the Bristol Aircraft Co. but I have read that this is not actually true. Anyway, the fork legs featured the part number and ‘MADE IN ENGLAND’ cast into the bottom of both sides and then these were machined accordingly, producing a handed leg with the cast-in script visible on both sides. This avoided the need for handed forgings.
The fork legs of 2751 have had the script ground off. I feel that this would have been done at the factory to give the legs a smoother appearance devoid of casting numbers.
In 1949 Vincent HRD motorcycles were abandoning the proprietary Brampton girder forks in favour of the Girdraulic forks of their own design. So, this was an early set of Girdraulics that was further fettled to give this early Grey Flash a more “finished” look. Later on we will strip the paint off to hopefully reveal what should be (according to the Works Order Form) an anodized finish underneath. At this time it will be apparent whether the script cast into the fork legs was ground off prior to them being anodized or not.
Genuine Grey Flash fork legs differ from all other Girdraulic fork legs fitted to other Vincents, racing or otherwise, in one other important way: the inside face of each leg is deeply milled for lightness.
The amount of alloy confidently milled out reflects how carefully calculated this operation was – rigidity could not be sacrificed for the cost of lighter unsprung weight. This would not have worked for the heavier and faster Black Lightnings.
Additional: the below comment on this post by Somer got me scratching my head… Over the next few days I started going through my data and I think I’ve found the additional feature that the learned reader was referring to. Grey Flash Girdraulic fork legs were further modified in one other way: a bevel was machined into the forks to relieve material where the FF32 bridge plates bolt onto the forks.
When the legs are stripped I will add details of this feature to the ‘Restoration’ section of this blog. Thanks Somer!
25.10.2019 David Dunfey has been in touch and kindly sent me this photograph showing the bevel in detail:
David also told me of one other very hard-to-find feature that is unique to racing Vincent Girdraulic fork legs. I have elected not to reveal that in this blog as David has his own notes on racing Vincents and will reveal all in good time. And he should be given much credit for his deep knowledge of this very specialised subject and detailed analysis of every component that sets the racing models apart from the road-going machines.