Vincent Black Lightning Home Page

9. Front Forks

Forks
Much as I love Vincent's, I would have to say that the overall design of Vincent Girdraulic forks seemed at best, quirky, and at worst seriously outdated by the time they appeared in the late 1940's. While many other manufacturers had moved towards fully damped telescopic forks, Vincent's had produced what seems to have been a girder/telescopic hybrid.
I know I risk being forever ostracized from other Vincent owners for voicing this opinion, but from a racing point of view you need only look at results from this era to see that racing success was being influenced by chassis design at least as much as by engine development. I know that there were very successful Vincent riders out there, but I cannot help but think that the likes of John Surtees and George Brown could have made a wheelbarrow handle.

Vincent Girdraulics
Taken from 1950 Catalogue

What I am trying to say is that when I decided to build a Vincent for racing, it was as much because I loved the idea of building a Vincent as it was because I thought it would be unbeatable in its class.
Sure, I was hoping that the power of a big Vincent might give me a better chance of being competitive, (an area that I had been struggling with my overstressed ES2 based Norton), but I was not expecting it to be up to much in the handling stakes.

Unusual Solutions
I admit that even now I have still not raced a Vincent in anger, so I can only speculate, but I am not expecting miracles and it might be this aspect of the bike that determines how I use it once it is finished. When I first started building the Vincent, Mickey Carter was racing a very potent Vincent in the unlimited pre-58 class. If you looked closely at this bike (see photo) you could see that some very novel ideas had been incorporated into the bike to improve handling (I believe well known Vincent exponent John Renwick had helped with this development). The main feature is that the centrally mounted damper had been replaced by a modern spring/damper unit, that looked fully adjustable. This alleviated the need for the spring boxes behind the blades and these had been removed. It had been done very neatly and therefore was quite inconspicuous.
Also visible, (although not immediately obvious) was a rod seemingly connecting the lower fork link to the petrol tank! On closer inspection all became obvious, a false fibreglass petrol tank had been fitted and through this protruded a steering damper. The 'real' alloy petrol tank sat underneath, on the right hand side of the UFM, which also left room for a battery to be fitted on the left side. At the time I was quite taken by these mod's, fully intending to try something similar myself (in fact I did buy a false tank from John myself), but have conceded that I am now unlikely to race the bike seriously and have settled on a more traditional setup.

Things are not always what they seem!
(see text)

Refurbishing the Forks
So then, back to the restoration. When purchased, the bike came with all the main fork castings but most spindles and fittings were gaff and would need replacing. Some of the bearings had already been bought and only needed fitting. All the major components seemed in very good condition and the only bits missing were handlebar clamps, damper and brake beam. The Brace Plate (FF32) between fork blades did look to be a little flimsy so I made a new slightly thicker version from 1/8" aluminium plate.

Actually, a brake beam did come with the bike, but for some reason one side was missing (see photograph), although I have no idea how. I did not really feel comfortable abut welding a new piece onto something as important as this, so held off in case I found a better one. A few years later, while helping an old friend unload some of his autojumble items at the Founders Day Rally, what should I find in the back of his van but a complete set of Vincent forks. He very kindly let me have the brake beam off them, before putting the forks out on display. Needless to say, despite the sickly green paint, the forks had sold within 15 minutes!

Old fork spindles had definitely seen better days . . .

. . . As had broken Brake Beam

I bought new spindles and replaced all nuts bolts and fittings with stainless items from Maughan and Sons. At this point it is probably worth pointing out that the Maughan family, apart from being fine engineers, produce the highest quality stainless nuts and bolts I have ever seen. Each bolt is a work of art with every bolt face burnished to a beautiful bright satin finish. In my opinion, it's this sort of finish that makes the difference between the average restoration and a real quality restoration. I normally end up having to make most of my own fastenings when restoring a bike, but in the case of the Vincent I allowed myself the luxury of buying 90% of them from Maughans.

Stainless Half Nuts came from Maughans.
Faces are burnished on every nut

Eccentric's new Sintered Bronze bearings were not used in the end

I passed the Lower Fork Link (FF3) and new sintered bronze bearings to Don Alexander so he could ream them after fitting. In the end though, Don fitted his own one piece bearings which I think are a better solution. He then line reamed them both together to ensure complete trueness. I fitted the other new phosphor bronze bearings in the remaining links, and also took the opportunity to fit grease nipples (I remembered back to watching my father fitting them to his Comet when I was a boy).

Grey Flash forks, showing milled blades on inner faces

Fork Blades
One of the well known features of Vincent's racing 500cc bike, the Grey Flash, was that the fork blades were milled down their inner faces, which I assume was to reduce unsprung weight. Bearing in mind the points I made earlier about handling, I thought this was a mod well worth making so asked Don if he could also make this modification for me. I don't believe it was actually made on real Vincent Black Lightnings and I assume that this was because a lot of Black Lightnings were used for sidecar racing, presumably the risk of weakening the blades was too great. I had no intention of attaching a sidecar so did not consider this a problem (my father also has a spare set of blades should I later change my mind).

My fork blades after milling

Suspension
For the moment I have fitted a Koni damper which I aquired from Ted Davis. I am told these can be overly firm until bedded in though, so will probably fit it to the rear suspension for the first 1000 miles or so. My father has some old original Vincent dampers in his spares collection and I am quite tempted to have one of these refurbished with modern seals, I will have to see if I can think of something he wants to tempt him!
The outer springs fitted are the standard solo springs, but I have also fitted the smaller inner springs, as fitted to twins only. Originally I considered special spring/damper units (as per John Surtees bike) but have now decided against that idea on the grounds of originality.

Finish
Finally, I considered what type of finish to apply to the forks. I was tempted to have them plastic coated, which gives a very durable finish but is not always free from blemishes.
As I was looking for a concours finish for this bike, I decided to use an acrylic 2-pack paint as used in the automative trade. I have used this paint before and know that if prepared correctly it can give the most beautiful finish, but is also very durable and strong.

The secret to this durability is to ensure the base metal is absolutely spotless, then to apply a thin coat of Etch Primer, followed very quickly by a 2-pack primer. Once these first 2 coats are applied you can then continue to add coats and rub down before applying the final topcoat. As I am sure most people are aware, 2 pack paint is extremely dangerous to apply without proper breathing equipment. As the paint and hardener chemically react they rubberise, if you are breathing the paint in to your lungs the paint will rubberise on your lungs and damage them permantly. I used to carry out the painting in my largest shed, with a North mask running an air pipe out through the shed wall, which worked fine.
The finished results are extremely hard, and although I say it myself, do not look too bad at all. The down side to doing it yourself is that it is very time consuming and demands a great deal of effort be put into the preperation, especially if you do not have a dedicated paint shop. I have to say though, doing it yourself does give tremendous satisfaction and at least you know how good the preperation has been.

Deep Lustre achievable with 2-Pack paint

I found Eccentric Shims (FF9) to be a pain to fit without damaging

Final Assembly (well not quite!)
Assembly so far has proved quite straightfoward, apart from the fiddly process of building up the correct shims to the eccentrics and lower link (see photographs). There is probably a technique to fitting these shims without damaging them, but I have not found it yet. Once this was achieved, however, everything else was straightfoward.
The eagle eyed out there might also spot that the lower damper eye bolts (FF57) are too long. Not sure why I bought these longer ones, but I think they will have to be replaced by the correct shorter ones before I put the bike on the road. I'm not sure if it makes any difference but read somewhere once that it is quite important.

The only problem is that I will need to partly strip them again to fit them on final assembly, but I am hoping this will not throw up any additonal problems. I am not sure how easy it will be to fit the spring boxes, but that is a while off yet.
For the mean time they look quite nice in their own right, what do you think . . .

The completed Forks