The Blog Oldracers posts - Grey Flash Diary Apr 2013

Grey Flash Diary Apr 2013

finished grey flash

As I looked around the piles of parts surrounding the engine it looked like it was time to start the final build. And I started, the tank came back looking immaculate with 1950 transfers and matching the existing paint. I reattached the gearbox and positioned it via the adjustment bolts so that the belt drive was at the right tension. I fitted the UFM and RFM (which in the interim had had its interior tubes well covered in corrosion preventative lube) slipped on the modified Vincent damper and spring units and secured them.
One of the items often thrown away with alacrity on racers is the steel reinforcement strip under the rear mudguard. I understand the weight saving logic, but this can result in a fretted unsupported guard. Although Supermarket DIY type stores hold little in the way of material suitable for a vintage racer, they do offer a nice selection of thin half hard alloy strips very close to the dimensions of the original steel strip. What DIY jobs within the home whose need they are supposed to fulfil, I cannot even guess, but it makes a good lightweight support to the rear guard now fitted in place on the RFM
Number one job on the forks was setting up the bottom link, eccentrics, spacer’s shims, steering crown lug and spindle. To play with these on a set of partially assembled forks is a nightmare. Done on a bench with a set of feeler gauges and a torpedo tool and it’s an enjoyable job. Apart from light assembly grease, on a racer I think it’s easier to oil them before each race event, rather than to apply great dobs of grease. After my initial assembly I try and leave them submerged in some gear oil for a day or so before continuing. The assembly of the blades and links went without a hitch another conformation of the theory that it’s never the items that you expect to be difficult, that are difficult, and its a supposedly easy tasks that can take days.
I am very pleased with my Comet engine cradle that allows me to build the engine and then attach the rest of the bike, all on my workbench with wheels off the ground, but it does unfortunately leave me with the UFM in the ‘normal’ position. Those of you that have not yet gone to a taper roller headstock (and that includes me) know the ‘fun’ of inserting the F33AS (in my case complete with the assembled forks) into the UFM without the headstock being vertical. It seems that however thickly encrusted with grease the lower ball bearings are, as the unit goes home you here the clink of a fallen grease sodden ball from the lower race (Or worse, you don’t hear, or find it, and I am sure as a result many bikes have relied on 19 instead of the full compliment of 20 balls). However all is solved, I stuffed a round rare earth magnet up the steering Colum and the 20 little solders stayed solidly in position as I hoisted them up to their “place in the race”. Then with the forks in place I then made up a little plate to reduce the steering lock.
I believe a modern Hydraulic damper is essential for a racer and as it is so obvious a modern addition at least it should look neat. For years we have had a hydraulic damper on the Comet racer with a bracket from the head for one end and an eye bolt instead of the FF53 that also holds the spring box at the other However I remembered a reply on a forum thread about this method by Bill Thomas warning about putting too much strain on a critical component, (not that we have had any problems in all the years we have raced the Comet. but on the other hand we have never had a tank slapper.) Viable mounting alternatives involved removing the standard damper, but I would like to keep that in use as a back up and keep the riders cockpit looking standard.
My solution to the front fixing was to replace what was normal steel FF53 (or stainless!) bolt, with a high tensile Allen bolt and turn up a one piece recessed cross drilled hollow socket and tab to provide the end pivot for the hydraulic damper and the trunnion function for the spring box. I then made up a plate and pivot to secure the other end to the head.
In the bitter cold of a spring day I finally found time to read all the thread on girdralic suspension. while I stick to my existing arrangement on the Comet (If it isn’t broke etc) I found the arguments of David Dunfey very convincing so rather than adding long eye bolts and an inch of broom handle to my 16” springs I have contacted Norman Walker and purchased a set of the weakest ‘Dunfey’ springs. (It’s a real accolade to get a set of springs named after you; older members will remember the ‘Pettiford’ springs often quoted back in the day for the rear units). While I think the Flash will end up slightly lighter than the quoted 330 lbs. I don’t think I am quite as slim as I should be, so I will make up a set of 4 interlocking spacers each of which will increase the length of the spring by ½” to use as required. (Assuming I don’t have to go up on spring strength) I was also spared my spring box tourniquet routine with nylon rope and bruised knuckles.
Scrabbling round in my parts store I found a front brake balance arm covered in a myriad of holes (the sort of thing to drive a concours man wild.) It came from the comet racer when I still had the standard brake set up so I must have had it over 40 years and it was drilled when I got it at a section bring and buy (remember them?), that piece of history has to go on the front.
The rear torque stay contains the requisite row of 13 X ½” diameter holes but one item of touring equipment I have always retained rather than the oft suggested circlip is the sprung retainer FT166 its microscopic weight is easily offset by the speed of removal of back wheel especially between races when a different sprocket or a new tyre is required.

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