In this post I will give instructions on how to mate with a 1940s Smiths chronometric tachometer… 🧑🏻🏫
Okay, that was a lame joke BUT such is the patinated beauty of this instrument that just looking at it positively generates an erection…
The bracket was re-profiled as outlined in a previous post. It was then sent out to be dull chromium plated for the second time…
That looks so in-keeping with all this restoration has been focused on: the icing on the cake, a veritable visual smorgasbord, a riot of the senses, an orgy of ocular splendour, a classic motorcycle aficionado’s wet dream, a… I could wax lyrical ad infinitum…
In the meantime, Bert has been wrestling with the profile of the exhaust pipe… Details of this to follow.
Sourcing the correct herringbone patterned oil/fuel pipe has not been easy… There are still some stocks of 3/8″ ID pipe available but stocks of 5/16″ ID pipe have dried up and none is currently being manufactured.
The correct run of the oil feed pipe was determined to be as above. We decided to stick with 3/8″ pipe for this as all the feed fittings present on the machine were sized to accommodate this ID – and many of them appeared ancient and possibly original to the bike. Below some shots of the other pipework in place.
The title is self-explanatory so I’ll just annotate the photos.
Running the throttle cable over the brake lever like that looks weird. In-period some were set up like this though and it’s actually the best route for the cable. We might revert to running it behind the lever later on – it can be changed easily enough.
All Vincent racers were supplied with Axle bolts rather than the T-bar arrangement seen on the roadgoing models. This is quite an obscure component and falls into the “not a lot of people know that” category… This rare racing part is depicted in the Spare Parts List.
2751 was missing these important parts and they needed to be made for the project. Where to start… No drawings or dimensions exist and few original items survive. Many years ago Vincent legend Big Sid sent me some pics of some NOS racings parts that he held and was looking to sell – these, I believe, ended up being used in the Gunga Din rebuild.
These three images appear to depict the just the one axle – an H25/3AS front item. In addition, I had a few pics of this component in situ on various bikes.
Working in conjunction with David Dunfey, and cross-referencing our available info, a drawing was made and tweaked until we were as satisfied as could be. Down in Australia, Stuart Penn kindly pulled one of the axles on his uncle’s BL and sent me the dimensions.
Yes, the Series D also utilises bolts rather than the T-bar configuration – these are available new from the VOCS and could be adapted? Well, no… In addition to the waisted centre portion, the threaded portion features a tapered end or “lead” to enable the axle to be pushed home and locate quickly under racing conditions. This taper means that the racing items are a little bit longer than they would need to be on a roadgoing bike. In addition, the bolt head is actually a nut brazed into place…
A lot of research was required to enable these axle bolts to be manufactured – the waisted portion had to be right to prevent catastrophic failure. Machined from high tensile steel, they will now need to be finished and would originally have been cadmium plated. I would like to thank David Dunfey, Stuart Penn and Franco for their assistance. 🙏🏻
Throughout its long racing career 2751 suffered many incidents that left their mark on the surviving original components. The magnesium gearbox casing bears “witness” marks from where primary chain slackness had been adjusted to the point where the casing was pushed up against the G50/2 pivot bearing plate.
Once a new primary chain had been fitted, it became obvious that more clearance was needed as the top of the gearbox casing was perilously close to the plate at nearly full adjustment. Bert got around this issue by fitting a cranked link, shortening the primary chain by just one roller.
There is a now a nice gap twixt gearbox case and plate enabling future adjustment to account for chain wear.
Bert Carefully replicated the the tacho bracket from the E.M.G. Stevens/F. Griffin drawing held on file by the VOC. The Club has taken great pains to create a database of accurate drawings for every part employed in all Vincent HRD motorcycles and “The Drawings Project” is still, as far as I’m aware, an ongoing process. Data was compared, correlated and precise drawings rendered, correcting many discrepancies previously encountered. Prior to the commencement of this project, many Vincent “pattern” parts were often found to not perform in conjunction with Works-made spare parts – there were all manner of issues that caused a lot of aggravation for enthusiasts as well as the small batch manufacturers involved in their production. So it was with the utmost confidence that Bert was able to fabricate a tachometer bracket exactly as the “Obscure Components” drawing.
This seemed fairly straightforward and the drawing enabled Bert to make it precisely. It did look a little out-of-keeping when compared to other parts on the bike though. For example, why don’t the radii match those of the handlebar clamps? It looked ill-thought-out to our eyes and at odds with the levels of detail visible on other parts of the machine. Anyway, off it went for dull chromium plating…
Once back and bolted into place Bert attached the old (incorrect) tacho head to see what it looked like. His first comment was that it was going to position the unit “bloody close” to the tank…
Period shots of 2751 and other GFs show the tachometers angled less… I ran this past David Dunfey and he kindly sent me a photo of a genuine bracket and mentioned that the “Obscure Components” drawing may have been based on a bracket employed by John Surtees on his personal Grey Flash racer.
The radii match that of the handlebar clamps – of course! A lesser angle too… Bert magnanimously agree to perform the necessary modifications and the re-worked bracket will now need to be re-plated.
Bit of a head-scratcher this one! So “obscure” is this part that no-one has ever questioned the drawing and there is very little call for such a bracket anyway.
Bert and I have been studying period photos of 2751 in order to ascertain how to route the cables and their lovely fabric sheaths.
In all the period photos the brake beam balance stop is on the “wrong” side and we have installed it this way round.
The upper fork link bears a “witness mark” where the sheath covering has rubbed off exposing the metal underneath – this was most useful helping us find the right path for the front brake cable.
Much care has to be taken with the routing of these cables to: (i) ensure that they do not foul when the forks are on full lock and (ii) are not pulled taught when the forks are fully compressed. If this happened then the front brake would likely be be actuated and the wheel would lock resulting in a situation too terrible to contemplate…
We are currently awaiting sundry parts back from the platers and the rubber hoses/ferrules to make up the oil and fuel pipes.