Club Journals 1 2 3 4

This page contains articles and some pictures from previous journals.
We publish our journal four times a year.
This article has been taken from the Autumn 2003 journal

“The Dot that never was”

The road going adaptation of a 1958 Dot 2T engined stripped scrambler

Of course RAS855 is not the first Dot 2T engined road bike, that Honour goes to Eric Adcock with his EAS of 1960, as was written up in Vol 8 of the newsletter (January 2001). Where the present machine differs from the EAS is that it uses the original Dot frame, forks and rear suspension.

The frame, and rear suspension, deserves some description. It is one of the 58/xxxx series which was designed for the 2T and 3T Villiers twin engines. Instead of the front down tube curving round under the engine as with most Dot frames, the down tube and bottom rail are fabricated at an obtuse angle. Much more significant how ever was that the design was a break with the established DOT practice, and indeed anticipated later trends in frame design generally in that it dispensed with the traditional bolted up rear sub frame assembly carrying the rear fork and suspension units; instead everything is attached to the welded up mainframe. The conventional rear sub-frame is replaced by two braced vertical plates welded to the top rear of the main loop, the braces reaching out to a welded on cross tube, and by two welded on cross tubes on the lower rear of the loop. The latter by means of long studs clamp between themselves and two vertical plates not the engine plates and the plates in turn provide the bearing for the pivoted rear fork.

The tops of the rear suspension units are also fixed to the mainframe by means of the upper braced cross tube. The result that the suspension units are much further off the vertical than with other Dots, give or take a degree or two the included angle between the spring damper and the rear fork, at rest and not under load, is fifty degrees.

But how did all this begin? Originally the idea had been to try and shoehorn a 2T into a 1955 Trials frame, but the factory, wisely, advised against it. Nothing is impossible, but…… The next thought was to construct a Mancunian from the 1955 frame and a search for the necessary parts began. It was whilst following up a lead for Mancunian hubs that the rather sorry remains of the 2T were found, and the concept of its adaptation for the road formed. A deal was done, and the long haul began.

The general idea was to make a bike that the factory itself might well have produced and to that end it was decided to use genuine Dot components to the maximum extent possible. An early call on the factory produced a Mancunian headlamp cowling, headlamp rim, front light sealed unit and Mancunian faired-in rear number plate assembly and various small parts. The question of a petrol tank was left to one side for the time being as inspiration was slow in coming! The original fitted to the 2T scramblers was far to small for the road, and not especially attractive visually, there was not one with the bike anyway, and neither could a decision be reached as to painted, alloy or chrome tank.

With a project of this nature, it was quickly realised that there are no standard references for the many cycle and other parts that have to be fitted to achieve roadworthiness. Where to begin? Well, there weren’t any usable wheels either, so new British Alloy rims were bought, WM1 19 inch front and WM2 19 inch rear, shod with Dunlop ribbed 3.00 tyre on the front and 3.50 universal on the rear, for the hubs, Dot Grimeca full width alloys were chosen in preference to the British Hub full-width units fitted to the Mancunian. A personal choice. The rear hub is actually a Ducati, but visually very similar, although the sprocket carrier and vane has only a single bearing as opposed to two in the Grimeca. This immediately introduced two little problems. One that the frame had originally taken ½ inch diameter wheel spindles whereas the Grimecas were carried on 15mm. Small flats were milled on the spindles to fit.

Two, having rejected the full width Mancunian style British Hub, with its built in mounting for the front mudguard, how to mount a close fitting guard (no more fixed front blade with a chunk of inner tube to prevent a face full of spray on a wet day -- effective but inelegant). The solution was to weld a rearward projecting lug to each cast bottom link, each lug drilled with two fixing holes providing a rigid mounting for a tubular loop as the lower guard mounting: the upper mount being a tubular fitted to the bottom mounting of the spring damper unit. Both hoops have a fore and aft mounting points to the guard and for a neat appearance both guards are fastened with stainless button head screws. For the guards themselves, standard steel C section was chosen, 3 7/8ths front, 4 3/4ins rear, radiused to give approximately 1in clearance over the front tyre, and at the back to permit full compression of the rear suspension. For the handlebars, early Norton Dominator bars in stainless were felt to give the right riding posture.

The next little struggle was the electrics. The original bike had only its internal energising coils and external HT coils (with unused lighting coils in situ). Fortunately this is standard practice for the 2T, in that lights, battery and rectifier are a completely separate circuit from the ignition side, so armed with the 2T workshop manual wiring diagram the latter was successfully wired up. The rectifier was replaced with a modern solid state device. For the mandatory stoplight an actuating device inserted in the front brake cable was obtained.

On the original bike, the Factory had mounted the HT coils on either side of the two vertical frame plates. It was decided to retain that arrangement and to use the same mounting points to carry a toolbox on the off and a battery carrier on the nearside. Both items were additionally secured to studs attached to the frame rear down tube. The toolbox, battery carrier and rear chain guard were drawn up and given to a local sheet metal worker. Next what to do about the exhaust system. No problem for the silencers , as the Villiers twin pattern is readily available, however the mounting

arrangements would not conform to any available variants, so they were purchased unplated, and suitable mounting brackets applied later before chroming. Similarly none of the different exhaust pipes available for various manufacturers 2T engined bikes were suitable as they stood. After discussion with Armours of Bournemouth, it was felt that Ambassador pattern was the nearest, and they too were bought unplated and subsequently tweaked to fit before chroming.

For the remaining cycle parts, a centre stand was made up and fitted, similarly a suitable brake pedal lever which, as it is fairly long, was fitted with a return helper spring. For footrests, solid steel is a personal preference and a pair was fabricated, in appearance similar to the Factory’s standard cast item, the latter not being suitable because of different mounting provision.

At the front the Mancunian cowling received a standard Smiths 3 1/2 inch trip speedo with extended trip zeroing rod, a six volt horn went into the provided cut-out , and after much searching a centre bolt fixing licence holder was found to go on to the hole provided at the other side of the cowling.

There remained the question of the tank. It was decided not to go for alloy, and the factory trawled from the depths somewhere a steel tank dating from the period, but apparently a prototype never taken further. Its suitability for the bike is a matter of opinion, but suffice to say that in its owners view it matches the twin engine very well. What to do, paint or chrome, that was the question. After much dithering it was decided to paint in the former traditional Dot cerise and silver. Finishing touches to the tank with the currently available plastic tank badges and the application of original thin rubber knee grips. The rest of the bike was finished in cerise with black suspension units, cast links, engine and frame plates, footrests, stand, brackets and pedals.

Verdict? Satisfaction with the result. So far the bike has only done a few miles on the road, to and from its MOT (passed), and is presently being worked on to rectify a problem with the sparks, but on that limited experience the handling seemed to be good. Would things be done differently starting again? Not really although a different dual seat with a stepped profile which would suit the bike better than the flat unit presently fitted. It’s a question of finding one that will fit, or can be made to. Longer HT leads are needed, also a longer clutch cable so that it can pass through the grommet in the headlamp cowling without stress. The centre stand is a bit of a struggle to use, a grab handle is needed to give a better pull on the bike and the toe plate for bringing the stand down needs modification. These things will be attended to, but that’s about it.

So, if anyone wants to build a nice road-runner, they could do a lot worse than to find one of these frames and create their own distinctive DOT. The snag is that not many were made by the factory. The exact number isn’t known, but it is thought that no more than 50 2Ts were made, and possibly a similar number of 350 RCAs. Of those 50 or so Villiers 2T (3T) engined bikes we know that about 25 went to Ireland where they were popular, but we also know from a piece in an earlier newsletter that they all seem to have disappeared without trace.