Norton Model 50 350cc
I've managed to get to the Model 50 again after our move here to Orkney, in between sorting out the workshop plus working on the house and building a conservatory/greenhouse for Chris. It came up here pretty much as it had been for the last *%$£%^ years, that is to say, as a frame with an engine. In the intervening period I have collected a great many parts, mainly thanks to the coming along of eBay, but I have also made quite few parts or refurbished existing stuff.
It was the first bike on the bench in the new workshop, and having joined the Orkney Vintage Club, it seemed a much more suitable thing on which to attend the runs and shows. Not that I have been embarrassed to attend the annual Vintage rally in the last 2 years on my 350 Four and the GB500TT and Christine even attended with the Jaguar XJS-C.
I had originally thought of fitting glass-fibre mudguards, but I turned up a very useable front one minus stays from Old Bike Mart and then set to, to make the thing fit. I made a thick card template for the bridge piece and fiddled around with the height, so that the guard followed the curvature of the front tyre. Using the template I then cut the shape out from a piece of 3mm steel sheet, using a very thin (1mm) cutting disc in the angle grinder.
One of the many great things I love about living here in Orkney, is that I can do this sort of work outside in the open air (with fantastic views over the Atlantic!) without annoying anyone or covering the workshop with grinding dust. As you can see from the picture, the bracket needs to be wide enough to pick up the two fork leg mounting holes on each side, it then needs to be narrowed (when viewed from the front) to clear the fork shrouds and the top hoop has to be somewhat less in width than the rest, so that it conforms better to the curvature of the guard. One thing I am intending doing is to make up some thick, shaped washers to allow the bracket to be fully tightened without 'dimpling' the surface.
The next stage was to source some dural tubing to make up the stays - this came from a suppliers I used to use during the course of my last job in the Spinal Injuries Unit. I contacted Simmal near Preston, Lancashire with my requirements and they sent me the cut lengths, well packaged in extremely quick time and at a very reasonable price. They are a really helpful company and have thousands of shapes and sizes and specifications of aluminium alloys.
Before any forming operations can be done with the tubing, it first needs to be annealed. We probably all know that aluminium hardens with age and work, so it needs to be brought to a condition where it will not crack when bent. It needs to be taken to a temperature of a little under 250 deg C and allowed to cool - there is no advantage to quenching aluminium as there would be with copper, but it is quicker and might prevent someone from picking up an innocent looking piece of hot metal! The way I test for the correct temperature is to heat it with a gas blowlamp and wait until the metal itself will char the end of a scrap of wood stroked along it. Another method is to rub the end with soap until it turns black - but there was no soap handy in the workshop that day!
I didn't want just a straight ended flat on the tube, so I filed a curved shape on a scrap block of ally so that the flattened end would have a more professional look - it also avoids sharp changes in section which can cause stress cracks in service. It's at times like this when I'm glad I served my apprenticeship as an aeronautical engineer!
It was then a matter of juggling all the bits into position in the vice and turning the handle with my knee (there is never anyone around at just the right time is there?) before finally squeezing the flat on the end.
The above shot shows the char mark left from the annealing process and the nicely shaped flat. All that needs doing then is to shape the end and drill the hole. A bit of trial fitting is next, to make sure that the angles are correct so that it just falls into place when fitted, without the need to twist anything to get the bolts in. It's also imperative that the two ends have their flats in alignment.
Only 3 more to go!
The end result is quite pleasing, but there are a few minor dings and some pitting to fill and flat down before it will be ready for final paint. Although no longer a legal requirement, I also intend fitting a front number plate and that will be another little fabrication task, plus a bit of turning and threading for the 2 pillars, followed by a bit of silver soldering.
There are a couple of unwanted holes which I will blank off and a split lip to repair by silver soldering. I also intend making up some packing pieces to insert between the 4 stays and the blade to clear the rolled edge without distorting the curve when tightening the nuts and bolts. These will also be silver soldered in position to aid assembly. Everything is to be trial fitted in the brushed on primer stage, so that any rectification can be easily carried out without wishing you had fitted that part before final painting - yes, we've all been there and done that! Eventually it can all be dismantled and painted properly, reasonably safe in the knowledge that final assembly will be a breeze!
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