The Advantages of the Modern Coachbuilder (continued...)


Windscreens

Introduction
Materials & Methods
Metals Used
Restoring a Body
Building a Body
Windscreens
Hood Frame
Panelwork
The Advantages...

When finalising the design of the windscreen, apart from the obvious functions on the body, it does give us the opportunity of being quite extravagant with the design and creating really quite a prominent feature. I personally believe that a screen can never be over-engineered as nearly all of its construction is visible, so let it be a feature.

On a fairly lightweight touring body, a straightforward folding arrangement is usually sufficient. They are more often folded back at an angle to achieve that rakish look than folded fully forward. But move on to a torpedo bodied touring car with a folding vee'd screen and a rear Auster screen, etc., and you can see just how much more imposing you can make a body by incorporating creative design into the screen work and not just considerations to function. When you arrive at the screen stage of a body build, you will have to overlap with the design of the folding top also, as in the majority of cases, the folding top will mount on the screen posts, and also in such cases where both items are independent of each other, but both designs must work together.

Once you have decided on the overall design, patterns must be made for all of the items to be cast, usually in brass or gunmetal bronze. Most of my patterns I will shape from any close-grained softwood or mahogany. Where there are shapes or features, this choice of wood will allow you to shape and carve with relative ease. But really any medium that you are happy with and can work well will do. Eventually you will have screen posts, mounts, folding mechanisms all mocked up as rough patterns. The next process is to give these patterns a good finish and smooth out all the imperfections. I would usually do this by repeated coats of a high solids, spray polyester base filler undercoat. This surface can then be sanded and prepared. Don't forget that what you see is exactly what you will get back from the foundry.

Silver Ghost Brass Windscreen

My preference for the next step is to make a high density silicone rubber mould of each pattern. When the mould has cured, I will cast an epoxy resin casting of each piece. You will then have a really tough pattern of each piece to be cast. - these can also be sprayed and prepped, even lacquered. This will allow the foundry to make a high pressure mould for investment casting. The detail and quality of your castings will be second to none and will require much less work to finish. The problems of porosity, etc., that go with sand casting will also be avoided, but don't forget that when casting in gunmetal or brass, you must account for shrinkage at the rate of approximately 5%. Remember this applies in all your cast pieces back from the foundry, the manufacture of the other parts of the screen can take place, and on through to final assembly. If the finished screen is to be plated in either nickel or chrome, base metal colour problems will not arise, but if you're making a screen for an early car to be finished in polished brass, then you must consider that different brasses from bar stock, drawn or extruded channels and castings will all age and patina down to different colours of brass which will necessitate a totally different approach to a screen manufacture, even to the extent, as I have done, of milling and shaping all of the screen sections from one large billet of brass to ensure continuity of colour.

Introduction
Materials & Methods
Metals Used
Restoring a Body
Building a Body
Windscreens
Hood Frame
Panelwork
The Advantages...

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