November 2008
Now that I’ve built this website which a lot of people liked, these same people like to see an update once in a while. Now sometimes you may feel that definitely there is progress, but you just don’t have a lot to show for it. This is the case today. But, after two years, the restoration of the bulkhead plates is finished, and I’ve experimented and learned how to make bodywork joints. There is some debate on how to make these joints, but here’s how I do it.
Cutting joints
To join the body frame parts together, you need to cut some very accurate slots. The sort of thing you’ve read about in dusty old books on woodwork, but which somehow never seemed physically possible to do by hand. The secret to cutting slots for joints is to use a very sharp chisel. I’ve been fooling around with blunt chisels all my life without knowing it, untill my lady learned how to sharpen a chisel from a professional. The secret to achieving surgical blade sharpness is to use a wetstone with diamond particles. She gave me two of those for my birthday and now life is much easier.
Once you have the right kind of tools, all you need to do is to simply “remove the material you don’t need” , to quote the sculptor Rodin. Unfortunately, it is not so well known what he did when he accidentally removed some material which he did need! On a one-off job as complicated as this, it is inevitable that you’re going to make some mistakes. I have used two types of shims to correct my mistakes, as shown in the picture below of a slot in the door post.
The shim on the upper surface was cut from ash and bonded in with polyurethane glue. The surface on the left is one where I couldn’t reach to take a measurement of the gap. I used a putty-like epoxy stick as a liquid shim between the two ash parts, with cling film in between to prevent it from gluing the two parts together. It worked out very nicely and produced a perfect matching surface.
The great thing about epoxy is that its physical strength is similar to that of hard wood, it doesn’t require clamping, it fills small gaps without reducing the strength of the joint, it doesn’t shrink while drying, and finally it is 100% water resistant. There is just one snag: frequent skin contact may result in an allergy which causes your skin to strip off your hands like a glove at the slightest contact with the stuff. So beware.
The picture below shows how I spliced a bit of new wood onto the forward (left) end of the original wheel arch - using epoxy. The joint with the door post uses only wood screws, no glue, as per the original.
Wood screws
Ash body frames for the J2 were originally put together using wood screws. From left to right: an original 1933 J2 bodytub screw and two candidate replacements; a new traditional slotted screw and a Phillips type cross headed screw, both bought at the local DIY store. Of course I wanted to use new slotted screws to stay as close to the original as possible. So I took some bits of ash and played around with different pilot hole diameters and torque settings. The results are shown below:
I only managed to put one single screw in without damage to the head and the wood surface, and that’s only because I used such a big diameter pilot hole that the screw wrecked its own wood threads. So I took another close look at the modern slotted screw, and found that the threads are quite blunt compared to the original screw and the modern cross-headed screw. That means that it requires much more torque to drive it into the wood. But you can’t do that, because the steel is too soft and you ruin the slot when you try to - even if you use grease as a lubricant. Basically, these modern slotted wood screws are of a lousy quality. They should only be used in softer kinds of wood like pine.
I searched the web and found thousands of catalogue pages with various kinds of hardware, but I could find no industrial quality traditional steel wood screws of the right sizes. I phoned a friend who has been a professional furniture restorer for decades and asked him where he gets his screws from. He answered that he removes them from old scrap furniture and he knew of no source for new, good quality, traditional wood screws. That settled it for me. I’m using cross headed screws, easily available in any size and excellent qualities for very low prices in any corner of the world.
Guarantee plate restoration
This is what the guarantee plate and the body number plate looked like when I showed them to Chris van Grinsven, a silver smith in The Hague, to ask him what could be done about these:
Chris is no ordinary silver smith. Although still in his twenties, his regular line of work is the restoration of very valuable antique silverware, which often includes designing and making replacements for missing parts in period style. His workshop includes a milling machine and a lathe, which he got cheaply because one of the gears was broken. He simply cut a new gear for himself and the lathe is working fine.
Chris said he couldn’t take this on as a normal commercial job because the cost would be huge compared to the value of the plates. But he is a friend with a weakness for nice old cars and he said he’d see what he could do in his rare spare time. Two and a half years later, he came to visit us at our new home in the country. The plates were done and they looked like this:
So what did he do? He flattened out the plates by hand but stopped short of rolling them to perfect smoothness. He hard-soldered in new bits of brass to fill in the holes, and reproduced the engraving on the new bits. He had found traces of original nickle plating on the plates, so he had them freshly nickle plated. The result wasn’t quite to his liking though, and he decided to have them chrome plated instead. Finally he filled the engraving with black paint. Needless to say, I think the result is fantastic! Thank you very much Chris van Grinsven.