I am losing track of the days now. The other night I went and worked on the new middle section. It’s not totally done but is close now. Today (Saturday) I went and visited Woody to borrow his guillotine to cut up welding rods. I just cut strips of aluminium so they were square section rods. About 90 lengths all up. When welding we use this as filler rod since it is the same as the metal you’re welding. When the welds are done everything is all the same material so it is really just one big piece.
The rods are wiped through a scotch pad to clean them then painted with flux. The excess flux is flashed off in a flame. The flux soaks up water from the air so if you leave the rods for a while they end up dripping wet again.
I prepared six rods at a time ready for welding.
When welding the flux gives off a bright orange flame. To counter this we use blue filtered goggles. I was actually using a full face shield with blue gel taped to it. This works great without fogging up. It’s a bit hard to photograph the difference but below you can see it when Joss was demonstrating the welding for me. I took one picture normally then another through my blue face mask. You can see how the blue cuts out the orange flame. In practice the torch flame doesn’t appear as bright as in the picture below. The camera over exposes it and makes it seem brighter.
In practice you can see everything very clearly. You need to to see what the aluminium is doing. To do the weld you heat the aluminium with the gas flame and you watch for the subtle change on the surface as it gets hot enough. The only way I can describe it is it gets a sheen or a wetness to it. Shortly after that it is ready to add the filler rod. Everything has to be done quickly or else you just melt a hole.
First though you must tack together the pieces you are welding. The skin was taken off the frame and propped up and the pieces to weld clamped together in their correct positions. First though the edges are cleaned with the scotch pad and fluxed. Then the tacks are done. These are just single spots of weld along the edges to join them. You start at one end and join that then simply pull the pieces into the right position by hand to get them to line up. After tacking you hammer the edges to make sure they line up nicely then you then go fill in between the tacks with weld.
The welding is done one little blob at a time. You hold the filler rod on the edge of where the weld will be then heat up the spot and the rod will melt into it causing a little bump of metal. The welds are a series of little bumps like this but you overlap them to keep the weld continuous. You can’t do it in one continuous go though as the metal gets too hot and will melt and you will end up blowing a big hole in the panels. So you do a spot, wait a few seconds (I found counting to 3 worked for me) with the flame off the weld then do the next little bit. You can get into a real rhythm doing this.
But you have to be careful not to get carried away. You do not want holes. Holes are bad as it would mean adding in a patch which is a lot of work. If it looks like things are going wrong you immediately move the torch away and wait for things to cool down. You can see when the metal is getting close. The changes are subtle. The metal sags and almost looks like it is crusting over. You must then immediately remove heat. Luckily I avoided any holes!
The first weld I did was the longest on the car, the front left weld (there are 9 in total to do). This took me about an hour to do as I was learning as I went. I then did the front right weld which only took 25 minutes (although it is a little shorter). It takes a lot of concentration and a steady hand too. When you get to the ends a big clamp over the very edges helps sink some of the heat. If you try to weld right to the edge without a heatsink it will get too hot and you’ll just burn a hole in the edge.
Since we use rod to feed into the weld you end up with much more metal there than needed. The weld looks lumpy as hell but then the extra material gets ground then filed off. In theory the weld should be invisible after doing this. As soon as the weld is done all the flux is scrubbed off with a scotch pad and water. It’s nasty corrosive stuff. All tools such as hammers, dollies and clamps that come into contact with it are also well cleaned after use.
Tomorrow I will tidy up these first welds then hammer the bends so the front half of the skin sits properly on the car. Then I can weld the two sides of the tail together and join them to the front.
Tonight I spent some time smoothing and adjusting the top front panel. That now fits very well and the side front pieces match it nicely. These are now ready to weld. They will be done first then the rear of the tail on the two rear side pieces. Then the two halves will be joined. Finally the top pieces of the tail will be welded on.
Tomorrow evening I will make the tail top and boot cover.
The pictures don’t really show much changing but there is a lot of fine fettling happening now. The skin as shown is not really attached to the frame. Rather the skin pieces are clamped to each other and just sitting on it. They are tacked together on the frame then taken off for welding.
Joss’s own car is coming along too. It is interesting that the main dimension of these two cars are very close to each other, only an inch or so difference in most places, but the shapes are totally different.
I went back today and finished off fixing the middle panel. All it needed was the edges rolling over, which I did after annealing them, and the peak down the middle. That was done by setting up a suitable dolly in the vice and simply pressing the panel down over it by hand to raise a peak. The panel now fits and I can now start adjusting and doing final trimming of all the panels. Will aim to weld in the weekend when I can get a full day at it.
It looks a little odd as the front of it is sticking up somewhat. This will be wrapped around the tubes eventually so sit correctly. The rear most panel needs remaking to match the curve of the body. I might make that in one large piece covering the boot opening and the tail then cut it onto two pieces later.
The peak is not a hard line, more a subtle change in the panel direction but very definitely there.
I also bought a flat bastard file which I will modify into a slap stick for when I do the final finishing on the body. I ordered it first thing this morning from Trade Tools online and it arrived at work early this afternoon. And shipping is free in NZ! Excellent service.
Well, half a day as I had errands to run for part of it.
I went to finish off the middle panel and ended up totally messing it up. The panel has so many odd stresses and tensions in it I just couldn’t get it to sit right at all. In the end, after hours of playing, I ended up rolling and wheeling it back to a flatter shape and started again. I eventually ran out of time so it remains unfinished. I will go back tomorrow after work and have another go! In the messing about we did discover that my rear most hoop (behind the boot opening) is sitting too low. But since we will wire the edges of the boot opening it isn’t actually needed. The panels define the shape, not the frame. So I will probably remove that part of the frame.
Well, I’ve been asked to expand on the english wheeling and as it happens today was spent doing just that. All day. On one panel!
I started making the last body panel, the one behind the cockpit. This is the hardest on as it is the one with the most shape and it is also the most important in terms of how the body looks. Get this one wrong and the whole car would look bad. Get it right and no one will notice it even though this is the one that defines the shape of the car.
I started by wheeling in some crown into the panel. The english wheel is all about crown. As you roll a panel between the rollers the metal stretches and you end up with a dome. To keep the dome even you have to wheel evenly and also not wheel all the way to the edges of the panel. The edges remain un-streteched so as the rest of the panel stretches it has to bulge out as there is no where else for the extra stretched metal to go. If you wheel an edge to much then it also stretches and this affects the shape of the bulge.
Rolling in crown is done holding the panel rather flat and evenly going back and forth over the panel in all directions. but it is also possible to pull up or down on the panel to give it extra stretch. Intentionally pulling the panel into the shape you want to give it a hand to move there. It is also possible to do this unintentionally too if you don’t wheel evenly or allow a large panel to droop as you roll.
The actual use the wheel is hard to describe. You get into a rhythm of rolling the panel back and forth. You rock your whole body guiding the panel back and forth though the rollers while gently holding it with your fingers. It’s quite relaxing! But you can also feel what’s happening through your fingers as you move the panel. The rollers are very sensitive. You feel every undulation in the panels as they pass through. And any little piece of gubbins that gets between the roller and panel feels like you’re rolling over huge bumps and it will leave marks all over the panel (so keep it all clean). You can adjust the pressure between the rollers too and you do need to as you roll a panel as it gets thinner when it stretches. The difference in thickness is tiny (would be interesting to try to measure it actually) but you can feel the change in the way the panel feels as you roll from a stretched part to a non stretched one.
The panel I was making today was hard since it had curve in all directions as well as a definite peak down the centre. I started rolling in an even (ish) crown. After a while I found no more was going into the panel. I kept going for a while before I realised it was because I have a bit of crown but was using a flat bottom roller.
The top roller (the bigger one) is fixed but the lower rollers come with different curves on them. Obviously as the panel gets more and more curved you have to switch to a more and more curved lower roller. Changing to a more curved roller meant I started adding shape to the panel again. When I had enough shape We put the bend in the middle. This was done by bending the panel over the curve of the slip rollers by hand. Of course bending this flattens out the panel somewhat. Using a tight radius bottom roller I was then able to roll in curve along the break line by pulling the panel down as I rolled it.
Basically it was then a matter of rolling and test fitting and more rolling of the panel. The sides were hammered over (after annealing) and since the panel tapers and curves shrinks were put into the edge to bring the panel edges around.
Any time you do anything like that though the whole shape of the panel changes. Weird stresses are set up. The panel can snap and pop and flip shape because of the tensions in it. The panel can even flip inside out as the crown pops back and forth between sides of the panel. You have to work out what’s causing the stresses and relieve them. This is very hard and takes experience and a certain amount of trying things to see what happens. Is an edge too long stopping a curve from forming properly? Then pucker and shrink the edge to allow the panel to move how it needs to. Are there hollows in the panel requiring more crown to be added. If so you have to add is carefully and evenly to avoid distorting the panel even more. You can feel what’s happening in the panel when holding and bending it by hand. You can feel if the panel is relaxed and not under tensions by how it feels to handle.
It’s very hard to describe. It’s just something you get a feel for. After a week of playing with the wheel I barely know the basics but I definitely have a better feel for it and once you start getting the feel of it it’s something you want to keep doing more of.
So, after 8 hours of wheeling I have a panel that almost fits. But it’s still not perfect and needs work. There is a lot of crown in it as well as curves and tapers.
The great thing about the wheel is it smooths everything out. To get the panel to fit we had to bash part of the metal out of the way. We did this with a hammer to crudely dent the metal out of the way of part of the frame it was rocking on. I then used the wheel to raise up the rest of the panel to match that piece then finally smoothed it all out. The more smoothing you can do with the wheel now the less you have to do with a hammer and dolly later.
I basically spent 8 hours today wheeling and fiddling with that panel and it’s still not perfect. It’s also very dirty! This was my hand at the end of the day. Just from handling the aluminium all that time.
Even after a wash in kerosene and a good scrub when I got home my hands are still filthy. You wouldn’t want to wear gloves though as you get so much feel for what the panel is doing through your fingers and the only way to really tell if a panel is smooth is to run you half flat over it to feel any hollows or peaks.
I know that’s a pretty crappy explanation of english wheeling but it’s really difficult to describe. It’s something you have to experience. And practice!
Tomorrow I will hopefully get that panel finished and trimmed to fit. Then I can start welding the panels together. The end of the tail first, then the top of the tail. Then the scuttle top to the front half of the sides. Then I can join the two halves, front and back together. In all there are 9 welds to be done by hand using oxy-acetylene gas welding. I will be practising that a lot first!