Car Restoration Summer School

Had I known I would have popped over and bought you a pint you were only 30 mins away    Still it looks you learnt a weeks worth in just one day 

Ah - I thought you'd been & gone - Weds / Thurs any good ? 

I'm in for the story too - having recently tried and failed to teach myself TiG welding, that course must be great.

I posted a link to a video a while back that I found very useful for using tinsnips properly, too. 

The course sounds very interesting. 

He's aware of Bicester, it's actually closer to where he lives than Brooklands. Apparently the schools are filling academic breaks with their own offerings rather than subletting.

Bruce expanded on the 90 degree thing today. His explanation was that regardless of the angle of the torch the arc tries to take the shortest route I.e. straight down, whereas the gas goes in the direction of the torch, and therefore potentially not fully screening the cooling weld long enough as you traverse.

Agree it will be interesting to try TIG in a more realistic setting we would recognise although he reckons only to use MIG for plug welds and even those he TIGs usually.

Sean

Day 3

Walked to site in that annoying sort of Drizzle just heavy enough to require a Jacket but temps warm such that you get just as damp from perspiration as you would if you hadn't bothered.

We started with a discussion on template creation. Bruce firmly advocates creating templates in metal, he countenanced Cardboard only as a stepping stone to a final metal version. He demonstrated a Buck he had made for an Allard rear wing and described the steps involved in fabricating it. He also showed us a WW2 aircraft drop tank replica he'd made for the Imperial War Museum I think he said, and showed another jig used to test its shape. Very much an advocate of technology he discussed the possibility of drawing the templates in CAD and having both the components for bucks/formers Laser/CNC cut but also the blanks cut in this way.

This formed a substantial part of the Day's practical. Bruce used an XK150 Door frame to lift a template for a common grot spot from where he cut out a blank and demonstrated the steps to form a repair panel. New techniques used included the use of a hole punch to stamp centre points for circular features, using a folding machine to turn straight flanges, and dressing curved flanges over a suitable radius form block with a chasing chisel. My humble contribution was thus



More welding practice, returning to our portfolio of tacked plates we now fully welded them in stages. Key to success here is speed of hand travel, the ideal result is just a hint of a crown on the cooled bead, if the bead is below the material you're moving too slowly and the weld pool is sagging. Example of my effort here, I did do a better one but didn't snap it.



We then had a demonstration of resistance spot welding, a discussion on why you can quickly get into problems with an underpowered machine, difficulties in spot welding Aluminium and ruses to get around them. We then had a demo on replicating spot welds using a MIG, and then TIG. I think most of you will be familiar with the principles using MIG, at home I had experimented and failed using TIG, the reasons quickly became apparent. Using TIG you do not drill or punch a hole. The Tungsten is withdrawn into the cup and the cup is placed directly on the surface of the clamped workpiece and on a high power setting (100A) the trigger is pulled for a short period. The result is very hard to distinguish from a resistance weld.

A couple of my peers had blown holes or had weld inclusions in their test pieces to address. A couple of approaches were shared. For minor blow throughs heating all around the hole is often enough to make the material expand and close up the gap which could then be welded. The other option is to drill the hole out, and using the hole punch a plug could be made and then peened into the hole and a pass with the torch then made it part of the wider material.

We had a discussion on MIG metallurgy, I was not aware that MIG wire is not simply mild steel but is in fact a different alloy containing a number of other metals which make it much harder than mild steel and this is why Bruce avoids MIG wherever possible as the hardness comes with the penalty that it is very hard to sand, can not be planished as easily and on a vehicle that is in reality flexing in use the weld flexes less than the surrounding panel and can over time reveal itself.

We had a brief discussion of Oxy Acetylene, Bruce's view was there are now better solutions, he explained how he used TIG to heat up seized nuts and steel stock for bending.

Final exercise of the day was annealing a sheet of Aluminium. Most Aluminium sheet is supplied half way between being fully soft and hard (stop sniggering at the back please) and forming Aluminium needs to be done on fully annealed material. Annealing is achieved by using a mahoosive blow torch and heating the sheet. We were shown to mark the area to be annealed with a marker pen, the marks fade as you approach ideal temperature and confirmation that you are at optimum temperature is achieved by wiping a matchstick over the material, if it leaves an Ash mark its hot enough.

Tomorrow we are getting into forming Aluminium, and, gulp, welding it!

Sean

No worries Chris. Catch you at some point in the future.

Day 4

No rain on my walk to site today. In our lunch break I had a walk up to the remains of the banking, absolutely astounding to think early racers were hammering round here doing 100+ a century ago, and, the circuit went from conception to completion in a matter of months! I will leave you all to reflect on how long such an undertaking would take if commenced today....

Another fact to ponder, cast your minds back to the London Olympics and in particular the Olympic Flame which was made up of 204 individual Copper Petals, each individual representing each Nation. Those Petals were made by Bruce, in fact he made 612 as he had to make three sets, one for testing, one for the main games and one for the Paralympics, each nation got to take a Petal home. I think that's a pretty awesome project to be involved with, oh and one other fact, he wasn't even approached until March 2012 with the concept. 

To the Day's activities then. You may recall we finished off the previous day by annealing a piece of Aluminium. Today we would be whacking and wheeling it in somewhat ambitious expectation that it would eventually fit this jig!



It's actually half of a half size Austin Seven Special tail. Towards the end of the day Bruce did offer the comment that it was a tough ask of novices and would be much easier done in two pieces but if it was easy everybody would be doing it. If you look at the jig all the shape is in the area of the horizontal rib, below that the metal is more or less vertical with a curve inwards and above the rib it becomes mostly flat with a degree of "crown" First step then was to draw a line on the panel indicating the line of the rib and then taking the sheet to the wooden block use the Bossing Mallet to start to get a rough shape. Obviously being Aluminium meant you go a lot steadier than with Steel. After a short bout of Hammering you get something resembling an Austin Seven Special that has had an incident on the Brooklands Banking! The lower edge develops a number of "tucks" as there is too much material for the shape its being forced to be, but we leave them as they hold the shape for us at this point. Our attention turns to the horizontal top. This is now all low, its the opposite of the side, its too short and needs to stretch. Over to the Wheel then to start that process. After a while of not seeming to be getting anywhere Bruce had me wind some more pressure on after which things started to move. Gradually the required Crown developed, it doesn't come consistently across the panel so you keep stopping, checking and working your "lows" until you get there. This process hardens Aluminium and its possible it will do so to the extent that further manipulation is not possible. In that case its back to the Blowtorch for some more annealing. 
At this point now we all had a panel that had approximately the required amount of shape our attention turned to the pointy bit of the tail. You will see on the jig the rear third is a piece of hardwood, this is a Hammerform, it's purpose is in the name, you literally Hammer the metal around it but there's a lot of movement required here so first we annealed the area to give the best chance of success, well move it slightly away from zero!
The forming is done using a Nylon Slapper, this is not a euphemism for a certain kind of lady from the 1940s but another variation on the metal whacking theme, Aluminium is easily marked so soft faced tooling is the order of the day.
After attempting to form the required shape once again the top was all over the shop so more wheel work to win the Crown back was required.
This is where we finished up. No doubt more still to be done tomorrow!



A number iof discussions in between our practical sessions again. One of my peers asked how Bruce had arrived at the shape for the piece of Aluminium he'd provided us with. We were given a short demo where Bruce draped brown paper over the jig and through a process similar to the way you would wrap it, folding and sticking down the excess paper soon had it fitting snugly, he then traced the edges of the jig and removed the paper, unstuck the folds and filled in any gaps on the traced lines and added a second line approx 20mm outside the first to allow for trimming the completed panel to size.

We also had a discussion on the various grades of Steel and Aluminium. The details are probably too boring to cover in detail but put simply both Steel and Aluminium come in many flavours and whilst there are certain types used that readily lend themselves to working, particularly in the case of Aluminium, you can't be sure what type have been used by a manufacturer. He mentioned that one model of XK Jaguar is skinned with grade that will annealing, and therefore whilst he could weld it, he could not dress out the distortion and he would generally have to wheel out an entire skin! The use of Aluminium in Jowetts was mentioned who apparently used a very specific brand called Duralamin (sp?) Which by some form of Witchcraft work hardens itself!

We discussed other metals, briefly. Bruce advised that absolutely all metal can be welded with a TIG welder, indeed its only Aluminium that requires AC, everything else, Copper, Titanium, Brass can be done with the most basic DC set, caution being needed on Brass as Zinc fumes are released which don't do you much good and the finished job looks dreadful until cleaned. He also gave a special mention to Stainless Steel, given a choice he'd weld nothing else, he finds it flows much better at lower current than even mild Steel.

One point to note on metal thicknesses, all metal thicknesses have a tolerance and a sad sign of the times is that most suppliers supply minimum in order to maximise the number of sheets they can roll from a given tonne. As an example if you order 1.0mm mild Steel you're doing well if its 0.95mm and will probably get 0.93mm which I would argue us really 0.9mm!! Order 0.9 and it will be to all intents and purposes 0.8!

That leads us nicely onto the others set of practical exercises, welding Aluminium.

First thing we covered was machine set up, the test pieces were 1.5mm and for this we were running at 80A, Aluminium is an excellent conductor so you are playing catch-up with material transferring your heat away from where you need it so you need to pump more in. Next up is gas, on Mild Steel 5LPM is sufficient, for Aluminium you need to double it. Final changes are to the Tungsten, for mild Steel we want a sharp point, for Aluminium you want a rounded tip, which the welder will pretty much provide for you as long as you remember to select AC current. The Machines we are using, being fairly sophisticated, have a number of bonus features some of which Bruce enabled to make our lives easier, these being pre, and post, gas flow. Basically the welder switches on the gas a controllable period before striking the arc and keeps it on after you release the trigger for a user selectable period. The purpose of this is that Aluminium is more reactive so we want the weld are fully inert before the arc starts to support a stable arc, and afterwards the gas prevents the hot metal oxidising.

We started with running beads on a test piece getting a feel for how fast to move etc. We then moved on to tacking and again the principle of heating the metal to expand material into the joint was applied. However it was not quite as per Mild Steel. Firstly Aluminium expands more, if you heat to close to the join you push too much in so your spacing is wider. Second difference is that your heating of the second side is a moving action, you start it and move quickly to the joint, once on the joint you slow down and briefly traversing in the direction of the joint before moving off onto the first piece as you kill the arc, its sort of a lazy S shaped action. It wasn't easy, at all, but slowly I got the idea and got my eye in. This is one of my test pieces.






And with that we left for the day, feeling like we had achieved the impossible, we'll maybe, but we haven't welded if fully yet, what could possibly go wrong?

Sean

Which reminds me of another point I forgot to share. Bruce's experience is that you can never successfully weld cracks in Aluminium panels as they fill up with impurities as they develop, the approach most likely to succeed is to cut around the crack and fit a patch, the cutting will expose uncontaminated metal which you will stand a much better chance of welding.