Technical Library

Article by Tim Griffin

​

It has been a while since my last article, and in that time we at CMC have enjoyed the company of a number of E-type Club members at our first-ever technical seminar.

​

I hope those who attended found it useful and enjoyable. It was our first attempt at such a venture and your feedback is always appreciated. We will look towards holding days on specific subjects if there is sufficient interest, so don’t hesitate to let the Club know your requirements.

​

Now that I have had my little ramble, we are going to look at how E-types are constructed, in the first instance the fabrication of the substructure. Using the ex-Lofty England OTS 1600 RW as our guide will also give an insight into how the early cars differed from their later counterparts.

​

We know the E-type is a semi monocoque with a stressed body shell and separate stressed engine frames, all of which were derived from the D-type.

​

You will forgive me if I now seem to be going off at a tangent, but I think it is something that needs to be said, namely to underline the importance of the structural integrity of E-types. The body tub carries the stresses of the suspension and torque from the drive train through the engine frames to eight mounting points on the front bulkhead.The stresses pass through the floor and sills to the rear, no superficial panels are load bearing and an OTS not only lacks a roof panel but inner rear wheel arches. That is unless you own a SIN.

​

The point I am making is to discourage you from patching repairs in these areas as although the car may pass a MOT, the stresses are no longer transmitted evenly throughout the monocoque. Such repairs are often the cause of cracks appearing along the sills to the bulkhead and the rear quarter panel lines, particularly on the open cars.

​

This brings me nicely onto the correct fabrication of the floors, which is the datum point for the rest of the build and therefore the first area to be fabricated and assembled.

​

When Jaguar first produced the floors for the E-type they were in two halves with a spot welded seam down the centre. On all SI and Sll two seaters the inner sills are parts of each half floor and not separate from them. This is, incidentally, a good place to look when buying an E-type as it is quite obvious when there is another layer of metal present.

​

Below is a photo of the left half of the floor which we have fabricated showing the inner sill and floor as one piece and also note the extra rib close to the gearbox tunnel. The design team at Jaguar originally wanted to put a crisscross pattern in the floor panels, similar to that of the heel boards, but the company decided against it on financial grounds.

​

The thinking was that the E-type was originally intended to be produced in low numbers and the extra rib was introduced as a compromise. However, it was discontinued after a short time as it was soon realized there were no strength issues involved. Note also the square, or as is often called, the flat cross member, which is common to all early cars.

​

There are, however, two tags just in front of this which were fastened to the original floor. They are contemporary but we do not know what they are for. We thought perhaps they were seat brackets of some description as the E-type arrived with a larger-than-average seat and we know Lofty, hence his nickname, to be a tall person. The trouble was they are on the passenger side and this car was never made in left hand drive form.

​

Another point to make, although not clearly visible on this photo, is the mounting bracket for the reartrailing arm. It is much shorter than later production

we are going to look at how E-types are constructed, in the first instance the fabrication of the substructure.

​

versions and lacks even the small extra plate that was affixed in front to early cars to prevent the tie straps for the trailing arms pulling through the floor.

​

There are also no top hat sections to the inside tops of the inner sills. This was also changed early on in production and one can only assume it was due to the sill tops becoming buckled as people got in and out of the car. There seems no other obvious reason for this modification.

​

In the photo opposite you can see the lack of top hat sections and the keen-eyed will also notice the pop-riveted wiring harness clips.

​

As our floors were to be faithful reproductions, we needed to have a set of wheels made for our swaging machine to the correct profile of the originals. It was then a matter of working out in which order the swaging would take place in relation to folding. The floor had to be oversized as the swaging would alter the size, and this had to be taken into consideration with the patterns.

​

There was also a considerable amount of shrinking to be done to finish off the swages correctly. I think I spent a day alone working all this out before even making the patterns. As I said in my last article, it was not something to be entered into lightly.

​

Here in the photo is, I presume, a pair of reproduction floor panels for a flat floor E-type. Note the incorrect swage pattern and finish at the end of the swages, also that the inner sill section is missing from the panel.

​

Again these floor panels are perfectly alright to use if you wish. But they were just not good enough for us to retain on such an important car.

​

After these floor panels were fabricated, trimmed to size and the holes positioned as per the originals, they were spot welded to the original chassis rails. These had previously been carefully removed from the floor assembly.

​

the E-type was originally intended to be produced in low numbers and the extra rib was introduced as a compromise

​

Then we can start to make some real progress of the kind you can see. The floor halves are now bolted to our body jig which ensures the correct alignment and can now be spot welded together along the centre line.

​

On these early cars Jaguar joggled this edge so that the floor was smooth on the top surface. There is a single line of spot welds along this joggle; on later cars the joggle was larger and smooth on the underside. There are two rows of spot welds with each row alternating between the other; again one assumes this was done to add strength to the shell.

​

With our two halves welded we can now add our cross member. It is worth remembering that, if you have an early car with a flat cross member, this is no longer available as a reproduction part and will need to be fabricated. This panel is also spot welded into place, apart from where it passes over the chassis rails and it has a line of MIG welds on either side. I think it would have originally been ARC welded, but if you don’t tell I won’t!

​

We can then spot weld the gearbox/transmission tunnel, which we’d carefully removed and preserved, in place. Bear in mind that you need to be accurate with your preserved, in place. Bear in mind that you need to be accurate with your measurements as your front and rear bulkheads have to fit over it and they need to be millimetre perfect.

​

When finished, we have a complete floor assembly just as Jaguar intended, ready for the front and rear bulkhead. We will start by adding the rear one, with all local repairs having been done, and for this I like to fabricate new panels using the old ones as patterns. As I mentioned earlier, I don’t like patches where they can be avoided.

​

Now we can offer the rear bulkhead to the floor assembly. This is where we hope that we have been as clever as we like to think we are, as although small adjustments can be made at this stage, it really is too late if we have made an error. Fortunately we haven’t and all goes well.

​

The original repaired rear bulkhead sits well on the floor assembly. As all is held in the correct place by the body jig, it can be welded in, again using the correct procedure and in accordance with factory practice.

​

In the next instalment we will look at the front bulkhead, which has probably the most noticeable differences to later production cars. Also we will look into fabrication of the outer panels and how to fit them.