de Dion assembly

With the rear end properly started with the install of the diff, it’s now time to crack on and get the de Dion tube assembled and fit the brake pipes. The brake pipes arrive as two shaped copper pipes which run along the de Dion tube, and which must be fitted before the tube is inserted into the chassis. Also it’s time to loosely attach the ears and calipers.

The process is fairly simple, only slightly helped by a tiny diagram in the assembly manual showing an exploded view of the ear/hub/caliper assembly. Everything went together as planned for me, apart from two bolts I could not locate in the same pack as all of the others. One email to Derek later and I was able to find them: in the misc metric pack. As usual, the guide was a little misleading here.

I found the diagrams from Andrew’s blog a great help again, reproduced below – much more than anything in the manual.  The key is using the right bolts, unsurprisingly.

With the ears and calipers loosely fitted, the way in which the brakes operate became obvious. I’d expected the caliper to be fixed (especially as it is connected with a rigid pipe) but it is the bracket holding the pads which is bolted to the ears. The caliper body itself moves. I found a decent explanation for the uninitiated like me at Alcester Racing Sevens web page: it’s an oldie but goodie.

Fitting the pipes gave me an initial worry – I could not see the holes that are pre-drilled for the rivets and there are strict instructions in the guide not to drill others. After a few seconds of searching and wondering where all the Dinitrol on my hands was coming from, it dawned on me: the waxy stuff had filled the holes when I’d sprayed it on the inside of the tube about a month previously. I also needed to run a drill through the holes to widen them slightly for the rivets, but nothing of any real consequence.

Riveting the pipe was a 30 second job in the end. I’m now an experienced riveter (!) so I placed them in position, fiddled with the alignment of the pipes and then popped them. Job done. With hindsight, what I should have done now is bend the ends of the pipe to fit the calipers while I had unrestricted access. I didn’t though, and I’m not sure why. Caught up in the moment I suppose.

I quickly stripped the de Dion back to the pipe plus brake pipes, taped some cardboard on the rear chassis arms, and set about man-handling it into the space at the back of the car. This bit was not as easy as I thought it would be: space is tight between the diff and the chassis and the de Dion is heavy. I managed after about 5 minutes of huffing and puffing, but would shout someone in to help next time.

Next step: unwrapping the rear dampers and drive shafts before fitting. Suddenly, the box that has been the largest and heaviest from the start is empty. The build is moving on apace.


4 thoughts on “de Dion assembly

  1. Hi Rob. I have enjoyed reading your posts and the photos have been great. I am currently building a 360S with a dry sump. I am about a month behind where you seem to be in your build. I wondered whether you used PTA tape on the rear brake line connections or simply relied on the brass connectors making a good seal?
    Best regards


    • Hi Chris,
      Really glad you are enjoying the blog. No tape on any of the brake lines at all. I did a bit of a dance with the flexible connector linking to the pipe in the chassis – the number and thickness of the washers would not allow a good seal, so I ditched one washer and got a good tight connection without running the connector up to the lock nut.
      Other than that I just tightened them by feel – I’m sure it was more than the 10Nm I used up front. When I bled the brakes I had no leaks from the rear assembly at all – but some from the front calipers with their copper washers which I had tightened to 10 Nm as per the guide. I need to go back to them and centre the washer and tighten them up again before the next (3rd) bleed.

      Good luck with the rear suspension – please give me a shout if you have any other questions.

      • Hi Rob

        I am having a bit of trouble with the electrics. Derek seems to be away at present as I can’t get a response to emails or calls.
        As you will remember the manual is somewhat vague on the connections. I have four twin wire female connectors which, based on the length of the wires need to be connected on the left hand side of the engine, near the starter/alternator. I think they are redundant and relate engines with fuel injection. Second, it is not clear which terminal the live battery lead connects to. The manual says the starter but there are three terminals. I guess it’s the terminal on the solenoid that is hard wired to the starter. Finally, there are two ring connectors on medium gauge brown wiring. Applying one of them to the starter causes the dashboard to spark into life even if the key is not in the ignition. Any tips on how these two brown wines should be connected?

        Best regards

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