Inside Every Small Job........

.......is a BIGGER job waiting to get out....... 

I'm getting closer to finishing some unplanned 'rectification' work. Not a big job, but something I could have done without.

Whilst re-undersealing the sills on my car, I decided to remove the long (2.17m) control rod that goes from the ride height lever in the cabin, to the height corrector in the rear. 

Tidying up the sills.

Removing the rod would give better access for cleaning, prep-ing and painting etc. More importantly, I could spray on gooey underseal and not worry about gumming-up the movement of the rod. I'm planning to rebuild the rear height corrector at some point, so would probably need to disconnect the rod anyway. It all sounded like a good idea.

I had already taken the cover off the front wheel arch to remove the piping to the engine bay and removing the control rod should have been a simple matter of unscrewing the rear end joint, then sliding the rod out of the sill through the front wheel arch.....

Rod at the bottom, slides through hole at the top...

First things first. The rear end of the rod is threaded (to make it adjustable for length) and fits into an articulated knuckle that operates a secondary height corrector rod. Although the area around the height corrector in the rear wheel arch wasn't rusty (due to some prudent use of Waxoyl back in the early 90s), the tip of the control rod was brown and slightly crusty. Okay - it was rusty. 

Rear height corrector. With disconnected rod in bottom corner

With the front linkage already disconnected, I removed the split pin to separate the second control rod at the rear height corrector and expected the threaded end piece on the long rod to then simply unscrew........It wouldn't budge. I tried penetrating oil - no luck. Unfortunately that bulbous end piece prevents the rod being withdrawn - so having committed to removing the rod (well - i'd taken the pin out already, hadn't I), it had to come off. 

There was no room to apply heat to the end piece in situ, for fear of melting or damaging something else. So I went down the caveman route and applied mole grips - to both the rod and the end piece. Sure enough, I felt some rotation! I gave it a slight wiggle and tried again. More rotation! Shortly before the end effortlessly snapped off.........

I was in shock. I sat for several seconds holding the two broken pieces as they were for several seconds, with a sad, cavernous air gap between them. How had I got to this point? HOW HAD I LET THIS HAPPEN?!? 

A problem I didn't want

I pulled out the (now) 2.16m piece of rod through the hole in the front wheel arch and inspected it. The vast majority of it that followed the line of the sill was absolutely perfect. Only the last 10cm that sat in the rear wheel arch were corroded. Of those 10cm, approximately 1cm was now snapped off and sitting in the knuckle. That would have to come out. 

Now losing 1cm off the end of a 2.17m rod doesn't sound like a disaster. It's true, I might have been able to simply have a shorter rod - though I wasn't sure whether that would then mess up the height corrector operation. 

I made some initial enquiries to find another but options seemed limited. With the rod being over 2m long, it wasn't the kind of thing that would easily go in the post from abroad.  With a dead DS sunken on it's haunches, it's not the easiest piece to remove from a hulk and so, with a fair amount of work needed to remove one from a dead DS, I didn't think anyone would be in a hurry to pull one for me either. Also, it was very likely that the end pieces might be seized anyway - just like mine. My best bet was to find one already removed and available in the UK but I had no luck. I was told the usual fix for this was just to braze on a new threaded end - and so that is the route I went down. Which meant that, as well as repairing the rod, I would need to salvage that joint.......

Luckily, there was still a few millimetres of thread still sticking out of the fitting.

Broken end stuck in joint....

I tried welding a nut to the end. But there was not really enough surface area to get a strong join and that didn't work. I tried gripping that end piece with mole grips - and it snapped straight of. Damn! The threaded end of the rod was acting like serrations on a sheet of paper and providing nice, clean tear lines - thwarting my attempts. How was I going to get it out now? 

Going backwards......

I parked that concern for the moment and went back to the rod......

I'd had no joy with brazing previously, having tried with MAP gas. Okay for household plumbing but I couldn't get the heat needed for brazing. I'd been moaning to my friend Peter Bremner ('Badabec') about this. Hearing my control rod woes, he offered to shut me up by giving me an old TIG welder 'buzz box' plus an arc brazing torch - just the job! I picked the 'buzz box' up at the D rally at Little Horwood in July. With most brazing done nowadays using gas, arc welding/ brazing is old technology. But it works. 

Ye Olde Arc Welder

The two carbon electrodes are slid together like chopsticks until they touch and 'arc'. The arc produces significant heat and light. The light is enough to give you sunburn and 'arc eye' - temporary blindness.......

Arc eye. No - really

.....and the heat is hot enough to, well, you could braze with it, for one thing. The heat from the arc is used to melt a filler rod to join the two pieces of metal you are working on. While exceptionally hot, the heat needed to melt the filler material is less than that which would melt your metal pieces.

An electric arc (photo by Achim Grochowski)

For the repair, I could have bought some steel rod and applied a thread myself. But it was just as easy to buy a pack of long M5 set screws. (As opposed to bolts that are threaded their full length, 'set screws' are threaded at the end but are unthreaded for part of their length). 

Now, because of the age of my DS, the M5 threaded parts have a 0.75mm pitch. Modern M5 bolts/ set screws will typically have a 0.8mm pitch. However, as I was going to have to tap and re-thread the fitting, I could re-tap it to 0.8mm pitch to match the set screw I was using. 

Hacking the heads off two screws, I experimented. I practiced extending the threaded section just a little. 

Adding more thread

Yep - that worked.

More thread added

How to join the set screw to the rod? It wouldn't be a strong repair to simply butt two ends together and 'grow' a blob of filler material around the join. Also, it wouldn't be fit for purpose: I would need to insert the rod through it's small guide eyes when I refitted it. For the repair to be useful, the diameter of the rod needed to stay as it was. The filler needed to be between the pieces - not around them. I used a grinding wheel and file to create a 'staggered offset' joint. (I don't know what else to call it - a step joint?). This meant that the surface area between the pieces would be much greater - giving a stronger join.

I planned to cut an offset joint in both pieces

I took out enough material from each part to enable the filler material (a silver alloy in my case) to flow between the two pieces. 

Lining up the joint. I left an air gap

After cleaning the buzz box up, I gave it a go. I needed both hands free. After carefully clamping the two pieces in position, I used the buzz box to heat the pieces until the filler rod melted when it contacted them. It didn't take long to get used to the technique. By varying the distance between the two carbon rods, you can alter the size of the flame/ heat. If i'm honest I also applied a bit of heat directly to the filler rod to encourage it to melt and flow. 

Very quickly I could see (through my welding helmet) that the joint was made. Once it had cooled a little I gently bashed off the slag with a hammer. After a bit of cleaning up and dressing with a file, it looked very respectable. The diameter was within tolerances  and the two pieces were aligned and straight.

Can you see the join?

This just might work! Could I do that a second time?

Yes. Yes I could. The real repair went just as well.

The actual control rod. Actually finished. Actually

If I'd thought about it, I'd have paid more attention to the offset and made it a snugger fit, but it was fine as it was: the rod fits through the nylon eyes that will go back in the sill, and the joint looks tidy and strong. Job done.

Before and after

I still need to drill out and re-tap the knuckle joint that's got the snapped rod piece stuck in it. Rather than do it by hand/ eye, Peter has suggested doing it on his lathe. I think that's the way to go: I can't afford to mess up the drilling and end up with an over-sized hole that the rod doesn't fit. Like they say: inside every small job.......