Nov 162013

One of the first modifications I’d decided to make was the change to an adjustable reaction plate for the torsion bars. In part the decision was due to the enormous trouble I’d had removing the torsion bars and reaction plate.

Also, even though the front suspension should only need to be set up once, if there was some settling of the suspension after the rebuild, subsequent fettling would be far easier. So I purchased an adjustable reaction plate from Rob Beere and followed Bob Skelly’s excellent installation guide.
– PDF Version

The bolt tubes on standard reaction plate are flush with the outer edges .... unlike the adjustable plateI’d planned to install the front suspension and torsion bars on two previous occasions. However, both times, progress had been thwarted due to some other fitting ‘difficulties’ that had been encountered. The first when installing the IRS and subsequently the engine.

So it shouldn’t have come as a surprise that fitting the reaction plate would be equally challenging! The first problem was the adjustable reaction plate was approximately 3-4mm wider than the original. The tubes for the bolts securing the plate to the underfloor channels protruded much further beyond the outer edges.

Rob Beere suggested using a pry bar and the need for a tight fit, which may well need hammering to ‘persuade’ it into position. If this didn’t work, the ends of the tubes could be ground down slightly to fit. No matter what I tried I couldn’t get it to fit and so had to resort to the latter.

The large Allen bolts are fitted first. Some paint repairs are now needed due to the tight fit and the need to tap the reaction plate into positionEven so, it still required hitting home with the nylon hammer. The various attempts to get the reaction plate to fit resulted in some damage to the paint work, which will need to be repaired.

Fortunately there are a number of other adjacent areas that still need to be touched up, where the chassis was attached to the support frame during painting. So these can all be tackled at the same time before the exhaust is fitted.

It was surprising to see that the new clutch slave cylinder had started to show some surface rust, even in the short time since the transmission was installed. I’ll have to treat it with some Dinitrol hard wax asap.

Bob’s instructions suggested tightening the large Allen key bolts once the upper bolts had been inserted. However I had slight alignment issues with all the mounting bolts and the torsion bar ‘ear’ brackets. Once the Allen and upper bolts were tightened, it was impossible to fit the remaining bolts and brackets.

The torsion bar 'ear' bracket and the upper & lower mounting bolts were all fitted before everything was tightened upI found it was necessary to have everything initially finger tight, which enabled a screwdriver to be inserted in bolt holes to pry the other mounting holes in the frame into alignment with those in the reaction plate.

The fitting order that worked for me was the large Allen bolts followed by the ‘ear’ brackets, the upper bolts and finally the lower pre-cut bolts.

Only once all these were in place could everything, except the bolt through the ‘ear’, be fully tightened. It is worth reiterating that:
i) the Allen bolts need to be tightened before the adjusting cam is fitted, as the nut securing the cam obstructs access to the head of the Allen bolt
ii) the ear brackets needs to be at the top of their permitted travel before tightening the lower pre-cut bolts.

Labels were added to mark the steps in the adjusting camI also followed the advice of labelling the cam steps and then painting the outer face with some clear lacquer. However I didn’t bother highlighting the edges of the steps as I thought this was a bit of overkill.

With hindsight, I think not adding the highlights was a slight mistake. It would have provided a better visual guide to ensure the step of the cam is parallel with the edge of the torsion bar ‘ear’ bracket.

It’s not a major problem, provided there’s sufficient light when setting the cams. If I were to do it again, I’d use two bright, contrasting colours to paint alternate step edges.

I’d not been looking forward to fitting the torsion bars. I hadn’t been able to dismantle them in the conventional manner, described in the various service manuals. There wasn’t even a slight hint of movement in the torsion bars despite some very hefty blows wielding a club hammer. In the end, as an act of self-preservation, I conceded defeat and removed each side of the suspension as single units.

Time for some (dubious) Maths – the torsion bar setting link
The shock aborber is replaced by a fixed length link to provide a datum point when setting the torsion bars. This should then give the correct ride height, although the adjustable reaction plate would then come into its own if it needed subsequent tweaking. The setting link for the early cars was 17 13/16″, however this had increased to 17 31/32″ for the S2 cars.

I’d obtained some replacement torsion bars at Stoneleigh but hadn’t realised at the time that almost all new torsion bars are ‘uprated’. The standard bars are 0.77″ in diameter while the replacements were 0.85″. As a result, the bars will be stiffer, so using the recommended setting link length would result in the ride height being too high …. but by how much?

A plot of Classic Jaguar's recommended setting link lengths against Torsion Bar diametersAfter some research I found that Classic Jaguar in America had produced a chart with recommended setting link lengths for various torsion bar diameters.

Unfortunately they don’t have a figure for 0.85″ bars so I thought I’d plot their recommendations in order to determine the link length required. The graph wasn’t what I was expecting, with a linear relationship between the setting link length and the torsion bar diameter.

Hmmmm! Perhaps I’m missing something as I thought the torsional stiffness or angular deflection of a solid bar was inversely proportional to the diameter to the power of 4. Still, without anything better to work from, using a linear calculation the setting link length needed was 43.1cm.

Fitting of the torsion bars
Replacing the shock absorber with the setting link provides a datum point for setting the ride heightThe calculated length of the setting link should give me roughly the correct ride height (fingers crossed etc). So I chose to set the reaction plate cam to the mid-setting ‘4’ and will be able to raise or lower the ride height if it’s not exactly right. With the setting link in place and the ‘ear’ bracket locked at setting ‘4’, the rotational positions of the front and rear splines in the suspension are fixed.

The torsion bar has a different number of splines at each end – 25 at the rear and 24 at the front. This provides a high resolution vernier adjustment, allowing the torsion bars to be set very accurately and therefore the ride height. The fitting of the torsion bar is now a matter of trial and error, rotating the bar by one rear spline at a time until the front splines are perfectly aligned with those in the wishbone.

A rotation of one rear spline is equal to 14.4 degrees while it needs 15 degrees of rotation to move on by one front spline. Another way of looking at it is when the bar is turned by one rear spline, the relative position of the front splines is altered by 0.6 degrees, in the opposite direction to the direction of rotation. The front splines will align perfectly for one of the 25 possible orientations!!

The torsion bars need to be passed rearward all the way through the 'ear' bracket. The torsion bars were protected to avoid the splines damaging the paint of the barsI had passed both splined ends of the torsion bars through their corresponding mating pieces a dozen or so times until I was satisifed it would only need three or four solid blows to hammer them home.

The torsion bar need to be passed rearward through the rear ‘ear’ mounting and then forward again until the front meets the splined hole in the lower wishbone. However the splines were still too tight a fit. It was necessary to carefully file the spline faces on the torsion bar until it only took one firm tap to fully engage the splines.

This enabled the torsion bars to be pushed forward by hand until the front was 1mm or so from the rear face of the wishbone. A tap with the hammer would then bring the bar up to the wishbone, at which point it was possible to determine if the splines were correctly aligned. I used a 12″ pointed concrete chisel for a drift, so the point could sit in the indentation at either end of the bars.

The mistakes I made were:

  • Smothering Copperslip over the front splines on both the bar and within the wishbone
  • Blindly accepting the view that it’s a matter of trial and error to find the best fit

The Copperslip did a splendid job of masking whether the splines were properly aligned and so it was all wiped off. The best time to apply it was once the correct orientation had been determined and the front splines had just engaged.

I followed the advice of adopting a methodical approach of rotating one spline at a time until an exact fit was achieved. After completing one full rotation I wasn’t convinced I was any the wiser. The correct orientation had probably been missed under the cover of Cooperslip!

It was only at this point did I sit down and work out the Maths of the relative 0.6 degree movement of the front splines for a rotation of one rear spline. A couple of minutes of thought up front would have saved several hours of grief and frustration with a club hammer! Armed with that knowledge, it was then quite easy to quickly home in on a small area of splines spanning the best fit.

As an example:

Front spline need clockwise rotation Result of rotating anti-clockwise by one rear spline Eventually an exact alignment is reached

In the left photo, gaps can clearly be seen between the splines. The front splines need to be rotated clockwise to close these gaps. The middle photo was taken after the torsion bar had be rotated anti-clockwise by one spline. The gaps have clearly been reduced.

Eventually an exact or best match is achieved. Although I found when viewed from the lower inboard (7-8 0’clock) the front spline alignment would look spot on. However when viewed from the top outboard position (1-2 O’clock), gaps would be visible.

I think this is because the angle between torsion bar and the wishbone isn’t exactly at 90 degrees. So the lower inbound splines start engaging before the top outbound splines. Hence why gaps are still visible from one view and not the other!

Finally the torsion bars were both in and I’ve now less fear of tackling them again in future.

A milestone is reached – back on 4 wheels … almost!!

 Front Suspension  Comments Off on A milestone is reached – back on 4 wheels … almost!!
Sep 042013

The issues getting the rear suspension fitted meant that there wasn’t time to fit the front suspension let alone the engine.

The front frames were removed to fit the tiny radiator support brackets. As the frame bolts pass through the front suspension mounts, these and the roll bar were refitted at the same time as the frames.

I must mention to Andy at Hutsons that it would be a good idea to fit the radiator brackets on S2 cars before bodyshells are returned to customers.

I started with the easier upper wishbones and found the castellation nuts need to be fully tightened to compress the rubber bushes. This pulls the front and rear fulcrum mounts together so the bolts holes line up.

The original camber shims had been re-plated and were fitted behind the front and rear mounts. I suspect the shimming will need to be changed when the geometry is finally set up because the new engine frames have been fitted.

At least it should be a good starting point. The rear mounts also have a strengthening plate fitted on the reverse side on the engine frame, under the nuts. One of these was missing so I suspect at some point the suspension had been dismantled and they’d forgotten to refit it.

The castellation nuts were then backed off as they should only be fully tightened once the full weight of the car is supported by the suspension to avoid damaging the rubber bushes. The wishbone pinch bolts were also not tightened as the fulcrum shaft will need to be rotated during the final setup to set the castor angle.

The upper wishbones were fairly easy to install as they simply bolt on The lower wishbones were much harder as both the front and rear mounts need slotting into the engine frame

For now the aim is to get the car back on four wheels so it can be moved around more safely. The front suspension can only be completed once the engine has been installed when the torsion bars are fitted. This will require the upper ball and steering arm joints to be separated. So at this stage, only the lower ball joint was fully tightened. Without the torsion bars the car should just settle on the shock absorber bump stops.

The moment had arrived. The lowering of the car back on to its own four wheels. Something that hadn’t happened for many, many years. The trolley jack was lowered very gently …. touch down (pats on back etc) …. then lower …. and lower …. and lower …. and so it carried on. I had to close the bonnet and control the jack from underneath but I was getting worried that the bump stops wouldn’t be reached. Do they even have bump stops?!

Will the bump stops ever be reached? ..... No! The car had to be put back onto the axle trolley.

The trolley jack finally reached it’s lowest height so I had to revert to Plan B – back on to the axle trolley until the engine and torsion bars are fitted. Ho hum …. a FAIL! I really should have just measured the compressed shock absorber length when it was off the car and then done some simple Maths. Another lesson learnt!

Building up the front suspension

 Front Suspension  Comments Off on Building up the front suspension
Aug 152013

The plating didn’t go quite to plan as I hadn’t expected (or asked!) for the parts to be yellow passivated so the final look wasn’t really what I had in mind. The photos below show the ‘oil slick’ appearance that comes from the yellow passivation. Another lesson learnt – don’t assume anything and be explicit in your requirements!

I’m sure they used it with best intentions, as it provides slightly greater protection, or it’s the default colour but I’m kicking myself now. Still a number of people have advised on painting rather than plating for a more durable finish – now I’ll have the best of both worlds!! Anyway the aim is to drive the car rather than polish it for show!

The bracket faces that are in contact with the engine frames and the fulcrum shafts were masked to avoid any clearance problems later on. All the suspension parts were then given three coats of aluminium Epoxy Mastic 121. The parts were left for a couple of days to allow the paint to fully cure and harden.

It was also time to come off the fence as I needed to decide on whether to use the standard rubber bushes or install ‘upgraded’ polyurethane ones, such as Superflex. I’d fitted polyurethane bushes on my Elise but after several years the bushes would squeak going over even the slightest road imperfection. I think this was probably largely due to the garage not applying the correct grease (if any!) when they were installed.

In the end I’ve decided to keep to the standard rubber bushes, which were fairly easy to press in the bushes using a vice and liberal amounts of washing up liquid.

Standard rubber bushes were used in the end rebuilt wishbones and uprights ready to go on Sealed for life XJ40 lower ball joints were used

I’d been toying with the idea of buying a hydraulic press since the start of the restoration but, each time I’d needed one during the rebuild, the job was farmed out. I couldn’t justify the cost of a press now, at such a late stage, and so took the front uprights, hubs and a print out of the suspension section of the manual to the local garage while I built up the wishbones.

I hadn’t felt the need to state the obvious, that the hubs have different handed threads, because they were clearly labelled ‘LH’ and ‘RH’. Sure enough, when I picked them up a couple of days later, they had put the hubs on the wrong way round! What was that about not assuming anything and being explicit in my requirements!

I thought it would be easier to sort that out once they’re on the car and set about finishing off the simple task of putting the upper and lower wishbones together.

Finally the sealed for life XJ40 lower ball joint units were fitted to the uprights. Far easier than the original set up which required shimming. The suspension parts are now all ready to be bolted on next weekend.

The plan was to install both the front and rear suspension, steering, the engine and gearbox and all the engine bay components with the aim to get the engine running. Unfortunately I’ve not managed to sort out the dreaded fuel tank yet so the testing of the engine will have to wait.

Aug 122013

The dismantling of the front suspension was by far and away the hardest part of the stripping down. I suspect it had never been apart since it left the factory and hadn’t seen much in the way of maintenance.

The only parts that could be removed were the two upper wishbones. It took some fairly heavy blows with two club hammers to get the ball joints to split it. The rest of the suspension had to be taken off the car in one piece so it could be soaked in penetrating oil for many weeks.

Front suspension had seen little maintenance Dismantling was easiest off the car Axle carrier limited access to the lower ball joint

Even after that time, it hadn’t made the slightest bit of difference and all the bushes and bolts were still refusing to come off. I tried to press out one of the shock absorber bolts that also hold the two wishbone arms together. However all I succeeded in doing was to bend the bolt!

Progress was painfully slow and often I would get to a part that wouldn’t budge no matter what I tried. So I’d put it to one side and come back to it in a week or so, with renewed vigour. Eventually, over three months later after applying everything from penetrating oil, heat, cold, fire and a lot of frustration, it had been dismantled into the individual components.

Upper ball joint is prone to wear Lower ball joints will be replaced with sealed for life ones Suspension parts ready for shot blasting

The plan was to get the upper wishbones machined to accept a modern ball joint and then shot blast the parts before re-plating them. The lower ball joints will also be replaced with more modern XJ40 sealed for life units. Nowadays most people seem to Nickel plate the suspension as the original Cadmium is no longer available. It’s generally limited to aviation components now due to the toxicity of the plating process.

I’m not a great fan of Nickel plating as I’d had my Elise suspension plated a few years ago and it hadn’t lasted very long. The main problem is that it isn’t a sacrificial coating like Cadmium and Zinc. Once the surface is damaged it corrodes from beneath. It’s also quite difficult to get rid of when it will inevitably need redoing and requires special Nickel stripping.

After a lot of research I found the best alternative to Cadmium was Zinc-Nickel. It also has the benefit of having a duller finish and so is a lot less blingy that bright Zinc.

Several others recommended just painting or powder coating, although this is somewhat frowned upon by the purists. Also a more flexible paint coating can hide stress fractures until it’s too late! I’d played around with spraying some of the zinc plated bracketry with a satin lacquer which produced the best compromise. It provided a ‘toned down’ plated look but with the added benefit of more durability. Decision made!

Not many companies do Zinc-Nickel plating and generally don’t take private work from individuals. Fortunately I was able to arrange for my parts to be Zinc-Nickel plated as a favour. However, without asking for it, they had yellow passivated them so they had an ‘oil slick’ appearance which I think would have looked awful on the car.

So to plan B – rather than adding a satin clear coat as planned, I would paint them in aluminium Epoxy Mastic 121. The combination of the plating and Epoxy paint should mean they keep their appearance for many years to come.