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September 2013 - Springs unsprung

As a change from woodwork, I've made some modest progress with chassis painting and also removing the rear springs and axle. Removing springs can be dangerous, especially if you were to follow the AC handbook instructions! With the underslung chassis, these springs are under load even when the chassis is jacked up. Worse still, the chassis underpan is very close underneath the springs. I decided that the best approach was to clamp the springs to hold them almost straight and then remove a pivot bolt.

The photo above shows one of the springs after the rear bolt was removed and the clamps released, showing about 5 inches of travel that was waiting to be released. You can also see how close the underpan is to the other spring.

Unfortunately, an issue with the rear axle bearings has turned out to be more serious than I had realised. With the ENV axle, end float is checked with both wheels off the ground, and it should be 0.005 to 0.008". Mine was over 0.030". Adjustment is by shims, but it appears that the slackness on mine is due to the bearings' inner cones not having been pressed on fully. This in turn allows the distance piece to spin freely on the axle shaft - or rather that the distance piece tends to stay still (gripped by the oil seal) when the axle rotates. Hopefully, it has not caused too much wear.

The next challenge to one's ingenuity (or lack of) is removal of the bearings without a 20 ton press to hand. Rest assured, that the website will have full write-ups in due course on mechanical over-hauls as well as chassis painting.

Sourcing and buying parts

Any amateur restorer will know that part of the challenge is dealing with suppliers of parts and materials as well as finding them in the first place. It is frustrating when some ignore repeated emails. Something less obvious to watch out for are traders who do not understand the technical items that they are selling. I've come across a few traders encouraging the mixing of screw threads (or selling one thread as another). Some acknowledge a difference in threadform flank angle, and dismiss it as trivial ("what... only 5 degrees difference? That can't be important...can it?"!!!). In fact there is more to each threadform than just the flank angle and it is not just a cosmetic exercise either - a thread is a working mechanism made to a fine tolerance. Anyone who deliberately mixes them is on a par with stuffing square pegs into round holes. Lives depends on bolted joints. Don't take any risks!

Modifying classic cars

Discussion on this topic tends to dwell on the ethics of originality, but there is a much more important point to consider. This is best explained by splitting modifications into two groups:

1) Improvements to a design shortcoming on the car.
2) Unnecessary changes after the owner/mechanic has failed to identify a simple fault (not design fault).

I've heard the SU fuel pump dismissed as "useless", by those who have rendered it useless themselves... after wrongly blaming it for what was really a fuel-line blockage! The mind boggles. Most of the parts on the AC work very well for a long period, as long as they are not mis-treated. One part of the engine that really does need improving, is the water pump. Other details of engine design also have scope for improvement, such as coolant circulation, oil circulation and filtering, and the way the engine is bolted together. Some excellent modified AC engine parts are available from AC Engine Project.

Any other improvements are likely to be accessories for creature comforts and safety, rather than design changes. If you do contemplate changes to the mechanical or structural design, then it needs in-depth research or possibly consultation with someone with the required expertise. Preferably it should be limited to changes that are already tried and tested for your model of classic.

May 2014: Axles

I finally came out of hibernation to attend to the AC's rear axle. With finances a little tight, I can't forge ahead with buying mechanic parts just yet. To add to these concerns, I learned that the bearings for the front axle are likely to cost about 1,000 UKP per set! Both sizes have ceased production, leaving old stock supplies only. Meanwhile other imperial sized parts seem to be getting even more scarce, such as U-bolts for the rear axle. As far as I know, half-shafts aren't available. The very similar shafts for the Jaguar XK120, are a different length. Moss gearbox parts have been a bit scarce for some time. Supplies of front wheel cylinders (for the early type of brakes) had been available from Land Rover specialists, but seem to have became very scarce again. Master-cylinders for all but the all-hydraulic ACs, have been unavailable for a long time.

Putting parts supply troubles to the back of my mind, I have made a start on repainting the rear axle and all its fittings and the spring fittings.

To help raise funds for the AC, I have put my old stock of BSF nuts and bolts on the market. The stock I have is large enough to finance the entire restoration, if I succeed in selling it all!

"Super Light"

If you follow a lot of my ramblings, you will know that I have a life-long passion for car design technology throughout history. That gives me a very different outlook on design competence from that of most enthusiasts, and I spot mistakes by even the better informed journalists and enthusiasts that are oft repeated. One that interests me is the so-called Superleggera body construction, meaning "super light", which is an oxymoron! "Sub light" would be a logical term, but maybe it lost something in the translation from Italian?

Assessments of this technique of body building, follow the routine of saying how good it was simply because it was new and caught on fairly widely, with many specialists and high quality marques of hand-built cars. But as is so often the case, the real reasons for its popularity, were its ease and speed of manufacture, and thus lower cost. That was an important factor when small manufacturers were coming under pressure from cheaper cars.

Yet I often come across praise for this technique claiming how very strong and light it is. And in the same article or programme, an admission that it is useless in crash protection! Really that strong, huh? I think confusion arises because steel is far stiffer than wood, and stiffness seems to get confused with strength - or at least it's wrongly assumed that something rigid must be really strong. Yet in crash resistance, you need resilience, not high stiffness. This Superleggera construction uses thin steel tubes, the bending strength of which is far inferior to a thicker (but not heavier) ash member. And the latter has exceptionally good impact resistance. Strength of wood is higher for impact loads, than for continuous loads. Wood is less likely to suffer from fatigue, and putting screws into it is less likely to cause stress-raisers than with metal.

The use of thin tubes (verses thick ash) does lend itself well to small sports cars. The light weight achieved in practice owes something to lighter chassis too, which were not necessarily very stiff, until full triangulated space frames made an appearance. Light weight in the 1950s/60s was often at the expense of strength and crash safety. It is true that the Bristol 401 is about 10% lighter than the AC 2 Litre, but I have no wish to test the strength of either of these bodies! Sadly, it is commonly assumed that wood construction was even weaker. I've just watched a TV programme of an MG TC restoration, with paranoid anxiety over how weak the wood is (mis) perceived to be!

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Website started 29th December 2006