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« on: August 11, 2008, 11:03:26 »
I have some experience of Ace chassis flexing/body cracks and, perhaps, a cure for this phenomenon.
When restoring my Ace some years ago, I was aware of the weakness and breakage of the transverse tube at the point of the rear shock absorber upper mounting, so I simply reamed out the existing tube and then sleeved it over its full length with thick walled tubing - no problems with body cracking since. Any “pop” rivets will need to be replaced by longer ones, as the existing ones will be sheared off during the sleeving operation and the new ones will need to be longer to compensate for the combined wall thicknesses of the two tubes.
Regarding Ace main chassis flexing, this is inherent, normal and not normally a problem. Indeed, all standard Aces will have become "set" in their ways over the years with the minor permanent bending of the main 3" chassis tubes. Sometimes, there is an additional bend in the area of the engine mounting brackets, too.
I had the chassis on my car straightened out on a hydraulic press during the rebuild to redress this, but the set recurred within a few months of the car being put back on the road (probably because I’m no lightweight, myself!) - this was evidenced by the gaps closing up around the doors, as well as the bend being discernible along the length of the chassis – check yours, I would suggest. To eradicate this, I decided to sleeve each tube with a 2.75" O/D 16 swg steel tube. Within this sleeving tube, and over it's entire length, I welded a 10swg steel web vertically at about 6" pitches on upper and lower sides. I made the sleeving tube about 3ft longer than the chassis tubes so that it could be hammered fully home without fouling the rear bodywork. A steel drift is needed to fit over the end of the sleeving tube, otherwise the end of the sleeving tube will crumple under the repeated sledgehammer blows. I prepared the chassis by removing the fuel tank and also the rear caps sealing the main tubes. To remove any corrosion and welding occlusions, I cleaned out the internals of the main tubes by using oil/grease to lubricate a "mop" made of carborundum balls attached to a long shaft/tube which was turned by a slow speed electric drill. A honing type action was employed.
The greased sleeving tubes were then driven into each of the main chassis tubes in turn, keeping the welded web vertical by means of corrective torque being applied using a pair of Stilsons, or similar, during the hammering process. The sledgehammer force needed progressively increased as the sleeving tube was driven in. Despite the theoretical 0.080" clearance between the two tubes, it is not an easy task to drive one tube inside the other! I did work out the weight penalty of this mod, but I can't recall it now - but it wasn't that much, because I used a light gauge for the sleeving tube. I went down the sledgehammer route reluctantly, because drawing the sleeving tube through the chassis using stout chain or stout steel cable doesn’t work – I tried it.
I also increased the torsional stiffness of the chassis during the rebuild by using aircraft type alloys for the cockpit flooring, transmission tunnel and footwells. There is also an extra crossmember between the main chassis tubes to accomodate overdrive gearbox - I left as much of the existing and redundant crossmember in place to improve torsional stiffness. Also, I made a cradle (inverted coathanger shaped) from MS channel section to bridge the chassis just behind the gearbox bellhousing. This cradle is bolted and picks up on holes in the existing lugs (on the chassis on my car, at least) and is detachable for gearbox removal.
The above information was the subject of an article written by me and published in Action around 1993/4 or so.
When restoring my Aceca, I was compelled to use this sleeving technique again (plus collaring in certain locations) because of serious corrosion to the 3" tubes caused by the very poor storage conditions over 25 years whilst the car was left derelict. I also sleeved the transverse shock absorber mounting tube as previously described. Normally, sleeving the 3” tubes on an Aceca is unnecessary because of the thicker gauge material employed, but my car was exceptional because of the extensive corrosion throughout the chassis.
In my opinion, both cars handle much better than their standard counterparts as a result of this work. The ride is slightly harder because of the reduced longitudal and torsional bending/springing compared to unmodified cars, but I prefer it! The sleeving of the 3” chassis tubes was also carried by myself on a friend’s Ace, with equally successful results.
Some ACOC members may baulk at this technique, because it significantly reduces the flexible characteristics of the chassis, but I swear by it’s beneficial effect!
Good handling is also maintained if the rear spring is prevented from skewing/slewing out of alignment with the chassis (which in turn skews/slews both rear wheels) – but that’s another story!
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