SPARKLING ALLOY


This article by Stuart Elliot appeared in the December 1979 issue of the Ontario Jaguar
Those readers who are familiar with the intricacies of preparing a car for a concours need not concern themselves with reading any further into this article.
However, during the technical discussion at an earlier meeting, I did promise to write something for the newsletter on the subject of polishing the aluminum alloy as used for the carburettors on most Jaguars. So for the benefit of those who are not seasoned concours competitors I offer the following.
I should also add that while I am not even a concours competitor, nevermind being a seasoned one, I have spent a fair amount of time investigating various polishing methods as well as actually polishing.
From the number of Jaguars which I have seen over the years with a disappointingly poor lustre on the aluminum parts, I can only assume that most owners do not know what can be achieved. Properly done, aluminum alloy can be made to shine as brightly as chrome plating, but without the artifical brightness of chrome. A couple of years ago when I was in England, I was lucky enough to see the XK 150 which was the British concours champion. On the outside the car was very nice, certainly better than anything I'd seen before, but when the bonnet was opened, the effect was stunning. The carbs and other aluminum components were simply incredible. Every Jaguar owner should have seen that car if only to see what can be done.
Needless to say, before any work can be done the parts must be removed from the car, and with the carbs for example, should be taken apart.
Then it is time to introduce these parts to the one piece of equipment which I consider essential to good polishing - the buffing wheel. Buffing wheels are actually circular layers of material, usually cotton, which are assembled in various thickness and then fastened, through a hole in the centre, to the shaft of an electric motor. This motor should be at least 1/4 H.P. with a speed rating of 3000 - 3500 R.P.M. It's not necessary to become too involved with technical details, but the important thing in buffing is the surface speed of the buff. For best results the surface speed should be between 3000 and 7500 feet per minute, the higher the speed the quicker the results.
To calculate surface speed, the formula is:

       SFPM = (PI x d")/12 x R.P.M., this can be simplified to: SFPM = d"/4 x R.P.M.,

       thus a 6" dia. buff at 3200 R.P.M. will give a surface speed of 4800 SFPM.
Using this calculation, the optimum diameter of wheel can be chosen, but it will be useful to also have a small buff of approx. 2" diameter (which will probably have a low surface speed) to get into tight corners.
I generally use only two types of compound, one being a medium-coarse one of #240 grit and one for finer work or "colouring."
It is the compound which provides the cutting action, not the buff. With the wheel revolving at the correct speed, it is coated with the compound until uniformly covered. The work is then moved against the wheel with a slanting downwards stroke.
With parts which have been previously buffed, such as carburetter dash pots, it will-only be necessary to use the fine colouring compound. This will result in a very high, mirror finish. With rougher castings the coarse compound will usually be sufficient, although sometimes it is necessary to use a file or aluminum oxide paper to smooth out casting marks, etc. before using the compound. Coarse compound will give a smooth, matt finish which is then ready for the finish, "colouring" compound. I buy all my material (buffs and compound) from W. W. Wells on Birchmount Ave. It will be necessary to tell them which material you are working with.
In addition to the aluminum of the carburetter, there are numerous brass parts, which can also be polished very highly and provide a nice contrast to the aluminum.
Once the desired finish has been achieved and the parts are reassembled and on the car, the problem remains as to how to keep them looking like that.
Over the years I have tried many different metal polishes, including Brasso, Simichrome, Solvol Autosol and Nevr-Dull and they all have provided equally good results provided the aluminum hadn't become too oxidized. When it has become oxidized, it's time for the buffing wheel - although Brasso will work with a lot of effort (an awful lot).
With a little practice and the right equipment and materials anyone can make aluminum really sparkle - then maybe we'll see more cars like that English XK 150.
Sept 13, 2011 by Webmaster