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What was the weight difference?
Since we now had both aluminum and steel sets, we could make a weight comparison. How much weight did the Polaris team save per sled by going to the aluminum pipes? By weighing the two 440 pipes we came up with a total weight for the two of 3.5 lbs. Weighing two of our pipes turned out to be 4 lbs. We had made our pipes out of .062-inch aluminum, and when checking the original 440 pipes, they seemed to be made of somewhat thinner gauge material but we did not want to cut them apart to check the exact thickness. For manufacturing purposes to get nicer welds and prevent the pipes from denting too easily, we chose the slightly heavier gauge.
In addition, we have the weight of the steel header pipes. The triple set came out weighing 6 lbs., and the three header pipes added another 1.5 lbs. for a total of 7.5 lbs. for the complete triple set. Weighing the triple set of steel pipes gave us 13.5 lbs., so the total weight difference was 6 lbs. The original pipes were made of slightly lighter gauge; the total set was maybe one pound lighter. Not knowing the thickness of the original steel pipes — they may have been 15 lbs. — which then would have made the total weight savings around 8 lbs. on the factory race sled. This may not sound like much, but back then that was enough to give it a try, considering that they spent more money on magnesium chaincases and maybe only saved a couple of pounds on that conversion alone.
As it turns out, the pipes were not on for many races because of the cracking issues, and as the racing went on, steel pipes proved more reliable and consistent in the tuning. The aluminum project may have worked, but that would have required more dyno work to tune them in, and probably a heavier gauge material that would have to be heat treated after welding. Is there much weight to be saved in pipes? Today, on Grand Prix motorcycles and motocross bikes, factory exhausts are built from titanium. This can easily cut weight in half, but titanium is expensive and requires to be welded in a chamber with special atmosphere. This usually makes them too expensive for privateers, but a factory may spend up to $5,000 for a set to save maybe 4-5 lbs. The Polaris aluminum pipe project turned out not to be practical, but it might have been with more development. They sure looked trick and created a lot of buzz at the time!
The fact that enthusiasts still talk about them today proves that as a marketing tool they were a great success.