I posted this to the FIE Facebook page last night. For those that aren't FIE FB followers...
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Just like anyone else, we're always looking to save money. When I saw a "Quality aluminum bronze gear" advertised for $29.20, I knew it had to be too good to be true. But it was a reputable name, so I decided to try one and see what we'd get. We go through a lot of gears here on the new magneto drives that we manufacture as well as servicing customer mags and drives. We often see gears with severe wear...teeth that are wispy-thin and ready to fold over. When we're told the gears have very little time on them, we have to wonder. Cheap stuff?
When the new gear arrived, I measured it up and found dimensional quality to be fine...everything was to spec. I knew something was fishy however, when I put the known GOOD gear next to the cheap one. The color of the material was very different. Notice in the picture how the good gear on the left has a darker, reddish hue. Someone in the shop claimed one was heavier than the other so I weighed them on a scientific scale and sure enough, the cheap gear was 12 GRAMS heavier! Wow, that's a big difference for two items that are virtually identical in size and shape.
I looked into having our own gears made a year ago, and I know the special alloy aluminum-bronze used for the good gears is very expensive. The material comprised half the cost of the gear! In the end, my cost each when making 60 gears at a time was the same as buying them from our current source one at a time. I quickly put that notion out of my head.
I would normally assume the heavier weight of the cheap gear would mean more bronze than aluminum in the alloy and everyone knows bronze is harder than aluminum, right? It turns out that when bronze and aluminum are combined, all sorts of magic happens and the resulting alloy is much harder than either by itself. I submitted both gears to a Rockwell hardness test and was shocked to find the cheap gear 49 Rockwell points SOFTER than the known good gear. Wow: FORTY-NINE! Obviously, the cheap gears are an inferior grade of material (an alloy of butter-metal?) and that's why they're cheap. They say they're aluminum-bronze, but I don't think so. Not the right stuff.
Bottom line: The only way you'll know the good ones are from their price tag. If you're not paying in the neighborhood of $50 for a distributor gear, be suspicious. Since the gear not only drives your ignition but also your oil pump, that is NOT a place to scrimp. We'll continue using the good stuff here in the shop not those cheap things. I'm using the one I bought for a paper weight here on my desk...it even holds a pen nicely
Spud
