You got ripped off, didn't you see the side of the box? $72.50 is what you should have paid for them.
????? I'd really like to know what the metallurgists and old time racers on here have to say. Without any other knowledge, I would tend to agree with "G-son".
Magnesium as a piston material Wednesday, July 09, 2014 Tags : advanced-materials Comments The racing piston market is dominated by aluminium, as are the roadcar and motorcycle markets, although in general the alloys used in racing are quite different from those in passenger vehicles. As racing engineers we look for increased durability and damage tolerance in our pistons, so we tend to make our pistons either as forgings from high-quality wrought material or machine them directly from billets of wrought aluminium. The exceptions to aluminium pistons in racing are those steel components used notably by some successful diesel engines, and aluminium-matrix composites used by a small number of racers where the regulations allow. The reason that aluminium is so widely used is its combination of properties and its cost. However, people have looked seriously at magnesium in the past as a piston material. While they have found it wanting when compared to aluminium, it is not beyond reason to expect people to look again in the light of new racing regulations and recent developments in engine and manufacturing technologies. So when aluminium is such a well understood and relatively cheap material, why would people look towards magnesium as a possible replacement? Well, it’s a question of density – at 1800 kg per cubic metre, aluminium is 50% more dense – but the stiffness of magnesium compared to aluminium is pretty much proportional to their densities, (that is, magnesium is about two-thirds of the stiffness of aluminium). With most of the piston’s stiffness being a function of its behaviour in bending, the required increase in section thickness to achieve the same stiffness as aluminium would still leave the magnesium piston much lighter. It is true that the room-temperature strength of good wrought magnesium alloys is lower than typical aluminium piston alloys, but at higher temperatures magnesium stands up to much closer scrutiny. For example, at 250 C the tensile strength of WE43 magnesium is higher than that of 2618, which is a favoured aluminium piston alloy. With the combination of high-temperature strength, sufficient stiffness and very low density, shouldn’t magnesium be a popular piston material? The most important reason why we don’t use it is its low thermal conductivity – it has around 60% lower thermal conductivity than 2618, which means that without considerable effort put into cooling, the magnesium piston will tend to run much hotter than its aluminium counterpart. This degrades performance, as some of the heat in the piston will be rejected to the incoming fresh charge, raising its temperature and lowering volumetric efficiency in the process, although there ought to be a significant decrease in the heat rejected from the combustion process, so we could expect fuel conversion efficiency to be improved. Where a set of racing rules rewards increasing power from a given fixed engine capacity, especially with an imposed maximum engine speed, any loss in volumetric efficiency is going to hurt performance. However, where fuel efficiency is at a premium – and this is an important factor in many forms of racing – improved fuel conversion efficiency is to be highly valued. There are types of racing where engine size, engine speed and breathing capacity are free, but the instantaneous fuel flow rate and total fuel load for the race are limited. In these types of racing, where the engine is constricted in terms of performance by an upper fuel flow limit, then fuel conversion efficiency equals performance. With the fashion for regulation that rewards efficiency, the magnesium piston may yet see a new dawn. Written by Wayne Ward
Gotta love the HAMB. That's a new one on me. Tatra and many European makes around WW2 used magnesium alloys for crankcases but this is the first I've heard of pistons. Wild.
To the O/P : You said you bought them so maybe there is a non-destructive test to see what they are really made of? Back in the day (even now), there was a lot of, shall we say, prevarication when it came down to the latest racing stuff. I hope you scored big, but if they turn out to be plain old aluminum, I wouldn't be completely surprised.
It'd be interesting to find an old complete catalog from Thomas Automotive. They made Mag products for a very wide range of mills(most of which are now considered long obsolete & "WTF were they thinking"). I've heard of, but never seen - in person - the mag pistons. I've got an NOS set of rocker arms for a Stude v8. The only other guy I know of to probably make more mag stuff was Mickey Thompson. Not counting wheels here. I do believe it was the cost that kept almost everyone who wanted them, from trying them, but don't see a major downside to using them. For more piston crown cooling, simple oil jets would help alot. Not to mention the coatings we now have available. Although, IIRC, the acids in oil resulting from blowby n such, will eat (degrade) the mag before the aluminum & steel/iron. So while that wouldn't matter much for a racing engine (except while in storage between racing events) they probably wouldn't live nearly as long as the aluminum pistons in a daily driver situation. Very neat find, btw. Marcus...
You also get gas bubbles. Aluminium doesn't react at all, not quickly anyway. Oh, this test maybe shouldn't be called completely non destructive. For a few seconds, no problem, in the long run there wouldn't be any metal left...
C. John Stutzer; Wow! Thanks for the info, never knew about the Dow book, & thanks for the mag pistons pic. I've got the feeling that the Dow book is rather hard to find. Guess I'll find out soon enough... . Marcus...
Yup, no problem. Like so many auto brands, Dow is a Michigan company, one that my family has been involved with since the beginning of the 20th century. Where they originated in Midland is a geologically unique area. There are ancient brine beds thousands of feet deep that provided much of the raw material for everything from chlorine to magnesium. Dow is one of my personal favorites for companies that early on did backyard R&D, developing products for the automotive industry and every other industrial field. They don't get much glory, but they sure did a lot of the early heavy lifting.
In the "for what it is worth category": Fairly early on, after Dow had gotten magnesium production figured out, Alcoa followed suit. However, Alcoa couldn't produce it economically, and made a deal with Dow, buying all their Magnesium from them. And of course, when we say "mag" wheels, it originated because magnesium was the most suited for die-casting. You got the twin advantages of light-weight strength and the ability to produce fine details. Which is why magnesium alloys were already widely in use in the aviation industry when Halibrand got his Eureka! moment for automotive wheels.
Ted Horn was rumored to have used magnesium pistons in his Offys. I wonder if he had heard of their earlier use at Indy?
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