Magnesium in piston alloys
Magnesium in piston alloys
(OP)
I saw a show the other day about the inventor of the compressed air powered car. The show stated he worked for a forumla one team for a number of years as an internal engine components engineer. They said he was know for first using magnesium in piston contruction to get piston weight in these engines down to around 250 grams. Wow! Does anyone know if this was an alloy and if so what might be the ratio of magnesuim to aluminum?
-Good day
-Good day





RE: Magnesium in piston alloys
RE: Magnesium in piston alloys
-Good day
RE: Magnesium in piston alloys
RE: Magnesium in piston alloys
Magnesium alloys have been used for crankcases and gearbox housings since the air-cooled VW Beetle era.
RE: Magnesium in piston alloys
RE: Magnesium in piston alloys
Ron
RE: Magnesium in piston alloys
There was some use of AlBe alloys (AMS 7911?) for pistons in F1, due to its low density and high modulus, until it was made illegal by the FIA.
RE: Magnesium in piston alloys
-Good day
RE: Magnesium in piston alloys
You are mostly wrong. In a high speed recip piston engine, the piston/wrist pin/con rod/rod bearing loads are mostly a function of piston accelerations, not piston velocities.
Piston linear accelerations (and thus inertia loads) are a function of crank and conrod kinematics, which in turn are determined (primarily) by stroke length and rod length.
F1 engine cylinder dimensions are typically way over-square (ie. bore-to-stroke ratio > 2.0). While Cup car engines have bore-to-stroke ratios closer to square (ie. 1.2?) Both types of engines have rules that dictate displacement, no. of cylinders, bore center dimension, max. bore dimension, etc.
Rod-to-stroke ratios in an F1 engine are kept as low as possible to minimize reciprocating mass. But these short kinematic rod ratios also produce very high peak piston accelerations, even though the mean piston velocity may seem low in relation to a Cup car engine. The rules for Cup cars essentially dictate the stroke dimension and block deck height limits that may be used, so the rod lengths are set by those rules. I haven't checked the Cup rules lately, but I believe all of the crank, rod and valvetrain materials must be a "magnetic metal" (ie. steel), so titanium conrods are not legal for race engines.
RE: Magnesium in piston alloys
(stroke x 2 x rpm) /12 gives 5500 fpm for a cup engine with a 3.50 stroke @ 9500 and I have seen them turn tighter than that. For the F1 engine I am not exactly sure what the stroke is but I figured it was around 2.00" which gives 6000 fpm @ 18,000 revs.
I was mainly pointing out that not many automotive engines go beyond 6000fpm and I think that statement still stands true. As for the rod lenth in reference to rod/piston acceleration, I am well aware. Since most of the engines that I build are for race applications at local track levels (drag & circle track), I ussually opt for a long rod that is slow at top dead center and bottom dead center but runs the short rod down on the straights as I say (in the middle of the stroke). Since they both must wind up at true tdc and true bdc at the same time. I have found that rod ratios of 1.7 or better will give the motor characteristics of a long rod engine and 1.6 or less will act like a short rod motor. But I am an engine builder not an engineer so thank you for elightning me and teaching me a few thanks, that is always appreciated.
-Good day