Archived posting to the Leica Users Group, 2006/01/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Well John the note I wrote a few dozen messages ago looks redundant now! Is it the crankcase shell which is magnesium? How is it protected? With standard potassium dichromate coating a racing car magnesium gearbox casing can be corroded beyond repair within a year if in storage. Magnesium water pump casings were lasting one or two races (1000 miles or so) before being too badly corroded to reuse. We do still have magnesium pump housings on most engines, nowadays machined from solid on NC machines, but they still require a passivator in the water otherwise they would be corroded through within an hour or two running. Nowadays the life of an engine is 1200km then most of it is scrap so the short life of mag parts is no longer an issue (if you think that is bad it used to be 400km before the rules changed). Sheet magnesium was banned from use in racing cars following the death of Piers Courage in a magnesium chassis de Tomaso at a Grand Prix in the early 70s (the car was being run by Frank Williams but before my time) if I remember correctly the minimum thickness of magnesium permitted in the rules is 3mm, though I haven't looked in years. AFAIK only cheaper racing cars use magnesium for important parts any more, and then probably only the gearcasing as it is probably the cheapest lightweight case, but not very stiff or strong. I haven't designed a magnesium hub carrier since the late 70s. Frank On 14 Jan, 2006, at 01:45, John Collier wrote: > I would have to agree with both Frank and Marc. > > The magnesium VW cases are durable though they will probably > require a line bore during an overhaul: not big deal and > inexpensive too. Hamfisted people also do tend to pull the head > stud threads but that is due to improper torquing. > > That said, I wouldn't use sheet magnesium to protect anything I > actually liked. Polycarbonate is one of the best materials to use > for camera construction: no "bling" factor though. I wouldn't mind > a poly Leica. It's what's inside that counts. > > An acquaintance of mine once threw a set of VW cases into a furnace > thinking they were aluminium. Not something he ever repeated. > > John Collier > > On 13-Jan-06, at 3:51 PM, Marc James Small wrote: > >> At 07:11 AM 1/13/06 +0000, Frank Dernie wrote: >> >>> This brings me to my second point. Magnesium is >>> rubbish, just cheap and light, it corrodes immediately if not well >>> surface sealed. I am disappointed to see its use beginning to >>> grow in >>> camera shells. >> >> Frank >> >> With all respect, I dissent. I have driven more than 600,000 miles >> (960,000km) on air-cooled VW's over the years, and have overhauled >> quite a >> few of the engines. The case is magnesium and is most durable. > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information