TheSamba.com :: View topic

Mon Dec 20, 2004 7:02 am

Does anyone know why the engineers at VW stuck with magnesium alloy crankcases until the "pancake" engines? Why not the apparently more resilient and tougher aluminum alloy from the start? :?

Mon Dec 20, 2004 7:11 am

Magnesium is lighter.

Mon Dec 20, 2004 8:36 am

Cause they were all pyros at heart.

That and they wanted it to be bio-degradable... you know, turn into a lump of corroded green slime and eventually just flamable powder!

:wink:

Mon Dec 20, 2004 9:25 am

cost, machinability, advancements in metallurgy, availability of bauxite ore, availability of magnesium ore, COST.

Mon Dec 20, 2004 9:34 am

Magnesium is less dense that Aluminum and because they are side by side on the periodic table they have very similar properties which makes them interchangable. To achieve Hitler's mpg requirements and help keep the front wheels on the ground, the rear of the beetle was made as light as possible but there was another consideration: convenience.

Magnesium wasn't just lighter it was abundant in Germany. During the war, the Germans were greatly materials constrained and while they could control 100% of magnesium production, Aluminum was heavily imported and recycled.

The foundry built to supply Magnesium for Wolfsburg was brought online quickly for the war production of kubelwagens, etc and since the beetle was a kubelwagen in disguise nothing was changed after the war ended.

Mon Dec 20, 2004 9:37 am

Cool!
On top of that I guess that on those days the aluminium would be reserved for the luftwaffe planes, much more sensitive to weight than cars.

Mon Dec 20, 2004 12:40 pm

Thanks, all. :)

Mon Dec 20, 2004 2:22 pm

ain't nothin' hotter than a magnesium fire in these parts! Not recommended for roasting hot dogs.

Thu Dec 23, 2004 3:31 pm

All vws used alluminum cases until mid 1950...so the WAR theories are no good. I am heavily into earlier cars and my jan `50 has an all alluminum case as well as all war time vehicles kubels ect....

Not sure of exact date as i sit here, but it was mid-late `50 when they went to the magnesium compound...my June `52 split has magnesium case.

Thu Dec 23, 2004 5:10 pm

bastardbus wrote: All vws used alluminum cases until mid 1950...so the WAR theories are no good. I am heavily into earlier cars and my jan `50 has an all alluminum case as well as all war time vehicles kubels ect....
You are correct in the details but everything I said is still correct if not misinterpreted. The foundary that eventually produced the Hydro alloy cases in Kassel was originally going to use Magnesium and eventually did. Kubelwagens used Aluminum cases and nothing was changed after the war, hence the short run of Aluminum cases.

I don't know why Aluminum was used for such a short period of time but two facts are clear: when the beetle was conceived Reimspiess, the engine designer, intended to use Magnesium. Back in that era the time required to cast and set Magnesium was much less than Aluminum and production numbers required the switch. This is the answer to the original post and was as true before the war as it was afterwards. Kubelwagen production was very limited by comparison.

Quote: Not sure of exact date as i sit here, but it was mid-late `50 when they went to the magnesium compound...my June `52 split has magnesium case.
Early in 1951 before March.

Thu Dec 23, 2004 5:39 pm

I've read that mag cased engines run a little cooler than aluminum also. I don't know if vw factored that into any of its "full stein of dark beer" induced engineering?

Thu Dec 23, 2004 9:04 pm

You can count on an aluminum case T1 motor to run about 15 degrees hotter oil temps than it will with a magnesium case. Head temps are not affected by either case.

Sun Dec 26, 2004 12:18 pm

Interesting facts.
When I went to buy a new crankcase recently, I chose magnesium in spite of it's durability shortcomings.
(i.e., eventual egg shaped bearing bores and case cracking compared to aluminum. Although the later alloys may be better in all that.)
Mostly, since the producer wasn't copying an exact, tried and true, VW of Germany alumininum alloy case for an early type 2, I didn't really trust the aluminum they may be using and/or it's heat expansion rate in that physical form of case, which may or may not be a problem.
(I hope that makes sense.) It seemed a little safer to me to get the standard magnesium unless I was ordering a type 4 case.

Sun Dec 26, 2004 2:25 pm

Bumped into something entertaining yet disturbing on this topic. Save the magnesium engine cases!!

http://www.burningart.com/meico/pyro/mag.html

Here are some highlights from this pyro website:

"Where do I get Magnesium?" .....my personal favorite Volkswagen engine cases and fan manifolds....There are several parts off of old Volkswagens and Porsches that are made of a mainly magnesium alloy. It's pretty easy to convince junk yards to give you their broken or cracked engines instead of the scrappers by offering them a little more than the scrappers would. I give them ~$6.00 per engine case-both sides, or ~$2.00 for a fan manifold. Haggle. See how low they'll go. And MOST important, when you go to get them BRING VINEGAR and A FILE... Because that's how you tell if they are magnesium or just aluminum. You use the file to scratch the metal to remove the Oxide layer and expose some fresh shiny metal. You then pour some vinegar (most household vinegars work fine- I use apple) onto the exposed portion. If the metal fizzes and bubbles then it's magnesium ( or mainly magnesium anyway).
"How much should I get" At Burning Man 1996 I did a teaser fire which people really enjoyed which only used a single fan manifold and one case half. This year I did a huge fire- which involved the digging, of 7 foot deep pit- with about 20 full size engine cases. Much more than a single case becomes a real bitch if you have to put it out immediately though.
"How long does it last?"- I've found that a single Volkswagen engine block will last about an hour. Although more engines cause a critical mass effect to take place instead of simple multiplication. My huge fire at Burning Man used about 20 cases and only lasted about 8 hours.

Yikes! :shock:

Sun Dec 26, 2004 6:50 pm

Disturbing indeed. And also, what the hell is a "fan manifold"?
Self Re-edit:
Oh yeah, a type 4, duh!

Sun Dec 26, 2004 7:31 pm

I don't know, fellas. I've always understood that they were alloys and that the ration mag/alu ration differed.

Sun Dec 26, 2004 8:43 pm

Yes. Everyone is implying Magnesium or Aluminum alloys.

AS21 aka MgAl2Si1 means Magnesium alloyed with up to 2% Aluminum and 1% Silicon.
AS41 is 4%Al. AZ91 and AZ81 are other formulas that substitute Zinc for Silicon.

Aluminum cases are also alloyed and mostly made from Al. I'm not sure what the Type 4 cases were made from but one such alloy is AlSi17Cu4Mg and you can see even it includes some Magnesium (they are side by side on the periodic table as I said before.)