Magnesium transmission casings
Magnesium transmission casings
(OP)
Does anyone know what the benefits of magnesium transmission casing are; structural/mechanical properties as well as cost compared to Al/Fe? Examples of applications would be helpful.





RE: Magnesium transmission casings
All new Volkswagen transmission cases are made with magnesium alloys.
You can find general information using Google (http://www.google.com) and keywords Volkswagen magnesium transmission.
You can find technical information using Scirus (http://www.scirus.com) and keywords Volkswagen magnesium transmission.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Magnesium transmission casings
There is no real benefit to Mg transmission casings. Although the metal has a lower density than aluminum, aluminum is better with respect to specific stiffness (the ratio of stiffness to density).
The downside to Mg casings are that they are more susceptible to corrosion. Magnesium also gives more problems when trying to maintain dimensional relationships with steel gears/shafts/bearings, during temperature change. Mg has a CTE about 25% greater than Al.
As far as cost, cast magnesium is not much more expensive than cast aluminum. It is a relatively plentiful element (I believe high quality Mg is extracted from dolomite).
If you wish to examine their properties more closely, you can go to the link below. The typical aluminum sand casting alloy is A356 or A357. A typical magnesium sand casting alloy would be AZ92 or ZE41.
http://www.matweb.com/index.asp?ckck=1
Good Luck.
Terry
RE: Magnesium transmission casings
There are real benefits to using magnesium alloys for transmission cases. I was imprecise in my first post - Al alloys have higher E/ρ, but transmission cases are bending critical components, and therefore the property index is either E0.5/ρ or E0.33/ρ. Mg alloys are superior under these conditions.
Automotive transmission cases are made using high pressure die casting, not sand casting. Therefore, suitable alloys are AZ91D and A380. Using Matweb for properties, one can calculate the following:
Property AZ91D A380
-------- ----- -----
E 44.8 71
ρ 1.81 2.76
E/ρ 24.75 25.72
E0.5/ρ 3.70 3.05
E0.33/ρ 1.96 1.50
Mg alloys do have larger thermal expansion, and the cost can be higher (~10%-50% depending on design, volume, etc.). Dolomite is one of the major ores from which to obtain magnesium metal.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Magnesium transmission casings
RE: Magnesium transmission casings
Regards
pat
RE: Magnesium transmission casings
Cheers
Greg Locock
RE: Magnesium transmission casings
RE: Magnesium transmission casings
To get the best from this material, please remember to design the Trans' case as Mg, not convert a current Al design. This should give a comparable cost to Al.
Good luck,
John.