ORIGINAL: Rcpilet
I'm no expert in metalurgy (sp?), but isn't titanium brittle? I might be wrong, but I've heard people say not to use the titanium axles because they are brittle. I would think you wouldn't want a brittle crankshaft or rod.
If titanium is brittle, then you wouldn't want to use it for prop hub bolts. Your not supposed to use stainless for prop hub bolts and firewalls because it's too brittle.
Why not make a CF crankcase with sleeve inserts where bearings must be pressed in? Or whatever? I would think a CF crankcase would be fairly light.
Most of the current magnesium cases are cast. I've seen quite a few on conversion engines. I really couldn't tell you what current production engines had magnesium cases. It's been said that a cast magnesium case is lighter than a cast aluminum case. AND it's been said that a machined aluminum case could be as light as a cast magnesium case. So, it stands to reason, with me, that a cast case is heavier than a machined case. Why not machine a case from magnesium? Wouldn't that be light? I have no idea what it would cost. I'll bet that as soon as the magnesium wholesalers figure out there is a demand for it--the price will go up.
We probably have a surplus of it on hand right now and they can't give it away, but soon as they find out they can make a buck--they'll be making 100 bucks for it instead.
Speculation...
I think that it would be neat to see someone come up with an engine thats really ahead of it's time and innovative. Something that will have all of us going [X(]
I'll gaurantee ya something right now--and I'll stand by this untill I'm either proven right or end up with egg on my face.
It's gonna be
EXPENSIVE
Titanium can have a large range of properties, depending on the specific alloy you are talking about. Should certainly be no issue to make rods from the proper alloy. The stainless issue is exactly the same, people do not know what grade of stainless they want or are getting and they use the wrong one. Some grades of stainless are among the toughest, hardest to work with metals going. But not all of them.
The CF crankcase could be done, but a well designed (that is, finite element analysis, serious test program to find weaknesses, etc.) magnesium one should be equal or very close and much easier to produce in quantity.
The use of magnesium in model aircraft engine will have NO effect at all on the world supply of a commonly used material like magnesium.
Very few people seem to realize we are dealing with dinosaurs for engines. They are air-cooled two strokes with carburators. This technology has been mature for a lot of years. Innovation now comes in small changes to porting for better/more power and clever packaging to optimize the engine for our uses.
You would be correct, any big weight savings will be very costly by the pound. More people should learn to build light airframes before worrying about saving a bit on the engine.
Mark