Machined vs. CAST crankcase 3W/DA

[Highlights]

Zee man, you are absolutely correct. It was a long day yesterday and I ma not sure where my head was at.

What is your guys take on the differances between the two methods of knocking out a crankcase for many of the well known engines on the market?

I am aware of the differances. The Pros and cons. I have however seen some ugly photos of ZDZ where crankcases have suddenly blown apart. Voids often times are prevelant in cast parts. Anyone ever have any issues with 3W motors?
I generally prefer a machined part. With this being said 3W is a fine motor. Why aren't they machining?

Any thoughts?

[Highlights]

Anyone?

[Cracky]

Just to let you know, I moved this thread into the Gas Engines and Power forum.


in relation to your question. I would think that cast is a cheaper way to make them.

[Highlights]

Good work Crack man. I have gotten into the bad habit of dumping everything into the Clubhouse.

Yeah I agree with cast being cheaper for sure. Why the heck has 3W stuck with this type of manufacturing. Their engines (especially the CS series) are top shelf yet they use what is considered an inferior process of making their crancases.
Is this a poor assumption?

[Surly_Schmidt]

If done right there is nothing wrong with cast.

But it doesnt match the sexy look of a DA though.

[Craven]

Ever had sex with your DA?

[Highlights]

Craven dude, don't tell me........... the cast is a little rougher?

[Craven]

LOL.......That was for Surly Schmidt.

[Highlights]

Ah..... I see. I thought after his candid comment that maybe you were sharing a few secrets and asking if he'd actually ever tried it.


I am bulls$%^&ing of course.

Have a good one,

Highlights.

PS any comment on the crankcase itself though. You know being machined vs. cast? I am close to pushing the button on the new 3W 170TS SC.

[MikeC3D]

My thought's would be that the tolerence on moving parts would be much more precise on the machined parts versus cast. I would think that undo stress or loads on any void COULD be catostrofic, whether mach. or cast. Also I would think a machined part could be made lighter than cast in the process.

[Craven]

	Quote: Originally Posted by Highlights
	Ah..... I see. I thought after his candid comment that maybe you were sharing a few secrets and asking if he'd actually ever tried it. I am bulls$%^&ing of course. Have a good one, Highlights. PS any comment on the crankcase itself though. You know being machined vs. cast? I am close to pushing the button on the new 3W 170TS SC.

Sorry I'm an "idot" LOL

[btomlinson]

There are sever types of castings. Sand, Spin, Investment, Die etc.. Sand casting being the poorest quality. Spin castings are done by your auto wheel manufacturers and guarantee zero holes due to the centripetal force while casting..

One advantage for casting V/S machining from billet is the waste. A properly cast part of good quality should have zero pores. Once machined they will perform just as well as a billet component. The only down side castings is they are brittle and subject to crack if not properly designed

Cast parts can be machined every bit as close as a Billet part. All cast engine crankcases are machined internally

As for DA im not sure why the chose Billet over Castings. Perhaps it was the tooling cost which can easily run over 100K per component. and if you want to make a manufacturing change ,well get out your wallet. Im glad to see DA going with Billet. I think the material is 7075 Aluminum witch is a good strong Aircraft grade.


Most of your forgings are done with steel. Its common to forage crankshafts,Con rods etc..


Im outta breath...

[Highlights]

Excellent, that is what I was looking for. Thanks for your time in writing that explanation of the differances in techniques used.



Highlights.

[btomlinson]

When you cast/forge molecules of the material form to the shape cast. When you machine from billet ( which raw stock is extruded) you cut the grain

As far as some manufacturers having casting issues, the fact is you get what you pay for. Today with engineered materials,Fianite analisis companies engineer things to break ( right after the warranty runs our I might add), not last like the good ole days.. Some time they get burned buy trying to raise the bottom line

[Mithrandir]

A casting is a fast way to get very close to what you want as a final product. Today's casting technology is very good... a properly cast'd product with suitable QC methods.. (Magnaquench is one method of checking for cracks and X-rays for porosity) will result in a product almost as good as cutting/CNC'ing from billet. That is the catch... almost as good... from a structural standpoint. 2024, 7075, 6061 and 7050 are all various types of aerospace grade alu alloys that can be hardened.. (Thus the "T" rating often listed next to the alloy rating)... and machine nicely. The casting lends itself to manufacturing. A typical glow 2 stroke single cylinder motor crank case can be cast for about $6.00 and requires 3 to 4 setups on a mill.. with proper fixturing that would take all of about 9 1/2 minutes.
Casting is also more susceptable to corrosion.. particularly stress corrosion.
Generally speaking..... a CNC'd from billet crank case will be lighter then a cast case. (At the same strengths)


I should note that sometimes a casting allows for a complex shape that could be cut via CNC, but would require either a 5 axis machine or multiple setups.
A DA or 3W crank case is a simple enuff shape, it shouldn't require more then 1 or 2 setups on a lathe and 4 setups on a 3 axis mill... (Prob'ly! )