Machined vs. CAST crankcase 3W/DA

[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! )

[sprice50]

Sounds like Brian knows his stuff.

Mark at the end of the day get whatever has the most bling... i.e. shiny shiny shiny and it needs to come with a real nice logo for the Ultimate. So I vote 3W 170 twinspark baby!

[btomlinson]

	Quote: Originally Posted by 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)

aaahh 6061-T6511 and two flute endmill Id love to know where you can get 6.00 castings unless your buying 250k + or there made by Ching Wang Foundry, located in a tent on the side of a mountain lol

I have wonderd who machines DA's engines ? Id love to have a crack at that crankcase. IMHO the machining looks a little rushed. large stepovers on the sculpture milled areas

[btomlinson]

	Quote: Originally Posted by sprice50
	Sounds like Brian knows his stuff.

Im a second generation machinist. Im 31 and have almost 20 years of experience in CNC/manufacturing.. I ran CNC's in junior high at my fathers company. I grew up with a garage based machine shop at home..

[btomlinson]

	Quote: Originally Posted by 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! )

a mill/turn would be sweet or 5 axis vert

[btomlinson]

anyone seen those billet gassers ? I think 3M produced them..

[Surly_Schmidt]

	Quote: Originally Posted by Craven
	Ever had sex with your DA?

polish the ports?

[Highlights]

Like I said earlier, I have always been a fan of machined/cnc'd billet. Never been a fan of castings. I agree with Brian on the large step overs. I have always beleived I was just being too picky but it has always caught my eye. Having been a sports fishing guide for half my life , I have spent tens of thousands of dollars on fine cnc /milled reels from billet aluminum.

The concern was the cast cases that 3W is using. I assume that they have very high standards though . The end product looks great, and like Sprice says, I am all about the bling factor. Speaking of which, DA's ignition lead looks way sturdier than say the leads on BME or 3W. I prefer the corded lead of the DA rather than the flimsy 22guage stuff they have on the others.

Thanks again guys. Good conversation!

[shiller]

Just to throw an idea out there... The DA crank housing is all CNC billet aluminum, but the cylinders are cast pieces. What do most DA engines go back for a rebuild for? From what I have seen it seems most DA's go back for a "freshening"... I read that as low in power which 9 out of 10 times comes from poor compression due to cylinder wall/piston ring wear. So maybe DA sees it as more cost effective to cast its cylinders and just replace them for nothing. And by doing so they build up this reputation as having "incredible service". They replace cylinders and parts... because they have to to keep a stellar reputation.

So before you think I am DA bashing here and start flaming me, let me just say I own a DA-50 and a DA-150. Great reliable engines! But let me go to the automotive world for a moment here... about 15-20 years ago Honda did the same thing with their transmissions. They were cheap crap, so when they were brought in for service because some stupid part failed, Honda would replace the entire transmission as it was most cost effective... It made more sense for Honda to replace the entire tranny and get the vehicle beyond the drivetrain warranty than to replace a part or 3 that might fail again sooner. In the end Honda had a great reputation for its service. Either way the methodology works because it makes the customer happy. But for what it's worth, the engine going on my 35% will be a 3w 106 just to be different and see how it runs.

[Highlights]

Interesting angle for sure. Being a business owner my self, I know that sometimes being creative has a two part effect. very interesting!