4 ms·
Im an automotive mechanic by trade for a chain of shops in the midwest. The point to clarify in this article I think is that cast vs billet crankshafts are alm
by nimbius 8y ago
Im an automotive mechanic by trade for a chain of shops in the midwest. The point to clarify in this article I think is that cast vs billet crankshafts are almost a pointless argument outside of classic car enthusiast communities, or race communities.
>Brady finds out that new forged cranks can be made for about $1000.
Bull shit, and I bet he knew it too. China can cost-cut some manufacturing by shifting the prices to human labor, but they cant drop the price on precision machining. Every US manufacturer I know who cuts cams or cranks is feeding billet stainless or billet high nickel into a 5 axis CNC. If its a big enough customer, they'll ship that part to another machinist to have them QC things like center-process and calculated c(pk) ratios.
>Compression dropped off, and an inspection showed that the exhaust valves were bent. Usually the only thing that can do this is putting the cam in several teeth off, something a lifelong motorhead like Steve isn’t likely to do.
Chinese manufacturing has about as much trustworthiness in it as the chinese communist party. Which is to say, im not surprised to see hidden rework on this part that caused a failure. heat-treated composite Steel is not cheap in china, so the pressure to rework is enormous. Whereas in the US we throw out NG spec pieces on the daily, an NG spec crankshaft at a thousand dollars is valuable enough to feed an entire village for the week.
>In the end, the Chinese kept all his money, he lost his business, his house, and a lot of the other things in his personal life unraveled.
speaking from experience, the chinese are just now getting around to manufacturing tooling that can withstand more than a few drops in the toolchest. high speed steel parts for example are still prone to fracture at ridiculously high rates. chinese fasteners are spot-on clones of german and american fasteners, but fail at much lower levels of force. Even the steel stamped to make bolts, cotter pins, and collars is riddled with QC variances and imperfections that can cause a part to fail in hours.
- rdtsc 8y ago> I think is that cast vs billet crankshafts are almost a pointless argument outside of classic car enthusiast communities, or race communities. It is an aviation community in this case as well. They are re-purposing a car engine. It seems the loads on the crankshaft if it is directly attached to the propeller will be quite different that what the would be in a car. With a propeller there would be a bending component (propeller acting a gyroscope) besides the twisting component, especially when say doing aerobatics, while in a car the it will be mostly a twisting component. So perhaps then cast vs billet becomes more important as one can withstand bending forces better than the other generally.
- jcims 8y agoDon't most props drive off a gearbox? Wouldn't that soak up most of the bending forces?
- sokoloff 8y agoMost (probably 99+% of them) piston airplanes are direct drive, meaning the prop hub is directly bolted to the crankshaft flange as can be seen in the last photo in the linked article. Cessna 421 is one of the common geared engine aircraft. Twin Bonanza, Navion, late Widgeons, R985s, and others also have geared engines, but they’re the vanishingly small minority of piston aircraft. Common types (Cessna 172/182/210, Beechcraft Bonanza/Baron/Skipper, Piper Cub/Warrior/Arrow/Seminole/Seneca/Apache) are all direct drive.
- jcims 8y agoCool! I had always thought they were direct drive, it makes sense to go that route. But then I started noticing gearboxes in various videos to the point where i switched my thinking.
- WalterBright 8y agoGearboxes are another source of failures in aircraft engines, so running direct drive is more reliable.
- jabl 8y ago> With a propeller there would be a bending component (propeller acting a gyroscope) besides the twisting component, especially when say doing aerobatics, while in a car the it will be mostly a twisting component. Is this a significant component? From what I've heard, a big thing with using automotive engines in aircraft is that aircraft engines spend most of their time at close to full throttle. In a car, however, average power output is probably 20% or even less of full power.
- mlevental 8y agoi used to live in Uganda and almost all of the cast metal parts for everything there is Chinese (sold by local Indians). I remember buying screws to affix solar panels to my roof and I kept torquing off the heads of the screws. I took a closer look at one of broken ones and it was hollow! I didn't investigate further but I'm pretty the screw was hollow down the entire shank length. since then I've seen pejoratively refer to Chinese steel as chinesium and I'm inclined to agree.
- ethbro 8y agoI wasn't aware one could buy screws whose heads could be manually torqued off without leverage until I did it. Now, I generally throw any fastener hardware that comes with Chinese kits out and use my own.
- ataturk 8y agoEverything you say is right, and it is morally right to not wish to support communism and the human oppression that it causes. But then you watch as Huawei inserts spy capabilities in their products and the US is right to try to ban that crap but then all these assholes in the "Get Trump" crowd support Huawei as a political move. I give up. China sucks, China has always sucked. Americans should be trying to make China better and freer and instead it is us who are getting worse and less free each passing day. It was not supposed to be like this! The 21st century is sure falling short of my expectations, it is more like a dystopian cyberpunk novel at this point.