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It's a lot scarier when you see things going under load at speed. Lots of wiggling, twisty magic, waves. Smokey Yunick (blessed be his name) used to make see-

It's a lot scarier when you see things going under load at speed. Lots of wiggling, twisty magic, waves. Smokey Yunick (blessed be his name) used to make see-through timing covers, oil pans, valve covers + strobe light + some sort of oscilloscope setup to watch the craziness. I think I remember seeing the results for small block Chevrolet timing gears on sprint car engines as the teeth wiggled more and more with rpm. Cam went backwards and forwards. Ooof.

bob1029 5y ago
Reciprocating machines are fairly remarkable when you consider all of the components involved, forces, etc. Even more so when you think about how long a typical car engine lasts. These incredible forces are why rotary and turbine engines are substantially more reliable. Some gas turbines have only 1 moving part, and in some applications this moving part experiences zero wear due to magnetic/aerodynamic/active bearings.
- bitexploder 5y ago
  [*] more reliable in theory. Mazda RX8 and rotary engines are famous for being a bit maintenance heavy and unreliable. The amount of engineering and brain power that has gone into making common ICE engines in cars in wide deployment reliable is staggering.
  - bob1029 5y ago
    Agreed on automotive rotary. It's not in the same spirit as the gas turbine and others.
  - Dork1234 5y ago
    I've own an RX8 maintenance came down to adding oil every few fill ups, and changing spark plugs every 10k miles. If you treat the engine correctly, the will easily get to 100k miles, if you drive the engine incorrectly (run at low RPM), or run low on oil things won't last long. The car is a sports car and won't get you worry free 200,000 miles like Accord or Camry. Even the S2000 had similar oil usage. Talking to the dealers I took the car too, many of the issues with related to people who didn't warm engine up, or baby the engine below 3,000 rpms causing carbon build up.
- kingsuper20 5y ago
  Rotaries are a funny case. Look good on paper. Thermal efficiency issues. Smog. Seals. Noise control difficulties. Weird patches like bridge ports. For modern passenger cars, it's kind of like overcoming the difficulties of two-stroke. In anti-defense of 4-stroke ICE, it seems to me like we are hitting peak wacky complexity of those. Variable timing cams, turn off the cylinders, direct port injection, turbos, variable intake, complicated ECU. It's a far cry from a flathead 6 or VW flat 4. Thank God electric cars are becoming more available, although I fear increasingly complex cooling and battery management and the 1000 things a software guy is going to add to them.
  - elihu 5y ago
    > Thank God electric cars are becoming more available, although I fear increasingly complex cooling and battery management and the 1000 things a software guy is going to add to them. I'm hoping lithium iron phosphate starts to be used more in midrange vehicles; partly because they can be scaled up while sidestepping the potential resource bottlenecks around cobalt and nickel, and partly because they're very durable and cooling isn't usually much of an issue. Though heating might be an issue in the winter time (most LFP cells don't like being charged when temperatures are below freezing; heating might be necessary in winter).
  - baybal2 5y ago
    The problem with ICE industry is that nearly nothing improves much in absolute terms. If you take a look at list of ICE records, nearly all of them were made decades, and decades ago. Biggest piston engines - early 20th century Most powerful piston engines - fourties Most efficient piston engine - Jumo 204 held the record until nineties Most power to weight - eighties Uncounted billions put into engine RnD were mostly about scraping last few percents off everything above, and environmental compliance.
    - stickfigure 5y ago
      Like those distorted maps of the united states weighted by population[1], your post should be read with "environmental compliance" as the center of mass. Yet you shrug it off like a footnote. Nobody, except perhaps ship designers, cares who has the biggest piston engines. [1] http://www-personal.umich.edu/~mejn/election/2016/ http://www-personal.umich.edu/~mejn/election/2016/
Syonyk 5y ago
> Smokey Yunick Oh, man. I'm not a huge NASCAR fan, but that guy. That guy. He was an absolute master of "But the rules didn't say I couldn't..." and probably is responsible for half the thickness of the modern rulebook on his own! "What? The fuel tank capacity can't have an inflated basketball in it that springs a leak during the race, leaving us with more fuel capacity?" "What? The fuel lines have to be a short path between the tank and engine? Now, look, nowhere in this here book does it say I can't stuff the frame rails with a couple hundred feet of spiraled fuel line. It gets an extra gallon or two in the car? Really? Huh..." "Nowhere in the book does it say the bodywork has to actually match the size or positioning of the stock car the race car is based on. I can't help it if nobody else has totally redone the bodywork to improve aerodynamics... oh, OK, you're bringing cardboard templates next season, got it, that trick is done." The guy was an absolute master of "creative advantages that weren't actually illegal at the time they were used."
- jborichevskiy 5y ago
  > "What? The fuel tank capacity can't have an inflated basketball in it that springs a leak during the race, leaving us with more fuel capacity?" Pardon my ignorance- what is the motivation for temporarily reducing the fuel capacity in this example? And why was it disallowed?
  - BrentOzar 5y ago
    Your fuel tank was only allowed to hold a certain amount of fuel because if you had more, you could go farther between pit stops, thereby covering more laps while the other drivers were stopped for gas. He would temporarily meet the small tank regulations during inspection, but under race conditions, the ball would burst, allowing for more space in the tank, which would get filled up with more fuel than his competitors at the first pit stop.
    - jborichevskiy 5y ago
      That makes sense, thanks. Clever!
    - 5y ago
adrianpike 5y ago
We had a see through engine w/strobe system at the uni I studied vehicle engineering at, it was really really educational to be able to adjust ignition timing and fuel mixture and see how it would change the color & shape of the flame front. Probably a ton easier to simulate it these days but at the time it was absolute magic and really helped me understand how to ear-tune an engine to at least good enough to get on a dyno.
towndrunk 5y ago
You can get clear valve covers for some BMW motorcycles now. https://www.youtube.com/watch?v=BE71lpgJ4ng https://www.youtube.com/watch?v=BE71lpgJ4ng
gooseyard 5y ago
Kevin Cameron from Cycle World has written some of the most fantastic articles about these topics, in particular there's one that I'm struggling to find about the problems with solid camshaft mass when rpms started to get really high and resulted in cam oscillation and failure, so they were made hollow, only to then discover they got too hot, which led to making the sodium filled, and on and on. Also a couple of great ones about the struggle to find alloys for radial engine cylinders that could flex without cracking. His writing is so insightful and concise!
TheSpiceIsLife 5y ago
How much of that was really metal elasticity and how much artifacts of the camera technology used, eg. rolling shutter? I work with metals all day every day, and damn can it flex, but would have imagined the high carbon steels used in engines would he fairly still.
roflchoppa 5y ago
i just got a driveshaft balanced for my 240z, it was 2/3oz out on the front and 1/3oz out on the tail. I was thinking how much force would that generate at speed. Hopefully the vibration problem is gone.

bob1029 5y ago

Reciprocating machines are fairly remarkable when you consider all of the components involved, forces, etc. Even more so when you think about how long a typical car engine lasts. These incredible forces are why rotary and turbine engines are substantially more reliable. Some gas turbines have only 1 moving part, and in some applications this moving part experiences zero wear due to magnetic/aerodynamic/active bearings.

bitexploder 5y ago
[*] more reliable in theory. Mazda RX8 and rotary engines are famous for being a bit maintenance heavy and unreliable. The amount of engineering and brain power that has gone into making common ICE engines in cars in wide deployment reliable is staggering.
- bob1029 5y ago
  Agreed on automotive rotary. It's not in the same spirit as the gas turbine and others.
- Dork1234 5y ago
  I've own an RX8 maintenance came down to adding oil every few fill ups, and changing spark plugs every 10k miles. If you treat the engine correctly, the will easily get to 100k miles, if you drive the engine incorrectly (run at low RPM), or run low on oil things won't last long. The car is a sports car and won't get you worry free 200,000 miles like Accord or Camry. Even the S2000 had similar oil usage. Talking to the dealers I took the car too, many of the issues with related to people who didn't warm engine up, or baby the engine below 3,000 rpms causing carbon build up.
kingsuper20 5y ago
Rotaries are a funny case. Look good on paper. Thermal efficiency issues. Smog. Seals. Noise control difficulties. Weird patches like bridge ports. For modern passenger cars, it's kind of like overcoming the difficulties of two-stroke. In anti-defense of 4-stroke ICE, it seems to me like we are hitting peak wacky complexity of those. Variable timing cams, turn off the cylinders, direct port injection, turbos, variable intake, complicated ECU. It's a far cry from a flathead 6 or VW flat 4. Thank God electric cars are becoming more available, although I fear increasingly complex cooling and battery management and the 1000 things a software guy is going to add to them.
- elihu 5y ago
  > Thank God electric cars are becoming more available, although I fear increasingly complex cooling and battery management and the 1000 things a software guy is going to add to them. I'm hoping lithium iron phosphate starts to be used more in midrange vehicles; partly because they can be scaled up while sidestepping the potential resource bottlenecks around cobalt and nickel, and partly because they're very durable and cooling isn't usually much of an issue. Though heating might be an issue in the winter time (most LFP cells don't like being charged when temperatures are below freezing; heating might be necessary in winter).
- baybal2 5y ago
  The problem with ICE industry is that nearly nothing improves much in absolute terms. If you take a look at list of ICE records, nearly all of them were made decades, and decades ago. Biggest piston engines - early 20th century Most powerful piston engines - fourties Most efficient piston engine - Jumo 204 held the record until nineties Most power to weight - eighties Uncounted billions put into engine RnD were mostly about scraping last few percents off everything above, and environmental compliance.
  - stickfigure 5y ago
    Like those distorted maps of the united states weighted by population[1], your post should be read with "environmental compliance" as the center of mass. Yet you shrug it off like a footnote. Nobody, except perhaps ship designers, cares who has the biggest piston engines. [1] http://www-personal.umich.edu/~mejn/election/2016/ http://www-personal.umich.edu/~mejn/election/2016/

Syonyk 5y ago

> Smokey Yunick Oh, man. I'm not a huge NASCAR fan, but that guy. That guy. He was an absolute master of "But the rules didn't say I couldn't..." and probably is responsible for half the thickness of the modern rulebook on his own! "What? The fuel tank capacity can't have an inflated basketball in it that springs a leak during the race, leaving us with more fuel capacity?" "What? The fuel lines have to be a short path between the tank and engine? Now, look, nowhere in this here book does it say I can't stuff the frame rails with a couple hundred feet of spiraled fuel line. It gets an extra gallon or two in the car? Really? Huh..." "Nowhere in the book does it say the bodywork has to actually match the size or positioning of the stock car the race car is based on. I can't help it if nobody else has totally redone the bodywork to improve aerodynamics... oh, OK, you're bringing cardboard templates next season, got it, that trick is done." The guy was an absolute master of "creative advantages that weren't actually illegal at the time they were used."

jborichevskiy 5y ago
> "What? The fuel tank capacity can't have an inflated basketball in it that springs a leak during the race, leaving us with more fuel capacity?" Pardon my ignorance- what is the motivation for temporarily reducing the fuel capacity in this example? And why was it disallowed?
- BrentOzar 5y ago
  Your fuel tank was only allowed to hold a certain amount of fuel because if you had more, you could go farther between pit stops, thereby covering more laps while the other drivers were stopped for gas. He would temporarily meet the small tank regulations during inspection, but under race conditions, the ball would burst, allowing for more space in the tank, which would get filled up with more fuel than his competitors at the first pit stop.
  - jborichevskiy 5y ago
    That makes sense, thanks. Clever!
  - 5y ago

adrianpike 5y ago

We had a see through engine w/strobe system at the uni I studied vehicle engineering at, it was really really educational to be able to adjust ignition timing and fuel mixture and see how it would change the color & shape of the flame front. Probably a ton easier to simulate it these days but at the time it was absolute magic and really helped me understand how to ear-tune an engine to at least good enough to get on a dyno.

towndrunk 5y ago

You can get clear valve covers for some BMW motorcycles now. https://www.youtube.com/watch?v=BE71lpgJ4ng https://www.youtube.com/watch?v=BE71lpgJ4ng

gooseyard 5y ago

Kevin Cameron from Cycle World has written some of the most fantastic articles about these topics, in particular there's one that I'm struggling to find about the problems with solid camshaft mass when rpms started to get really high and resulted in cam oscillation and failure, so they were made hollow, only to then discover they got too hot, which led to making the sodium filled, and on and on. Also a couple of great ones about the struggle to find alloys for radial engine cylinders that could flex without cracking. His writing is so insightful and concise!

TheSpiceIsLife 5y ago

How much of that was really metal elasticity and how much artifacts of the camera technology used, eg. rolling shutter? I work with metals all day every day, and damn can it flex, but would have imagined the high carbon steels used in engines would he fairly still.

roflchoppa 5y ago

i just got a driveshaft balanced for my 240z, it was 2/3oz out on the front and 1/3oz out on the tail. I was thinking how much force would that generate at speed. Hopefully the vibration problem is gone.