3 ms·

>Three-cylinder engines have a tendency to rock backwards and forwards around the middle cylinder. Carmakers have come up with a number of ways to absorb the vi

by vlehto 11y ago

>Three-cylinder engines have a tendency to rock backwards and forwards around the middle cylinder. Carmakers have come up with a number of ways to absorb the vibrations and make sure such engines don’t shake, rattle and roll. I'm skeptical how effective that is. Smells like planned obsolescence. >These include more new materials, such as what the industry calls diamond-like carbon (DLC) coatings for the surfaces of moving parts. "Diamond like" sounds nice. But it's soluble to steel. I'd prefer Boron Nitride or TiN by physical vapor deposition. But if other contact surface is coated, then you might be able to use that DLC stuff. But if I recall correctly, it's wear characteristics are not that miraculous in bearings.

thenewwazoo 11y ago
> I'm skeptical how effective that is. Smells like planned obsolescence. I'm not sure why it smells like that to you. Perhaps the word "absorb" is insufficiently precise. The correct term is perhaps "counterbalance", and it's purely mechanical. Some modern parts have fluid chambers and flexible rubber components to damp oscillation, but that's not "planned obsolescence" because the parts will very likely outlast the rest of the car.
- vlehto 11y ago
  Four cylinders is inherently more balanced than three. Fatigue is the second worst killer of mechanisms, right after corrosion. Vibration causes fatigue. The best ideas to balance inherently unstable engine involve balancing axle. But even they usually are not as good as inherently balanced.
  - thenewwazoo 11y ago
    But the entire point is that they've invented a novel mechanism for counterbalancing vibrations that are unique to the three cylinder. When you do that, you reduce vibration. This reduces fatigue. It's worth noting as well that there's no such thing as "inherently balanced" when you're talking about ICEs (except perhaps the inline 6). Four-cylinders are inherently balanced in one mode (first harmonic), imbalanced in another (secondary imbalance), and exhibit torsional effects that may as well be imbalance.
    - vlehto 11y ago
      You have point there. No ICE is really balanced, there are 16(?) different vibration modes and the best boxer 6 engines can deal with maybe 4 of them. I have pretty strong gut feeling that the 1st harmonic is more important than the 15 other modes combined. This far engines with odd numbers of pistons have been exception. Until we go to single row star engines, but they got replaced pretty quickly with two row star engines. Which can take the 1st harmonic into account.

by vlehto 11y ago

thenewwazoo 11y ago

> I'm skeptical how effective that is. Smells like planned obsolescence. I'm not sure why it smells like that to you. Perhaps the word "absorb" is insufficiently precise. The correct term is perhaps "counterbalance", and it's purely mechanical. Some modern parts have fluid chambers and flexible rubber components to damp oscillation, but that's not "planned obsolescence" because the parts will very likely outlast the rest of the car.

vlehto 11y ago
Four cylinders is inherently more balanced than three. Fatigue is the second worst killer of mechanisms, right after corrosion. Vibration causes fatigue. The best ideas to balance inherently unstable engine involve balancing axle. But even they usually are not as good as inherently balanced.
- thenewwazoo 11y ago
  But the entire point is that they've invented a novel mechanism for counterbalancing vibrations that are unique to the three cylinder. When you do that, you reduce vibration. This reduces fatigue. It's worth noting as well that there's no such thing as "inherently balanced" when you're talking about ICEs (except perhaps the inline 6). Four-cylinders are inherently balanced in one mode (first harmonic), imbalanced in another (secondary imbalance), and exhibit torsional effects that may as well be imbalance.
  - vlehto 11y ago
    You have point there. No ICE is really balanced, there are 16(?) different vibration modes and the best boxer 6 engines can deal with maybe 4 of them. I have pretty strong gut feeling that the 1st harmonic is more important than the 15 other modes combined. This far engines with odd numbers of pistons have been exception. Until we go to single row star engines, but they got replaced pretty quickly with two row star engines. Which can take the 1st harmonic into account.