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ssuds 46 minutes ago [-]
In a past life I worked on a rocket engine turbopump that spun at 160,000 RPM. It’s crazy to visualize how fast that is. The stresses in the metal are so high that we needed speciality alloys made exclusively for us. The parts are literally ripping themselves apart.
ggreer 7 minutes ago [-]
What diameter was the part that spun at that speed? Also do you have some idea of the maximum forces exerted on it? It might not be much higher (as in, less than on order of magnitude) than the peak forces exerted on some parts of a reciprocating engine. Also the turbine doesn't have to constantly switch between tension and compression, which I think should help a lot when designing a part that moves quickly.
MisterTea 26 minutes ago [-]
High speed turbo machinery is certainly an odd area -- like you said, its on the verge of ripping itself apart. The Leybold turbo molecular vacuum pump on my bench at home is rated to spin at 60,000 RPM. In the old days of metal fabrication you'd have two specialty precision machines to locate, drill and bore holes -- the jig bore and jig grinder. Once you bored a hole, if the part was heat treated there was almost certainly a need to touch up the bore from slight deformation so a jig grinder, a jig bore base with a 100,000+ RPM pneumatic grinder, is used to perform the final precision machining.
dpoloncsak 2 hours ago [-]
I'm being incredibly pedantic, but 244Hz monitors would refresh faster than the revolutions, right? Or do I misunderstand Hz
danbruc 38 minutes ago [-]
But even with 244 Hz the engine running at 9000 rpm or 150 Hz will not even give you two frames per revolution, about 221° of rotation per frame to be precise. If you want a somewhat smooth animation, say 10° per frame, you want to look for a 5400 Hz monitor.
hamdingers 7 minutes ago [-]
Your monitor refreshes a bit faster than my motorcycle. '09 Yamaha FZ6 14k redline, 240hz would be about 14,400 rpm.
zokier 2 hours ago [-]
But combustion engines go also much faster than 9000 RPM; afaik bike engines can reach 18000 RPM or more.
OGWhales 2 hours ago [-]
You’re correct, would be equivalent to 150Hz. I was curious too since my monitor is 360Hz :)
phoghed 2 hours ago [-]
Not pedantic enough because we have 500Hz monitors already. Don’t think that’s the point the author was trying to make though.
Idling at 900rpm or 15cycles per second is a tremendous waste. Somehow I always assumed it was slower.
0.9k RPM is way too fast to be the low end of a machine.
huijzer 2 hours ago [-]
Well.. as so many things in engineering: it’s a tradeoff. Mechanically, it’s also very important to let the engine warm up and cool down before and after heavy load. Primary reasons for warmup are that the oil is more fluid on higher temperatures and metal is also less fragile when 50 or so degrees above freezing. Cooldown is especially important on turbo engines as the turbo on hundreds of thousands revs per minute and high temperature needs oil to be pumped through the bearings. If you turn it off after heavy load on engines that do not keep the oil running after motor shutdown, there is a chance that oil burns and gets stuck in the bearings, degrading performance or worst case breaking the turbo.
Grombobulous 2 hours ago [-]
True, idling is wasteful, but at the same time “spinning fast” does not necessarily equate to “high energy consumption.”
The CPU fans in my computer spin at about 1000 RPM all day long but that doesn’t mean they’re consuming a lot of electricity.
34 minutes ago [-]
mschuster91 2 hours ago [-]
At idle, it doesn't take that much fuel to keep the engine alive. Idle stops are more important for noise abatement and local toxic exhaust gas emissions - a lot of exhaust gas treatment depends on the exhaust gas having a minimum amount of thermal energy.
The downsides of idle stops are, however, that they tend to put a lot of load on the engine, especially from the lack of oil pressure at the very few first strokes [1], and that the low temperature deposits all kinds of gunk in the exhaust pipework instead of transporting it outwards.
If you run an engine with idle stop, it really really is important to properly take care of the engine, including preventative maintenance and regular oil changes.
[1] That is even more of an issue in large engine blocks, hence that high pitched noise you hear from ships and locomotives for a while before they start up - that is an ancilliary oil pump, priming the entire oil pipework until all air is gone and full oil pressure is present at all ports in the system.
enragedcacti 4 minutes ago [-]
> The downsides of idle stops are, however, that they tend to put a lot of load on the engine
While I don't doubt that it seems like this is essentially a solved issue. Priuses are some of the most reliable, long-lasting cars out there despite experiencing considerably more start-stop cycles than a traditional ICE with start-stop would.
SoftTalker 31 minutes ago [-]
Yeah I disable idle stop on my cars, for exactly those reasons. If I'm going to be stopped for more than a minute or two, I'll let the engine idle so that temperatures can normalize, then shut it off manually.
Back when turbochargers became common on passenger cars, there was even advice to be sure you let the engine idle for a minute or two before shutting it off, so that the turbocharger could cool. Otherwise the oil in the turbocharger would get baked into a goo. Modern synthetic oils, and turbochargers, handle this better today but I still like to give any hot spots a chance to cool off.
dragontamer 52 minutes ago [-]
Unless you have a hybrid vehicle, like the Prius. Which basically switches to electric during idle stops and barely has any downside.
bob1029 29 minutes ago [-]
Idle stop == cam death rattle.
The externalized consequences of drivetrains failing faster (or being abandoned because they give the perception they might) easily offsets whatever gains are achieved with this nanny tech.
Auto start/stop is a great example of weirdly aggressive nerds failing to explore nuance, which is found everywhere.
MisterTea 19 minutes ago [-]
In the early days it also killed starter motors as they weren't rated for that duty cycle.
I feel these kinds tech are more symbolic than functional and exist to simply check off boxes to obtain environmental ratings. I would even guess the environmental ratings are also short sighted and exist as symbolic gestures of environmentalism. Basically, environmentalism performance theater.
margalabargala 17 minutes ago [-]
> easily offsets whatever gains are achieved with this nanny tech
That's a matter of opinion, which may not be shared by anyone living near places that have seen decreases in noise and air pollution due to idle stop.
Idling at 900rpm or 15cycles per second is a tremendous waste. Somehow I always assumed it was slower.
0.9k RPM is way too fast to be the low end of a machine.
The CPU fans in my computer spin at about 1000 RPM all day long but that doesn’t mean they’re consuming a lot of electricity.
The downsides of idle stops are, however, that they tend to put a lot of load on the engine, especially from the lack of oil pressure at the very few first strokes [1], and that the low temperature deposits all kinds of gunk in the exhaust pipework instead of transporting it outwards.
If you run an engine with idle stop, it really really is important to properly take care of the engine, including preventative maintenance and regular oil changes.
[1] That is even more of an issue in large engine blocks, hence that high pitched noise you hear from ships and locomotives for a while before they start up - that is an ancilliary oil pump, priming the entire oil pipework until all air is gone and full oil pressure is present at all ports in the system.
While I don't doubt that it seems like this is essentially a solved issue. Priuses are some of the most reliable, long-lasting cars out there despite experiencing considerably more start-stop cycles than a traditional ICE with start-stop would.
Back when turbochargers became common on passenger cars, there was even advice to be sure you let the engine idle for a minute or two before shutting it off, so that the turbocharger could cool. Otherwise the oil in the turbocharger would get baked into a goo. Modern synthetic oils, and turbochargers, handle this better today but I still like to give any hot spots a chance to cool off.
The externalized consequences of drivetrains failing faster (or being abandoned because they give the perception they might) easily offsets whatever gains are achieved with this nanny tech.
Auto start/stop is a great example of weirdly aggressive nerds failing to explore nuance, which is found everywhere.
I feel these kinds tech are more symbolic than functional and exist to simply check off boxes to obtain environmental ratings. I would even guess the environmental ratings are also short sighted and exist as symbolic gestures of environmentalism. Basically, environmentalism performance theater.
That's a matter of opinion, which may not be shared by anyone living near places that have seen decreases in noise and air pollution due to idle stop.