Things you always wanted to know the answer to [Vol. 5]

[Brother D]

How do car makers paint cars? Do they do a run of 100 white, 100 black, 50 red? Surely it's not on a car by car basis? (Or is it)??

[h0b0]

v9 said:

stemll said:

The head forms from dissolved CO2 by a process called nucleation. To do that they need somewhere to do it. In a clean glass the only nucleation sites are either dirty bits of glass or irregularities in the surface. In a used glass there will be residue left from earlier beer so there are more nucleation sites and hence more head.

This is the right answer, though I will add that some beer glasses (I acquired some recently like this) have nucleation sites built into the inside of the glass, often on the inside of the base, maybe try one of these and report back.

If you notice scratches on the bottom of a beer glass it is to form the head.


Oddly, many people are familiar with the opposite with champagne. The first glass poured into a dry glass often bubbles over. It’s because the soap used make the glass have that “sticky” clean feel where your fingers don’t run smoothly over the glass. To avoid this, wet the inside of the glass and the water fills the nucleation sites and your champagne doesn’t bubble over. However, at events people think they are being served flat champagne if you do this.


My final year of Chemical Engineering was spent doing all the work for Frank’s phd on “foam”. Wow, that was exciting. Also, Frank lost his st when I proved an industry accepted model was completely wrong when scaled. Apparently, he wanted to prove the model and not push the boundaries of what was known. Frank tried to falsify data until he finally caved. That prick now has his name in some fancy publications that changed an industry. He omitted mine.

[Brother D]

popeyewhite said:

RizzoTheRat said:

Surely you'd need to be a in a V formation rather than line astern in order to get any benefit, or have geese got it wrong?

Geese don't slipstream, it's something to do with disturbed air from the bird in front. Can't remember.

Yeah they can get some efficiency from the wing vorticies like the airbus proposal

[Brother D]

Sway said:

President Merkin said:

I think i know that one. Lightning flashes travel at the speed of light, so practically instantaneously to a viewer but thunder at the speed of sound, so roughly 750mph & also bounces off hills, buildings etc. creating echoes & hence outlasts the lightning flash by seconds.

Ah, that makes sense - the echoes and stuff.

Last night was a little odd, lots of the thunder was a long rumble, then a big short but bloody loud single deep bang. Really didn't seem to match the flash, nor indeed would it make sense for echoes to arrive before the biggest bang!

Lightening isn't quite at the speed of light. I mean it's pretty fast

https://www.britannica.com/science/thunderstorm/Cl...

[Jader1973]

Brother D said:

How do car makers paint cars? Do they do a run of 100 white, 100 black, 50 red? Surely it's not on a car by car basis? (Or is it)??

In batches.

The bodies tend to be the same for all trim levels, so they go through weld in batches and then get painted in smaller batches. After paint they end up in a storage area before they get pulled down to the final assembly line.

Minimising down time is the key - too many colour changes slows things down.

In theory you could do final assembly in any order, but for volume production batching still works best to avoid confusion on the line, so they’d do small batches of maybe 10 of the same colour and trim at a time.

High volume car plants are a well oiled machine running just in time (at a minimum for line side parts) so the production is planned well in advance, that allows them to batch build.

[Jordie Barretts sock]

Brother D said:

Lightening isn't quite at the speed of light. I mean it's pretty fast

https://www.britannica.com/science/thunderstorm/Cl...

And not very heavy?

[RenesisEvo]

Jader1973 said:

Brother D said:

How do car makers paint cars? Do they do a run of 100 white, 100 black, 50 red? Surely it's not on a car by car basis? (Or is it)??

In batches.

The bodies tend to be the same for all trim levels, so they go through weld in batches and then get painted in smaller batches. After paint they end up in a storage area before they get pulled down to the final assembly line.

Minimising down time is the key - too many colour changes slows things down.

In theory you could do final assembly in any order, but for volume production batching still works best to avoid confusion on the line, so they’d do small batches of maybe 10 of the same colour and trim at a time.

High volume car plants are a well oiled machine running just in time (at a minimum for line side parts) so the production is planned well in advance, that allows them to batch build.

the 'painted body store' (creative name, I know) is where the bodies are drawn from to complete each order. It acts as a useful buffer too, so that any stoppages from building the bodies-in-white (often still called this even when they're painted) doesn't immediately cause final assembly to halt as well. The downside is having space to store them, even a small batch takes up a lot of space as you might imagine.

[captain_cynic]

Is there a reason we can't have "small" big engines. Why does a V8 need to be a massive 5L monster. We can make a decent 1.6L I4 that is better than a 2L 4.pot from 20 years ago... Why don't manufacturers make a 3.2L V8?

Is it just lack of demand or are there technological limitations?

[paua]

captain_cynic said:

Is there a reason we can't have "small" big engines. Why does a V8 need to be a massive 5L monster. We can make a decent 1.6L I4 that is better than a 2L 4.pot from 20 years ago... Why don't manufacturers make a 3.2L V8?

Is it just lack of demand or are there technological limitations?

Some of that Q is tax related - Ferrari used to make 3 litre v8s & v12s. In th early 80's they also made a 2.0 v8 ( 208GTS?) Tax bands influence many decisions ahead of engineering choices.
In NZ it costs the same to register (tax) a Cinquecento as a Viper, many countries tax cubes

[Fastchas]

captain_cynic said:

Is there a reason we can't have "small" big engines. Why does a V8 need to be a massive 5L monster. We can make a decent 1.6L I4 that is better than a 2L 4.pot from 20 years ago... Why don't manufacturers make a 3.2L V8?

Is it just lack of demand or are there technological limitations?

This may not 'answer' your Q, but it's a good video to watch and very explanatory.

[Jordie Barretts sock]

If only you'd linked the video!

[Rusty Old-Banger]

Fastchas said:

captain_cynic said:

Is there a reason we can't have "small" big engines. Why does a V8 need to be a massive 5L monster. We can make a decent 1.6L I4 that is better than a 2L 4.pot from 20 years ago... Why don't manufacturers make a 3.2L V8?

Is it just lack of demand or are there technological limitations?

This may not 'answer' your Q, but it's a good video to watch and very explanatory.

[Jader1973]

captain_cynic said:

Is there a reason we can't have "small" big engines. Why does a V8 need to be a massive 5L monster. We can make a decent 1.6L I4 that is better than a 2L 4.pot from 20 years ago... Why don't manufacturers make a 3.2L V8?

Is it just lack of demand or are there technological limitations?

Because there is no replacement for displacement.


Actually Buick had a 3.5 litre V8 - the story is that a Rover executive was visiting them and saw a prototype. Rover bought the design and that is why the first cars to use it became known as the P5B and P6B - B for Buick.

[captain_cynic]

Jader1973 said:

Because there is no replacement for displacement.


Actually Buick had a 3.5 litre V8 - the story is that a Rover executive was visiting them and saw a prototype. Rover bought the design and that is why the first cars to use it became known as the P5B and P6B - B for Buick.

Erm it's called a turbocharger and weve been using it to make small engines faster than big ones for decades.

American engines are terrible examples. I'm thinking more of Japanese or European engines.

I had a Honda K20 in my Integra that outpaced the Holden V6s with their 3.5L Alloytecs (and ecotecs when they finally admitted the Alloytecs were time bombs). The K20 was naturally aspirated. They were rockets when fitted with a supercharger (as in the Ariel Atom).

Also technology has improved, maybe not in the US but certainly everywhere else allowing engines to be smaller and lighter (and more reliable) whilst producing more power.

[Error_404_Username_not_found]

captain_cynic said:

Is there a reason we can't have "small" big engines. Why does a V8 need to be a massive 5L monster. We can make a decent 1.6L I4 that is better than a 2L 4.pot from 20 years ago... Why don't manufacturers make a 3.2L V8?

Is it just lack of demand or are there technological limitations?

There should be no technical reasons that small displacement engines cannot be Vee multis. It's been done often enough. But there are some considerations that are more relevant to small engines than larger ones.
For example out of balance forces will have proportionately greater influence in a small engine. 6,8 or 12 or whatever cylinders will have out of balance forces resulting from firing cycle timings that sap proportionally more power in a smaller engine that lacks the rotational inertia of a big unit.
To some extent this can be designed out by using a two (or more) plane crankshaft for example, but that is prohibitively expensive compared to a single-plane crank.
The wonderful throb and thrum music of a big Vee idling comes partly from the unequal intervals between firing strokes on a single-plane crank.
Before I retired I maintained V12 CAT (CAT 3412) diesels for a living and the sound of a pair of those bad boys idling will remain in my memory for life.

[RenesisEvo]

Error_404_Username_not_found said:

There should be no technical reasons that small displacement engines cannot be Vee multis. It's been done often enough. But there are some considerations that are more relevant to small engines than larger ones.
For example out of balance forces will have proportionately greater influence in a small engine. 6,8 or 12 or whatever cylinders will have out of balance forces resulting from firing cycle timings that sap proportionally more power in a smaller engine that lacks the rotational inertia of a big unit.
To some extent this can be designed out by using a two (or more) plane crankshaft for example, but that is prohibitively expensive compared to a single-plane crank.
The wonderful throb and thrum music of a big Vee idling comes partly from the unequal intervals between firing strokes on a single-plane crank.
Before I retired I maintained V12 CAT (CAT 3412) diesels for a living and the sound of a pair of those bad boys idling will remain in my memory for life.

A 6 or 12 cyl V can be arranged to perfectly balance primary and secondary forces, hence their traditional smoothness.

[GroundEffect]

captain_cynic said:

Is there a reason we can't have "small" big engines. Why does a V8 need to be a massive 5L monster. We can make a decent 1.6L I4 that is better than a 2L 4.pot from 20 years ago... Why don't manufacturers make a 3.2L V8?

Is it just lack of demand or are there technological limitations?

The size per cylinder is a big part for overall efficiency. Everyone's settled on around 500cc/cylinder - so where you might have had a 1.6 4 cyl previously (400cc/cyl) you now see 1.5 3 cyl. That gives:

- Inside the cylinder a better volume to surface area ratio (as an object increases in size, it's volume goes up at a cube rate and surface area quadratically. So you're spreading the heat around in the fluid rather than transferring it to the cylinder walls/coolant
- For a given volume you have less piston ring area touching the cylinder walls by making the cylinders larger - less mechanical friction
- To keep overall engine size down, you tend to have smaller bores on multi-cylinder engines of lower capacity, which means less valve area and less efficient cylinder filling - lower volumetric efficiency/lower specific output
- Fewer components - cheaper to make the engine
- Turbocharging is ubiquitous now (because they're cheap) so you don't need the capacity to get the torque/power

[Clockwork Cupcake]

If you want to go down an absolute rabbit hole of highly technical (but accessible) videos on various engine designs and the like, including explanations on engine balance, thermal efficiency, and the like, then this guy's YouTube channel is superb.

I really recommend it.

https://www.youtube.com/@d4a

[GroundEffect]

Clockwork Cupcake said:

If you want to go down an absolute rabbit hole of highly technical (but accessible) videos on various engine designs and the like, including explanations on engine balance, thermal efficiency, and the like, then this guy's YouTube channel is superb.

I really recommend it.

https://www.youtube.com/@d4a

Agreed. He's good.

[Error_404_Username_not_found]

RenesisEvo said:

A 6 or 12 cyl V can be arranged to perfectly balance primary and secondary forces, hence their traditional smoothness.

Not strictly true. AFAIK only boxers can be arranged to eliminate both primary and secondary imbalance.
You can of course use Lanchester shafts, but they come with a penalty of power sapping.
And none of the above addresses rocking couples or firing order imbalance.