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Put armor where there aren't bullet holes

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Re: Put armor where there aren't bullet holes

#21

Post by ced »

werftgh wrote: post #16
teilo wrote: post #11

This reminds me of the story of the US army moving from canvas to metal helmets. To their surprise, they found that the number of head injuries went up, and not down. Why? Because the metal helmets converted fatalities to head injuries.

Same thing with bicycle helmets and seatbelts in cars.

This might be closer to the mark:

Under the risk compensation theory, helmeted cyclists may be expected to ride less carefully; this is supported by evidence for other road safety interventions such as seat belts and anti-lock braking systems. Anecdotally, many riders report feeling safer with a helmet: "When I wear it, I feel safe..." One researcher randomized his helmet use over a year of commuting to work and found that he rode slightly faster with a helmet.

Motorists may also alter their behavior toward helmeted cyclists. One small study from England found that vehicles passed a helmeted cyclist with measurably less clearance (8.5 cm) than that given to the same cyclist unhelmeted (out of an average total passing distance of 1.2 to 1.3 metres).

http://en.wikipedia.org/wiki/Bicycle_helmet#Risk_compensatio...

Re: Put armor where there aren't bullet holes

#22

Post by evgen »

werftgh wrote: post #17
dkarl wrote: post #12

Earlier quoted context omitted.

Many, many of the stories you read about insight turn out to be quite exaggerated, with everybody at the time understanding something which after many retellings turns into an amazing breakthrough by one person. Hell, it happens all the time at work, with a bunch of people screaming, "We need to do X, we need to do X," for months on end before they give up and just grumble bitterly about it over beer, and then after…

The astronomer Freeman Dyson was doing similar work for the RAF (I had heard this story attributed to him) Two of his calculations weren't acted on because of illogical users. Very few bombers crashed because of airframe failures as opposed to enemy attacks. Logically it would make sense to make the aircraft weaker but lighter/cheaper/faster the loss of a few % crashing due to breakups would balance being able to esc…

The wrinkle in this story is that both conclusions were eventually discovered by others as well, acted upon, and eventually became the dominant paradigms by the end of the war (Dyson was doing operations research for RAF Bomber Command and claims to have made the suggestion in regards to cutting weight on Lancasters.) Some of the most successful planes in the war embodied this philosophy before Dyson even enlisted. The most successful light bomber in the war was the De Haviland Mosquito, which was made primarily of wood, usually carried no machine guns, and could outrun every other plane in the sky until the arrival of jet engines.

Re: Put armor where there aren't bullet holes

#23

Post by pg »

robg wrote: post #19
pg wrote: post #14

Earlier quoted context omitted.

It's not completely illogical to want to protect the places with holes, because the distribution of where bullets hit isn't random. Fighter pilots aimed at specific parts of planes they were attacking. And some surfaces would have been protected either by other surfaces or by having a nearly flat angle of incidence to probable incoming fire.

I thought this too, but then realized the humans doing the shooting are also illogical. For instance, I could see how hitting the wings might feel effective and easy, but it's not a great strategy because the bullet holes don't really impact the flight capability.

WW II fighter pilots were very rational about what they aimed at. (I happen to have read a lot about this.)

Re: Put armor where there aren't bullet holes

#24

Post by petenixey »

pg wrote: post #23
robg wrote: post #19

Earlier quoted context omitted.

I thought this too, but then realized the humans doing the shooting are also illogical. For instance, I could see how hitting the wings might feel effective and easy, but it's not a great strategy because the bullet holes don't really impact the flight capability.

WW II fighter pilots were very rational about what they aimed at. (I happen to have read a lot about this.)

Was this because of their incredibly short ammunition reserves? I heard something recently about spitfires having only having about 20s worth of machine gun fire.

Re: Put armor where there aren't bullet holes

#25

Post by anonymous236 »

pg wrote: post #23
robg wrote: post #19

Earlier quoted context omitted.

I thought this too, but then realized the humans doing the shooting are also illogical. For instance, I could see how hitting the wings might feel effective and easy, but it's not a great strategy because the bullet holes don't really impact the flight capability.

WW II fighter pilots were very rational about what they aimed at. (I happen to have read a lot about this.)

What about anti-aircraft ground fire?

Re: Put armor where there aren't bullet holes

#26

Post by btilly »

ced wrote: post #21
werftgh wrote: post #16

Earlier quoted context omitted.

Same thing with bicycle helmets and seatbelts in cars.

This might be closer to the mark: Under the risk compensation theory, helmeted cyclists may be expected to ride less carefully; this is supported by evidence for other road safety interventions such as seat belts and anti-lock braking systems. Anecdotally, many riders report feeling safer with a helmet: "When I wear it, I feel safe..." One researcher randomized his helmet use over a year of commuting to work and foun…

In addition research has shown that cars drive closer to people with helmets than they do to people without them.

Re: Put armor where there aren't bullet holes

#27

Post by silentbicycle »

btilly wrote: post #26
ced wrote: post #21

Earlier quoted context omitted.

This might be closer to the mark: Under the risk compensation theory, helmeted cyclists may be expected to ride less carefully; this is supported by evidence for other road safety interventions such as seat belts and anti-lock braking systems. Anecdotally, many riders report feeling safer with a helmet: "When I wear it, I feel safe..." One researcher randomized his helmet use over a year of commuting to work and foun…

In addition research has shown that cars drive closer to people with helmets than they do to people without them.

Do you have any citations for that? I'm not doubting you, but genuinely curious (and ambivalent about helmets).

There seems to be a pervasive attitude in the US that if you're a cyclist hit by a car when you're not wearing a helmet, you're automatically at fault, because you're not being responsible. Which is weird, because the risk isn't coming from the bikes...and there's a good chance that it makes cycling seem more dangerous that it is, which makes cycling more dangerous (by making safe cycling techniques more obscure, making it less likely that drivers know how cyclists are likely to behave, etc.).

As a data point: I've been in two collisions in eight-ish years of cycling as my primary transportation (in and around Grand Rapids, Michigan). The first time resulted in a skinned knee and elbow, the second time a bad mood, a bent wheel, and a hurried (but passed) Islamic history exam.

I don't think urban cycling is particularly risky, once you know what you're doing. I feel more in control cycling than when I'm driving on ice (physics!), and I've been driving here for a decade. (Fixed-gear bikes are particularly stable on ice, though.)

Re: Put armor where there aren't bullet holes

#28

Post by silentbicycle »

BRadmin wrote: post #9

Survivorship bias: http://en.wikipedia.org/wiki/Survivorship_bias

Would you mind fleshing that out? Just posting two words and linking to wikipedia doesn't add much to the conversation, and people who care about maintaining the level of discourse on HN might heavily downvote you.

Re: Put armor where there aren't bullet holes

#29

Post by mattmaroon »

You must be careful when applying this sort of logic because it assumes that what happens to a plane after its shot is entirely deterministic, ie. if it gets shot in the tail fin it crashes, if it gets shot in the wing it doesn't. That may or may be accurate for planes (I really don't know) but may not for other things.

Suppose anywhere the plane was shot led to a 1/5 chance of the plane crashing, meaning that all places are equally deserving of armor. Suppose also that the wings comprised about 75% of the surface area of the plane. You'd see 3 planes returning with bullet holes in a wing for every 1 with a bullet hole somewhere else. That doesn't mean somewhere else is a better place to put the armor.

It's easy to see how it could be possible, if the odds of a crash weren't uniform (ie if the wings had a slightly higher than average chance of causing a crash if shot in my example above) you could easily come to the wrong conclusion.

Re: Put armor where there aren't bullet holes

#30

Post by brudgers »

ced wrote: post #21
werftgh wrote: post #16

Earlier quoted context omitted.

Same thing with bicycle helmets and seatbelts in cars.

This might be closer to the mark: Under the risk compensation theory, helmeted cyclists may be expected to ride less carefully; this is supported by evidence for other road safety interventions such as seat belts and anti-lock braking systems. Anecdotally, many riders report feeling safer with a helmet: "When I wear it, I feel safe..." One researcher randomized his helmet use over a year of commuting to work and foun…

According to John Forester, being struck by an overtaking car is among the least likely bicycle accidents, even though it is the rationale used to justify mandatory bike lane usage. http://www.johnforester.com/

His book, Effective Cycling is a great way to improve bicycle safety.

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