If you had a piston in a bore, say the same dimensions as a ford 4.1 and the piston is not connected to any conrods or engine, but you mythbusters style detonated an equivalent charge of compressed petrol under the piston how far up a bore would it travel? Or even better, If the bore only extends to the Pistons skirt how far into the air would the piston fly?

AwesomeO said:

If you had a piston in a bore, say the same dimensions as a ford 4.1 and the piston is not connected to any conrods or engine, but you mythbusters style detonated an equivalent charge of compressed petrol under the piston how far up a bore would it travel? Or even better, If the bore only extends to the Pistons skirt how far into the air would the piston fly?

Diameter of the bore?

ratty one said:

AwesomeO said:

If you had a piston in a bore, say the same dimensions as a ford 4.1 and the piston is not connected to any conrods or engine, but you mythbusters style detonated an equivalent charge of compressed petrol under the piston how far up a bore would it travel? Or even better, If the bore only extends to the Pistons skirt how far into the air would the piston fly?

Diameter of the bore?

Whatever it takes to accomodate a 4.1 falcon piston.

AwesomeO said:

ratty one said:

AwesomeO said:

If you had a piston in a bore, say the same dimensions as a ford 4.1 and the piston is not connected to any conrods or engine, but you mythbusters style detonated an equivalent charge of compressed petrol under the piston how far up a bore would it travel? Or even better, If the bore only extends to the Pistons skirt how far into the air would the piston fly?

Diameter of the bore?

Whatever it takes to accomodate a 4.1 falcon piston.

Is 4.1 a diameter or the motor size and name for litres alternatively?

ratty one said:

AwesomeO said:

ratty one said:

Diameter of the bore?

Whatever it takes to accomodate a 4.1 falcon piston.

Is 4.1 a diameter or the motor size and name for litres alternatively?

4.1 is the capacity of the engines combustion spaces.

Bore diameter is 96mm.

capped or uncapped bore and is their water in the bore or are you using the bore like a barrel of a gun and air surrounds the piston only?

their = there

ratty one said:

capped or uncapped bore and is their water in the bore or are you using the bore like a barrel of a gun and air surrounds the piston only?

god i love it when she talks dirty

Dropbear said:

ratty one said:

capped or uncapped bore and is their water in the bore or are you using the bore like a barrel of a gun and air surrounds the piston only?

god i love it when she talks dirty

well. you would need these extra details I am guessing. cause the length of the bore plus the amount of explosive has not yet been stated and and I am guessing those tid bits will help greatly

ratty one said:

capped or uncapped bore and is their water in the bore or are you using the bore like a barrel of a gun and air surrounds the piston only?

I am just thinking Mythbusters style, take a ford 4.1 divorce a piston from its connecting gear, and the cylinder head, explode the fuel air mixture and see how far up it goes.

AwesomeO said:

ratty one said:

capped or uncapped bore and is their water in the bore or are you using the bore like a barrel of a gun and air surrounds the piston only?

I am just thinking Mythbusters style, take a ford 4.1 divorce a piston from its connecting gear, and the cylinder head, explode the fuel air mixture and see how far up it goes.

Maybe Bill could guess. He is good with car type questions.

ratty one said:

AwesomeO said:

ratty one said:

capped or uncapped bore and is their water in the bore or are you using the bore like a barrel of a gun and air surrounds the piston only?

I am just thinking Mythbusters style, take a ford 4.1 divorce a piston from its connecting gear, and the cylinder head, explode the fuel air mixture and see how far up it goes.

Maybe Bill could guess. He is good with car type questions.

Thank god, cause he’s a crappy politician :)

AwesomeO said:

ratty one said:

capped or uncapped bore and is their water in the bore or are you using the bore like a barrel of a gun and air surrounds the piston only?

I am just thinking Mythbusters style, take a ford 4.1 divorce a piston from its connecting gear, and the cylinder head, explode the fuel air mixture and see how far up it goes.

4.1 pistons come with 4 weights. 509/488/402 and 374 gms.For calculating conrod acceleration the removed pin weighs 114 gms.

https://m.youtube.com/watch?v=Dzj7L8Uw66c

AwesomeO said:

If you had a piston in a bore, say the same dimensions as a ford 4.1 and the piston is not connected to any conrods or engine, but you mythbusters style detonated an equivalent charge of compressed petrol under the piston how far up a bore would it travel? Or even better, If the bore only extends to the Pistons skirt how far into the air would the piston fly?

This will give you an idea of how powerful petrol is.
From the wonderful old TV series, ‘The secret life of machines’, with Tim Hunkin.

Video here

The interesting bit starts from about 2:30, but the whole thing is quite interesting.

AwesomeO said:

If you had a piston in a bore, say the same dimensions as a ford 4.1 and the piston is not connected to any conrods or engine, but you mythbusters style detonated an equivalent charge of compressed petrol under the piston how far up a bore would it travel? Or even better, If the bore only extends to the Pistons skirt how far into the air would the piston fly?

> mythbusters style

I once calculated that 2/3 of what Mythbusters does is Newtonian fluid mechanics. This is one example. And I am expert in Newtonian fluid mechanics. So I should be able to answer this one.

But first some clarification needed. What is meant by “equivalent charge”? Do you mean “equal mass of petrol”, “equal amount of energy”, or “equal amount of energy in an enclosed space”? All three are different. The air is compressed in a piston engine, and this greatly affects the speed and uniformity of combustion, even the pattern of swirl created within the cylinder head space affects the completeness of combustion. If the space isn’t enclosed then almost all of the energy is lost to atmosphere. Is this what you want?

If what you really mean is “how fast would the piston be ejected from the barrel if there were no conrod to slow it down?” then the answer can be simply calculated to reasonable accuracy just from the RPM and stroke. Let’s say 3,000 rpm, that’s 50 revs per second. Say a stroke of 0.1 m. Two strokes per rev so that’s an average piston speed of 2*0.1*50 = 10 m/s. But sinusoidal motion so maximum speed is pi/2 times that. So the piston would fly out at about 5*pi = 16 m/s.

If fired vertically at 16 m/s, it comes back to ground in 3.2 seconds. Maximum height 0.5*10*(3.2/2)^2 = 13 metres.

If fired at 45 degrees, it comes back to earth in 32./sqrt(2) = 2.26 seconds. Maximum length of flight 16/sqrt(2)*2.26 = 26 metres.

mollwollfumble said:

AwesomeO said:

If you had a piston in a bore, say the same dimensions as a ford 4.1 and the piston is not connected to any conrods or engine, but you mythbusters style detonated an equivalent charge of compressed petrol under the piston how far up a bore would it travel? Or even better, If the bore only extends to the Pistons skirt how far into the air would the piston fly?

> mythbusters style

I once calculated that 2/3 of what Mythbusters does is Newtonian fluid mechanics. This is one example. And I am expert in Newtonian fluid mechanics. So I should be able to answer this one.

But first some clarification needed. What is meant by “equivalent charge”? Do you mean “equal mass of petrol”, “equal amount of energy”, or “equal amount of energy in an enclosed space”? All three are different. The air is compressed in a piston engine, and this greatly affects the speed and uniformity of combustion, even the pattern of swirl created within the cylinder head space affects the completeness of combustion. If the space isn’t enclosed then almost all of the energy is lost to atmosphere. Is this what you want?

If what you really mean is “how fast would the piston be ejected from the barrel if there were no conrod to slow it down?” then the answer can be simply calculated to reasonable accuracy just from the RPM and stroke. Let’s say 3,000 rpm, that’s 50 revs per second. Say a stroke of 0.1 m. Two strokes per rev so that’s an average piston speed of 2*0.1*50 = 10 m/s. But sinusoidal motion so maximum speed is pi/2 times that. So the piston would fly out at about 5*pi = 16 m/s.

The equivalent charge would be the release of the same amount of energy in the same form and time as would occur in that engines normal combustion process. If the piston was disconnected from conrods and be just sitting in a bore I would think its velocity would be higher?

a petrol injector off an old car squirting into a metal tube should be good enough

the link I gave before was the same thing as bills – the secret life of the internal combustion engine

you could use a beer can that roughly fits the metal tube

you could make plastic rings to help the beer can seal nicely without causing problems

you’d need to strengthen the beer can and weight that front of it so that it flew better

the originally shows the beer can flying a kilometre or more and that wasn’t atomised petrol like in an injector .

if you could get a long barrel and a microcontroller you could probably make an Iraqi supergun

wookiemeister said:

a petrol injector off an old car squirting into a metal tube should be good enough

the link I gave before was the same thing as bills – the secret life of the internal combustion engine

you could use a beer can that roughly fits the metal tube

you could make plastic rings to help the beer can seal nicely without causing problems

you’d need to strengthen the beer can and weight that front of it so that it flew better

the originally shows the beer can flying a kilometre or more and that wasn’t atomised petrol like in an injector .

if you could get a long barrel and a microcontroller you could probably make an Iraqi supergun

I have a microcontroller………………………….. mz Tamb.

Tamb said:

wookiemeister said:

a petrol injector off an old car squirting into a metal tube should be good enough

the link I gave before was the same thing as bills – the secret life of the internal combustion engine

you could use a beer can that roughly fits the metal tube

you could make plastic rings to help the beer can seal nicely without causing problems

you’d need to strengthen the beer can and weight that front of it so that it flew better

the originally shows the beer can flying a kilometre or more and that wasn’t atomised petrol like in an injector .

if you could get a long barrel and a microcontroller you could probably make an Iraqi supergun

I have a microcontroller………………………….. mz Tamb.

you’ll need sensors to detect the can moving down the tube OR set up a firing time for each igniter using trial and error

Ywookiemeister said:

a petrol injector off an old car squirting into a metal tube should be good enough

the link I gave before was the same thing as bills – the secret life of the internal combustion engine

you could use a beer can that roughly fits the metal tube

you could make plastic rings to help the beer can seal nicely without causing problems

you’d need to strengthen the beer can and weight that front of it so that it flew better

the originally shows the beer can flying a kilometre or more and that wasn’t atomised petrol like in an injector .

if you could get a long barrel and a microcontroller you could probably make an Iraqi supergun

I think it is fair to say making a supergun is difficult and if it could be done with old car injectors, a long barrel and a strengthened beer can it would have been done.

Tamb said:

wookiemeister said:

a petrol injector off an old car squirting into a metal tube should be good enough

the link I gave before was the same thing as bills – the secret life of the internal combustion engine

you could use a beer can that roughly fits the metal tube

you could make plastic rings to help the beer can seal nicely without causing problems

you’d need to strengthen the beer can and weight that front of it so that it flew better

the originally shows the beer can flying a kilometre or more and that wasn’t atomised petrol like in an injector .

if you could get a long barrel and a microcontroller you could probably make an Iraqi supergun

I have a microcontroller………………………….. mz Tamb.

you’ll need sensors to detect the can moving down the tube OR set up a firing time for each igniter using trial and error

AwesomeO said:

Ywookiemeister said:

a petrol injector off an old car squirting into a metal tube should be good enough

the link I gave before was the same thing as bills – the secret life of the internal combustion engine

you could use a beer can that roughly fits the metal tube

you could make plastic rings to help the beer can seal nicely without causing problems

you’d need to strengthen the beer can and weight that front of it so that it flew better

the originally shows the beer can flying a kilometre or more and that wasn’t atomised petrol like in an injector .

if you could get a long barrel and a microcontroller you could probably make an Iraqi supergun

I think it is fair to say making a supergun is difficult and if it could be done with old car injectors, a long barrel and a strengthened beer can it would have been done.

a “supergun” , not a real supergun

wookiemeister said:

AwesomeO said:

Ywookiemeister said:

a petrol injector off an old car squirting into a metal tube should be good enough

the link I gave before was the same thing as bills – the secret life of the internal combustion engine

you could use a beer can that roughly fits the metal tube

you could make plastic rings to help the beer can seal nicely without causing problems

you’d need to strengthen the beer can and weight that front of it so that it flew better

the originally shows the beer can flying a kilometre or more and that wasn’t atomised petrol like in an injector .

if you could get a long barrel and a microcontroller you could probably make an Iraqi supergun

I think it is fair to say making a supergun is difficult and if it could be done with old car injectors, a long barrel and a strengthened beer can it would have been done.

a “supergun” , not a real supergun

Sorry, I was confused when you said you could probably make an Iraqi supergun. I was thinking you probably couldn’t.

the petrol mortar would still be good to fire fairly heavy objects ( within reason ) maybe up to a kilo if the barrel was thick enough

if you wanted to go hardcore you could get a tube of the gun alloy

you could attach a motor to the end of the mortar at the base and spin it before launch

hmm didn’t know that

cordite was the explosive used in the detonation system of the Hiroshima bomb

supposedly cordite is gun cotton ( nitric acid poured into cotton ) and nitroglycerin and petroleum jelly

petrol is powerful enough for your purposes