OzVMX Forum
Clubroom => General Discussion => Topic started by: TooFastTim on October 25, 2012, 07:19:15 pm
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Not the sort of thing you'd expect to find in chaps shed:
http://www.youtube.com/watch?v=qM7ksfRVF70&feature=related (http://www.youtube.com/watch?v=qM7ksfRVF70&feature=related)
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Bet his neighbours wished he'd stuck to noisy cars & bikes instead ;D
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Hours of fun for the whole family there. ???
Maybe if he set up the kids 'slippery-dip' behind it and then fired her up........
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Awesome track blower before the next meeting....wont have any complaints about dust then will we.
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Bloody awesome, I want one.
Reckon I could fit that in a XT 250 frame
I look forward to winning Tattslotto so I can be the sort of eccentric that has that sort of stuff sitting around the yard.
Not quite in the same league but my old man had a BSA engine that he turned into a stationary engine, we used to fire it up every other year and watch it vibrate around the floor. These guys were smarter than my Dad though because they bolted their engine down.
Hasn’t been started in 20 years now at least, really must keep the family traditions going and embarrass my kid
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How many of us know why a jet engine moves through the air?
cheers
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BASIC UNDERSTANDING OF THE jET ENGINE PROCESS
The jet engines are essentially a machine designed for the purpose of producing high velocity gasses at the jet nozzle . The engine is started by rotating the compressor with the starter , the outside air enter to the engine . The compressor works on this incoming air and delivery it to the combustion or burner section with as much as 12 times or more pressure the air had at the front . At the burner or combustion section , the ignition is igniting the mixture of fuel and air in the combustion chamber with one or more igniters which somewhat likes automobile spark plugs. When the engine has started and its compressor is rotating at sufficient speed , the starter and igniters are turn off. The engine will then run without further assistance as long as fuel and air in the proper proportions continue to enter the combustion chamber. Only APPROX. 25% of the air is taking part in the actual combustion process . The rest of the air is mixed with the products of combustion for cooling before the gases enter the turbine wheel . The turbine extracts a major portion of energy in the gas stream and uses this energy to turn the compressor and accessories . The engine's thrust comes from taking a large mass of air in at the front and expelling it at a much higher speed than it had when it entered the compressor . THRUST , THEN , IS EQUAL TO MASS FLOW RATE TIMES CHANGE IN VELOCITY .
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(http://upload.wikimedia.org/math/6/1/a/61a840e7e6b25040825c61fd519756ae.png)
and:
(http://upload.wikimedia.org/math/4/f/e/4fef570fa684173cbc6e70a904dd5e66.png)
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Because it is attached to a plane ;D
Cheers
Shaun
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I crack a fatty when you rocket scientists are allowed to expound on the theory of thrust. ;D
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Yes of course , forgot about that Shaun , it needs to be attached to a plane to gain the full value of the engine ;D.
Although there are a bunch of English men that have a fully operational stationary jet engine setup in their garden. "Now that a real party toy."
Almost as good as a petrol powered blender , "hey Marky" 8)
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I have trouble just comprehending the workings of a door handle............... ::)
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The objective of a doorhandle is to the convert rotary motion of your hand in................................................................................. ;D ;D ;D ;D :P :P :P :P
Or you could conceivable use the jet engine mounted on the cradle but it would most likely render the door to a one use only proposition. ;D :P 8)
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to a exit or entry path 8)
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How many of us know why a jet engine moves through the air?
cheers
The object of the jet engine is to make noise.
Noise = power
The very same principle was applied to shorty mufflers.
Noise needs atmosphere to travel.
Atmosphere is sucked into the front of the engine and turned into noise. The engine has big fans inside that amplify the noise and it is this noise that is expelled from the rear of the engine that creates the thrust.
Jet engines don’t work in outer space just like screaming doesn't.
If not bolted down the jet engine will move through the air.
We can easily take advantage of this by bolting the jet engine to a container that can carry people and merchandise.
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Noise = power
The very same principle was applied to shorty mufflers
And politicians. ;)
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Noise = power
The very same principle was applied to shorty mufflers
And politicians. ;)
;D ;D ;D Dam right
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Must be a slow day at work.....I know a bloke who has a Canberra bomber in his back yard.....cool toy.....I reckon we should all chip in and buy one of the old army Iroquos choppers when the government finally gets round to selling them....how cool would that be to rock up to your next VMX meet in one of those....we could store it at GMC's ranch....I'm sure you wouldnt mind picking us all up Geoff...much easier than riding a DT400. ;D
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There's a Canberra at HARS (http://hars.org.au/ (http://hars.org.au/)) in the "Gong. Looks fine (smaller than you'd think though) but isn't airworthy. Apparently it was used to take air samples after the A-bomb tests and, well, the decontamination process was a little too thorough.
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how cool would that be to rock up to your next VMX meet in one of those
And freak out any Vietnam vets that just happen to be there :o
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how cool would that be to rock up to your next VMX meet in one of those
And freak out any Vietnam vets that just happen to be there :o
Ya know as somebody new'ish to this neck of the woods I keep forgetting about the ANZAC involvement in that war.
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O K. My simple question although well answered by HVA61, to me has not addressed the real qustion.
If the forward motion was bought about by the pressure of lots of air sqirting out the rear and it won't work in outer space (primarily 'cause there's no air to go in the front) how come a rocket will work in outer space even though there is nothing to thrust against?
Is there a mechanical engineer on here that can answer?
I think I know how it works but I would like to hear an expert on this.
Cheers.pancho.
P.S. not VMX but this is in the correct forum space I believe. (general discussion.)
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What, your telling me none of you blokes have a jet engine in your shed?? ???
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Um... building one from scrap in my shed. Have procured various pumps for the fuel and turbine bearing lubrication :) Working on the fuel injection and metering/firing chambers and afterburner now. Blokes got ta have a project. Thanks to the internet for the plans.... Tim754
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O K. My simple question although well answered by HVA61, to me has not addressed the real qustion.
If the forward motion was bought about by the pressure of lots of air sqirting out the rear and it won't work in outer space (primarily 'cause there's no air to go in the front) how come a rocket will work in outer space even though there is nothing to thrust against?
Is there a mechanical engineer on here that can answer?
I think I know how it works but I would like to hear an expert on this.
Cheers.pancho.
P.S. not VMX but this is in the correct forum space I believe. (general discussion.)
Laws of physics for each force there is an equal although opposite reactive force.
An example if you were in outer space and fired a gun (ignoring the fact that as there is no air would the bullet actually fire) the projectile would travel at a set speed in one direction and you would travel at the same speed in the opposite direction.
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What, your telling me none of you blokes have a jet engine in your shed??
I've got a butane gas torch and a dog that farts....either of them cut it?
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A friend of mine built a jet engine using a truck turbo and a kero heater jet and AC plug ignition. It certainly propelled his billy cart fast in a striaght line and made the most unbelievable amount of noise so maybe GMC is correct. I kid you not ;D ::)
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how come a rocket will work in outer space even though there is nothing to thrust against?
Is there a mechanical engineer on here that can answer?
Every action has an equal and opposite reaction.
Google rocket principle and you'll get something like this:
With rockets, the action is the expelling of gas out of the engine. The reaction is the movement of the rocket in the opposite direction. To enable a rocket to lift off from the launch pad, the action, or thrust, from the engine must be greater than the mass of the rocket. In space, however, even tiny thrusts will cause the rocket to change direction.
One of the most commonly asked questions about rockets is how they can work in space where there is no air for them to push against. The answer to this question comes from the third law. Imagine the skateboard again. On the ground, the only part air plays in the motions of the rider and the skateboard is to slow them down. Moving through the air causes friction, or as scientists call it, drag. The surrounding air impedes the action-reaction.
As a result rockets actually work better in space than they do in air. As the exhaust gas leaves the rocket engine it must push away the surrounding air; this uses up some of the energy of the rocket. In space, the exhaust gases can escape freely.
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Laws of physics for each force there is an equal although opposite reactive force.
Almost true. The law actually states: "for each reaction there is an equal although opposite reaction.
An example if you were in outer space and fired a gun (ignoring the fact that as there is no air would the bullet actually fire) the projectile would travel at a set speed in one direction and you would travel at the same speed in the opposite direction.
Not true. P=mv. Momentum is conserved so m1v1 = m2v2. The bullet buggers off at say 200m/s (v1) and it weighs say 0.05 kg (50 grams, m1) so P = 200 x 0.05 = 10. But you weigh 80kgs (m2) so 10 = 80 x v2 giving 0.8 m/s for v2 or the rate at which you bugger off backwards. See: http://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentum (http://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentum)
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ignoring the fact that as there is no air would the bullet actually fire
Hmmm, so if gunpowder needs oxygen to explode how does the oxygen get inside the little brass chamber when it’s already full of gunpowder??
And the brass chamber is usually hidden away inside metal components making it hard for oxygen to get in quickly.
And if we sit things on our lap when we are sitting down where does our lap go when we stand up??
If only the forum intellect could be harnessed for good instead of…
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'the rate at which you bugger off backwards' about sums up this lot ;)
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We got 2 Rolls Royce Orpheus jets, one we. Keep at my work and im sitting next to the other right now lol
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Hey GMC, I suspect that gunpowder, like nitro methane. contains its own oxygen?
Hey montynut, my eyes went crossed when I saw all those mathematical hieroglyphics (long time since I was belted for not reciting my multiplication tables) but I get whats happening.(I think!)
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Laws of physics for each force there is an equal although opposite reactive force.
Almost true. The law actually states: "for each reaction there is an equal although opposite reaction.
An example if you were in outer space and fired a gun (ignoring the fact that as there is no air would the bullet actually fire) the projectile would travel at a set speed in one direction and you would travel at the same speed in the opposite direction.
Not true. P=mv. Momentum is conserved so m1v1 = m2v2. The bullet buggers off at say 200m/s (v1) and it weighs say 0.05 kg (50 grams, m1) so P = 200 x 0.05 = 10. But you weigh 80kgs (m2) so 10 = 80 x v2 giving 0.8 m/s for v2 or the rate at which you bugger off backwards. See: http://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentum (http://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentum)
Your correct with your formula but the bullet weight and your weight are dependent on gravity therefore in space where gravity is minimal or effectively zero I believe that the resulting speed of the projectile and the person would be much closer to equal. Well that is my understanding. But does the relative masses of the two bodies compensate for this ??? my head hurts :P
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ignoring the fact that as there is no air would the bullet actually fire
Hmmm, so if gunpowder needs oxygen to explode how does the oxygen get inside the little brass chamber when it’s already full of gunpowder??
And the brass chamber is usually hidden away inside metal components making it hard for oxygen to get in quickly.
And if we sit things on our lap when we are sitting down where does our lap go when we stand up??
If only the forum intellect could be harnessed for good instead of… ;) ;) ;) ;) I've read that somewhere before ;D
;D ;D I hate guns and was posing another question as I didn't really want to think about it ;D I believe there is an oxidising component in the gunpowder.
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Hey GMC, I suspect that gunpowder, like nitro methane. contains its own oxygen?
Hey montynut, my eyes went crossed when I saw all those mathematical hieroglyphics (long time since I was belted for not reciting my multiplication tables) but I get whats happening.(I think!)
I didn't post the formulas
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Laws of physics for each force there is an equal although opposite reactive force.
Almost true. The law actually states: "for each reaction there is an equal although opposite reaction.
An example if you were in outer space and fired a gun (ignoring the fact that as there is no air would the bullet actually fire) the projectile would travel at a set speed in one direction and you would travel at the same speed in the opposite direction.
Not true. P=mv. Momentum is conserved so m1v1 = m2v2. The bullet buggers off at say 200m/s (v1) and it weighs say 0.05 kg (50 grams, m1) so P = 200 x 0.05 = 10. But you weigh 80kgs (m2) so 10 = 80 x v2 giving 0.8 m/s for v2 or the rate at which you bugger off backwards. See: http://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentum (http://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentum)
Your correct with your formula but the bullet weight and your weight are dependent on gravity therefore in space where gravity is minimal or effectively zero I believe that the resulting speed of the projectile and the person would be much closer to equal. Well that is my understanding. But does the relative masses of the two bodies compensate for this ??? my head hurts :P
Tim's "conservation of momentum" equations do apply perfectly in space. The only confusing aspect is that he referred to the "masses" of the objects as their "weights".
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You correct Feetup I was just considering again and the relative mass still applies so Tim is correct. Now the important question how far would the projectile and person travel once the gun was fired ;D ::) Oh FFS forget it :P
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Their speed and direction would vary over time depending on the force of gravity generated by other masses that acted on them as they travelled.
It is only the initial velocities of the person and the bullet that can be calculated by the law of conservation of momentum
Saltpetre (potassium nitrate) is the oxidising agent in gunpowder. Bullets can be successfully fired in space and under water (provided the round is waterproof).
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You correct Feetup I was just considering again and the relative mass still applies so Tim is correct. Now the important question how far would the projectile and person travel once the gun was fired ;D ::) Oh FFS forget it :P
I was just starting to get interested too :D
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Tim's "conservation of momentum" ....... hey who is calling me a lazy bugger >:( Wait sorry is some other Tim :D Tim754 well actually I am...... ;)
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Hey montynut, my eyes went crossed when I saw all those mathematical hieroglyphics (long time since I was belted for not reciting my multiplication tables) but I get whats happening.(I think!)
He he. To be honest so do mine (although I'm quite happy with Hills equation). I just cut and pasted Bernoullis equation and the Navier-Stokes equation. Both describe the behaviour of fluids.
Tim's "conservation of momentum" equations do apply perfectly in space. The only confusing aspect is that he referred to the "masses" of the objects as their "weights".
When I wrote that I knew somebody was going to pick me out for using the word weight. Dave you are correct I should have used mass.
Now the important question how far would the projectile and person travel once the gun was fired
In deep space? Assuming a (near) perfect vacuum and no nearby "massive" bodies? A bloody long way. Perhaps forever. At least until it falls under the influence of a massive body or the vacuum ceases to be near perfect. Hwever far that may be.
During the Gemini project when NASA was experimenting with space walks the problem soon showed itself. The simplest movement in space has consequences that you'd normally never dream of. For example: you lift your arm to reach for something, your arm rotates in its socket, there is an equal and opposite reaction so your entire body begins to rotate in the opposite direction. The astronauts would end up disorientated and exhausted.The problem was so bad that it nearly canned the moon race. But one astronaut thought about it and introduced special foot and handholds on the space craft and introduced training in the world biggest swimming pool. That astronauts name? Buzz Aldrin. Buzz is a clever phucker with a PhD in orbital mechanics. Buzz saved the moon race.
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(although I'm quite happy with Hills equation).
Ah yes, Hills equation.
Finally you’re talking about something I know about.
Hills equation states that while rotational direction is a variable relative to rise and fall, the force required during rise and fall is directly proportional to the amount of wet washing on the hoist at the time.
During the Gemini project when NASA was experimenting with space walks the problem soon showed itself. The simplest movement in space has consequences that you'd normally never dream of. For example: you lift your arm to reach for something, your arm rotates in its socket, there is an equal and opposite reaction so your entire body begins to rotate in the opposite direction. The astronauts would end up disorientated and exhausted.The problem was so bad that it nearly canned the moon race. But one astronaut thought about it and introduced special foot and handholds on the space craft and introduced training in the world biggest swimming pool. That astronauts name? Buzz Aldrin. Buzz is a clever phucker with a PhD in orbital mechanics. Buzz saved the moon race.
Was that Buzz on the Halloween episode of Big Bang Theory the other night?
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Hills equation:
(http://upload.wikimedia.org/math/f/2/a/f2a1cd78ed872e47735947e0d278d591.png)
Used in designing particle accelerators. It implies that in addition to moving forward the particle oscillates on the x, y and z axes. Its kinda important if you want an accelerator to work.
Yes, apparently (I don't watch sitcoms) Aldrin was on the Big Bang Theory.
OK, I'll go back to having a sense of humour now ;D
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How many of us know why a jet engine moves through the air?
cheers
Seeing that you were being serious I'll answer your question as best I can.
If you think about a 2 stroke engine it has 2 strokes of the piston for a cycle. Basically these are compression and exhaust (I'll ignore how the mixture gets into the barrel for this explanation). A jet engine is similar. The air is sucked in at the front and compressed, the fuel is then burned and it is exhausted out the back:
A big difference is that the fuel is burned continuously and not in cycles.
After the fuel is burned at expands rapidly causing the turbine at the back to rotate which drives the compressor...
(http://www.scienceinthenews.org.uk/images/contents/15/en/75.jpg)
When Whittle first conceived the jet engine he realized that, with a turbo charged piston engine, you didn't really need the piston engine and that it could be replaced with just a combustion chamber and, if you look at his design (called a centrifugal jet) you'll see that's exactly what it is:
(http://www.fiddlersgreen.net/aircraft/Lockheed-P80/IMAGES/Sketch-Allison-Engine-P80.jpg)
Look familiar?
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So when you look at the first of those two diagrams it seems to show thrust effectively generated from the high pressure turbine (group of four) thence the equal and opposite direction thrust would react on those turbine blades.
So it appears that this action/reaction is similar to what makes an ordinary propellor move through the air.
All very interesting.
;D pancho.
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The top engine is a turbo fan while the bottom is a turbo jet
have a look at these
http://www.animatedengines.com/jets.html
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l
Ah yes, Hills equation.
Finally you’re talking about something I know about.
Hills equation states that while rotational direction is a variable relative to rise and fall, the force required during rise and fall is directly proportional to the amount of wet washing on the hoist at the time.
[/quote
:D :D :D
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So when you look at the first of those two diagrams it seems to show thrust effectively generated from the high pressure turbine (group of four) thence the equal and opposite direction thrust would react on those turbine blades.
So it appears that this action/reaction is similar to what makes an ordinary propellor move through the air.
Sort of. Part of the thrust generated by the exhaust from the combustion chamber drives the turbine which in turn drives the compressor and the rest of the thrust pushes the engine forward. A bit like a 2T motor where some of the torque generated by the piston is used to drive the pistons back up and the rest to drive the back wheel via the clutch and gearbox.
The top engine is a turbo fan while the bottom is a turbo jet
Yeah, I wasn't going to go into that but that was the best piccie I could find.
Pancho, as Montynut says the first piccie is of a turboFAN motor. The first "propeller" is actually external and is not used for compression but is really a giant prop on the end of the shaft. Its this that in most modern engines provides 75% of the thrust. The exhaust accounts for the remaining 25%.
PS it's this propeller that is most obvious on almost all airliners today.
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Turbo jet is heaps easier to attempt to build at home ;) Tim754
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After all that I'm glad I asked my simple question.!
Shows what brain power is available on our forum.
cheers pancho.