starting without the gas tank

[tatu]

If that was true there would be no water towers.

Are you another who thinks that stuff gets heavier the higher you take it? Just to help you, the more you put up the heavier it gets. Again, a pound of fuel weighs a pound.

[tkent02]

No, to increase 'head' you would need to add more fuel, not put it higher, a pound of fuel is a pound of fuel, to increase 'head' you would put two pounds of fuel.

This is incorrect. The amount of liquid has no effect, zero. It is only the hieght difference that matters.

[tkent02]

are you another who thinks that stuff gets heavier the higher you take it? Just to help you, the more you put up the heavier it gets. Again, a pound of fuel weighs a pound.

this is absolutely incorrect.

[ART]

Are you another who thinks that stuff gets heavier the higher you take it? Just to help you, the more you put up the heavier it gets. Again, a pound of fuel weighs a pound.

No, I'm one of those pesky people who has studied physics.

Think of it like this: Will a bowling ball falling on your foot from one inch hurt as much as one dropped from a building? Liquid works exactly the same.

[tkent02]

Swim ten feet deep in a large lake, then swim ten feet deep in a small pool. The pressure you feel at ten feet is identical. The volume of water has nothing to do with it. Same thing as the pressure head question.

[Ghostgs1]

For an understanding of this principle you need only look at hydro power plants. You either need very large flow or higher pressure to produce the same amount of power. Hence low pressure or high pressure hydro plants. To increase pressure supplied to the penstock or inlet pipe to the turbine, it is sometimes common to use a supply lake or pond, far above the turbine in elevation to increase the head pressure. The old Boulder Hydro and the Glenwood Hydro from the early 1900's are examples of this. Boulder Hydro used a lake about 1500 ft. above that gives it some 800 psi supply pressure while Glenwood Hydro uses a diversion from the Colorado river and very high volume with low pressure to produce electricity at about 12 MWe. The turbines are the same size with only the water wheels being different designs for the change in operating pressure.

[tatu]

This is incorrect. The amount of liquid has no effect, zero. It is only the hieght difference that matters.

A pound of water is a pound of water irrespective of elevation, and the amount has everything to do with it as more liquid = heavier

this is absolutely incorrect.

It is absolutely correct.

No, I'm one of those pesky people who has studied physics.
Please study some more.
Think of it like this: Will a bowling ball falling on your foot from one inch hurt as much as one dropped from a building? Liquid works exactly the same.

Same as a sponge weighing a pound that hit you from a building or a pound of metal dropped from the same place.
This is a confusing analogy and will not help any thing. I don't want to get into this.

Swim ten feet deep in a large lake, then swim ten feet deep in a small pool. The pressure you feel at ten feet is identical. The volume of water has nothing to do with it. Same thing as the pressure head question.

This is also not the same, you are confusing ambient pressure here within the water, a different thing. ((I will give this some more thought because pressure in this case comes from volume and it is an interesting thought) (If I was in a 10' deep tube at the bottom, would I feel the same pressure as at the bottom of a lake, as it is the column of water that is the governing factor there.))
The volume of water has everything to do with it if you were to lift both the pools and attach a pipe to the bottom of each the larger one with more water would have more head because of the weight of the water, more weight = more 'head' = more pressure.

[QUOTE=Ghostgs1;2004738]For an understanding of this principle you need only look at hydro power plants. You either need very large flow or higher pressure to produce the same amount of power. Hence low pressure or high pressure hydro plants. To increase pressure supplied to the penstock or inlet pipe to the turbine, it is sometimes common to use a supply lake or pond, far above the turbine in elevation to increase the head pressure. pressure can only come from increased volume with the greater weight pushing the water down the pipe. A gallon of water from that pond above is not heavier than a gallon at the lower lake. The old Boulder Hydro and the Glenwood Hydro from the early 1900's are examples of this. Boulder Hydro used a lake about 1500 ft. above that gives it some 800 psi supply pressure If you took the extra water from the top of the supply lake you would not gain advantage of the weight of the volume as you would by taking it from the bottom of said supply lake, which is why whe water supplying the turbine to the penstock or inlet is taken from the bottom of the dam because of the weight of the water pressing from above. while Glenwood Hydro uses a diversion from the Colorado river and very high volume with low pressure to produce electricity at about 12 MWe. The turbines are the same size with only the water wheels being different designs for the change in operating pressure. [/QUOTE]
The water wheel will not turn faster because the water came from further away, it turns faster because there is more of it, the flow only is increased because of the weight/head (The volume within the supply pipe on this scale will also a significant factor)

You cannot increase the weight of something, liquid/metal/piece of wood, scotch egg, aeroplane with its tanks full/empty by simply elevating it.
A pound of fuel is a pound of fuel, whether you pick it up an inch off the floor or take it to 10,000 feet it is still the same and no matter how much you try to talk it round, it cannot be changed.

[ART]

It is not about mass (weight), it is about potential energy.
For your model to work, lifting a pound of liquid to a higher elevation would need to require zero energy.
It very clearly does not.

However, you are of corse free to remain ignorant if choose. O:-)

[tkent02]

An airplane does not get heavier when you lift it up, nor does a bucket of water. That's not what we are saying. It does have more potential energy.

The pressure in a pipe or in a lake increases with depth, not with volume.

How often this comes up amazes me, I thought it was Kindergarten level physics.

Spend two minutes Googling it, all very clearly explained.

[tatu]

It is not about mass (weight), it is about potential energy.
For your model to work, lifting a pound of liquid to a higher elevation would need to require zero energy.
It very clearly does not.

However, you are of corse free to remain ignorant if choose. O:-)

You are moving the goal posts here, again. Its not a model nor a dam. What is stated from the beginning is: do not lift the tank higher as it will increase the pressure at the needle valve and will cause a leak. It will not increase pressure and nor will it leak.
Potential energy is something else again. a pound is a pound change that if you can, lift it a 1000 feet it is still a pound of pressure at the end of the pipe, why cant you see that, how will it become two, four, a hundred??? the only factor that will change is the volume in the pipe and insignificant in this case.
And I am really far from ignorant.

An airplane does not get heavier when you lift it up, nor does a bucket of water. That's not what we are saying. It does have more potential energy.

The pressure in a pipe or in a lake increases with depth, not with volume.

How often this comes up amazes me, I thought it was Kindergarten level physics.

In the pipe yes the pressure would, but we are not in the pipe, we are holding the whole pound of fuel, and is what you have been saying. the potential energy is one pound nothing more, and that you will get at the end of the pipe connected to the bottom of the tank not two pounds. and it will not make your vlvs leak. And it is kindergarten physics.

Just add here which make the whole statement even more ridicules is that my gs holds about four gallons roughly about thirty pounds, why tell some body lifting up a stand alone tank lawn mower tank too high will bring a leak?

[hampshirehog]

It's not about the weight. Age is quite correct that a gallon of fuel at 3 feet off the deck weighs exactly the same as a gallon of fuel at 10 feet off the ground. Alright, that's not entirely true as the further you move the fuel away from the centre of the earth the less the effect of gravity - but you're not going to measure that with a set of kitchen scales (and it depends on latitude as the planet isn't a perfect sphere)!

However, the pressure effected by that weight does vary with height. I remember the rule of thumb that for every foot you raise water the pressure exerted increases by half a psi.

In practice however, with the needle valves on these bikes, if the things let go at 3 feet above fuel tank level then they'll let go at tank level.

[tatu]

It's not about the weight. Age is quite correct that a gallon of fuel at 3 feet off the deck weighs exactly the same as a gallon of fuel at 10 feet off the ground. Alright, that's not entirely true as the further you move the fuel away from the centre of the earth the less the effect of gravity - but you're not going to measure that with a set of kitchen scales (and it depends on latitude as the planet isn't a perfect sphere)!

However, the pressure effected by that weight does vary with height. I remember the rule of thumb that for every foot you raise water the pressure exerted increases by half a psi.

In practice however, with the needle valves on these bikes, if the things let go at 3 feet above fuel tank level then they'll let go at tank level.

Wally, absolutely correct. but I didn't want to complicate things further, just wanted to keep it simple. But as we have started..In the old days when I first started offshore, part of the pre job requirement was to go to a known point and measure gravity to calibrate the equipment, gravity is not the same everywhere.

[hampshirehog]

Sorry Chris - I thought it was Adrian causing trouble. Must be that part of the moon cycle.....

Now of course the moon has an effect on the weight of things on earth. Wait until it's overhead and you can eat a very small chocolate between meals and not gain weight.

[tkent02]

In practice however, with the needle valves on these bikes, if the things let go at 3 feet above fuel tank level then they'll let go at tank level.

It's not about letting go. It's about controlling the level, by controlling the flow, while the fuel is flowing. Not about stopping the flow and holding the pressure, it's about controlling the volume in the float bowl accurately. Three times the pressure will flow more and will effect the resulting float level somewhat.

An empty tank, the fuel level is maybe 6 inches above the needle valve? Maybe eight? Full tank maybe 14 - 16 inches? Put the tank up two or three feet higher and you are increasing the flow through the needle valve, the needle then needs to close farther to get the right flow, the floats must float higher to do this, and as the fuel level gets higher, the engine runs richer.

[hampshirehog]

It's not about letting go. It's about controlling the level, by controlling the flow, while the fuel is flowing. Not about stopping the flow and holding the pressure, it's about controlling the volume in the float bowl accurately. Three times the pressure will flow more and will effect the resulting float level somewhat.

An empty tank, the fuel level is maybe 6 inches above the needle valve? Maybe eight? Full tank maybe 14 - 16 inches? Put the tank up two or three feet higher and you are increasing the flow through the needle valve, the needle then needs to close farther to get the right flow, the floats must float higher to do this, and as the fuel level gets higher, the engine runs richer.

The fuel level change is virtually nothing. If it weren't then every time you pushed your bike through the twisties it would run like crap.

Head pressure is height times density times gravity. If you pull a bit of G in a bend it would have the same effect as putting your test tank on your roof.