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Helium lifting ability
Anyone know offhand without going to too much trouble, what is the ratio
for volume of helium to lbs force against gravity ? Fred |
Helium lifting ability
A cubic foot of air at sea level under standard conditions weighs
about 0.077 lb, so if you displaced that cubic foot of air with helium, the net lifting force would be slightly less than that (i.e., 0.077 lb minus the weight of a cubic foot of helium, which I don't know the value of offhand). Of course, you also have to subtract the weight of the container. Bert ff wrote: Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? Fred |
Helium lifting ability
Sounds like another budding lawn chair pilot in the making.
I'm not sure but the simple way would be to get a 4oz fishing weight and see how many balloons you need to lift it and multiply this by 4. Saturday mornings at auto dealerships they usually have a whole lot of balloons they might let you play with. -- Roger Shoaf If you are not part of the solution, you are not dissolved in the solvent. "ff" wrote in message ... Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? Fred |
Helium lifting ability
I believe a cubic foot of helium will lift about 28.2 grams. Multiply
the volume times 28 and divide by 448 g/lb. A 10' diameter weather balloon will lift about 32 pounds. ff wrote: Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? Fred -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Helium lifting ability
On Sun, 20 Jul 2003 05:16:09 GMT, ff wrote:
Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? A Google.com search on: helium lift cubic foot ....found more than one thousand, three hundred web pages with the information you want. No trouble at all. -- --Pete "Peter W. Meek" http://www.msen.com/~pwmeek/ |
Helium lifting ability
On Sun, 20 Jul 2003 05:16:09 GMT, ff wrote:
,;Anyone know offhand without going to too much trouble, what is the ratio ,; for volume of helium to lbs force against gravity ? I don't think there is an answer to your question but... I think you are asking about Archimedes principle... All bodies floating on or submerged in a fluid are buoyed up by a force exactly equal to the weight of the fluid they displace. 1 cubic foot of air= 0.0807 pounds at 32 F and 1 atm. 1 cubic foot of helium= 0.0111 (same conditions) If you are planning a trip in a lawn chair that should provide the needed information. |
Helium lifting ability
On Sun, 20 Jul 2003 05:16:09 GMT, ff wrote:
Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? Fred I am unable to resist. Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? YES Errol Groff Instructor, Machine Tool Department H.H. Ellis Tech 613 Upper Maple Street Danielson, CT 06239 860 774 8511 x1811 http://pages.cthome.net/errol.groff/ http://newenglandmodelengineeringsociety.org/ |
Helium lifting ability
In article ,
Don Wilkins wrote: On Sun, 20 Jul 2003 05:16:09 GMT, ff wrote: ,;Anyone know offhand without going to too much trouble, what is the ratio ,; for volume of helium to lbs force against gravity ? I don't think there is an answer to your question but... I think you are asking about Archimedes principle... All bodies floating on or submerged in a fluid are buoyed up by a force exactly equal to the weight of the fluid they displace. 1 cubic foot of air= 0.0807 pounds at 32 F and 1 atm. 1 cubic foot of helium= 0.0111 (same conditions) And -- of course -- one cubic foot of vacuum would lift the full 0.0807 pounds (again at STP), but the trick is finding a rigid container which doesn't weigh more than the lift. :-) If you are planning a trip in a lawn chair that should provide the needed information. Be sure to file your flight plan. :-) Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
Helium lifting ability
On Mon, 21 Jul 2003 02:05:39 GMT, Jeff Wisnia
wrote: So what *is* the pressure in a typical rubber party balloon. IIRC, it gets *lower* as the balloon expands. I think it's the same with soap bubbles. I suppose the pressure in one of those mylar party balloons must be pretty close to one atmosphere. If the sides are not rigid it's always *exactly* atmospheric pressure. If it expands either atmospheric pressure has dropped or the temperature of the balloon has gone up. Here's a question for everyone. Explain *exactly* the mechanics of how and why a balloon floats :^)? Not as easy as one might think. And a second one is why when you have a helium balloon in your car and put the brakes on to stop, the balloon will float to the back of the car instead of flying to the front like everything else. Again, what are the mechanics that make it do so? John Please note that my return address is wrong due to the amount of junk email I get. So please respond to this message through the newsgroup. |
Helium lifting ability
Errol Groff wrote:
On Sun, 20 Jul 2003 05:16:09 GMT, ff wrote: Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? Fred I am unable to resist. Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? YES Thank you for sharing that information :-) For those who were wondering, I'm not going flying in my lawn chair !! I have some R/C gear and was contemplating building a small blimp or dirigible. So I was wondering how large it would have to be to carry motor, battery, receiver and servos. Anyone ever tried this or seen one? Fred |
Helium lifting ability
"John Flanagan" wrote in message ... On Mon, 21 Jul 2003 02:05:39 GMT, Jeff Wisnia wrote: So what *is* the pressure in a typical rubber party balloon. IIRC, it gets *lower* as the balloon expands. I think it's the same with soap bubbles. I suppose the pressure in one of those mylar party balloons must be pretty close to one atmosphere. If the sides are not rigid it's always *exactly* atmospheric pressure. If it expands either atmospheric pressure has dropped or the temperature of the balloon has gone up. Here's a question for everyone. Explain *exactly* the mechanics of how and why a balloon floats :^)? As I understand the physics, air is a fluid and the helium balloon being lighter than the air around it floats just as a drop of oil will float if released from the bottom of a volume of water. Not as easy as one might think. And a second one is why when you have a helium balloon in your car and put the brakes on to stop, the balloon will float to the back of the car instead of flying to the front like everything else. Again, what are the mechanics that make it do so? Again the air being heaver than the balloon the air has more mass. When this mass is in motion, pressure is equal on all sides of the balloon. When the brakes are applied the air inside the car keeps moving at the speed the car was going until it hits the windshield. As air bunches up in the front part of the car, there is more air pressure at the front of the car and less at the back so the pressure in the front pushes the lighter balloon backwards. -- Roger Shoaf If you are not part of the solution, you are not dissolved in the solvent. |
Helium lifting ability
ff wrote in message ... Errol Groff wrote: On Sun, 20 Jul 2003 05:16:09 GMT, ff wrote: Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? Fred I am unable to resist. Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? YES Thank you for sharing that information :-) For those who were wondering, I'm not going flying in my lawn chair !! I have some R/C gear and was contemplating building a small blimp or dirigible. So I was wondering how large it would have to be to carry motor, battery, receiver and servos. Anyone ever tried this or seen one? Never tried one but have seen numerous examples. Galliger (sp?, he of smashed water melons) used one in his act for a while. |
Helium lifting ability
There are at least a dozen R/C blimps available already. They have been
around for years |
Helium lifting ability
|
Helium lifting ability
On Sun, 20 Jul 2003 22:58:47 -0700, "Roger Shoaf"
wrote: As I understand the physics, air is a fluid and the helium balloon being lighter than the air around it floats just as a drop of oil will float if released from the bottom of a volume of water. But, mechanically, "how" does it float. You almost answered it below. Not as easy as one might think. And a second one is why when you have a helium balloon in your car and put the brakes on to stop, the balloon will float to the back of the car instead of flying to the front like everything else. Again, what are the mechanics that make it do so? Again the air being heaver than the balloon the air has more mass. When this mass is in motion, pressure is equal on all sides of the balloon. When the brakes are applied the air inside the car keeps moving at the speed the car was going until it hits the windshield. As air bunches up in the front part of the car, there is more air pressure at the front of the car and less at the back so the pressure in the front pushes the lighter balloon backwards. It took a little time for a friend and I to realize how a balloon floats. I think about half a Big Mac at McDonalds one day. You're correct here. It really puzzled me for awhile when I first noticed this phenonemen (sp). I have a lot of fun with kids when I tell them this, they usually go beserk and get real excited when they see it happen. The reason why a balloon floats in still air is because of the pressure gradient between the top and the bottom of the balloon. Most people don't think there is enough of a gradient to make a balloon float but there is. They usually think of pressure drops between sea level and the top of a mountain, not one over just a foot of height. If the pressure was the same it would sink. John Please note that my return address is wrong due to the amount of junk email I get. So please respond to this message through the newsgroup. |
Helium lifting ability
Errol Groff wrote:
On Sun, 20 Jul 2003 05:16:09 GMT, ff wrote: Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? Fred I am unable to resist. Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? YES That's eggsackly the same answer I give folks who "ask in the negative", as when they barge in on me with, "You haven't seen Gwendolyn have you?" My answer is, "YES, I haven't." Jeff -- Jeff Wisnia (W1BSV + Brass Rat '57 EE) "Success is getting what you like; Happiness is liking what you get." Errol Groff Instructor, Machine Tool Department H.H. Ellis Tech 613 Upper Maple Street Danielson, CT 06239 860 774 8511 x1811 http://pages.cthome.net/errol.groff/ http://newenglandmodelengineeringsociety.org/ |
Helium lifting ability
Subject: Helium lifting ability
From: Jeff Wisnia Date: 21/07/03 03:05 GMT Daylight Time Message-id: So what *is* the pressure in a typical rubber party balloon. IIRC, it gets *lower* as the balloon expands. I think it's the same with soap bubbles. It's higher as the balloon expands or there would be negative work being done to inflate the balloon against the elasticity of the rubber. I suppose the pressure in one of those mylar party balloons must be pretty close to one atmosphere. It can be anything up to what the material will withstand. It can't be lower than atmospheric though because the internal and external pressure will equalise back to atmospheric via a change in volume of the balloon. Once the balloon (given the relatively inelastic material) has reached its maximum volume the internal pressure will rise as more gas is pumped in. The lifting capability will then decrease though as the mass rises for no corresponding gain in volume and boyancy. For a balloon made of inelastic material the maximum lift occurs when the internal pressure is the same as external and the ratio of volume to mass is highest. i.e. fully inflated until the pressure just starts to rise above atmospheric. For a balloon made of elastic material the maximum lift also occurs when the ratio of volume to mass is highest, but the pressure for that depends on the strength and elasticity of the material. Dave Baker - Puma Race Engines (www.pumaracing.co.uk) "How's life Norm?" "Not for the squeamish, Coach" (Cheers, 1982) |
Helium lifting ability
ff wrote:
Errol Groff wrote: On Sun, 20 Jul 2003 05:16:09 GMT, ff wrote: Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? Fred I am unable to resist. Anyone know offhand without going to too much trouble, what is the ratio for volume of helium to lbs force against gravity ? YES Thank you for sharing that information :-) For those who were wondering, I'm not going flying in my lawn chair !! I have some R/C gear and was contemplating building a small blimp or dirigible. So I was wondering how large it would have to be to carry motor, battery, receiver and servos. Anyone ever tried this or seen one? Fred These are readilly available. Have been for several years. Try one of the Indoor Flyer R/C magazines for ad's for these. http://www.google.ca/search?q=radio+...-1&hl=en&meta= Above is a link to a google search for radio control airships. About 5000 links. Some are sure to be pertinant. Have fun! Cheers Trevor Jones |
Helium lifting ability
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Helium lifting ability
In article , Jeff says...
Jeeze Jim, do I row up behind you on the pond and splash a paddle into the water just as you're about to set the hook? LOL! I guess I never did like fishing that much. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
Helium lifting ability
I thought that MAYBE I actually still had the paper those guys wrote--but no.
Memory sez they did an aluminum geodetic frame covered with sheet aluminum triangles, all sealed with wax. I don't remember what stopped them--the sheets or the frame collapsing, or all the joints leaking. David "DoN. Nichols" wrote: A high school classmate made a year long project of building a vacuum balloon. He had more success than I gather the physics teacher thought he would have, but still no-go for positive buoyancy. I was sort of thinking of doing it for a package to mail via the USPS. Watch them try to figure out the proper postage on something which was a one or two foot sphere, but which didn't show up on their scales. :-) I was thinking of perhaps a titanium sphere, and wondering what the minimum wall thickness to sustain it against a vacuum. But I never got around to it. What did he use for materials and shape? Enjoy, Don. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
Helium lifting ability
Momentum?
-c. "Roger Shoaf" wrote in message ... "John Flanagan" wrote in message ... On Mon, 21 Jul 2003 02:05:39 GMT, Jeff Wisnia wrote: So what *is* the pressure in a typical rubber party balloon. IIRC, it gets *lower* as the balloon expands. I think it's the same with soap bubbles. I suppose the pressure in one of those mylar party balloons must be pretty close to one atmosphere. If the sides are not rigid it's always *exactly* atmospheric pressure. If it expands either atmospheric pressure has dropped or the temperature of the balloon has gone up. Here's a question for everyone. Explain *exactly* the mechanics of how and why a balloon floats :^)? As I understand the physics, air is a fluid and the helium balloon being lighter than the air around it floats just as a drop of oil will float if released from the bottom of a volume of water. Not as easy as one might think. And a second one is why when you have a helium balloon in your car and put the brakes on to stop, the balloon will float to the back of the car instead of flying to the front like everything else. Again, what are the mechanics that make it do so? Again the air being heaver than the balloon the air has more mass. When this mass is in motion, pressure is equal on all sides of the balloon. When the brakes are applied the air inside the car keeps moving at the speed the car was going until it hits the windshield. As air bunches up in the front part of the car, there is more air pressure at the front of the car and less at the back so the pressure in the front pushes the lighter balloon backwards. -- Roger Shoaf If you are not part of the solution, you are not dissolved in the solvent. |
Helium lifting ability
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Helium lifting ability
Subject: Helium lifting ability
From: jim rozen Date: 22/07/03 19:56 GMT Daylight Time Message-id: In article , says... The reason why a balloon floats in still air is because of the pressure gradient between the top and the bottom of the balloon. I really don't understand this. Are you talking about the pressure gradient in the atmosphere? Yes. Which by definition means that there is also a pressure gradient between the top and bottom of the balloon, albeit a very minute one. The essential bit though is only that there be a density gradient. The fact that this is caused primarily by pressure is not relevant. It could also be caused by temperature. The balloon rises to a point at which it displaces exactly its own mass. If it were to rise higher it would displace less than its mass and so sink again. The reverse would happen if it were to sink from the equilibrium point. If that were the case then even a ballon filled with air would float, because it sees the same gradient as one filled with helium. But air-filled ballons don't float because the amount of lift from that effect is very, very tiny. I'm not sure what you are taking the term "pressure gradient" to be but I think you are misunderstanding it. It simply means there is a static density gradient and the original point might have been better made using this term. There is no way a balloon filled with air can float in air of the same density unless the material of the balloon is also less dense than air. Things float because the volume of fluid they displace, weighs less than their own mass. This is true even in incompressible fluids, like water for example. Exactly. But in incompressible fluids objects generally either sink to the bottom or float to the top. In compressible ones they can find an equilibrium point from which they rise no higher. Strictly speaking even the tiny amount of compressibility in liquids means that there is a small density gradient and a possible equilibrium position for a submerged object but it's a very unstable equilibrium and requires that the density of the object falls somewhere within the tiny range of densities of the liquid between the top and bottom. Dave Baker - Puma Race Engines (www.pumaracing.co.uk) "How's life Norm?" "Not for the squeamish, Coach" (Cheers, 1982) |
Helium lifting ability
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Helium lifting ability
jim rozen wrote:
In article , says... The reason why a balloon floats in still air is because of the pressure gradient between the top and the bottom of the balloon. I really don't understand this. Are you talking about the pressure gradient in the atmosphere? If that were the case then even a ballon filled with air would float, because it sees the same gradient as one filled with helium. But air-filled ballons don't float because the amount of lift from that effect is very, very tiny. The pressure differential is only half of the equation. It has to be balanced against the weight of the balloon. In the case of a helium-filled balloon that rises, the net force resulting from the pressure differential is greater than the weight of the balloon, so it pushes the balloon up. For an air-filled balloon, the weight of the balloon is greater than the resultant buoyant force, so the balloon sinks. The amount of force involved is not as tiny as you think. At sea level at 59 deg F, the pressure gradient is about 0.000531 psi / ft, or 0.0765 psf / ft. To simplify calculations, let's assume we have a balloon in the shape of a cube 1 ft on each side. The difference in the upward pressure acting on the bottom square foot and the downward pressure acting on the upper square foot is therefore 0.0765 lb, or 1.22 oz, acting in an upward direction. (Note that these numbers are the same as the weight of one cubic foot of air under these conditions -- this isn't a coincidence!) This force is greater than the combined weight of a cubic foot of helium (at near ambient pressure) and a balloon; it's less than the combined weight of a cubic foot of air and a balloon. (An empty balloon this size would probably weigh 1/3 to 1/2 oz, based on the weight of a smaller balloon I had lying around.) Things float because the volume of fluid they displace, weighs less than their own mass. This is true even in incompressible fluids, like water for example. The weight of the fluid displaced is simply an easily computed surrogate for the force due to the pressure differential. Both values turn out to be exactly the same (regardless of whether the fluid is compressible or not). But physically speaking, the balloon moves because of the forces acting on it, and the force acting on it due to the surrounding atmosphere is transmitted through pressure (which is the result of individual gas molecules impinging on the balloon). Bert |
Helium lifting ability
Very good description Bert.
John On Tue, 22 Jul 2003 19:48:05 -0500, Bert wrote: jim rozen wrote: In article , says... The reason why a balloon floats in still air is because of the pressure gradient between the top and the bottom of the balloon. I really don't understand this. Are you talking about the pressure gradient in the atmosphere? If that were the case then even a ballon filled with air would float, because it sees the same gradient as one filled with helium. But air-filled ballons don't float because the amount of lift from that effect is very, very tiny. The pressure differential is only half of the equation. It has to be balanced against the weight of the balloon. In the case of a helium-filled balloon that rises, the net force resulting from the pressure differential is greater than the weight of the balloon, so it pushes the balloon up. For an air-filled balloon, the weight of the balloon is greater than the resultant buoyant force, so the balloon sinks. The amount of force involved is not as tiny as you think. At sea level at 59 deg F, the pressure gradient is about 0.000531 psi / ft, or 0.0765 psf / ft. To simplify calculations, let's assume we have a balloon in the shape of a cube 1 ft on each side. The difference in the upward pressure acting on the bottom square foot and the downward pressure acting on the upper square foot is therefore 0.0765 lb, or 1.22 oz, acting in an upward direction. (Note that these numbers are the same as the weight of one cubic foot of air under these conditions -- this isn't a coincidence!) This force is greater than the combined weight of a cubic foot of helium (at near ambient pressure) and a balloon; it's less than the combined weight of a cubic foot of air and a balloon. (An empty balloon this size would probably weigh 1/3 to 1/2 oz, based on the weight of a smaller balloon I had lying around.) Things float because the volume of fluid they displace, weighs less than their own mass. This is true even in incompressible fluids, like water for example. The weight of the fluid displaced is simply an easily computed surrogate for the force due to the pressure differential. Both values turn out to be exactly the same (regardless of whether the fluid is compressible or not). But physically speaking, the balloon moves because of the forces acting on it, and the force acting on it due to the surrounding atmosphere is transmitted through pressure (which is the result of individual gas molecules impinging on the balloon). Bert Please note that my return address is wrong due to the amount of junk email I get. So please respond to this message through the newsgroup. |
Helium lifting ability
On Mon, 21 Jul 2003 02:05:39 GMT, Jeff Wisnia
wrote something .......and in reply I say!: So what *is* the pressure in a typical rubber party balloon. IIRC, it gets *lower* as the balloon expands. I think it's the same with soap bubbles. It will go past a maximum point, because as the balloon stretches, it becomes weaker and therefore requires less PSI to expand, but inside will always be higher than outside pressure. ************************************************** **************************************** Huh! Old age!. You may hate it, but let me tell you, you can't get by for long without it! Nick White --- HEAD:Hertz Music Please remove ns from my header address to reply via email !! ") _/ ) ( ) _//- \__/ |
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