Build a Wind Tunnel for Indoor Skydiving

[darrellcro]

Or any specific requirments formulas that will help me on my way in building one please.

Moderator's note: this thread is from 2008.

 

[Topher925]

You are going to need to do a LOT of reading if you want to build your own. If you are serious about having a wind turbine to power your home, your better off going out and buying a commercial unit unless you are a master at electrical power systems. There are no actual plans that I know of since no one wants the liability but there is plenty of information. I recommend starting with http://books.google.com/books?id=WeVSAAAAMAAJ&q=wind+turbine+control&dq=wind+turbine+control&pgis=1" and make sure you have a solid foundation of power electronics and control. Including a solid knowledge of PMSMs and SFIMs along with different methods of control them, especially DTC and SVM.

Next you will need to decide what kind of turbine you want (VS,VP), what kind of power output, cut in speed, cut out speed, and you will also need to know a lot about your wind conditions. That is average wind velocities, capacity factors, wind variance, and velocity distribution.

If you need any more info or help let me know, I sort of an expert on the subject.

 

[jaseh86]

I found this australian website that seems to offer plans for sale, but its no small price.

http://www.indoorskydiving.net/ordernow.html

 

[mshinavar]

You are going to need to do a LOT of reading if you want to build your own. If you are serious about having a wind turbine to power your home, your better off going out and buying a commercial unit unless you are a master at electrical power systems. There are no actual plans that I know of since no one wants the liability but there is plenty of information. I recommend starting with http://books.google.com/books?id=WeVSAAAAMAAJ&q=wind+turbine+control&dq=wind+turbine+control&pgis=1" and make sure you have a solid foundation of power electronics and control. Including a solid knowledge of PMSMs and SFIMs along with different methods of control them, especially DTC and SVM.

Next you will need to decide what kind of turbine you want (VS,VP), what kind of power output, cut in speed, cut out speed, and you will also need to know a lot about your wind conditions. That is average wind velocities, capacity factors, wind variance, and velocity distribution.

If you need any more info or help let me know, I sort of an expert on the subject.

maybe you misread the original post. i would guess he is asking about something like this:
http://www.iflyhollywood.com/

otherwise known as vertical wind tunnels

"i want to build my own wind tunnel" vs. "i want to build my own wind turbine"

 

[Topher925]

maybe you misread the original post.

Yes I did. It was just one of those days. What are they called again? Oh yes, Fridays. :zzz:

 

[RonL]

maybe you misread the original post. i would guess he is asking about something like this:
http://www.iflyhollywood.com/

otherwise known as vertical wind tunnels

"i want to build my own wind tunnel" vs. "i want to build my own wind turbine"

After looking at the website, there are two things mentioned that should help darrellcro calculate his needs, (A) below 6', the weight has to be below 230 pounds, (B) over 6' the weight has to be below 250 pounds.

Do your math, and the wind velocity can be calculated.

For a one or two person size, a fan or propeller system can be designed, that might not be too large. Unless this will be built at a commercial property, power supply might be a major issue.

 

[Mech_Engineer]

It is my suspicion that a sky-diving wind tunnel like you are proposing will have very large power requirements. If my calculations are correct, a 10 ft. diameter wind tunnel with a speed of 120 mph (approximate terminal velocity of a skydiver in the "flat" oriantation) would need 690 kW (925 hp, about $90 per hour using average electrical prices) just for the required kinetic energy of the air going through the tunnel (assuming the air is accelerated from still outside air, not a closed-loop system), not including drag losses in the tunnel which would increase the power requirement.

A wind tunnel of the same dimensions with a speed of 200 mph (skydiver going down headfirst) would require approximately 3.2 MW (4300 hp, $415 per hour).

 

[CPTMAC]

Ok, the issue I see with the above scenario is that he is not calculating any drive gearing into the equation, for pure shaft power output he is right.

So what you will need are the following components;

A large stable mesh platform to mount several large fans under.

I suggest a series of 3-4, 8-14 foot fans. Each fan needs to have spacing of 2-3 feet to allow pressure to build up in between the fans. They will need to be mounted in a fairly airtight circular structure with 2-3 feet above them before the mesh for the bottom of the high pressure/speed tunnel.

The Air Intakes will need to be screened and well protected to avoid sucking in particles which, accelerated to 130-180 MPH, could kill someone.

A high horsepower V-8 engine connected to the right gear box can easily put out enough power to send 4 or 5 people 10-15 feet off the mesh if the tunnel is built open or closed above the fans, you will probably burn the equivalent of about 4-8 mpg of unleaded gasoline, depending on your engine. V-8 engines routinely accelerate (with proper gearing) 3000+ pound Nascars to well over 200 mph, 4 or 5 180-230 lb people in a column of air should be no problem

v/r
MAC

 

[Cyrus]

I suggest you calculate how much this tunnel will cost you to build and operate. I'll bet you $20USD that for that same amount of money, you could get many, many jumps out of an actual aircraft.

 

[herpamad]

This this is a great project, would love to know if you go and do it.

A portable one costs 400k over in the USA, so that's the same price as 21k solo jumps from an aircraft.

I was also wondering, what is the best propeller design for this type of application?

Guessing that some designs will provide more wind-speed than others? So is it possible that the better designed props need lower power-input?

Seems the basic ones use 2 blade prop, direct diesel powered, and the more advanced use 3/4 blade props with electric motor powered by diesel engine(s).

Seems that they use a single prop, but was suggested that 2 props could be used.

Anyone more info on this? the static structure design above the prop look like a static fan.

 

[pwscottiv]

It is my suspicion that a sky-diving wind tunnel like you are proposing will have very large power requirements. If my calculations are correct, a 10 ft. diameter wind tunnel with a speed of 120 mph (approximate terminal velocity of a skydiver in the "flat" oriantation) would need 690 kW (925 hp, about $90 per hour using average electrical prices) just for the required kinetic energy of the air going through the tunnel (assuming the air is accelerated from still outside air, not a closed-loop system), not including drag losses in the tunnel which would increase the power requirement.

A wind tunnel of the same dimensions with a speed of 200 mph (skydiver going down headfirst) would require approximately 3.2 MW (4300 hp, $415 per hour).

How did you calculate the power requirements? The published values I've seen for wind tunnels are around 1000-1400hp and can achieve up to 180mph wind speed. The one I flew in had five ducted five-blade fans that were about 24in dia with the electric motor in the center of each housing. Also, $90/hr is a bargain, when you consider that they charge around $850/hr to fly in the tunnel. I'd definitely consider building one if I had the time and resources.

 

[Mech_Engineer]

How did you calculate the power requirements? The published values I've seen for wind tunnels are around 1000-1400hp and can achieve up to 180mph wind speed. The one I flew in had five ducted five-blade fans that were about 24in dia with the electric motor in the center of each housing. Also, $90/hr is a bargain, when you consider that they charge around $850/hr to fly in the tunnel. I'd definitely consider building one if I had the time and resources.

For the calculations I just basically figure out the mass of air you would have going though a 10 ft diameter tunnel at 120 mph, and calculate the kinetic energy per time that would be required to accelerate that air. I'm actually suprised I got as close to the published values as I did, considering the gross simplicity of the calculation...

 

[pwscottiv]

For the calculations I just basically figure out the mass of air you would have going though a 10 ft diameter tunnel at 120 mph, and calculate the kinetic energy per time that would be required to accelerate that air. I'm actually suprised I got as close to the published values as I did, considering the gross simplicity of the calculation...

Just curious. 1000HP is definitely a lot less than 4300HP though... Especially if I'd be paying for the power.

 

[Mech_Engineer]

Just curious. 1000HP is definitely a lot less than 4300HP though... Especially if I'd be paying for the power.

BUT- what's the diameter of the wind tunnel that can go up to 180 mph?

 

[pwscottiv]

BUT- what's the diameter of the wind tunnel that can go up to 180 mph?

There are a few that claim they can get up to 180mph, but http://www.bodyflight.co.uk/about/" is the largest at 16.4ft (5m) diameter. Which is also much more powerful than any other wind tunnel in the world at 4000HP. There is a larger diameter tunnel in Las Vegas, but their wind speed is only about 90mph (which kinda sucks).

 

[Mech_Engineer]

There are a few that claim they can get up to 180mph,

Well it takes power to go that fast, so my guess is they're a smaller diameter and higher in power than most. There's no escaping the required kinetic energy with an open loop wind tunnel (closed loop a.k.a. recirculating tunnels are different and can't be compared to open loop in terms of power requirements).

but http://www.bodyflight.co.uk/about/" is the largest at 16.4ft (5m) diameter. Which is also much more powerful than any other wind tunnel in the world at 4000HP. There is a larger diameter tunnel in Las Vegas, but their wind speed is only about 90mph (which kinda sucks).

My guess, at 16ft in diameter and 4000hp that wind tunnel's velocity is around 120-150 mph, am I right?

I'm betting that for just a "regularly" sized wind tunnel and "regular" air velocities of 100-120 mph you need over 1000hp, and it basically goes up as the square (or even cube) of the diameter and the square of the velocity from there.

 

[pwscottiv]

Well it takes power to go that fast, so my guess is they're a smaller diameter and higher in power than most. There's no escaping the required kinetic energy with an open loop wind tunnel (closed loop a.k.a. recirculating tunnels are different and can't be compared to open loop in terms of power requirements).



My guess, at 16ft in diameter and 4000hp that wind tunnel's velocity is around 120-150 mph, am I right?

I'm betting that for just a "regularly" sized wind tunnel and "regular" air velocities of 100-120 mph you need over 1000hp, and it basically goes up as the square (or even cube) of the diameter and the square of the velocity from there.

I'm an ME too, but I didn't bother doing the calcs... They're claiming that they get 180mph in the 16.5 foot tunnel... I doubt they're lying. Most tunnels are around 12 ft, have around 1200hp and operate up to 160mph or so.

 

[Mech_Engineer]

I'm an ME too, but I didn't bother doing the calcs... They're claiming that they get 180mph in the 16.5 foot tunnel... I doubt they're lying. Most tunnels are around 12 ft, have around 1200hp and operate up to 160mph or so.

Well 16.5ft diameter and 4000 hp back-calculates to 140 mi/hr for an open-loop tunnel, so either they're a bit optimistic in their top speed estimate, or its a closed-loop system (which is very possible considering it was a large military facility).

An open loop 12ft diameter tunnel with 1200hp would have a maximum speed of 116 mi/hr, achieving 160mph would require 3150hp. But again this is all assuming open loop systems, and I suspect most large and fast tunnels are probably set up as closed-loop systems due to the outrageous power requirements of open-loop systems.

 

[pwscottiv]

I doubt they'd lie about something like that... It's completely possible that it's closed loop. Also, if they couldn't achieve those speeds, skydivers like myself would have figured that out immediately.

 

[kamkaze]

Ok, the issue I see with the above scenario is that he is not calculating any drive gearing into the equation, for pure shaft power output he is right.

So what you will need are the following components;

A large stable mesh platform to mount several large fans under.

I suggest a series of 3-4, 8-14 foot fans. Each fan needs to have spacing of 2-3 feet to allow pressure to build up in between the fans. They will need to be mounted in a fairly airtight circular structure with 2-3 feet above them before the mesh for the bottom of the high pressure/speed tunnel.

The Air Intakes will need to be screened and well protected to avoid sucking in particles which, accelerated to 130-180 MPH, could kill someone.

A high horsepower V-8 engine connected to the right gear box can easily put out enough power to send 4 or 5 people 10-15 feet off the mesh if the tunnel is built open or closed above the fans, you will probably burn the equivalent of about 4-8 mpg of unleaded gasoline, depending on your engine. V-8 engines routinely accelerate (with proper gearing) 3000+ pound Nascars to well over 200 mph, 4 or 5 180-230 lb people in a column of air should be no problem

v/r
MAC

This this is a great project, would love to know if you go and do it.

A portable one costs 400k over in the USA, so that's the same price as 21k solo jumps from an aircraft.

I was also wondering, what is the best propeller design for this type of application?

Guessing that some designs will provide more wind-speed than others? So is it possible that the better designed props need lower power-input?

Seems the basic ones use 2 blade prop, direct diesel powered, and the more advanced use 3/4 blade props with electric motor powered by diesel engine(s).

Seems that they use a single prop, but was suggested that 2 props could be used.

Anyone more info on this? the static structure design above the prop look like a static fan.




can i build it with 4 4ft props with 4 50hp on each prop electric motors powerd by diesel generator? i think that 4 motors 2800rpm each can build more than enogh speed..
pls reply back because i am in the middle of buying the right props and motors

 

[kamkaze]

I only need to fly not more than 2 people i just need the right sized props and hp with the right rpm with the size of the tunnel

 

[Mech_Engineer]

can i build it with 4 4ft props with 4 50hp on each prop electric motors powerd by diesel generator? i think that 4 motors 2800rpm each can build more than enogh speed..
pls reply back because i am in the middle of buying the right props and motors

I already did the analysis for you: a 10 ft. diameter wind tunnel with a speed of 120 mph (approximate terminal velocity of a skydiver in the "flat" oriantation) would need 925 hp just for the acceleration of the air.

200hp of electric motors won't cut it. There's a REASON these indoor skydiving tunnels are so expensive...

 

[Exris]

This is manufacturer of wind tunnel with several projects. Prices starts with 130k euro and higher.

http://www.aerodium-technologies.com/en/products/models/

 

[Redbelly98]

Moderator's note: this thread is from August, 2008.

 

[pwscottiv]

Moderator's note: this thread is from August, 2008.

Yes, and I'm still going to build my own tunnel eventually , so keep the posts coming... It would help a bit if their website wasn't down.

 

[pwscottiv]

This is manufacturer of wind tunnel with several projects. Prices starts with 130k euro and higher.

http://www.aerodium-technologies.com/en/products/models/

LOL, ok, that's just plain WRONG teasing me like that... The website is down .

 

[Exris]

LOL, ok, that's just plain WRONG teasing me like that... The website is down .

Strange, for me it's opening without any problems.
Just try to google: aerodium technologies. They models shown in section - products.

 

[pwscottiv]

Strange, for me it's opening without any problems.
Just try to google: aerodium technologies. They models shown in section - products.

OK, so this is really strange... I can access the internet (obviously), and http://www.downforeveryoneorjustme.com/ says it's up, but I can't get there in FF, IE, or Chrome. Strange. Any ideas?

 

[pwscottiv]

lol, even more strange is that I can get there on my iPad :/

 

[Lancefield]

The kids and I have a plan. The tunnel could be an old silo, they are very strong and an old one would do. The fan can be an expired aircraft prop, they get scrapped after a certain amount of reshavings and can come in their housing which means you can adjust the pitch. I have bought some before for scrap prices. The engine can be anything from an old truck motor to the PTO of a tractor. The required horse power is still in question but species from the plane the prop came off should give some indication. The kids are going to have to get a job first I think.