Perpetual Motion or free energy devices 1

[jmw]

OK, I was browsing you tube and came across the Gravity plane.
It uses Helium for lift and compressed air for weight.
So, we start with the thing on the ground and then it expels compressed air which reduces weight and allows helium bags to expand and becomes lighter than air.
It climbs.
Then it uses compressed air to compress more air which collapses the helium bags and makes it heavier than air again.
As it dives the air flow drives turbine air compressors to recharge the compressed air banks.
When it gets too low it discharges compressed air to allow the helium bags to reflate, climbs and repeats.

It is, wait for it, environmentally friendly and uses no fuel.
OK, I'm sold, where do i get one?

http://uk.youtube.com/watch?v=0QZ1KzveIic

JMW

http://www.ViscoAnalyser.com

 

[MikeHalloran]

Woods Hole already built a moderately larger Sea Glider, and made no overunity or near-unity claims, but demonstrated impressive endurance:

http://www.whoi.edu/page.do?pid=7545&tid=282&cid=37008&ct=162

Mike Halloran
Pembroke Pines, FL, USA

 

[msquared48]

Personally, in my lab downstairs, I am in the process of deveoloping a chewing gum that gives back more energy than it receives. I hope to sell it to Washington to help counter Fillibusters, then to Dentists seeking to expand their practices to include complications from Tinitis. Next, teenagers and two year-olds. Looking for trial test participants. Must have OSHA insurance.

Mike McCann
MMC Engineering

 

[HamishMcTavish]

So the main differences between this design and an airship (goodyear blimp etc) are that

1) After an initial charge by using its props on the ground (not very windy there because of the boundary layer effect so could take some time)

2) it can then use buoyancy to increase altitude

3) After some point it uses the stored compressed energy to reduce the buoyancy and starts to free fall

4) it recovers the energy during the falling process via the props

It is still going to fly pretty much like an airship but instead the (vertical) flight path will be like a sawtooth. Losses in the system will mean that the altitude gained at each subsequent peak of the 'sawtooth' will be less (dont' know by how much)

Why not KISS and just put some solar panels on an airship to drive electric motors? Plus have some exercise bikes rigged to charge the battteries on cloudy days! ;-)

No more things should be presumed to exist than are absolutely necessary - William of Occam

 

[handleman]

So, what size of evacuated Titanium alloy hollow sphere would float in the atmosphere? density=4700 kg m-3, yield stress=1500 MPa, E=140 GPa (guessing that elastic buckling might be an issue)?

airdensity=1.22 kg m-3, airpressure=101325 Pa

Cheers

Greg Locock

C'mon, Greg, you've done 90% of the work...

1m^3 of air = 1.22kg
We just need a 1m^3 sphere whose mass is less than this.

Radius of 1m^3 sphere is 0.62m
Surface area of 0.62m radius sphere: 4.84m^2
Multiply surface area by thickness to approximate material volume, multiply by density. It was easier to punch into Excel and guess than to solve for thickness, but I got a thickness of 0.0535 as the maximum material thickness for neutral buoyancy in atmospheric air, assuming perfect internal vacuum.

Oh, and that's mm, not m. About 54 microns. Somewhere around the thickness of household aluminum foil.

And that's not counting any carbon nanotubes!


-handleman, CSWP (The new, easy test)

 

[jmw]

I'm not flying in anything with a fuselage the thickness of bacofoil. Sorry, but no.

JMW

http://www.ViscoAnalyser.com

 

[KENAT]

I think Mike picked up on something I previously tried to point out, some of the sites don't claim over unity, just impressive endurance/efficiency.

I'm pretty sceptical on the flying version with anything like current state of the art technology and it's confused by over unity claims but the sea glider version is interesting.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[MikeHalloran]

Handleman: You don't have to guess.
Remember Newton's Method?
No matter; Excel does.
Tools|Goal Seek



Mike Halloran
Pembroke Pines, FL, USA

 

[handleman]

I considered using goal seek, but guessing was still quicker (for me) since I don't use goal seek that often. It only took about four to get as close as I needed to.

-handleman, CSWP (The new, easy test)

 

[SnTMan]

okaayyyyy... How about that elastic buckling at .62m & 54 micron?

I don't think we're there yet.....

Mike

 

[GregLocock]

q~0.365*E*t^2*r^-2

q being the 'likely' pressure to cause elastic buckling in a thin uniform spherical shell under external pressure, according to Mr Roark, 15.2.22

So, the kitchen foil solution fails horribly.







Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[JStephen]

Note that where you have different updrafts, it is possible to keep a glider in the air a good long time, and cover some distance- but this isn't what the proposal is about.

 

[rb1957]

jmw,
"I'm not flying in anything with a fuselage the thickness of bacofoil. Sorry, but no." ... i guess you don't fly in small turbo-props (DHC-8, 0.032" thick fuselage skins; Canadair RJ, 0.06" fuselage; Bombardier GX, 0.06" fuselage) not sure about the A320 but it wouldn't be much thicker.

but, of course, a sphere 0.052" thick couldn't support an internal vaccuum; as other posters have posited, the compression would crush the thin shell, tho' it could survive in space (pR/t = 14.7*18.2/0.054 = 5ksi; exen as bi-axial tension it'd be fine)

 

[GregLocock]

I think the answer is no - but, in a thin spherical shell with internal pressure is there an elastic instability mode? It seems unlikely since any small deflection is self correcting.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[handleman]

rb1957, I think maybe you missed the units. 0.054 is millimeters. 54 microns. That's only 0.0021". The thing would collapse under its own weight in gravity.

-handleman, CSWP (The new, easy test)

 

[moltenmetal]

The nearest I've seen to a perpetual motion machine is that Global Warming thread...if you could harness the hot air rising there and put it to work, there'd be a tremendous source of free energy!

 

[rb1957]

yeah, handleman, i mistook "microns" for thousandths of an inch (fairly usual in US/NA) instead of millionths of a meter