It'd only fly for a bit, since the wheels would leave the ground and slow it down a bit. We're straying into plane/conveyor belt territory here!
I was busy writing my hollywood screenplay in starbucks when i happened upon this thread.
Most entertaining.
if the pigeons spread their wings and held on to the perches - the truck would fly !
Omigod - if that could save even 1% of fuel consumption, the value of the diesel saved across an entire fleet of trucks would hugely outweigh the cost of birdseed required to feed the pigeons! The commercial applications are massive - if you could provide a one-stop solution for pigeon management to equip every vehicle with a flock and market it as a costsaver to fleet managers, it would be hugely profitable. The growth would be immense. Best of all, you could franchise the idea to have dual streams of income.
Tell you what, greyman - how does 60/40 sound to you? Obviously we'd need to attract mezzanine investment and eventually we'd have to float on AIM, but in the meantime, you and I could make MILLIONS!
Truck gets lighter = Myth! Busted... 😛
Without trawling back through all the posts, has nobody pointed out that this theory was put to test on the discovery channel show "mythbusters". I remeber watching it and the test was pretty convincing. It was back in March 2007. They put each wheel of a truck on load cells and managed to get 11lbs of pigions to fly in the back all at once, with no change in weight, although the readings where a little noisey. So to go a step further, they flew a RC helicopter in the back of the truck....no weight change.
[url] http://kwc.org/mythbusters/2007/04/episode_77_birds_in_a_truck_bi.html [/url]
Video here! [url]
LOL at Konabunny
Dragons Den here we come ?
African Swallow or European ones do you think ?
Sorry I've hardly been paying attention to this thread but I'm getting a general gist that someone is arguing that a bird flying around in the air is pushing the air down so that the air puts the same force on to the ground as if the bird was sitting on the ground?
Have you ever had an aeroplane or a helicopter fly overhead? Did your house collapse?
If you're talking about a situation where there is a truck, with a bird in it, then the reaction force the ground has on the truck is (bird + truck) x g. Then when the bird takes off the reaction force will increase slightly (by the amount needed to accelerate the bird - eg: the force from its legs). And then the reaction force will just be the truck x g.
Ok now that we have cleared that up.. 😀
(Basically air can not carry a force (if you will) all the way to the ground - the force will just move the air about a bit immediately by the bird, then turn into heat..)
But if the air obeys as an ideal gas, assuming the truck is airtight and the volume of gas cannot change, and if the truck is a perfect insulator, the pressure will rise with the temperature, until eventually the bird melts/is crushed/the truck explodes.
Grimy - you miss the point.
If the pigeons are flapping about in the truck, then sure the downdraught is equal to their weight so the weight doesn't change.
This is about the hypothetical situation where the truck is big enough for the pigeons to [i]glide[/i]. My assertion is that a gliding pigeon is slightly buoyant, so it'd be like putting a helium balloon in the truck...
PS sorry to break this to you but Mythbusters, whilst a great show, is often profoundly unscientific. And Adam and Jamie know it too, but it's glossed over 🙂
BS of the week.
oh the ironing.
I never meant it that way steve.
Is this going to become BS of next week too then?
I haven't read most of this but I get the jist.
An example that whilst not the same, illustrates the point.
You have a sail boat with a large sail. You have a large fan on the boat(petrol powered for arguments sake) you point the fan at the sail at full blast, but the boat will not move. Put the fan on another boat behind and point it at the sail, the boat will move.
Put the fan on the boat. Pointed away from the sail. The boat will move.
Do you understand why this is the case? Please don't make me explain! 🙁
On the other hand, what if they were swallows?
Funky Monkey - see Dunning Kruger. You're not understanding the problem I'm trying to address 🙂
A victim of my own success 🙁
Molgrips, I know the show dosnt exactly conduct experiments to the scientific n'th degree, but the experiments are usually carried out with sufficent accuracy to dispell certain myths, and even then, people will change the argument and still stand by some theoretical minute point thats almost imposible to dispell just to suit their own argument. I think Adam and Jamie do a fairly good job of testing out stuff in a "real world" environment and with what is reasonably practical circumstances.
I'd have thought that the blades of a helicopter cut through the air and create lift in pretty much the same way as a gliding bird anyway, dispelling that theory too. But i'm really not interested in arguing that one out....youll only change the argument again to suit your needs! 😉 😛
A fair few of the experiments have MASSIVE holes in them from the scientific point of view. Most don't tho, admittedly.
Helicopter blades are static and result in a downward current of air below the helicopter - unlike the bird.
I haven't changed the argument to suit my needs, wtf!? We discussed the original case and then I thought about a special case which might produce a counter-intuitive result, for amusement purposes.
Jeez, you just can't play intellectual games with some folk...
Sorry molgrips, I'm just having a little interllectual fun too!
Although I said I wasnt going to argue over the similaritys of a helicopter blade and a birds glide, I will debate it with you! 😛
The way I understand helicopter flight, is not as you describe. It does not fly as a result of forcing air down like a harrier jump jet, but as a result of foiled rotating wings cutting through the air, creating less density above the wing than bellow, and thus achiving Lift, not thrust. Much in the same way a plane or bird glides. So if the experiment showed no weight change for a helicopter flying in a truck, then, the prinipal of flight being the same for a bird, the same results would apply?
ne'er mind al.
look at it as a win instead.
Ok, well if we're gonna get into this.. 🙂
Aeroplane wings and presumably helicopter wings work with a combination of the Bernoulli effect (the low pressure above the wing bit) and just forcing air downwards by being angled up (the angle of attack of a plane wing is critical).
I suspect that it's a little different for a helicopter though because it hovers in place. The low pressure above the wing ends up sucking air downwards from above, and coupled with the angled blade ends up forcing it downwards. Because it's hovering, this sets up a column of air with momentum downwards which is what keeps it up.
I suspect that an aeroplane (and bird maybe) has more of a component of lift generated by the buoyancy of the low pressure area above the wing. Since the wing is moving forward through air all the time, the pressure differential will be only present for a short moment, and would tend to equalise after the plane's gone, there by resulting in less of a downward moving pressure wave...
But I really don't know for sure - any aeronautical engineers on here?
You could do the same experiment with a small radio controlled plane in the truck, and see if the truck got lighter...
Or a hot air balloon...
I cant argue with that theory molegrips, It certainly sounds convincing. I wouldnt like to put money on it either way?
Me neither 🙂
Anyone had a plane fly really low over them, and felt a downdraught?
That Might just be displacement - like if a lorry drives past you, theoretically there shouldn't be a downdraft, as the wing is being pulled upwards by the less dense air, as you said buoyancy - or where you stating that there is no downdraft? In which case i agree.
Back to the original topic and a thread on tubeless tyres was bound to throw up a gem...
Running kevlar beaded tyres makes the tyre less sturdy in hard cornering and more likely to come off is you get landing squint etc.
Yes! Kevlar stretches!
So does wire 😉
intense 5.5 crack all the time I read it on the internerd, David taylorford strikes again
Apparently there is a [url= http://www.singletrackworld.com/forum/topic/sanderson-frames ]Sanderson bike frame[/url] that both costs £550 and weighs 5.5lb. 😉
Who on earth would buy one of those?
seen it on the scales!
I'm sure you've seen a sanderson weigh 5.5lb on the scales. My medium gas-pipe one most likely does. I expect a 20" is a bit more as well.
So: heavy ones @5.5lbs, rrp £300-350
853 ones, max rrp £500. about 0.2-0.3 lbs lighter whatever the inaccuracies in the website blurb.
Don't see any for £550 at all.
Perhaps you should shop around a bit Al.
