[Closed] could STW do better?

Ever ridden a recumbent? It's really not very powerful, as you can't use your upper body.

I think recumbents are fast because you significantly reduce your frontal area.

Hijack - have yo been to that recumbent shop in Erding?

However, yes I think we could do better tbh.

Position does look ridiculous, though I wonder if the aerodynamics of the will matter much.

You'd think they'd use a fit cyclist...and make it controllabvle.

See (possibly):

(*I can't see lots of stuff at work)
but anyway search on Gossamer Albatross, be interesting to see how the technology has moved on

looked more push powered to me.

The take off seemed to depend more on the bloke pushing it than the guy pedalling.
Stick Graeme Obree in it and you might have a winner.

I would start off with a top spec road bike I think. I wonder if you'd benefit from having drive to the wheels to help takeoff?

cynic-al - Member
Position does look ridiculous, though I wonder if the aerodynamics of the will matter much.

You'd think they'd use a fit cyclist...and make it controllabvle.

You, McMoonter and Stoner should build one. 😉

They always use very long propellors for these things - is that better than a fast rotating smaller one? I think I would be tempted to include a battery and motor that can be charged from pedal power, to provide a boost for takeoff and climbing. A pedal-electric hybrid. And I'd use a load of cowlings to improve aerodynamics.

Control surfaces would be mandatory I reckon too, to allow use of glider techniques.

I'd want to start with a stiff chassis in a recumbant position. I reckon that's still the best way of getting max power - I'm thinking of the leg-press machine from the gym. Aerodynamics are going to be important if it's going to be any more than a hop and a skip.

What speed does he need to be going to lift off?

needs a treadmill

is that better than a fast rotating smaller one?

IIRC, props that go too fast for the airspeed aren't very efficient (they just churn the air rather than really moving it as I recall). Big and slow for that type of plane.

Speed looked like maybe <10mph? I doubt the aerodynamics of the pilot aren't going to matter too much.

Pilot has to sustain sufficient power to gain some height so I don't think using traction to assist take-off will help.

HTS, I am flattered 😀

They did this on scrapheap challenge a few years ago - it was a UK vs US special.... I seem to remember a beardy chap getting properly up in the air and doing turns and all sorts.

Than those machines were made in a scrapyard.... make this effort look a bit poxy.

*goes and googles for clip*

*returns from googling*

Nah... theirs had engines:

Surely it's a fairly redundant idea, seeing as you can fly a long way in a glider with no power (other than a helpfull landrover/winch/hill)?

And would the design not work better with a tandem (or more?) seing as you wouldnt need mroe 'plane', you'd just go faster with the added power and create more lift that way, just needs to be strong enough to hold double the weight.

On that note, who'd be better the Schelcks (or any two other good climbers, say 125kg between them?) or Chris Hoy on his own (probably the same overall power, but less weight and a limited range), or a Schleck and a Hoy, Hoy to get it off the ground and climb, Schleck to fly the thing?

Ever ridden a recumbent? It's really not very powerful, as you can't use your upper body.

?? Last time I rode one I felt it more powerful as I could a) hold my body in place with my arms and b)push against my lower back. When riding on an upright bike I am limited by body weight unless I want to strain stupidly agains the bars which is inefficient.

Surely it's a fairly redundant idea, seeing as you can fly a long way in a glider with no power (other than a helpfull landrover/winch/hill)?

And would the design not work better with a tandem (or more?) seing as you wouldnt need mroe 'plane', you'd just go faster with the added power and create more lift that way, just needs to be strong enough to hold double the weight.

Not necessarily - in simplistic terms you'd need twice the wing to give you twice the lift, which would mean twice the drag, cancelling out the point. You could of course gear it to twice the speed at the prop and use the same wing, but then your drag increases with the square of the speed so you'd need more than twice the power to get twice the weight up.

When riding on an upright bike I am limited by body weight unless I want to strain stupidly agains the bars which is inefficient.

thats where clipless pedals come in.

Not necessarily - in simplistic terms you'd need twice the wing to give you twice the lift, which would mean twice the drag

This is turning a bit 'plane on an conveyor belt' but the advantage tandems have is that they provide twice the power for less than twice the aero drag so for a plane, it'd really depend whether the majority of drag is from the wing or from the rider(s).

Surely it's a fairly redundant idea, seeing as you can fly a long way in a glider with no power (other than a helpfull landrover/winch/hill)?

Hence my pedal/hybrid assist glider idea.

the advantage tandems have is that they provide twice the power for less than twice the aero drag so for a plane

That's fine on the ground, but in the air you need twice the lift which means twice the wing or twice the speed, and that has implications on drag and also weight still further, since bigger wings are going to need to be a lot sturdier to stay rigid.

Happened upon BGtT last night and they were doing all the work up for this, was actually pretty interesting, and not entirely insulting to those who have a vague idea about it.

They reckon he'll have to sustain 350 watts to achieve and maintain lift. Now... that's not far off my 5 minute power output, I'd not want to have to stay above that or die! His FTP was a not entirely embarrassing 270 watts (IIRC), and I think he weighs c72kg, so FTP of roughly 3.75 w/kg, which isn't that bad, so he's got a bit of fitness.

Fair play to him I say, I reckon there'll be bigger problems that power generation though frankly!

Think the limiting factor for propblades is when the tips start to approach the speed of sound, as well as obviously structural and power requirements.

So if it's slow and light, you can go with long blades.

And I'd definitely go with a recumbent, possibly with a fairing, and powered wheel(s).

Ooh, found an image of the pedal-powered airship we build at university:

[img] [/img]

Lot easier to get off the ground 🙂

Only in the right conditions.

Yes, but seeing as the average* person is going to struggle to output 400W for more than half an hour, and a tiny little 2 stroke engine will put out 10hp easily all day long

*well, significanlty above average but not in the TDF cyclist, most of us are going to struggle with half that!

What is the point of wheel power when it's gone when you are in the air?

http://en.wikipedia.org/wiki/Gossamer_Condor

I saw the Gossamer Condor at the Smithsonian last year, and remember watching it's construction and development on Horizon as a kid. It was hugely inspiring. His cross channel flight was awesome. The pilot nearly exhausted himself trying to stay too high above the water, descending in defeat he found he could generate more lift for less effort only a few feet above the water.

And I'd definitely go with a recumbent, possibly with a fairing, and powered wheel(s).

Light weight is everything if you're trying to leave the ground. Fairing? More weight. Recumbent? Longer frame, more weight. Powered wheels? Extra transmission, more weight. It's a marginal proposition to get off the ground at all. Pilot aerodynamics also pretty moot at a jogging pace, which is all you're going to be doing.

Look forward to seeing the programme 🙂

thats where clipless pedals come in.

Yep, but clipless can also be applied to recumbents, so it's a moot point.

What is the point of wheel power when it's gone when you are in the air?

A vast amount of the energy required to get you flying will be in the acceleration of your mass. It's a lot easier to accelerate mass when you have physical contact with the ground rather than through fluids.

I would like to see a breakdown of the value of fairings vs their weight. If you could go significantly faster you could use less wing and therefore save weight on that.

I saw BgtT last night too. Kind of interested to see what my wattage would be. At my weight it's a moot point, A380s struggle to lift of with me on-board.

I think it is beautiful, and a great attempt - he was good on last nights programme so looking forward to seeing the rest.

But in the spirit of STW....

Would he have taken off if he was on a treadmill rolling towards him at a speed identical to his ground speed....

The tandem theory has legs I reckon. Double power without double the drag would work pretty well (if you don't think that's right, google ASH-25 and let me know why that doesn't have inferior performance despite massive wings and 2 pilots). However, clearly the one person design does work. As a side note, flying low in ground effect, you can cover an astonishing amount of ground for no height loss in a glider, I'm amazed the pilot of the channel crosser hadn't been told that, every competition glider pilot has experienced it for themselves and it's certainly kept me out of a field a few times!

HTS, I am flattered

Don't be. It'll be made of gas pipes and wood and covered with solar panels. Damn thing wouldn't move, let alone fly. 😉

Don't forget the carbon fibre...

It's a lot easier to accelerate mass when you have physical contact with the ground rather than through fluids.

But you have to maintain the speed as you lift off...

True - but most of the work is on takeoff in a plane, isn't it? Takeoff and initial climb. So if you can save a load of energy in the first 30s you should be better placed to put the work in to gain decent altitude.

I am thinking a Graham Obree style position would be good - there's a reason on-foot sprinters power off like that, and he did rather well riding like that if you remember. Plus, you could put your feet down to land like a hang-glider does, so you'd not need fixed undercarriage. You could take off on some kind of skateboard arrangement. Only if you weren't going for the powered wheels takeoff.

Don't think powered wheels would add much weight, you've already got the wheels and most of the transmission, adding a bit more chain isn't going to change things that significantly. Once you're up to speed takeoff will be a lot easier. I suppose with all those helpers they're possibly unnecessary, though.

Stalling as soon as you leave the ground? No thanks.

For that reason I'm out. 😀

You wouldn't stall. You'd cycle nicely along to take off speed then redline, rather than redlining just to get moving. It'd mean you could start off without anyone supporting you too, because you'd quickly gain enough speed to avoid falling over.

Carrier-style steam catapult 🙂

Or, to maintain human-powered credentials, enormous bungee cord and pedal-driven winch.

coffeeking - Member

Ever ridden a recumbent? It's really not very powerful, as you can't use your upper body.

?? Last time I rode one I felt it more powerful as I could a) hold my body in place with my arms and b)push against my lower back. When riding on an upright bike I am limited by body weight unless I want to strain stupidly agains the bars which is inefficient.

This = you can get better power from a recumbent riding position or one where yo have something solid to push against.