My idea for power to the train

[Bill Stanier]

So where does the lift come from?

The wings, as the aeroplane accelerates normally to take off speed.

 

[Ploughman]

Any thing in this article that could be used?
http://www.bbc.co.uk/news/science-environment-27659068

 

[Stompehh]

The wings, as the aeroplane accelerates normally to take off speed.

The lift comes from the aircraft's speed relative to the air. In this case the aircraft's speed relative to the surrounding air is zero as the treadmill does not move the air.

EDIT: We've been caught in a trap of looking at the problem in different ways and making different assumptions

Explanation here: http://blog.xkcd.com/2008/09/09/the-goddamn-airplane-on-the-goddamn-treadmill/

 

[JB_B]

The wings, as the aeroplane accelerates normally to take off speed.

I don't think so - if the (imaginary) conveyer belt really could make this bit true:-

"The faster the aeroplane moves forward, the faster the belt moves backwards."


then there will be no lift (but still plenty of weight) so the aircraft would stay firmly on the ground.

( think of the solution to x = -x for real numbers )

 

[Bill Stanier]

I don't think so - if the (imaginary) conveyer belt really could make this bit true:-

"The faster the aeroplane moves forward, the faster the belt moves backwards."


then there will be no lift (but still plenty of weight) so the aircraft would stay firmly on the ground.

( think of the solution to x = -x for real numbers )

You're making the classic mistake of assuming that if the belt moves backwards so does the aeroplane. It doesn't.

The aeroplane moves forwards powered by engine thrust in the normal way and at take off airspeed it flies. The backwards-moving runway merely makes its wheels spin very fast as it accelerates forwards relative to the air and relative to the (non-moving) ground either side of the backwards-moving runway!

I thought this one would hook a few!

 

[Class172]

Sounds like a problem for the Mythbusters...

 

[cjmillsnun]

Sounds like a problem for the Mythbusters...

easy done with a model aeroplane.

 

[starrymarkb]

I don't think so - if the (imaginary) conveyer belt really could make this bit true:-

"The faster the aeroplane moves forward, the faster the belt moves backwards."


then there will be no lift (but still plenty of weight) so the aircraft would stay firmly on the ground.

( think of the solution to x = -x for real numbers )

Aircraft are not driven by their wheels. So the aircraft would accelerate as normal by the thrust from the engines causing an equal* and opposite reaction. All the belt would do is accelerate the wheel speed, the limiting factor would be the wheel bearings being able to take the speed of 2x takeoff speed

*aprox there is some Noise+Heat

 

[sutty]

However- if the belt were to move the plane the other way and throw it down the runway, like a catapult shot on an aircaft carrier, you'd be well away. You'd get that lovely air moving over your control surfaces.

+1 for linking to XKCD

 

[DownSouth]

Assuming that the OP is only talking about hotel power rather than traction power, this already exists and has already mostly moved into the pages of history.

Not in the form of turbines on top of the train, but in the form of older loco-hauled coaches in some countries having axle-driven generators to allow them to be hauled by freight locomotives without HEP and without a dedicated power van being added to the consist. When moving, the axle generator provides all the power necessary for lighting, HVAC and other appliances while also charging up the onboard battery. When stationary, the lighting keeps going and the HVAC shuts down (or stays on if an external power supply is connected) even if the loco is uncoupled.

Most of the coaches in service with Great Southern Rail (Serco-owned operator of the Indian-Pacific, The Ghan and The Overland) were originally fitted with axle-driven generators and batteries, but since then they have all been converted to take HEP from the loco (the batteries remain, to provide lighting only) or from an external supply while at a station without a loco attached as happens during the Adelaide and East Perth stops of the Indian-Pacific.

EDIT: I believe that HEP (Head End Power) is known in Britain as Electric Train Heat.

However- if the belt were to move the plane the other way and throw it down the runway, like a catapult shot on an aircaft carrier, you'd be well away. You'd get that lovely air moving over your control surfaces.

That still works on the assumption that the plane moves with the conveyer instead of the wheels simply rotating while the plane stays on the spot. An aircraft's wheel brakes are too valuable on landing to put them to hard work during takeoff!

To get any meaningful amount of assistance from a conveyor or catapult of some kind for a large plane (i.e. larger than the sort of fighter/attack or light transport planes used on an aircraft carrier) would require enormously heavy landing gear and stronger internal structures. That's a big problem, because every extra kilogram of landing gear is a liability being carried instead of a kilogram of revenue-earning cargo or a kilogram of fuel allowing an extended range.

The use of JATO packs on commercial airliners would be far easier, and also far more entertaining to watch.

 

[306024]

As last seen on Wacky Races I think.

Professor Pat Pending would be proud of some of these suggestions.

Let's see how successful the battery powered class 379 project is first, meanwhile it isn't windy today so my train will be cancelled. It opens up a whole new chapter of excuses for delays.

 

[Emyr]

A train carriage might have about 50m² of roof space (assuming 20m x 2.5m - most are slightly bigger than that, I know, but not all the roof space will be usable - and round numbers make the sums easy ), so being generous and assuming 160W/m² you could peak at 8kW from each carriage roof. From Wikipedia (yeah, I know) the lowest power consumption around for an EMU is a class 315 at 656kW for 4 carriages i.e. 164kW/carriage, so 8kW of PV on the roof won't go very far.

That's 656kW peak output though, what does a 315 take to maintain a 90mph cruise on a still day with normal clean rails?

 

[306024]

A very strong wind. They are 75mph units.

 

[Emyr]

So the cruising power to overcome aerodynamic drag and friction would be even lower!

 

[fairysdad]

Sounds like a problem for the Mythbusters...

They already did http://www.youtube.com/watch?v=YORCk1BN7QY

 

[gerryuk]

Professor Pat Pending would be proud of some of these suggestions.

Let's see how successful the battery powered class 379 project is first, meanwhile it isn't windy today so my train will be cancelled. It opens up a whole new chapter of excuses for delays.

Then surly its better to start looking at new ways to power trains now.
A whole new chapter will be opened up when informed that there are no trains as the world has run dry of oil.

 

[DownSouth]

A whole new chapter will be opened up when informed that there are no trains as the world has run dry of oil.

When the oil starts to dry up, the meek acceptance of the FUD peddled about nuclear power will dry up with it.

 

[Bill Stanier]

When the oil starts to dry up, the meek acceptance of the FUD peddled about nuclear power will dry up with it.

Exactly, but it's a pity we have to wait 'till then. We should be building modern (French-designed) nuclear stations now (actually, we should have started 15 years ago) and electrify all railways to use that clean power.

 

[colchesterken]

what they could do is. build a frame fit a big boiler to heat up water, big fire underneath, then use the steam. lile a kettle to drive pistons with cranks to drive the wheels
I read the price of coal has gone down by 40% since our american friends have been fracking,, bargain

 

[DownSouth]

what they could do is. build a frame fit a big boiler to heat up water, big fire underneath, then use the steam. lile a kettle to drive pistons with cranks to drive the wheels
I read the price of coal has gone down by 40% since our american friends have been fracking,, bargain

Even better, how about put all the messy coal and water and burning and heating into a big building somewhere and find some way to transmit the energy to the trains through some sort of supply along the route?