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-   -   The "Plane on a Treadmill" Question (http://cellar.org/showthread.php?t=12670)

tw 12-10-2006 12:04 AM

Quote:

Originally Posted by MaggieL
I think they're in danger of burning anyway. Their friction is the only path for the treadmill to transfer energy to the airplane, and they've been specifically designed *not* to do that, whereas the engines are designed specifically to do exactly what they're doing. So the proposed takeoff failure scenario has a power transfer through friction in the wheel bearings equal to the power output of the engines (less engine system losses, of course). So even in a smallish airplane we're talking 100-200 horsepower...which is about 150 kilowatts. How long before the wheel bearings fail from heat?

My auto inspection shop complains about the cost of their treadmill. $20,000+ to test hundreds of horsepower cars (a machine required by the state required and that has not purpose only years later). Same treadmills exist for Indy and F1 racers designed to test 500 and 800 HP engines. I think we can find those bearings.

Maybe we and the Russians could cooperate on buiding one for airports? Anything for world peace. And since we are using labrat's ass, then it would be methane powered. Reduced global warming. No tailwinds. Having tapped chuck norris, the reduction in bullshit story lines means no additional landfills. Clearly there are plenty of spinoffs from this original proposal including 18 pages of deep technical discusion that would make any Congressman proud.

MaggieL 12-11-2006 07:50 AM

Quote:

Originally Posted by tw
Same treadmills exist for Indy and F1 racers designed to test 500 and 800 HP engines. I think we can find those bearings.

Not quite the same thing. The dynamometers you speak of are purpose built to carry the load of a race car in normal operation. The "no-fly zone" treadmill must run fast enough to dissipate the equivalant of all the power of the aircraft engine[s] through friction at the landing gear bearings alone. (I grant you can postulate treadmills of any desired power handling capability; Heinlein certainly did--convincingly--in "The Roads Must Roll").

The bearings in question are the landing gear wheel bearings, not anything in the treadmill. They weren't built to do anything more than handle relatively short takeoff and landing rolls near the stall speed of the aircraft, and some taxiing around at speeds about as fast as a man can walk.

SteveDallas 01-28-2008 03:40 PM

I will probably be shunned for resurrecting this thread... but I had to bring to everyone's attention that this topic will be covered on "Mythbusters" this week.

Undertoad 01-28-2008 04:39 PM

Found recently

http://cellar.org/2008/planetreadmill.jpg

SteveDallas 01-28-2008 05:08 PM

1 Attachment(s)
Clearly in this case the plane will not take off . . . it won't get past the obstruction at the front of the treadmill.

lookout123 01-28-2008 05:22 PM

I think this treadmill was designed for landings only, Sleeve.

monster 01-28-2008 07:24 PM

They're thinking of installing one at Heathrow.

regular.joe 01-28-2008 07:32 PM

Help me Obi Wan!!! wow, my brain hurts.

I say no. If the plane is on a tread milbl, there is no forward motion....no Bernoulli effect.

Try this, same question different object...

An armored personnel carrier with full tracks, is driving down the road at 30 MPH. How fast is a track shoe touching the ground, centered on the vehicle moving and in what direction?

monster 01-28-2008 07:36 PM

Quote:

Originally Posted by regular.joe (Post 427910)
An armored personnel carrier with full tracks, is driving down the road at 30 MPH. How fast is a track shoe touching the ground, centered on the vehicle moving and in what direction?

Who the fuck cares -just run in the away direction. fast!

lumberjim 01-28-2008 07:39 PM

Quote:

Originally Posted by regular.joe (Post 427910)
Help me Obi Wan!!! wow, my brain hurts.

I say no. If the plane is on a tread milbl, there is no forward motion....no Bernoulli effect.

Try this, same question different object...

An armored personnel carrier with full tracks, is driving down the road at 30 MPH. How fast is a track shoe touching the ground, centered on the vehicle moving and in what direction?

don't they wear combat boots anymore?

lumberjim 01-28-2008 07:40 PM

if you mean the little bits of the tank tracks.....i thought they stayed still?

so ....0mph?

HungLikeJesus 01-28-2008 07:46 PM

Quote:

Originally Posted by regular.joe (Post 427910)
Help me Obi Wan!!! wow, my brain hurts.

I say no. If the plane is on a tread milbl, there is no forward motion....no Bernoulli effect.

Try this, same question different object...

An armored personnel carrier with full tracks, is driving down the road at 30 MPH. How fast is a track shoe touching the ground, centered on the vehicle moving and in what direction?

There's no such thing as absolute velocity - all velocity is relative.

Relative to the ground, the part of the track touching the ground is not moving. The upper track is moving forward at twice the velocity of the vehicle (60 mph, in this case).

classicman 01-28-2008 10:02 PM

ohhh HLJ is a smarty pants!

regular.joe 01-28-2008 11:49 PM

You Sir, get a chocolate cigar!

LabRat 01-29-2008 08:55 AM

Quote:

Originally Posted by SteveDallas (Post 427862)
Clearly in this case the plane will not take off . . . it won't get past the obstruction at the front of the treadmill.


My crush on SD grows stronger...


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