The "Plane on a Treadmill" Question

[tw]

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]

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]

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]

Found recently

[SteveDallas]

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

[lookout123]

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

[monster]

They're thinking of installing one at Heathrow.

[regular.joe]

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]

Originally Posted by regular.joe

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]

Originally Posted by regular.joe

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]

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

so ....0mph?

[HungLikeJesus]

Originally Posted by regular.joe

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]

ohhh HLJ is a smarty pants!

[regular.joe]

You Sir, get a chocolate cigar!

[LabRat]

Originally Posted by SteveDallas

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...