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Magnus Effect

Sun, 29/08/2010 - 12:08 — mnd22
Introduction
Catapulting a spinning carboard tube through the air in such a way as it generates lift.
Useful information
Kit List: 

Cardboard tube - this is something like the centre of a kitchen roll, or can be made by rolling up card. We found that the rolled card option had a tendancy to collape in the middle, so it may require reinforcing by either using double sided sticky tape between the layers, or by putting ping-pong balls inside as reinforcing
Elastic - about 1.2m or so
A table to attach the elastic to
A source of a water stream (jug or tap or something)
- we have a water carrier for this if ther is no tap
A spoon

Explanation
Explanation: 

Catapulting a spinning carboard tube through the air in such a way as it generates lift, and will fly across the room. This can be compared with spoons bending a stream of water and why a tennis ball's spin will affect how it flies.

Cylinder

The basic idea is to attach the elastic to one end of the desk, stand at the other and roll it up around the cylinder in such a way as it will have back-spin and then release it.

There is a definite knack to making the cylinders fly, as far as I can work out it involves rolling the elastic up keeping the cylinder in the same place, so the deepest elastic is the loosest, so it will release nicely. You also have to make sure you wind the elastic right in the middle and release the cylinder cleanly. IF it works it flys really bautifully.

Spoon

Just put the convex side of the spoon into a water stream and you should see the water bending around the spoon and be able to feel a force on the spoon

Explanation

The explanation rests on the tendancy of streams of fluids to stick to a curved surface (I think essentially because if the air goes in a straight line it will start to drag the air out of the pocket that it leaves. This will reduce the pressure in the pocket, if this pressure is small it will drag the main stream around - the coanda effect, if it is large it will cause air to be sucked in from different places, producing turbulence.

The change in the direction of the flow through a Newton's law causes a force on the spoon

This explains the spoon, the cylinder has the spin, this means that the air going over the top is dragged along with the cylider by friction, and the air at the bottom is slowed, this means that they meet and seperate below the centreline, so the flow is moved downward and there is a net upthrust

Flight

This is a better explanation of how wings work than the standard bernouli explanation, the wing is designed to change the direction of the flow of air downwards to produce lift. A stall is when the air going over the top of the wing becomes unattached and turbulent, so all of a sudden the plan looses half of it's lift and if it is too close to the ground crashes

Uses

NASA have tried to use this effect by attaching spinning leading edges to slow observation planes, and www.fanwing.com have built combine harvester style plnaes (to get more grip) which work on a similar principle.
Tennis ball, football etc swerves normally work on this principle

Risk Assessment
Date risk assesment last checked: 
Fri, 30/12/2011
Risk assesment checked by: 
mnd22
Risk Assessment: 
DESCRIPTION Launching spinning cardboard tubes, with elastic so they generate lift.
RISKS
  • Tube or elastic may hit someone, but not too hard
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    ACTION TO BE TAKEN TO MINIMISE RISKS
  • Try to make sure the tubes are shot into space which isn't crowded, and that there is noone in front of the elastic
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    ACTION TO BE TAKEN IN THE EVENT OF AN ACCIDENT
  • Call first aider in event of injury
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