Tweel Airless Tire

For more than 100 years, vehicles have been rolling along on cushions of air encased in rubber. The pneumatic tire has served drivers and passengers well on road and off, but a new design change all that - the Tweel Airless Tire.


The name is a combination of the words tire and wheel because the Tweel doesn’t use a traditional wheel hub assembly. A solid inner hub mounts to the axle. That’s surrounded by polyurethane spokes arrayed in a pattern of wedges. A shear band is stretched across the spokes, forming the outer edge of the tire (the part that comes in contact with the road). The tension of the shear band on the spokes and the strength of the spokes themselves replace the air pressure of a traditional tire. The tread is then attached to the shear band. The Tweel looks sort of like a very large, futuristic bicycle wheel




When the Tweel is put to the road, the spokes absorb road impacts the same way air pressure does in pneumatic tires. The tread and shear bands deform temporarily as the spokes bend, then quickly spring back into shape. Tweels can be made with different spoke tensions, allowing for different handling characteristics.

Flying V????

 

Most of us have probably seen large groups of birds flying in formation. These large groups of birds will typically fly in a large "V" shape with one bird in the lead and others trailing behind in two lines.

This formation flight is followed by the birds for two reasons.They are,

First reason :

                   The shape of the formation reduces the drag force that each bird experiences compared to if it were flying alone.

Second Reason :

                      Is that may explain why birds fly in formation is that this orientation allows the birds to communicate more easily. The V formation provides the birds with good visual contact of each other to keep the flock together. This communication minimizes the possibility of losing birds along the way as the formation crosses vast distances during migration.

Results:

Studies have estimated that a flock of 25 birds in formation can fly as much as 70% further than a solo bird using the same amount of energy.

By spacing themselves apart properly, birds can achieve optimum positions that reduce the drag of every bird in the formation. However, not all birds benefit equally.  Apex bird has to work the hardest since it flies into undisturbed air. The upwash(upward thrust) that this bird creates improves the aerodynamics of the two behind it, and these two further improve conditions for the next two birds in line. This means that birds in the middle experience less drag than either the lead bird or the bird at the end of each line.

 

Interesting Point : The birds at the apex and aft positions may interchange their positions after some time so that the flock can migrate to a longer distance.

Degrees of Freedom

Degrees of Freedom(dof)

“No. of parameters needed to specify completely the spatial pose of a rigid body”

A rigid body in ‘d’ dimensions has  d(d+1)/2 no. of degrees of freedom.

d(d+1)/2        =         d          +           d(d-1)/2

           (dof)                 (translations)          (rotations)

• A non-rigid body has infinite no. of dof.

In 3 dimensional space for a rigid body there are 6 dof.

 

• 6 dof:

1.  Moving up and down(heaving)

2.  Moving left and right( swaying)

3.  Moving forward and backward (pitching)

4.  Tilting forward and backward (pitching)

5.  Turning left and right( yawing)

6.  Tilting side to side (rolling)

Dof for a system: A system is defined to be a set of rigid bodies.Its dof can be calculated by

Dof of system = (Dof of bodies) –(internal constraints they may have on relative motion)

Here the dof represents the no. of parameters needed to specify the spatial pose of the system.  

Eg:1

A human arm has 7 dof.

    I.        Shoulder----3----pitch,yaw,& roll

   II.        Elbow--------1----pitch

  III.        Wrist----------3---pitch,yaw,roll 

·         Only 3 of these movements would be necessary to move the hand to any point in space. But people would lack the ability to group things form different angels or directions. 

·         Total no. of dof is 6 

·         A robot/object that has mechanisms to control all 6 physical dof is said to be holonomic 

·         An object with few dof is said to be non-holonomic. 

·         An object with more controllable Dof( than total dof) such as human arm is said to be redundant.

Eg:2

An air plane is a non-holomonic. Since it has only 4 dof

                    I.        Forward motion

                  II.        Rolling

                III.        Pitch (only some extent)

                IV.        Yaw

Eg:3

A car has max. of 15 dof

15 = 6 DOF for the car body+ 1 for each wheel's vertical motion+ 1 for each wheel spinning + 1 for the engine

Eg :4

A human wrist has 27 dof .

• It is the most complicated design that ever made on the earth and it is the system which has the max. no of dof.

•  4 in each finger ( 3 for extension and flexion and one for abduction and adduction)                                     =                                4 x 4

•  the thumb is more complicated and has 5 Dof     = 5

• 6 DOF for the rotation and translation of the wrist =  6

                                                                                           -------------

                                                                                                 27        

                                                                                         -----------              

• Human Hand Not only design but also animating the wrist movements is so difficult such that they animate with only 12 dof neglecting the 15 other dof.

• It clearly unclouded that He is the best designer than any one who born on the earth