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How
is the function of the PowerSkip ?
The PowerSkip is mainly defined by a leaf spring,
which is controlled during deformation in that way, that the result is
a straight movement of the fixing device. (Fig 1 and 2)
With the PowerSkip functional principle a degressive
spring characteristic and a backward movement of the force
point during deformation is achieved. This supports the natural force
point movement in direction to heel at higher loads and allows the runner
to transpose his jumping energy optimal.
For a good handling during running and jumping
a low weight is essential. For this reason the PowerSkip is designed
strictly to extreme light weight criterions, else only used in aerospace
applications.
Because of the application of high strenght
aluminium alloys for the structural parts and the use of high performance
compound materials like E-glasrovings (as in rotor blades of
helicopters) for the spring, a total weight of 3.5 kg per each is achieved.
For comparison: The spring force is similar to a spring in the wheel suspension
of a small car. The sole weight of such a spring is about 3.5 kg.
The Model PowerSkip Pro is designed for
a maximum of convenience and performance. With the new, patented
kinematics it is possible to transpose the muscular strength of the
lower leg into forward speed when running and into jumping height when
the spring is pushed through until to the stop unit.
In Fig.3 the kinematics is shown as it happens
during a run. It can be seen, that the tilting of the foot is transposed
into a horizontal movement of the footlever.This allowes to run
faster than with the standard modell. In Fig.4 the PowerSkip is fixed at
the main structure to give an other view to the mechanics. Here it can
be seen, that only negligible relativ movement between the knee and the
kneebow occures. This avoids painfull bruises and allowes to run in an
natural
motion sequence. |
Fig.
1 |
Fig.
2 |
Fig.
3
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Fig.
4
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How
high is the durability of the PowerSkip ?
The PowerSkip is designed for professional use
and can be used durable in its main parts. However, it is not possible
to design every part in that way, when the weight criterion is critical.
For this reason some parts must be exchanged after a certain time. The
following list shows the lifetimes of this exchange parts on basis of the
current experience:
Sole: MTBF 50 hours (running on hard rough
surface)
The wear depends from the way of use and the
roughness of the ground. On soft surfaces the liftime is nearly unlimited.
Springs: MTBF 500 hours (professional
use, always bouncing to the limit stop)
The liftime of the spring depends from the number
and magnitude of the load changes on the one hand and from a statistical
factor of the material on the other hand. Because of this fact, there is
a high uncertainty in the MTBF number.
Note: Safety aspects are not touched, because
the spring wears out slowly by losing its tension more and more. The spring
never breaks into two parts and it never brakes without warning.
Bearings: MTBF 1000 hours (for E640 spring)
The life time of the bearing bushes depends from
the type of the spring and from the way of use. Weaker springs than E640
elongate the lifetime considerable.
MTBF = Mean Time Between
Failures
All data result from the evaluation of the current
sold PowerSkip´s and can change with higher experience. |
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