Andy Wardley
<abw@kfs.org>
This is the Tetrahedral Active Bridle. It is the natural
extension of the Dihedral Active Bridle to 3 dimensions: effectively
adding an Activator leg to each consequetive pair of bridle legs.
Like the Dihedral Active Bridle, the Activator legs may be separated
and placed at different distances from the tow point to acheive
specific effects. Naturally, the lengths of the legs may also be
adjusted. The configuration shown here, with all three Activator legs
attached together, is ideal for trick kites and can produce some
radical freestyle tricks.
This bridle configuration was originally named the Trihedral Active Bridle. Wim Hendrix was inspired by the original Active Bridle design and has independently developed a configuration based around the same shape (which he correctly identifies as a Tetrahedron) called the Tetrahedron Bridle. In acknowledgment of Wim's efforts, and in keeping with his chosen naming scheme, I've renamed my configuration the Tetrahedral Active Bridle. Thus, the similarity between the two is reflected in the name, but they retain their own individual identities and specific implementations. Wim describes his Tetrahedron Bridle at http://studwww.rug.ac.be/~whendrix/. The term Trihedral Active Bridle is now used to collectively describe all the various 3-dimensional designs shown here.
Mark Reed has also been undertaking some similar research but details are still sparse. I'll have to find out more from Mark.... Further detail is likely to be found (in time) at http://www.prism.com/
The Tristar Active Bridle shown here consists of three legs,
one attached to each bridle leg, that are then joined together at one
central point. Each leg is effectively an Activator controlling the
movement of the bridle leg to which it is attached. Because the
Activators are joined together, they exert negative feedback on the
system by each one naturally resisting (as a result of the tension in
the line) the movement of the other Activators. The Activator system,
known affectionately as the Space Frame in reference to the
kite on which it was originally developed, the Benson Outer
Space, maintains an unparalleled stability in the bridle as
constantly self-adjusts to balance the pressures exerted on the kite.
The length of each Activator leg can be adjusted, as can its position on the bridle line from the tow point. A well-balanced Space Frame positioned some distance from the tow points, and pulling the bridle lines in only a little, will generally produce a stable, responsive kite that is not only more precise but also capable of increasingly radical tricks.
More extreme positions, with Activators of shorter or uneven lengths, or placed at different distances from the tow point, will produce more radical effects. In general, shortening an Activator leg will move the centre point (where the Activators join) closer to that bridle leg. This will increase the amount of tow point movement (with the bridle under tension) in the direction of that bridle line. Moving an Activator away from the tow point will typically bias the tow point away from that bridle line. It may also have a shortening effect to increase the potential movement in that direction.
See the Dihedral Active Bridle page for further details on the effects of length and placement of Activators.
Permission is hereby granted for any person to use or modify the Active Bridle for any purpose, under the following conditions:
This document is © Copyright 1998 Andy Wardley. All Rights Reserved.
You may freely copy, mirror, print or distribute unaltered copies of this document, provided that no charge is made for it. Please contact the author if you wish to reproduce the document in a commercial publication or in an altered format.