This implement looks like a standard weed-whacker, except the abrasive-coated string is a loop.

The loop is attached, at one slightly reinforced point, to a curved spring-steel wire, which other end is at the motor spindle. When the motor turns, the weight of the wire extends it horizontally out to six inches, quickly pulling the one foot diameter loop into a very light duty circular saw.

Unlike the radial-string type where the cutting surface is only the last half inch, the entire circumference of the lasso is available to quickly shear through the greenery. As well, there being no fatigue points, each loop should last quite awhile.
-- FlyingToaster, Jul 18 2013

Fun idea, but I don't think it will work as well as you hope.

Since it is not symetrical, the spinning loop will have a wobble to is (like a spinning lasso does). That means one area of the loop will get more wear than another area of the loop.

When you are starting it up, how do you get it to spin like a lasso rather than having the loop get flung around at the end of the string, effectively creating a string that is 6" + pi*12"/2?
-- scad mientist, Jul 18 2013


Actually it wouldn't have an inherent wobble since the handle is wire and not string. A springy wire to be sure, but the RPM is chosen to match the wire's properties such that when it's pulling a string, the distance from center to circumference (horizontally across the plane of the loop) is half the diameter of the loop.

Yes, if you jabbed the trimmer far into the weeds, the point where the wire meets the loop would tend to be a bit more resistant to being pushed inwards, but the wire doesn't weigh very much.

As far as the startup is concerned, the spring steel wire is slightly curved to begin with and, when the strimmer's started, centripugal force will pull it out to its full radius which, non-coincidentally, is half the diameter of the loop.

So, starting with the loop dangling from the wire, slightly off the axis, the wire starts to spin and, as its horizontal radius quickly increases as previously noted, pulls its end of the dangling string outwards. The other end of the string flips up _on the other side of the axis_, the string spreads out and becomes a lasso pulled around circumferentially.
-- FlyingToaster, Jul 18 2013



random, halfbakery