Toward a muscle-powered weed whacker

I’ve been trying to construct a muscle-powered weed whacker. I am a fan of reel lawn mowers, and for the same reasons I like those — quiet, zero carbon emissions, no gas cans or cords to bother with, and so on — I would like a motor-less rotary weed whacker. If such a thing already exists, I haven’t been able to find one.

I do have a weed whip, a wonderful tool — this thing:

weed whip

It works very well in open areas, but it does not reach down into the rocks which we have as a border around our front flowerbed, nor into the gaps in the chain link fence around the side of our yard. Spots like this one:

DSCN1009

For these areas, I want a rotary weed whacker.

How would I make a manual weed whacker? With, I reasoned, the awesome power of a salad spinner. Or the type of gear that’s used in a salad spinner — one that converts linear motion into rotary motion. 

(There must be a name for this mechanism, but I haven’t been able to find it.)

Most salad spinners use crank handles, or push knobs, but I found one with a pull cord; the fine Prepworks spinner made by the noble people at Progressive International.

DSCN1023

This is the mechanism, cord, and flywheel-spinner.

So with a broom handle, some other wood, and a string as an extension for the pull cord — passed through eye hooks — I assembled this tool:

DSCN1019

And I tried it out using wire as the cutting edge.

Before I did this I cut away most of the disc, or flywheel, which spins around in the lid of the salad spinner. I assumed this would speed up the tool, and allow the wire to spin faster, but in reality I think there might be value to leaving some weight there so the disc can hold its momentum as a proper flywheel. In any case, I then attached some wire to the rotor so that two ends stuck out past the cover.

This thing did not work. The spinner would not achieve enough rpm to spin the wire fast enough to cut anything. 

Prototype 2: A new cutting method

So I took off the wire and instead mounted a thin strip of metal on the rotor. You can see it protruding at about the 5 o’clock position in the photo above. 

This time, it actually did cut grass. But nowhere near well enough to be useful.  In the next day or two I will post the Next episode: Prototype 3.  

Why am I writing and publicizing this, when clearly I am onto something that I can patent and use to earn untold riches? Because there are plenty of better tool-makers and mechanics out there who could do it more quickly, and the planet needs this new tool pronto. 



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