Sunday, July 4, 2010

Universal Scythe

Is there an off-the-shelf scythe which can be adjusted to fit anyone, regardless of height?  Is this even possible?  The answer is "Yes".
Here is a method of blade attachment which, when combined with an adjustable one-grip snath, can be adjusted to fit any height person for virtually any blade (regardless of tang steepness).  

A one-grip snath can be made at home from hardwood lumber, as detailed on the ScytheConnection website:

To make this type of snath adjustable, the method of grip attachment can be changed from the mortise and tenon connection (shown in the instructions) to a bolted connection, using a hanger bolt to secure the base of the grip into a dado in the snath.  Some examples are shown at the ScytheConnection site, with dadoes made on the snath for two grip locations:

To make the snath adjustable to fit anyone, a number of dadoes (six or more) can be made on the snath for additional grip locations, and the total length can be more than six feet (with a longer rounded section for the left hand position).

Now that the snath can fit any person, it must now be fitted to the blade.  With this "Universal Scythe" design, the blade is bolted to the snath, requiring a hole in the tang of the blade.  Some blades already have a hole in the tang, such as blade #00 from the ScytheConnection catalogue, pictured here.  A hole can otherwise be drilled into the tang of a blade to make it work with this attachment method (I've previously had a local machine shop drill a hole in a scythe blade for a few dollars).

The chosen blade (in this case, the pictured blade #00) will have a certain tang steepness which in most cases will be different from the required tang steepness for a one-grip snath.  For details on the required tang steepness, refer to my previous post here or the discussion at:

The "Universal Scythe" design can accommodate a wide range of wedge sizes for adapting the snath to a specific user/blade combination.  In this example, let's use a blade with a tang steepness of 25 degrees (such as blade #00), and let's assume that a tang steepness of 45 degrees is required for a given user of the one-grip snath.  A 20 degree wedge (45-25=20) would then be used to adapt the blade to the snath and user.  

The blade and wedge are bolted securely to the snath using a special "Piesslinger patent" metal plate which has been modified for this purpose.  (The Piesslinger patent attachment was mentioned in a previous post here.)  This photograph show the modified Piesslinger plate, with the wedge and two bolts used for this example of the "Universal Scythe".  This method can accommodate a blade with a single hole and a wedge of any angle. With the two bolts tightened, this blade attachment is extremely strong.  No ring clamps are needed.

In these photos, the snath has been reduced to seven inches in length for simplification.  The snath section is left square at the blade end, since there is no need for partially rounding it. Because of the added angle of the wedge, the end of the Piesslinger mount needs to be bent to conform to the snath end.  It is not necessary to nail the Piesslinger mount to the snath, as it is held quite solidly without nails.

The wedge is connected to the snath by the two bolts. The lower bolt also holds the blade against the snath. Since the bolt is a quarter-inch diameter, and the tang hole is a half-inch, a piece of white nylon bushing is used to hold the blade solidly.  

Since the nuts protrude from the snath at an angle, the tops of the holes were countersunk to provide flat contact with the wood.

A washer is used under the blade, and smaller washers and lock washers are used with the two nuts.

A groove was made in the back of the wedge to hold the knob of the tang.  Hafting angle considerations for the specific blade will influence the location of this groove.  I cut the corresponding end of the Piesslinger mount with a hacksaw and bent the metal flaps into the groove to hold the knob more securely.  I figured that this would be stronger than simply cutting a keyhole into the metal (i.e., cutting away the flaps).  The flaps were easily bent by putting the cut Piesslinger mount and wedge into a vise, and gently hammering the tang knob into place.

When the blade is being mounted to the snath, the upper bolt is first attached (since this is located under the tang near the knob).  Then the Piesslinger mount and tang are put into place and the lower bolt is attached.  The nuts are tightened with a small wrench.

A wide range of wedges with various angles can be made available for a precise fitting of the "Universal Scythe" to the user.  This type of blade attachment can also be used for other snath designs, including the Oregon Snath (described here).

(Source:  Photo of  "Spiral Galaxy M100", from NASA, HubbleSite,