Artemisia Missile Combat


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Make an Aluminum Crossbow Prod 
by Bartholomew Hightower

You need to check around with some of your local fabrication shops, and get them to order in some 1.5" x 0.25" 7075 T6 51 aluminum bar. I usually find this in 12' lengths, and get it cut into 3" lengths. Make them cut it -- not shear it.

I usually have a small curve rolled into it, but that isn't really necessary. Some will even go so far as to say that rolling the bar will reduce its lifespan. I set a recurve into the ends by clamping 2-3 inches into a padded vise and giving it the old heave-ho to get about a 35-45 degree angle on the end.

Some crossbow makers (good ones) grind a nice taper on the prod ends, but I just leave 'em straight.

For the tangs, you need a small angle grinder and a 'non-ferrous' grinding wheel for it (the regular grinding wheels just get gummed up with aluminum).

Check out the sketch. In (1) the bar is marked with some guide marks using a pencil or a sharpie marker. I would give you dimensions if I had them, but I've always just eyeballed it. I would guess the horizontal line is 0.5" to 0.75" from the end of the bar.

Use safety glasses, gloves, a shop apron, and a padded vise for the grinder work.

In (2),  the first two cuts have been made. It's useful to watch the line as best you can. In (3),  the two shoulder cuts have been added.  Be careful here.  It's easy to get the cuts lower than you want. Aim high; you can always trim more later. 

In (4), the corners have been rounded with the angle grinder. I try to keep the grinding wheel orthogonal to the bar, cutting only the profile, and leaving the rounding the of the face edgesfor the file work.

For filing, I use a couple of regular old files. A flat and a round chainsaw file. Keep a wire brush handy for cleaning the files as you work. I start with the string guides. (5) shows the side toward the shooter, (6) shows the side from the front of the bow. It is important that there be a smooth, continuous curve from the front to the back, else it will chew right through your strings.

After the string guide is filed, I go back and round over the tip and shoulders with a flat file. Finally, I switch back to the round file to round over the part that I can't get with a flat file, and to smooth the transition between the string guide and the rest of the tang. I do this by starting with the round file in the string guide and then pushing it diagonally toward the outer edges (forward and sideways at the same time. Try it, and you'll see what I mean.

I finish off the tangs by polishing on a buffing wheel loaded with a liberal amount of emory, paying particular attention to the string guides.

After you are satisfied with the polished prod ends, you may wish to cover your prod with rawhide or leather.  I use a thick upholstery leather for this task, because I like the way it beefs up the look of the prod.  Others have used rawhide coverings for this same task, which can provide a very strong covering with a lighter weight penalty.

I start with a piece about 36" long.  The width varies depending on the individual piece of leather, but 4" or slightly less is about right most of the time.  I lay the piece of leather on a soft pine board, then fold it lengthwise and use a few spring clamps to keep it that way.  I start at one end and use an awl to push a hole through both layers of leather along the edge. 

After the holes are punched, I sew it onto the prod using waxed cord and a bigassed upholstery needle.   I don't worry about getting it too tight as I am initially sewing it on.  Having it slightly loose is useful for moving the seam around the way you want it.  After the first pass, I go back and pull all my stitches tighter.

I string it with a 34" string.  I usually end up with about a 90 pound pull at about 10.5 inches of draw, which you can test with a spring scale like this one.