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PART 2 THE ROLLER NUT TRIGGER IN A GERMAN
HUNTING CROSSBOW
When it comes to making crossbows, the older styles of stocks were
similiar, in the forearm area. But it is up to the individual how the back of
the stock ends up looking. Most of the older styles were just straight and plane
looking, I like to add different shapes in mine, but it is up to you how you do
yours. In the crossbow building, part 1, I showed you how to rough out the
stock. Although the stocks in part 1 and 2 look different, the
real difference, lies in the trigger system. This one has a roller nut
trigger system, which is alot more complex and more difficult to build. The
first thing I do, is to determine where the string will be released on the top
of the stock. I make a mark on the stock. On this crossbow, I am using an
1 1/2" roller nut. So I will measure down from the top of the stock from the
mark 1 1/4" and make another mark, then I will use a 1 1/2" paddle bit to remove
the wood 1 1/4" deep leaving a 1/4" wall on the side of the stock. Then I
measure 1/2" on each side of the 1 1/2" hole toward the front of the stock
and the back of the stock, and about 3/8" below the 1 1/2" hole toward the
bottom of the stock. Then with the use of a wood chizzel, I remove the wood from
the inside of the marks, at this point this is what your stock should look
like.
Now to cut the roller nut. I use a 1 3/4" hole saw to cut
through a 1" thick tight grained white oak board. The hole saw leaves a 3/16"
hole in the center of the roller nut. I thread a 3/16" x 2" bolt through the
center, then tighten a 3/16" nut down against the roller nut. I then insert the
rest of the threaded end of the 3/16" bolt into the chuck of my drill press.
Then with 80 grit sand paper, I slowely work the roller nut down until it
fits into the 1 1/2" hole snug. Now you have to determine the way the grain is
running in the roller nut. With the grain running up and down, mark one end
the top and one end the bottom. Then measure 1 1/4" down from the top, and
draw a 1/4" line. Then make another line at a 90 degree angle. Make a duplicate
set of marks on the other side. Then connect the line on the top and the lines
at the opposite end at the 90 degree marks. Then with a fine tooth saw, I cut
through the top of the roller nut with the grain, down 1 1/4". Then I go to
where the 90 degree marks are and cut against the grain until I reach the 1/4"
mark. Then with the roller nut top turned up, I measure across the 1" roller nut
from one side and make a mark 5/16" in, then I measure from the opposite side
and make another 5/16" mark in. Then with a saw, I remove the wood between the
2 5/16" marks. Here is a picture for an example below.
Now lay the roller nut on it's side. Draw a line from the top side to
the bottom side, the line should be with the grain, on the side where most of
the wood is removed, we will call it the right side of the roller nut. Now we
will turn the roller nut with the bottom up and draw a line straight across the
1" bottom side. Now measure 5/16" from one side then make a mark, then measure
5/16" from the opposite side and make another mark. Now with the bottom side
turned up, imagine a slot cut between the 5/16" marks to the line that
crosses the 1" bottom 1/4" deep then make a 90 degree angle and straight out to
the right side. Here is a diagram that shows more.
Now it's time to cut out the slot for your trigger lever. Since
I use a 5/16" square stock steel for my lever, I will use a 5/16" drill bit and
hand held drill to remove the wood in the center of the stock where
the lever goes. When the wood is removed, the slot should look similiar to the
one in the two pictures below. The
slot will go all the way through from the bottom of the stock to where the
roller nut sets.
 
Here
is a diagram to show you more on how the slot is cut inside the
stock
Now I'll make my lever. I start with a piece of 5/16" x
5/16" x 12" long square stock steel. The bends in the lever will depend on how
accurately you removed the wood from the slot where the lever sets shown in the
dotted lines in the diagram above. The first bend, should be made 1" from where
it fits into the notch of the roller nut, this will be the pivet point. Bend a
little bit at a time until the lever fits into the notch into the bottom of the
roller nut and touches the bottom side of the slot in the bottom of the stock.
Once it fits like it is shown in the drawing above, then you measure where the
lever comes out of the bottom of the stock and make your other bends to your
liking. Now you take the lever out of the stock and drill a 5/32" hole at the
pivet point. Then I take the lever and lay it on the outside of the stock, (the
side that is cut out for the roller nut). I lay the lever down on the side of
the stock the same position it would be in if it were set in the roller nut and
the other side at the bottom of the slot of the stock, I mark where the pivot
point is and drill a 5/32" hole straight through the stock, then I take the
lever slide it into the slot, and with a hardened 5/32" pin I slide it through
one side of the stock, through the lever to the outside of the opposite side of
the stock. Then I pull the lever trigger, and slide the roller nut in place. Now
I have to cut a piece of wood, the same wood as my stock, 1/4" thick x 2"
long x 1 5/8" wide. I slide the piece of wood into the slot into the side
of stock where the roller nut is and use 4 small wood screws to secure it in
place, I make sure the roller nut turns smoothly. Then I remove the roller
nut and lever and sand the stock to a smooth finish.
Here is a picture of all the parts to this crossbow.
On the crossbow in this project, The bow is fastened
on the stock with 1/8" twisted nylon string, which is wrapped numerous times to
achieve strength. The foot claw is a 1/2" braided rope, which is looped around
the bow then bound together with 1/8" nylon string. The barrel is cut at 1/4"
wide. Normally it would be 3/16" to accept aluminum arrows, but I made 6/16"
wooden arrows for this project. I used a german style stock and trigger stystem,
but I used an osage bow. If you wish to make a wooden bow for your crossbow,
refer to part 1. After 3 coats of polyeurothane, this is what the finished
project looks like.
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