Design and Construction of a Knock-Up Target

David Day

Sept. 2, 2006

While at the AAFTA nationals this summer in Tacoma, I got to shoot a Bat that when hit fell up instead of down.   How cool is that!!!  Well, I just had to have one but I just spent my last dollar on a beautiful  Woodpecker produced by Craig Taylor.  So after a lot of thinking and drawing, I figured I could build one on my own based on Brad Troyer's design that can be found at http://www.aafta.org/html/education/education_equipment_targets_build.html  

I had previously built a number of these targets and found that they were simple to make.   The only two places where I have deviated from Brad's plan are in the washer to protect the area around the kill zone, and in the tension/spring mechanism.  For the washer, I use a product of the Nutty Company called a 'dock washer' which is essentially a washer with a 3" diameter. They come in various Kill Zone sizes from 3/8" to 1".  I have found that the added area of the washer eliminates virtually all destruction of wood from errant pellets.  I also inlet them into the wood face so it gives me a flat surface to paint.  The second modification I made was replacement of the spring with a mini bungee cord which lets me more precisely adjust tension on the face plate for increased consistency in function of the mechanism.

In thinking through the development of a knock-up target, I figured that I could build Brad's design, eliminate the spring or bungee cord, and replace it with a pulley mechanism to which a counterbalance was attached.  Because gravity would take care of repositioning the Kill Zone arm during resetting by allowing it to simply fall back into place, I also connected the reset cord directly to the target face to allow a more direct force on the counterweight during the resetting process.   Here is the end result:

The target works absolutely great!   The counterbalance was made of a lead core through which an eye bolt was placed.  If you are planning on building one of these targets, they are simple to make, but  I did learn a couple of things along the way that might save you some time and frustration.

First, because the target is upside down gravity seems to have an effect on the tolerances for Brad's KZ trigger mechanism.   You actually have a lot more room for error between the edge of the KZ paddle and the tension pin as a consequence.  What I did on the metal paddle was drill out two channels through which the retaining screws could be placed and basically this made  KZ paddle adjustable up and down.  With the target in position, I just locked the metal part of the paddle into place once I got the tension set just right.

The second thing that went wrong was that gravity worked a little too well on resetting the KZ paddle and this caused the trigger mechanism to engage too close to the target face to allow reliable activation of the target on KZ hits.  This problem was easily eliminated by application of a wood screw to the target face that was adjusted to minimize 'over travel' of the KZ paddle when resetting the target (A).

Another issue I found was that the amount of tension being placed on the sear or trigger mechanism (B) could be effected by the amount of weight on the counterbalance.  Initially I had about 3 times as much weight as necessary on the counterbalance and this tended create so much counter force on the face that the trigger tended to lock in place and require a higher than desired pellet force on a KZ hit to topple the target.   I mention this here only because a little experimentation with the amount of weight needed on the counterbalance to topple the target will save you a lot of time if you are melting and re-melting lead to build the counterbalance.  It isn't necessary to have so much weight on the counterbalance that the target slaps up when hit.  Just enough to insure reliable function of the target without lock-ups is necessary.

As I wanted the target to fall up as flatly as possible, I added two strips of wood parallel to the base of the target and the target face was mounted on these pieces of wood.   What this did was create a channel into which the KZ paddle could fall (or be pulled into) to get it out of the way of the falling target.  Application of of a retaining bolt at each end of the target base topped with a wing nut will allow quick installation on a platform that I have specially built for my target on the WLOPA FT course.

Finally, the first time I used the target in the field, it did not work exactly as planned.  The sear mechanism didn't engage as reliably as I would have liked with different people resetting the target and this allowed the target to occasionally fall with face hits.   Upon close examination, I found two things had occurred.   First, the screws I used to secure the meal KZ plate were too shot and had worked loose causing the KZ plate to shift from the force created on it by the face plate and counterbalance.   Secondly, because the target was not totally level in the field, gravity kept the KZ paddle from swinging totally back into position to reliably engage the sear.   This problem was easily solved by adding a bungee cord that connected the KZ paddle to the face place.  With just a little bit of stretching of the cord during resetting, it causes the paddle to repeatedly 'snap' back into place on the sear without creating additional force that would keep the target from falling with a KZ hit.

I hope this encourages you to build a knock-up target of your own.   I had a lot of fun experimenting with mine and am looking forward to the additional variety it will add to our local FT matches.