Comparison Testing of Plastic Nocks
and HTM Anti Bounce Device Back Nocks.
Sir Jon Fitz-Rauf
Note: The following is not official policy from the office of the SCA Archery Marshal
I have been working on an ABD nock for use on fiberglass shafts. My theory was that a nock with a larger diameter than the standard plastic nocks would be less apt to pass through the bars or visor slot of a SCA legal helm in the slight chance of a possible bounce back. Also by replacing the two sharp edges of hard plastic on a standard plastic nock with a larger flat surface would reduce the chance of possible eye injury.
I decided to use the HTM black rubber small game blunts as a nock. The blunts for the 5/16 shafts are 5/8s of an inch in diameter with a flat striking surface. A slot is cut in the material to fit the bow string and act as the nock slot.
To make a proper fit on a 1/4 inch fiberglass shaft, it was built up with a three inch long strip of 3/4 inch wide electric tape. They can also be used on 11/32s wood shafts by reducing the diameter of the nock end of the shaft to 5/16. They can not be used when the nock end of the shaft has been tapered.
I have shot them from both a non center cut solid fiberglass bow and an almost center cut laminate recurve. The solid fiberglass bow was shot off the top of the grip with no other arrow rest. The recurve was shot both off the shelf and off a simple one piece plastic rest. I used both a one finger over, two fingers under release and a two/three finger under release. In all cases the arrow cleared the side of the bows and flew straight.
I also tested the blunts for 11/32 shafts, they have a 7/8 diameter head. They would only clear the side of the bow on a perfect release, which is difficult under combat conditions.
PASS THROUGH TEST
A comparison test between the small plastic nocks and the HTMs was done to see how much the 5/8 blunt would reduce the number of arrows that would pass between the bars of a legal SCA helm in the case of a bounce back compared to the smaller hard plastic nock.
Testing on the HTM ABD was done using a six inch square test grill of five parallel 1/4 inch bars spaced 1 inch apart, edge to edge measurement. This represents the maximum bar spacing of an SCA legal helm.
Both an arrow with a standard plastic nock(Beman) and an arrow with a HTM nock were dropped from a height of approximately two feet on to the test grill. The arrows were dropped randomly onto the grill. Each arrow was dropped 100 times.
Each drop was recorded as either: A block, in which the arrow shaft was completely stopped by a bar. A hit, in which the nock hit the bar but continued on. A miss, in which the arrow missed the bars completely.
To the naked eye there was little reduction in speed to the plastic nocks when they hit the side of the bar. But, the HTMs seemed to slow down a bit after hitting the side of the bar.
The HTM had: 33 blocks. 13 hits. 54 misses
The plastic nock had: 13 blocks. 7 hits. 80 misses.
The HTMs reduced the number of arrows that passed the bars by a factor of 2.5. This could mean that if using plastic nocks a injury might happen once every ten years, then with HTM nocks it could be reduced to once in twenty five years.
HTM BLUNT/NOCK LIVE TARGET BOUNCE BACK TESTS
In order to compare the injury caused by THM nocks and plastic nocks I built an arrow with removable nocks on both ends. The shaft was 1/4 inch solid fiberglass rod, 29 and 1/2 inches long. An one inch by 5/4 inch UHMW rod was drilled all the way through so as to slide on the shaft. This made it the same weight as one of my standard UHMW combat blunts. The UHMW rod also acted as a draw stop for the bow. This was done so that I could draw it the same length each time.
The draw length was selected to give the test arrow the same distance of travel as one of my standard UHMW blunts. The average bounce back for those blunts is about 15 feet. I actually made the test arrow have a range of about 17 feet.
The test arrow was first given a plastic 1/4 Beman nock at both ends. The bow was my 31 pound at 28 inches Dammon Howart Ventura target bow. A very fast and efficient bow. The distance to the target was six feet from the tip of the arrow at its limited full draw to my chest.
The arrow was shot three times at my bare chest with the plastic nock on the front of the arrow. The results from this were:
|Shot #1||Location-right side of sternum. Damage-Cut skin and drew blood, blood dripped from the double cuts from the edges of the nock.|
|Shot #2||Location-right side of chest over ribs. Damage- Cut skin and drew blood, but did not bleed.|
|Shot #3||Location-right side of stomach. Damage- Cut skin shallow, no blood.|
The plastic nock was then removed and a HTM blunt/nock was put on in its place and the process repeated as with the plastic nock. The results from this were:
|Shot #1||Location- left side of sternum. Damage- red mark about the size of a quarter.|
|Shot #2||Location- left side of chest, over ribs. Damage-red mark about a the size of quarter.|
|Shot #3||Location- left side of stomach. Damage-lighter red mark slightly smaller than a quarter.|
The area of each impact was circled with a pen in order to compare the size of any bruising over a period of time. I rechecked the impact marks after one hour. The red marks from the HTM blunt/nocks had faded out, without the pen circles around them it would have been very difficult to locate them. The cuts from the plastic nocks had stopped bleeding and were now beginning to show bruising. The bruising from the plastic nocks took about five days to fade out.
The damage done to human skin by the HTM blunt/nocks is negligible compared to that of the plastic nocks. I did not compare impact upon the human eye, but it could be inferred that the possible damage there would also be equally reduced. If anyone has access to sheep eyes, which can be found in some Near Eastern markets, they may run a comparison test on them.
Given both the reduction in the chance of a HTM nock passing the bars of a helm and the greatly reduced damage that could be caused by it, I would recommend their use to anyone that would want to reduce the chance of one of their arrows causing injury by a bounce back.
The HTMs can be purchased at most archery shops and when combined with a break proof fiberglass shaft the possibility for injury is greatly reduced from wooden shafts with plastic nocks. And there is only the least amount of reduction in range or accuracy.
First cut off the thin 1/4 long section of the blunt, so that it is shorter. Then using two or three hacksaw blades bound together, depending on the diameter of your bow string, you cut a slot in the center of the face of the blunt. Make sure that the slot is centered and perpendicular. You can cut the slot a 1/4 to 5/16 inch deep.
Then using a small flat file, finish the width of the slot so that your string will slide easily into the slot, but will not fall out. If you have a small round file you can enlarge the bottom of the slot making a form of snap nock.
If you taper the mouth of the slot in to a "V" shape it will be easier to guide the string into the slot.
One method of mass producing them would be to use a router and router table with a jig to guide the blunts. A 1/8 inch veining bit can cut the slots. A wider angled bit can be used to taper the mouth of the slot.
Make sure the nock is a snug fit on the shaft then remove and glue it in place. For 1/4 inch shafts you can build up the diameter with electrical tape or with heat shrink electric tubing. You need to make sure the nock is aligned correctly with the fletching. Then glue in place.
For wooden 11/32 shafts you can use a file to reduce the diameter for a good fit.
You can not use the HTM nocks on shafts which have the nock end tapered.
For questions related to this article please contact the author: Sir Jon Fitz-Rauf
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