Ballistic Chronometer - Revision 1.5

A colleague brought it to my attention that there were a couple errors on the schematic I posted for the Poor Man's Ballistic Chronometer. The revised version is shown here.

I have also updated the schematic on the original post and wish to offer my sincere apologies to anyone who might have downloaded this circuit and attempted to build it.

The original post is located here: http://inkarlslab.blogspot.com/2012/01/poor-mans-ballistic-chronometer-part-1.html

More on Making a PVC Pipe Archery Bow

Regular readers of this blog will recall the piece I wrote about my experimental PVC archery bow. I wanted to see if one could actually produce a longbow type archery bow easily and cheaply using PVC. Between family, school, and other demands I have not gotten out to shoot it yet. See my previous post here:
http://inkarlslab.blogspot.com/2011/06/homemade-pvc-pipe-archery-bow.html

While doing some research a couple weeks ago I stumbled upon this interesting you-tube video. It details how to make a PVC bow that is considerably more elaborate than the one I made and wrote about. It's owner claims 60 pounds draw weight - quite respectable, in my opinion.

http://themanscave.com/hunting-outdoors/pvc-bow/

There are plenty of sites online that deal with PVC as a cheap and readily available material for making archery bows. Here is a quick distillation of what I have learned:

USE EYE PROTECTION when shooting ANY archery bow!! Any bow made of any material could potentially break. This could cause eye injury, depending on where the pieces fly. I've also heard of strings breaking and swatting people in the face, too.

1) While PVC will work, it does NOT have the speed or the "snap" of wood or fiberglass. In other words, when the string is released, a PVC bow of a given design and draw weight will take slightly longer to return to the relaxed position. Thus it will not produce as much arrow velocity as other materials.

2) PVC will develop a "memory", or "take a set", if it is left strung all the time. Thus, one should always unstring the bow when not in use.

3) On ANY "traditional" style bow, you want a brace height of 6" - 7". The brace height is the measurement between the string and the handle - in this case as measured at the middle of the bow. I should adjust mine by shortening the string slightly; the brace height is about 4.5".

4) The "composite" design of "Themancave's" bow offers the advantage of better speed due to the fiberglass rod core. Doing as he said by using a 1/2" pipe slipped inside a 3/4" pipe might also help protect against breakage - though I'd use soap or lanolin instead of petroleum based oil as the assembly lubricant.

5) If you paint PVC as "Themanscave" did, beware that the solvents in the paint will eat into the PVC and weaken it somewhat. Krylon and Rust-Oleum both make a spray primer for PVC. This primer is supposed to help the paint bind to the PVC. I'm currently using that on my own PVC projects to hopefully avoid the paint flaking I've experienced in the past.

6) As I mentioned in my previous post on this topic, PVC gets quite brittle at temperatures below the mid 40's Fahrenheit. So don't try to shoot it in cold weather. PVC also degrades due to UV exposure - so don't leave your PVC bow exposed to sunlight when not in use. Painting your bow will protect it from UV exposure, but as I mentioned above the paint itself will weaken the material slightly.

While PVC does have certain disadvantages as pointed out above, it can be a viable way to obtain a bow quite cheaply and easily, and also might prove to be a useful emergency technology in a survival situation.

If any readers have made and used a PVC bow, I'd love to hear from you. In a future post I plan to cover simple "home and hardware store" materials to use for making bowstrings.

A Homemade PVC Pipe Archery Bow

For thousands of years, the bow and arrow have been used for both sport and survival hunting. Even today it is still used throughout the world. In America, it is primarily a sporting weapon, though occasionally it is still used for more serious purposes. For example, during the Vietnam conflict, American Marines were said to have used bows and arrows for relatively close situations where a quiet, discrete weapon was needed.

Ever since I was a boy, archery has fascinated me. I had never owned a bow nor did I have the opportunity to get instruction from anyone who could properly teach me. As an adult I fortunately was able to take archery at a local college. I did quite well in it and bought my first bow shortly before the end of the course. Since then, life intervened and I haven't shot a bow in years. While I still have my factory-made bow, I wanted to try something a bit different.

My Hardware Store Specials:
One goal of mine was to, as much as possible, stick with materials I could readily buy at any local hardware or home improvement store. When doing a project I try to avoid any hard-to-find or exotic stuff whenever I can.

I am currently doing two archery bow-building projects. Both of these are classified as "long bows", as opposed to a recurve or compound bow.

One is a "board bow" - so named as it is carved from a solid 6' piece of red oak 1" x 2" board. I have the rough shape cut out and am in the process of whittling it to its final shape. This is a painstaking process involving a draw-knife and/or a carpenter's plane. More on this project in a future post. I got the board for under $10 USD from the local Lowes Home Improvement Center.

In the picture above is another experiment I am doing - the PVC pipe bow. While handling some PVC pipe a while back, it occurred to me that given its springiness it should make a crude but effective bow. Some searches of Google and you-tube revealed numerous examples of folks who have made PVC bows. Many of them were of low draw weight and made by kids, but a few are of decent (40# or more) draw weight and made by adults. And so I made the one in the picture above. It consists of a 72" piece of 1.25" schedule 40 PVC pipe. The string is my own crude attempt at a "Flemish bowstring", made from 6 pieces of mason's line. I bought my mason's line from the local Home Depot for about $5 USD.

I haven't fired this bow yet, but I do have some arrows that are suitable for the approximate draw weight involved. In a future post I will give test results, draw weight measurements, ...
Meanwhile I have built a wooden stand for measuring the draw weight accurately and for "tillering" the board bow. "Tillering" is the process of shaping the limbs of the bow and adjusting their tension so that the bow is properly balanced.

A Word (or Two) of Warning:
If you decide to try this, BEWARE that PVC gets extremely brittle in cold temperatures! DO NOT try to use such a weapon at temperatures below 45 degrees F - it could shatter and injure you!!

Secondly, when messing around with unproven materials such as these, use some good, stout eye protection. If the string or the bow fails, you do not want the shrapnel going into your eye.

By the way: PVC pipe is great stuff; I've found all sorts of novel uses for it. PVC performs reasonably well up through VHF frequencies for winding loading coils for amateur radio antennas.
Granted, this has NOTHING to do with archery, but it is another valid re-purpose of a common commodity.