prod problems???

Hi guys. Need some advice on a bow I have made. It's an early straight bow with a Alchem prod #3732 @135 #. It shot a foot to the left no matter what bolt I used. I rechecked that the roller cut , fit, ect ,was true, the bolt fits square and near center to the string, and the prod is centered and square to tiller and roller as best as I can tell. HHHMMM!!?? Finally I found at full draw and cocked the prod is VERY uneven from one limb to the other, almost 1 inch more pull on the right limb . I have removed the prod and checked the tiller at 3" brace height and it is even. This is the first steel prod I have used, have had no problems with aluminum, or fiberglass prods. Any suggestions for me, I suspect improper prod tiller, but will not rule out builder error yet.... stevbear

Stevbear: There are several possibilities for consistent shooting to the left.
1. Your prod-socket may be crooked... not perpendicular to the bolt-groove or rest of stock, so your prod actually angles to one side.
2. you may be consistently pulling the bow crooked on spanning (I've seen this done due to old shoulder injury)
3. Your prod may be defective. Usually that shows up when the prod is strung, but not spanned. It won't follow a nice, consistent curve... may have one or more kinks. That should be picked up by quality control at the manufacturers, but occasionally such things slip by.
4. you may actually be rolling the stock to the left when shooting. This is a common fault with long, straight medieval stocks, in which the shooter has trouble getting his eye down low enough for sighting (medieval bows were commonly shot atop the shoulder, rather than shotgun style, and most of the shorter stocks were actually shot free-hand, with the butt of the stock held alongside the cheek)
The first thing you need to do is check to see that your bowstring at rest crosses the stock at a 90 degree angle. If it does, your prod-socket is probably straight. If that measures correctly, take your bow out to the range, make double-sure that you place your hands close alongside both sides of the stock from the beginning of spanning, so that you cannot pull the prod off-line. Okay, now we've got a square mounting and the bow is spanned straight. Now put the butt of the stock atop your shoulder, sight down the bolt and point it at the target. Then make sure the ends of your prod are at the same height, not banking right or left like an airplane.
After making sure that you haven't woggled off-target, raise your head a few inches and shoot, being careful to watch the flight of your bolt. You should be able to tell if it fishtails or whirligigs in flight. Anything other than nice, smooth flight means trouble.
Now go down range and look at your bolt where it's lodged in the target. Is it stuck in straight, or did it go in at some weird angle? Bolts that don't go in straight are indicative of unstable flight. Sometimes it's the bolt's fault: bad fletching, an uneven butt, or head put on crooked, but often whirligging or fish-tailing can indicate a prod that's loose in its mountings, or pulled off-center.
If none of these things solve your problem, there could be a flaw in the prod itself. In that case, you want to talk to Jim Koch of Alchem. If you approach him nicely, he's not hard to deal with.
Geezer.

Geezer has certainly covered all the bases here.

I have the following procedure to offer for getting the prod correctly situated in the tiller.
--set the tiller up vertically in your bench vice...butt end down. It must be perfectly vertical, and very secure.
--set up a stout leather strap with a stirrup...you are going to use this to draw the bow by pressing down with your foot.
--locate the strap so that it is centered on your string.
--draw the bow with your foot, and watch to see if the center of the strap travels down the exact center of the tiller
--reshape the notch in the tiller until this is so

This procedure will make allowances for slightly mis-tillered prods. As long as the string draws perfectly straight, it will also release perfectly straight. Thus the bolt will not be pulled to one side or another.

If your prod is tillered (balanced)perfectly, it will end up perpendicular to the tiller (stock). If it is slightly "off", the final mounting will be slightly off to compensate.

Mac

I would add one other tip. I mark the center of the string with a sharpie marker (mark it at brace directly over the bolt groove). Then when it is cocked the mark should be in between the finger of the roller nut. If not you probally are pulling more on one side than the other. Might make sense being that you are most likely right handed and you noted the right side had more bend.



Todd

Thanks Geezer, Todd, and Mac. I will certainly try what you've told me. It's these types of challanges that makes it fun(and frustrating) work. Getting the prod socket true has always been a hard chore for me.

stevbear

stevbear wrote:Getting the prod socket true has always been a hard chore for me.

stevbear

I use carbon paper, or candle soot and a sharp chisel. It takes time and patience. The job is made more difficult if the prod "works" in the center.

Mac

Ah ha, I never thought of that, I've been going on "feel" and a square, I have also started squaring up my tiller wood from the face Iwant to use as the table, square up the sides to it, and then use drill press to cut roller socket and binding hole. Then square up my prod socket lay out and cut it out, then any shaping of the outside.

Stevbear