Comment on handshock

[Badger]

Yesterday I gifted a bow to a friend of mine. A long time archer bowyer in his late 70's. The bow was 38#@26" very fast little r/d hickory backed osage. The bow was a bit too heavy so I decided to remove wood from the inner 1/3 of limb near the handle. I dropped it to about 32#. I couldn't believe how much handshock this bow picked up when I did this. Tiller was still good just a much more circular tiller. This is the first time I have seen such a dramatic change when retillering something. Seemed like the bow suddenly became overbuilt. Steve

[Pat B]

Steve, could it be the increased tip weight relative to the overall weight once you reduced wood from the center of the bow?      Pat

[DBernier]

Sounds just like Pat may surmise. Tips transferring the vibrations down to the handle and not enough mass there to absorb it.
   Pat still working on the arrow shafts. Steve showed up yesterday.

Dick

[Badger]

   Not really sure Pat, the tips were so small the last 6" or so I couldn't imagine making them any smaller. I think the mid limb area was just a bit too wide for the lower weight, when I thin about it I reduced the weight by almost 25%, on a heavier bow it wouldn't mean to much to drop 6 or 7# off the weight. Loooking back now I wished ZI would have just narrowed the mid and inner limb instead of scraping down the thickness. Steve

[Pat B]

The limbs are recovering together? I'm real curious now.  What causes hand shock? uneven limb timing, excess tip weight, too much handle bend without enough limb bend?   I'll be thinking on this.    Pat

[George Tsoukalas]

Badger, so what caused the hand shock? Too much bending near the handle? Hand shock is pretty relative to the person shooting. Jawge

[Badger]

Pat, I have been working with some modern bow builders on limb vibration. It seems the tips actually arrive home before the mid limb in most cases. Toward the end of the power stroke the arrow is trying to slow the tips down just enough so that the mid limb can land just before them, When the tips are too heavy or if the mid limb is not rigid enough or both then the tips momentum will resist slowing down just enough to land home before mid limb giving that vibration. What we have found is that just slightly more aggressive tapers in thickness allowing for a more elyptical bend along with keeping mass down in outer limbs seems to counter this pretty good, often with wood we just have to do the best we can with what we have. Steve

[waterlogged]

quickly read over this one, will come back to it later, but my guess is that a change that dramatic means you hit something of a fundimental frequency, or just really unlucky harmonics. Either of those could be fixed with slight changes in mass placement. Interesting puzzle.

[son of massey]

  i wonder about the fact that is a r/d bow instead of a straight stave bow. making the tiller much more round in the handle may add to the effect of the deflex, which would be the equiv. of having a bow with set near the handle...but this bow doesnt have that, so instead of a floppy set induced bit of wood that doesnt store the energy for shock this well tillered stout mass of wood has that energy to jar the hand?   just a hypothetical, but that is an interesting case. SOM

[GraemeK]

Hi Steve
I have found that D/R bows are prone to this and having the mid limb thinner and wider worsens the problem but is sometimes impossible to avoid with all wood bows. I have also found that if the limbs are tillered to be straight at brace height rather than elliptical the problem tends to be less but I guess that just means they are stiffer mid limb.

Graeme