Primitive Archer

Main Discussion Area => Bows => Topic started by: sleek on August 28, 2019, 08:00:24 pm

Title: Bow limb tip movement.
Post by: sleek on August 28, 2019, 08:00:24 pm

Per inch of draw, has anyone figured how much a tip moves? Is it dependent on bow length? Seems it would be. Say a 54 inch bow pulled to 26 inches... That's what I am trying to figure out right now. I'd just measure myself, but all my gear is packed away for yet another road trip...

Title: Re: Bow limb tip movement.
Post by: Badger on August 28, 2019, 08:16:51 pm

  Look at one of the full draw pics we have taken on a tillering board.

Title: Re: Bow limb tip movement.
Post by: DC on August 28, 2019, 09:37:00 pm

I've found that it is roughly 1/3". 3" of DL =1" of tip movement. It varies some depending on the brace height and I assume other things affect it. If you figure 28" DL and 7" brace height that leaves 21" of power stroke. 7 and 21, that's a third, coincidence, probably. I always thought it would be 2 to 1 because it seemed like stretching a diamond to me. But you start out minus the brace height. I've only measured it on longer bows that you like so it may change with a short bow. Del mentioned a couple of times that he's measured it and got the same results I did. 3-1.

Title: Re: Bow limb tip movement.
Post by: Badger on August 28, 2019, 09:57:42 pm

At 90 degrees it is 1:1  at brace it is much less maybe 5:1   string angles and bow length affect it.

Title: Re: Bow limb tip movement.
Post by: SLIMBOB on August 28, 2019, 10:23:53 pm

I have always been fascinated by this and understand little about it. The tip moves in 2 planes, both horizontal and vertical. I assume you are measuring how far the tip actually travels, point A to point B. I wonder if there is an optimal vertical/horizontal ratio during the whole thing. A ratio that produces the best results. Bow length surely plays a roll.

A whip ended bow will move more vertical. A bow with stiff tips and loose near the grip would move more horizontal. Or so I figure. Neither is optimal. So what is the optimal sequence. I hope that clarifies my question. Sorry Sleek if I stepped on you here.

Title: Re: Bow limb tip movement.
Post by: Badger on August 28, 2019, 10:41:43 pm

  If you put a bow in a vice and hook a string and scale to one limb and start bending it you will see it doesn't change all that much from start to finish.

Title: Re: Bow limb tip movement.
Post by: DC on August 28, 2019, 11:04:14 pm

Quote from: Badger on August 28, 2019, 09:57:42 pm

At 90 degrees it is 1:1  at brace it is much less maybe 5:1   string angles and bow length affect it.

If you average out 1:1 and 5:1 you get 2.5:1. that's pretty close to 3:1 ;D ;D ;D ;D

Title: Re: Bow limb tip movement.
Post by: Badger on August 28, 2019, 11:39:39 pm

Yea 3 to 1 sounds about right

Title: Re: Bow limb tip movement.
Post by: DC on August 28, 2019, 11:53:59 pm

Yeah but I think your's is more right and it kinda explains what's happening with the leverage and the gafarken and follaw ;)