Estimating draw strength without scale

[Dane]

I hope this is a simple question, but they often aren't

An upcoming problem I am going to have is estimating draw weight when you pass the maximum weight your scale can show.

I don't recall, but may be wrong, that there is a formula one can use for this situation, if you at least know a draw weight at a certain draw length, but then run out of little numbers for weight, ie max out your scale.

Hope that makes sense,

thanks,

Dane

[George Tsoukalas]

3 # per inch will get you in the general area. Jawge

[Marc St Louis]

What does your scale read up to?

[Keenan]

As Jawge said about 3 pounds per inch of draw. You can fine tune that number by running your own chart and see what it's gaining per inch up to that point.  I have found that the shorter 60" and less tend to build a bit faster at about 3.5-4 pounds an inch.

 Ps.  Sometimes the poundage drops drastically (about a millisecond) before the tip hits me in the head. 

[Dane]

Marc, I have the Pelouze 110# scale. I think I got it through 3 Rivers. This is for the gastrophetes machine. I'm targeting 200# for that project. Since I want it to draw that weight for a 12" bolt / arrow and I plan to brace the bow at the standard 6", where would I be when I max out the 110# scale? The bow will be made from hickory, and sinewed. One recommendation is a 36" bow, about 2" wide at the center.

Keenan, George, thanks, 3# per inch - that is the figure I couldn't remember. Thanks.

Dane

[CraigMBeckett]

Dane,

if you used pulleys you could double the reading so your scale could be used for 220 lb.

The bow string would need to be attached through a pulley such that on one are of the string through the pulley is the scale and the other is used to apply the force,  preferably pulling through another pulley for the change of direction. The draw stroke of the strings through the pulleys will be twice the drawn length of the bow string. Each string in the pulley will take half the thrust.


Craig.

[zenmonkeyman]

Yes!  Like Craig said!  I took the liberty of making a crap- drawing, which photobucket downgraded to make  ultra-crap-.     Anyways, without further ado, I present:



(Not to scale) 

[Dane]

Zen, I am going to print out that awesome picture and put it in my workshop. You made it totally clear, too. Thanks so much. And thanks for the laugh.

Dane

[zenmonkeyman]

Just happy to contribute!   

[Marc St Louis]

Marc, I have the Pelouze 110# scale. I think I got it through 3 Rivers. This is for the gastrophetes machine. I'm targeting 200# for that project. Since I want it to draw that weight for a 12" bolt / arrow and I plan to brace the bow at the standard 6", where would I be when I max out the 110# scale? The bow will be made from hickory, and sinewed. One recommendation is a 36" bow, about 2" wide at the center.

Keenan, George, thanks, 3# per inch - that is the figure I couldn't remember. Thanks.

Dane

If you are pinning a 110# scale then the increase/inch is more than 3#/inch.  Heavy draw weight bows can have an increase of more than 5#/inch towards the end of the draw

[CraigMBeckett]

Zen

what a great drawing, thanks

Craig.

[Justin Snyder]

Marc, I have the Pelouze 110# scale. I think I got it through 3 Rivers. This is for the gastrophetes machine. I'm targeting 200# for that project. Since I want it to draw that weight for a 12" bolt / arrow and I plan to brace the bow at the standard 6", where would I be when I max out the 110# scale? The bow will be made from hickory, and sinewed. One recommendation is a 36" bow, about 2" wide at the center.

Keenan, George, thanks, 3# per inch - that is the figure I couldn't remember. Thanks.

Dane

If you are pinning a 110# scale then the increase/inch is more than 3#/inch.  Heavy draw weight bows can have an increase of more than 5#/inch towards the end of the draw

What Marc said, Ill bet it is closer to 7 pounds per inch when you get close to 200lb.

[Dane]

Thanks for the help, Marc and Justin.

Dane