# how much force does it take?



## Relentless (Jul 20, 2007)

How much force does it take to press a 70# compound bow?? How much force must a press produce...


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## rookiebowholder (Jan 31, 2010)

probobly 70 ounds


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## Hammer0419 (Nov 21, 2005)

rookiebowholder said:


> probobly 70 ounds


I have no clue but I would bet more than 70lbs. Most could lift, pull 70lbs but couldn't squeeze a bow to compress it. You have to figure when you draw a bow it has two wheels/cams which lighten the load and make it easier to draw. Maybe I am way off base but I would think it is a lot more???


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## tenzero1 (Aug 3, 2009)

Hammer0419 said:


> I have no clue but I would bet more than 70lbs. Most could lift, pull 70lbs but couldn't squeeze a bow to compress it. You have to figure when you draw a bow it has two wheels/cams which lighten the load and make it easier to draw. Maybe I am way off base but I would think it is a lot more???


I agree with you and it may be noted that many bows with a #70 max can exceed that to some extent and having that as your press weight may not be enough


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## unloaded (Jan 11, 2010)

I'm thinking the opposite, that it would be less than 70lbs. because you don't need the string slack enough to reach full draw, just enough to get some slack in it. I'm not sure either though. If I ever finish my press I'll try to rig a scale on it and see.

peace.
unloaded


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## racer102 (Jul 16, 2006)

*force*

I've been told it's about 20 lbs at string slack. When your bow is at full draw it's now at 70 lbs think about it you only have to compress the tips enough to slack the string and if you pull your bow now lets say 4 or 5" do you need that much muscle as when your at full draw and shooting


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## revwilder (Apr 11, 2005)

Gentlemen, I don't have the perfect answer, but go back to the old recurve. The more you flex it the stiffer it becomes, because it wants to return to its original shape. The limbs on your compound are no different. 

I agree with hammer. The compound bow is a pulley system. The system allows you to draw and hold much more than you could do without them.

I could be way off base, but a pulley system you multiply the number of strings to the weight you are pulling to get how much you are actually lifting. If that is true in the case of a 70lb bow X2 is 140lbs and we all know that a bow has three X3 210lbs. 

I would suggest that it takes somewhere between 140 and 210 lbs to press your bow.


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## Usingmyrights (Aug 19, 2008)

I think that the example of lifting or pulling 70lbs compared to pressing the limbs together is a bad one. The movement needed to press the limbs together really isn't used and most people aren't going to be very strong in that area. However the more common, natural movements of lifting, pulling, etc are naturally going to be stronger and that explains why someone who could easy move 70lbs other wise couldn't compress a bow as easily if at all. The pulleys do make a difference, though I'm not sure how much since one or both aren't round and you're fighting agaisnt getting ti over the hump.


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## XForce Girl (Feb 14, 2008)

*70*

I takes 70lbs...

if it draws 70 lbs, then you need 70lbs to press it.

Stop over analyzing, pressing a bow is no different than drawing a bow, except the bow is laying horizonal instead of vertical.


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## Widgeon (Jul 17, 2009)

XForce Girl said:


> I takes 70lbs...
> 
> if it draws 70 lbs, then you need 70lbs to press it.
> 
> Stop over analyzing, pressing a bow is no different than drawing a bow, except the bow is laying horizonal instead of vertical.


Unfortunately, incorrect. Pressing a bow directly pushes the limbs towards each other without using the cams.

If you think it takes 70 lbs. of force to press a 70 lb. bow, try this little exercise then get back to me: 

Put a dowel in the bottom cam so that the cam can't rotate. Set the bow on a soft surface, such as carpet, and try pushing the top limb towards the bottom limb, even putting your full weight on it. What happens?

Mechanical advantage (pullies, lever arms, etc.) is a wonderful thing!


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## XForce Girl (Feb 14, 2008)

*ok*



Widgeon said:


> Unfortunately, incorrect. Pressing a bow directly pushes the limbs towards each other without using the cams.
> 
> If you think it takes 70 lbs. of force to press a 70 lb. bow, try this little exercise then get back to me:
> 
> ...


No I'm not going to do that, I'll just take your word for it.
Guess I shouldn't of posted here, made myself look silly.


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## Squawsach (Apr 26, 2008)

I can't tell you how much force it would take to press a 70# bow to the point of being able to change cables and the such but it's going to take quite a bit. The compound bow flexes the limbs at draw by using some highly engineered cams which give the archer a great mechanical advantage. I can pull a 70# recurve bow. If put a string on the naked axles of a 70# compound bow and attempted to draw it, I would get nowhere. My answer to the question is more than 70 pounds.


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## Widgeon (Jul 17, 2009)

XForce Girl said:


> No I'm not going to do that, I'll just take your word for it.
> Guess I shouldn't of posted here, made myself look silly.


I can't even count how many times I've learned something by making myself look a lot worse than silly!


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## jrip (May 19, 2008)

Relentless said:


> How much force does it take to press a 70# compound bow?? How much force must a press produce...


For most 70# bow its going to be well over 350#, and some are near 500#.


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## GBG (Mar 4, 2007)

I have an old 80# Jennings with the micro adjustable cable yokes. Setting the bow verticle on a soft surface it takes 150-200# just to relieve enough tension on the cables so I can turn the adjustment screws by finger. To compress it completely and remove the strings and cables, I use two 400# racheting tie down straps. Even then I need leather gloves to keep the ratchet handles from cutting my palms. BTW, I-Always-Wear-Eye-Protection when pressing and working on a bow.


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## Rhody Hunter (Jul 14, 2008)

it is definatly not 70 lbs . it depends on the bow because all the coumponds are pulley systems but the cams add a twist to figuring the force that it takes to draw it. thus we have different let offs and diferent lbs in the cycle. the way the limbs position also matters. is it parrrallel ? the angle it is on and the angle it is being pressed at affect force needed to press it . think about moving an object in a straight line and the same object being pushed from an angle. it will be diferent.
my best guess would be around 3 times the bow wieght but for an exact answer you would need to know the componants and variables of the bow to calculate


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## Relentless (Jul 20, 2007)

I am guessing somewhere around 500 lbs. as well...i was curious because I am building a press and have an engineering friend who wanted to run a computer model, ect.


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## NJBuckBuster (Jul 9, 2007)

I can tell everyone this, 

I have a 400# Linear Actuator mounted on one of my DIY Linear Presses and it will not press a bow over 60 lbs. 

I have tried about 10 different bows at 70 lbs and out of all of them I was only able to press one bow just enough to install a peep {with a string separator that is.}

I thought a 400# was going to be enough but I guess not. I am going to get a bigger one and I will report back.

NJBB


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## jrip (May 19, 2008)

You have to remember that the cams on your bow are gears also. They dramatically reduce the amount of force it take to draw a compound bow. Some of the speed bow are around 7-1 to 8-1 gear ratio, for a 70# bow that equates to 490#-560# of limb force to produce a 70# draw weight. Much more than the 70# on the limb sticker.


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