Big John

That sound you hear is me clapping!!!!!!!!!!!!!

mlaubner

Ok, everyone...I had the absolute pleasure of meeting Len in his shop on Sat. afternoon. I do not have enough time to type the accolades, but suffice it to say that Macrotech as a shop and Len as the leader of the pack, are without a doubt, the finest pro-shop I have ever seen in my life!
Every tune-up tool and gizmo know to modern man.
The level of professionalism is first class.
If Len and the people at Macrotech can' t fix or tune it, it can' t be done!
If you need to drive an hour+ to get there...go.
I would gladly make the trip. In a word...Unbelieveable!

But back to the original question...." What I learned Saturday about bow effeciency"
The short version goes like this: For each pound of bow draw weight, you should get 1 pound of kenetic energy. This would be your end result, in a perfect world, if all your components are perfectly matched, etc.

Using my bow as an example: 386gr arrow @252=54# K.E. off of a 63# bow= 85% efficiency.

So to increase my bow efficiency it appears as though I would have to tweek my arrow weight:speed ratio so as to affect my KE number to get it higher. Right?

Rangeball

Ok, now I' m confused... How am I able to get over 70' #s of KE out of a 70# draw bow?

walks with a gimp

This area is where BowTech shines bright My Pat Dually and Pro 40 both produce close to 10 foot pounds more of K.E. than the peak weight at 29 inches draw length. Short draw archers can take advantage of better engineering for increased performance and accuracy. You can simply find out for your self what your bow is doing with a chronograph and a scale to weigh your arrows. If you get 60 ft. lbs. of K.E. with a 60 pound peak compound bow, you' re doing ok but you can get more

mlaubner

From what I understood, the 100% bow in an enigma, only exists in utopia and has never been held by human hands.
The object was to try and get as close to this as possible...I think.
Again, my impression, was that it was an impossibility in reality but a goal to try and attain.
It almost sounds religious.

JeffB

I had a HUGE post discussing the topics that Len and PW had mentioned unofrtunately if you don' t put in a subject line , when you hit reply, it goes to a blank screen asking if you want to go back and if you do, all of your post is gone! [:@][:' (][>:][X(]

I just would like to mention quickly (especially to Len) that when I was home in Northern VA I went to a local Mass Merchant named Galyans. Theya re an upscale outdoor sports merchant. In thier archery section were about a dozen brand new PARKER bows! UL' s, the mid price model w/ the camo grip, etc. Surprised the hell out of me. Might wanna give the crew down in Mint Springs a call Len[8D].

Suffice to say, With the Free Market Economy our country is based on, the small business owner is going to HAVE to learn how to deal with and counter the mass merchant (or fade away). I' m sure back in the early days of the 20th century many five and dime store owners had a friggin fit when Woolworths hit the scene.a speople do now w/ Wal-Mart.

Right or wrong, it' s the way of life here in tehse United States. It' s very tough for the little guy, but I sure as hell wouldn' t like the alternative. I' d rather not stand 8 hours in a line freezing my butt off for some Government Issued Toilet Paper, Bread and a pack of Thunderheads [:-]

CapstoneME

I' m not 100% up to speed on this topic, I must admit. BUT, I do know this: the area under the force/draw curve is the stored energy available when you reach full draw. It is measured in FOOT-POUNDS. (Not just pounds.) That means that the FOOT component contributes along with the POUNDS component. (i.e., you can get an energy total higher than the pounds of pull because the energy is a product of pounds over distance.)

How " efficient" your total system is depends not just on the design of the bow, but how well your arrow can absorb the energy that the bow releases during the shot.

I think I remember learning somewhere that the most efficient compound design is a wheel bow. It seems like the wheels provided the best mechanical advantage, storing more energy for less work. This does not mean they' re faster. The area under a " hard cam" curve is greater, and the cams store more energy, BUT you' ve got to pull up a MUCH steeper force/draw curve. This means that they' re less comfortable to draw, etc.

Arthur P

Rangeball, because your bow STORES more than 70 pounds of energy as you draw it. You don' t just put 70 pounds of your muscle energy into drawing a 70 pound bow, especially one of the new cam designs that hits peak weight early and holds it until nearly full draw.

The longer the draw length, the more energy it stores. The lower the letoff, the more energy it stores. Someone with a short draw length and high letoff will likely never get 1 ft lb of energy per every pound of draw weight. Someone with a long draw and low letoff would likely get more than 1 ft lb for every pound of draw weight.

Mark, I' m sitting here looking at Norb Mullaney' s bow test report for the Browning Eclipse. At 30" draw, 60 pounds, 75% letoff, it stores 70.55 ft lbs. At 65% letoff, it stores 71.78 ft lbs. At 65% letoff, it shoots a 400 grain arrow at 244 fps for some 53 ft lbs of energy. It shoots a 500 gn arrow 222 fps for just under 55 ft lbs. It shoots a 600 gn arrow 207 fps for just over 57 ft lbs.

This bow, at 30" draw, NEVER hits 1 ft lb for every pound of draw weight. As you can see, increasing the arrow weight does make the bow more efficient, but at the cost of arrow speed. IF your bow showed the same KE gain as the Browning, 2 ft lbs for every 100 grains of arrow weight, then you might get 63 ft lbs of KE into your arrow by jumping weight up to 836 grains. Doubt you' d want to do that though.

I believe strongly in heavy arrows and momentum, and think KE is secondary in importance and highly overrated when it comes to penetration, but there is a limit to how much speed I' m willing to give up.

mlaubner

Thanks Arthur P, Your example illustrates what an enigma the " efficiency" number can really be.
I guess you have to find a happy middle ground with as high a % as is practical given your particular shooting needs.

It has been quite a learning experience along the way.

Now, how do I put the lid back on this can of worms?

Arthur P

You' ll probably have to encase it in lead and bury it under 30' of concrete.