I was wondering if you guys could possibly help me with my curiosity. I wish I had a chrono to do it my self, but i don't..
I was wondering if anyone has ever done a test to see the differences of speed a 1/2" of brace height can make?
I have heard and read that the higher the brace height, the more speed and more forgiving because of the shorter "power stroke". But i'm wondering exactly what the difference is.
If you would like to help out my curiosity, just shoot your bow through a chronograph and measure the brace height, then change it a 1/2" or so and shoot it again. You can state all the info you want or as little as you want.
Thank you for your help,
Daniel
If you raise brace you loose stored energy and speed but gain shootability.
Lowering brace adds stored energy and speed but makes the bow less forgiving.
Mike
Mike,
thanks for the input. I was really looking for actual numbers.
For example:
BW MAIII
155fps @ 7.5" brace height
147fps @ 8" brace height
143fps @ 8.5" brace height
No one may want to invest the time it takes to do this test, which is fine. I just thought I would ask since I don't have a chrono at my disposal.
Without precise equipment (Hooter Shooter, calibrated chrony, precise set-up, etc.), it's not going to mean much.
Even then, there's going to be a ton of variables...bow type, bow length, string material, strand count, draw length, etc. etc. etc.
Short answer is, in general, 1/2" isn't going to make much difference.
Swap that over to finger shooters, there will be more variance in releases than 1/2" of brace height will make.
This is a test that could take days, and still not wind up with any definitive answers, depending on how specific you want to get.
Chad
I understand that there are a ton of variables.
I am not trying to come up with definitive answers like if i decrease my BH by 1/2" i'll game x-fps. This is mainly just to see some different numbers.
Nothing has to be scientifically correct. Just wanting to know what some numbers would be.
QuoteOriginally posted by wingnut:
If you raise brace you loose stored energy and speed but gain shootability.
Lowering brace adds stored energy and speed but makes the bow less forgiving.
Mike
Thank you, Mike, that is what I was thinking too!
Bisch
I can send u my chrono for awhile if you want to do some testing with ur awesome strings.
I'm sure some of our fine bowyer sponsors have done some testing, and should be able to give you a ball park figure for at least their designs.
Not being smart here but I bet some of our fine bowyer sponsors wish they had the kind of time to test their bows this finely. With all the other demands a self employed craftsman has to handle I suspect they are happy to string their models to a standard brace hight and clock it from there.
In the Traditional Bowyer's Bibles Tim Baker has experience with brace hight and shows, as Wingnut said above, the lower the brace hight the faster arrow cast. I don't believe he has exact figures you are looking for, though.
It has been my experience that bows like to be in a zone. Within the recommended zone some bows like your BW will not vary as much, while others like the Schulz that I recently part with, will make much more of a difference. From 5&3/4" to 6&1/2" on that particular bow made a very noticeable difference. I will not share the numbers because the chrono may have been reading fast and if it was not reading fast, everyone would argue the numbers. But the difference was 12 fps. I never checked my BWs, performance was never anything that I questioned. While I did not care for their handling when not shooting, they seem to have liked every moderate tuning thing that I could do with them with very little noticeable change in performance.
I enjoy playing with bows and my chronograph, and will be happy to run a test for you with one of my long bows. I will say in advance that there will not be much difference, as stated above. Also it will take many many shots to average in order to find such a small difference.
But, seems like a fun project so I'll go ahead on it. It won't be for a few days though since I'm helping to set up a rather large party for Saturday and then I need a good weather window since my chrony does not like cold weather. In fact, neither do I!
If the brace is low enough or high enough to lose vertical stability the limbs may lose quite a bit of energy in excessive flop and vibration. This energy is not imparted to the arrow. This effect may actually cost you more than what is gained by lower brace. However if the limb is vertically stable where it is and vertically stable where you take it then by increasing the brace 1/2 inch you will lose between one and 2 fps. Within reasonable shot variation. Probably closer to 1 fps instead of the two. I give a range of one inch total movement within the recommended brace of my bows and maintaining acceptable performance difference. In otherwords negligible.
Bows will definitely vary.
God bless, Steve
The best thing I did with my chrono was give it away!
QuoteOriginally posted by LBR:
Without precise equipment (Hooter Shooter, calibrated chrony, precise set-up, etc.), it's not going to mean much.
Even then, there's going to be a ton of variables...bow type, bow length, string material, strand count, draw length, etc. etc. etc.
Short answer is, in general, 1/2" isn't going to make much difference.
Swap that over to finger shooters, there will be more variance in releases than 1/2" of brace height will make.
This is a test that could take days, and still not wind up with any definitive answers, depending on how specific you want to get.
Chad
As much as i hate agreeing with Chad on much of anything... He nailed this one perfectly.... To many variables.
The only thing i could add is every limb design is going to have a different sweet spot for the brace height. and that is going to be where the string tension is at the highest preload at brace....You can increase or decrease the brace height past that point and the the preload actually reduces... that's why they call it the sweet spot...
Took an average of a bunch of shots. Generally my release varies +/- 1 fps. 1" drop in BH gained me a whopping 2 fps. But honestly that still must be taken with a grain of salt as basically state of tune went straight down the toilet.
Good post, confirms what I expected without doing the work:) I read about guys tuning an arrow with brace height etc. I always thought tune the bow to it's best and then tune the arrow to it's best is the best;-)
QuoteOriginally posted by pavan:
It has been my experience that bows like to be in a zone. Within the recommended zone some bows like your BW will not vary as much, while others like the Schulz that I recently part with, will make much more of a difference. From 5&3/4" to 6&1/2" on that particular bow made a very noticeable difference. I will not share the numbers because the chrono may have been reading fast and if it was not reading fast, everyone would argue the numbers. But the difference was 12 fps. I never checked my BWs, performance was never anything that I questioned. While I did not care for their handling when not shooting, they seem to have liked every moderate tuning thing that I could do with them with very little noticeable change in performance.
this is what I was looking.
Just some around about figure that you gained or lost by adjusting BH. I do understand that you have to calculate in release, wind, feather size, arrow weight, etc. But I don't care about all that. I am just wanting some random invalid numbers. If youre release sucks, let it suck with both brace heights! :)
QuoteOriginally posted by Keith Zimmerman:
I can send u my chrono for awhile if you want to do some testing with ur awesome strings.
Keith,
did you ever manage to kill anything? :)
QuoteOriginally posted by Kirkll:
QuoteOriginally posted by LBR:
Without precise equipment (Hooter Shooter, calibrated chrony, precise set-up, etc.), it's not going to mean much.
Even then, there's going to be a ton of variables...bow type, bow length, string material, strand count, draw length, etc. etc. etc.
Short answer is, in general, 1/2" isn't going to make much difference.
Swap that over to finger shooters, there will be more variance in releases than 1/2" of brace height will make.
This is a test that could take days, and still not wind up with any definitive answers, depending on how specific you want to get.
Chad
As much as i hate agreeing with Chad on much of anything... He nailed this one perfectly.... To many variables.
The only thing i could add is every limb design is going to have a different sweet spot for the brace height. and that is going to be where the string tension is at the highest preload at brace....You can increase or decrease the brace height past that point and the the preload actually reduces... that's why they call it the sweet spot... [/b]
Kirk,
so this would be my question, as a rough estimate, what do you think the difference between the "sweet spot" and not would be as far as performance?
(rough estimates are fine with me, i'm not going to tell anyone you told me and use it as truth)
It's not rocket science, and you don't need chromo to figure it out. If you raise or lower your brace height by 1/2 inch, you are in effect, decreasing or increasing your draw length about a half inch. A half-inch in draw length translates into 1-1 1/2# of draw weight on a mid weight bow. That, in turn, translates into 1-3 fps. Not enough to worry about.
With Schulz and Hill style longbows while the bow is designed to have quite a low brace, I wonder if the difference between a B50 string to a modern would show differences as well, being that the B50 string would have more carry through than a no stretch string. I would bet that this difference could show up on recurves as well but with less variance.
Modern, low-stretch strings, are faster because they don't stretch as much during the draw or when the arrow is released as does dacron. They don't follow the arrow as far past brace either, but at that point, there's little energy left in the string anyway.
oops - double post
QuoteOriginally posted by Kirkll:
QuoteOriginally posted by LBR:
Without precise equipment (Hooter Shooter, calibrated chrony, precise set-up, etc.), it's not going to mean much.
Even then, there's going to be a ton of variables...bow type, bow length, string material, strand count, draw length, etc. etc. etc.
Short answer is, in general, 1/2" isn't going to make much difference.
Swap that over to finger shooters, there will be more variance in releases than 1/2" of brace height will make.
This is a test that could take days, and still not wind up with any definitive answers, depending on how specific you want to get.
Chad
As much as i hate agreeing with Chad on much of anything... He nailed this one perfectly.... To many variables.
The only thing i could add is every limb design is going to have a different sweet spot for the brace height. and that is going to be where the string tension is at the highest preload at brace....You can increase or decrease the brace height past that point and the the preload actually reduces... that's why they call it the sweet spot... [/b]
If a person has a Hooter Shooter and a calibrated chrono, your only variable would be the difference in brace height, assuming you are shooting the same bow with the same string and arrow to make the comparison. Then just shoot a bunch of shots at each brace height to get a good average. No need to make more out of it than what it is. But I agree, a 1/2" won't make much of a difference.
I got a new to me acs longbow see manlaw new to me acs. I deceided to check what affects changes in brace height has on speed. First let me say I have posted that I believe it does not have a affect on speed so I thought I would back up my words with results. I have a very consistent form, draw and release I usually only very one fps high or low so the results schould be accurate. I have worked with this bow some and I am using a brace height of 7" so I will start lower then this and move up 10 twist at a time untill I go over one inch past starting point and then go back to my 7" were I will keep this bow. I used three different arrow weights let me know what you think and any thoughts about the results.
6 13/16 brace height 387gr 182fps 452gr 177fps 517gr 166fps 7 1/16 brace height
387gr 182fps 452gr 175fps 517gr 165fps
7 5/16 brace height
387gr 182fps 452gr 174fps 517gr 165fps
7 5/8 brace height
387gr 182fps 452gr 174fps 517gr 165fps
7 15/16 brace height
387gr 180fps 452gr 174fps 517gr 163fps
I then went back to my 7" brace height.
387gr 185fps 452gr 178fps 517gr 167fps
I then deceided while I have the crony setup I would check the difference with a hold at full draw and release and the way I shoot a pull threw release. I used one arrow for this it was the 452gr arrow.
Hold and release 174fps
Pull threw release 178fps
So what do you think about the results!
I think I found the correct height for this bow and I will keep it a 7"!
As I thought untill you get a good bit over it does not have any real affect on speed. Widow
Back in 2011 I did this hope it helps. Widow
QuoteIf a person has a Hooter Shooter and a calibrated chrono, your only variable would be the difference in brace height,...
My point is that the readings you get will only be good for that specific set-up, shot with a Hooter Shooter. It can change from bow to bow, even with a different bow of the same make. If you test one bow, you will have an idea of the variance in that exact bow--nothing more.
Throw in the variance of shooting with fingers, it's all out the window. It's not like a sucky release is consistent--if it were, then you wouldn't have a sucky release.
Find the optimal brace height for the bow via tuning and you'll get the best from that bow. A couple of fps rarely if ever makes any difference other than in advertising. In my opinion/experience of course.
Chad
So then, as Kirk suggested, all bows have a sweet spot, possibly where the pounds of force is greater, would be a good brace height. Seems to me we do not need a shooting machine or a chrono, but a scale, an inline string mounted scale perhaps, so we can find that optimum preload point.
I go by feel. I've always been able to find a spot where I get the least noise and vibration (I always tune with a bare string).
It's not complicated or technical, just takes a little time.
QuoteOriginally posted by LBR:
I go by feel. I've always been able to find a spot where I get the least noise and vibration (I always tune with a bare string).
It's not complicated or technical, just takes a little time.
^-------THIS
I follow the bowyer's recommended brace height to a point, then I experiment and find the brace height that gives me the most pleasing draw feel and yields the most forgiving shooting results for ME. These are biomechanical instruments we're messing with here and each shooter must tailor the bow to themselves.
QuoteOriginally posted by Kirkll:
QuoteOriginally posted by LBR:
Without precise equipment (Hooter Shooter, calibrated chrony, precise set-up, etc.), it's not going to mean much.
Even then, there's going to be a ton of variables...bow type, bow length, string material, strand count, draw length, etc. etc. etc.
Short answer is, in general, 1/2" isn't going to make much difference.
Swap that over to finger shooters, there will be more variance in releases than 1/2" of brace height will make.
This is a test that could take days, and still not wind up with any definitive answers, depending on how specific you want to get.
Chad
As much as i hate agreeing with Chad on much of anything... He nailed this one perfectly.... To many variables.
The only thing i could add is every limb design is going to have a different sweet spot for the brace height. and that is going to be where the string tension is at the highest preload at brace....You can increase or decrease the brace height past that point and the the preload actually reduces... that's why they call it the sweet spot... [/b]
Completely agree.
I used to be one of those who thought an increased power stoke by decreasing brace height would increase speed.
A friend of mine showed me the error in that thinking, and showed me how to find that brace height sweet spot. Prior to that I never realized how much I was leaving on the table where performance and stability were concerned. I've never owned a chronograph (or a hooter shooter), but he had one, and the results shocked me to put it mildly.
Actually I go with the recommended brace and nock setting and then find the arrow that works. The variable is for me always the point weight, since I always shoot the same length arrows no matter what. The pattern has been a choice of 145 Grizzlies or 160 Hills or Grizzlies. I notice that the Grizzlies have changed weights, so my world is in total turmoil right now, I cannot sleep normally, my hair is falling out, my wife won't run and I think my pickup is cheating on me.
Pete Ward has probably chronographed as many arrows as anyone and I think he would just laugh at trying what you are suggesting...a lot of what amounts to work to learn something that is of no value...on the other hand I bet if you offer to trade him something nice for the information he is your man
DDave
QuoteOriginally posted by Orion:
It's not rocket science, and you don't need chromo to figure it out. If you raise or lower your brace height by 1/2 inch, you are in effect, decreasing or increasing your draw length about a half inch. A half-inch in draw length translates into 1-1 1/2# of draw weight on a mid weight bow. That, in turn, translates into 1-3 fps. Not enough to worry about.
Orion,
not to "stir the pot", but raising and lowering your brace height would not shorten or lengthen your draw at all. It would shorten and lengthen the "power stroke".
QuoteOriginally posted by widow sax:
I got a new to me acs longbow see manlaw new to me acs. I deceided to check what affects changes in brace height has on speed. First let me say I have posted that I believe it does not have a affect on speed so I thought I would back up my words with results. I have a very consistent form, draw and release I usually only very one fps high or low so the results schould be accurate. I have worked with this bow some and I am using a brace height of 7" so I will start lower then this and move up 10 twist at a time untill I go over one inch past starting point and then go back to my 7" were I will keep this bow. I used three different arrow weights let me know what you think and any thoughts about the results.
6 13/16 brace height 387gr 182fps 452gr 177fps 517gr 166fps 7 1/16 brace height
387gr 182fps 452gr 175fps 517gr 165fps
7 5/16 brace height
387gr 182fps 452gr 174fps 517gr 165fps
7 5/8 brace height
387gr 182fps 452gr 174fps 517gr 165fps
7 15/16 brace height
387gr 180fps 452gr 174fps 517gr 163fps
I then went back to my 7" brace height.
387gr 185fps 452gr 178fps 517gr 167fps
I then deceided while I have the crony setup I would check the difference with a hold at full draw and release and the way I shoot a pull threw release. I used one arrow for this it was the 452gr arrow.
Hold and release 174fps
Pull threw release 178fps
So what do you think about the results!
I think I found the correct height for this bow and I will keep it a 7"!
As I thought untill you get a good bit over it does not have any real affect on speed. Widow
Widow,
thank you for taking the time to do that. that is all I was wanting to know. This post was not for a book so the validity was not necessary, I just wanted to see some numbers.
thanks again.
First of all we have to establish what Good performance or "High performance" really is..
I would say tuning the bow first to find the sweet spot is going to yield the best all "around performance" of that particular bow. It's hard to generalize because each bow is different. But over all "High performance" is a combination of the least amount of noise and vibration which in turn will provide the highest amount of energy transferred to the arrow . this can be measured on the chrono... If you are talking about how much difference in speed, or how much difference in noise or vibration? these numbers and amounts are going to differ a lot between different limb designs.
Here is a good example:
If we look at a long bow limb design with a very low preload at brace, and a lot of limb mass moving forward. The "preload" or the tension on the string at brace is what stops the forward motion of the limbs. At that point the transfer of energy stored in the limbs goes to the arrow shaft.... When you don't have enough preload to stop the limbs clean, a much higher percentage of your stored energy stays in the limbs and goes back into the riser in the form of vibration. This stored energy is lost completely.... and for sake of comparison lets say we end up with 168 fps at 10 gpp measured in the chrono......
With a bow like this i'd bet the brace height could be moved as much as an inch without a measurable difference in speed.
Ok.... Now lets take a recurve bow design, or a hybrid long bow with a much higher preload at brace..... These limbs are designed with a much shorter working portion with much less actual limb travel. The higher preload stops the limbs dead and transfers a much higher percentage of the stored energy in the limbs to the shaft. It also has much less vibration felt in the riser because the limbs are not flopping around. For sake of comparison, lets say this bow shoots 190 fps at 10 gpp through the chrono. The tension on the string at brace or preload is going to change a lot more with a 1" difference in brace height than the long bow with lower preload.... so that 1/2" difference is going to be measurable by as much as 4-5 fps... and the noise level if tuning with a bare string is going to be much more noticeable too.....
Are we splitting hair here? Sure we are...
How much difference does it really make? Well each archer out there has a different idea of getting the most out of there set up. They are all different, and nobody is wrong... But higher performance bows will be more sensitive to brace height adjustments, and they all got there own sweet spots.....
You guys don't need a chrono to find that sweet spot. tune your bow with a bare string using lighter weight shafts for noise, then switch to heavier shafts once you've got the sweet spot in the brace established. If you start getting the brace too high, the bow will still be quiet, but you will notice a drop in trajectory the farther you twist the string.
btw.... there is another way you could measure the optimum brace height on a bow using an in-line cable tensiometer on the string. But they are expensive little buggers... [/QB][/QUOTE]
thanks for that explanation Kirk.
Daniel B. You're right. Because the effect is the same, I use the two terms interchangeably. That's why I qualified the statement with "in effect".
By lowering the brace height, one increases the power stroke. In effect, the arrow is subjected to 1/2-inch more draw even though the archer doesn't pull the bow any further. Likewise, raising the brace height shortens the power stroke. The arrow is subjected to 1/2-inch less draw, even though the archer doesn't draw the bow any less.
Regardless, as I said in my first post. The effect is so small as to be unnoticeable to most folks.
QuoteOriginally posted by Orion:
Daniel B. You're right. Because the effect is the same, I use the two terms interchangeably. That's why I qualified the statement with "in effect".
By lowering the brace height, one increases the power stroke. In effect, the arrow is subjected to 1/2-inch more draw even though the archer doesn't pull the bow any further. Likewise, raising the brace height shortens the power stroke. The arrow is subjected to 1/2-inch less draw, even though the archer doesn't draw the bow any less.
Regardless, as I said in my first post. The effect is so small as to be unnoticeable to most folks.
I can see that. Didn't mean to get technical, jsust needed a little more clarification..
The best Chrono test that I have ever seen devised made a lot of sense to me, but it was not a successful test. A fellow learned the equations to calculate how much stored energy his arrows had at impact. He wanted to know what tuning versus which arrow would give him the best results at his maximum hunting range, because he had this notion that the heavier arrow would retain more energy. He bought a chrono and tested
a variety of set ups, wrote down all of his averages. Then he backed up to his maximum hunting range and practiced all week until he was spot on with his first test set up. He set up his chrono carefully measured everything, waited for the wind to die down and shot. He hit the base of his chrono on the very first shot dead on and killed it.