Calling all Chronograph owners..

DanielB89 · January 14, 2015, 09:55:00 AM

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

wingnut · January 14, 2015, 11:10:00 AM

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

DanielB89 · January 14, 2015, 11:25:00 AM

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.

LBR · January 14, 2015, 11:43:00 AM

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

DanielB89 · January 14, 2015, 12:05:00 PM

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.

January 14, 2015, 12:26:00 PM

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

Keith Zimmerman · January 14, 2015, 02:01:00 PM

I can send u my chrono for awhile if you want to do some testing with ur awesome strings.

Pheonixarcher · January 14, 2015, 02:35:00 PM

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.

ChristopherO · January 14, 2015, 02:44:00 PM

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.

January 14, 2015, 02:51:00 PM

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.

monterey · January 14, 2015, 03:09:00 PM

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!

Sixby · January 14, 2015, 03:17:00 PM

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

Gil Verwey · January 14, 2015, 03:24:00 PM

The best thing I did with my chrono was give it away!

**DONOTDELETE** · January 14, 2015, 08:23:00 PM

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...

Bender · January 14, 2015, 11:08:00 PM

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.

old_goat2 · January 14, 2015, 11:57:00 PM

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;-)

DanielB89 · January 16, 2015, 09:19:00 AM

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!

DanielB89 · January 16, 2015, 09:20:00 AM

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?

DanielB89 · January 16, 2015, 09:28:00 AM

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)

Orion · January 16, 2015, 03:28:00 PM

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.