Chronographs

aquatoo

Member
Anyone got any experience of using chronographs in bow tuning? If you have which is the best and how useful is it?
 
D

Deleted member 7654

Guest
I have a chrono, it's a bit tricky to get consistent results with a longbow due to arrow flex at short range and my inability to put one through the beam at long range!
Also lighting is a prob, my dear lady wife doesn't like me shooting in the garden where I could use daylight, so I have it set up in the garage with 2 100w incandescent bulbs mouted in diffusers, hanging above it, (Fourescents are no good due to the flicker), a better lighting fixture would prob help...but it's a pain to make one. The current one is on sting and I hoist it up to the ceiling when not in use.
Recently I used it to look at speed difference between 70gn and 100gn points, (only about 6fps) but I went by feel anyway and used the 100gn with by latest longbow.
With a centreshot bow it will be much easier to get good results.
I don't think it will help with 'tuning' much, but I know zip about compounds/recurves and centre shot stuff. It will tell you speed but not how quick the arrow settles etc, I just watch 'em fly and go by feel with my self bows, but then they aren't doing mach 8.
Del
 

aquatoo

Member
A method for using a chronograph for recurve bow tuning is mentioned here:
https://sites.google.com/site/archerybibliography/documents-1/tuningwithspeed.pdf?attredirects=0

Proposed explanation of the basis of the method is presented here:
Speed Variation Tuning
The button tuning method in the paper you highlighted is interesting insofar as it ignores bracing height variables. I had thought that in order to obtain the highest speed with a standard fletched arrow it was necessary for the nodes of the arrow to be aligned when the arrow left the string and, to turn the argument on its head, that this "ideal" arrangement resulted in the highest arrow speed thereby confirming the tune of the bow.

It seems to me that this would be the first use of the chrono and that tuning the button pressure would be secondary.

However.........
 

joetapley

New member
Adjustment of bracing height (vibration/noise) is generally considered to come under the heading of bow set up rather than tuning.
Static arrow alignment with flight direction has no effect on measured speed with a gate chronometer. Obviously the arrow travel path angle with the plane of the chrono gates (the cosine error) will have an effect on measured speed.

As far as 'usefulness' goes the measured effect of tuning on speed is very small (<2fps). Commercial chronos are not particularly accurate anyway. For most archers their natural 'technique' derived speed variation is going to be much larger than the tuning speed variation. So using speed for tuning not very useful even for top level archers.

You can clearly fiddle about with arrow speed (increase draw weight, lighter arrow, brace height adjustment etc) but the faster arrow resulting may be a very poor (and un-tunable) bow set up.

I think what your really adjusting with BH is the string exit path to the alignment of the nock.
 

aquatoo

Member
I think what your really adjusting with BH is the string exit path to the alignment of the nock.
Hi Joetapley

I agree that BH directly affects nock alignment and that was the point that I was trying to make. If the nock is not in line with the string at exit point I had assumed that the arrow speed would be reduced to some measurable degree.

If that's not the case and the button adjustments makes such a small difference then perhaps using a chronograph might be a bit of a waste of time
 

joetapley

New member
Hi Joetapley

I agree that BH directly affects nock alignment and that was the point that I was trying to make. If the nock is not in line with the string at exit point I had assumed that the arrow speed would be reduced to some measurable degree.

If that's not the case and the button adjustments makes such a small difference then perhaps using a chronograph might be a bit of a waste of time
I agree that there is a speed penalty via nock - arrow separation but is it 5fps or 0.05fps? Unless you can quantify it to some reasonable degree then you don't know whether there's any mileage in it. With the Frangilli method, I considered it many years ago and discounted it as the (calculated) speed difference was too small to be of practical use. The bright (Frangilli) idea was to interpolate the tuning setting from speed values that were (just about) measurable.
 

aquatoo

Member
I agree that there is a speed penalty via nock - arrow separation but is it 5fps or 0.05fps? Unless you can quantify it to some reasonable degree then you don't know whether there's any mileage in it. With the Frangilli method, I considered it many years ago and discounted it as the (calculated) speed difference was too small to be of practical use. The bright (Frangilli) idea was to interpolate the tuning setting from speed values that were (just about) measurable.
Seems that the only way to find out would be to get a chronograph and shoot a lot of arrows at differing brace heights.
 

joetapley

New member
Seems that the only way to find out would be to get a chronograph and shoot a lot of arrows at differing brace heights.
The problem is that changing brace height changes measured arrow speed in a number of different ways - can't see the tree for the wood.
That's why in in the Frangilli speed method you compare (the difference between) a bare shaft with a fletched shaft. Speed difference depends only on the tuning (variable) and slight arrow mass difference (constant). All other speed affecting variables are going to affect the bare and fletched shafts equally assuming arrows shot close together in time. You could in theory just shoot fletched arrows and measure the speed change with tuning but then you are not allowing for other speed affecting variables messing up the measurements.
 

aquatoo

Member
The problem is that changing brace height changes measured arrow speed in a number of different ways - can't see the tree for the wood.
That's why in in the Frangilli speed method you compare (the difference between) a bare shaft with a fletched shaft. Speed difference depends only on the tuning (variable) and slight arrow mass difference (constant). All other speed affecting variables are going to affect the bare and fletched shafts equally assuming arrows shot close together in time. You could in theory just shoot fletched arrows and measure the speed change with tuning but then you are not allowing for other speed affecting variables messing up the measurements.
Many thanks for all the information. I'll probably get a chrono and go from there
 

buzz lite beer

Well-known member
Anyone got any experience of using chronographs in bow tuning? If you have which is the best and how useful is it?
Using a chronograph to tune a bow will most probably get you a nice fast efficient bow set up, but it's very likely not going to be the best set up in terms of being the most accurate one for getting good consistent groups.
 

BorderBows

New member
Are you talking compound or recurve...
Id think Bow tune would best suit compounds, due to some variables being fixed due to design and tweaking of allen keys ect.

But I would have thought Chrono's would be better used to tune the archer to repeatability, Consistancy of release, and maybe even tab face tests, than bow tune, since there are dozens of "other" variables in recurve bow tune (cant coment on compounds) that can effect speed on a recurve. Such as Arrow tune, draw length, ect.
I can see the one result if speed is your goal, Limbs wound in, Low brace hieght, and a light weight point and a loss of FOC.
If you were going for consistancy, id look at the human/bow interface with a chrono...
Other than that use a chrono to try and find out what gives a faster setup to find the cause and effect of each part of bow tune. but not to tune a bow.

Just our 2p's worth...

Worth playing with though...
 

aquatoo

Member
Are you talking compound or recurve...
Id think Bow tune would best suit compounds, due to some variables being fixed due to design and tweaking of allen keys ect.

But I would have thought Chrono's would be better used to tune the archer to repeatability, Consistancy of release, and maybe even tab face tests, than bow tune, since there are dozens of "other" variables in recurve bow tune (cant coment on compounds) that can effect speed on a recurve. Such as Arrow tune, draw length, ect.
I can see the one result if speed is your goal, Limbs wound in, Low brace hieght, and a light weight point and a loss of FOC.
If you were going for consistancy, id look at the human/bow interface with a chrono...
Other than that use a chrono to try and find out what gives a faster setup to find the cause and effect of each part of bow tune. but not to tune a bow.

Just our 2p's worth...

Worth playing with though...
I realise that tuning a bow is subject to more variables than just arrow speed but it thought would give a starting point for the only variable that is not clearly defined - other than by trying to decide where the bow is quietest - bracing height. I find that I'm never sure where it is quietest and sort of go with what feels smoothest.

In order to determine quietest you pretty much need someone with nothing much to do for an hour or two so that they can listen away from the bow for you. Difficult to find!
 

joetapley

New member
I realise that tuning a bow is subject to more variables than just arrow speed but it thought would give a starting point for the only variable that is not clearly defined - other than by trying to decide where the bow is quietest - bracing height. I find that I'm never sure where it is quietest and sort of go with what feels smoothest.
I think with BH you take the split the difference approach. For me there is around a half inch range of BH where noise/vibration is low and no detectable difference is noticeable. So if you can detect noise change (increase) at 8.5" and 9" limits then around the mid point, 8.75" is about where you want to be. Don't think BH setting is that critical as it sort of comes out in the wash when you do the bow set up (initial bare shaft) check and the draw weight, if necessary, is adjusted.
 

aquatoo

Member
I think with BH you take the split the difference approach. For me there is around a half inch range of BH where noise/vibration is low and no detectable difference is noticeable. So if you can detect noise change (increase) at 8.5" and 9" limits then around the mid point, 8.75" is about where you want to be. Don't think BH setting is that critical as it sort of comes out in the wash when you do the bow set up (initial bare shaft) check and the draw weight, if necessary, is adjusted.
Simon Needham thinks differently in his book suggesting that BH is very important. I tend to agree with you in that you can pretty much get a bow into tune providing it isn't making a huge crash each time you release it. It would be nice, though, to know the optimum BH for a given setup - which, I think, is where I came in.
 
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