# Nock Travel Testing Fixture



## practice-more (Nov 10, 2005)

I am very interested in exactly what "fixture" you have designed to test this and what the results of your tests are.

Please don't keep us waiting too long.

Mitch


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## TailChaser (Aug 13, 2005)

That's awesome. Thank you for testing. I'd love to see the results.


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## LEADWORKS (Apr 6, 2006)

me too, I want to know!!!!!!


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## acal (Jan 13, 2003)

I would like to know also.

Thank you !


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## oldbuck (Apr 14, 2006)

*Nock Travel Info coming!!*

Hello,
I have started to test bows and compile data. I will show it to all in approx two weeks. So far the results have been very revealing. I want to attach picture files and a spread sheet for the data. Does anyone know how its done on AT ?? Need some help here folks...
thanks
oldbuck:embara:


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## glrjola4 (Feb 2, 2006)

*Draw Board*

A lot of archers discuss about the better Draw board or how should be an accurate draw board to test nock travel.

Pls see http://www.archerytalk.com/vb/showthread.php?t=378156&page=2

Can you attach or send me pics of your Drawboard ( i will attach them for you )

[email protected]

Thanks a lot and I wish you will have a lot of good results to teach us.

Jorge


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## RP-archer (Jan 30, 2007)

I see that there are few other archers out there that are interested in plotting/evaluating nock travel so I thought I would post a few pictures of the jig that I built. The idea came from a bow comparison done by Hunters Friend between a Champion Scorpion and a Bowtech Liberty. In the comparison one of the categories was nock travel. To test this, they served a Sharpie marker to the bowstring and drew the bow back with long rope so that when they let it down to plot the path the long string would not influence the natural course of the string. 

The jig that I have uses a boat winch to keep the bow back at full draw and the winch cord is attached to an aluminum block that has a hole sized for a sharpie marker. When you view the pictures you’ll notice that there is an end mill cap with a rubber band on each side that goes over the sharpie to keep the marker engaged on the paper as the bow is being let down. The bow is held by two upright 3/8” bolts through blocks of wood that are clamped to the table. This allows the bow to be aligned and allows maximum adjustment for different bows. The 2x4 with the winch attached to it is clamped to the table and is secured behind the winch to the wall. 

The red line in the photo is perpendicular to the string and the black line represents the nock travel. This bow is a customized PSE that was retrofitted with a Pearson PHD Post-feed Thruster Single Cam. This cam was advertised as having perfect horizontal delivery (PHD). I like the characteristics of the cam in that it was fairly fast and quite, but it was finicky to tune. As you can see, maybe the name of the cam should have been RHD – relatively horizontal delivery. I’m not implying anything negative against this cam or company, as there are quite a few cams that do not have perfect nock travel. Also, there is generally a compromise between single cams that are adjustable with modules. One of these compromises being optimum nock travel. 

I’ve plotted several bows and have found that single cams tend to have a downward slope and about mid-way come up a bit. Dual-cams that are out of sync will start out with a slightly “squiggly” line and then straighten out. One interesting note, when I plotted my wife’s Bowtech Equalizer, with the binary cams, it produced a nice straight line even though the cams were not perfectly synchronized. Perhaps these actually do self-regulate as they suggest. 

I hope you find this interesting. This type of jig is a starting point and can be refined, but this seemed to produce the results that it was designed to do.


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## RP-archer (Jan 30, 2007)

Add'l pictures


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## pyroarch57 (Jul 13, 2006)

That`s some real weird nock movement. Are you sure the clamps aren`t moving slightly?


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## pyroarch57 (Jul 13, 2006)

pyroarch57 said:


> That`s some real weird nock movement. Are you sure the clamps aren`t moving slightly?


That would explain the `squiggly` line.


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## NMP (Aug 6, 2003)

That is exactly what we have found to be able to happen when the riser is bound (by two bolts in this case) and the pulling devise is in a fixed location. If you look at the pic the winch is contantly trying to pull the nocking point toward the camera during the draw and effecting the travel. It does this noticably until the bow reaches peak draw weight then slowly tries to return to the right position.


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## NMP (Aug 6, 2003)

NMP said:


> That is exactly what we have found to be able to happen when the riser is bound (by two bolts in this case) and the pulling devise is in a fixed location. If you look at the pic the winch is contantly trying to pull the nocking point toward the camera during the draw and effecting the travel. It does this noticably until the bow reaches peak draw weight then slowly tries to return to the right position.


The effects of this will be minimized by centering the winch with the nock point and berger hole.


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## pyroarch57 (Jul 13, 2006)

NMP said:


> That is exactly what we have found to be able to happen when the riser is bound (by two bolts in this case) and the pulling devise is in a fixed location. If you look at the pic the winch is contantly trying to pull the nocking point toward the camera during the draw and effecting the travel. It does this noticably until the bow reaches peak draw weight then slowly tries to return to the right position.


If that were the case, then the winch cable would pull it offline throughout its travel.
Obviously it is desirable that the winch cable is in a straight line. But, IT IS IMPOSSIBLE FOR THE WINCH CABLE TO PULL THE STRING OFFLINE, ANY EXCESS STRING COMING FROM EITHER SIDE WILL JUST MOVE THE NOCK POINT IN THE OPPOSITE DIRECTION. I thoroughly tested this out on my jig. I removed the central eyebolt that my cable (rope) runs through and wound it in from the far side of the drum, this made no difference at all to my nock travel point, i did the same thing from the opposite side of the drum, again, no change. I have done other things to determine the accuracy of the board and they have confirmed this.

To give you an idea of what`s happening- hold your index and second finger in a`V` Tie a short length of string with some slack in, around the top of those two fingers (this will simulate a drawn bowstring) tie another piece centrally on that string, making sure it cant slip, Now pull on the string a few inches back from where it`s tied (now simulating the drawboard) move one of your fingers slightly towards you and watch how the `nocking point` moves.

This duplicates exactly what the drawboard is doing. Also you don`t need to have the winch cable much more than the bows drawlength.

So, to sum everything up, if anyone is thinking of making a drawboard this way you can be assured that it works PERFECTLY well and it will be EXTREMELY accurate in predicting any adverse nock travel.


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## pyroarch57 (Jul 13, 2006)

*Board*


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## francis (Jan 18, 2003)

ttt


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## hayman (Sep 9, 2004)

Maybe I missed something here. What is the point of plotting the nock travel? Can it be adjusted?

Bill


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## NMP (Aug 6, 2003)

pyroarch57 said:


> If that were the case, then the winch cable would pull it offline throughout its travel.
> Obviously it is desirable that the winch cable is in a straight line. But, IT IS IMPOSSIBLE FOR THE WINCH CABLE TO PULL THE STRING OFFLINE, ANY EXCESS STRING COMING FROM EITHER SIDE WILL JUST MOVE THE NOCK POINT IN THE OPPOSITE DIRECTION. I thoroughly tested this out on my jig. I removed the central eyebolt that my cable (rope) runs through and wound it in from the far side of the drum, this made no difference at all to my nock travel point, i did the same thing from the opposite side of the drum, again, no change. I have done other things to determine the accuracy of the board and they have confirmed this.
> 
> To give you an idea of what`s happening- hold your index and second finger in a`V` Tie a short length of string with some slack in, around the top of those two fingers (this will simulate a drawn bowstring) tie another piece centrally on that string, making sure it cant slip, Now pull on the string a few inches back from where it`s tied (now simulating the drawboard) move one of your fingers slightly towards you and watch how the `nocking point` moves.
> ...


Do me a favor and dont mount your riser down to the draw board. Just let it sit against the two pins you have to mount it with. Then offset your winch to the nocking point by about 3" like this fellow has done and check your nock travel. You will come up with the same reading as he did. The reason that yours does not do this is because your winch is centered with the berger hole and the riser is locked down. You are not trying to force the nock point in any direction except straight back. This is what I was concerned about the last time we had this conversation. I didnt say that these things dont or wont work.


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## pyroarch57 (Jul 13, 2006)

NMP said:


> Do me a favor and dont mount your riser down to the draw board. Just let it sit against the two pins you have to mount it with. Then offset your winch to the nocking point by about 3" like this fellow has done and check your nock travel. You will come up with the same reading as he did. The reason that yours does not do this is because your winch is centered with the berger hole and the riser is locked down. You are not trying to force the nock point in any direction except straight back. This is what I was concerned about the last time we had this conversation. I didnt say that these things dont or wont work.


 To measure nock travel accurately, the bow has to be held stationary. So whether the bow is bolted down or just resting against its posts has no consequence, providing it does not move.
I believe RP-archer`s photo was taken from slightly left of his table. I think his winch is in line with his nock point, but even if it isn`t it will not make a shadow of any difference to the nock travel. (as explained clearly in my last post).


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## Dave Nowlin (May 21, 2003)

I won't contribute to the arguement, but will say that I talked to the gentleman who does the testing for Mathews a few years back after talking to Josh at Spott-Hog. The man told me that by using very high speed photography they had discovered something very interesting. A bow will draw one line when drawn, a different line when carefully let down and a third and still different line when shot. I'm actually only interested in the line drawn when the bow is shot. That's the only one which gives useful information. I hope you can find a way to plot that line.
Dave Nowlin


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## pyroarch57 (Jul 13, 2006)

Dave Nowlin said:


> I won't contribute to the arguement, but will say that I talked to the gentleman who does the testing for Mathews a few years back after talking to Josh at Spott-Hog. The man told me that by using very high speed photography they had discovered something very interesting. A bow will draw one line when drawn, a different line when carefully let down and a third and still different line when shot. I'm actually only interested in the line drawn when the bow is shot. That's the only one which gives useful information. I hope you can find a way to plot that line.
> Dave Nowlin


It`s not an argument Dave, it`s a factual discussion.


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## RP-archer (Jan 30, 2007)

Pyroarch - I like that draw board you have - compact. My results have been similar to yours in that the winch rope does not seem to influence the nock path even if the winch is not positioned precisely perpendicular to the string and/or berger hole although it is probably a good practice to do so. When I have the bow drawn back there is still approximately 5 feet of cord between the winch and the bowstring but this is probably an excessive precaution to avoid influencing the nock movement. I may shorten this up because it sounds like you are getting good results with a shorter distance from the bowstring to the winch when the bow is at full draw. 
I have graphed this bow (PSE Baby-G with a Pearson Thruster cam) several times with different modules making sure the clamps were tight and things were lined up and the plots are very similar. The majority of the change is in the first inch or so when the bow is let down – the cam just doesn’t have the best travel although it was better than the lightning cam that was originally on the bow. This bow has always been very critical when paper testing. You could tune it to shoot near bullet holes but only at specific distances from the paper. I’m sure that the tune was just matching the arrow paradox at the specific distance. In contrast, I have a Darton Tempest Extreme (CPS cam) that will shoot bullet holes 4 feet from paper and at all distances back to about 38 feet (max distance in the basement). It just seems that bows that truly have straight, fairly level nock travel (not merely advertised straight nock travel) tune up easier - sometimes a lot easier – then those that don’t. How would you know for sure unless you plot it. That is the value in testing – at least to me.


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## pyroarch57 (Jul 13, 2006)

It just seems that bows that truly have straight, fairly level nock travel (not merely advertised straight nock travel) tune up easier - sometimes a lot easier – then those that don’t. How would you know for sure unless you plot it. That is the value in testing – at least to me.[/QUOTE]

You have it in a nutshell there RP. When i first read an article on this subject by James Park it got me wondering about the nock travel on my `03 U`tec. I thought i had it set up perfectly - but on the drawboard it showed a straight line pull for 2/3rds distance, then a gradual climb up to 3/8" nock high at full draw. 
I tied a length of cotton pulled taut around the axles and measured the tiller, then compared this against tiller at rest, there was a discrepancy indicating that my top limb was slightly stiffer than the bottom limb. 
I advanced the top cam a little (to let more string out) and managed to get the nock travel down to its best setting which was 1/6" high. Tuning is a breeze now, and the bow has never shot better.


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## Jerry/NJ (Jan 17, 2003)

pyroarch57 said:


> It just seems that bows that truly have straight, fairly level nock travel (not merely advertised straight nock travel) tune up easier - sometimes a lot easier – then those that don’t. How would you know for sure unless you plot it. That is the value in testing – at least to me.


You have it in a nutshell there RP. When i first read an article on this subject by James Park it got me wondering about the nock travel on my `03 U`tec. I thought i had it set up perfectly - but on the drawboard it showed a straight line pull for 2/3rds distance, then a gradual climb up to 3/8" nock high at full draw. 
I tied a length of cotton pulled taut around the axles and measured the tiller, then compared this against tiller at rest, there was a discrepancy indicating that my top limb was slightly stiffer than the bottom limb. 
I advanced the top cam a little (to let more string out) and managed to get the nock travel down to its best setting which was 1/6" high. Tuning is a breeze now, and the bow has never shot better.[/QUOTE]

Nice job and interesting as well! On your board, do you just watch the nock area in relation to the red line you have? As compared to RP's board with the sharpie?


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## pyroarch57 (Jul 13, 2006)

Jerry/NJ said:


> You have it in a nutshell there RP. When i first read an article on this subject by James Park it got me wondering about the nock travel on my `03 U`tec. I thought i had it set up perfectly - but on the drawboard it showed a straight line pull for 2/3rds distance, then a gradual climb up to 3/8" nock high at full draw.
> I tied a length of cotton pulled taut around the axles and measured the tiller, then compared this against tiller at rest, there was a discrepancy indicating that my top limb was slightly stiffer than the bottom limb.
> I advanced the top cam a little (to let more string out) and managed to get the nock travel down to its best setting which was 1/6" high. Tuning is a breeze now, and the bow has never shot better.


Nice job and interesting as well! On your board, do you just watch the nock area in relation to the red line you have? As compared to RP's board with the sharpie?[/QUOTE]

Yes Jerry i do. That`s the reason i prefer a winch over a pull cord etc - it`s nice and quick.


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## Jerry/NJ (Jan 17, 2003)

pyroarch57 said:


> Nice job and interesting as well! On your board, do you just watch the nock area in relation to the red line you have? As compared to RP's board with the sharpie?


 Yes Jerry i do. That`s the reason i prefer a winch over a pull cord etc - it`s nice and quick.[/QUOTE]

My set up isnt as purty as you guys' but I'll have to give it a try...thanx :thumbs_up


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## RobVos (May 23, 2002)

Dave Nowlin said:


> I won't contribute to the arguement, but will say that I talked to the gentleman who does the testing for Mathews a few years back after talking to Josh at Spott-Hog. The man told me that by using very high speed photography they had discovered something very interesting. A bow will draw one line when drawn, a different line when carefully let down and a third and still different line when shot. I'm actually only interested in the line drawn when the bow is shot. That's the only one which gives useful information. I hope you can find a way to plot that line.
> Dave Nowlin


Dave is correct on this. You cannot get an accurate representation of the real dynamaic nock travel during the shot with these set-ups. First, if you are clamping the bow in or resting it anywhere other than the grip, you are not allowing the riser to flex as it normally does during the draw and shot sequence. Secondly, you are applying a force to the bowstring the entire time and even though you think it does not matter, the bow reaction would be different withour that force that you are constantly applying. And you cannot be certain that the wood draw boards that are being used are not experiencing some deformation -- they sure are.

While I enjoy these threads and find it interesting, the only real way to test is with high speed video.


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## oldbuck (Apr 14, 2006)

*Nocking Point Travel*



RobVos said:


> Dave is correct on this. You cannot get an accurate representation of the real dynamaic nock travel during the shot with these set-ups. First, if you are clamping the bow in or resting it anywhere other than the grip, you are not allowing the riser to flex as it normally does during the draw and shot sequence. Secondly, you are applying a force to the bowstring the entire time and even though you think it does not matter, the bow reaction would be different withour that force that you are constantly applying. And you cannot be certain that the wood draw boards that are being used are not experiencing some deformation -- they sure are.
> 
> While I enjoy these threads and find it interesting, the only real way to test is with high speed video.


 
I have been in contact with the head of R&D for Mathews and had many conversations about nock travel. He said that the nock travel very closely follows a plot from a draw board. It needs to be attached and drawn from the nocking point on the string. The plots are a very accurate representation of the dynamic travel. He said this was verified via high speed photography that he personally did. His nock travel data and mine are virtually the same. The tests I did and the data I published on this forum are representative of the bows tested. As far as frame flex is concerned, I have measured flex on many risers, both top and bottom. The delta flex is an insignificant amount, also most of today’s bows have parallel limbs and the flew has VERY little to no impact on the nock travel. There may be some difference bow to bow, as there are manufacturing tolerances to take into consideration. All you folks who take the time to make a draw board, feel confident about your results. High speed video is only one way to get an answer about nocking point travel.
oldbuck


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## Marcus (Jun 19, 2002)

> High speed video is only one way to get an answer about nocking point travel.


Actually it isn't and there is a very cheap way of getting the information that you require with better quality than high speed video. I am just not allowed to tell you how.


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## oneluckypops (Feb 24, 2007)

Marcus said:


> Actually it isn't and there is a very cheap way of getting the information that you require with better quality than high speed video. I am just not allowed to tell you how.


then why say anything at all? Seems to me if anyone has factual information they would be more then willing to share it or is that just the american way?


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## Marcus (Jun 19, 2002)

Actually the american way is to not give something away for free. 
However as said, high speed video ant everything.


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## pyroarch57 (Jul 13, 2006)

Marcus said:


> Actually the american way is to not give something away for free.
> However as said, high speed video ant everything.


Well, the drawboard is more than adequate for me. There`s too much `hair splitting` going on in archery!


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## Marcus (Jun 19, 2002)

Agreed! :darkbeer:


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## hayman (Sep 9, 2004)

hayman said:


> Maybe I missed something here. What is the point of plotting the nock travel? Can it be adjusted?
> 
> Bill


*
Can it???*

If so HOW?


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## oldbuck (Apr 14, 2006)

*Nock Travel Adjust*

:teeth:


hayman said:


> *
> Can it???*
> 
> If so HOW?


The travel can be optimized with two cam bows. By that I mean you can get bow cams in synch, and adjust out errors made by out of synch, the straighter the travel the better it is. After that the _cam profiles_ dictate the the overall travel, level and/or straight. As typical for all the two cams I tested, the "travel" rises from the bracing height to full draw. Some bows only .35", one I tested was .97" high. Some two cams had a large "s" curve at the end of the draw, indicating cams out of synch. Note that there is a difference between "straight" and "Level" nock travel. With this info you can hopefully flight tune the bow/arrow in an optimum way. No absolutes here, but more knowledge is better than less when it come to your shooting. Build a draw board, you will educate yourself about these issues, its interesting and fun. What bow do you shoot?
I hope this helps you.
oldbuck


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