# Tiller



## wanemann (Oct 7, 2010)

well.... there ya have it.


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## Dacer (Jun 10, 2013)

That's perfectly clear! You explained tiller so expertly that you didn't even have to explain it.


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## theminoritydude (Feb 11, 2013)

Seen it? Go ahead, scrutinise it.

Alright, the graffiti you see above was traced out of a 70" (25" riser) bow with a positive tiller of 9mm. For those who are not familiar, a positive tiller means that the perpendicular distance from the string to the pivot point of the limb on the riser is larger on the upper limb than the lower limb. This setting is one of the most common, if not, the recommended setting for a conventionally tuned olympic recurve bow. 

Now, it's been said at least once that the reason we have a positive tiller, is to compensate for the bow hand being offset below the bow centre. It's also a popular thinking among archers that due to the positive tiller, the lower limb is the stronger limb (or the limb undergoing more force at brace compared to the upper limb). Correct me if I'm wrong, I'm looking at a recent post, and that's what it says to me there. Although it may be argued that a positive tiller is not what I have stated above, I'm going to take it as just that, and we can go about with any clarifications should that become necessary.

Alright, let's get one thing clear; there is only ONE string on this bow. That implies the string exerts the same pulling force on the upper and lower notches of both limbs.......

Right now some of you may be having a mind*ck, it's very normal. It usually happens when one has a deeply held belief that is in conflict with his or her rational mind. We shall proceed to rectify the situation. Indeed there exists a difference between the upper and lower limb, despite the fact that both limb tips experience the same force (well, close enough). The difference occurs at the limb roots (I call it that, some of you call it something else, just to be sure, that's the part being squashed by the limb bolt). So most of you understand that when you turn your limb bolts into the riser limb pocket, you are increasing the stress of the limbs. That is absolutely correct.

What some people I have spoke to seems to suggest that IF YOU TURN IN THE BOLT OF THE LOWER LIMB, YOU ARE STRENGTHENING THE LOWER LIMB RELATIVE TO THE UPPER LIMB. That is incorrect. When one increases the flex of a limb, the opposite limb experiences a more than corresponding increase in its flex. Refer to the diagram above, the strings are placed in parallel for visual comparison of their respective limbs. Notice that the upper limb is being flexed more than the lower limb (I know, their positions are not suggestive of their labels, apologies for the bad arrangement), which suggests that all things being equal, the only meaningful differences between the two, are the forces exerted on the respective limb bolts, and the amount of "dead zone" left on the limbs.

"Dead zone" is a name I give to the portion of the limb that is in contact with the string. It is a region that is at any given moment in time that does not do any work.

If one examines the two dead zones, one should see that the upper limb has less of it at brace than the lower limb. With any luck, during the draw, the upper limb is going to have less dead zone as well, all the way to the full draw. Limb utilisation for a recurve is unlike that for a longbow or straight bow, or even that of an asiatic horn bow, in that it is an "infinite gear" system, giving it unparalleled efficiency, beating even the compound bows. Which explains why aggressively recurved limbs like Borders and Uukha seem to be able to shoot faster arrows with so much less effort. But I digress, again.

My take on a positive tiller is this: It does not matter how the bow reacts when you draw. That is just meaningless. Unless someone is going to score on a smooth draw, I don't see why a bow should be tuned based on how it draws. It should be tuned based on how it shoots, not how it feels like when it shoots, but how it actually gets the arrow to where you want it to go. And how and where you want your arrow to go, is in a straight line (or as straight as you could). Imagine if you drew your bow in a straight line between your nocking point and your bow hand, do you think your arrow is going to trace a straight path as well? Anyone who is good in geometry will know the answer.

So quit saying that tiller should be adjusted based on how your bow draws. Your arrows don't give a sh*t.


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## w8lon (Jun 2, 2012)

My old tired bow shoulder begs to differ on your assessment of tiller and how the bow draws. To me tiller matters more in how the pin settles on the target, why fight it when a tweak of tiller will settle the pin on center of target.


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## theminoritydude (Feb 11, 2013)

I am happy for you.


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## Dacer (Jun 10, 2013)

I genuinely, sincerely appreciate you taking your time to expound on your findings, and opinion on the matter tiller. 

I think there is room for adjusting both on feel and what's happening with the arrow as they are not mutually exclusive when shooting an arrow. I certainly see what you are getting at with the changes of One limb directly effecting the other and I think that rational would be right on except for a couple different relationships. 

If you keep the bow riser at a constant reference angle (vertical) - the string angle about a point in the vertical plane of the riser at brace height does change ever so slightly, based on tiller. 

While this angle changes while the placement of the draw fingers and the bow hand does not causing one limb to be ahead of the other in terms of its individual force curve - also the fact that one is not pulling at the string center. 


Let's use the example of a 0 tiller & The angle of the string at full draw with respect to the nock point and the plunger. The angle made with the top limb is less than that made with the lower limb. This suggests to me that while the limbs work together the top limb is ahead in its individual draw cruve than the bottom limb's from the fact of being off center.

A more extreme example would be to draw the bow back while putting your bow hand behind the top limb pocket and the draw hand appropriately place on the string. Draw the bow. The top limb clearly has more work done on it than the bottom limb as seen by the difference in displacement. More work done on the limb, more stored energy in that respective limb. 

Also I do think it has a direct effect on The feel of the bow hand becuase if my reasoning it correct it will effectively change where the pressure point of the grip is When the system settles into its equalibium at full draw. As far as accuracy I always thought of tiller in the same light as Cam timings for a compound bow. Adjusting so that both limbs have finished thier power strokes at effectively the same time. 


Simply my take on the mechanics of it, but I'm a lot better at calcuating molar flow rates than spring systems. However, That was fun. 

Apologies for typos - using my iPhone.


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## julle (Mar 1, 2009)

theminoritydude said:


> So quit saying that tiller should be adjusted based on how your bow draws. Your arrows don't give a sh*t.


So do arrows care about tiller at all? I've always been under the impression that tiller is something only mediocre archers are concerned about. I just set it somewhere at 0-4mm positive, set nock points so arrows flies horizontal and be done with it.


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## theminoritydude (Feb 11, 2013)

julle said:


> So do arrows care about tiller at all? I've always been under the impression that tiller is something only mediocre archers are concerned about. I just set it somewhere at 0-4mm positive, set nock points so arrows flies horizontal and be done with it.


So is it 0, or 1, or 4?

My guess is, no one in this forum knows. And I'm not even talking about a particular value, I'm saying no one here even knows how to go about finding it, other than how they feel about it, which is highly subjective.


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## Dacer (Jun 10, 2013)

theminoritydude said:


> So is it 0, or 1, or 4?
> 
> My guess is, no one in this forum knows. And I'm not even talking about a particular value, I'm saying no one here even knows how to go about finding it, other than how they feel about it, which is highly subjective.



Perpendicular distance from the base of the limb as it come out of the limb pocket to the string. a -b = tiller a being the top limb and b being the bottom limb. 

Atleast that's the conventinal way of doing it as documenting in various tuning and set up guides published by easton/hoyt and such. However I suspect if you aren't really worried about a true value and just a the relationship between the two limbs then as long as it's close to the limb pocket the exact place where it is measured isn't important as long as the individual remained consistant with his methods.


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## Mika Savola (Sep 2, 2008)

I 've almost always used negative tiller (1/8-3/16") on my bows. PB FITA 1288.


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## theminoritydude (Feb 11, 2013)

Dacer said:


> If you keep the bow riser at a constant reference angle (vertical) - the string angle about a point in the vertical plane of the riser at brace height does change ever so slightly, based on tiller.


No it does not. This implies that the string curves. It doesn't. Its gradient with respect to the riser is constant.



Dacer said:


> While this angle changes while the placement of the draw fingers and the bow hand does not causing one limb to be ahead of the other in terms of its individual force curve - also the fact that one is not pulling at the string center.


Firstly, comparing draw hand placement (a displacement parameter) with string angle (angular parameter) is comparing fruits with bugs. Second, one is indeed not pulling at the string center, which leads us to ........




Dacer said:


> Let's use the example of a 0 tiller & The angle of the string at full draw with respect to the nock point and the plunger. The angle made with the top limb is less than that made with the lower limb. This suggests to me that while the limbs work together the top limb is ahead in its individual draw cruve than the bottom limb's from the fact of being off center.
> 
> 
> A more extreme example would be to draw the bow back while putting your bow hand behind the top limb pocket and the draw hand appropriately place on the string. Draw the bow. The top limb clearly has more work done on it than the bottom limb as seen by the difference in displacement. More work done on the limb, more stored energy in that respective limb.


.......bow hand being approximately 2.5" below bow center, nocking point measured to be 2.25" above string center. Kinda evens out. In fact, I'm preparing to measure the angle and limb usage at full draw, watch this space.



Dacer said:


> Also I do think it has a direct effect on The feel of the bow hand becuase if my reasoning it correct it will effectively change where the pressure point of the grip is When the system settles into its equalibium at full draw.


The pressure point during draw is mostly decided by how much forearm muscle one wishes to utilise through flexing of the wrist. If one does not flex his or her wrist, the pressure point remains largely unchanged.




Dacer said:


> Simply my take on the mechanics of it, but I'm a lot better at calcuating molar flow rates than spring systems. However, That was fun.


We should do this again.


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## theminoritydude (Feb 11, 2013)

Mika Savola said:


> I 've almost always used negative tiller (1/8-3/16") on my bows. PB FITA 1288.


My wife shoots 1300+, positive tiller.


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## theminoritydude (Feb 11, 2013)

Dacer said:


> Perpendicular distance from the base of the limb as it come out of the limb pocket to the string. a -b = tiller a being the top limb and b being the bottom limb.
> 
> Atleast that's the conventinal way of doing it as documenting in various tuning and set up guides published by easton/hoyt and such. However I suspect if you aren't really worried about a true value and just a the relationship between the two limbs then as long as it's close to the limb pocket the exact place where it is measured isn't important as long as the individual remained consistant with his methods.


errrrrrrr something like that, not exactly but you got the part about the true value and the relationship between the two limbs quite right.

I wasn't talking about the definition of what constitutes a positive tiller. We all agree that it is as what you have stated. What I was lamenting about was the lack of a systematic approach to finding the appropriate tiller setting.


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## Mika Savola (Sep 2, 2008)

theminoritydude said:


> My wife shoots 1300+, positive tiller.


Good for her, is that with a compound bow...?


Joking aside, I was just trying to explain that it is possible to use negative tiller with good results. And this is something that came from experimenting, not by chance


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## theminoritydude (Feb 11, 2013)

Mika Savola said:


> Good for her, is that with a compound bow...?
> 
> 
> Joking aside, I was just trying to explain that it is possible to use negative tiller with good results. And this is something that came from experimenting, not by chance


I'll let her know that you gave her your compliments.

I am aware that good results have come from 0 tiller, and going negative is just one step further into reducing the positive tiller, so it wasn't hard to imagine. Having said that, what I wanted to demonstrate, is the idea that what seems to work well, may not be what works best.


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## BlackCheetah (Sep 28, 2007)

I've been wondering about what necessitates a change in tiller. It seems to me if you change tiller you'd have to retune everything.
I also have heard about setting tiller to keep the sight steady during the draw. But maybe there's a better way...
So what is it? How to find the best tiller setting? Let's hear it...


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## ThomVis (Feb 21, 2012)

My take on it: Tiller setting is to tune out the difference in power stroke between the top and bottom limb. You want the power stroke of both limbs to end at the same time, launching the arrow forward without it being dragged up or down by a residual power stroke difference. Top and bottom limbs are not created equal across the board, some being closer together than others. Lower or higher pressure in the grip caused by bigger/smaller hands or different hand position, drawing more on the index finger or ring finger, stabilizer weight trying to rotate the handle forward all influence how power is put into the limbs and thus influence tiller setting.
So I'm not interested in what exact value the tiller should be, I'm interested in how to get to the correct tiller for that particular archer/bow. Drawing the bow back watching the stabilizer (not) dipping or raising is a way to get a starting point. Watching the reaction of the bow and limb tips as the archer shoots and adjust accordingly to get to the final result.


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## Dusty Lee (Jan 11, 2015)

For myself as a beginning archer I found your thoughts on tiller to be an interesting read that somehow made sense to me . When I read your post to my husband who is an engineer and a mathematician , he laughed and said "exactly!"


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## Kendric_Hubbard (Feb 5, 2015)

Simon needham's book "archery: the art of repetition" offers a great deal of information about the importance of the tiller setting and tuning methods to ensure correct tiller. The basis of his thoughts about tiller is that the tiller should be set so that as the bow is drawn, the arrow does not experience any vertical movement.


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## Mika Savola (Sep 2, 2008)

IIRC Pete Carney posted some videos here a while ago, showing arrow behaviour at launch with different tillers. If somebody could dig them up...


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## chrstphr (Nov 23, 2005)

Pete Carney Gif

http://www.c3di.com/images/archery/form/tiller-comparison.gif


Chris


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## theminoritydude (Feb 11, 2013)

For every tiller setting, there is a nocking point position that allows the arrow to leave the string without tumbling. I am assuming Pete hadn't adjusted his nocking point position throught the demonstration.


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## TER (Jul 5, 2003)

theminoritydude said:


> For every tiller setting, there is a nocking point position that allows the arrow to leave the string without tumbling. I am assuming Pete hadn't adjusted his nocking point position throught the demonstration.


If I remember correctly, your assumption is correct.


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## Mika Savola (Sep 2, 2008)

Okay, if not with correct nocking point, those vids show nothing useful


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## Fury90flier (Jun 27, 2012)

Systematic approach to setting tiller?
Easy- well, sort of
this is what I was taught.
1. get a consistant grip and hook- if either one of these change, tiller value won't help much since both can effect how the limbs work.
2. once 1 is achieved- set tiller so that both limb tips come back to the same point at anchor, relative to the riser when the riser is plumb.

right now, tiller doesn't mean squat for me...my hook is junk (weight distribution isn't consistent)


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## Fury90flier (Jun 27, 2012)

chrstphr said:


> Pete Carney Gif
> 
> http://www.c3di.com/images/archery/form/tiller-comparison.gif
> 
> ...


nice link...thanks for sharing.

I like how the arrow bends differently based on tiller...very cool- never thought about that aspect of the tune with regard to tiller.

I'm having an issue with a particular shaft tuning...will be trying different tiller to see how that does.


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## theminoritydude (Feb 11, 2013)

I'm going to perform an experiment to prove a theory: All else being equal, maximum speed is achieved with optimum tiller setting.


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## Vittorio (Jul 17, 2003)

THA Chapter 3.1.. nothing to add as nothing is changed ...


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## Fury90flier (Jun 27, 2012)

theminoritydude said:


> I'm going to perform an experiment to prove a theory: All else being equal, maximum speed is achieved with optimum tiller setting.


before you go through a lot of effort (less you're just doing it for yourself), do some searching for tiller tests...I know I've seen the same test done already--- your theory is sound.

are you planning on doing it on a mechanical shooter or manually? if mechanically, how are you releasing to create the paradox?


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## theminoritydude (Feb 11, 2013)

The finger release is really not so different from a mechanical release, except that the finger release carries more mass, and hence imparts a significant amount of momentum. In fact all that needs to be done to create the paradox is to use a mechanical release with a similar amount of mass on the hook. A mechanical shooter should be easy to setup.

The point of the experiment is to discover the relationship between several other factors and the tiller, factors like grip (low, medium, high) which could be quantified by the pressure point on the bow's grip, the center of mass of the system and how it affects the tiller during the draw, the effect of tiller on different poundages,....the list goes on. Understanding these, we could then decide for ourselves how best to make tiller adjustments work for us.


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## limbwalker (Sep 26, 2003)

Tiller is an area I've always noticed that often gets discussed by club-level archers who struggle to break 1150. 

Quite a lot in fact.

I've never quite figured out why though.


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## jaredjms (Oct 24, 2007)

limbwalker said:


> Tiller is an area I've always noticed that often gets discussed by club-level archers who struggle to break 1150.
> 
> Quite a lot in fact.
> 
> I've never quite figured out why though.


....because their tiller is off


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## theminoritydude (Feb 11, 2013)

Vittorio said:


> THA Chapter 3.1.. nothing to add as nothing is changed ...


Sorry Vittorio. Don't have your book here. Is it a long chapter?


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## julle (Mar 1, 2009)

limbwalker said:


> Tiller is an area I've always noticed that often gets discussed by club-level archers who struggle to break 1150.
> 
> Quite a lot in fact.
> 
> I've never quite figured out why though.


:thumbs_up
Same with FOC


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## Ten_Zen (Dec 5, 2010)

It seems to me that the optimal tiller setting could be different for each limb/riser combination. Additionally, one could find the optimal setting using a mechanical shooting device, only to find that their release causes an entirely different behavior than the machine. 

In short, the reason no one knows what the optimal tiller settings are is because there are no such settings.


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## Dacer (Jun 10, 2013)

limbwalker said:


> Tiller is an area I've always noticed that often gets discussed by club-level archers who struggle to break 1150.
> 
> Quite a lot in fact.
> 
> I've never quite figured out why though.


I think it's safe to say that all areas regarding adjustments to equipment are discussed often at at length by 'club-level' archers. 

Possibly, maybe. Becuase at that level people have often naturally progressed to their lvl of natural talent - where to increase in performance would require actual training rather than casual practice. So if an equipment adjustment can get you a couple more points - it's the path of least resistance to a better score. 

I could be wrong though....

I think a more percise static yet someone dynamic way to get an optimal tiller would be to measure the angle of the string relative to the arrow at full draw for in reference to each limb. 

It could then be calculated what the optimum angle ratio, difference, or just in reference to one limb since the other would be simply be 120 - angle1. 

I would think that you would want to adjust this so that the angle of the string on either side of arrow would be equal. Could be a bad assumption. But that would effectively put the nock at the effective center of the string for an even timing of the top and bottom limbs. Given all other factors being constant.


That all said - probably easier to just adjust it until feel good and then move on.


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## theminoritydude (Feb 11, 2013)

Both limbs stop at the same time, regardless of the tiller. One limb cannot move beyond when the other limb stops. They stop each other.

Or more accurately, both limbs experience a sudden and abrupt deceleration, often with one limb travelling beyond the brace position, while the other travels back, followed by a decaying oscillation.


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## limbwalker (Sep 26, 2003)

> That all said - probably easier to just adjust it until feel good and then move on.


For 99.9% of archers, the "Ron Popeil approach" works best. In other words, set it and forget it. 



> Same with FOC


I completely agree. I bet you could ask 100 Olympic archers what their FOC is, and you'd get blank stares from 90 of them.

There are dozens of things in this sport worth worrying about. These are not two of them.


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## wesel (Sep 6, 2013)

limbwalker said:


> There are dozens of things in this sport worth worrying about. These are not two of them.


@limbwalker, now I'm very curious to learn some of, let's say, the most important things. Will you share your thoughts?


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## Giuliano (Oct 30, 2005)

Based on my personal experience I have to say that limbs do stop at the same time only when tiller and nocking point are correctly set.
A friend of mine has made an interesting work on this tuning, the link I try to post is to an Italian page but I guess a bit of Googling would be enough to understand it 
http://www.steghe.it/tesi-arco/tesi-arco.htm


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## ThomVis (Feb 21, 2012)

limbwalker said:


> I bet you could ask 100 Olympic archers what their FOC is, and you'd get blank stares from 90 of them.


Or if you ask it like that, some knuckles to the face.


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## limbwalker (Sep 26, 2003)

thomvis said:


> or if you ask it like that, some knuckles to the face.


lol.


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## limbwalker (Sep 26, 2003)

wesel said:


> @limbwalker, now I'm very curious to learn some of, let's say, the most important things. Will you share your thoughts?


When it comes to equipment, the things that matter are good setup (including setting your tiller to somewhere within the range the manufacturer recommends) and selecting the correct arrows. Not overbowing oneself, whether that's draw weight, mass weight or both. Good mental and physical preparation and proper technique.

Equipment is just one leg of the three-legged stool. The other two legs are: preparation (both physical and mental) and technique. All three have to be up to the task.

For split-fingered shooters (most all Olympic style shooters) they would do well to just find the natural tiller for the set of limbs they are using (you can do this by setting the limb bolts to the same setting, measuring the tiller, flipping the limbs and measuring again, and then halving the difference), and then just stick to that setting. For most limbs, that's somewhere between 1/4 and 3/8" strong (positive tiller) on the bottom limb.

Things like properly fitted and designed finger tabs and finger spacers for the individual, correct draw length adjustment (related to alignment, but not always), and a decent tune will always be more important than whether a bow's tiller is 1/4" off.

But none of that matters if an archer is shooting with poor technique, poor clicker control, poor endurance or a weak mindset.


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## theminoritydude (Feb 11, 2013)

Giuliano said:


> Based on my personal experience I have to say that limbs do stop at the same time only when tiller and nocking point are correctly set.
> A friend of mine has made an interesting work on this tuning, the link I try to post is to an Italian page but I guess a bit of Googling would be enough to understand it
> http://www.steghe.it/tesi-arco/tesi-arco.htm


Much appreciated Giuliano. However I am having some problems translating it at the moment, I will look into it again.

When I said that the limbs stop at the same time (with more precise description included to define the stop) it wasn't because of any experiences that I had myself, because that would be unnecessary. Logic dictates that if two bodies are in opposing motion while tied to a string acting as a constraint, at the moment of reaching that constraint, both bodies affect each others' momentum, concurrently.


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## Ten_Zen (Dec 5, 2010)

theminoritydude said:


> Much appreciated Giuliano. However I am having some problems translating it at the moment, I will look into it again.
> 
> When I said that the limbs stop at the same time (with more precise description included to define the stop) it wasn't because of any experiences that I had myself, because that would be unnecessary. Logic dictates that if two bodies are in opposing motion while tied to a string acting as a constraint, at the moment of reaching that constraint, both bodies affect each others' momentum, concurrently.


The string is not constraining the limbs while they are in motion. At the moment of release, the difference in the angle (A) between the limbs will affect the velocity of each limb subject to the same amount of force. See Diagram:


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## theminoritydude (Feb 11, 2013)

Ten_Zen said:


> The string is not constraining the limbs while they are in motion.
> View attachment 2168540


Both right and wrong, but that's irrelevant since it is not what I am describing.


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## Ten_Zen (Dec 5, 2010)

what I am trying to say is that there are three parts to this problem. The static forces and angles of the system (string and limbs) before the draw, the _dynamic_ forces of each limb on the string while in motion (limbs acting independently of each other during this time), and the "brace moment" or moment where full tension returns to the string and the limbs become a system again. the relative angle of each limb at this moment is not the same, causing a wave to travel through the string (like a towel being whipped). Depending on the relative angle (A) this wave will travel the string either from top to bottom (at brace moment) or bottom to top depending on which limb finishes its power stroke first which again depends on the relative angle (A) which is determined by the tiller.


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## theminoritydude (Feb 11, 2013)

Ten_Zen said:


> what I am trying to say is that there are three parts to this problem. The static forces and angles of the system (string and limbs) before the draw, the _dynamic_ forces of each limb on the string while in motion (limbs acting independently of each other during this time), and the "brace moment" or moment where full tension returns to the string and the limbs become a system again. the relative angle of each limb at this moment is not the same, causing a wave to travel through the string (like a towel being whipped). Depending on the relative angle (A) this wave will travel the string either from top to bottom (at brace moment) or bottom to top depending on which limb finishes its power stroke first which again depends on the relative angle (A) which is determined by the tiller.


I cannot agree to the statement that the limbs act independently of each other, even before the string reaches the brace. 

I like the idea you have presented, that a wave travels through the string, a result of such an independent motion of the limbs. However that premise invariably results in the string losing "traction" with the arrow in very extreme cases, but mostly to a certain minimal degree, still at least provide the constant push (constant, not in magnitude, but you know what I mean) on the arrow, thereby having a tension in the string, and in a way, still behaving as a variable constraint.

Returning to the point of relevance I was trying to bring to your attention, is the idea suggested by certain groups of very experienced "veterans" of the sport, that limbs can somehow stop independently of their opposites. That is simply untrue.


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## Ten_Zen (Dec 5, 2010)

Not 100%, there is still as you say the force of the arrow on the string causing tension which means they are still acting together. But they also have a degree of freedom (this is a classic analytical mechanics problem). Imagine you have two people each holding one side of a cloth, in the middle of the cloth is a large marble. If each person pulls on the cloth at the same time and at the same speed the cloth will snap the ball straight up into the air. Gravity is holding the tension in this case and when the limbs (people) engage, the cloth remains under tension through the "shot." However, if one limb (person) accelerates faster than the other, the ball will not fly straight up but will instead be whipped off to one side or another depending on who started first (try it for yourself). This is analogous to our situation. If one limb is at a steeper initial angle before the release it will accelerate faster than the other one and reach the end of its powerstroke first, therby causing the force to be distributed asymmetrically. Granted, this may be entirely negligible in reality, being vastly outweighed by the asymmetry of the archers hand placement and finger pressure. But if we are talking only about the physics of the bow itself, this is the situation im afraid.


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## Joe T (Apr 5, 2003)

Ten_Zen said:


> Not 100%, there is still as you say the force of the arrow on the string causing tension which means they are still acting together. But they also have a degree of freedom (this is a classic analytical mechanics problem). Imagine you have two people each holding one side of a cloth, in the middle of the cloth is a large marble. If each person pulls on the cloth at the same time and at the same speed the cloth will snap the ball straight up into the air. Gravity is holding the tension in this case and when the limbs (people) engage, the cloth remains under tension through the "shot." However, if one limb (person) accelerates faster than the other, the ball will not fly straight up but will instead be whipped off to one side or another depending on who started first (try it for yourself). This is analogous to our situation. If one limb is at a steeper initial angle before the release it will accelerate faster than the other one and reach the end of its powerstroke first, therby causing the force to be distributed asymmetrically. Granted, this may be entirely negligible in reality, being vastly outweighed by the asymmetry of the archers hand placement and finger pressure. But if we are talking only about the physics of the bow itself, this is the situation im afraid.


You are forgetting that the limbs are coupled together via the riser (which is the whole point of the "tiller" topic - as in how the limb/arrow acceleration affects the riser). As a very bad analogy  suppose that the two hands holding the cloth above were connected together via a rope running through a pulley attached to the ground between them.


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## theminoritydude (Feb 11, 2013)

I'm going to digress a little here because this is going to be interesting.

You have made a couple of assumptions here, I assume.
1) Each person has the autonomy to initiate his own pull. 
2) The marble (ball) is locked in its lateral position on the cloth.
3) Limbs behave like the two individuals, with respectively defined stops.

Am I right in all 3 counts?


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## Ten_Zen (Dec 5, 2010)

Sigh. Joe, the whole point of the analogy is to show the asymmetric force distribution through the string caused by varying lateral acceleration of both ends. If they both start at the same time with different acceleration vector magnitudes... follow? If not, Im gonna stop here. As they say in my Analytical Mechanics class where we study these phenomena all day long "further analysis left as an exercise for the student." Don't beleive me? Set up the Lagrangian and solve the partial differential equations and see for yourself.


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## Joe T (Apr 5, 2003)

Ten_Zen said:


> Sigh. Joe, the whole point of the analogy is to show the asymmetric force distribution through the string caused by varying lateral acceleration of both ends. If they both start at the same time with different acceleration vector magnitudes... follow? If not, Im gonna stop here. As they say in my Analytical Mechanics class where we study these phenomena all day long "further analysis left as an exercise for the student." Don't beleive me? Set up the Lagrangian and solve the partial differential equations and see for yourself.


"_whole point of the analogy is to show the asymmetric force distribution through the string caused by varying lateral acceleration of both ends_"
I agree (the static string force at full draw is also asymmetric either side of the fingers  ). My point was that a) the limbs don't accelerate independently as they are connected at both ends and b) tiller has nothing to do with the arrow (marble) but with with the riser behaviour, the limb forces on the riser pockets.


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## theminoritydude (Feb 11, 2013)

TenZen, I am going to assume that you believe that the limbs stop at the very same locations as when the bow is not draw. Correct me if I'm wrong.


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## Ten_Zen (Dec 5, 2010)

theminoritydude said:


> TenZen, I am going to assume that you believe that the limbs stop at the very same locations as when the bow is not draw. Correct me if I'm wrong.


No. that would only occur if the acceleration vectors were exactly the same for each limb and if their displacement from equilibrium were equal (and if they were made of perfect materials with constant coefficients and a string that had no ability to stretch). In general real world problems rarely achieve perfect symmetry


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## theminoritydude (Feb 11, 2013)

Ten_Zen said:


> No. that would only occur if the acceleration vectors were exactly the same for each limb (and if their displacement from equilibrium were equal). Neither of these conditions are generally true.


To be fair, the acceleration vectors for each limb does not have to be the same, and neither do their displacements for that condition(or something close to it) to occur.

Having said that, I just wanted to eliminate the possibility of you confusing limb stop with limb position at brace. Now we can disregard this.


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## Ten_Zen (Dec 5, 2010)

Consider a rope being held at each end by two oscillators with the same frequency. A symmetric wave with a node at each end will appear in the rope. Vary the frequency of one node and you break the symmetry of the wave. Again. This all goes back to the diagram. Angles A and B determine the initial velocity and acceleration of each limb. The angles are not the same, therefore the force on each limb is not the same. F = ma so that means the acceleration vectors will not be equal, meaning one limb will reach the end of its power stroke before the other. This means that one side of the string will have moved further than the other , causing a wave to travel up or down the string depending on which side finished moving first. I cannot explain this in more simple terms than this. I hope that helps.


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## theminoritydude (Feb 11, 2013)

No one is disputing the fact that the two limb tips (or where the string is just leaving the contact of the limb) are very possibly moving at different speeds and accelerating differently. 

The issue here is what you defined as the end of the powerstroke for one limb, and the other is still a distance away from its end. There is no such thing. The two limb tips are "coupled" by the string. Their end of the powerstroke is determined by each other, and occur at the same time.

What happens immediately after the end if their powerstroke, is that most likely, they have not settled in their original brace positions, hence begins a phase of returning to that position, visible to us as a minute limb flutter.


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## theminoritydude (Feb 11, 2013)

If you could tear yourself away from the math of it and picture the whole thing in your head. I'm not saying your math is wrong, it is rudimentary and simple but very likely to be correct, but your modeling may be off.


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## Ten_Zen (Dec 5, 2010)

theminoritydude said:


> No one is disputing the fact that the two limb tips (or where the string is just leaving the contact of the limb) are very possibly moving at different speeds and accelerating differently.
> 
> The issue here is what you defined as the end of the powerstroke for one limb, and the other is still a distance away from its end. There is no such thing. The two limb tips are "coupled" by the string. Their end of the powerstroke is determined by each other, and occur at the same time.
> 
> What happens immediately after the end if their powerstroke, is that most likely, they have not settled in their original brace positions, hence begins a phase of returning to that position, visible to us as a minute limb flutter.


Ah, okay I see where the confusion is. So yes, the brace moment happens at the same time for each limb because the string reaches full tension in that moment, however, that is not to say that each limb has travelled the same distance in that time, and depending on the relative difference in the angles of each limb at brace determines the asymmetry of the motion in the string in that moment.


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## MAT (May 27, 2003)

It seems like you guys are ignoring the arrow on the string. If it’s not in the middle it’s also exerting uneven forces on the limbs, either speeding one up or slowing one down. If you draw a bow well off center you’ll see the shorter string side draws that limb more, which means there a different mechanical advantage (leverage) based on the geometry of the string/limb angles. When shot the shorter string side limb has less of a mechanical advantage (more force is needed to move the arrow) so it’s slower. Isn’t this the real reason for tiller?


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## Ten_Zen (Dec 5, 2010)

theminoritydude said:


> If you could tear yourself away from the math of it and picture the whole thing in your head. I'm not saying your math is wrong, it is rudimentary and simple but very likely to be correct, but your modeling may be off.


I am not going to debate the complexity of Lagrangian Formalism. I doubt you have ever heard of it or have any idea how rudimentary or simple it is or isnt. If you had, you probably wouldnt be confused about this.


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## theminoritydude (Feb 11, 2013)

MAT said:


> It seems like you guys are ignoring the arrow on the string. If it’s not in the middle it’s also exerting uneven forces on the limbs, either speeding one up or slowing one down. If you draw a bow well off center you’ll see the shorter string side draws that limb more, which means there a different mechanical advantage (leverage) based on the geometry of the string/limb angles. When shot the shorter string side limb has less of a mechanical advantage (more force is needed to move the arrow) so it’s slower. Isn’t this the real reason for tiller?


It doesn't matter if it is in the middle or away. The fact that the bow hand is below the bow center already subjects the system to asymmetry at the onset of the draw.


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## theminoritydude (Feb 11, 2013)

Ten Zen, I was referring to F=MA.


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## Ten_Zen (Dec 5, 2010)

Yes, this I would say is the primary reason (asymmetric initial conditions). I am simply trying to explain the dynamics of the system by considering only the asymmetry of the limbs. But as I said before the other asymmetries are likely to far outweigh the affects of an asymmetric tiller with all other things being perfiectly symmetric.


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## Joe T (Apr 5, 2003)

If you check the archery bibliography under recurve stabilisation (zanevsky) you will find a Lagrangian approach to the vertical plane bow behaviour.

Unfortunately as regards tiller the effect of gravity is not included

https://sites.google.com/site/archerybibliography/bow-stabilisation


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## theminoritydude (Feb 11, 2013)

Joe T said:


> If you check the archery bibliography under recurve stabilisation (zanevsky) you will find a Lagrangian approach to the vertical plane bow behaviour.
> 
> Unfortunately as regards tiller the effect of gravity is not included
> 
> https://sites.google.com/site/archerybibliography/bow-stabilisation


Funny you should mention gravity. I once asked a bow manufacturer the effects of gravity on the lower limb, and he replied that it was not taken into account.


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## Joe T (Apr 5, 2003)

theminoritydude said:


> Funny you should mention gravity. I once asked a bow manufacturer the effects of gravity on the lower limb, and he replied that it was not taken into account.


That was the correct answer. 
Solution to tiller is the stabilizer system not the limbs.


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## theminoritydude (Feb 11, 2013)

Has this been verified in real world tests? I understand the effects to be minuscule, but I was interested in running a testing rig where I am suspended upside down.


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## MAT (May 27, 2003)

theminoritydude said:


> It doesn't matter if it is in the middle or away. The fact that the bow hand is below the bow center already subjects the system to asymmetry at the onset of the draw.


Whatever the location of the hand has on the bow has during the draw will not be there after the release which will have no effect on the limbs closing speed (if the riser does not move). The arrows location on the string will be much more important to the closing of the limbs. All your hand is doing is holding the riser basically counteracting the reaction of the arrow and limbs moving forward. If the arrow is not in the center of the string there will be different forces on the limbs, so zero tiller will result in different closing speeds. Is this not what tiller is about?


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## Joe T (Apr 5, 2003)

> Has this been verified in real world tests?


Virtually nothing in archery has been verified by "tests". Most reported tests are of the amateur garden shed variety and can't really be taken seriously. The real testing is done by many archers and manufacturers continually trying to improve performance over many years of trial and error. This process is remarkably effective. 




MAT said:


> Whatever the location of the hand has on the bow has during the draw will not be there after the release which will have no effect on the limbs closing speed (if the riser does not move). The arrows location on the string will be much more important to the closing of the limbs. All your hand is doing is holding the riser basically counteracting the reaction of the arrow and limbs moving forward. If the arrow is not in the center of the string there will be different forces on the limbs, so zero tiller will result in different closing speeds. Is this not what tiller is about?


cf the marble on the pulled cloth above whatever the limb force balance is the arrow nock (marble) is positioned so that it goes straight up and not to the side (aka nocking point tuning). Tiller is not about limb closing speeds. Tiller is about the riser pivoting around the bow hand as a consequence of the different limb-riser reaction forces at the top and bottom limb pocket. You can reduce this riser rotation by having different limb-riser angles top and bottom but it's only going to be partially effective. A far better way to eliminate riser rotation is to use the stabilizer system.


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## Joe T (Apr 5, 2003)

Ten_Zen said:


> The string is not constraining the limbs while they are in motion. At the moment of release, the difference in the angle (A) between the limbs will affect the velocity of each limb subject to the same amount of force. See Diagram:
> 
> View attachment 2168540


The source of that figure was a web page built by someone going around the internet copying and pasting stuff (often tarting it up), ignoring any copyright notices and often getting the rehashed stuff technically wrong. 

The amusing bit is - here is the original drawing (written by me so long ago I can't remember when) and it relates to the *static* draw force










"_The weight on the fingers is 2FCos(A)Cos(B). (The factor 2 comes from having two, assumed identical, bow limbs)._"


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## Vittorio (Jul 17, 2003)

Joe T said:


> That was the correct answer.
> Solution to tiller is the stabilizer system not the limbs.


You have summed it up perfectly !


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## theminoritydude (Feb 11, 2013)

Joe T said:


> Virtually nothing in archery has been verified by "tests". Most reported tests are of the amateur garden shed variety and can't really be taken seriously. The real testing is done by many archers and manufacturers continually trying to improve performance over many years of trial and error. This process is remarkably effective.


I was talking about the garden shed variety. They do represent the real world. Not perfect.


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## wfocharlie (Feb 16, 2013)

theminoritydude said:


> Has this been verified in real world tests? I understand the effects to be minuscule, but I was interested in running a testing rig where I am suspended upside down.


If you do this please post it on youtube.


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## regas (Oct 24, 2013)

https://www.youtube.com/watch?v=kTcRRaXV-fg&list=RDkTcRRaXV-fg#t=44

which one of you is lou?


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## theminoritydude (Feb 11, 2013)

wfocharlie said:


> If you do this please post it on youtube.


Oh, YouTube would probably be the only reason to do something like this.


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## spogshd (Mar 14, 2014)

limbwalker said:


> When it comes to equipment, the things that matter are good setup (including setting your tiller to somewhere within the range the manufacturer recommends) and selecting the correct arrows. Not overbowing oneself, whether that's draw weight, mass weight or both. Good mental and physical preparation and proper technique.
> 
> Equipment is just one leg of the three-legged stool. The other two legs are: preparation (both physical and mental) and technique. All three have to be up to the task.
> 
> ...


So are you saying the bottom tiller is larger than the top


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