# Tiller Tuning?



## JAVI (Jun 19, 2003)

last-in-line said:


> I shoot back tension and like to pull hard against the wall, but when I do it seems to pull my pin down. I've heard you can adjust tiller to help the bow to point (aim) better. Any sugestions?


What kind of bow???


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## last-in-line (Jul 28, 2004)

It's a Merlin Max 2000 w/Rapid cams (dual).


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## JAVI (Jun 19, 2003)

I would have to ask first... if you bottom out the limbs is the tiller even? and if not.. have you timed the cams....????


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## last-in-line (Jul 28, 2004)

Tiller is dead even. Both cams have stops and they hit at the same time as far as I can tell. The bow shoots as good of groups as I can, it just seems like the geometry is such that when I pull against the wall, it pulls the pin down.


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## JAVI (Jun 19, 2003)

*try this before you attempt to tiller tune...*

which is only a method of changing nock travel on a cam assisted bow...

This was written By GRIV... some time ago for the two cam bows...

*Creep Tuning*

By "GRIV" George Ryals IV



Here is a blurb that I wrote in another thread and it basically describes creep tuning and why it works and why it is needed.

Nock travel has three factors, the measured center of the bow and the shooting center of the bow (plane of the arrow’s flight), and the shape of the cam systems. If your two cam bow is timed around the measured center of the bow and you shoot the bow through the measured center you will have level nock travel. The problem is you can’t really shoot an arrow effectively out of the measured center of the bow and hold the bow at the measured center. You could just hold it below the measured center and shoot the arrow out of the middle. This balance condition makes it very hard to aim as steady as possible and they do not recover well from muscle tremors. In my opinion, those handles that are all sight window are not a good design.

The best method is to design the bow with great balance by setting the measured center of the bow between where you hold it and where the arrow flies through it. This creates a well balanced symmetrical riser design that works with the shooter and is very easy to control and the arrow is as close to the measured center as possible. Then when you Creep Tune your two cam bow, you will set up the nock travel to be behind the shooting center of the bow rather than the measured center. Usually this will cause the top cam to be a half twist advanced because the shooting center of the bow is ¼” above the measured center.

Creep Tuning will automatically set your cam timing to the shooting center of the bow and give you the optimum nock travel condition. Creep Tuning is designed for Dual Cam Systems. However if your single cam system or Hybrid System has the straight and level travel that it says it has, you will get optimum results when the bow is tested. If not, Nock travel is present, and there are few options to adjust them to straighten it out.

For those of you unfamiliar with Creep Tuning, here is a little review.

The Creep Tune Procedure
The Creep Tune procedure is as follows:

1. Set the timing as close as you can by eye (you don't have put a micrometer on it; just get as close as you can)

2. Sight your bow in at twenty yards.

3. Put a piece of masking tape on your target butt horizontally. In a pinch, you can use the top edge of a target face.

4. Pull your bow into the wall as hard as you can and shoot arrow #1 at the tape.

On the next shot, creep forward to the front of the valley and shoot arrow #2 at the tape. You make need to re-shoot these shots a couple of times to rule out bad shots.

5. If your bow is in perfect time, both arrows will hit the tape or they will land on the same horizontal plane. (Level with the tape or on the tape)

If the "creep" shot hits HIGH, TIGHTEN or SHORTEN the cable that connects to the BOTTOM cam.
If the "creep" shot hits LOW, TIGHTEN or SHORTEN the cable that connects to the TOP cam.

Make very small, one or two turn, adjustments a time. A little twist goes a long way. You can fine-tune your timing by repeating the test at forty yards. If you make an adjustment at this distance do not turn your cable more that a half a turn at a time. Too much adjustment at this distance can send an arrow over the target butt or in the dirt. When you have completed the test, your bow will be in perfect time, and given that your other accessories are adjusted properly, your bow is as accurate as it can possibly be.


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## last-in-line (Jul 28, 2004)

Thanks Javi, I can see how creep tuning will improve grouping, but forgive my ignorance, I don't see how it would change how the bow points at full draw.


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## JAVI (Jun 19, 2003)

If one cam is rotating slightly more than the other it will pull the bow if you pull hard into the wall....

The mechanical advantage of the cam will not really allow tiller tuning except as a method of moving the nock point/travel...

You can prove this by putting the pivot point of the grip on a 3/4" bolt and pulling the bow back... even with one limb backed out 5 turns and the other bottomed out the bow will not pivot... The cams make the limbs work together...


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## last-in-line (Jul 28, 2004)

Thanks much...I get it now. Creep tuning tomorrow!


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## TWesley (Sep 14, 2002)

Last-IN-Line

I think you want to take weight off the top limb. If I were you I take 1/2 a turn off the top limb.

I am suggesting you take 1/2 turn off in order to verify your doing the right thing because I could be telling you to adjust the wrong limb... 1/2 turn will make a big difference. If it helps, put the 1/2 turn back on and move the tiller in 1/8 or 1/4 turns untill you get it like you want it.

TW


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## bowbender7 (Jun 1, 2002)

Adjusting tiller on a compound does little more than change the relationship of the grip (whole riser) angle to the string.

Maybe moving some weight from the end of the stab to the rear of the bow would help?


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## ex-NFO (Sep 20, 2003)

bowbender7 said:


> Adjusting tiller on a compound does little more than change the relationship of the grip (whole riser) angle to the string.


I disagree. I've been having a problem shooting indoors, with the shoulder of my bow arm getting tired very quickly. I figured out that the cause was downward pressure from the lower limb, based on where the nock was set. I compensated by adding a full turn to the top limb, and taking a full turn off the bottom limb. This kept the draw weight the same, and the upper limb is now the stronger limb. 

At full draw, the upper limb now helps me hold the bow on target at full draw, and I don't get tired anymore. I also find it much easier to settle on the x now.


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## bowbender7 (Jun 1, 2002)

Martineer, If you made the alteration and still have the same draw weight - no limbs were weakened or strengthened. 
What you did is facilitate a lower wrist grip which allows a little more heel pressure which can very well aid in not dropping out the bottom of the spot.

I most respectfully state that tiller adjustments on your compound only alter the grip to string angle relationship. The cams will bend the limbs equally regardless of how many turns in or out they are.

There are instances where a pair of limbs are not matched very close in deflection - this is where tiller came from initially - the idea being that say you have a stiffer limb on the top for instance, you can back out that limb to make the tiller measurements match at rest or full draw.


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## ex-NFO (Sep 20, 2003)

I'm sorry, I don't see it. If I look at a bow at full draw, both limbs tips deflect the same amount. If the base of the top limb is cranked down farther to the riser, that limb will be pre-stressed more. 

If that's the case, the force applied from the top of the string will tend to pull the bow up, bring the system back into equilibrium. The draw weight is the sum of forces applied by both limbs, which wouldn't therefore change.

I agree that tiller tuning is also useful in accounting for limb mismatch.



bowbender7 said:


> Martineer, If you made the alteration and still have the same draw weight - no limbs were weakened or strengthened.
> What you did is facilitate a lower wrist grip which allows a little more heel pressure which can very well aid in not dropping out the bottom of the spot.
> 
> I most respectfully state that tiller adjustments on your compound only alter the grip to string angle relationship. The cams will bend the limbs equally regardless of how many turns in or out they are.
> ...


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## JAVI (Jun 19, 2003)

*some of y'all need to read this...*

http://homepage.ntlworld.com/joetapley/tiller.htm


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## ex-NFO (Sep 20, 2003)

I'all read it, and what I got out of it was a recommendation to stiffen the bottom limb to create a more level nock travel, which I understood was not the point of the thread. I thought the point of the thread was to adjust the tiller to hold more easily.


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## bowbender7 (Jun 1, 2002)

Imagine a see-saw with two equal weight kids that can balance each other. Now imagine a fat kid swaps places with one, you are thinking that that only the fat kids side of the seesaw will be affected, but I think you realize that is not the case. As one side goes up, one side comes down. Its the same thing with bow limbs.
The riser becomes the fulcrum and the harness pivots on this fulcrum.
If you observe a bow with matched limbs, both set three turns out and everything looks symmetrical then tighten the top limb in three turns you have decreased the brace height of that limb and increased the brace ht of the other. They are both still prebent the exact same amount. How could they not be, you cant tell one limb tip to stay put while you tighten the other.
They both will react proportional to any adjustments. 
You mentioned the amount of tip travel but failed to see that because of your tiller alterations, the limb tips are both starting their movement from a different location in relation to the riser.
Limbs are bound to each other with the harness system, just because you adjusted one limb, you are failing to see that this adjustment is reflected in the opposite limb because they in effect are affixed to each other. Your harness length does not change because you only adjust one limb bolt any more than one limbs deflection is affected.

Why dont you try the old fashioned Larry Wise method of measuring limb deflection with a carpenters square, then you will see that they are both the same regardless of your limb bolt adjustments.

I am am not stating that tiller tuning does not work, it can since it changes the pressure point of the bow system. Only because you are altering the grip angle though. I just cant help but point out that contrary to popular belief, you are NOT changing only one limbs stiffness by adjusting limb bolts.

Now if you take one limb off the bow and grind on it with a drum sander, you will change how 
much that limb bends


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## JAVI (Jun 19, 2003)

bowbender7 said:


> Now if you take one limb off the bow and grind on it with a drum sander, you will change how
> much that limb bends


Yep... there ya' go... shaving the limb is how we adjusted the tiller on our old re-curves and stick bows...

Damn am I that old...????


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## ex-NFO (Sep 20, 2003)

Ok, I'll go home, measure with a carpenter's square, and report back. For both limbs to be pre-stressed the same, the matching legs of the right triangles need to be the same.


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## TWesley (Sep 14, 2002)

Last-IN-Line

Adjusting the top limb bolt will do one of three things

1. Make the top limb stronger than the bottom limb.
2. Make the top limb weaker than the bottom limb.
3. Make the top limb exactly the same as the bottom limb.

If your like most people, you sight your bow at full draw. Therefore I wouldn't spend to much time attempting to get the bow to aim well at rest.  

TW


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## bowbender7 (Jun 1, 2002)

Martineer, make sure you measure with your tiller arrangement and again with limb bolts set to even amount of turns so you have a reference.


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## ex-NFO (Sep 20, 2003)

bowbender7 said:


> Martineer, make sure you measure with your tiller arrangement and again with limb bolts set to even amount of turns so you have a reference.


Right, because the limbs might not match exactly.


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## JAVI (Jun 19, 2003)

What some of y’all are missing is that a bow limb is nothing but a leaf spring… plain and simple… it has a specific rate of pounds per inch of travel. The amount of pre-load will have no effect on this period… Well ok… it will if you exceed the travel limit of the spring…. But that will usually result it bits of carbon fiber flying about…

The bow riser acts as a coupling between the two halves of the spring, it does not act as a fulcrum. The reason adjusting the pre-load on one limb affects the bow is that it will rotate the cam slightly thus moving the nock point. 

If you move the nocking point you change the pressure point on the grip, this is why some folks think it is improving the holding of the bow…

If you tend to heel the bow then adjusting the tiller will in effect compensate by ******ing or advancing one cam…

This is also why some people feel that they shoot better with one cam ******ed to the other…

If you want to adjust the weight of a single limb you must change the spring rate… this can only be accomplished by adding or removing material or by lengthening or shorting the limb… 

If the limbs are not matched in rate form one to the other, changing the preload, still will not match the pounds at a specific travel...


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## bowbender7 (Jun 1, 2002)

Javi, I didnt mean to imply that the riser IS a fulcrum, only to think of that way in reference to tiller adjustments. When the bow is drawn, the riser is only a coupler.

I do have to disagree that the cam is rotated however. It appears to be rotated in relation to the limb because the limb forks intersects a different area of the cam when in fact it is the limbs location that is moved. The whole limb tip, cam assembly and harness is moved up and down with tiller adjustments.


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## JAVI (Jun 19, 2003)

bowbender7 said:


> Javi, I didnt mean to imply that the riser IS a fulcrum, only to think of that way in reference to tiller adjustments. When the bow is drawn, the riser is only a coupler.
> 
> I do have to disagree that the cam is rotated however. It appears to be rotated in relation to the limb because the limb forks intersects a different area of the cam when in fact it is the limbs location that is moved. The whole limb tip, cam assembly and harness is moved up and down with tiller adjustments.


Sean... if you check the timing of the cams after a pre-load adjustment of the limbs you will find that it has changed.... that can only happen if the cam rotation is altered...


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## TWesley (Sep 14, 2002)

Bowbender7: Your dead on with the tiller. Do you know the answer to this question. Does changing the angle of the handle in relation to the string not change the clock position of the Cams in relation to the limbs?

I think it does, but I am not sure. If the clock position of the cam changes, the leverage the cam has on the limb changes, which would have the same effect as shaving one limb.

TW


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## ex-NFO (Sep 20, 2003)

Hmmm. Since I'm being sent off to measure something, I'm sure it will come back as expected. 

So, I guess what you're saying is that any pre-load applied to the base of one limb, will in effect be applied to the tip of the other limb because it's a closed system.

I wonder about the cam not rotating however. In looking at the lobes of the top and bottom cams after adjusting the tiller, one is clearly contacting the string further down than the other.


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## bowbender7 (Jun 1, 2002)

Javi, I think the reason the timing may need adjustment is because now you have a brand new pressure point in the grip area.

Yes it changes the closk position of the limbs, not the cams. To truly change the position of the cams you would have to alter the harness.

As a preface to all stated above, I use to think that you could change the stiffness of one limb with limb bolt adjustments. That is until I started building board bows (longbows made from kiln dried lumber) and read extensively on finish tillering a recurve or longbow. When I had a rough longbow on the tillering board, I found that if I had to remove material from one limb to weaken it, not only did the brace on that limb go up, the other went down without even touching it. I learned quickly that I had to be very carefull as any material removed had a much fgreater effect than one would have thought. This caused my to realize that as Martineer put it, it is a closed system with alterations being shared, even if conversely.


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## JAVI (Jun 19, 2003)

The limb is pivoting on the rocker, which is acting as a fulcrum in this case so by changing the angle of attack, you are causing the cam to rotate. 
It still will not change the spring rate of the limb, and since the other cam is rotated in the opposite direction the limbs will still move the same amount.

This is especially true of the hybrid cam bows because the string is just along for the ride… 

What gives the illusion of changing the limb rate is the moving of the nock point, causing you to apply either up or down pressure on the string…



Want to try and experiment… set the limbs to even (bottomed out) and the cams in time… then set a nock point a ¼ above your normal one, and one a ¼” below the normal… then draw the bow using each in turn…. The grip pressure (angle) will change drastically.


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## TWesley (Sep 14, 2002)

Javi

A bow with a hatchet cam is a good example. You have even tiller at full draw and when you look at the limbs it looks like you can draw a line down the limb and straight down the flat spot on the cam. If you took up on the top limb and backed off on the bottom limb it should change the relationship between the cam and the limb. Now the top cam would be rotated past straight with the limb and the bottom cam would be short of straight with the bottom limb.
Is that right or wrong?


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## JAVI (Jun 19, 2003)

Troy...

That's pretty much correct... but measure the deflection of each limb and you will see that each is moving the same as before the change in pre-load...

On most bows the top and bottom limbs will bend different amounts because the grip/nocking point is not in the middle of the bow... But the rate of the limbs will be the same...

By the way I'm glad to see you back to posting, and I enjoyed talking to you in Temple...


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## TWesley (Sep 14, 2002)

Yes, but my point is the cam has leverage on the limb. As it relates to aiming a bow that wants to climb or fall, changing the leverage the cams have on the limbs, will change how the bow aims. Just as if you actually had made one limb weaker or stronger than the other one.


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## JAVI (Jun 19, 2003)

TWesley said:


> Yes, but my point is the cam has leverage on the limb. As it relates to aiming a bow that wants to climb or fall, changing the leverage the cams have on the limbs, will change how the bow aims. Just as if you actually had made one limb weaker or stronger than the other one.


I'm not disagreeing with that, I'm just saying it is an illusion and can be accomplished by other methods with less effect of the timing and cam roll over which can effect the efficiency of the bow.


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## TWesley (Sep 14, 2002)

I'v got a head ache now, I think I'll take up beach volly ball. Last-IN-Line, sell the damn thing and buy a gun.


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## JAVI (Jun 19, 2003)

TWesley said:


> I'v got a head ache now, I think I'll take up beach volly ball. Last-IN-Line, sell the damn thing and buy a gun.


That's why I quit shooting and just work on the little buggers...


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## bowbender7 (Jun 1, 2002)

JAVELINA said:


> Sean... if you check the timing of the cams after a pre-load adjustment of the limbs you will find that it has changed.... that can only happen if the cam rotation is altered...


If you take a couple turns out of the top limb, your nock point is lower. Now if you lower your pressure point on the grip the same amount - the bow is still in time.


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## Jabwa (Dec 10, 2004)

Tiller does 2 things to a bow: 1. Changes the nock point 2. Changes the angle of the riser. (It may also change the timing slightly). It is the second point that may concern the ORIGINATOR of this post.

By changing the angle of the riser you can change the shooters hand pressure slightly. I would guess that turning the bottom limb bolt in will cause a little more "palm pressure" on the handle and force the sight up slightly at full draw.


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