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How to set your bow's tiller

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How to set your bow's tiller

Old 12-08-2007, 04:49 PM
  #1  
Giant Nontypical
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Default How to set your bow's tiller

Arthur originally posted this as a response to a question, but since it contains so much good and oft-overlooked technical information, I think it should join the ranks of the pinned.

I am interested in why you wouldn't want your upper and lower tiller measurements to be the same;
If the grip, arrow rest and nock point were all centered in the bow, then even tiller would be perfect. But it's not that way. The grip is below the arrow, below the nock point and below center in the riser. So you're putting pulling forcein one plane, pushing forcein another.

Generally, consider the riser a lever and the grip as the fulcrum. The grip/fulcrum is closer to the bottom end of the riser than to the top end. So the top end of the lever is longer than the bottom. Basic gradeschool physic tells us that the top end has greater mechanical advantage and we either have to increase the weight on the bottom end, or decrease the weight on the top end, in order to balance the lever over the fulcrum.

But if you would prefer to leave the physics out of it (and I really hope you would prefer it) there is an easy way to see it. Just pick up your bow, aim a sight pin at a point on the wall and, slowly, begin drawing straight back. If you've got your bow set at even tiller, the effect should be immediate as soon as you apply the first bit of drawing force.

The bow will rock back in your hand and the pin will lift up, off the spot. The reason is the top limb, on the long end of the lever, has more mechanical advantage than the bottom limb and is overpowering it. Now, if you pull on back through the breakover to full draw, stabilize the hold on the spot and release an arrow, what do you think that bow is going to do? It will do exactly the same on the shot as it did during the draw! The bow will rock in your hand again during the shot.

The result is you will feel the bow's movement as shock or vibration. It might make more noise than it should.Your bow will be harder to hold on target than it should be, with the limbs straining and fighting against each other. You will have a harder time tuning the bow because you have to fiddle around with adjustments until you find the exact spot in that rocking motion where the arrow finally leaves the bow. The bow's rocking motion guarantees your nock travel will not - CAN NOT - be straight and level.

So, what to do? Well, assuming the pin lifts UP off the target, you add weight to the bottom limb bolt, reduce the weight on the top limb bolt or both. You make a small adjustment, like 1/4 to 1/2 turn, then repeat the 'pick a spot and draw' test. You keep adjusting until you can put that pin on it's spot and draw straight back without it wanting to either lift up off the target or sink below it.

That's a simple, down and dirty way to adjust the bow's dynamic tiller, to custom match your individual grip. There are other, more complicated and involved ways of doing it, but this is very easy and plenty good enough for all but the very best, world class type shooters.

...and generally what bow problems could be "fixed" by playing with the limb bolts to tune the tiller specs.
As I've mentioned, it will keep the bow from rocking at the shot. So, you will feel less recoil and vibration during the shot. It will make the bow holdmore steady and stable during aiming. It will make the bow easier to tune because you're not having to compensate for the rocking motion and your nock movement is straighter and more level. It will likely make the bow quieter. In fact, with the limbs balanced and working together during the shot, it is very likely that you will see a smallincrease in arrow speed, even though you might have reduced your draw weight by a couple of pounds.

Some say tiller doesn't matter on single cam bows and I've always said that's a load of rubbish. It works just the same on any bow, no matter what style cam(s) it has.

Now, doing this tiller adjustment will most likely cause your nockset to move, so you might not want to mess with it until after hunting season is over. You will also have to move your peep and any other string mounted anchor references (like a kisser). But the time you save in tuning your arrow flight will more than offset the time it takes to do this.


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Old 12-09-2007, 10:29 AM
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Default RE: For Roscoe - Tiller

Wow- thanks Arthur! I'm thinking I may have done my new Reflex bow a dis-service by backing of the lower limb bolt a little to even up the tiller. You think the bow manufacturers would build some elements into the design of bows to compensate for this basic imbalance . . . . .
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Old 12-09-2007, 10:46 AM
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Default RE: For Roscoe - Tiller

Yeah, well it's not really possible to do that. No two people hold a bow exactly the same way, so tiller would vary from one person's bow to the next. For folks who shoot fingers, there's a significant difference in tiller for someone who shoots 3-under than for someone who shoots split finger.The 3-under shooter will need his tiller closer to even than the split shooterm because he is pulling under the arrow rather than behind it. Same for a release shooter who uses a nockset/cushion button arrangement to hook up under the arrow vs someone who uses a string loop behind the arrow.

What baffles me is why the manufacturersdon't give good info on tiller adjustmentin their tuning instructions. All you get from them is 'just set it even and go on.' After checking my axle to axle, brace,cam timing/synchand setting a temporary nockset,tiller adjustment isthe first thing I get set when I start a major tune-up.
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Old 12-09-2007, 11:04 AM
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Default RE: For Roscoe - Tiller

So let's say you start your major tune up. And you are getting a slightly low tear in the paper (assuming you go paper tuning first). Are you going to raise the nocking point, lower the arrow rest, or adjust the tiller?
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Old 12-09-2007, 03:36 PM
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Default RE: For Roscoe - Tiller

My tiller is already set, remember? And I like my arrow rest set so that the arrow is level with the mounting screw hole, so that stays put. I adjust the nock point.
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Old 12-09-2007, 07:11 PM
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Default RE: For Roscoe - Tiller

Stuff like this just makes me realize how little I know about something I love so much and spend so much time doing. I really need to be more informed.
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Old 12-09-2007, 07:32 PM
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Default RE: For Roscoe - Tiller

Wow, I just went from knowing absolutely nothing about the subject to feeling as though I know enough that I will be able to check and if needed, fix any problems with my tiller.

Thanks Arthur!
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Old 12-09-2007, 08:41 PM
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Default RE: For Roscoe - Tiller

OK - I went back and re-read your first post. The tiller adjustment is made, as a first step,to stabilize the bow's draw cycle and get the nock tracking pretty level. After that, you just leave it alone and move on to doing further tuning adjustments on the arrow rest and/or nocking point? Or are there some tuning issues later in the process that can be addressed with the tiller adjustments as well? Thanks.
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Old 12-10-2007, 07:48 AM
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Default RE: For Roscoe - Tiller

Sure. You canmove your nock point slightlyby cranking around with the tiller. Like if the tune job hasbeen fighting with you all day,you've got a rope loop tied onand it's just maybe 1/32" from being perfect and you simply don't want to mess with moving the loop AGAIN, give the tiller a little twiddle. I know some guys who do it. I don't recommend it though.
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Old 12-10-2007, 11:11 AM
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Default RE: For Roscoe - Tiller

It is sure great having folks like you on this board who, not only know this stuff, but are willing to share as well.
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