Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on October 05, 2016, 03:30:59 pm
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I'm working on a Yew R/D. When I put it on the tree I have to put it an inch off center to get it to sit level. I'm not"too" concerned but it got me wondering if this will affect limb timing etc. I've double checked all the measurements and if anything the heavy end is the smallest. Is this physical imbalance going to affect the "dynamic balance"?
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I am sure some others will chime in here, but I think the actual timing of the limbs is more important than the actual balance point of the entire bow - but that said - the balance point at the mid handle makes it easy to carry the bow (not tippy in the hand) and - although maybe not a direct correlation, but I think the physical balance point is a good indicator of the amount of mass on either side of the balance point (of course - definition of balance) and thus a good indicator of the limb timing you may expect to see. On my tiller tree, the block that the bow rests on, is radiused - so - only bows that are "balanced" will sit level on the tree when pulled - - this aids in my tillering - as I am shooting for a bow that pulls even and sits level when pulled on my tree.
Not sure I explained that well. I hope you get my gist.
Russ
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Interesting question. I think it has more to do with internal composition of the wood (coarser grain, knots), rather than actual dimensions. I have found also that almost perfectly symmetrical limbs don't necessary make bow be in balance on their supposed center mark.
My new hazel warbow is one of the examples. But I don't worry about it, its not even on tiller tree yet.
I made my new super reinforced tiller with double pulley system so that I pull the string 1" to the right of the center of the bow. Surprisingly that barely made hazel bow I made yesterday rocking on the tiller. That is also first bow on my new setup so I don't know how other hazel or future bows will behave.
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Wet wood is heavier. Is it possible one end is drier than the other? Not sure how this could even happen but theoretically I suppose depending on how it was stored when drying it could
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I don't think it is possible to make two limbs not return at the same time. They are connected so always have exact same tension on them even if the tiller is way off. One limb may keep moving longer or go further past brace once it releases the arrow if the limbs are off.
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Badger, I disagree. Limbs of different strengths have the same tension on their tips at brace because they directly oppose one another in a straight line, but once we grab the handle and string, draw it, and load the limbs by hand from a third direction, the tensions measured between the string hand fulcrum and limbs tips differ relative to the degree of dynamic imbalance.
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Sorry guys, I didn't mean to start the "balance thing" again but it was an honest question ??? ???
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You could always add weights if you think things can be fine-tuned that way.
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Badger, I disagree. Limbs of different strengths have the same tension on their tips at brace because they directly oppose one another in a straight line, but once we grab the handle and string, draw it, and load the limbs by hand from a third direction, the tensions measured between the string hand fulcrum and limbs tips differ relative to the degree of dynamic imbalance.
I agree, but most of us tend to let go of the string when we shoot the arrow.
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If one limb is thicker than the other it will have a faster return time to brace. I know what you are saying Badger but just because the tips are essentially tied together they have to move together to some degree doesn't mean that they are moving in union. If one was thicker it would be 'pulling along' the thinner limb to a degree.
Think about tuning forks, why do they make different sounds? Different thicknesses produce the different notes/vibrations. Thicker vibrates faster. Same with bow limbs.
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"I agree but most of us tend to let go of the string when we shoot an arrow."
Of course. And loaded springs of different strengths tend to travel different distances in different amounts of time.
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I am in Steve's camp on this one. ;) :)
Pappy
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When I start my initial tillering I always sit the bow on center and pull from center until the limbs are dead even (and heavy) and the bow sits perfectly still when drawn 12-15". Once I get it balanced I shift the bow to sit in the same place my hand will, that almost always makes my bottom limb tilt downward, so I start on that limb and balance it out again. I start out on center because its easier for the initial tiller. If it doesn't balance on your tree it cant balance in hand without you shifting your hand, and that's no good. It makes for a loud, inaccurate bow that thumps your hand.
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Physical imbalance is not a problem.
Please see these two videos:
youtube.com/watch?v=oAXSMKogHgI
youtube.com/watch?v=8pYVmrWzTP8
As long as the nocking point is right, the bow is behaving well. The heavier limb tips are, the more handshock, as is well known. "Timing" is not a problem because there is no such a think like "limb timing" you could affect.
Please, test it - take any bow and grip it middle of the upper or lower limb, put a nocking point at right place (+10 mm of square, as usually) and shoot it. What happens? The bow and arrow are behaving well, the bow is fully shootable.
See this video (starting from 0:50 s.:
youtube.com/watch?v=ir5GKAQG14g
It is interesting to see yumi bow in slow motion, although you can not see the full bow. But you can see the same thing than you see from my videos. Although limbs are moving different distance and different speed, they are in unison - they stops at the same time.
One more thing - how would a bow shoot, which had one normal limb and one fully stiff limb, so one limbed bow? Please try, it is easy to test. How it differs from normal bow? What is efficiency of this kind of bow? If there is some differencies, is the reason limb mass or "limb timing"?
Tiller tree geometry is totally different thing. You have two contact points - hand pressure point at the handle and drawing point at the string. Using these, you will get what you see. But, the problem is that using symmetrical tillering tree geometry and these two points, the bow are tilting at the tillering tree, so you have to "read" the bending of the bow correctly.
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I'm in Steve's camp as well. The only possible way the limbs can be "out of time" is if their outer limb mass is grossly different and you would have to be a pretty poor bowyer for that. Small changes in this mass-difference will not affect the way they return substantially, they will contribute to that hand-shock though
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Tuomo, there IS such a thing as limb timing. You more or less said so yourself... "As long as the nocking point is right, the bow is behaving well." Yes, because moving the nock point moves the string hand fulcrum which affects... yep, relative limb balance and limb timing. That's why folks who switch to 3 under have to move the nock point up, to re-strengthen the bottom limb, to regain shooting qualities.
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When I start my initial tillering I always sit the bow on center and pull from center until the limbs are dead even (and heavy) and the bow sits perfectly still when drawn 12-15". Once I get it balanced I shift the bow to sit in the same place my hand will, that almost always makes my bottom limb tilt downward, so I start on that limb and balance it out again. I start out on center because its easier for the initial tiller. If it doesn't balance on your tree it cant balance in hand without you shifting your hand, and that's no good. It makes for a loud, inaccurate bow that thumps your hand.
That is almost exactly how I do it.
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When I start my initial tillering I always sit the bow on center and pull from center until the limbs are dead even (and heavy) and the bow sits perfectly still when drawn 12-15". Once I get it balanced I shift the bow to sit in the same place my hand will, that almost always makes my bottom limb tilt downward, so I start on that limb and balance it out again. I start out on center because its easier for the initial tiller. If it doesn't balance on your tree it cant balance in hand without you shifting your hand, and that's no good. It makes for a loud, inaccurate bow that thumps your hand.
That is almost exactly how I do it.
I agree - as it is how I do it as well. Does this not mean, though, that the tiller balance around your hand holding the bow is a prime factor - since if it is not balanced, your hand will have to unnaturally hold the bow "vertical" to keep the shot straight?
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Russ that is exactly what it means.
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My tillering is pretty much the same way as Pearly does his tillering too.I have lines every 2" across the background both ways to make 2" squares to confirm my eye.Did that way long ago when starting to make bows,but really don't need them any more really.A 20" draw check position of tips like said usually is good out to 28" for me.
At that point if there is any difference there is'nt very much draw weight loss to balance them and it's just a matter of where removal is taken then.Usually evenly the whole length because it is evenly bending limbs.Along the way I get an 1/8" positive tiller the whole length of the limb.Shooting it confirms the feel of things in my hand provided the string nocking point is pretty close.
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Russ that is exactly what it means.
PD - I get that - I was really asking if Badger now agrees or is still thinking that the balance issue is a non issue.
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Its a non issue only if your okay with sliding nocks up and down your string and adjusting your hand placement. I mark exactly where my pass will be before the bow ever gets close to bending. I make a 4" grip and my pass is always 2" above center. I don't adjust that and see no reason to adjust it. I adjust the limbs strength rather to match my markings.
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I tiller differently than you guys then. I place the bow on the tree the way I hold it, and pull the string from where I'll draw it from the very first pull. I can tell if the limbs are balanced relative to my holds by pulling the string just an inch or two from brace height on the tree.... actually I know before brace, with the long string. I want to know exactly what it needs as early as possible in the tillering, begin balancing right away, and can't think of a reason to pull it other than how I'll shoot it... but I can think of reasons not to :)
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Jeff that's how I do it at well. I simply start on center until I'm out to say 18-20", its easier for me to see initial bending. Then I slide the grip down to match my hand hold and I always hook on where my middle finger would be.
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Actually good floor tillering a bow very close to your draw weight reduces set in my book.Coming from floor tillering to even brace within 5 to 10 pounds your initial draw weight at your draw length is an art and if heat treating is involved so the better retaining your treatment.Going on a different subject here I know though.Anyway I tell ya if it stands the test of time and holds profile/hits where you want/and has very little hand shock that's all that's required.
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OK if I want to get this bow to physically balance on it's geographic center I'm going to have to remove quite a bit of wood. I've now quadruple checked my measurements and the heavy limb is smaller so there is denser wood in there or something. However the tiller looks OK(ish). I'm thinking the best place to remove wood will be the tips(more bang for my buck and less effect on the tiller). Does that sound like the smart thing to do?
As added info this is more of a deflex/ recurve then an RD. It is an almost flawless piece of Yew. I had left the tips 3/4" wide and tillered it to almost complete. I took it out to shoot it and it was horrible. With my usual aiming point the arrows hit 18" low at 20yds. Broke one tip on the concrete block that the target sits on. Also up until now I was unsure what handshock felt like. Now I know!! Since then I have reduced the tips to 1/2" and reduced the deflex by two inches while heat treating the he!! out of it. It's resting now.
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I believe you are on the right track there bud.
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Also up until now I was unsure what handshock felt like.
I have broke about 7 bows and have 7 survivors. The only time I felt hand shock was on my Ski Bow. Hence limbs built from a pair of skis. :)
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Russ that is exactly what it means.
PD - I get that - I was really asking if Badger now agrees or is still thinking that the balance issue is a non issue.
I always check the ballance but only because I get a kick out of seeing how well a finsihed bow ballances. As far as I know I have never had one far enough out to really pay much attention to it. So my answer would be I do usually check the physical ballance but I don't base it on anything or do anything about it. I just make the limbs look the same and ballance out the tiller I am looking for.
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I lay it out asymmetrically so the static balance point/geographic center is about 3/4" above handle center... right on my middle finger. I like how such a bow carries, is quick and natural to point, and how it works with the tillering process. This design puts the static balance point, string fulcrum, and dynamic balance point at full draw all within a fraction of an inch of each other... for me... which causes the bow to behave better during the draw and facilitates tillering for dynamic balance earlier in the draw.
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The first thing I do after floor tillering is place the bow on the tree from the center to make sure the bow balances. I can't long string tiller without doing that.
The subject of limb timing comes up now and then on here.
Wood is not uniform. Even within the same stave it can have different properties. If your stave is a knotted, twisted piece of wood, timing can be an issue especially when you can't achieve that picture perfect tiller.
I want my limbs bending equally well and returning at the same time.
I can see that on my rope and pulley.
Call it what you want.
I call it limb timing. :)
FYI I tiller from center and finish tiller either by feel, mirror or digi pic.
Jawge
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If I have to lose weight on one limb is making that limb narrower an acceptable trade off? By making one narrower I can take more weight off and still have the same tiller(hopefully).
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I think DC is talking about physical weight like on a ballancer. Not so much ballanced tiller, if the ballance point is 1" off center it can't be far off
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Yup