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Main Boards => The Bowyer's Bench => Topic started by: Jaenak on September 08, 2008, 01:13:00 AM
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This is going to sound like a *DUH* kind of question but bear with me because that's not how I mean it.
What causes hand shock? There's the *DUH* part. I know that it's caused by vibrations in the bow that are generated when you release the string. What I want to know is if that's the only contributing factor to hand shock and what can a bowyer do while making the bow to reduce hand shock as much as possible. I guess you could also say, why do some bows have more hand shock than others?
I know that the heavier the arrow the more shock it'll absorb, the lower the brace height, the longer the string will be in contact with the arrow and thus the more shock it'll be able to transfer to the arrow, and I know that some types of wood absorb more shock than others although I really don't understand that last one. I also suppose that the more wood there is in the bow itself, the more shock it'll be able to absorb. Any thoughts, comments, ideas, etc?
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Hand shock is caused by improper limb timing, and excessive weight at the tips. Design also plays a part.
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Hand shock is excess energy that is not absorbed by the arrow. Like Apex said it can be because of improper limb timing or excess weight in the outer limb tips or just poor bow design or even a heavy string. Depending on the bow and its design, most hand shock can be eliminated or reduced to an almost unnoticeable level. Having a heavy riser can "absorb" the extra vibrations that cause hand shock.
Are you talking about a glass bow or a wood bow? I build wood bow so I can maybe help reduce hand shock with a self bow or wood bow. Others can give you better advise for glass bows. Pat
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My Martin #10 Pioneer longbow is a reflex only designed bow (the limb are straight but are angled out past the back of the bow a bit). If gripped too tight it jots my bow forearm and hand so that my watch can cause a sore on my wrist in just a shooting session. I've learnt how to hold it better now but still there is handshock.
I've had the opportunity, once, to try out a R/D fiberglass bow and was stunned by the amount of handshock: NONE. I've lately put together a few BBO trilams of the R/D persuassion and am impressed with their softness in the hand. Same is said of my Dad's 1960 vintage Herter's recurve: Smooth as silk and no shock.
As said above design coupled with other elements makes or deletes handshock.
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*wips out notepad*
riser too light...string too heavy...bad limb timing...too much weight at the limb tips
So, a heavy(ish) riser, a heavy arrow, low brace height, light and relatively skinny limb tips, a thin string, a thick leather grip, and great limb timing will help to reduce hand shock. Cool. All except that last one, could anyone explain the limb timing to me? Also, how do you change the limb timing when making a bow? I've always had this childish notion that both limbs always magically straighten at the same time with the same speed. And yes you're right, I've obviously never made a bow. I'd like to one of these days though. A wooden one that is, no fiberglass.
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All of the above are good suggestions. Hand shock can be eliminated in most bows just by correcting bad limb timing. I see a lot of bows where the tiller is no where near right but people keep insisting on using the same bad formula to tiller their bows. A whip tillered bow can have hand shock or at least excessive vibration when shot. The heavy strings dont help either....Glenn...
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"I've always had this childish notion that both limbs always magically straighten at the same time with the same speed."
If one limb is too stiff and the other is too weak they won't time up right. When tillering a bow you look for the limb tips, at least I do, to be pulled the same distance. I mark horizonal lines on the wall behind the tiller tree. Then I stand back and pull the cord attached to the bow string to see if the limbs are arching correctly and if the tips are both touching the same line on the wall. If one is an inch off then you will know that those tips aren't timed up. Admittedly, I am still a neophite at wood bow building but this is what I've learned from my studies on the subject. Seems to work for me when I get it right, too.
Hope it helps.
By the way, light risers don't have to have handshock if the bow is tillered and designed well. I've shot bows that don't have massive risers that are extremely smooth. The R/D fiberglass I mentioned above is like that. Striker Bows, also, are very smooth, yet, with a petite riser.
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Christopher is correct except for one thing; the limbs have to bend evenly and together. Just because the tips pull the same distance doesn't mean the limbs bend evenly. You could have a hinge or stiff spots that would prevent an even bend in the limbs even though the tips line up.
A heavy riser doesn't make it a given either. On my self bows I use a bulbous handle and the limbs usually bend right up to the handle. My handles are very light and my bows have little hand shock. In many cases with self and wood bows tip weight is the culprit. Pat
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Cool. So if both limbs bend the same distances in all the same spots all the way up and down the limbs, then they'll be timed correctly? Sounds like it'd be a good idea to draw a one inch square grid on the wall behind the tiller tree so you can measure every spot all the way up and down both limbs.
Thanks everybody!
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If you make a symmetrical bow both limbs will bend the same and together but if you build an asymmetrical bow both limbs will bend together but not the same. One limb(usually the bottom) is shorter so its bend will look different than the longer one. This is one reason I prefer a symmetrical design...for ease of tillering for me.
Don't let all of this confuse you. Just do it. Lots of what we are talking about will become second nature to you and you will hardly have to think about it. You just have to develop an eye and a feel for it. Pat
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If you make a symmetrical bow and shoot the arrow 1.25 inches above centre on the riser and the riser is equal length either side of centre the string to the top limb will be 2.5 inches shorter to the top limb than to the bottom limb from where the aarrow is nocked. You will be placing more pressure on the top limb which will make it bend different to the bottom limb. If you make the top limb weaker than the bottom limb you will make it bend a lot more than the bottom limb, the bow limbs will be automatically way out of time with each other and have a lot of hand shock...Glenn...
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If you make a symmetrical bow and shoot the arrow 1.25 inches above centre on the riser and the riser is equal length either side of centre the string to the top limb will be 2.5 inches shorter to the top limb than to the bottom limb from where the aarrow is nocked. You will be placing more pressure on the top limb which will make it bend different to the bottom limb. If you make the top limb weaker than the bottom limb you will make it bend a lot more than the bottom limb, the bow limbs will be automatically way out of time with each other and have a lot of hand shock...Glenn...
Using what type of grip Glenn? Yes, if you use a straight wrist/low contact type grip then you will apply greater pressure to the top limb. Apply a full hand/low wrist contact and you'll put greater pressure on the lower limb. Apply proper grip to the 1.25 inches above center and both limbs feel even strain. Folks kind of forget or simply don't know that you've got to grip a bow according to its design.-ART B
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...just because it's simple doesn't mean it is easy!
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Hey Pat,
I believe I was correct in everything I said. I just shortened what you said,
"the limbs have to bend evenly and together. Just because the tips pull the same distance doesn't mean the limbs bend evenly. You could have a hinge or stiff spots that would prevent an even bend in the limbs even though the tips line up."
down to,
"Then I stand back and pull the cord attached to the bow string to see if the limbs are arching correctly".
You just added the right amount of words to make sense!
Jaenak, Pat is right, you will have to dive in and do it to see what we mean. I am still learning by doing and reading these men who have the knowledge.
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when we quit learning we had better just give it all up! Pat
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That's a great point, Art B, my friend (good to "see/hear" you), and one I would dearly love to see some difinitive pictures or diagrams of someday. I tend to think that I use pretty much the same grip all the time but I know that's probably not compleatly so. I probably, in fact, adjust my grip to the bow I am shooting (within my parameters) to were it is the most comfortable with that particular bow, and it shoots the best for me - subconciously (or maybe unconsciously is more like it - LOL). In truth, I'd have to admit that probably someone like you, or other friends who have watched me, or seen pics of me, know more about the type of grip(s) I use than I do.
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Art B that is true what you say, I made a real nice short selfbow years ago and I let someone shoot it but he shot the bow with his thumb pointing up towards the top limb and pulled the bottom limb way out of shape, it needed to be a lot stiffer for his hand grip and style.
I still had in my mind what had been said on other post here about tiller. I know that there is no one formula to cover tiller on all bows as bows come with equal length and unequal length limbs and tiller always has to be adjusted to suit hand placement on the bow and string and as you have correctly pointed out high and low wrist grips. Selfbows are a dead give away and quickly show up any tillering mistakes...Glenn...
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Hi Bernie, always a pleasure to look/listen in on your conversations (mostly a lurker these days you know)! From looking at your pose over on your Holmi thread it looks like you and I have pretty much the same grip (low to medium). For myself (and most of my friends) I go 1 1/2" above center for this type of grip. That's about average for most folks from what I've gathered over the years. For the real punishers like my son I will raise that to 1 3/4" to 2". He's got a big ol' hand and uses it all on the handle. Even for myself I'll raise my arrow pass to 1 3/4" to compensate for higher weight bows (I tend to need more hand to handle the extra weight).
But it all comes down to making a few bows and then deciding what works best for yourself. Nothing really set in stone here.
Glenn, I'm still crying over that very nice bent eared hickory static I gave my son last year. ART B
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Art, I have a couple of selfbows now that I never string up if someone wants to handle one, some people just don't know how to handle selfbows properly. Hand placement on the bow makes a huge differance to how the limbs will bend when being drawn...Glenn...
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Thanks, Art, glad you looked in there - I just wish I knew one tenth of what you know about wood bows (and arrows) - and, while I'm at it, then I wish I could retain just one tenth of that - :D . I sure do have fun though ("with a lot of help from my friends" :) ).
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Oh boy, that complicates things. I forgot about the grip style effecting the limb strength. So, would it help solve things if a person made the handle portion, figured out where the nock would be on the string in corilation to the grip and pull style (split finger or three under), then attached the string from the tiller tree to the nock point and adjusted the tiller according to what the tiller tree showed from the adjusted placement of the tiller pull string? Then the tiller tree would be pulling the bow string right where your fingers would be pulling the bow string later and you'd be able to get an accurate measurement from the tiller tree then. Would that work or am I just lost on this?
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A tiller tree is too static to get a "true" feel for the tiller. That will come with experience. The way your hand(or any other shooter)cradles the bows handle isn't any thing like a tiller tree's bow rest. Dean Torges tried to improve on this with a radiused bow rest. I find this hard to deal with in real life so I have learned to adjust. By looking at yourself pulling the bow to full draw in a large mirror or having someone take a pic of you at full draw will give you a better view of tiller...but a posed pic is different from a shot taken at a deer or even a target. Pat
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I did that on my Holmi, at the suggestion of Glenn and Dano, cause it made sense to me to at least try - it's do-able and makes some difference (of course). You can see it, and read about it, near the last steps of my thread/build. Whether or not it makes enough difference to play with is gonna be for each person to decide for themselves, I would think. For those with the experience and instincts of folks like, friend Pat, they develope other ways to reach the same point or results, such as he mentioned. So, "many ways to skin a cat" comes to mind, and I, for one, as a rank amateur, love hearing, considering, discussing and trying them, or not - don't you? :archer:
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I use a single point of contact, versus a cradle, to suspend the bow handle. Mine is a lag bolt wrapped in leather so I have a surface of about 1/2" to rest upon. I find I can balance the bow at about 1" above center or thereabout and adjust the position of my draw hook to fine tune the balance. My draw hook winds up somewhere below the final nock point, between an inch to zero I'd estimate.
The primary method for determining how well the bow is balanced, in terms of the balance of stress between the upper and lower limb, and even the bend within a particular limb, is the set taken from shooting by hand. The earlier you start shooting the bow by hand, versus working it on the tree, the better matched your finished bow will be to your shooting style. I generally start shooting at least 4" before final draw lenght. And I try not to work the bow much on the tillering tree, or shooting for that matter, until I'm satisfied the load is well balanced and each entire limb takes an equal amount of set from work. I also prefer lots of shorter workouts, with enough rest too fully recover the set, so that I don't permanently set the bow with some inherent flaw early in the tillering process.
All this being said, I'm not sure how it relates to hand shock to be honest. I'd rank outer limb mass and low stretch string above tiller "timing" (more or less positive tiller) for it's relative influence on hand shock.
Perfect tiller, in as much as it can be achieved, has other, more compelling justifications anyway, predominantly premature work fatigue and the overall design requirements. More specifically, a really short bow should bend generally more on the inner limb, and longer visa-versa, imho. I find full arc of circle tiller not necessarily as desirable in as many cases as not. In fact one could make a compelling argument full arc of circle might be more likely to contribute to hand shock than other forms, based upon the idea (demonstrated in high speed film) that it's the mid limb area which tends to distort or "bulge" the most at the end of the power stroke. Full arc of circle would tend to exaggerate this, I would think, by virtue of the mid limb being necessarily weaker relative to the other two forms.
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I appreciate the offer Glenn, but like yourself, I have many bows that are being neglected also. I've given many bows away over the years so I'm very aware of the treatment they receive. Hard to make a selfbow bomb-proof but I do my best.
About one tenth of what I use to know is about all I have left Bernie (no kidding).
I try to keep my bow building as simple and as quick as possible. I use a tapering method to get the limbs bending and pretty much all I have to do is scrape the entire limb from tip to fade (no tillering gizmo used for selfbows) to reduce weight. By keeping the bow's static balance in line with it's dimensional center at the floor tillering stage I know I'll be very close to having an even tiller at brace height on the tillering board. Once the bow shows even tiller on the tillering tree I go straight to full brace height using the short string. From there I draw the bow by hand keeping an even tiller to just under desired weight. Then I'll set the appropriate tiller for the bow. -ART B
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Art, how do you determine the appropriate tiller for the bow, I'm assuming you mean the degree of positive?
Reason I ask is I'm not real sure how I do it myself, other than trial and error by shooting manners and watching for set on one limb versus the other, giving much more priority to the latter. I'm afraid I've become so used to doing the same thing over and over, I'm not real sure what or why I do what I do. I think the set issue is the primary driver, and the shooting manners naturally follows. I know most of my bows wind up with about 1/8" of positive, even when the offset of the arrow pass to dimensional center can change by as much as 1" from one bow to the next. Kinda makes me wonder whether or how the handle config effects the amount of positive "required." I've always assumed, based upon what I've read about bow mechanics, that more offset of arrow pass from dimensional center would require necessitate more positive tiller for good shooting manners. Curious about your experiences with that.
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Setting the appropicate tiller for me is a combination of drawing the bow my hand (keeping an even tiller while having even strain on both limbs by using proper hand placement) and shooting the bow. Once I feel even strain on both limbs I then apply a little heel pressure to the bow's handle to make sure I feel the lower limb stiffen ever so slightly. This will on average show a bow with around 1/8" positive tiller as you mentioned.
The shooting part is important as well. If your bow shoots where you're looking then you're ready to shoot the bow in. But if the bow consistantly shoots low then the lower limb needs strengthening (or weaking the upper). This is what works best for me for the handle (straight) style I prefer and type shooting I do.
Due to the greater angle between the bow hand and drawing hand created by the higher arrow pass this will cause more "heeling" of the handle David. So yes, on most bows I will beef up the lower limb creating more positive tiller. Heck, I do this deliberately when I'm making a give-away no matter the arrow pass placement. But in spite of instructions most folks will heel these bows to death destorying the bow's profile. Better that they feel a little kick in the bow then having a bow that will be useless sooner than later.
But there's much more to tiller than that with the higher arrow pass. Higher arrow passes creates an asymeticial string which can be compared to a short and long tillering string. Upper limb's string angle (long tillering string) strains enter limb. Lower limb's string angle (short string) strains mid to outer limb. A little balance is needed here to equal the strain to both limbs. Your thougths on that David. ART B
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Nothing is going to simulate the actual shooting of the bow. I go out and draw the bow trying to sense the handle pressure. Is it even or is the bow tipping in my hand. When I shoot I forget about hitting the bull. Instead I try to feel the limbs as they slam home. Do they do so at the same time or are they out of sync? Is the arrow release silent? This is all part of the tillering process and through all of this I never once used my eyes. The bowyer that uses only his eyes to tiller is 1/5 the bowyer he could be. Use as many of your senses as you can. :) Jawge
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Yeah, you're right George. Positive/negitive tiller is more a feel for balance which can't be achieved on a tillering tree. My tillering tree is only used to exercize bows over my draw length. My eyes are going bad George so now I'm down to one tenth of 4/5 of a bowyer. Talking about having to work by feel.......................:)ART B
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Sorry to hear that, Art. I'd happily be 1/5 the bowyer you are. Jawge
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You've got that right, Jawge, and that's far more of a statement, coming from a bowyer like you. How I wish I had started building bows when I was waaaaaaaaaaaaaaay younger - but I'm sure glad my friend, Mike, wouldn't stand for me waiting any longer, or my saying that there wasn't time enough left anymore, so at least I've got the thrill of doing a few - :archer:
Tomorrow AM I go Deer hunting with my own Osage self bow, "It", - never woulda thunk it - :jumper:
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You are too kind George! What little I know won't fill even one of your boots. :) ART B
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Art,
"Higher arrow passes creates an asymeticial string which can be compared to a short and long tillering string. Upper limb's string angle (long tillering string) strains enter limb. Lower limb's string angle (short string) strains mid to outer limb."
My thinking is like yours. I love your analogy, which describes perfectly the asymetry inherent in the so called symetrical, or 2" above center handle config. It's asif the lower limb is that of a longer bow, attached to an upper limb as if from a shorter bow. By making the lower stiffer, we make it "seem" shorter to the upper, essentially inducing "stack" but as true draw weight from the outset in order to balance out the stack, in the classic sense of the word, the upper limb sees by virtue of it's wider string angle.
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At the end of the day the proof is in the shooting. You can make up a fiberglass bow and before the shelf and window are cut in mark 1.25" above centre where the arrow will pass and shoot the bow in the positive tillered position and then turn it up the other way and shoot it in the negative or reverse tillered position and see what you think.
With a selfbow that has been made with even length limbs and it is shot 1.25" above centre and has been positive tillered will take more set to the top limb because it has more pressure placed on it by the shorter string length...Glenn...
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I know what you're saying Glenn. And I'm sure if your tillering method works fine for you then that'd OK by me. Got no ax to grind about the tillering method you use. Best I can do is explain why my method works for me and you can draw your own conclusions.
First and foremost I want even strain (both limbs sharing equal work) on both limbs. When this occurs both limbs will take equal set. I'm sure you will agree with that. If I get more set in the upper limb vs the lower then I realize I'm over stressing that limb (doing more then it's share of work). Here is where logic would say to beef up the upper limb to help to compensate for the over stressing (adding even more work-load to the upper limb and taking away from the lower limb)thus producing a stiffer upper limb or negitive tiller. Problem with that line thinking is that I now have one limb doing more work then the other. So that doesn't solve the problem of having equal strain on bow limbs. So to solve the problem I have to take some workload from the top and add to the bottom limb to even the strain back out. Now I have both limbs carring the same work-load and taking even set. And because of the the extra stress added to the lower limb by the forces created by the bow and drawing hand it will need to be slightly stronger to help maintain it's profile over time. I just added that last sentance to demostrate the need for positive tiller. In reality you shouldn't notice the stronger lower limb or uneven set if proper grip is used.-ART B
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Art I don't any have any axe to grind either or how somebody wants to tiller their selfbow. I use to make my selfbow with equal length limbs and index finger of bow hand 1.25" above centre and tiller the bow with positive tiller. But I have always found that the top limb takes more set than the bottom. I have just found that since I started shooting equal length limb bows with negative tiller or reverse tiller the bows will take equal set and the bows are much smoother to shoot. Even the fibreglass bows made the same way are much more pleasent to shoot with reverse tiller. If you change your hand placement on the bow up or down tiller has to be adjusted to accomadate the different strains placed on the limbs. The closer to the centre the arrow passes the less strain on the top limb and more strain placed on the bottom. Low and high wrist grips will do that also as well as split fingers and three under. There is not only tiller to consider but how does the bow balance in the hand when it is being drawn...Glenn...
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I think that's what most folks fail to understand Glenn. Just because something works for one doesn't necessarily mean it's suitable for all. We all got our own needs and requirments. Heck, most of us are just doing this to suit ourselves anyway. Have fun! -ART B
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No worries Art, it's been a good discussion anyway, back down to the shed now...Glenn...
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I enjoyed the discussion as well fellas. Thanks for posting. The part that really soaked in for me was the passage which follows from Art. I think it's the part I tend to focus upon, indirectly and oddly without realizing it, which means I misscommunicate with others who probably don't give it as much consideration. I tend to take the balanced load aspects for granted I guess.
"The shooting part is important as well. If your bow shoots where you're looking then you're ready to shoot the bow in. But if the bow consistantly shoots low then the lower limb needs strengthening (or weaking the upper). This is what works best for me for the handle (straight) style I prefer and type shooting I do."
Obviously, whether a bow shoots high or low relative to "where you are looking" is so highly subjective, and so much a function of our individual form, it's not like we'll all be the same in that respect. But this is the focus of most of the discussion of tiller and it's underlying purpose, and mathematical modelling with the incentive of having the arrow come off the bow as straight as possible (in the verticle plane). But no matter how we tiller and shoot, we can usually find a nock point height which works for that unique combination.
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PAT'S right all the way around
Heres a couple things not said,
Poor tillering one limb pulling more than the other.Which is what happens if you make your limbs the same.You have make your bottom limb the right leanth acording to your shelf placement.
Your limbs are to thin not enough mass in your bow.This why heavey woods have less hand shock than white woods.
Tips need to be stiff at lease 4"s down from the nock.Just heavey enough to keep them stiff.
A to straight a grip.
Like PAT said to big a string.
High brace height.
To light an arrow.
Twisted limbs.
I think you all have covered it all.
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PAT'S right all the way around
Heres a couple things not said,
Poor tillering one limb pulling more than the other.Which is what happens if you make your limbs the same.You have make your bottom limb the right leanth acording to your shelf placement.
Your limbs are to thin not enough mass in your bow.This why heavey woods have less hand shock than white woods.
Tips need to be stiff at lease 4"s down from the nock.Just heavey enough to keep them stiff.
A to straight a grip.
Like PAT said to big a string.
High brace height.
To light an arrow.
Twisted limbs.
I think you all have covered it all.
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Good Stuff--Question for you guys and do not mean to hi jack this thread, but this question fits. When tillering should your tillering string be located below the nock point (for example 1.25 inches above bow center if that is where you rest is going to be? Most of the guys I work with put the hook in the center of the bow. Always wondered about this as changing the point of pull on the string affects how the limbs bend when tillering. Thanks, Coach
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Personally, I think you can mimic perfectly the pressures (even strained limbs) applied by "pulling the bow from dead center" with the hook by the dymamic action of the bow/drawing hand. However, I don't believe you can mimic ones draw on the tillering tree by off setting the hook from center (creates uneven limb strain). Just my personal opinion guys.
ART B
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Art, I've been following your remarks on here and on other sites regarding and handle grip styles and rest locations. You have given me something to think about. But i just am too tired right now to wrap my feeble mind around it. But I have think about it. Jawge
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Again Pat cover it all.In wood bows I've found out one limb pulling more than the other.Is one of the main reasons for it.Most bows start out tillered correct'ly but lose there tiller later for one reason or another.This is one of the main reasons wood bows get hand shock.Second reason is the tips are made to heavy.But again PAT's already went through all of that.
I keep learning and relearning all the time.