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Author Topic: Limb timing
arachnid
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Hi guys.

In an attempt to learn and perfect my bow building skills, I`ve been studying (or at lest trying to) my latest bow. I watched the shooting video and took a snap shot out of it.
This in the moment of release:
 -

Look at the limbs. The lower limb returned almost completely to it`s braced position while the upper is still bent.

A) Is this normal of do I need to have both limbs returning at the same time?

B) What can cause this and how can I avoid it on my next bow?

C) Is it fixable (on this bow)?

Thanks in advance

Dor

Posts: 210 | From: Israel | Registered: Jul 2016  |  IP: Logged | Report this post to a Moderator
Buemaker
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I "map" my limbs. Lay the braced bow on a long piece of paper, mark where the center is. Draw a line along the bow's back or belly, then flip the bow. If you now draw a line it should be the same as the first one. Repeat with the bow at say 20" draw and If you like at full draw, use a stick to hold the bow in drawn position. I do not bother with the positive tiller thing, I want the limbs to bend the same, works for me at least.
If the bow don't kick like a mule, you must have done something right.

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Crooked Stic
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Did you adjust the fade tiller. Let us see a pic of that bow at brace and unstrung and full draw. are both limbs the same length?

--------------------
High on Archery.

Posts: 3125 | From: Princeton IN. | Registered: Dec 2003  |  IP: Logged | Report this post to a Moderator
arachnid
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quote:
Originally posted by Crooked Stic:
Did you adjust the fade tiller.

I guess you mean the distance from the fade to the string?
If so then the answer is yes, it is the same distance.

I'll post pictures later.

Posts: 210 | From: Israel | Registered: Jul 2016  |  IP: Logged | Report this post to a Moderator
Shredd
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I think that I read somewhere that you cannot go by certain electronic pictures... The pic could be off... Hopefully someone can add info to this... I don't know for sure myself...
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mikkekeswick
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That picture is nuts! Something weird is happening! If a bow acted like that then the limb strengths would have to be way,way off! Like brace would have one limb bent and the other straight! Handshock would be immense too!
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pditto613
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quote:
Originally posted by mikkekeswick:
That picture is nuts! Something weird is happening! If a bow acted like that then the limb strengths would have to be way,way off! Like brace would have one limb bent and the other straight! Handshock would be immense too!

Have to agree. No way the arrow would be flat coming off a bow bending like that. How does it shoot? Hand Shock? Does the arrow porpoise real bad?
Posts: 155 | From: palatka, fl | Registered: Mar 2009  |  IP: Logged | Report this post to a Moderator
arachnid
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quote:
Originally posted by pditto613:
quote:
Originally posted by mikkekeswick:
That picture is nuts! Something weird is happening! If a bow acted like that then the limb strengths would have to be way,way off! Like brace would have one limb bent and the other straight! Handshock would be immense too!

Have to agree. No way the arrow would be flat coming off a bow bending like that. How does it shoot? Hand Shock? Does the arrow porpoise real bad?
The bow shoots great. Fast, pretty dead in the hand. Tiller looks good... I post braced an FD pics later
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alaninoz
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I think Shredd has got it. Have a look at:

https://en.wikipedia.org/wiki/Rolling_shutter

--------------------
Alan

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Bowjunkie
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Yeah, you need a camera shooting high speed film. I've seen other guys try to do what you're doing and the pics were even more unbelievable than yours.
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Bowjunkie
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Good link and explanation, Alan.
Posts: 2356 | From: Pa | Registered: Apr 2003  |  IP: Logged | Report this post to a Moderator
arachnid
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I've read the info in Alan's link. Phew..... Well that a relief.... I thought something went WAY wrong with this one...

So how DO you adjust limb timing? Do you even consider this as a factor or do you just set the tiller right?

Posts: 210 | From: Israel | Registered: Jul 2016  |  IP: Logged | Report this post to a Moderator
Dazzad
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That image is outrageous!!! I'd not heard of the photographic phenomenon that can create this kind of thing.
If the limbs really were so different to each other you would surely have felt and seen a really undesirable result on the shot - If the bow feels great to shoot, that camera is telling lies. I'm off to read the wiki link on this right now....

--------------------
Each day the devil whispered in my ear -"you will not withstand the storm."
Today I whispered in the devil's ear - " I am the storm..."

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Crooked Stic
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I went back and looked at your video of the test shots and man that thing looks good there. I say if it has good tiller and aint rattling your teth on release you are fine.

--------------------
High on Archery.

Posts: 3125 | From: Princeton IN. | Registered: Dec 2003  |  IP: Logged | Report this post to a Moderator
Bowjunkie
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In a nutshell, here's one way to achieve limb balance/timing without guessing. Support the handle in the tillering tree(rope and pulley system) so that it's perfectly level, and don't worry about one limb tip being ahead of the other(like when one has more reflex).

Pull the string from where the fulcrum of pressure will be while shooting, and watch the hook/fulcrum on the string as it comes down.

On the wall under the tillering tree's handle cradle, draw a vertical plumb line in the exact spot that mimics the hook coming straight down, or in other words... the string hand fulcrum coming straight back(for me, this is where the center of my middle finger resides on the string, assuming a 3/8" high nock point and 1/4" thick arrow nock, which is then exactly where I put it when the bow is done).

The hook will only follow that line during the draw if the limbs are balanced relative to your holds. If one limb is too strong, it will flex less, travel less distance, and the hook will drift towards it during the draw. You then weaken that limb until the hook/fulcrum follows the line. When it follows the line to your draw length, and the limbs are bending the way you want, you're done.

There are more involved ways to fine tune it, but these basics will get you close enough for our intents.

Done this way, when drawn by hand, both limb tips travel the same distance, bringing the arrow's nock end straight back relative to the handle/shelf, and it leaves straight away, inherently tuned without porpoising, and so without a need to move the nock point up and down trying to 'fix' it.

Posts: 2356 | From: Pa | Registered: Apr 2003  |  IP: Logged | Report this post to a Moderator
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