Is Limb Timing an Issue?

[Del the cat]

People were talking about limb timing on a recent thread.
I find it hard to see how the limbs can return at different times, after all the limb tips are connected by the string!
They are balanced at brace, and (unless the grip is somehow clamped in an unbalanced position) the force is in balance at every point from brace to full draw, and thus presumably during the return as the arrow is loosed.
The only imbalance I can see is if someone is string walking (a hideous practice for a wooden bow)

They are not "individual" limbs, the whole bow is effectively one continuous spring. Even a very asymmetric bow like a Yumi remains in balance throughout the draw.
Is there any video evidence of limbs returning out of synch'? I can see it happening with a compound (spits on floor) if the cams don't match.
Anyone got any explanation, comments thoughts?
I'm happy to be shown to be wrong and have my understanding (or lack of it) enhanced.
Del (confused of Harlow)

[Eric Krewson]

Timing might not be the right word, perhaps balance would work better. I have had shocky bows with one limb that felt slightly stronger at full draw than the other, I would give the suspected limb a full-length belly sanding a little at a time to see if the shock got better, it usually did and smoothed out. This is a shoot and feel kind of thing. I have sanded the suspect limb and the shock got worse, I realized I was working on the wrong limb.

After shooting bows for 65 years this "feel" isn't something I can describe, I just sense it.

[Mo_coon-catcher]

I’ve always thought the same Del. I feel it has more to do with the location of the vibrations in the bow. Watching low motion videos of the bows shot, they all vibrate. So really you want the oacillation waves to hit their valleys or atleast crossover at the neutral plane, at the handle so that spot doesn’t move. If the peaked both hit you hand at the same time you’ll get lots of movement. I think that different shaped tiles induce a different vibration wave and the goal is to get matching waves so they consistently oscillate in the same way. And the limb tuning/timing is shifting these waves independently until the oscillation reaches a point that either tolerable or goes away at the handle.

I hope this rambling gets my thoughts across

Kyle

[Marc St Louis]

People were talking about limb timing on a recent thread.
I find it hard to see how the limbs can return at different times, after all the limb tips are connected by the string!
They are balanced at brace, and (unless the grip is somehow clamped in an unbalanced position) the force is in balance at every point from brace to full draw, and thus presumably during the return as the arrow is loosed.
The only imbalance I can see is if someone is string walking (a hideous practice for a wooden bow)

They are not "individual" limbs, the whole bow is effectively one continuous spring. Even a very asymmetric bow like a Yumi remains in balance throughout the draw.
Is there any video evidence of limbs returning out of synch'? I can see it happening with a compound (spits on floor) if the cams don't match.
Anyone got any explanation, comments thoughts?
I'm happy to be shown to be wrong and have my understanding (or lack of it) enhanced.
Del (confused of Harlow)

There's been talk of limb timing over the years.  To me the only way you could have a timing issue is if there is an imbalance in the limbs, specifically the mass.  You'd have to be a pretty crappy bowyer to have that much mass imbalance to create an issue

[Pappy]

Yep very much agree with above. I hear it but usually don’t comment because didn’t really know I to explain why I thought it but Del done a fine job.👍 Pappy

[Selfbowman]

I agree with Marc. Overbuilt bows. Extra weight on the tips is one example. Vibration from unbalanced limbs.

[willie]

They are not "individual" limbs, the whole bow is effectively one continuous spring.

yes but one end may not react to the loose as fast as the other, or put another way
one end can have more hystersis than the other

 the string comes tight at the end of the release stroke, the timing is the same because there is only one string to define the moment, the tips are suddenly stopped at the same time but the midlimbs (with more mass) are following through and will still move foreward depending on the momentum of that particular end of the bow, and the unevenness or difference of momentum is felt as shock

[sleek]

I'm 100% convinced timing is a thing and almost positive limb tips do not return at the same time. The string pulls them back at the same time but doesn't push them back. I shared a few years ago a theory I have I call a limb wave theory. It involves manipulation of the time timing to form a wave that transfers into the string. ThY causes the string to act like a bullwhip and whip the arrow faster.

Thats the abridged version anyway.

[Tuomo]

Please see these videos. I made tests with high speed camera years ago.

https://www.youtube.com/watch?v=dUskzh9jaBA
https://www.youtube.com/watch?v=EZ4TdACqABE
https://www.youtube.com/watch?v=6iHEiBa7zMg
https://www.youtube.com/watch?v=xGgWZYny9RM

So, you can decide how much the tiller (and limb timing) is affecting.

[Del the cat]

yes but one end may not react to the loose as fast as the other, or put another way
one end can have more hystersis than the other

 the string comes tight at the end of the release stroke, the timing is the same because there is only one string to define the moment, the tips are suddenly stopped at the same time but the midlimbs (with more mass) are following through and will still move foreward depending on the momentum of that particular end of the bow, and the unevenness or difference of momentum is felt as shock

Nice explanation
Del

[Del the cat]

Please see these videos. I made tests with high speed camera years ago.

So, you can decide how much the tiller (and limb timing) is affecting.

Ah, thanks... I thought I'd seen some videos, but couldn't find them!
Looks like the limbs return together but there is some vibration and rotation at the grip (other views are also available  )
Del

[Eric Krewson]

I always repeat my findings that wood is wood, nothing consistent about a stave from one end to the other, as bowyers we have to adjust for this inconstancy or we will have a shocky bow even if the measurements are perfectly alike limb to limb. That is one reason I like sister billets for a bow because they are more identical, most of the osage staves I have cut have wider rings at what was the tree's base compared to the ring structure 6' up the trunk.

[bassman211]

Limb timing can be an issue with wheel bows for sure.