Limb Timing

[Del the cat]

There is some woolly thinking going on here .

It doesn't matter what the limbs are!
One could be a limb sawn off a 50# bow and one off a 20# bow joined together as a take down...
At full draw the limbs will automatically be in balance because they are joined by a string which will have the same tension along it's entire length.
So the limbs will end up under the same force! Let's call it say it 35# for the sake of the discussion
The "50" limb will not bend so much as it did in the 50#bow and it will only be pulling 35#.
The "20" limb will be over strained and will be pulling 35#
So you see at full draw it is in balance.... (Yeah it won't look pretty tho'  )
If we freeze frame the bow every inch or so during the loose.... we can apply exactly the same logic to show that the two limbs are still in balance because the tension in the string is still the same along it's length.
When the bow is shot  the limbs will act as one, because the whole thing is one assembly.
BUT!!!... IF we get to full draw and cut the string....
THEN and only then can one limb race ahed and get home first... but without the string... it's not a bow!

Right I'm quite happy to be shown to wrong on this! If someone can point out the error of my ways...
I'm willing to go sit on the naughty step and eat humble pie, but I think my reasoning hold up, and it certainly agrees with that slo mo video.
Del

[Buckeye Guy]

By joe I think he's got it !
Good job Del !
cut the string 

[Marc St Louis]

Sounds good to me Del

[Dances with squirrels]

That's failed logic, Del. As you define it, they may be balanced IF the archer does NOTHING to alter the imbalance with his bow hand, but your balance requisite doesn't take into account the effects..... one of them being the positional relationship of the nock point to the shelf.

We always draw to the same anchor point, but with one limb's relative strength greater than the other, there are consequences... which I explained above, and you partially explained in your last post... i.e. the stronger limb won't flex as much as the weaker one... so the weaker one 'gives' to the stronger, giving away nock position relative to the shelf as it does so.

Again, since we always come to the same anchor, any unbalanced bow, especially your 50/20 bow, can/could be seen as the bow tilting in the hand at full draw, which I've seen on every bowmaking site I've visted. The more the limbs are out of balance, the farther the bow will try to tilt in the hand, and the farther the nock of the arrow will deviate from perpendicular travel relative to the shelf. There are also consequences to THIS, upon release.... arrow porpoising, handshock, inefficiency, unbalanced draw, etc.

[toomanyknots]

My goal is to build bows that are balanced at full draw... meaning, at full draw the way I hold the handle and string, both limbs will exert equal strain on the string, resulting in a bow that doesn't try to tip in the hand during the draw, with the nock traveling straight back perpendicular to the handle, and straight forward upon release, with both limb tips arriving at true brace simultaneously. If one limb's strength (relative to all factors) is stronger, the nock will be pulled toward it during the draw relative to the shelf, and move away from it upon release. I don't want the nock end of my arrow treated that way. As Del mentioned, the string will try to stop them both at the same time, but a stronger faster limb gets there first, while the weaker acting limb is still on its way. This 'distorted brace' happens for an instant until the bow can 'right itself'. This is probably the instant we see in your pictures above.

If one limb is stronger than the other, and we work to balance them, it doesn't matter if one is weakened or the other strengthened, but usually it's easier to remove wood from the stronger.

If you're building symmetrical bows, tillered positive, with the shelf 2" above the center, you have probably become used to the feel of them shifting from static balance(at brace) to dynamic (at full draw) and posible putting extra pressure here or there where you feel it's needed. A bow that is balanced might feel odd to you and you may need to make some adjustments.

You said you dont know how someone could shoot a bow with a stronger top limb. First understand that just because a bow shows the top limb stronger at brace doesn't necessarily mean it will feel and ACT stronger at full draw... or any time during the draw. Much depends on design and the shooter's peculiars.

I make my bows to feel balanced at full draw, and depending on those things mentioned, and others, sometimes my bows are tillered negative, sometimes even, and less often, positive... but they ALL feel balanced the same at full draw.

Well whatever works for you I guess. I would never tell anyone asking though to make the weaker limb the bottom one form my experience. For one, I believe the bottom limb gets stressed more, and needs to be a bit sturdier than the top. And two, it doesn't make sense. I don't nock my arrows more than 1/2" above center usually, if they were two inches above center the upper limb would need to be weaker, not stronger like you are proposing. (when you nock the arrow 2" above center, say on a 72" bend in the handle elb for example sake, one limb becomes 34", and the other becomes 38". So you have essentially shortened the top limb. And when you shorten the top limb, it becomes stronger, so you need to weaken it to balance the draw, giving the bow it's yumi like asymmetrical brace profile, aka, positive tiller.) 

Edit: Fixed stupid math error,   

[PEARL DRUMS]

I wish I could explain why my bows shoot great. But I cant. I just whittle them out and call them bows when they feel like bows. If I could explain it; I may have some useful to offer here.. Another reason Im not much of a teacher.

[toomanyknots]

BUT!!!... IF we get to full draw and cut the string....
THEN and only then can one limb race ahed and get home first... but without the string... it's not a bow!

That's one thing that boggles me, is how utterly crazy the string seems to go when I fire the bow from frame to frame. It seems to go nuts, and I shoot either low stretch linen or fast flight.

[PatM]

Remember that the more accepted theory is that bow strength does not make nearly as much difference in limb speed as one might believe.
 So two limbs that are at most a pound or so apart are not actually going to be in some sort of one-sided race.
 The timing theory is a wildly convoluted theory to explain something that is likely far simpler.

[adb]

I've never really fully understood this whole argument about bottom/top limb & stiffness, positive tiller, etc.

With bendy handle bows and ELBs, I only set the arrow pass about 1/2" to 1" max above center anyway, so the limbs are effectively the same length. There's no riser per say, and you can set the grip wherever you want.

With stiff handled bows, the limb is only bending between the fade and tip, in both limbs. If you have a 68" bow with an 8" non-bending riser for example, regardless of where you place the arrow pass within the 8" non-bending handle, the 30" bending portions of the limbs are still the same length. Even if you turn the bow upside down. The string does become longer on the bootm limb on this type of bow, but that doesn't seem to matter to me.

Therefore, I tiller my bows from geographic center, and make the limbs bend evenly. As the slow-mo video clearly shows, the tips have to recoil at the same speed regardless, when they're connected by a string.

Making the limbs different lengths (aka Torges style) is a different story. The arrow pass becomes the fulcrum and balance point of the bow instead of the center.

[toomanyknots]

I've never really fully understood this whole argument

The more I try to, I think the less I get it,  .

[adb]

For me, and the longevity of the bow, I think it's more important that the tiller is even.

[Marc St Louis]

The improperly tillered bow in the link that Dell posted shows a bow that must have a stronger lower limb for them to bend the way they do yet they still return exactly at the same time.

As I said earlier.  If you increase the mass on the limb tip of a properly tillered bow then you may see limb timing that is off since the higher mass should slow that limb down.  For a bowyer to inadvertently do this while making a bow seems unlikely since most try for symmetry.

[adb]

When I look at a stiff handled bow like this, the bending portions of the limbs (from fade to tip) are still the same length regardless of which one is up/down. The bottom limb is longer than the top if you're considering where the arrow pass is, but the bending portion is still the same. The string does become different lengths, but does this effect anything?

I've always kinda thought this whole 'gotta make the bottom limb stronger' stuff was an urban legend and myth. Seems to be a few of those in archery. People just seem to accept this as gospel, but never really stop and think about it.

This bow was tillered evenly from dead center, and it still sure seems to bend evenly in the hand. The arrow pass is 2" above center.

[PatM]

Didn't look at the link but I know one of those videos shows weight added to a limb to test the theory further. Can't remember if it is a well tillered bow or not with weight added.
 I know I have seen video posted by one guy who firmly believes in timing and two separate videos show one bow tipping forward on release and the other kicking forward in the lower limb. They felt right to him which is probably more what is going on.

 The picture Adam posted above shows why I personally prefer positive upper limb tiller. I want the bow handle tipping slightly forward since that is what our wrist and hand does naturally if we just clench our fist lightly and hold it at arms length.
 See how the upper portion of his wrist is kind of  "crushed"? I don't want that. That has little to do with how the bow actually works itself but I want everything in the equation working together.
 ps: look at a Yumi at full draw and note how it looks more "pointable" with the forward tilt to the handle.

[Dances with squirrels]

Pat, instead, I would harmonize the limbs and shape the grip to tip my hand, while not tipping the bow.