Stupid question

[DC]

If I have a 40# bow, would each limb measure 20# separately? So for testing components like joints and siyahs I should stress them to half the draw weight? Plus a large safety margin of course.

[Jim Davis]

yes

[Del the cat]

No, I'd test 'em to 40#
If you pull to 40# there is 40# of tension in the string and it's pulling on both limbs...
I'm not saying I'm right and I'll be only too happy to be shown to be wrong.
But there was a similar sort of question on another forum about if pulling 40# is there 40 on your fingers and 40# on your bow hand or 20# on each.... which is the wrong way to look at it.
I think you have to consider the entire system and not break it into parts.
Del

[Jim Davis]

Del, it's mechanics, or physics. Two 20# forces added together equal 40#.

[bjrogg]

Yes and no.lol I guess ask a stupid question get a stupid answer. Just kidding DC. I would guess awfully close but that's just a guess. It seems like if it didn't it would rock in your hand but like I said I'm just guessing
Bjrogg

[PEARL DRUMS]

Del is right. If you want to test a handle joint on a 40# bow then that joint is holding 40#, not 20#.

[Jim Davis]

OP did not say HANDLE joints. He said joints and siyahs.

Just  to provide more reason to scratch one's head, if you string a bow with its string behind the string of a strung bow (><), each bow being 60#s pull, then pull them away from each other to full draw, it will only take 60# pull to do it. 

[PEARL DRUMS]

Touche', Mr. Davis

[Del the cat]

It's not as simple or obvious as it seems and it depends on how you do your testing.
If we consider a symmetrical bow pulling 40# the tension on the bow string either side of the hand is not 40# nor is it 20# because of the angles.
Thus you can't just hang a weight of 40# or 20# on the joint.
I've had a quick look at the physics, but can't be bothered to work it through.
I still don't claim to know the detail, but I do feel it would be prudent to test to full draw weight.
it's a bit like the long string vs braced bow thing.
I expect the full analysis of the mechanics taking into account the leverage on the siyahs and angle of string and limb etc would be quite tortuous.
For anyone who doubts that it is complex. Consider the case at brace... there is zero draw weight, yet the joints will be under considerable stress... so it's not simply down to draw weight.

To summarise:- I don't know, but I'm smart enough to realize that I don't know 
Del

[bradsmith2010]

i wouldnt hurt to test at 40,,, I used to test the tips till they would break so I knew the limit,,

[DC]

Actually I was going to test to 60#. Three times load like strings. I just wanted to get a minimum. This is like the loop on a Flemish twist string. It looks like it would be half the strength but it isn't.
It also is like stacking scales. I put my small gram scale on my bigger gram scale and zeroed them both out. I put a 100 gr weight on the small one. I really didn't know what to expect. They both read 100 gr.

[willie]

not stupid at all DC. I am surprised at some of the answers posted above. In theory, tension changes with string angle when the nocks are a fixed distance apart. Since a bow bends and the NTN distance changes, so perhaps the easiest way to find out wothout too much math, would be to put a scale in bow string and make a test.

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http://www.williamhackett.co.uk/phpmedia/graphics/79acc09728a9669320a3de67d0db3d88.jpg

[Del the cat]

I've just some rough calculation assuming the string forms a 90 degree angle on the fingers and pulls on the tips at 90 degrees.
That would give the string tension and thus force on each tip of about 0.7 times the draw weight.
So for a 40# bow there would be 28# on each tip.
Now this doesn't even start to look at the leverage onto the siyah....
Del
(I still reserve the right to be wrong  )

[PatM]

Actually I was going to test to 60#. Three times load like strings. I just wanted to get a minimum. This is like the loop on a Flemish twist string. It looks like it would be half the strength but it isn't.
It also is like stacking scales. I put my small gram scale on my bigger gram scale and zeroed them both out. I put a 100 gr weight on the small one. I really didn't know what to expect. They both read 100 gr.

Don't you mean an endless loop?

[DC]

Oh yeah