Scientific Limb Comparison

[CUBowman]

Has anyone ever done a proper analysis of limb performance? I'm trying to find data on draw/force curves and limb speed for the major limbs.
I imagine that the manufacturers do these tests but understandably don't publish the results.
All the rubbish you see in the advertising like "limb x is 12.83% more stable than any other limb" or "limb y is 8.9% more efficient than any other limb" is not at all helpful becuase they take pains to not define 'stability' (not a quantitative measurement anyway, how do you put a number on it?) or 'efficiency' (what efficiency are the measuring there, the work done to arrow speed ratio, the energy stored to arrow energy ratio, or the amount of hot air to revenue ratio?)
I'd really love to see a proper set of measurements. Failing that I'd love to gather a set of measurements. I'm an engineering student, so it'd be no hasstle to set up a rig to measure draw force profiles and arrow speed while varying:
Limb type,
Limb length,
Limb poundage,
& Poundage adjustment

Unfortunately I don't have the means to get hold of the the limbs themselves to do the tests. Is there a shop owner who would be interested in doing this?
Alternatively, I've noticed that the chaps from Border on here think very highly of the performance of their limbs, would they care for an independent investigation to put that to the test?

[simon m]

Mike at the archery warehouse has chrono'd most top end limbs back to back on the same set-up he's interesting to talk to.(this was lastyear dunno if he's investigated the new models in the same way.)


Only true test would be a hooter shooter(mechanically perfect machine archer)
& brand new same poundage limbs on the same riser shooting the same arrows indoors etc.

Maybe a magazine ought to do an independant limb test? like Car & bike mags?

[CUBowman]

Originally Posted by simon m

Mike at the archery warehouse has chrono'd most top end limbs back to back on the same set-up he's interesting to talk to.(this was lastyear dunno if he's investigated the new models in the same way.)

Ok, thanks. I'll look him up.

Only true test would be a hooter shooter(mechanically perfect machine archer)
& brand new same poundage limbs on the same riser shooting the same arrows indoors etc.

That's what I was thinking, yes. It wouldn't be too difficult becuase you don't really care where the arrow goes so long as it hits the boss, the only measurement which needs to be precise is the draw length.
I'm not even sure if you need the rig to be dynamically the same as a real archer after release (riser held rigidly or on a sling like a real archer). Obviously without a realistic release you can't take any readings about the vibrations on loose. However, I wasn't planning to anyway becuase that would require the machine to be almost perfectly bio-mimetic, which is really difficult to do. I think that for a comparitive test a rigid grip on the riser is fine, it would allow perfectly fair comparision of the relative performance of the limbs. The absolute values would be wrong, but that doesn't matter because they would only be relevent to someone shooting the exact same set up as the one being tested anyway.

Maybe a magazine ought to do an independant limb test? like Car & bike mags?

Yes, good idea.

[moo-mop]

This is what easton's little gadget is supposed to do and some shops do have these.

As mentioned I expect your own variation would probably mask the differences if you're planning to do the shooting. First make a simulated recurve machine, and prove it shoots like a recurver, with high speed cameras (this has been done in other papers - visit the cam university library to see them). You don't actually have to simulate all aspects to get arrows that fly like recurve arrows.

Even then each set of supposedly the same limbs will have intrinsic variation and tolerances making comparisons rather difficult to judge ie you'd only get data on the actual pairs of limbs you test and might not be able to extend that data to other limbs of supposedly exactly the same specs (btw dealers understandably don't stock limbs of some types - eg medium and 42lbs).

Finally you'd have deal with issue of whether you are setting the bows up right to maximise their efficiency. For me I compared one 70in bow with a 68in bow and discovered bareshafts in different places even when the arrows have the same speed coming out of them.

[JohnK]

A French magazine did something like this in 2002. I have a PDF of the article back home; PM me your email address and I'll send it over when I can.

[worthipa]

Originally Posted by JohnK

A French magazine did something like this in 2002. I have a PDF of the article back home; PM me your email address and I'll send it over when I can.

Would it be appropriate to post it to the Drop Box or somewhere else suitable on AIUK? This matter does come up fairly regularly.

[Ski]

Originally Posted by CUBowman

Has anyone ever done a proper analysis of limb performance? I'm trying to find data on draw/force curves and limb speed for the major limbs.
I imagine that the manufacturers do these tests but understandably don't publish the results.
All the rubbish you see in the advertising like "limb x is 12.83% more stable than any other limb" or "limb y is 8.9% more efficient than any other limb" is not at all helpful becuase they take pains to not define 'stability' (not a quantitative measurement anyway, how do you put a number on it?) or 'efficiency' (what efficiency are the measuring there, the work done to arrow speed ratio, the energy stored to arrow energy ratio, or the amount of hot air to revenue ratio?)
I'd really love to see a proper set of measurements. Failing that I'd love to gather a set of measurements. I'm an engineering student, so it'd be no hasstle to set up a rig to measure draw force profiles and arrow speed while varying:
Limb type,
Limb length,
Limb poundage,
& Poundage adjustment

Unfortunately I don't have the means to get hold of the the limbs themselves to do the tests. Is there a shop owner who would be interested in doing this?
Alternatively, I've noticed that the chaps from Border on here think very highly of the performance of their limbs, would they care for an independent investigation to put that to the test?

Found this on the Border site. May be of some use.
Border Archery

Ski.

[Ski]

Here is one from Hoyt.
http://www.hoyt.com/accessories/imag...ulletin_07.pdf

Have fun.

Ski

[moo-mop]

Ski: A draw force curve is easy to do but in isolation doesn't tell you how much of that force is used to move the arrow and how much is used to move the limbs.

[Ski]

Originally Posted by moo-mop

Ski: A draw force curve is easy to do but in isolation doesn't tell you how much of that force is used to move the arrow and how much is used to move the limbs.

You do have a point there.

Is there not a standard for this?

So would you say that they are not worth the paper they are written on?

What would be a better alternative?

Ski.