bowhack

Man.....I really feel like Crap now....after seeing that my reply was sent to the trash for being argumentative.......Sorry.......My apologies to everyone

Black Frog

bowhack-

no worries mate. We're all here to learn from each other. Everyone's got an opinion, and that is what makes this forum interesting. VERY interesting at times.....

ampahunter

Rangeball, I hadn't laughed for the day--until I read this response---and you're absolutely correct. You guys do have great humor.
Keep it coming!!!

Arthur P

Surely you're not saying the parallel limb and vibration absorption technologies are being developed simply to disquise crappy shooting characteristics! [][>:]

Or to disquise the effects of shooting arrows that are really way too light for the bow...

If you want a real demonstration, grab a straight limb longbow - preferably a 70 pound Jerry Hill Wildcat to get maximum effect - and shoot one 350 grain arrow. Then, when the nerves in your hand and bow arm have recovered, shoot one 700 grain arrow, and compare the feel. You can't rountinely abuse a longbow by shooting it with arrows that are too light. It won't let you. Of course, it doesn't have the 'advanced' technologies built into it to hide those effects.

Black Frog

Not at all. Shooting characteristics of modern compounds have never been better, and neither have the dynamic efficiencies (low VM numbers) of modern compounds.

All I'm saying is that you could have a smooth shooting bow, but it still may have inefficiency within the dynamic shot. Maybe it has bushings that carry a lot of friction, maybe it has horrible nock travel pattern in that some energy is spent on launch flexing the arrow more than another cam design. It may shoot smooth as silk, yet still be inefficient. I don't believe that there is a direct correlation of smooth-shooting characteristics to dynamic efficiency (like you mentioned in a previous post).

Arthur P

I dunno... Seems like when you get off into bearings/bushings, nock travel and such, then you're encroaching into the realm of hysterisis. Which is another measure of inefficiency and another complication.

selway

mass +mass=double mass simple

Black Frog

ok, that's fine. I don't think you're seeing that the VM is a measurement to represent all the combined inefficiencies of the bow/arrow combination upon launch. Add up allllll the stuff that keeps the bow from transferring the absolute 100% of its stored energy to the arrow. Friction, accelerating limb mass, cam mass, string friction, wind resistance on the limb face, whatever. Add up all that stuff that keeps our bow from imparting all the stored energy to the arrow and represent it as an imaginary mass that is launched from the bow at the exact same instant and velocity as our real arrow.

The real arrow being launched will have a weight and speed that we can measure. From this, we can determine the measureable energy of the arrow once it's launched. But that energy of the launched arrow won't be the exact same amount of energy that was stored in the bow at full draw due to losses in the dynamic bow/arrow combination. The VM is the figure used to represent those energy losses upon launch of the real arrow. The VM is a way to quantify the difference between our stored energy value at full draw and the measureable energy of the launched arrow.

If you had reaaallly thick, wide, and heavy limbs that are quite long- they will suck more energy out of the stored energy value upon launch than thin light limbs. It takes more energy to get a heavier mass moving up to speed vs. a lighter mass. Right? Or what if you had cams that weighed 5lbs each(extreme example, I know). It would take lots of the stored energy to get them moving up to speed to launch the arrow. And in both these cases, the draw force curve may the the same as a modern, high-tech compound. But the efficiency numbers (VM values) would not be so hot.....

Arthur P

Isn't it: virtual mass + hysterisis = total inefficiency?

I always thought they were two seperate, distinct things and not components of one another. I mean, just to take bearings for example... It's the weight/mass of the bearings that figure into virtual mass, and how much friction they have with the axles factors into hysterisis. Right?

Pinwheel 12

You guys having fun yet? Pinwheel 12