Boo Yew RD

[Tuomo]

I made some calculations according to the draw force table (42,65#@28") and with these chrono numbers: "Speed 320 grain-224fps and 450 grain-196-198".

Stored energy: 62,60 J
efficiency (10 gn/# -arrow): 82,3 %
virtual mass: 6,78 g
calculated 10 gn/# -arrow speed: 200,4 fps

The only problem is tht hysteresis seems to be a bit negative. If that 450 grain arrow speed would be 195 fps, then hysteresis would be about 2 %, but then 10 gn/# -arrow speed drops just below 200 fps.

So, every measurements should be made perfectly and with precise routine. For example, shoot 20 times, measure speed at least with three different weight arrow, then let the bow rest an hour or so. Shoot 20 times and take draw force measurements with precise system.

But, as a conclusion I would say, that the secret of this bow is very low hysteresis. The same is with my fastest bows, they have low hysteresis. But I think that meaning of low hysteresis is already well known fact.

[DC]

That 450 grain arrow actually weighs 451 if that makes any difference. I would redo the test but it would be different today. I don't know if it's humidity or my ineptness but nothing has ever been exactly repeatable. When I was just using one chrono I was happy with the results but now with two the results are always contradictory.

[Markus]

I think the chronies should be moved further apart.
To check if both are correct, how about firing a 22 caliber over the chronies. That bullet will go in a straight line and the reading should be the same if both chronies are right.
Probably have a small hole in the wall, but what a heck.

[DC]

Don't have a .22 any more but I do have a pellet rifle. The bag will stop that. Good idea.

[Badger]

Tuomo, my calculations were very close to yours. I came out with a virtual mass of 90 and efficiency of about 82%. Extremely good numbers. Speaks a lot for low set designs.

[DC]

It took a bit but the pellet rifle worked. I had to change out the LED lights like Willie said. I suspected that but they seemed to work as well as incandescents with the arrows. Wouldn't even trigger with the rifle. What kind of lights are on your chronos Markus?

[DC]

Tuomo, my calculations were very close to yours. I came out with a virtual mass of 90 and efficiency of about 82%. Extremely good numbers. Speaks a lot for low set designs.

Thanks Badger

[Markus]

I bought two sets of these. They have light for Caldwell https://www.lancasterarchery.com/competition-electronics-prochrono-pal-chronograph.html
Scroll down a bit to see the lights

[mmattockx]

Its in the eye of the beholder. If you look foolish to anyone on here, the fool is the observer. Not many on here can get within 30 fps of you. You are making bows that inspire people.

+1, DC's bows are top notch and super fast (regardless of what number the chronograph says today).

When I was just using one chrono I was happy with the results but now with two the results are always contradictory.

 

As the old proverb says - A man with one watch knows what time it is, a man with two is never quite certain.


Mark

[Eric Garza]

Referring back to your force-draw curve, it looks like you hit the inflection point right at 24 inches.

[willie]

Referring back to your force-draw curve, it looks like you hit the inflection point right at 24 inches.

Sounds like a good thing Eric, could you elaborate why its good @24"?

[DC]

And what is it?