Re: BP M illing Time

"Darwin" <Darwin72@xxxxxxxxxxx> fired this volley in
news:w6MTi.39448$G23.8326@xxxxxxxxxxxxxxxxxxxxxxxxxx:

Thanks Lloyd.

I have been using this method to compare commercial to home made. To
me it seems like a reasonable that as the objective for lift is to get
the projectile to a known/safe height with a given amount of powder.
If I use slower powder, I need to use more but then I blow out a lot
of incompletely burned powder & I was connerned about setting off
other neighboring pieces with burning powder.

My tests use a fiberglass festival ball mortar and golf ball. Since
the dimensions and weigh of the golf ball are not too far off from a
real festival ball, I thought this might be a good way to check the
powder.

2 Grams of Goex gives me a flight time of 5 sec (launch to landing)
but home made are less and in some cases considerably less. I was
just wondering how much milling it took to start to approach Goex.
(Using Paulomnia charcoal).

Help me, if you will, with the math. The formula for height , given
the gravitational constant & ignoring drag, is (1/2)at2.
Since I assume total flight time is one half total flight time, then
I would think (1/2)a(t/2)2 would give height.
(1/2) * 32 (2.5) **2 = 100 feet for 5 second flight time. 10 seconds
would compute to 10000 feet. Did I get the forlula right ?

You got the formula right on the 2.5 second fall, but I don't know how
you came up with 10K for a 5-second fall. It would be 1600 feet for a
ten second fall.


You cannot ignore drag. I can assure you that the balls never went more
than, oh, five to six hundred feet high.

Falling object at one G, in a vacuum.

Calculated from 1/2(at^2)

1/2(32*5^2) ; 1/2(32*25) ; 1/2(800) ; 400 feet


Done empirically, determining average velocity of each second's fall --
Each second, the velocity at the end of that second (V2) is 32fps greater
than the beginning velocity (V1). The average velocity is (V1 + V2)/2.

16 feet the first second: from zero to 32fps: average velocity 16fps
48 feet the second: from 32 to 64fps: average velocity 48fps
80 the third: from 64 to 96fps: average velocity 80fps
112 the fourth: from 96 to 128fps: average velocity 112fps
144 the fifth: from 128 to 160fps: average velocity 144fps

Sum up the distances traveled in each of the five seconds.

Up 400 feet in five seconds; down 400 feet in another five.
Round trip time of ten seconds

For 2.5 seconds, and the height is 1/2(32*6.25) ; 100 feet
; round trip of 5 seconds.


LLoyd

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