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    Steel Alchem Prod Feet Per Second

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    Hotspur
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    Steel Alchem Prod Feet Per Second

    Post by Hotspur on Sun Dec 02, 2012 5:06 pm

    Using Audacity sound program I looked at half dozen 50 foot shots, (I know, go purchase a chronometer!)

    I don’t have enough build experience to know if I should be disappointed with the following results... (Ignorance is bliss?)

    175 lbs steel prod
    3.5” brace
    8” draw

    425 grain bolt
    50 feet
    Flight time .297 ms

    168 feet per second

    I measured six shots all identical times (mic in centre of range to cancel speed of sound error)

    How does this compare to others experience?
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    Re: Steel Alchem Prod Feet Per Second

    Post by Todd the archer on Sun Dec 02, 2012 7:25 pm

    I think that is pretty close. my 205 pound prod from Alchem shot a similar bolt at 207 fps. With a 532 grain bolt it got 190 fps.

    With the steel prod you can figure about 1 fps for each pound of draw weight and for each 10 grains of bolt weight 1 to 1.5 fps.



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    Re: Steel Alchem Prod Feet Per Second

    Post by MRobin on Mon Dec 03, 2012 1:27 am

    This is what I would expect with these short medieval draw lengths.
    That's why ancient manufacturers rapidly came up with cocking devices that could cope with like >800 lbs steel bows, allowing crossbows to equal the killing range of warbows, with more accuracy !
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    Re: Steel Alchem Prod Feet Per Second

    Post by Todd the archer on Mon Dec 03, 2012 2:57 am

    Keep in mind that steel prods have a certain max "dry fire" speed. Would not expect much faster speeds than maybe 230 fps no matter how light the bolt. The greatest advantage of higher draw weights is their ability to cast proportionally heavier bolts at the same speed.



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    Re: Steel Alchem Prod Feet Per Second

    Post by Zardoz on Mon Dec 03, 2012 5:18 am

    That still sounds kind of slow even for a steel bow. Is maybe the string pressing a little too hard on the top of the tiller?
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    Re: Steel Alchem Prod Feet Per Second

    Post by B.Cheers on Mon Dec 03, 2012 6:57 am

    @Zardoz if you look at his crossbow its a frictionless setup so there is nothing for the string to press/rub on
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    Re: Steel Alchem Prod Feet Per Second

    Post by Todd the archer on Mon Dec 03, 2012 7:28 am

    The string being used is also a factor. How many strands and materials as well as construction methods play a part.

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    Re: Steel Alchem Prod Feet Per Second

    Post by actionbow on Mon Dec 03, 2012 7:43 am

    A couple things, first placing the mic in the middle does nothing to negate speed of sound issues. Think about it. The sound still has to reach the mic. Half as far at firing and striking vs real-time at firing and twice as far at striking. It amounts to the same thing. Second a chrony would measure muzzle speed which would be higher than total flight time but I am sure you realized that.
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    Re: Steel Alchem Prod Feet Per Second

    Post by Zardoz on Mon Dec 03, 2012 7:54 am

    B.Cheers wrote:@Zardoz if you look at his crossbow its a frictionless setup so there is nothing for the string to press/rub on
    Sorry, I didn't see that.

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    Re: Steel Alchem Prod Feet Per Second

    Post by MRobin on Mon Dec 03, 2012 9:37 am

    actionbow wrote:A couple things, first placing the mic in the middle does nothing to negate speed of sound issues. Think about it. The sound still has to reach the mic. Half as far at firing and striking vs real-time at firing and twice as far at striking.

    If it takes as much time for the firing sound as for the striking sound to travel to the mic, then there is no more to worry about speed of sound correction, given that we only care about a T2 - T1 thing
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    Re: Steel Alchem Prod Feet Per Second

    Post by Hotspur on Mon Dec 03, 2012 11:50 am

    Todd the archer wrote:The string being used is also a factor. How many strands and materials as well as construction methods play a part.

    Todd

    Hi Todd,

    The string is Dacron B50, 50 strands from Alchem.

    Ernest
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    Re: Steel Alchem Prod Feet Per Second

    Post by Hotspur on Mon Dec 03, 2012 12:03 pm

    Hotspur wrote:

    175 lbs steel prod
    3.5” brace
    8” draw



    I messed up my own stats, its a 3" brace, 8.5" draw...

    I have a 225lbs on order from Alchem, will look forward to trying that next fall Rolling Eyes ...
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    Re: Steel Alchem Prod Feet Per Second

    Post by actionbow on Mon Dec 03, 2012 12:34 pm

    MRobin wrote:
    actionbow wrote:A couple things, first placing the mic in the middle does nothing to negate speed of sound issues. Think about it. The sound still has to reach the mic. Half as far at firing and striking vs real-time at firing and twice as far at striking.

    If it takes as much time for the firing sound as for the striking sound to travel to the mic, then there is no more to worry about speed of sound correction, given that we only care about a T2 - T1 thing
    I guess you are right. Didn't think of it that way. Self correcting since the delay is equal. Duh on me.
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    Re: Steel Alchem Prod Feet Per Second

    Post by Zardoz on Mon Dec 03, 2012 2:03 pm

    Hotspur wrote:
    Hotspur wrote:

    175 lbs steel prod
    3.5” brace
    8” draw



    I messed up my own stats, its a 3" brace, 8.5" draw...

    I have a 225lbs on order from Alchem, will look forward to trying that next fall Rolling Eyes ...
    Good luck getting the Alchem prod by next fall.
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    Re: Steel Alchem Prod Feet Per Second

    Post by Hotspur on Mon Dec 03, 2012 4:14 pm

    Zardoz wrote:
    Good luck getting the Alchem prod by next fall.

    Yes, I have ordered a couple things from Alchem. The quality was always good in my experience but man, the delivery times are measured with tree rings.

    Love the Zardoz. I actually went to a theater to see that in 74 smack
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    Re: Steel Alchem Prod Feet Per Second

    Post by Zardoz on Mon Dec 03, 2012 5:39 pm

    Lol, hardly anyone knows about the movie and quote!

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