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    Pellet Crossbows

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    Xamllew
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    Pellet Crossbows

    Post by Xamllew on Wed Jun 24, 2015 4:52 pm

    In theory it seems like a great idea, a crossbow that you can shoot all day without worrying about losing your bolts! I'm really interested in this concept. I've done some searching and there seems to be very few contemporary examples of stone-firing crossbows. All I really know is that they were used for bird hunting for some time in the 18th and 19th century.

    In the past I tried some mockups for a stone bow using PVC for the limbs of the bow and aside from the incredibly scary fact that if the pouch reverses upon firing you might lose an eye (stone bows normally use two parallel strings with a pouch connecting them), it wasn't a complete failure. Now I kinda want to experiment with a crossbow in the same way, but I haven't really got any idea what to expect in performance since there seems to be nobody else trying them.

    I have an idea for a crossbow which uses a tiller with an enclosed track, much like a gun barrel which you muzzle load with a ball after charging. The inside of the "barrel" would be slightly tighter at the back end so that the ball gets lodged just enough to not fall out when aiming down.
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    Re: Pellet Crossbows

    Post by kenh on Wed Jun 24, 2015 8:46 pm

    There are a number of barrelled crossbows aka pellet or stone bows) in museum collections.  If you google search "barrelled crossbow" images you'll see a number of examples.

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    Re: Pellet Crossbows

    Post by phuphuphnik on Wed Jun 24, 2015 10:04 pm

    Here is what we did last year: http://thearbalistguild.forumotion.com/t1179-7th-grade-stonebow-progress

    They worked really well. The barrel is a little different. We based the barrels on those little white slingshot marbles. The kids discoverd that the marbles would shatter on a cinderblock wall if you are closer than 50 feet. They were accurate too. We also discovered that you can skip the marbles across a pond!
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    Re: Pellet Crossbows

    Post by Xamllew on Thu Jun 25, 2015 9:35 am

    phuphuphnik wrote:Here is what we did last year: http://thearbalistguild.forumotion.com/t1179-7th-grade-stonebow-progress

    They worked really well. The barrel is a little different. We based the barrels on those little white slingshot marbles. The kids discoverd that the marbles would shatter on a cinderblock wall if you are closer than 50 feet. They were accurate too. We also discovered that you can skip the marbles across a pond!

    Oh those are very nice. Never got nearly as exciting projects in 7th grade.

    Do you know any specs of the bow such as prod weight and draw distance? I'm really only interested in seeing if I can make something more powerful than a slingshot. If I can't get a prod to perform on par with slingshot rubber, something around 200fps with a .45 steel ball, then I'm not sure I'd even bother.
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    Re: Pellet Crossbows

    Post by Geezer on Thu Jun 25, 2015 10:21 am

    Geezer here on pellet bows.  Though I will argue loud and long against people making double-string pellet bows... the kind with the ball-pocket in the middle because they can be made to shoot backward.. (yes, I have the damaged eye to prove that) barrelled bullet-bows should be quite safe, and don't require the troublesome doubled-string. They'll shoot pretty much anything you can cram down the tube and will give hours of fun with marbles, clay-balls or whatever. Slur-bows (with a wooden plate over the table will work just as well.  So go have fun.
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    Re: Pellet Crossbows

    Post by Gnome on Thu Jun 25, 2015 11:44 am

    I highly recommend Richard Middleton's "Man-Powered Weapons and Ammunition" for anyone interested in building crossbows, slingshots or other such implements of destruction, but particularly if you want to use bullet-type projectiles. A very informative and entertaining read.
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    Re: Pellet Crossbows

    Post by septua on Thu Jun 25, 2015 12:27 pm

    Xamllew
    Your choice for a single string type was prudent for safety as well as ease of making and mass consideration.  Mine is home built with a 90# prod made by Slowbows for Alchem and throws with more accuracy than I can aim and shoot. I blame my eyesight as well as an awkward thumb release-sure! A velocity of 217ft/s was calculated by the gravity/drop distance formula to give time of flight for (1) shot.
    Rather than a pouch, a light weight (hmwpe) shuttle holds the ball shot for a total of 13 grams which is almost at a dry fire limit. You can see my avatar for a head on view of the shuttle and removable launch track. The ball, held by a magnet in the trigger case nests in a conical socket.  At release the shuttle with ball bearing leave the magnet behind. Of course the shuttle is held fast by the bowstring.
              
    Here is a test of a 19th century double string bullet crossbow vs. slingshot.
    http://www.ctmuzzleloaders.com/ctml_experiments/bulletbow/bulletbow.html


    Last edited by SEPTUA on Sun Jun 28, 2015 5:10 pm; edited 2 times in total (Reason for editing : corrected velocity from 220ft/s to 217ft/s 10 shots to 1 shot)
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    Re: Pellet Crossbows

    Post by Geezer on Thu Jun 25, 2015 7:00 pm

    In fact, I have seen a T-shaped shuttle that can be attached to a standard crossbow string that allows ordinary bolt-bows to shoot projectiles. There's a drawing of the device in Egon Harmuth's "Die Armbrust' and as I recall, a similar one is mounted on a crossbow in the Metropolitan.  The little self-cocking bow with inlaid ivory stands of arms all over and a wheel-lock gun mounted below the grooved steel table.  I wonder if anybody has pics of that bow?  There's a nearly identical one in Vienna... maybe that's the one with the stone-shuttle attachment.  Duhh, sometimes my brain gets fuzzy with too much crossbow stuff.  Geezer
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    Re: Pellet Crossbows

    Post by Xamllew on Fri Jun 26, 2015 12:47 am

    Thanks for the info, SEPTUA. What size ammo were you getting those velocities with? I like the idea of a shuttle device for the pellet, I found this video showing a product that does just that.

    Probably a better idea then a closed barrel mechanic, this could allow you to switch from bolts to stones in the field in seconds. I can't foresee any major safety issues with it, shuttle could possibly blow up with a strong enough crossbow though.


    Last edited by Xamllew on Fri Jun 26, 2015 12:49 am; edited 2 times in total (Reason for editing : Forgot the video)
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    Re: Pellet Crossbows

    Post by Geezer on Fri Jun 26, 2015 6:51 am

    Yes, that's the device.  The concept shows up on crossbows from 16th or 17th centuries.  Some have a deeper pocket, so presumably you might be able to load multiple shot as well as single balls.  I think medieval bows mostly used baked clay balls... essentially low-grade ceramic for projectiles, but I can imagine shooting small shot for closer range eradication of rats or pest-birds.
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    Re: Pellet Crossbows

    Post by septua on Fri Jun 26, 2015 8:02 am

    Xamllew
    I am now using 3/8”balls but have also shot .400” lead with a hinged flip up retainer on top of the trigger housing.
    http://www.mcmaster.com/#standard-steel-balls/=xshguh

    re: Kostka Lightning
    I am familiar with this item. It is possibly adjustable to maintain max draw length by shortening down so the latch pin is reinserted within an inch of the string slot. The front cup and retaining clip are ball size specific somewhere over ½”. The reduced draw length of the uncut item should not be a problem with modern long draw bows. My bow latches a little over 1” behind the string which retains the designed 8” draw.


     
     
     
    Aside from the caveats of the 2 string w/pouch bullet bow, if built as intended there can be a consistency from shot to shot. It took quite a bit of experimentation to arrive at my final track profile. There is a box full of shuttles of all material type and shapes: aluminum flats and tubes, wood, plastics. The final shuttle is held to the track with moderate string down force which in theory makes for shooting consistency as long as that shuttle stays in full contact with the track.
    I tested for string over travel and found about 1-1/2”. That brings up the question, how does this effect consistency (accuracy) in any crossbow?
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    Re: Pellet Crossbows

    Post by Geezer on Fri Jun 26, 2015 8:20 am

    I am SO PLEASED to see this bit of medieval/renaissance technology reborn. The weight of the shuttle is fairly important... it will cost you some lost energy and perhaps slightly increase vibration/recoil.  Maybe a bit of extra string wear, but if it fits tightly on the string and can't shift around you should be able to establish consistent hitting on your target.  I particularly like the adjustable features, so it can be fitted to different partterns/styles of c-bows.  Hooray.. forward to the 16th century!  Geezer
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    Re: Pellet Crossbows

    Post by septua on Fri Jun 26, 2015 11:43 am

    This is my ball holder (shuttle) after firing more than 2000 recyclable ball bearings and lead rifle balls.

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    Re: Pellet Crossbows

    Post by septua on Fri Jun 26, 2015 12:59 pm

    One important item I have to mention is the need for a fixed pressure pad to prevent the shuttle buckling upward at full draw.  It must be an exact slip fit over the shuttle.


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    Re: Pellet Crossbows

    Post by c sitas on Fri Jun 26, 2015 4:00 pm

    Septua; Would it be possible to have a clear picture of how this fits on the string? And what it looks like. I'm a little foggy on this.
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    Re: Pellet Crossbows

    Post by Xamllew on Fri Jun 26, 2015 4:12 pm

    Oh yeah nice, .40 cal lead at 220fp/s I can live with that. Septua, I have one more question for you, what material is the shuttle made from? I'm guessing Delrin?

    Thanks for all the info, can't wait to try out some ideas once I get some Fiberglass tension rods for prod experimentation.



    Here's another strange design I just found, a magazine fed compound pellet crossbow pistol. Guy looks like a modern Da Vinci.

    Quite an impressive whallop for such a small thing shooting .45 cal balls.
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    Re: Pellet Crossbows

    Post by septua on Fri Jun 26, 2015 6:29 pm

    c sitas
    I left the bowstring out of the picture in order to see its slot just below the top plastic piece (pressure pad). So in this next view a slight amount of shuttle buckling upward is visible which means the pressure assembly needs attention. The ball ammo never comes in contact with the track.



     
     
     
    Xamllew
    1) The 217fps was for (1) 3/8"steel ball at 26'. The lead ones were not measured
    2) The shuttle is of “high molecular weight polyethylene” HMWPE.


    Last edited by SEPTUA on Sun Jun 28, 2015 5:31 pm; edited 3 times in total (Reason for editing : Updated velocity, quantity and shot distance. 220 to 217 10 to 1 25+/- to 26)

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    Re: Pellet Crossbows

    Post by c sitas on Fri Jun 26, 2015 8:04 pm

    I thank you Septua; it's very clear now. I plan on using the same material. Only I have a never ending supply of lead balls.
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    Re: Pellet Crossbows

    Post by Geezer on Sat Jun 27, 2015 9:05 pm

    Back in my old black-powder shooting days, I made a lot of pistol balls out of old wheel-weights from the local tire-shop. They work great, cast in a pistol mold, but do your casting in a well ventilated area. Breathing the fumes is hazardous to your health.  Strike hard, strike often, IN THE MIDDLE.  Geezer

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    Re: Pellet Crossbows

    Post by rolynd on Sun Jun 28, 2015 2:05 am

    Here is a modern Version of a pellet crossbow, http://www.shoottech.com/Page/Web/AR480MARKII
    they use double string but  since they use pulleys the string is less likely to flip. In a more historic build this obviously wont work because you cant use wheels.  
    I think the "flip over" is from the center of gravity of the ball not being aligned with the  appplied force of the string.   Sled or barrel is definitely easier without danger of RTS.

    Here is the picture Geezer was referring to from the Richter Book:



    It is no.4 in the pic, but I must wonder how the  ball was held in place before shooting. with steel balls a small magnet would do but for marbles and clay balls...?

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    Re: Pellet Crossbows

    Post by c sitas on Sun Jun 28, 2015 6:43 am

    Royland, I made that same contraption out of cutting board material. I fiddled with the ball hole  until it would just grip the ball . Make sure it never falls out. I dry fire sure don't help your bow. Mine is slightly different . Just picture  small fingers ,one on each side on the ball. works perfect.Saves on a lot of lost bolts.The wackos don't like lead but oh well.
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    Re: Pellet Crossbows

    Post by septua on Sun Jun 28, 2015 11:13 am

    Rolynd

    Ali can build one of those “STS RAPTOR”!!
     
    RE: The Richter drawing
    If the sled cup was sturdy with a slotted top a narrow wire spring clip, ala arrow hold down will work. Upon release the ball needs no hold down. When shooting lead balls I used a light weight plastic piece that swung up out of the way, but that required an overhead attachment.
    I recommend a purpose built launch track that won’t allow axial rotation and keep the whole affair from touching the center bottom. A close fitting wippe or gafe for spanning makes for consistency and remember if this is for target shooting you’re going to do a lot of spanning.


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    Re: Pellet Crossbows

    Post by septua on Sun Jun 28, 2015 6:03 pm

    Xamllew
    I have updated all of my velocity data on this thread by using the same basic setup but mounted and leveled with more care and rigidity.
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