Pellet Crossbows

First topic message reminder :

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.

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.

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.

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.

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

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...?

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.

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.


tom

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.
Sep