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More on crossbows (Read 2883 times)
Bikewer
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More on crossbows
Nov 1st, 2007 at 11:54am
 
My first attempt at building a crossbow worked out pretty well ( I had pics up but I guess the file was too big), and I'm inspired to make a more refined model.

Just got an excellent book from the library, written in 1906.  It's a detailed history of the weapon, including instructions for building several different types.   ( The Crossbow, Medieval and Modern, Military and Sporting, It's Construction and Management.....Hehe- those turn-of-the-century authors....)

Anyway, there are limits to what you can do with a wooden bow.  I intend something in the 150-175 pound range, and wood tends to be excessively thick and heavy.
I can, of course, just buy a steel prod from Alchem for about 60 bucks.  Still, I'd rather make....
For years, I've heard that an automotive leaf spring can be used.  In fact there are dozens of references on the Web to this effect.   BB posts, little factiods, that sort of thing.  "All you have to do is get an automotive leaf spring!"

Unfortunately, I can't find a single reference as to anyone who's actually done this.  No pics, no build-a-longs, no articles.    
No dimensons, no information as to what size spring to look for, etc, etc.

If you look at auto-parts sites, it's obvious that there's a very wide variety of springs available, from very light (like for trailers) to very heavy (trucks).
All these have a pretty strong curvature built in, which would seem to either limit available power or cause excessive draw length.
And it appears you'd have to do a lot of cutting and grinding to remove the shackle mounts and cut notches for the string. 

Anyone know of any references at all?
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Dravonk
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Re: More on crossbows
Reply #1 - Nov 2nd, 2007 at 11:44am
 
Bikewer wrote on Nov 1st, 2007 at 11:54am:
All these have a pretty strong curvature built in, which would seem to either limit available power or cause excessive draw length.

Maybe you could build it in the other direction so that it acts like a recurve/reflex bow? But I haven't done this and I don't know how safe it is.
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Bikewer
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Re: More on crossbows
Reply #2 - Nov 2nd, 2007 at 3:29pm
 
I actually thought of that; if the spring were not too severely bent, you could string it "backwards", making a deflex design.

There might be problems with failure, but it might be something to experiment with.  I may run by a local salvage yard this weekend just to see what's available.
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winkleried
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Re: More on crossbows
Reply #3 - Nov 3rd, 2007 at 12:31pm
 
Might ask some of the crew over on the Yahoogroup Crossbow. These are crossbowmakers of a wide range of skill.Url is:
http://groups.yahoo.com/group/crossbow/

Marc Adkins


Bikewer wrote on Nov 1st, 2007 at 11:54am:
My first attempt at building a crossbow worked out pretty well ( I had pics up but I guess the file was too big), and I'm inspired to make a more refined model.

Just got an excellent book from the library, written in 1906.  It's a detailed history of the weapon, including instructions for building several different types.   ( The Crossbow, Medieval and Modern, Military and Sporting, It's Construction and Management.....Hehe- those turn-of-the-century authors....)

Anyway, there are limits to what you can do with a wooden bow.  I intend something in the 150-175 pound range, and wood tends to be excessively thick and heavy.
I can, of course, just buy a steel prod from Alchem for about 60 bucks.  Still, I'd rather make....
For years, I've heard that an automotive leaf spring can be used.  In fact there are dozens of references on the Web to this effect.   BB posts, little factiods, that sort of thing.  "All you have to do is get an automotive leaf spring!"

Unfortunately, I can't find a single reference as to anyone who's actually done this.  No pics, no build-a-longs, no articles.    
No dimensons, no information as to what size spring to look for, etc, etc.

If you look at auto-parts sites, it's obvious that there's a very wide variety of springs available, from very light (like for trailers) to very heavy (trucks).
All these have a pretty strong curvature built in, which would seem to either limit available power or cause excessive draw length.
And it appears you'd have to do a lot of cutting and grinding to remove the shackle mounts and cut notches for the string.  

Anyone know of any references at all?

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Bikewer
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Re: More on crossbows
Reply #4 - Nov 3rd, 2007 at 3:19pm
 
Hehe-I belong to a dozen Yahoo groups, wonder why I didn't think there would be a crossbow-oriented one.....
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winkleried
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Re: More on crossbows
Reply #5 - Nov 3rd, 2007 at 5:46pm
 
I have no Idea. They have some nice plans both replica/tradtional and modern in thier files section.

Marc Adkins


Bikewer wrote on Nov 3rd, 2007 at 3:19pm:
Hehe-I belong to a dozen Yahoo groups, wonder why I didn't think there would be a crossbow-oriented one.....

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Re: More on crossbows
Reply #6 - Nov 5th, 2007 at 11:00pm
 
hey bikewer, i saw something about leaf spring crossbows, posted by user "hellfire," if not on this forum then on another.  his had a draw weight of something like 1000 lbs (he cocked it with a hydraulic press), and fired a chunk of re-bar, if I remember correctly...  (he cautioned people not to repeat it due to the extreme danger).   I'm sure that you're aiming for something a little lighter and more practical.  Don't know if he stacked the springs or not.  if you want i'll look for it, but tonight i'm a little busy.
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paracord sling tutorial thread: http://slinging.org/forum/YaBB.pl?num=1196026630
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Bikewer
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Re: More on crossbows
Reply #7 - Nov 9th, 2007 at 9:54pm
 
According to Payne-Gallwey's book, some Medieval crossbows actually had bows with similar draw-weights, but you needed a big windlass to draw them, and a very sturdy mechanism!

I may just break down and buy one of Alchem's fine prods.  About 60 bucks, and you can get them in any draw weight you want.   The "Crossbow" yahoo group has an article from a 1940 (!) issue of Popular Mechanics by a guy who built a leaf-spring crossbow, but the illustration looks like a very light spring compared to most you see these days.

When I was in the army, back in the 60s, I remember seeing a Jeep leaf-spring assembly that looked like it might furnish a useful spring.  I imagine lots of smaller cars might work.
The problem with these springs is that they are not set up to bend progressively like a prod or bow.  They are pretty much a straight piece of stock. 
So, in order to do it right, you'd have to do a lot of grinding/machining, and then re-temper the whole thing.

Still tossing around the idea of a more powerful wooden bow; probably something backed with hickory.
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