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Material for Homemade


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#1 AndyF

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Posted 27 November 2009 - 07:54 AM

I'm building a steel bow from scratch. I haven't decided on weight, but it will be 142 thru to 438lb. 438 with a scope would be awesome but bolts are "seldom retrieved intact".

Anyone know where I can get 6 cord flax and bow steel?. Depending on weight, plan calls for car spring of thickness: 3/16" initial set 2.25", 7/32 initial set 2, 1/4 initial set 2. Length of steel 23"

Respectfully, spring to release, 11.5, 10.5, 10.5"

It'll cost me 3 hacksaw blades to cut the springs, but I'd prefer to shop for the steel rather than search scrapyards.

Any help would be appreciated

Thanks.

Andy

#2 cingold

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Posted 27 November 2009 - 08:41 AM

been there, done that and still experimenting...

1) Material
no need for buying spring steel, automotive leaf springs will work as fine and are way cheaper. Remember to cool the sawblade and not overheat the steel when cuttingor you have annealed and weak spots (2)

2) Metal treatment
as long as you don't know how to heat treat metal, don't go that road. Especially with these high poundage prods. Annealing and quenching or hardening is a science itself, get help on that or leave it be for obvious reasons (3)

3) Safety
if the metal hasn't been treated properly (2) the prod can and most likely will break. If it does, the metal splinters will become schrapnels. ALWAYS wrap something around the prod such as leather, shrinking tube etc to dampen the shrapnels. Your safety comes first, your eyesight cannot be restored!

4) Shooting
well, cocking ain't easy, I tell you. And shooting isn't as smooth as with a modern crossbow. These high poundage bows were used to propel a heavy but short quarrel fast enough to penetrate horsemen and light infantry armor over distances up to 600 yards. Hunting? Naa, I don't think so, not with 400lbs (check laws about crossbow hunting in your state).

5) Supplier
these guys supply you with a properly treated prod for a reasonable price. I doubt you can manufacture one at home for less...

http://www.alcheminc.com/crossbow.html

I am now concentrating on fiberglass laminated limbs. They have a positive and smooth "cast" unlike metal, they are not as affected by ambient temperature as metal, they are as easy and cheap to produce as metal, they can be shaped into whatever recurve you want much easier. And remember, poundage alone doesn't give speed, a 400lbs bow with a powerstroke of only a few inches won't shoot better than a 180lbs with 13 inch powerstroke. For hunting purpose a definitive no-go. Reenactment of historical battles, ya why not.

Anything else, just ask. There are some other resources I can send you to, most of them told me the above in more or less the same words :thumbsup:

Have fun

Edited by cingold, 27 November 2009 - 08:47 AM.


#3 AndyF

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Posted 27 November 2009 - 01:47 PM

cingold:

Thanks for the info.

Metal treatment - I'm working from a Pop Mechanics manual circa 50's. They don't mention anything about breakage. Maybe they figured it's a necessary hazard seeing what we have to work with the war just being over and scarcity of material.

Good idea on the covering, never thought of that. :) I can image a guy can lose some teeth if it ever let go. :(

I am prepared to watch for leaf wear from lower and upper spring friction that leaves gouges and reject them. Also a fatigue would have set in affecting poundage but that would be balanced on both sides I guess. I'd still buy them new if I can.

Good idea on the fiberglass. Ever consider that new black composite stuff they use on chopper and plane blades?. I'm going to use fiberglass in the same process to give me stronger flexing in gale force winds on my 10' wind generator props I'll make one day.

Too bad all the trees are practically gone to disease but if you can find some dry rock elm planks I'd include some slivers of that in the layering with the lemon wood. (Not sure if you can get ewe wood on this continent). Elm is one heck of a tough wood.

They show plans for the bolts which are 5/16 birch X 13" w/ target points. I'm going to try 1/4 in X 12 aluminum to see what variation I get on impact. It should be greater for the lighter projectile. This would call for more of a "V"ed track than usual has I don't want any rocking in the groove on initial release for this light a bolt, (or do we now have a dart. :thumbsup:) Maybe a removable slot can be rabbeted for different bolts cut with a single dovetail bit.

Thanks again. Pics when I start.

Andy

#4 cingold

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Posted 27 November 2009 - 02:27 PM

Bo-Tuff glass, pre tapered and easy to glue up. Bingham Projects, 3 Rivers Archery etc all supply Bo-Tuff and other glass ready for bow/limb making. It's hard to get the proper stuff here in RSA but it's worth it.

You might want to sign up for another Crossbow Nation members document archive. Go to http://www.ballestaperu.com/ (there should be an option for english) and sign up, then search for the download section. Many documents about crossbows and construction plans, I think I found Paynes standard on crossbows there too. Especially a document called construccionballestayotros.pdf should be of interest for you, the author covers wood, fiberglass and steel limb plus several different stocks (in english).

Are you working with Bertram Brownolds Auto-Spring Crossbow manual?

Edited by cingold, 27 November 2009 - 02:30 PM.


#5 AndyF

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Posted 28 November 2009 - 11:18 AM

cingold:

You guys are sure informed on the latest!. Looks like I can forget most of the material in my plan and use the latest technology.

I've got a 12 volume Do-it-Yourself Popular Mechanics edition. These were popular years back. Shows how to make broadpoints and the tips out of spent cartridge casings. It even has a squirrel knocker point for the small game guy.

They show plans for a wood crossbow of various strengths up to 80lbs.

What I like about PM plans is they are all contributed, so the prototypes have all passed grade and the glitches are noted and passed on. Nothing is theoretical.

The 438lb steel is legit and calls for 82 loops of 6 strand flax made on a 23" form also supplied. I'd be tempted to pay someone to cock it, and stand back when the trigger is pulled. :rolleyes:

Thanks for the info. This is an excellent site.

Andy

#6 cingold

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Posted 28 November 2009 - 02:34 PM

The 438lb steel is legit and calls for 82 loops of 6 strand flax made on a 23" form also supplied. I'd be tempted to pay someone to cock it, and stand back when the trigger is pulled. :D

Andy


If you want to be historically correct. If performance, durability and safety are issues rather go Dacron or other modern string material. But with a Dacron string that has a breaking strain of 10lbs you are facing 176 strains to ensure a safe shooting out of a 438lbs bow :D Get more info on that, there are some great stringbuilders here with loads of tips and the latest breaking strain development news... It's easier to reserve the string too btw, that loop center serving thingy on medieval crossbows would drive me crazy...

Again, try to get the manual I mentioned above, there is some great info in too. I have some of the popular mechanics, most of it would for sure work but isn't all too great at the end. Their crossbows won't last long IMO and safety is an issue for me after some accidents experimenting with gun cotton etc :D Tinnitus :bigear::)

#7 pdislow

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Posted 28 November 2009 - 09:34 PM

There are several fibers now that are considerably stronger than dacron. I do not have a clue as to how they would perform as a bow string, but spectra, plasma, and maybe vectran should be around 3 times stronger than dacron. Good luck and be safe! phil

#8 cingold

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Posted 29 November 2009 - 03:41 AM

Andy
I gave it another thought and want to throw in a fourth prod material, mostly underestimated.
I'm currently working on asiatic composite bows, at least I try to learn the basics. They are made of a wood core, horn belly (unlike american flatbows, there horn or glass would be the backing) and sinew backing. I know from certain sources that the ancient chinese, turks and persians used horn composite limbs that have been as strong as steel prods.
Positive aspects include easy shaping, easy adjusting draw weights up to high poundages, you're historically correct if you're a traditionalist, it's all natural material (carbon footprint, environmental friendly :)), the limbs are significantly lighter than steel (which is one of the key factors) and the safety of course.
Negative aspects are the time spent to research and learn about construction, the material can be difficult to obtain (waterbuffalo horn from the Philippines, fish [sturgeon] glue from Germany, sinew from a butcher or taxidermist near you etc), glue and sinew need to dry for at least 18-24 months before the bow can be stringed and used, and the tillering might be a bit difficult at first. And the hide or fish glue isn't water resistant, a very humid environment will break down the adhesive ability and sinew backing.

But they are very appealing, an exhibition bow made this way for sure is an eye-catcher. The Traditional Bowyer's Bible might be a good start to research, and a guy named John McPherson is IMHO one of the hornbow gurus :)

Let us know your progress

Edited by cingold, 29 November 2009 - 03:44 AM.


#9 cingold

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Posted 05 December 2009 - 05:57 PM

I've found very neat drawings with measurments in milimeter for a medieval crossbow with metal prod. PM me your email address, I'll send it to you for further research