My crossbow project

This is the test tiller, it is made from pine. Not the usual wood for a tiller, but it's the best I could find in my backyard (and a common wood in my country). I believe that I'll probably change it to more beautiful and suitable wood.

Cutting the stock:





Inserting the tickler:





The side plates with an extra inaccurate hole for the axle:







And finally, the assembled rough crossbow:


I forgot to take a picture how I assembled the irons I made for the prod, but I simply drew a hole for the welded nut, and screw the four screws to the tiller.

The crossbow spanned with a dowel playing as a bolt:

.

Well, I was eager to shoot it, finally, after a long time. I wanted to feel the power of the shot. So I took it outside (in the dark, I couldn't wait) and shot the dowel just to see if the crossbow works. This is the result:



It worked: the broken dowel indicated that the shot was good. The crossbow has enough power to shoot the dowel and smash it against the yard date, few meters in front of me.
The second "evidence" for the shot was the broken string. It broke in the nock, reminding me what Dane wrote about strength in the nock.

Ferdinand, now I'm sure it's now strong enough ! You and Rizzar are right, I need to make a stronger one. Thinking of something like 12 times stronger the draw wieght, i.e. 600kg (1323 pounds).

Back to the working table...

The point for counting the strings strands always have to be the nock.
Otherwise if you count in the middle, you only have half the breaking strength in the nock (where the forces are very devastating).

Another very important point is rounding up and polishing the nocks. any small point and edgy area works like a cutting edge to your string.


Linen with over 40lbs sounds almost fantastic, great material.

I am enjoying to see your progress.

Rizzar

I was also going to mention refining your nocks- I can't see them that well in the photo so you may have done this already, but where the string lies and moves against the metal from rest to armed position should be as smooth, curved, and without edges as possible. Even a very dull edge will cut when there is enough force behind it, and you have plenty of force working there. I might also reccomend adding padding between the steel and string, like thin leather. Some add a leather tube around their string end loop, I wrap the nock ends then put the string over, because that way the string is still visible so I can check it periodically . Either way, you could eliminate string wear from friction against the nock from the equation and concentrate on getting your string strength where it should be.
Gnome

Rizzar and Gnome,
I was failing to see that point... That's how it is, you learn all the time . I think I polished the nocks pretty good but didn't made them round enough. I'm starting to think that the shape of the nocks causes a lot of stress on the side as you can see from the side profile drawing:



Maybe they are too width - 20mm (25/32 inch)...
I think I'll take your advice Gnome, and pad the nock with leather or something else. And maybe make them more rounded.

I'm really glad to know that you are enjoying my progress, Rizzar. I'm also glade to read your comments, both you and Gnome and everybody else who gives feedback. Cheers!

Sorry about the broken string, ZigiMan. Far worse could have transpired, and I think you can never, ever have too strong a string, all things considered and factoring in that performance may suffer with too fat a string. But I'd rather loose a few FPS bolt speed then end up in the ER or have my weapon destroyed.
I was just look at specs for Fastflight, a newer bow string material. It has a breaking strength of about 100 pounds per strand, so if you made a string from 100 strands of this stuff, you will have a string that fails at 10,000 pounds. That is a lot! Even halved at the nock points, you have 5,000 pounds of breakage strength. Fastflight is an expensive material, and you do have to buy special serving material, since the stuff is very slippery, but it may be worth the extra money. It is also I believe smaller in diameter per strand, so you can add more material and still have a thinner string than with Dacron B50 or linen.

Oh, and when you can, get some hardwood for your tiller! I wonder if some sort of palm would work, since it is a local tree where you live. I have seen bows made from palm, and it may look really handsome.
Dane

Dane, I think you are right. It's better to have strong string then breaking the crossbow or get hurt. Fastflight might be good material but probably I will stay with linen in order to keep the medieval look. But I will keep that in mind for future modern builds. For those, I will want to use more modern and thinner string. I will surely get a better hardwood for the tiller, this one is just an experimental one. Tell you the truth, I never heard of using Palm as wood material. From past looking on Palm stock I believe it doesn't seems suitable for tiller. Thanks for the tips!

ZigiMan

Cuts of old Coconut palm trunks are pretty hard - similar to mahogany. Trees that were planted for coconut crop production and have gotten too old to produce fruit are often just ground up as trash, but sometimes are cut into planks for timber. Likewise Black Palm, a native of Latin America; but with it, only the outer few inches of the trunk are hard, the inner core is soft.

ZigiMan wrote:

It worked: the broken dowel indicated that the shot was good. The crossbow has enough power to shoot the dowel and smash it against the yard date, few meters in front of me.
The second "evidence" for the shot was the broken string.

How heavy is that dowel?
If you shoot too light bolt with a massive bow you are guaranteed to break strings. As you are technically dry-firing the bow.

Zigi,

Mr. Flintstone makes an excellent point there. If the energy stored in the bow doesn't get used up doing something useful there is bound to be trouble.

But, that doesn't mean the string loops and the bow nocks don't need attention.

In addition to rounding the "pins" of the nocks, you should also consider the "shoulders". While the pins can be made quite round and still have enough strength to do their job, the shoulders of this bow are always going to be sort of narrow. This may be a source of continued trouble. A hard leather "washer" placed over the pins will pad and effectively broaden the shoulders. I have used this trick before on a ballistrino, and had good luck with it.

Mac

mac wrote:Zigi,

Mr. Flintstone makes an excellent point there. If the energy stored in the bow doesn't get used up doing something useful there is bound to be trouble.

But, that doesn't mean the string loops and the bow nocks don't need attention.

In addition to rounding the "pins" of the nocks, you should also consider the "shoulders". While the pins can be made quite round and still have enough strength to do their job, the shoulders of this bow are always going to be sort of narrow. This may be a source of continued trouble. A hard leather "washer" placed over the pins will pad and effectively broaden the shoulders. I have used this trick before on a ballistrino, and had good luck with it.

Mac

Good advice!! I did that on my first bow and the last one, same design nocks as u have, heavy jute cloth or thick raw leather will decrease the wear on the loops.
Maybe the string whas a little short to? To much brace? Good luck making that second string, use lots of wax!

Hey guys,
Thanks for the feedbacks!
Been away lately... holidays (Passover)...
I've noticed that I got a Techno Weeny rank Thanks! (I've always wondered how you get those ranks...and still wondering)

kenh wrote:Cuts of old Coconut palm trunks are pretty hard - similar to mahogany.
Trees that were planted for coconut crop production and have gotten too
old to produce fruit are often just ground up as trash, but sometimes
are cut into planks for timber. Likewise Black Palm, a native of Latin
America; but with it, only the outer few inches of the trunk are hard,
the inner core is soft

kenh, I don't think we have Coconut or Black Palm hear... Maybe only for beauty or in botanic gardens but for sure not in plantations... But I believe there won't be a problem buying one of the common woods in use for tiller.

Nerd Flintstone wrote:How heavy is that dowel?
If you shoot too light bolt with a massive bow you are guaranteed to break strings. As you are technically dry-firing the bow.

Nerd, In my rough estimation it's about 30-50 grams, so you can say it's weight almost nothing... So maybe that was one of the reasons for the break.

Mac wrote:Zigi,

Mr. Flintstone makes an excellent point there. If the
energy stored in the bow doesn't get used up doing something useful
there is bound to be trouble.

But, that doesn't mean the string loops and the bow nocks don't need attention.

In
addition to rounding the "pins" of the nocks, you should also consider
the "shoulders". While the pins can be made quite round and still have
enough strength to do their job, the shoulders of this bow are always
going to be sort of narrow. This may be a source of continued trouble. A
hard leather "washer" placed over the pins will pad and effectively
broaden the shoulders. I have used this trick before on a ballistrino,
and had good luck with it.

Mac, That seems like a good supplement for the nock. I think I'll file the edges a little bit more, make a stronger string and add a leather washer as you advised. If that's fail, I'll round the pins a little bit more.

ferdinand wrote:Good advice!! I did that on my first bow and the last one, same design
nocks as u have, heavy jute cloth or thick raw leather will decrease the
wear on the loops.
Maybe the string whas a little short to? To much brace? Good luck making that second string, use lots of wax!

ferdinand, I think the string was in the right size. In the first string I've mad, I followed the the common size of one inch shorter then the nock-to-nock distance but it seems very short with high brace height. Then I made shorter one, and another one shorter until I got to the right size and brace height. Thanks for the good luck! and now that I got bee was candles can wax it well.


Thank you all again for the comments and advices!

ZigiMan

p.s. Speaking of weight, I always saw here that when people writing about the
weight of the bolt they use Grain. If I understand correctly, it's an
old use measurement. Or am I wrong? I'll be glade to know more about it.
I also couldn't find a way to convert it.
And what should be the weight of a bolt for a 60kg (110pound) prod?

1 Grain = 0.06479891 grams

The weight of a bolt, I understand, should be 1/12th of the MASS of the prod, not it's draw weight.

Happy Passover, by the way. The other day, I made a batch of knishes. We are not Jewish, but they are sooo good. You get the various new ranks by the number of posts you have done. I think so, anyway.

kenh wrote:1 Grain = 0.06479891 grams

The weight of a bolt, I understand, should be 1/12th of the MASS of the prod, not it's draw weight.

Thanks, kenh! I wonder why the weight should be relative to the mass of the prod, rather then to the draw weight...

stoneagebowyer wrote:Happy Passover, by the way. The other day, I made a batch of knishes. We
are not Jewish, but they are sooo good. You get the various new ranks
by the number of posts you have done. I think so, anyway.

Cheers Dane Tell you the truth, I never knew Knish before... It seems that there are Jewish dishes that are not so common and well known in Israel and the Knish is one of them. It looks delicious! Well, I learn new things almost everyday

Has to do with the amount of potential energy from the cocked prod which is transformed into kinetic energy in the bolt as the crossbow is fired. If the bolt is too light, too much energy goes into the prod, not the bolt, and the prod can be damaged by the 'overflow'. If the bolt is too heavy it simply goes slower than optimum.

Cheers Dane Tell you the truth, I never knew Knish before... It seems that there are Jewish dishes that are not so common and well known in Israel and the Knish is one of them. It looks delicious! Well, I learn new things almost everyday [/quote]

The knish seems to have traveled and evolved from Western to Eastern Europe and then across to the US in the early part of the 20th century with various Jewish populations moving around, and is very much (I think), a New York thing. I grew up with many Jewish friends in Los Angeles, but had never heard of the Knish until fairly recently on a trip to Manhattan. My wife grew up enjoying them, and she is Puerto Rican. So go figure

The knish is a dish of Eastern European origin - Poland, Hungary, the Ukraine, Belarus, Romania, Bulgaria, etc. which was adopted by the Jewish diaspora up into the 1940s. It was brought to America in the late 1890s early 1900s by Eastern European immigrants (not necessarily Jewish). 'Knish' is a Yiddish word derived from the Russo/Ukrainian word Книш (knyush).

...things you learn as a gourmet Personal Chef!

It's seems that you both are the woman's dream of how a man should be - one that know how to build and use weapons and also can cook!
Never thought I will be discussing food in this forum...

Wait till you see my recipe for Lamb Kebab al Quarrel

Zigi, being able to cook is a great skill for any guy. Women love men who can find their way around the kitchen. What made me start to learn was that a girlfriend was moving into my apartment and I realized that I couldn't afford to eat out every night, and my own diet or junk food and so on would not impress her.

Moms cooking got me hooked! I love to cook! I think if u are a creative person like anyone of us here it is just another challenge! Creating beautifull things like crossbows is probably just one of many things we do!?
If i speak for myself:
I have a old 73' ford taunus i love to ride and tinker on.
I ride a bike, kawasaki drifter(cant afford a vintageindian!!)
I do some painting sometimes.
Just build a forge and am discovering this art!
And it goes on and on haha
Dont think i am that different from all of u, right?!

Ken, that seems like a true crossbow hunter dish!

Well Dane, it's part of the holy trinity for woman: chef at home, warrior outside and lover in the bedroom!

I couldn't agree with you more Ferdinand, it all about creating... the urge to understand and make things with your hands, whether it's crossbow or food... Zen and the art of building a crossbow

Built new bases for the string jig since the old ones (on the left) weren't firm enough, causing the poles to bend when there is too much tension.



Had a hard time making the new thick string. Took me time to realize that few factors were influencing the length of my string: Stretching the threads too much shorten the length by 1cm, and the loop of each nock short the string by 1/2cm and finally, the bend of the loop while resting above the nock made it short by another 1/2cm. Making long story short, the string was too short.



Only in the third string I took all of the above into consideration and make a proper size string. This one is three times thicker then the one that was broke.



Filled the edges of the nocks a little bit more. In order to secure the week points of the nocks, preventing them from breaking, I followed Mac's advice and added leather strips.



Tested the shoot with what I had as a heavy projectile (in order not to dry-fire) - a long aluminum round bar, and it worked pretty good.
Now it's time to build a bolt.

ZigiMan

Forged my first bodkin:





Tested the bolt (without fletching yet). Worked very nice. The shot was taken from a distance of 10 meter (11 yard).



Took a thin plastic sheet I found at a stationery shop.



Cut the fletchings:



After making a slot I glued them with 5 minutes glue.