Step 7: Making the Springs

Next we'll make the nylon string springs.  

Cut your 24ft of para-cord into 12ft lengths. 

To form the springs, you will wrap the strands of para-cord around a jig like the one shown in Picture 1 .  Using any scrap board (or your workbench), nail 2 finish nails exactly 7 inches apart.  Removing the nail heads will make it easier to slide the string off after wrapping.

I recommend doing the next steps with one length of para-cord at a time to keep the strands from falling apart.   Remove outer casing from your para-cord.  Save this for the next step.  My cord had 4 strands inside, yours may be different.  If there are more than 4 strands, you will have to shorten the length or the completed spring will not fit in the frame.  You will have to experiment a bit to find the best fit.  Be sure to keep your strands together during the next steps.

Holding all strands together, wrap the length around the jig as many full rotations as you can.  You will have a few inches left over after the last full rotation.  Cut off this extra.  Use one strand as your threading string.  See Pictures 2 & 3.   Loop the threading string through all layers of string at one nail and tie securely.  This will ensure your spring strands stay together and will make threading the spring through the holes in the frame much simpler. 
It's also a great way to keep the strings separated so you can get the spring tighteners and arms into place.

Repeat for the other 12ft length of para-cord.

Using the threading strings, hang your springs somewhere out of the way where the strands will not tangle.  We will add the tighteners, springs, and bow limbs in the next step.
<p>Your attempt to explain the construction of the torsion springs (Step 7) is rather pathetic. It does not offer a clear explanation of how/where to begin or end the spring cords. Do the ends hang loose? That would unravel the spring. It offers little assistance to the casual reader. Please consider adding more detail.</p>
Ah. I appreciate your absolute abandonment of the art of disagreeing, preferring instead to resort to vulgar, childish name calling. Thank you, sincerely, for adding absolutely nothing to the conversation.
This is awesome I'm sooooo adapting this design into a longbow size design
<p>I love reading all these inspired projects and seeing the (mostly)supportive comments. I feel frustrated that I have a garage full of tools and wood and other supplies and no one to utilize them. Even I have a hard time getting started because there's not good organization of everything. My family would like me to just get a dumpster but I have old heart pine 2x4s and beams and bolts and hardware just aching to be turned into something in the right hands. I have tried offering a rental house I own for free to a local hackerspace but after leaving me hanging for months they rented a bigger space. I just want to expose kids and adults to doing and making that maybe don't have the place or resources on their own. Any thoughts on how to connect? ps. Organization is not my strongest suit.</p>
<p>just asking, why the lever trigger instead of a roller nut?</p>
<p>This is brilliant, possibly one of the best things i have ever seen. I have tried building my own crossbows before but i could never source an effective prod, well good enough to hunt with anyway. This is the ideal solution to my problem, how powerful is the crossbow?</p>
Hi dbull <br> I'm in the process of making the scorpion , having trouble downloading the stock plans could you give the length and with of the stock and barrel . Thanks Ron
This is SlenderMan.
Very cool but this is not a crossbow, it is a Roman Scorpion. A Scorpion uses rope torsion with rigid arms while a crossbow uses arms that flex when pulled back. See attached pictures. (first is a scorpion and second is a crossbow) <br>Nice work anyway
While we're getting all technical the projectiles crossbows shoot are generally referred to as bolts, not arrows. A scorpio is a type of a crossbow too so the original author was technically correct. Actual scorpios all have mount stands. <br> <br>Great article by the way.
he said that in the title
Yes he changed it after I informed him.
I didn't originally-I added that after I verified this comment was correct. I didn't want to totally change my title and confuse people. thanks though!
I stand corrected, sir! I actually modeled my weapon off of pictures of ancient Roman weapons I have seen, but the books I had didn't say what they were called. Thanks for the info and the compliment.
And I just looked at the instructable again and you have a very cool trigger design! I build a giant version of this a few months ago (about 10 feet long) at my friends house but we never could figure out how to make a trigger...Maybe ill try to build one like this!
that sounds awesome. Just shoot me a message if you need any design pointers. The more I use this one, I'm sure I will come up with some tweaks to the design. I would be happy to lend a hand
Sounds good, thanks.
Okay no problem
im going to make this but a dumbed down version as im a beginner.
amazing! the trigger system helped me sooo much, iv been wanting to build a cross bow for ages, but all the triggers i could find where either to hard for me to build, or required tools/metals that i didnt have, thought i wont be using the bow that yours has, (im attaching an old fiberglass bow) everything else is awsome!!!!! thank you sooooooooooo much!!!!!!!!!!!!!!!!!!!!!! =)
that's amazing!!<br><br>unfortunately, i never have any money and i don't have the tools. what i might do though, is make it out of plastic, metal, and sweet gum saplings... thats about all that i have access to!
i built one of thes out of wood pallets
Awesome. I've been wanting to make one of these ever since a built a little table top onager a couple years back. I'm glad to see other people think like me. this is deffinetly getting bumped up in my to do list.
I used your Instructable for the basis of this:<a href="http://www.instructables.com/files/deriv/F7H/R17Q/GTGZI7ZN/F7HR17QGTGZI7ZN.MEDIUM.jpg">http://www.instructables.com/files/deriv/F7H/R17Q/GTGZI7ZN/F7HR17QGTGZI7ZN.MEDIUM.jpg </a><br> I was too lazy to make the rifle-stock thing you've got going on, but it is pretty much functional and a great use of torsion. However, I don't think it could kill any animals, and I can't possibly wind it any tighter or it will break. Do decent arrows make a significant difference?<br>
Can it kill game?
Nicee. I made one of these once but it was around 10 feet long and I had to use steel for the arms because the 2&quot;x2&quot;x4' pieces I was originally using splintered!
sweet. 5/5<br>sooo trying this but made out of steel and using metal springs <br>this is so good thnks heaps
Hunting with miniature siege weapons? Sounds like a good time.
Do you think the size could be doubled without making the top and bottom pieces thicker? Or do you think everything should be doubled?
i was thinking would you get more range if you made the distance between the frame and trigger longer, do you think the arms could stretch back more with out stressing the frame? you seem to have alot of overhang in the arrow
awesome instructable! i have been wanting to build a scorpion bow for a few years but never found good instructions and the fact that this one is hand held makes it even better. the only problem im having is finding out the length of the trigger and release mechanism if you or anyone can help clear that up it would be great
I'm glad you are able to use my Instructable. I will take some measurements and get back to you as soon as I can.
thank you
this is pure epic win!
i wish i had thought of tighteners like yours when i made my ballista for my physics class, i only wrapped my rope around the entire thing and twisted the arm until it was too tight to slip the peg on the outside back in. needed to use a car jack to get the clearance needed to put it back together
Yeah, I went through a few designs before thinking of the tighteners...I wanted to avoid the problem you had.
can you use bigger rope
are you asking about the strings for the springs or the rope that pulls the limbs back?
great project. Currently working on my own crossbow, i know what you mean about the red oak, pine has been breaking alot.
If you just want it to show off, then by all means use pine. However, pine just will not hold up to the forces exerted during firing if you actually want to shoot it. Good luck with your project!
Pretty good instructable. Only part that was lacking were drawings (could have been cleaner) but other than that, i'm going to base one of these off your design. Thanks for sharing, i look forward to seeing more from you.
I also wish I could have had the drawings turn out better, hopefully I will work the bugs out of that component of the process before I do any more 'ibles. thanks
this is an amazing project. although at the moment i have no free time (high school senior :/) i will definetely build one of these. love the design. excellent workmanship and simple directions. the only thing i might suggest is making the trigger mechanism out of metal. wood is slightly weak for something like that. since this is definetly a dangerous weapon, i might also suggest making a safety. <br>one thing i might also recomend is putting pads on the forward upright pins to reduce shock when the limbs snap forward. other things you might think of: put a forward grip so you dont have your fingers so close to the string (you can lose fingers, or at the least break them), paint it, maybe work out a sight. Don't take my criticisms the wrong way it is all purely constructive. LOVE THIS PROJECT!!!
Thanks for the love man, no hard feelings over the suggestions. I made this project just exactly as I wanted it to be (as much wood as possible) and it has worked great for me. Your suggestions are good ones, and would make your project unique. I recommend writing up an 'ible yourself. This took me about 10 days total, working a few hours each day after work.
Thanks man!
You are welcome. Today is the last votation day, <a href="http://www.instructables.com/member/rimar2000/">I have two projects too</a>...<br> <br> BTW, for the crossbow, did you try using latex tube instead of paracord? I think It will enhance a bit.
I didn't think of that, but I may try it. The more I use it, I am sure I will be thinking of tweaks to the design. thanks.<br>Your spinning top is cool, I wish I had a lathe, it is one of the few tools I don't have in my shop.

About This Instructable


319 favorites


Bio: Hi, I'm Dave and I like to party.... No, really, I'm just a guy who likes to do guy stuff...camping, canoeing, making ... More »
More by dbull: Wooden Scorpion
Add instructable to: