Spring powered Crossbow 

If you rotated the wheels by 90 degrees so they remain flush against the body, you might be able to make a really powerful bow that meaures incredibly thin on width. I imagine this would make it more mobile and easier to carry, especially around corners and low arches. I know folding limbs exist on a crossbow, and crossbows are meant for hunting so you'll typically be out in the woods and not in either of those 2 situations very often, but the idea of a long and skinny crossbow seems pretty novel to me.

good design. i would recommend putting safety wires through the springs though. that way if the springs break they don't go flying everywhere and hit you in the face. i used to work on garage doors and that was a problem with some of the older systems that home owners would install. its a good idea for anything that uses extension springs

That's really cool. I like how simple the powerstroke extension method is!

One advantage of springs is that you that you really can extend your draw length and weight and also put them in Series or Parallel. So maybe having 4 springs that are lighter but have a longer draw length might be better. Maybe. Idk. It is a very impressive design. Really awesome design. You could probably turn into a slingshot too.

Hello, I tried to modify your construction a little by not using round pulleys on the string, but in the shape of a three-quarter ellipse with a ramp from a smaller to a larger diameter, it made stretching the string a lot easier, since the largest diameter of the pulley is actually at the point when the spring is "free" " is basically in zero action and as we pull the string further, the diameter decreases and the closer we get to the maximum tension of the coil spring, the diameter of the pulley for the string decreases and thus we develop less force for stretching, but at the same time it simplifies the start of the string, the greatest force it is actually on the smallest diameter of the pulley and as the diameter increases the power decreases, but the speed of the string increases and so does the arrow, I use one spring not two, and it is built into the duralumin body of the crossbow, actually it is not one, but two, they are pushed in itself, it is softer on the inside and harder on the outside, in addition, they are longer and for better balance the end of the springs is attached to the pin before the end of the stock, while the trigger mechanism is designed around the driving coil springs, I charge with a lever that pulls the string up to above the spring and is integrated in the crossbow frame, I also have an industrially produced hunting crossbow with a reverse reed and elliptical pulleys, I must state that the home-made spring crossbow has significantly more power, I don't know exactly how much, but the arrow shoots at a speed of 508 m/s, it is absolutely accurate at 30 meters, after 40 meters already the ballistic curve works and the arrow goes down, but the arrow hits the oak tree 2 cm deep at 70 m, which I think is a respectable force, at 10 m it pierces a 5 cm thick spruce board and the arrow simply goes through the whole thing and flies even further, at 20 m it goes through straw I aim for a third of the length. I'm currently dealing with loading from a suspended arrow magazine, I'm mainly interested in ensuring that the mechanics fit the arrow accurately into the arrow holder and always in the same way, both deep and sideways, and the accuracy of shooting depends on that, there are still malfunctions, but it's already going well in 90 percent of cases, you can put it on the same way, but it is only about the correct clearance in the arrow feeder and the pressure of the holder, the repetition speed is about 6 seconds, which I think is good for a crossbow. Thanks for the inspiration, I would never have started this even though I know the principle of course if I hadn't seen it from you. good luck :D

I don't know if you are aware, but what you've built is basically a crossbow version of a type of speargun called a "roller gun". They are by no means a new invention, I think the first one came around in the '60s but for some reason, they disappeared until maybe 10 years ago or so, and by far most of the ones I saw back in the days before I started building my own, were homemade guns. These days they are manufactured by a couple of companies I think, or you can get drop-in kits to modify your _(some)_ traditional speargun(s), to a roller. One of the problems with traditional spearguns is that they don't use the full length of the stock, they generally only transfer energy to the spear over some 2/3s of the full length, and when they do they go from transferring 100% of the energy to 0%, meaning that the energy curve is rapidly declining. Then you can add another set of bands, and that _does_ give you a decent amount of extra energy, but it _also_ increases the already rather substantial recoil. Roller guns however, never let the bands contract to 0%, because the bands are either pre-stretched or as in the case of my first gun, also boosted after loading with 2 sets of booster bands. So, energy transference-wise, they go from some 150% or more down to maybe 50% at the point of release, I haven't done the exact math on it, but it's in the ballpark. As for recoil, I'd say a roller only has about 60% the recoil of a similar length traditional speargun. I would recommend you look into this type of speargun, clearly you are a skilled craftsman, so it shouldn't be too hard for someone like you to adapt a speargun roller system to suit your needs, or at the very least reuse the technology for something besides hunting fish underwater. I reckon you could easily shave those wheels down to around 35-40mm in diameter, and thus get a much sleeker result, on a roller gun the wheels are upright, the pull comes from the underside as the spear is pulled by the "wishbone" on the upper side of the wheels. On a roller gun we need a couple of string risers at the end of the stock because our spears aren't pulled from the end, but from a groove or "shark fin" located a bit up from the back end of the shaft, where it goes into the trigger system, but you won't have to worry about that. Most traditional spearguns around my part of the world are either what we call "75'ers" or "90's" as that's the band pull measured in cm, the shorter ones are primarily for hunting around structures, whereas the longer ones are better for open water. My main gun is a bit shorter than a "75", but shoots like a "110", so there is a lot of length to be saved with a roller gun design. One of the greatest features, in my mind at least, is that you can add several boosters without increasing recoil significantly. Anyway, if you decide to have a go at new crossbow, feel free to ask anything, I've built a bit of this and a bit of that over the years, and I might be able to answer some of your questions.

Thank you for the innovative inventing of a spring crossbow, I love archery.

Sweet design mate! I really liked your draw length multiplication, simple yet effective. It also looks like it shoots smoothly with very little hand shock, well done!

Very nice proof of concept. I think there are many more mechanical advantages that can be applied to maximize the usefulness of such a small bow. The fact that you got it to the point it currently is with such a small overall size just leaves that much more room with which to add upgrades/improvements.

This man just discovered how to bullpup a crossbow, i love it

You should try mounting the pulleys vertically, to make the bow narrower

Iam impressed, looking forward to whatever improvements you make for the next one.

Man this is awesome. You straight up made a crossbow from the game Kenshi and I'm totally loving it.

Very good design! I'm a little bit of a fan of the idea of using metall springs as parts of crossbows, and so it's very nice to see that you have so many new ideas to enrich the design of these devices! Thumbs up and subscription added. ;-)

Im so impressed. You could put those roles anywhere. Good job!!!

Welcome my friend, I like the design and the power too. I am also considering building a spring gun but I don't have a specific plan yet ..... The pistol grip and shoulder rest are good. I would add two things to the gun: -With a sight to shoot accurately at a distance. -I would put the springs in a thin-walled metal tube (say it looks good in a brass tube) to make it safer. if you touch the spring you can pinch your skin when shooting. The springs are close to your hand. Congratulations to.

That’s fantastic! My only complaint is when you gave an overview of the crossbow you didn’t say “let me show you it’s features” 😜🤣🤣🤣🤣

Well done! I think the principle is called Compound Gearing, very useful stuff.

Bruce here,I love what you’re doing keep going.

Very nice, good design which seems to work quite well. Keep the videos coming, thanks.

I'm glad he mentioned using a compound crossbow-like system. A smaller, compound wheel/pulley system could reduce the profile. Might even be able to fit all of it within the body of a crossbow

Great build , impressive if i had access to a workshop id make one of these

Impressive,excellent. A solid step forward.Kudos

As an Australian without ready access to Orangina, I'm furious! Furious that you would waste my favourite drink! But I do love the crossbow design. So I suppose I'll let it slide haha. Great job!

Hat's of to u. For inventing it. You'll make further improvements and fine tuning it as you use it more. 👍

Screams steampunk, the dwarves will definitely adopt this one for the mines

Awesome idea. Excellent work 👍

Very cool design I passed it on to a friend who's into Dungeon & Dragons so they can put it in a campaign!

Like. Looking forward to seeing you develop your system.

I would suggest adding some sort of lightweight casing for mechanisms. If something got caught in the wheels or springs when under operation you may get a danger of the operator getting debris in the eyes or face the mechanism. Alternatively a face guard, face shield or combination of a face shield and mechanism cover.

Ausgezeichnet!! I would not have guessed that any of those parts were 3d printed. It would be lovely to see a skeletonized 3d printed frame, too, if it would be strong enough. Very nice work!

Hello and welcome to the springshot channel.

Great work friend I made one long time ago reminds me of the spring bow aswell

A new JOERG SPRAVE is born, thanx God, finally. Tatsächlich hab ich auch viel über Federn nachgedacht, Klasse vor allem mit der Übersetzung, dass man praktisch den geringen Zugweg der Feder so beliebig verlängern kann. Auf die Idee muss man erstmal kommen, scheint mir das beste an der ganzen Sache. Weiter so

It genuinely looks like a fictional weapon from a video game. Well done.

WOW ! I had kind of the same idea but never did made it to work. It is very slim and I bet you could make it even more slim by stacking the cams. GOOD JOB ! 👍👍👍👍

I love that idea ❤ and there is not question it looks great!

wow, im very surprised that 3d printed parts can hold up to those forces, well done :3

Truly marvellous design.

Replace your coil springs with high grade nylon monofilament, extending right back in grooves to the back of the stock. It has over 140% original length yield strength and the highest energy storage per weight in tension of any common material. Run it directly to wind up spools directly on your throw wheels. If you offset the centre of rotation on the throw wheels and reduce friction by having them offset forward and unwind the throwstring directly at their rear, and preload the nylon tension cords, then you can easily achieve a constant force and acceleration over the whole throw of the Arrow. Then you will have a world leading crossbow in power and accuracy.

Absolutely beautiful

Really novel idea. You could probably use a toothed rack attached to one spring to drive two pinions and use those to drive the wheels, then you might be able to house only a single big spring inside the stock of the crossbow rather than two on the outside.

Very good, I like your design, thank you for sharing.

Could you tellus how much power and speed u get in "Joule and Feet Per Sec".? I have similiar project,but for slingshot not a crossbow. Thanks you

well done, looks like a great design.

In one of my undergrad journals from the early '90s I have a design for a spring powered crossbow very much like that, but a little more compact, but essentially the same. Never got around to making it though, too many other things to do.

nice design although i would add longer spring that go direct on two assymetrical egg shaped wheels and make them slightly smaller .... that would be insane

Fascinating, thanks for posting.

This is exceptional. I watch allot of self-made irregular crossbow concept videos and hence was expecting something that can tickle styrofoam. Instead, here is something that would stain Yogis underwear. It puts out enough energy. Next up. Gas pistons?

Very good work master!!!

Great choice of springs after the massive trend of backyard trampolines you can get such springs for free quite easily.

thank you for this tutorial, can you make another tutorial with new version of this tools ?!

Awesome project, I too am designing a spring powered bow with my son as one of his uni ideas, the latest designs have internal springs and vertical wheels, but I still like the traditional bow look, but want the adjustability of a spring, so have gone for a double actuated knuckle at the front, won't be as powerful, but as with you, it's an experiment Look forward to your MK3 version, will be very cool ; )

Cool demonstration

I think you should combine traditional design with the spring idea. Have the springs work at the end of the release to give the bolt extra umph.

This is genius. I have a couple of similar springs lying around and have been thinking of using four or more pulleys to increase the draw length and to possibly allow lighter arrows to be shot faster and therefore on a flatter trajectory. I think this system could achieve the same thing. I wouldn't have thought of doing it this way. Well done. I look forward to the next generation of this design. P.S. there is a video on RU-vid of a supersonic trebuchet. Do you think bows can be pushed to be supersonic?

You can actually get rid of the two wheels closest to the spring and connet the spring cord directly to the underside of the big wheel axles. Your springs would angle away from the weapon body by around 15° so won't look as cool, but it's simpler and it reduces friction just a little bit.

The only weakness of your design is the springs themselves. Great job.

Looking forward to the bullpup version…

I don't know how to make a xbow or slingbow draw over double my body weight, or close to it even. Can't seen to keep my foot on it using a rope, it's lifting me off the ground. Mine is just an angled step to step on. It would have looked weird with a stirrup. Are stirrups essential for beefy xbows? Like 300 pounds? I gave up struggling and went down to 6 bands from 8. Maybe I'm just not a spring chicken anymore? It is only 200-ish now, each band 32- 34.

Is there any reason you couldnt make the same design with stronger springs or were these just what you had on hand?

Very clever, well done

The best thing I've seen so far! One suggestion. I think it is possible to reduce the design to one spring and one lever.

Fantastic work! Is the draw length limited by the circumference of the wheels? Or do you allow the string to overlap on the wheels so you can have a large draw length without large wheels?

Very impressive, looks fun!

If you make your parts with 20% to 30% infill and lots of little holes on the surface, then you can paint them with resin which will soak in and make them very strong. Or if you make them very thin and then paint them with resin, and then dip them in graphite fiber (or baking soda), let them dry, then paint them in resin again and dip them in graphite fiber (or baking soda) again. Repeat that until they are as thick and strong as you need them.

I realy like the design. Looks great for Steam Punk!

@6:42 That apple be like "Crossbow bolt ain't sh!t now again! I said again!" little did we know that apple was in a doping scandal a year ago no wonder he took like a champ.

Do you have the original measurements from the video as they aren't mentioned here or on your website

Wow what a great design ... You Rock !!!

Allegedly music wire is the most efficient spring material. 90-95% efficient, compared to 80-90% of your average spring.

Three obvious things that can improve the system: use eccentric cams to let off the spring force - this will even the force and make steady the acceleration curve, promises up to 50% improvement when balanced correctly to the weight of the bolt; do not use extra passive rollers - I recon you lose up to 20% of energy in them just for the sake of springs moving in parallel to the stock; synchronize the string pulleys, 20-30% of energy loss here, the easiest is to use one spring and distribute it into two cams. With all of those you may practically double the energy. Further, the bolt weight must balance with the weight of the spring, roughly it should be equal to the weight of the spring divided by two roller ratios (because only half of the spring moves "on average"). You may improve the system even more by using an air spring, e.g. from the spear gun using a carbon fiber drive rod.

Those springs are kinda where the stabilizing hand goes on the forestock. One normal xbow maker uses wing shields halfway horizontal across the forestock to keep fingers from creeping up. I would suggest polished overlapping sleeves, two part where one slides into the other. You may not have seen that design executed due to perceived or actual danger/liability.

Great design, and good to see some fresh thinking. I wonder if a pneumatic spring might be a thing? It would take a bit of designing, but being able to change the draw weight by a pressure adjustment seems worthwhile.

it's not a Ravin R500 or a Ten Point Nitro 505, but you did a great job and in any case, I wouldn't want to find myself in the path of your arrows! congratulations, I think you have the potential to improve your product even further

It would be nice to see how the Crossbow performs when shot with more heavier or lighter bolts. My hypothesis would be that you could reach more Impact with heavier ones, due to the heavy moving parts.👍🏼

did you try something with a manipulated pneumatic cylinder?

That is a very nice looking crossbow, good job! I think this would look even more awesome when given a little bit of a steampunk / Victorian makeover, or to keep it German, Bavarian. By which I mean less plastic and more brass (for the gears and cover) and darker wood. Aber es sieht so wie es ist sehr schön aus!

Instead of using more powerful springs, move the existing ones back so they are more pretensioned, som you gain the additional force over a longer length of the draw. And like you said, change the shape of the wheels to adjust the force profile in different parts of the draw. Very cool!

Super réalisation, bravo et merci pour le partage !!!!!!!!!!!!!!!!!!

Very nice job! Now I want to build one!

This is amazing

I had a super similar idea back in 2006 after walking around and looking at some stuff that was available at a hardware store.

Fantastic, tried pausing but trying to get my head around the set up between the small wheels and the larger for your step up system. Any information appreciated.

A good design. But the following small ideas. Consider a double spring? a bigger spring with a smaller spring inside? It maight make the pulling faster. Did you consider making the big wheels excentric? Maybe faster.

how do you call this form factor? this very strong shape... :D

looks really good

Gave me some good inspirations great video and explanations!

You could make the wheels not circular but oval shape, so the lever increases the ratio to the end of the stroke

It's so creative, I really like it

ALWAYS LOVED CROSS BOWS, PRICE

What if you use just one spring, with a short arrow in the midle ?

Would oval wheels allow for an easier cocking experience?

Хорошая работа 👍

Can you make it more compact like the HUNT: showdown one? It's a video game (of course i know it's not a functional design)

Nice concept. Now a motor and magazine for 'fast' automatic shooting ;O)

Есть ли идеи по модернизации данной конструкции, а именно: эксцентриковые блоки и система булпап? Ещё можно попробовать скомпоновать блоки вертикально, что сузит ширину, но усложнит конструкцию. При испытании на скорость использовался тяжёлый 30 граммовый болт, что выдало результат в среднем 40 м/с. Если использовать более лёгкий болт в пределах 15-20 граммов, то насколько увеличивается скорость в м/с? И ещё, способна ли выдержать конструкция арбалета выстрелы шариками, так как они могут быть слишком лёгкими, и критично ли это для надёжности? Есть ли идея реализовать подобное?

Not sure how to calculate the most efficient acceleration profile, but as you say you could certainly include excenter profiles on the wheels, BOTH ends. The spring pulls the hardest as maximum stretch and a lot less near end of power stroke, could pay off to use an excenter profile on input wheel too, might need to step up the radius near end of spring movement to be sure it can actually add energy and not coast along at the end of spring contraction. Not sure if it pays off to have a smooth start acceleration curve or just start as violently as possible. Normal "compound" is to introduce a lower let-off force, slower start, but that is mainly I believe to compensate for human "issues". There are alot of simplifications that can be made by putting wheels vertically, like all wheels can be fixed on one thru-hole axle. That will however make excenter wheel design problematic as it would induce a wobble in Z-axis... that may lead to an extra support/guide wheel to eat up the variation but at a price of complexity and losses in power. I'm amazed that the plastics stand up to these forces!

Great work! 😎

Nice build 👌