Pouch for ~150-175 pound slingshot crossbow?

Discussion in 'Slingshot Crossbows' started by Jeff213, Mar 15, 2016.

  1. Jeff213

    Jeff213 New Member

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    ~150-175+ pound, welded stainless slingshot crossbow

    I am building a badass slingshot crossbow out of 316 stainless tubing/ angle, welded, with a metal trigger group,with a carbon fiber tubing stuff inside it for more rigidity, an actual rifle stock, roller bearing pulleys (skateboard wheels), and 3/4 inch speargun rubber for the bands.

    What should the pouch me made of to stand up to this much weight? Should I just use thick leather?

    I am going to shoot ~470 grain round balls and heavy bolts out of it.
     
    Last edited: Mar 17, 2016

  2. Jeff213

    Jeff213 New Member

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    No pictures yet, I have been churning the idea around in my head for a month now, thinking about it every single day and refining the design. I have some rough sketches done in the notepad app on my phone.

    I have the tubing, and the qb78 air rifle stock which the tubing fits PERFECTLY into, but the angle wont be here until thursday.

    I do gunsmithing work as a hobby so I have some insights into the workings of a trigger and sear. I also weld as a hobby, and if I get good enough I may start welding professionally as well, but this is all practice for me.

    I don't know when the skateboard wheels or the carbon fiber tubing will come in but I can't put in the carbon fiber tubing until I finish all the welds anyway.

    I am designing the trigger group this weekend, I already have an idea how it will work.

    It will be wheel, with a release somewhat like the one on Joerg's midevil crossbow, but it will be fired with a trigger. The sear will be cut into the wheel, and case hardened, and the release will be welded to the wheel. the trigger will be case hardened as well where it comes in contact with the sear. The whole unit will be sandwiched in between some 18ga plates and attached (welded or bolted, not sure yet) to the tube "receiver" of the crossbow, going through a vertical slot up to the top. I may do some testing with a spring that will pull the release back into position after the ball / bolt is released but that will be later on. If i go with changeable bands there will be a smaller release built into the wheel in front of the main release to clip a D-Loop into for shooting bolts.

    The pulleys will be some convex shaped skateboard wheels stacked 2 high and sandwhiched together to form a groove, mounted on a bolt that is welded onto the 316 stainless angle. I will use U bolts or something similar to prevent the band from popping completely off the pulleys when the slingbow is fired, but they will be completely untouched by the band at any other time in the firing cycle until after the projectile is released.

    I am thinking of using either a removable band system, or a removable knock, to make the switch between bolts and cast lead balls, both will be approx 450 grains (heavy ammo)

    It will also have a stirrup to aid in cocking, the stirrup will probably be made out of a bracket that I brought home after a demolition job. The brackets have been sitting in my shed for 3 years looking for a good use.

    I have thought about the idea of pouring some molten lead into the pipe toward the back where the trigger group will be attached and the carbon fiber tube won't fit to give it some more rigidity and shift the weight back to the rear but this idea hasn't been explored too much yet and I don't know if the contraption will be too heavy.

    I have already invested considerable time and money into this project, and I will be going through with it, I will post some picture updates as I go along, and will be looking for suggestions.
     
    Last edited: Mar 16, 2016
  3. JoergS

    JoergS Administrator

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    Sounds like a cool project!

    175 pounds isn't all that much, I used leather pouches on heavier bands. You might want to use two layers of the leather though, for the piece of mind. Remember leather isn't leather, one skin may be very tough, another one may tear very easily. You gotta find the right type. Do some tests in the vise.

    Remember if you use the wheel method, you MUST punch a large center hole into the pouch or else the shot will go wild. The pouch will simply slip over the BB and it will come out high uncontrolled.

    Good luck!
     
  4. Jeff213

    Jeff213 New Member

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    thanks Joerg, I will try that.

    I was also reading that people here dont like rollers much.. should i abandon the roller idea even though it will have ball b3arings and just make the bands pull straight back? this will reduce weight.

    EDIT: After more research I will scrap the rollers, I have some ideas though for a true compound sling x-bow for the future, but i need to make a working sling xbow first before I try anything super fancy.
     
    Last edited: Mar 16, 2016
  5. JoergS

    JoergS Administrator

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    That is probably a very clever approach. Rollers really don't add much power, but they sure cause a million issues during construction AND during normal operation of the weapon.
     
  6. Bone

    Bone Slingshot Shooters

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    Sounds like fun. Can't wait to see the progress.
     
  7. Jeff213

    Jeff213 New Member

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    My carbon fiber tubing came in today, as well as my stainless angle bracket. I got plenty of stainless angle, but only have enough stainless tubing and carbon fiber tubing for 1 slingshot.

    I was wondering if anyone has figured out a sort of optimum distance between band attachments to pull length ratio using 3/4" speargun tubing. I am thinking I want to pre tense the bands because I want to get maximum power out of this thing, but the wider apart I place the "limbs" where the tubing attaches, the more leverage there will be on the angle, possibly causing it to bend. It will also be harder to handle the wider it is.

    Would 2 feet apart from limb to limb at the front, pre tensed to 30 pounds or so and a 3 foot draw length be a good combination? Would you go with more or less? I can always shorten the metal later, technically I could weld more on and make it wider as well but this will detract from the aesthetics of it.
     
  8. Fipfip33

    Fipfip33 Scout Shooter

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    I don't know if this helps or not but I built a sling-xbow that shoots bolts using speargun rubber.I used rolers to save space and not have the rifle so long but the rolers are the biggest pain. It works not too but yeah I think rolers can be difficult to work with.

    Keep us updated!