Sunday, January 2, 2011

"The Eagle" - Butterfly shooter for tubes, with rollers

Had these rollers lying around, from a DIY shopping spree a while back. They are really cheap, originally for rope of course.

I also had some aluminum tube with just the right diameter to serve as axis - so I decided to do a variation of my 4x4 design, but in wood, and for tubes.

The design came out really well. It gives me about 22 cm of a draw extension, ideal for the task as it is easy to load a ball into the pouch and it does allow full butterfly.

This is really powerful, especially with heavy lead balls!

It is also not so hard to make, I consider making a tutorial video soon.


  1. This design has potential. I can see it as a slingbow with the addition of an arrow rest. If someone wanted to be really creative, they could even make the outline of an eagle to bring the design home and to dress it up.

    The form and function of the pulley mechanism is something that I am not understanding the concept behind. It would seem to me that you would get little benefit from the pulleys.

    What is the draw pull on this model?

    Again, fantastic work that you are doing with both the slingshots and slingbows.

  2. The pulleys store rubber, about 22 cm per side. Without these pulleys the "dead play" (the loop) would be 22 cm longer, the effective acceleration phase would be shorter and the shot would be weaker.

    Alternatively, one could forward extend the fork by 22 cm, which would have the same effect. But then a wrist brace would be needed as the slingshot would "want" to turn in your hand when you draw out. This would make a clumsy (and illegal, in many places) wrist brace necessary.

    The draw is about 13 kg in full butterfly (160 cm draw length).

    Shooting arrows would be possible, but my dedicated slingbows are a lot better for that job. This is a ball shooter really.

  3. First of all, love the show and the awesome weaponry you construct, I wish they were legal in my country so I could join in the fun. Instead I must resort to imagining and admiring.

    Perhaps this is the wrong place to ask this question. Is there any advantage to a pulley system in slingshots beyond reducing dead play? How much energy is transferred to the projectile from the part of the band that is still in the pulley system when the band is fully stretched out?

    Can we increase the draw length indefinitely by adding even more pulleys!? We could put the first marble on the moon!

    Okay, most likely not as there must be some point where adding more pulleys or having a certain amount of band in the pulley system other than that needed to minimise dead play is either ineffective or serves to actually reduce power. Assuming a perfect pulley system though, where is this point? Or, where can I go to find out? Please and thanks.