Also, how do you get so much pressure from that skein? Do you insert the arm and then twist the skeins round and then fix the skein into place? Is that what gives it it's strength? Otherwise, without it being twisted, I don't see any other way so much pressure can be put into it.
Once the arm is in place, the skein is wound tight on either side of it. For this model, I have a pawl to hold the skein taught, but there's enough friction that it isn't really required. This video only has the skein at about 1 1/2 turns on either side, but I was able to get 2 3/4 turns on another similar model. Under that much tension, it was able to throw the hex nut about 70 feet, which isn't too bad for a four inch model :-D
The material needs to be as elastic as possible. I don't use any kind of braided or twisted cording for the skein as a lot of the torsion energy gets lost in them, and the twisted ones will have a bias resulting in unequal power on either side of the arm. As far as the trigger goes, I use a slip-hook attached to the takedown winch so it can be fired at any point. I've got some pics on my flickr page that show the trigger design that I'm using.
I used 25lb nylon fishing line for the two small onagers I've done so far. It's reasonably elastic, and doesn't abrade itself as the skein is wound down. You might be able to use rubber bands for some projects, but I think you'll need a *massive* skein to get the right amount of power out of it. For the next one, I've decided to switch to 15lb line, which is supposed to be relatively close to the breaking strength of sinew.
Also, how do you get so much pressure from that skein? Do you insert the arm and then twist the skeins round and then fix the skein into place? Is that what gives it it's strength? Otherwise, without it being twisted, I don't see any other way so much pressure can be put into it.
shabiraziz 2 years ago
Once the arm is in place, the skein is wound tight on either side of it. For this model, I have a pawl to hold the skein taught, but there's enough friction that it isn't really required. This video only has the skein at about 1 1/2 turns on either side, but I was able to get 2 3/4 turns on another similar model. Under that much tension, it was able to throw the hex nut about 70 feet, which isn't too bad for a four inch model :-D
imgunby 2 years ago
Brilliant stuff. I have 2 questions.
Firstly, instead of the fishing line wire, can you instead use thin rope for the skein, or does the material need to be elastic?
Secondly, how exactly does the releasing of the arm work? I.e. what exactly did you at the end to release the arm and send the projecticle flying?
Thanks so much. :)
shabiraziz 2 years ago
The material needs to be as elastic as possible. I don't use any kind of braided or twisted cording for the skein as a lot of the torsion energy gets lost in them, and the twisted ones will have a bias resulting in unequal power on either side of the arm. As far as the trigger goes, I use a slip-hook attached to the takedown winch so it can be fired at any point. I've got some pics on my flickr page that show the trigger design that I'm using.
imgunby 2 years ago
i realy have to do one of those
talibanrules 2 years ago
I used 25lb nylon fishing line for the two small onagers I've done so far. It's reasonably elastic, and doesn't abrade itself as the skein is wound down. You might be able to use rubber bands for some projects, but I think you'll need a *massive* skein to get the right amount of power out of it. For the next one, I've decided to switch to 15lb line, which is supposed to be relatively close to the breaking strength of sinew.
imgunby 3 years ago
for the trust did u use String
cant i use Rubber bands??
13chungh1 3 years ago
nice
Zergosss 3 years ago