5289Views7Replies

Author Options:

What kind of rope is best for a ballista? Answered

Would Nylon or Polypropene make a good torsion spring?Or would some kind of metal wire work better? By "better" i mean is able to produce the most force or is able to pack the most force into a 5/8"hole (thats the biggest drill bit i have).

Discussions

0
None
steveastrouk

Best Answer 7 years ago

Which is most elastic ? Do some simple tests by hanging a piece of rope with a varying load and measuring it. I suspect a natural sisal rope might work very well.

0
None
seandoguesteveastrouk

Answer 7 years ago

+1

I don't know if it's the weave used or what, but in my experience, nylon rope stretches quite a bit under load, (far, far more so than hemp rope) implying that it has a very low spring constant.

0
None
meburnfireseandogue

Answer 7 years ago

So nylon would make a very bad spring as it stretches, which means it isn't a good spring as it wouldn't be able to hold a constant amount of force whereas a hemp or sisal rope would work much better as a spring as it is able to keep its springiness for a longer period of time and hold it better?

0
None
seandoguemeburnfire

Answer 7 years ago

Well, that's *my opinion, based on previous experience trying to use nylon rope for both pulling and suspending heavy loads. As I noted, it could be a weave issue, although I'm not sure.

It has been my experience that hemp rope is far less "stretchy", so I would think it would have a higher spring constant. I don't have enough experience trying to support any weight of consequence with sisal. My experience there is pretty much limited to tomato/cucumber cages and bundling sticks.

I was mainly +1-ing the "Do some simple tests by hanging a piece of rope...", since that's probably the best advise of all, short of a ballista expert chiming in.

0
None
meburnfireseandogue

Answer 7 years ago

Well, i made the ballista and tested it... and i couldnt get enough sisal/hemp/manila at a reasonable price to make the second spring, and i found that nylon is actually pretty strong as after a while, it cant stretch and you can just tighten it. A lot.

0
None
fieldhockey4020meburnfire

Reply 4 months ago

So which kind of rope do you think worked the best, I'm trying to make a catapult for school and i wasn't sure what rope to use.

0
None
rickharris

7 years ago

In general the older weapons used animal sinews as springs rather than ropes. The Romans made Ballistas with hemp rope. But I would say nylon is going to be your best bet - Polyprop tends to neck and stretch under strain.