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Building a Ballista...

PostPosted: Mon Jun 11, 2012 9:15 pm
by AK_Brickster
It has been decided between myself and some friends of mine that we are going to build a ballista. It will live in my friend's garage next to their already-popular-at-family-gatherings trebuchet, which has a throwing arm that's approximately 8' long (perfect for hurling small melons or giant wads of duct tape :))

Anyway, I will be using this thread to document our progress and also I wanted to reach out to our very knowledgable community for ideas, tips and possible resources.

The main site that I'm using for reference is http://www.siege-engine.com
it's a very informative and interesting site. I recommend you give it a quick perusal.

I guess I'll start the journey by telling you that we spent a few hours hunkered over our smart phones brainstorming at a recent gathering. They initially came to me to get an "engineer's opinion" of their idea, which was to build basically a large crossbow. After googling "build your own ballista" I found that a more accurate version would use twisted rope to propel the projectile, and I think we've decided to go that route. Here is our inspirational picture, though we will probably aim to build one about 1/2 to 1/3 the size of the one in the image below:

Image

Re: Building a Ballista...

PostPosted: Wed Jun 13, 2012 3:51 pm
by Medieval Guy
This looks exciting! How are you planning to twist the ropes tightly enough? With some kind of lever? Also, the tension on both sides will have to be equal, or close too it, so I'd be interested to know how you manage that.

Re: Building a Ballista...

PostPosted: Mon Jun 18, 2012 5:49 pm
by AK_Brickster
I worked on my Lego prototype last night and this is as far as I got

(please ignore my wife commiserating with the dog in the background about the unfairness of being kenneled for the night, lol)

http://youtu.be/wPZMxTzx9Sw

Obviously, I still need to add the other arm and the drawstring, but I think good progress is being made. Everything in the model is 100% Lego (even the strings)

Re: Building a Ballista...

PostPosted: Mon Jun 18, 2012 6:11 pm
by Heir of Black Falcon
cool project. we built a small one in 1998. It was rather neat and could shoot tennis balls two hundred plus feet.

have you seen this?
http://www.google.com/url?sa=t&rct=j&q= ... j8IsvNAZrA

a BBC program building the impossible: the roman war machine.

RPM

Re: Building a Ballista...

PostPosted: Mon Jun 18, 2012 7:26 pm
by AK_Brickster
Nice video! I had seen images of their final result while researching this topic a bit, but hadn't seen the footage. Looks like an episode I'll have to look up.

Since you built one, do you have any pics, plans, or tips you could share? I'm not sure how big my friends want to go (they are buying the materials, so it's up to them ;) ) but being able to launch a tennis ball 200' sounds like a good starting point :D

Re: Building a Ballista...

PostPosted: Mon Jun 18, 2012 8:34 pm
by friskywhiskers
AK_Brickster wrote:Nice video! I had seen images of their final result while researching this topic a bit, but hadn't seen the footage. Looks like an episode I'll have to look up.

Since you built one, do you have any pics, plans, or tips you could share? I'm not sure how big my friends want to go (they are buying the materials, so it's up to them ;) ) but being able to launch a tennis ball 200' sounds like a good starting point :D


Maybe you would want to check w/ your neighbors before launching tennis balls at high speed throughout the town :lol: .

Re: Building a Ballista...

PostPosted: Mon Jun 18, 2012 11:49 pm
by Redav
friskywhiskers wrote:Maybe you would want to check w/ your neighbors before launching tennis balls at high speed throughout the town :lol: .

Nah, it's easier to ask for forgivness than for permission. Go forth and conquer!

Veni, vidi, I subscribed

Re: Building a Ballista...

PostPosted: Tue Jun 19, 2012 12:03 am
by friskywhiskers
Redav wrote:
friskywhiskers wrote:Maybe you would want to check w/ your neighbors before launching tennis balls at high speed throughout the town :lol: .

Nah, it's easier to ask for forgivness than for permission. Go forth and conquer!

Veni, vidi, I subscribed


Yes, that's what Napoleon Thought. Then he got his **s shipped of to a deserted Island. :)

Re: Building a Ballista...

PostPosted: Tue Jun 19, 2012 3:53 am
by Heir of Black Falcon
RAT is the place for Roman Historical stuff online.

http://www.romanarmytalk.com/rat.html?f ... =entrypage

I'd add only a little, better to overbuild than under.

Be aware that in some places having such items is actually illegal. I have lived in many states and a number of countries and I try doing some research to be safe.

Heir

Re: Building a Ballista...

PostPosted: Tue Jun 19, 2012 8:28 pm
by AK_Brickster
I finished the prototype last night. Here is an image of it, but there are more in my Flickr gallery and I'm uploading a video to YouTube as we speak...

Image

Since I'm only using a single lego string on each side (doubled up), I didn't really crank up the tension on it. It currently can shoot a Lego soccer ball or my technic axle spear about 6 feet.

It's amazing how much tension you build up in the torsion arms for the amount of forward thrust that's generated. If I can find some stronger braided string, I may try upping the torsion a bit, but I also don't want to damage the bricks! Anyway, I hope you enjoy. I'll keep you posted on further developments :)

EDIT: Here is the YouTube video of the ballista in action! VIDEO LINK

Re: Building a Ballista...

PostPosted: Tue Jun 19, 2012 9:50 pm
by Shadowviking
AK_Brickster wrote:(please ignore my wife commiserating with the dog in the background about the unfairness of being kenneled for the night, lol)

Dude,
you kenneled your wife? That's a bit much innit? :P


Just kidding. Awesome project. I love ballistas. Not always sure they're the most efficient siege weapon, but they are very, very cool imo.
Looking forward to seeing more of this. And if it's not too personal I'd love a price tag on the build to see if it's worth my while to build a real one, or if I should stick to LEGO. ;)