# Hatra Ballista



## TruckeeLocal (Dec 23, 2009)

I started this topic because other topics ended up on this subject. If you hav'nt read the 5000 words already written just google "hatra ballista" and picture that in a hand held size with tubular bands to power it and thats pretty much it so far. At present time, this is still just a mythical creature because there is no documented proof of its existence. We don't even have a hand rendering of this fictitious beast. So for now I believe this to be a "latex powered hand held hatra ballista".

Ok WarHammer you've got several of us interested so its time for some eye candy. Like Joerg, I believe that it time for a little more than talk. There is a point when you've heard someone talk so much that you start to wonder if its true or if its BS. I think we have passed that point already. Prototype not protohype.

Hey Joerg are you interested in making a prototype of something of this nature. This seems to be an interesting subject and it would be nice to see a working model properly tested even if its not a slingshot.


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## JoergS (Dec 17, 2009)

Truckee, I have seen ballistas already. The classical ones derive their power from twisted rope. Do you think you need to twist rubber instead of rope, or replace the bow string with rubber tubes?

I saw a "weapons masters" episode where they presented a reproduction of a historical ballista, and then they tried to modernise it. The ended up using truck springs as a power source, twisted the flat spring material just like the rope.

There is a slingshot that I own, called the Slingcat. It actually used a spring loaded lever that you pull out with the rubber. An interesting design! Doesn't come close to a flat band equipped "W" though. I once wrote a review in another forum, will pull it up and re-post it here.

Regards

Jörg


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## TruckeeLocal (Dec 23, 2009)

How much for the Slingcat?

I was thinking that that the tubing would replace the torsion twist. Cams would be attached to the pivot ends of the arms. The tubing would pull against those cams in a linear motion. Using one piece of tubing, each end would be attached to a cam so that the tubing rests parallel to the x axis.

Its 5:00am here in California so I don't have the time to bust out a 3d model right now. Maybe this weekend.


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## NightKnight (Dec 16, 2009)

Have you seen this one:
http://www.siege-engine.com/BabyHatraBallista.shtml


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## Warhammer1 (Dec 27, 2009)

The machine you describe is similar to a discarded proto. As you describe, simply increase the diameter of the "cams" and totally eliminate the levers altogether. Place the two disks apart an appropriate distance. attach powerbands to both top and bottom. You can now use it either way and as one powerband wears, simply turn it around and use it the other way.

This would also work for BKNIGHTS Hawian speargun, but will have two cams instead of one. For the Hawian speargun, use two cams, but simply stack them on top of each other for more compact design and simplicity.

The mousetrap design is best as it provides both the torsion spring and the levers at the same time. Just nail or screw two of them to a short board, arrange them so that theyt will load as you pull the string toward you. You can hold the two apart by nailing them both to a piece of plywood so that they are separated but securely held.

I have provided the board with five inswinger designs that do not interfere with my patentability.

1) Stan Wings archery bow

2) Nicks inswinger ballista from Watts Unique .com

3) siege engines "hatra video

4) rat trap design.

5) the above design(s).

*** I have been more than generous here and have tried to share knowledge. There is a limit to my generousity and willingness to help. You cannot learn except by experience of building them, identifying problems, and overcoming them by careful consideration. Have fun with the new ideas and concepts I've shared with you all here.
One of the main benefits of the inswinging design is that very heavy weights can be used. While no speed demon, a medium pull latex powerband has powered a 1.25" (30mm) ball bearing weighing 112 grams. It will totally destroy cement housebricks, or red clay bricks and keep on going with just a 30lbs pull and 30 inch draw.

I imagine a heavier pull band like Trumark heavy duty would be similar in power, maybe even more so. I have not found the need for more powerful bands to use within the house than 30lbs pull which is pretty strong to allow shot after shot in an afternoons pleasure activity. Accuracy suffers with too heavy a pull for the strength of the user.



TruckeeLocal said:


> How much for the Slingcat?
> 
> I was thinking that that the tubing would replace the torsion twist. Cams would be attached to the pivot ends of the arms. The tubing would pull against those cams in a linear motion. Using one piece of tubing, each end would be attached to a cam so that the tubing rests parallel to the x axis.
> 
> Its 5:00am here in California so I don't have the time to bust out a 3d model right now. Maybe this weekend.


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## TruckeeLocal (Dec 23, 2009)

OK everyone WarHammer has finally given us some eye candy. This is not his design but it is food for thought.


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