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"Ballista Bow" to see production! (in-swinger)
#1
Hi Folks!

Just finalized a deal with Pullin Archery to manufacture my manuballista bow designed especially to assist phsically challenged people. Spring powered and torsion based the bow will be approx. 20 inches axle to axle, with 55lbs max draw weight, and powerstroke between 20 to 25 inches.

Will this be a first in recorded history? Arrow weight 350 - 500 grains, looking for 300fps plus.

Its been a very long long road. Hope this might put a smile on some of your faces! As it will help marginalized people I hope some folks will applaud my efforts and purchase one when available. Custom orders will probly be available within six months. Pics will follow as soon as IP is in place.

Torsion WILL rule!

Suggestions for name? Something a little more creative than just plain Ballista Bow. X-Bo perhaps?
Torsion rules! - Joel from Ham. Ont. Ca.
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#2
Congratulations on that!

Perhaps something simple, like The Tor-bow?
Visne partem mei capere? Comminus agamus! * Me semper rogo, Quid faceret Iulius Caesar? * Confidence is a good thing! Overconfidence is too much of a good thing.
[b]Legio XIIII GMV. (Q. Magivs)RMRS Remember Atuatuca! Vengence will be ours!
Titus Flavius Germanus
Batavian Coh I
Byron Angel
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#3
Hello and thanx for reply. Yeah, thats better than X bow, I want something to distinguish/separate it completely from crossbows, so that is much better! Tor-Bow, or T-Bow... hmmmm.

Im putting out word on some forums asking for input from folks with disabilities of all sorts who are having trouble finding proper equipment they can use comfortably, and what their special problems and needs are. Maybe there are a few folks here who can chip in... my email is for those who might not want publically announced input (pm would do)is [email protected]

Its for a good cause folks so dont be shy. I dont bite - at least not that hard. :lol:

Well again thanx for the reply and input. Tuff crowd here LOL. Confusedhock: Cry
Torsion rules! - Joel from Ham. Ont. Ca.
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#4
Yikes.

Well, you all sure is a tuff crowd to work. How about just discussing this then?

data sampling from prototype with axle to axle spacing of 20.5 inches, six inch limbs, and no pulley or cams:

Limb arc..............draw in inches.........Limb arc to draw inches
20........................6"...................... ..3.3
45........................10...................... ..4.5
60........................12...................... .5.2
90........................15...................... .6.0
120......................18....................... 6.3
135......................20....................... .6.75

A basic compounding inswinger design with simple pullies. Should be a RAT first - data from simple inswinger with pulley wheels on limbs - YES a compounding design...Yes, Duncan told me they did have pullies in days of old... if only to wind machine! Surely one of them had thought of it. This is MY theory, but no proof. Did they use a simple block and tackle to load machine in them days. Some of you say yes....notice the change in limb arc per inch of draw compared to basic in-swinger design? THIS would have given the performance spoken of.

Lever arc...............draw in inches.............Limb arc per inch of draw in degrees
15...............................8................ .........1.87
23..............................10................ ........2.3
45..............................12................ ........3.75
68..............................16................ ........4.25
90..............................21................ ........4.28
115............................25................. ........4.60
135............................28................. .........4.82

How does axle spacing effect such a crossbow or bow design? 6 inch levers, no pulley (causes extra length).

Spacing......Draw length@[email protected] to draw@ 90..........@135
13"...............12.5......................16.5.. .............7.2.....................8.18
15"...............13.5......................17.... .............6.6.....................7.9
18'...............15.0.......................18.0. .............6.0.....................7.5
24................16........................20.... .............5.6.....................6.75
30................18........................21.... .............5.0.....................6.43
36"...............20........................23.5.. ............4.5.....................5.74

As you can see my machines can provide some real fun, and I've had a blast designing and building them over the past ten years. Narrow spacing good for rocks. Wide spacing good for arrows. Allows one to control angle of pull....more arc....135 degrees higher energy potential. 90 degrees more effecient use of power....Which spacing would YOU choose?
What does limb arc per inch of draw have to do with anything???
Torsion rules! - Joel from Ham. Ont. Ca.
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#5
Well, time to tweak the ballista bow one more time. The data above clearly shows its a simple thing to increase the effeciency simply by incremental increases in the spacing between "rope bundles" (as I have axles). By further increasing the ratio of limb length to spacing, I gain effeciencey that will ulitimately be measured by a change in terminal velocities. The machine will then assign more string travel through the entire lever arc movement.

The other reason for doing it is a simple increase in power. The little machine can handle 25lbs quite comfortably with the current set up, but by shortening the levers from 6.25 to 5.25 gives my an incremental increase in power without further modification, a simple remedy. The change will hopefully gain me another 5Lbs of draw weight. A 20% increase, along with more string travel per degree of lever arc.
Torsion rules! - Joel from Ham. Ont. Ca.
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#6
Hey all Nick from WattsUnique and his archeogical experiments in ballistica (study of ballistas, term I coined) are happening again. Through light hearted jesting I goaded him into trying a 10,000 grain "durabolt" but the machine was not properly tuned, the arrow went sideways, and smashed into many pieces upon impact with the target...

Despite this fact and the machines new rope bundle engines are just getting "warmed up" the bolts recorded 208 fps with about 3600lbs of pull.
He has some lighter bolts ready to rock and is now conducting tests with a variety of heavier weight bolts much heavier than his previous 2800 grain "durabolts". Heres an except from his blog, tune in weekly or monthly for testing results. www.wattsunique.com

Tue 23 Feb, 2010
Day-glow
Comments (0) Filed under: The Ballista

I made up 6 bolts today, 26? long and varying in weight from 6500 to 8379 grains. Painting them day-glow orange seems to help visibility for the video. I only managed one shot before the light turned sour. Here is some footage of that shot, slowed down 4 times. 20100223153553

The slow motion flight of the bolt is visible for 70 yards and a small spurt of white can be seen as it burrows into a patch of snow, just outside the veggie garden. Also, this video clearly shows the bolt flying wide to the left. More torque is needed on the port side bundle. I will try and get more video as the tuning proceeds, and then we can see the shots finally straighten out. Specs on this shot as follows: weight of bolt 8379 grains; draw weight 3700 lbs; draw length 49?; additional 7 1/2 degrees added to the top washer starboard side; velocity 233 fps; energy 1010 foot pounds. I plan on getting the bundles balanced and the shots flying true, before applying the higher levels of torque to the bundles. Nap now. ………


Other: Warhammer has arranged to build a few more manuballista prototypes using the Scorpyd crossbow rail, stock and trigger assembly. Also has permission to prototype a in-swinging hunting how using Scorpyds patented Reverse Limb Tech. Scorpyd is coming out with a new crossbow in April that has 165lbs pull, 20" powerstroke, and will hit a smokin 460fps with a 350grain arrow.

Can old Warhammer design and build the worlds fastest bow? A "ballista bow"? And an inswinger to boot! I think so, but will need a Hercules type archer to weld it. A big man's bow, requiring the strength of a big man... 165lbs pull, a 27 inch powerstroke, and maybe JUST maybe a 500fps inswinger hunting bow can it be done? Yep. Will I have the resources to pull it off? We'll see.

Since the 165lbs pull bow hasnt hit the streets yet, I'll start off with a 80 or 100lbs pull, 24 inch powerstroke, 7-8" brace height. It all takes money which is in short supply around MY house. I'll give it my best shot anyway.

W
Torsion rules! - Joel from Ham. Ont. Ca.
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#7
Ballista news flash - Nick from watts unique . com has finally hit the 400 fps mark with his Orsova in-swinger. He used a 7500 grain durabolt, and about 5000lbs of pull to accomplish this. He did this using less than 90 degrees of limb arc. There are some great recent videos including the 401fps chronied shot.

Nicks work (research) should be a great resource for future in-swinger builds where performance is the goal.
Torsion rules! - Joel from Ham. Ont. Ca.
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