my \"manuballista\" concept

[Warhammer1]

What would a modern manuballista possibly look like? How about a "pistol" manuballista?
http://warhammer1.wordpress.com/scorpyd ... completed/

The converted crossbow is a Scorpyd.

The other is just the product of a demented mind. A simple design utilizing two single pulleys. Certainly doable by ancient Romans as they did utilize pulleys in that time period. Use of the extention spring negates the need of constant tuning and maintainance, assuring an accurate release every time.
AS the extention spring is held under tension at rest holding the arms in place, no tension is needed in the string so that a very large percentage of available energy is expended. No stops needed. The design expends so much energy that you are able to dry fire the little machine repeatedly despite its small diameter soft metal arms.

If constructed as a railess design it cold shoot either sharps or blunts by simply changing out the string and/or removing the arrow rest. Anyway it will deliver 65llbs of pull with up to 24 inches of draw as pictured. By simply changing the string it becomes a regular inswinger again (non compounding) but with 130lbs pull and 15 inches of draw.

I cut the rail too short but here it is in a drawn position with only 20.5 inches of draw: http://warhammer1.wordpress.com/mini-ba ... stol-type/

[Vindex]

Interesting concept.

Is is possible to see photographs which show the weapon more clearly please? I find the back ground a little confusing to see your concept properly.

Ta!

[Warhammer1]

I'll try and post a few more pics and possibly a vid of my little ballista bow in action which I think is wickedly fast for something under 20lbs pull even with a 61 grain wooden dowel rod. While I cant be sure until chronied, I believe it may be up around 200fps, possibly better. The pics were taken on a spur of the moment thing by a friend who dropped with a camera.

Im sure I can do a better job if planned out.

An Italian designer came out with something similar to my little homemade springthing and was at the Archery Trade Association Trade show with a proto. http://www.tecnarm.com

Update: Using audacity digital sound software, I recorded the time it took for the arrow to pass through a piece of cardboard and then into the backstop exactly two metres away. If you divide the time by two you get metres per second. Test one with a 36.5 gram arrow (585 grains) came out at a dismal 30 metres per second. The second test with a 61 gram arrow (984 grains) came in at just 24 metres per second. I did remeasure the pull weight though, and near as I can tell with an old fish scale is right about 15 lbs pull.

In defense of the design though, the metal pulley wheels on the levers are purposely heavy, each one weighing in at 36 grams to test my impact acceleration tech. I think perhaps I am asking too much from the available draw weight as the levers are also made from steel, and weigh more than the pulley wheels. I did not bother to chrony the five ounce arrow which it still manages to throw out at a fair clip. Perhaps too much of the available power is being used up accelerating the steel levers and ball bearing pulley wheels. I will replace the heavy 36 gram pulley wheels for 7 gram plastic ones and see what shaving off two ounces of weight from arm tips will do and try a few more speed shots.

[Warhammer1]

Performance comparison of "concept" ballista bow vs regular inswinger

In re-thinking what I thought was dismal numbers for projectile velocities of 30 mps for a 36.5 gram arrow, and 24 mps for a 61.5 gram arrow, I retraced my thinking on what I believe is a design entirely capable of ancient tech or manufacturing techs, mostly involved the use of pulley wheels to add performance than be used in a simple winch. Certainly I can provide no evidence other than posssible design changes or modifications that result in higher velocities or improved performance in a given task.

Since all of my work began as addressing the ineffeciencies of the common slingshot, my ballista designs are where it ended up at as I addressed the problem areas where the machine lost energy and robbing the projectiles possible velocities. A stage one design most resembles the accepted Hatra/Orsova configuration and general design.

It occured to me late last night to use Professor VG Harts little machines for comparison, in trying to figure out why I had not attained velocities in excess of 200fps with my arrows.

This morning it appeared there are readily apparant differences which I will cover comparing the two since they are both approxiamately the same power. It appears the only way I will find out is to use a much lighter weight, approximating the mass used in Mr. Harts experiments. I dont think I have an arrow that light (3.5 grams) but it does appear my little machine may indeed be capable of 200fps and above provided I apply the same effeciecies to the material I use to construct my little machines. The closest I have to such a light weight is a length of small diameter bamboo used in indoor gardening situations. Previous shooting with the bamboo "arrows" saw them passing right through both sides of an old light panel door down in the basement. If I can find a suitable length I havent already destroyed, I will try the chrony with a lighter weight. There is also a large arrow 5.2 ounces in weight I will shoot after getting it down to a reasonable 1/4 lbs or four ounces by cutting off six inches or so.

Harts experiment had two masses one was 3.5 and the other 4.9 grams. Only one velocity was given for both machines - 43 mps for the inswinger and 30.5 mps for the out-tie. The max pull on both inswinger and outswinger ballistas he tested was set at 10 kilograms or about 22 lbs. Max range fired at that velocity at a 45 degree angle (hatra) resulted in 75m with the 3.5 mass. The out swinger range for 3.5 gram mass was 52.

My concept design managed 24 mps with a 61.5 gram arrow, and 30 mps with a 36.5 gram arrow. It seems logical then that since the lighter arrow used is still seven+ times the weight of the heavier projectile used by Hart, attaining 40 or 50 mps is not entirely out of the question even using the much heavier arms. The most obvious observation here is that despite having a projectile seven times the mass of the outswinger, my design was still able to match its performance, despite the fact the arm weight of the two machines is way out of wack.

Arm mass for Mr Harts machines both inswinger and outswinger was 7.5 grams.

Arm mass for my concept machine is 30 grams, plus another 36 grams for the roller bearing pulley wheel, a total of 66 grams or approx. nine times the weight.

Total mass of arm and projectile mass for Hart is 7.5 plus 3.5 for a total of 11 grams

Total mass of arm of projectile for ballista bow concept machine is:

(a) 66 plus 36 (30mps) total of 102 grams
(b)66 plus 61 (24)mps) total of 127 grams


A lot of my work involves Nicks beautiful machine the notion of working with that incredibel 5000 lbs of pull. While NIck is after attaining 400 fps which I think he should be able to do easily with the new mods, I think the true beauty of the inswinger design is that it is able to shoot incredibly heavy weights at pretty decents speeds. Pretty sure Nick will hit 400fps with the current 7000 grain arrows but feel firefly should be kicking out something two or even three times that weight at a lower speed of 250 - 275.

As evidence I offer the above velocity examples between the one and two ounce arrows. While I cant be 100% sure I think the evidence points out that the machines effeciency actually increases using the heavier weights. While the weight difference between the two arrows is 100% - the loss in velocity 30 mps down to 24 is significantly less (20%?).

Im pretty sure that if you triple the avaible power, like the pistol style mini ballista/catapult in my pictures, the end result in projectile velocities would be significantly higher.

[Warhammer1]

Just a quik update in my "in-swinger" promotion efforts. JoergS of the Slingshot Channel on youtube has just built an inswinger ballista slingshot.

In the video, he DOES admit that it provides about a 20% increase if velocities. Yeah, like thats new news. JoergS and I ran afoul in such a discussion online. Although he did not give me any credit, he did admit the in-swingers superiourity over non- torsion assisted inswinger slingshots, which previously before my efforts, did NOT exist.

I cannot access another tab on windows without losing RAT connection and log-in. To view Joergs video just go to youtube and punch in ballista slingshot and Im sure it will appear.
Another video to watch is the "Woodland Survival Flipper" which I am currently negotiating rights to manufacture and distribute (but my version).

Since it is patented already, I could email a video of my inswinger slingshot and bow design/prototypes for Duncan to post. I dont know if I can do it here, but I will try. Also there is a little ballista bow kickin out a 1275 grain arrow.

It will take me a few more years effort, but I will bring back torsion inswingers into mainstream once more.

Its an exciting time in Sports and Recreational Weaponry. See the Woodland Survival Flipper on youtube. Ballistas will make a comeback!

W

PS - Nicks machine is lookin' awesome. I wish I could be there for the ranging and penetration tests.

[Warhammer1]

videos of modern "scorpio" available. A torsion inswinger on a modern day Scorpyd crossbow platform. 60 pound pull, 174 fps 350 grains. Not rope bundle powered, but single extension spring for simplicity and reliability.

Have to send video by reg. email. If anyone is THAT curious to see a modern version of a scorpio (according to Warhammer at least) pm me.

Ballista(inswinger) archery bow vid available soon...