Ballista version

[gneuspartak]

Let me show you my inswinger version of the Heron-Wilkins ballista.
The first construction was made as outswinger system.
I used the nylon rope for my ballista constructions. This is not effective.
The first (and last) test showed that ballista have shot only 95 meters.
I will correct of the error.

[P. Clodius Secundus]

Denis,
Very nice work! Thanks for sharing.
I'm suprised that you call it a Heron-Wilkins ballista. What you have made looks much more like the designs of John Anstee or Aitor Iriarte. What did you do with the big bronze locking rings and linear ratchet? Was there enough extra metal left over to make another set of washers and frames? If so, please consider sending them to me. I have been a very bad boy all year and Santa Claus will probably put only coal in my stocking
Please post more photos and keep us all informed of your progress

[Gaius Julius Caesar]

Thanks for the photos, I finaly understand the exact meaning of the in swinger mechanism....... :oops:

[gneuspartak]

The first construction version had been made like the design of A. Wilkins by Ildar Kayumov ( last photo ).
I made alternative frame construction after I have consulted with Russian specialist of the roman artillery.
This construction have been made without «the big bronze locking rings».
I applied «The inswinger theory» by A.Iriarte .
Photo of the working progress:

[Crispvs]

"inswinger version of the Heron-Wilkins ballista"

Alan would probably be wearing a very pained and frustrated expression by now if he had read that. I will not attempt to spoil his normal good humour and forbearance by passing the phrase on to him. :wink:

Perhaps it aught to be referred to as the 'Iriate-type catapulta'. Credit should go where it is due: Aitor is, after all. the father and effective inventor of the inswinger catapult, something so good that the ancients would surely have used it if they had had it. :twisted:

On the positive side, your workmanship is admirable and despite my reservations, I do look forward to hearing more about your test results as you continue to test it. Please do carry on. All of us here need to learn more about virtually every aspect of these machines.

Crispvs

[P. Clodius Secundus]

Perhaps it aught to be referred to as the 'Iriate-type catapulta'. Credit should go where it is due: Aitor is, after all. the father and effective inventor of the inswinger catapult, something so good that the ancients would surely have used it if they had had it. :twisted:

As much as I admire Aitor's many contributions, (He's done yeoman's work demonstrating, publishing, and popularizing the idea.) I don't believe he would accept credit for the in-swinger concept. He traces it back through Anstee and Prou to Heron himself. IIRC Prou published in 1877. He didn't have the benefit of the Lyon, Gornea, Orsova, or Hatra frame to point the way. IMHO it's nearly the same situation as De Reffye and the onager. The Victorian era theorists were on the right track until the Edwardian's came along and mucked it all up. Folks have spent the last hundred years arguing which turn of the century red herring to chase. When new evidence comes along rather than question basic assumptions, it's more convenient to conjure up a big chunk of bronze that makes it work. In that sense I praise Mr. Wilkins as a most capable inventor. :wink:

Merry Christmas to all!

[Warhammer1]

When new evidence comes along rather than question basic assumptions, it's more convenient to conjure up a big chunk of bronze that makes it work. In that sense I praise Mr. Wilkins as a most capable inventor. :wink:

Merry Christmas to all![/quote]

- Well.... since you mention inventors thought I'd share some data with you. I ran some data to see if if I could get the machine to assign more string movement to the levers once they are drawn past the 90 degree mark. My pathetically underpowered "ballistas" seem to pull some nice weight for the size. My inswinger ballista bow likes arrows over 1000 grains even though its under 40 lbs pull. My latest arrow is 34 inches long and 3/4" diameter and weighs in at 1600 grains. Not a 300M machine for sure, but nice for 15 M target practice. A 500 grain arrow should have no prob with 300 yards though.

Data using 6" levers (inswinger)

Spacing................Draw @90............ @ 135..................Arc to draw @ 90...............@135

13".......................12.5...................16.5........................7.2........................ 8.18

15".......................13.5....................17........................6.66........................7.9

18".......................15......................18.........................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


The machine with very closely spaced limbs seems best as a stone hurler. The first entry shows a very high draw length to width ratio at 90 degrees limb rotation, the levers averaging 7.2 degrees per inch of string travel. This is like a loaded truck pulling a hill in first gear. Nice long acceleration pathway as well which is needed for heavier projectiles.

On the other end of the scale where width is 6 times lever length, total draw at 90 increases very little ratio wise, BUT, the machine assigns more string movement to lever arc. Only 4.5 degrees per inch of draw which means the machine is more suited to lighter weights and throwing them almost twice as fast...

The data also supports that arrow shooters probly best not to exceed 90 degrees for peak effeciency, while stone hurlers could go with the max amount of lever travel the machine is capable of. If 120 is the average max for most rope bundle machines, that gives the machine 30 degrees to accelerate the arms or levers before any real movement is assigned to the string and projectile.

Since I work with arrow shooters I mostly have used a machine width of about 3 times the limb length - 18 inches. This is a nice balance because it seems to handle either really well. Actually I strive for 3.33 times lever length for width, although a width of 2.5 times the lever length seems most effective from the data.

It will be interesting to see what kind of velocities I will be able to get with a 1600 - 2000 grain arrow and about three or four times the power I currently use. Now that will be an interesting machine when built...

When in doubt I always seek data. Hope this might help with your ballista building!

Warhammer.

[jkaler48]

Sinew rope that's the thing everyone needs to find out what all these different machines can really do! But is not easy to find!

[Warhammer1]

I see you missed the point the data points out. The machine with the 24 inch rope bundle spacing has about the same draw length at 90 degrees than the 15 inch wide machine does at a full 135 degrees (120 degree max for rope bundle tech). Not only that, but the configuration has assigned more string movement (velocity) per degree of limb/lever arc.

Remember that half the total draw occurs at 30- 35 degrees depending on spacing. Given that, instead of concentrating on what material to make the bundle out of, perhaps tuning the machine to provide max torque a lot earlier on and using less lever arc is condusive to higher velocities.
Not only that but the huge amounts of torque most machines are loaded to under max limb rotation is counter productive to machine reliability and rope bundle life.

Using only a portion of the available power will allow you to fire the machine all day without much problem, or should anyway. A rope bundle loaded to a 3000 lbs max cap. with a two foot lever will produce over 6000 lbs at limb tip with a one foot long lever...

There are other factors involved, but altering ones perceptions about the machine would have a much greater effect on end velocities or projectile mass capabilities than simply adding more power.

Supporting evidence (a): http://www.schoolforchampions.com/scien ... antage.htm
Supporting evidence (b): http://www.schoolforchampions.com/scien ... torque.htm

Sinew rope that's the thing everyone needs to find out what all these different machines can really do! But is not easy to find!