With the new chronograph up and running, here are the results from a couple of preliminary shots made this morning.  The bolt we used is left over from the Gallwey project and not really ideal for the Orsova machine.  When we get around to making the lighter Dura Europos style bolts, velocity should increase quite a bit.  The data below is from half draw so it’s pretty low power stuff.  It is just a sneak preview of a long series of higher power tests that will be performed soon.  Yes I know, the quality of the videos is terrible, but even with it you can see that the frame of the machine shows no sign of vibration or movement during firing.  This is probably the best news yet as it promises good accuracy in the future.

Bolt weight             Velocity                    Energy                   Draw length

First shot                  5,015 grains             208 fps                   481.74 ft/lbs                      34″

Second shot              5,015 grains           214.7 fps                  513.27 ft/lbs                      36″

Click here for video of the above shots,  field-test-4

Click here for some ten year old footage of the Gallwey at high  power (1150 foot pounds), zipping through 4 sheets of 3/4″ plywood with a 1″ blunt.    gallwey-1a

The maximum draw of the Orsova reconstruction is 63″ and testing at that level will have to wait for the electric winch to show up.  It will allow us to go to the higher power levels with some measure of safety.  A remote control for the winch has also been ordered so we can stand behind cover when a limb breaks (yes, something will break eventually).  If we extrapolate a geometric increase in power from these two data points, full draw should put us at about the same power level as the Gallwey reconstruction with its massively bigger springs.  If the power rises exponetially, perhaps it will even exceed the Gallwey.  Either way, even these half draw tests indicate that the Orsova inswinger could develop plenty of power with its much smaller springs.

The sinew ropes the ancients preferred for their ballistas must have been hard to come by.   Being perishable, labor and resource intensive, and in high demand for many applications, sinew rope was surely a valuable commodity in ancient times.   If the inswinger design could have allowed the Romans to make powerful torsion engines while using less sinew, that would have been a big logistical advantage in a far flung empire.

3 Responses to “Low power testing.”

  1. D B Campbell says:

    Fascinating stuff, Nick. If Dietwulf Baatz is reading this, he should be very pleased with himself. 25 years ago, without the assistance of scientific instruments, he estimated the initial velocity of a catapult missile as 72m/s. Vindicated!

  2. Nick Watts says:

    Vindicated indeed! And then some. I see the need to reproduce my results in metric as well as english measure.
    From this low power testing our best shot indicates 65.44 m/s and 695.83 joules. From the mid range testing in the next post we see 75.98 m/s with 938.01 joules. Going to full draw with stabilized and more highly strained bundles, should increase these stats considerably. I may have to build an improved set of limbs, but we should be posting some longer strings of data and better video soon. Stay tuned.

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