A Little Penatration... (testing a cheiroballista)

[Nerva]

Salvete Omnes!

Well we finally had a chance to dust off the Cheiro and loose a few bolts this evening (in between the downpours ). Anyway, we were trying to set up the ballistic radar and distance measuring equipment so we could begin to get some meaningful results. Unfortunately the ballistic radar did "just as it says on the tin" and went ballistic so we have no precise velocities. The old odeometer and timer did ok. The machine is torsioned to 526 lb's at full draw for these tests.

So here's the first pic. The target is at 30m and consists of a crappy old shield, 9mm ply, that should have been put down ages ago...




Here's the Cheiro primed and ready to loose...




This bolt was loosed on the 3rd last stop, I have no idea what the draw weight was other than something less than 526 lb's. It hit the umbo perfectly. The umbo on this shield was just light aluminium, about 1mm thick at most...



And another




And again...




Now here's one from the inside of the umbo...Ouch! He wont be doing DIY for a while!



And...



And here's the hole...



Here's a bolt loosed on the same setting but this one hit the wood...



And...



And from the inside...



Now here's a bolt fired on the last stop, 526 lb's or so, right through the shield, but would it have done any harm to the person weilding it? Probably not...



And...



And from the inside...



And...



And the hole...



This is one fired on the second last stop...This was actually the first bolt we shot.



And from the inside...



We finally decided to loose one off on the second stop at about 35 Deg's.. It travelled 98m. Here's a pic looking back at the Cheiro from the bolt's final position...



And then at the last stop. It travelled 162m...Time of flight was 4sec approx (give or take 10sec or so ) which works out at an average velocity of 40.5 m/sec or 133 ft/sec, but, until we get the ballistic radar working that figure is approximate. (actually it's not a radar at all. It's a laser device based on two beams at known distance).



And here's the bolt...now you know why we paint the bolt's ass red...



It's worth noting that at 520 lb's or so our machine is wound far less than maximum. Len Morgan and Alan Wilkins experimented with a machine torqued up to 680lb's. We calibrated ours earlier in the day using an electronic strain gauge in the weight room of a local gym.

Valete

Nerva