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Sunday morning found me in the mood for something heavy.  This little fellow comes in at 8,889 grains,  (576 grams).

At 44″ long,  it makes a credible walking stick for those late night strolls in the garden.  Jeeves is miffed he doesn’t have one too.

Dad’s old army helmet gets dwarfed by this quaint little retro stick.  If it works (find out tomorrow) it would have been just the thing for impressing the natives.  Big, ugly pointy thing that it is,  the Romans would have loved it.

Testing commences first thing Monday morning.

I have been mulling over what kind of qualities I want in a bolt made strictly for testing purposes. ……That’s easy:  be accurate,  long lived, and not have any complex to manufacture features.  Also the shafting material should be available for inspection before purchase in order to obtain straight specimens.  Hardwood broom handles are probably still the favored material due to their relative ubiquity.   Dura Europos style bolts have proven pretty fragile in the past and will not be suitable for this round of testing.

Note to self:   A  blunt point has much to recommend it in terms of retrieval.  Also easy to fabricate with pipe, plug and weld.  Accurate and expedient is the ticket for now.  The pitch of the bolt is vital for proper take off from bolt groove.  Can experiment by applying suitably sized band of masking tape on the shaft right behind the head to control up-pitch, place at rear to produce down pitch, i.e. Dura config.

Balance is not always where you expect it.    Sometimes the sweet spot jumps out at you.  More likely, though, you have to dig for it a bit.

At least until they are not.

Shot #12 just in.   299 fps  with a  6867 grain bolt for 1,363 foot pounds of projectile energy.  Firefly’s pep with these Mk VIII limbs seems identical to what it was 18 months ago when we were puncturing propane cylinders and the like with those fatally flawed paddle limbs. If our only net gain is to be able to achieve that level of performance with limbs that hold up for hundreds of shots, I’ll consider that a big win.

Roughly speaking, it seems that an increase of 200 lbs in the draw weight is yielding an additional 25 feet per second with this particular bolt.  This seems to be true whether that increase is created by engaging a longer draw length or by increasing the washer tension.  Both scenarios have been tried and have similar effects.  While I don’t plan on taking Firefly up to 5,000 lbs as we did before,  it seems reasonable to think that we would be getting 350 fps if we did.

300 fps is plenty for our purposes.  I’ll seek no more velocity until I’ve seen what accuracy can be achieved with what we’ve already got.   Time for a new paradigm.  First up,  a new style of bolt.

The new MK VIII limbs are proving themselves different from all the previous sets we have tried in that they don’t make any creaking sounds while under load.    Also, the vulnerable end grain at the highly stressed base of the limb is showing no radial cracking as before.    Encasing the wood on three sides in these family sized irons may just have done the job.  Now the trick will be to see how much performance we can coax out of them by better tuning.

If I can get enough of these low power shots under my belt I may be able to find the confidence to increase the draw length by a few inches.   I must admit to dogging the proceedings a bit by taking considerable time to screw my courage up for each shot,  being in fear that something will fail again and my beautiful illusion about a “finished” Firefly will be crushed under the whim of the you-know-whos.     Faith is such an arbitrary mistress.

Port top (PT) gets another 7 1/2 degrees of rotation induced by this very powerful spanner set up.

Below, port bottom (PB)  gets the same treatment.  Balance is near.

This relatively low power 219 fps bolt took a tumble in the sand.  The tail end of the shaft sat up and stopped fast enough to do itself this much damage.   The tip was found burrowed a foot into the sand,  kinda like an ornery ostrich.

I suspect Dura type bolts would be particularly prone to this type of shaft breakage given their greater mass in the tail.

The shaft material of this bolt is something known as “Bamwood”.   Basically it is just a low cost, laminated bamboo broom handle,  mass produced in (let me guess) China.   It is, perhaps, not an ideal analog for a Roman ballista bolt.  But we do have to start somewhere don’t we?  Just like with bowstrings.  Not perfect at first, but at least cheap enough to suit the current level of  experimentation.

Don’t you just love executive decisions?

The first 4  shots are done with a 7,000 grain bolt with a 6 1/2″ quadrobate tip.  Velocity readings were taken with a RADARchron,  microwave based, Doppler chronograph.  Accuracy +/- 2%.  All shooting is done at 55 yards (50 meters) unless otherwise noted.

Shot #     Velocity                Comments

1               204 fps   ??            I was pretty well disorganized for chronographing this first shot.   Reported by memory that this shot was 240 fps.     Now think that I transposed the 4 and the 0.  My bad.  Corrections made.

2              190  fps                    Very weak due to leaving it cocked to stretch the bundle.  Limb can be hand pulled 1/2″ off stanchion at rest.

3              210  fps                     Started torsioning sequence by adding 7 1/2 degrees all around.   Draw weight 2900 lbs.   Limb can be hand pulled  3/8″ away from stanchion at rest.

4              219 fps                     Now at 15 degrees past starting point.  (i.e. +15)  Limb can be lifted 1/4″ off stanchion by stout hand pull at rest.  Draw weight 3300 lbs.  Starboard limb shows to be tracking above its target plane of movement.    Will introduce some asymmetrical tightening to train it into position.  Top half of starboard bundle will receive additional torsion.

Let’s reorganize this presentation a bit:

Shot #    Velocity.   Draw Weight.    Draw length.   Washer rotation & comments.

5                220 fps            3400                     44″                Starboard top +22 1/2 degrees, the rest at +15.   Limb can still be hand lifted 1/8″ off of stanchion.   We are now using a different style of bolt.  Weight 6867 grains, 26 1/2 long,  1 1/2″ flat tip.   All following shots will be performed with this bolt until announced otherwise.

6        177 fps     3300 lbs      44″     ST + 30,    SB +22 1/2,  PT +15,  PB  +15.    (ST = starboard top.  PB = port bottom.  etc.)   This shot was wildly out of balance with the starboard side limb perhaps  retarded twenty degrees behind the port side limb due to its stiffer resistance.  The shot flew far left, about 10 feet at fifty yards.   Velocity clearly terrible.  Bowstring rates as loose,  with noticeable slop and zero twang in the at rest position.

——-  A  tight string is key to speed.   A ballista with a loose string has a dull and thudish sound to it.  One with a tight string emanates a much higher tone.  ———

For obvious reasons,  I am holding off shortening this string until the torsioning sequence is complete.

7       205 fps    3600 lbs    44″     ST= +30, SB +22 1/2,   PT +22 1/2,  PB +22 1/2.     Bow string is too loose.

8       201 fps     Rest same as above.

9      196 fps      Rest same as above.  Torsion balance in these last 3 shots was excellent.  Bolt leaving machine directly over the bolt groove.   All three shots were casually aimed yet grouped inside a one foot circle at fifty yards.  Remarkable  given that the bolt flight appeared imperfect,  with a noticeable tail waggle for the last twenty yards.  Bowstring slack and needs to be shortened by at least 1″ before continuing.   No longer possible to manually pull the limb away from the stanchion at all.   Mk  VIII limbs rate as nominal.  Zero strain damage evident.

10     251 fps    4050 lbs  44″   All positions +30.  Bow string complete bollocks.  Bolt too short by perhaps 6″.    However, the bundles are nicely balanced and the bolt lifts off directly over the bolt groove.  The limbs track A-Okay inside their target planes.   Previous trials with Firefly have shown that if we increase the draw weight to 5000 lbs  we can reliably get velocities of around 320 fps with a 7,000 grain bolt .  If I can get these heavier (and seemingly reliable) limbs to kick out a steady 300 fps with 7,000 grain bolts,  then  the power levels will be  sufficient to conduct some serious accuracy trials.  Only accurate ballistas are interesting.  Sorry Whelan.

11     275 fps   4o50 lbs   44″   All positions +30.  Only change over the last shot was that I shortened the bowstring by about an inch.  String is noticeably more taut in the at rest position.  Need to order more double braid for some strings.  Desperately need to make more bolts.    Limbs happy.

12     299 fps   4250 lbs   46 1/2″  All positions still +30.   The extra 2 1/2″ of draw length I included this time seems to have boosted us into the velocity envelope I want for this next series of tests.  Limbs remain trouble free.  Bolt and string still very much sub-par.  Hand cocking to this length and weight of draw is quite a chore for one average man to handle.  I’m betting a machine this size had a minimum of two really strong, big guys,  at the levers.

A brief pause ensues while I make some more bolts and dream about strings…….

13   200 fps 4100 lbs   44″  All +30.    New bolt was tried.  Weighed in at  8889 grains.  Christened “Little Walloper”.   Power  down probably due  to loop slippage in bowstring.

14    285 fps   4100 lbs   44″  All   +37 1/2 degrees.  Old bolt that weighed 6867 grains Bowstring shortened by 1 1/2″ and holding firm.  Starboard limb tracking high;  believe may be related to the waggle tailed bolt flight.  May need to try longer shafts too.

15   210 fps  3700 lbs  39 1/2″  All +37 1/2 degrees.    This shot made with “Little Walloper”, 8889 grain bolt.    I am not convinced that increasing the weight of the bolt is actually picking up any more foot pounds of energy.  I will make up three new bolts (5,000 grain, 7,000 grain, and 9,000 grain) .  Firefly finally seems to be reliable enough for some extended experiments.

16   287 fps  3700 lbs  36″ draw length.   New bolt that weighed 6,651 grains.   ST +45 degrees, SB 30, PT +37 1/2, PB +37 1/2.  The starboard limb is tracking better after tightening the top and loosening the bottom of its spring bundle.  Bolt flight was good.   Draw length shorter than previous shot #15,  yet pull weight is the same.  Go figure …. that kind of thing happens after adjusting the bundles.

17    245 fps  3700 lbs  36″ draw length.  This shot made with “Little Walloper”.  Bolt flight good.

18    260  fps  3700 lbs 36″ draw length.  Back to the 6,651 grain bolt.  Bolt flight excellent.

19   258 fps  3700 lbs  36″ draw length.  Same as above and also went through the same hole as the previous shot.

20  208  fps  3400 lbs  33 1/2″ draw.  6,651 grain bolt.   Hit about 1 foot below aiming point on cardboard target.  Range is fifty five yards and I will attempt to shoot a group.  Velocity is low due to reduced draw and pull weight.  Suspect the loops may have slipped again.

21  210 fps  3400 lbs  33 1/2″ draw.  6,651 grain bolt.  This shot struck three inches to the left of the previous shot # 20.

22  205 fps  3400 lbs  33 1/2″ draw.  6,651 grain bolt.  This shot disappeared into the same hole made by shot #20.

23  185 fps  3400 lbs  33 1/2″ draw.  6, 651 grains.  This shot went through same hole as shot # 20 & 22

24  196 fps  3400 lbs  33 1/2″ draw.  6,651 grains.  This shot went through the same hole as #20 & 22 & 23.   Accuracy at this power setting is outstanding.  The limbs are finally tracking in their proper planes and the bolt flight looks near perfect.  Couldn’t be happier with these last five consecutive shots at fifty five yards.

25   282 fps  3400 lbs  33 1/2″ draw. 6,651 grains.  ST +52 1/2 degrees, SB 37 1/2, PT +45, PB +45.   All positions have been advanced by 7 1/2 degrees.  That appears to be all it took to boost the velocity by 80 fps.  Also, this is the first shot after the sights were adjusted to move the group onto the bulls-eye.   Some good luck going on getting that right.  Drilled it.

26   278 fps 3440 lbs 33 1/2″ draw.  6,651 grain bolt.  Decided to spice things up a bit by taking a bead on that coconut that has been waiting patiently in the fridge these last nine months.  Click for vid.  20111015144301(2).    All these shots have been witnessed by the Rebecca.  More witnesses will be needed for the work that is to come.    There is just too much work to have gotten this far, to have it questioned by an unverified reporting of the facts.

27   283  fps   3400 lbs  33  1/2″ draw.  6,651 grain bolt.  First sighting shot of the day.  Struck 2″ right of where intended.  My flub.

28   279  fps   3400 lbs  33 1/2″ draw.  6,651 grain bolt.  Second sighting shot.  Drilled it.

29   286  fps  3400 lbs   33 1/2″ draw.  6,651 grain bolt.  Showtime!  Nailed the cone.  Can’t believe the Gods are being this good to me.

30  274 fps   3350 lbs  33 1/2″ draw.  6, 651 grain bolt.  Sighting shot on original group.  They just keep disappearing into the hole from the previous shot.  I am a dyed in the wool target shooter from way back, and I must say, this string of shots is really quite extraordinary.  The limiting factor on the accuracy of this machine, appears to be the precision with which I can align its sights.  Group size is match grade.  Overall size of this 11 shot string is 3″, range 55 yards (50 meters).   However the last three shots have literally gone through the same hole.  This phenomenon is obviously a gift from the Gods and I am resolved to make not the slightest change in her tuning.  I have  fabricated and tested over fifty  flintlock firearms, many modern, and not so modern, rifles and pistols,  and I must say, (keeping in mind her obvious limitations as a catapult) shooting  Firefly reminds of the very best target grade weapons I have tested.  Absolutely extraordinary.

…But I digress.

31  269 fps  3350 lbs  33 1/2″ draw.  6.651 grain bolt.  That makes the last five through the same hole.  I went to the doctor today and my blood pressure is uncharacteristically high.  These last few days have been very jacked for me.  I know this sounds like hyperbole, but I am literally getting a sustained adrenaline dump from all this success.  Sorry to be such a boor, but I just feel like a door that I’ve been knocking on for a very long,  has suddenly opened.   I’m blinking a bit.

32  270  fps  3350 lbs. 33 1/2″ draw.  Ditto.  This is getting weird.

33  215 fps  3350 lbs.  33 1/2″ draw.  Needed a change. This shot made with “Little Walloper”.   Hit low from the previous shots by a couple of feet.  It looked a bit ponderous.  BP down.

34  210  fps  3350 lbs.  33 1/2 ”  draw.  No zip, trajectory noticeably curved.   Boring.

35  270 fps  3350 lbs.  33 1/2″ draw.  I used a new style bolt here.  Weight is 6,693 grains. Fins are a bit longer, with a classic angled rear end.   It hit about 5″ above the previous points of impact.  Sights have been adjusted to compensate.

36.  N/A  fps  3350 lbs.  33 1/2″ draw.  6,693 grain bolt.  This is my second ice cream shot.  Results as follows:  click for vid.  20111021143100(1).   BP up.

37  260  fps  3350 lbs.  33 1/2″ draw.  6,693 grain bolt.  Sighting shot.  12 o’clock, 2″ from dead center.

38  263 fps  3350 lbs. 33 1/2″ draw.  6,693 grains.  Sighting shot.  12 o’clock, 3″ from dead center.

39  N/A fps (est. 260 fps)    3350 lbs. 33 1/2″ draw.  6,693 grain bolt.  This was the my first shot in a three shot string testing off hand accuracy.   1 o’clock,  2″ from dead center.  Good clean control of the aim and trigger pull.

40  N/A fps  (est. 260 fps)  3350 lbs. 33 1/2″ draw. 6,693 grain bolt.  I blinked at the moment of release,  trigger control was spotty.  3 o’clock,  4″ from dead center.  Second offhand shot

41  N/A  fps (est. 260 fps)   3350 lbs.   33 1/2″ draw.  6,693 grain bolt.  12 o’clock, 1″ from dead center.  The current sight setting is set 1 1/2″ high at 55 yards when using a 6 o’clock hold.  Bulls eye diameter is 4″.  No blink this time, follow through was right on, trigger pull nominal.  This one felt really good.  Third offhand sight.

42   N/A fps (est. 230 fps)    N/A lbs.   Ditto on rest.  Something is wrong.    No chrono reading, but velocity clearly down.   Struck in the dirt 12″  low.    String a tad slack, not so sure it was loop slippage this time.  A mystery to investigate.  I need to start adding the date to these shots.  Above four shot string done on 10/23/11.  It looks like this blog posting will be the place I come to record all the raw shooting data.

43 through 50. Various sighting shots that concluded with that trick shot picking the apple off the pumpkin.

50 through 75.   It is 11/04/2011 and this entry is a catch-up to at least record the existence of 25  sighting and tuning shots made with Firefly over the last couple of weeks.  No attempt was made to measure velocity as I need to redo the mounting bracket for the chronograph and  have yet to find a suitable way to remove the 30 second time limit for making the shot.

76      11/07/2011.  This is the first shot after realigning the stock to the field frames to remove the string/deck gap.  It hit 15″ to the left of the bull.  Port bundle, top half, needs 7 1/2 degrees more twist.

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