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The crossbow is a more complex derivative of the ancient
recurve longbow. To be an effective weapon, a longbow
requires an operator with decades of physical adaptation,
experience and constant practice. As such, the trained
archer gained social status and value befitting their worth
battlefield. Conversely, the crossbow can be
wielded by almost any disposable shambolic clodhopper.
This means a reasonably effective force can be made out
of the nearest group of low-grade troglodytes. This
explains the popularity of crossbows among the French.
To draw a light crossbow, the operator can simply pull
back the bowstring. Heavier, more powerful bows for
warfare require a separate mechanism. Stronger peoplw
would be one way, another promising direction might be to
use trained primates. I reckon a gorilla would handle 500lb
with minimal fuss and would be handy when it came to the
melee, but "Mixed Primate Archery Corp" is an idea for a
Real world mechanisms included one system that used a
loop on the front of the bow that was held down with the
foot while the string was lifted via a hook attached to the
belt. This allowed use of the stronger back/leg muscles
and therefore a more powerful bow. A second system used
a hand crank or windlass arrangement. The string could be
wound back, spreading the work load over several seconds.
The windlass arrangement could easily be modernized. The
power demands for a modern hunting bow are large but
manageable. Brief research suggests 350lb draw weight
over an average of 13" is typical for the larger end, which
is where we want to be. Converting that to sensible units
gives a draw energy of ~4800J, which if you wanted to
load in say 3 seconds requires 1600W. That is at the larger
en of "hobby grade" electric motors, so we're in business.
Those motors are big, and an electric crossbow already
exists <link> where they've clearly had to dial down the
draw weight (230lb) to compensate for the bad
So, innovation #1. Have the cocking mechanism mounted
with a spring opposing the force of the main spring system.
This will work a bit like the counter weight in a
lift/elevator system. Rather than have a brutish motor that
can lift the fullest car, have a counter weight of half the
maximum so you can use a smaller motor. Here, the
electric motor will move the cocking mechanism forward,
compressing a spring of say half the main spring value.
350/2 = 175lb in my example. It hooks the bowstring and
moves backwards with half the force coming from the
motor, half from the spring. Now you could use say a
1000W motor, get a faster draw and a much more
managable motor size.
Innovation #2. When you want to shoot stuff, particularly
stuff that dislikes being shot, the stuff seldom hangs
around at exactly the range you have your scope dialed in
for. With a rifle, and to some extent bows, you have a
projectile designed to give as consistent a flight path as
possible. To do this, they are often fired with the exact
same energy, as far as can be controlled. Then, with
calibration, you can alter the angle of the scope to the
barrel and have the object you're looking at be on the
exact flight path of the bullet.
More sophisticated guns, such as those aboard HMS
Warspite used to open the D-Day bombardments, can vary
the amount of energy given to the projectile, the
flightpath can be modified by angle and power
We can do the same with our electric crossbow. Imagine
looking down your scope and panning across a landscape
looking for stuff to shoot, as you pan, the objects in view
will be at different ranges, there might be a bush 50 yards
ahead or a collection of trees 125 yards away. The laser
rangefinder built into the scope relays the distance to the
objects you are surveying and adjusts the power of the bow
proportionally by moving the string forward/backwards
through the travel.
I imagine a cylinder/piston arrangement with appropriate
pressures on either side of the piston would make a
cleverer spring design.
*You can use this to pull some clever tricks, such as
shooting a great high arc and a shallow lob from the same
gun so that 2 shells arrive at the same time.
[bs0u0155, May 08 2017]
Air sprung bows exist...
[bs0u0155, May 08 2017]
||You know, [bs], you should take up this crossbow malarkey professionally.
||If you really wanted to reload your crossbow quickly, you could use a piston driven by an explosive to draw the string. This would necessitate carrying a bunch of small explosive charges around with you, but perhaps they could be fashioned into convenient cylinders and held in a magazine within the stock.
||Crossbows have the advantages that (a) they're relatively quiet, and (b) it's so far proved impossible to produce body armour effective against both high velocity, low mass projectiles (bullets and mortar/shell fragments) and sharp, high mass low velocity items like knives, spears, screwdrivers ... and crossbow bolts.
||Idea #1 is probably practical, but you're adding mass. The mass of a personal weapon needs to be kept to an absolute minimum. If you're going to add mass, do it as ammunition, not in the "dead" weight of the launch system.
||Idea #2; most animate stuff dislikes being shot.
||Apart from BL naval rifles, the same "high and low" trajectory trick can be done with guns like the British 25-pdr gun-howitzer (the name gives it away). Some late WW2 German equipments had the same capabilities, as do the later Bofors designs, still in service.
||You reckon ? We do OK from the used-car sales, and of course
the royalties from the adult movies are a nice bonus
||//it's so far proved impossible to produce body armour
effective against both high velocity, low mass projectiles
(bullets and mortar/shell fragments) and sharp, high
mass low velocity items like knives, spears, screwdrivers
... and crossbow bolts.//
||Really? I'd be pretty confident that a crossbow bolt
wouldn't penetrate an E-SAPI Boron-Carbide trauma
plate (and thence the SPECTRA and Kevlar backings), or
at least not one of the older Steel/Titanium
versions. The issue is with coverage I think (as with all
modern body armour) rather than resilience.
||Average folks probably don't know how much power is
represented by a number such as "1600 Watts". They need
a reference, and in this case a suitable reference is, 760
Watts equals one horsepower.
||If you attach two horses to your crossbow, there will be a lot of disadvantages.
||The best you could hope for is to use the horses to tow a ballista from place to place on a trolley. But horses are smelly, very very expensive, eat lots of bulky food and produce huge steaming piles of dung at frequent intervals, plus they get ill incredibly easily resulting in enormous vet bills.
||One horse on each side, in a kind of hamster wheel thing, to turn the winch shaft to draw the bow.
||When the bow is not being drawn, the horses can turn a generator to sell surpluss electricity to the grid.
||Nigel Calder, in The Human Brain: The brain is an organ
preoccupied with inserting little metal pieces into other
||Not necessarily metal; wood, ceramics, or rock fragments can fulfill the requirement equally well.