How many ft-lbs from a "wrist rocket" slingshot?
ltl919
those
pellets sure fly fast. I have heard of people hunting pests and
squirrels with them - does anyone know how many ft-lbs of energy one of
these things can deliver?
----------------------------------------------------------------------
Please find out about rec.guns at http://doubletap.cs.umd.edu/rec.guns
John Buol
I saw some kids shooting a "wrist rocket" slingshot at a dirt pile and
those
pellets sure fly fast. I have heard of people hunting pests and
squirrels with them - does anyone know how many ft-lbs of energy one of
these things can deliver?
Step 1) Ask kids "Hey, want to see something neat??"
2) After ensuring you have a sling-shot safe backstop, set up your
chronograph. As a shooter, you DO own a chrono, right? If not, maybe you
could borrow one. They can be had for under $100.
3) Chrono sling shot pellets, as per the chrono manufacturer's
instructions. The chrono gives you velocity in feet per second. Weigh the
sling shot pellets on your reloading scale (you DO have a scale, right? Lee
makes a cheap one for $20)
4) Compute. Mass x Velocity = momentum. IPSC, Taylor KO (and some others)
are based on momentum. To find IPSC power factor, take your scale reading
(in grains) and multiply it by the chrono reading (in feet per second) and
divide by 1000.
125 and above makes "Minor" This is 9mm, .38 Special, etc.
175 and above makes "Major" (.45 ACP, hot .40 S&W, etc)
165 used to make major. Bowling pin shooters run in the 200+ range.
My guess is a powerful sling shot would probably make "Minor" at least.
John
--
**************************************
Play the best new shooting game for hunters!
http://www.huntershooter.com
in...@huntershooter.com
Paul Cassel
-paul
ltl919 <ltl...@newsguy.com> wrote in message
news:7pe0d0$890$1...@xring.cs.umd.edu...
> ...
SLOW_...@webtv.net
However if you use mag-safe .5 grain fragmenting pelets you can get
98.99% one shot stops. SCI (slingshot controle inc) is working overtime
to get these deadly weapons out of the hands of children. Acording to
historical reports, even a small child could take down an armored giant
with one of these...assuming corect shot placement. We must ban these
now...do it for the giants! The news media recently discovered a
particulrly deady load for this weapon. Its a high powered, teflon
coated, armor peircing, heat seaking, hollowpoint pellet called the
black hippo. It is rumored to be able to punction body armor, steel
plate, and concrete walls. Clearly this pellet was developed with one
purpose..killing. Together we can get this weapon of mass destruction
off the streets. This is clearly not what the founding fathers had in
mind. They had no idea of the technilogical advances the rubber band
industry would make
Sorry...i dont have any real info for you....just feelin kinda froggy.
Good question though.
Jason
david renner
know it's mass, then the kinetic energy equals 1/2 massXvelocity squared.
damn, its hard to write formulas on keyboards!
btw, that formula works for anything that's not moving at near lightspeed.
----------------------------------------------------------------------
boyd
> ...
I'm going to guess and show how to calculate it.
Assume the projectile weighs 200 grains. Assume it's traveling 250 fps.
The equation is:
energy = weight * velocity squared
--------------------------
450400
where energy is in foot*lbs
weight is in grains
velocity is in feet/second
so for the guess:
27.7= 200* 250*250
-----------
450400
28 ft*lbs is better than most air rifles but a lot less than a .22LR.
Weigh, measure the velocity, and find out for sure.
--
Lou Boyd
FCSA-GOA-NRA-JPFO
Article II: A well regulated Militia, being necessary to the security of
a free State, the right of the people to keep and bear Arms, shall not
be infringed.
James E. Bragge
new chrony. then i made the mistake of using it with my 308 with the 12x
scope. the chrony looked like a blob from 10 feet. the first shot was too
hight to clock. the next one was ok, the third was so close it cause the
chrony to move a bit. you can guess where the fourth one went. to this day
i have not told my wife the real reason i have not used it a second time.
Be careful how you aim a wrist rocket at a chronometer.
RB
# 2) After ensuring you have a sling-shot safe backstop, set up your
# chronograph. As a shooter, you DO own a chrono, right? If not, maybe you
# could borrow one. They can be had for under $100.
#
# 3) Chrono sling shot pellets, as per the chrono manufacturer's
# instructions. The chrono gives you velocity in feet per second. Weigh
the
sleepy
that keep tipping over the trash cans!!! The answer to your question would
vary so much as to be almost unanswerable. You would need to know the
weight of the projectile, the strength and length of the bands, how far you
pull back... Do your own experiments by shooting tin cans, junk cars, stray
dogs... I just know that I would not want to be hit by anything that flies
out of a wrist rocket. I have whacked strays with mine that made noises
that I had no idea dogs could make. Just make sure that whatever you hit
with it deserves what it gets!
Paul Cassel <pca...@rt66.com> wrote in article
<7pev93$6hu$1...@news.rt66.com>...
> ...
Golfnhead
#
# Don't know the numbers, but they'll definitely put the hurt on stray dogs
# that keep tipping over the trash cans!!!
I know a wrist rocket shooting a .44 cal round ball will destroy
the back window of a junk 61 Chevy pickup at over 50 yds :-)
I also use it for duck hunting. If you see a bunch of ducks go down
in the weeds just out of range, lob a rock into the flock and they
most likely get up again perhaps giving you another chance at em.
Im my opinion, the .44 cal ball is THE most lethal WR ammo around.
--
My opinions are my own and in no way reflect my employers!
remove spam to reply
The Polymath (Jerry Hollombe)
|Marshall and Sanow put it at 2% one shot stops with 4.5 grain pellets.
|However if you use mag-safe .5 grain fragmenting pelets you can get
|98.99% one shot stops. SCI (slingshot controle inc) is working
overtime
Not as funny as it sounds. They _are_ banned in England, for example,
and have been for decades.
The Polymath (aka: Jerry Hollombe, M.A., CCP, CFI)
http://www.babcom.com/polymath/
http://www.babcom.com/gla-mensa/
Query pgpkeys.mit.edu for PGP public key.
Chris MacClellan
So my 454 Casull shoots a 300 grain head at 1750fps equals 2040 ft-lbs of
energy!!!!!!
Chris
JerryO
# I saw some kids shooting a "wrist rocket" those
# pellets sure fly fast.
# does anyone know how many ft-lbs of energy one of
# these things can deliver?
***********************************
I thought energy equals force times distance.
Kids probably pull about 1 foot with a max force of 30 (15 ave) pounds.
also rubber has a rebound effeciency of about 70%.
1 times 15 times .70 equals 10.5 foot-pounds.
An adult with a bow aught to be 1.75 feet by 30 pounds ave by .9 eff.
for about 48 foot pounds.
--
JerryO
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Brent & Tina Blanchard
a nice bright overcast day and could get ZERO readings. Probably too
sloowww for the PACT unit I was using (it worked fine with .38s & .357s).
Big rocks, small rocks, light rocks, dark rocks all the same.
I was *saving* the reject cast bullets for when I would get real readings.
Way back in my high school days, I did a science project to build a
ballistic pendulum (IPSC was just invented and there were no readily
available skyscreen chronos, and printed curcuit-paper screens attached to
an ocilloscope were a 110VAC endeavor). I recall computing about 9 ft-lbs
with either 200-gr H&G SWCs, or with .54 round balls.
I've heard that up to a limit, the max velocity is determined by the bands
themselves, not the projectile weight. They slow down a bit with really
heavy stuff like the 1 inch steel balls I would sometimes lob... Those
things actually produce recoil!
boyd wrote:
> ...
Andy J.
years.
Andy
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dood...@my-deja.com
JerryO <jd...@my-deja.com> wrote:
# ltl919 <ltl...@newsguy.com> wrote:
# # I saw some kids shooting a "wrist rocket" those
# # pellets sure fly fast.
# # does anyone know how many ft-lbs of energy one of
# # these things can deliver?
# ***********************************
# I thought energy equals force times distance.
#
actually that's work, not energy. Energy is either potential or kinetic
(in as applied to this case). Units of energy are the same whether it's
kinetic or potential)
Ek = 1/2 * mass * velocity^2 (lbs-mass * (ft/sec)^2)
Ep = mass * gravity * height (lbs-mass * (ft/sec^2) * ft )
or (lbs-mass *(ft/sec)^2)
or (lbs-weight * ft)
the last units are what's normally used
Hope that helps.
John
KMiddle532
#I know a wrist rocket shooting a .44 cal round ball will destroy
#the back window of a junk 61 Chevy pickup at over 50 yds :-)
#I also use it for duck hunting. If you see a bunch of ducks go down
#in the weeds just out of range, lob a rock into the flock and they
#most likely get up again perhaps giving you another chance at em.
#Im my opinion, the .44 cal ball is THE most lethal WR ammo around.>
I use .36 cal in mine, shoots much flatter,
and inside 50 yards I doubt that you'll see much differance in terminial
preformance.
I hit a rabbit with one @ 30 yards one time,
it jumped about 3 feet off the ground and took off at a dead run, it made 40
yards and collasped, I found both shoulders shattered.
Another time, as a youngster, I drilled one of my brothers in the chest with a
marble
@ 50 yards +/-.
He went down so hard that I thought that I had killed Him.
Sure got My ass tore up good for that one!
KM
If you ain't gonna cook, stay away from the stove!
Doug Owen
"The Polymath (Jerry Hollombe)" wrote:
#
#
# Not as funny as it sounds. They _are_ banned in England, for example,
# and have been for decades.
#
Very little to do with weapons of any sort is funny there. Last time I
was there, a lot of years back, the punks were gluing half naked victims
to underground ('subway') walls with super glue. There were signs all
about telling you what to do if you saw a package that might be a bomb,
emergency stop buttons on escalators and the like complete with signs
warning of big fines for hitting them for fun.
Truly sad to see how far it's possible for a 'reasonable' society to
slide. From a point where gentlemen went armed and protected unknown
women from road agents and lesser perils to their modern soccer fans...
One can assume we're following as we adopt their enlightened views.
Some role models.
Doug Owen
John Rathfon
times the velocity( in fps) squared.
Force(ft-lbs)=.5*m*v^2
Brent & Tina Blanchard <bbl...@anv.net> wrote in message
news:37BD2009...@anv.net...
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on
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Gunner
> ...
Kmart and Walmart both sell them here in Kalifornia, usually in the
same section as the BB guns and pellets and bbs.
Gunner
> ...
http://userzweb.lightspeed.net/gunner
JerryO
I LOVE IT !!!
Start by saying 'force times distance' is wrong and after several
formulas I don't care about, says the normal is 'force times distance'.
Back in the 50's, our high school science taught that work and energy
used the same units and were therefore (generally) interchangable. That
is the work to stretch the rubber bands equals the energy stored equals
the energy given up by the rubber bands. All transfers are subject to
the energy (which is conserved) being lost to heat.
JerryO
*************************
dood...@my-deja.com wrote:
# In article <7pjkvh$r4v$1...@xring.cs.umd.edu>,
# JerryO <jd...@my-deja.com> wrote:
# # ltl919 <ltl...@newsguy.com> wrote:
# # # I saw some kids shooting a "wrist rocket" those
# # # pellets sure fly fast.
# # # does anyone know how many ft-lbs of energy one of
# # # these things can deliver?
# # ***********************************
# # I thought energy equals force times distance.
# #
#
# actually that's work, not energy. Energy is either potential or
kinetic
# (in as applied to this case). Units of energy are the same whether
it's
# kinetic or potential)
#
# Ek = 1/2 * mass * velocity^2 (lbs-mass * (ft/sec)^2)
#
# Ep = mass * gravity * height (lbs-mass * (ft/sec^2) * ft )
# or (lbs-mass *(ft/sec)^2)
# or (lbs-weight * ft)
#
# the last units are what's normally used
#
# Hope that helps.
#
# John
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----------------------------------------------------------------------
Robert Fahey
John Rathfon wrote:
> ...
Mass is in "slugs", weight in lbs divided by 32.2 ft/(secXsec)
> ...
force is measured in lbs, ft-lbs measures energy here
> ...
Ziemianski
Andy J. wrote in message <7pl61l$3kl$1...@xring.cs.umd.edu>...
#Hey, where can we get one of these? I haven't seen them in stores for
#years.
#
#Andy
Got one at Wally World a couple months ago.
Do not tell them what you want it for,heard one gent say he was having a
problem with cats and she would not sell it to him.
When my turn came i didn't give her an answer.
Dennis
WJS/wi/usa
know the weight of the projectile in grains. Once you determine all that
the formula is:
VxVxM/450240=E
V=Velocity in feet per second
M=Mass of projectile in Grains
E=Energy in foot pounds.
If you have a pellet weighing 14.3 grains and push it out at 950 feet per
second you get 28.66 foot pounds of energy. (950x950)x14.3/450240=28.66
HTH
__________
WJS/wi/usa
WVanhou237
<MN....@sd5.mailbank.com> writes:
#I know a wrist rocket shooting a .44 cal round ball will destroy
#the back window of a junk 61 Chevy pickup at over 50 yds :-)
#Im my opinion, the .44 cal ball is THE most lethal WR ammo around.
#
Having been stationed at Fort Sill when I was playing around with a
Wrist Rocket I was able to pick up lots of the old "cannister" balls
the Artillery used at one time. They were somewhere about .50 cal.
and and fairly soft lead. Great WR ammo.
Bill Van Houten (USA Ret)
Nothing that is politicaly Right can be Moraly wrong.------ Th. Jefferson
Osmo Ronkanen
John Rathfon <jr...@preferred.com> wrote:
#The correct formula, if one knows the velocity, is .5 times mass(in pounds)
#times the velocity( in fps) squared.
#Force(ft-lbs)=.5*m*v^2
That works with mass in kilograms and velocity in meters/s. If you use
above units you have to scale by 0.3048^2*0.45359237/1.35581795 =
0.03108095. Also energy and force are different things.
Osmo
Doug Owen
This has been a fun discussion, for sure. Several interesting points
were raised by not fully discussed. Thus far nobody (except me) has
done it, and you'll have to wade through the following to find the
answer:
Of the things I find most interesting is the idea that you can estimate
it by the energy stored in the rubber bands. Of course! How
insightful. Except we have to consider it's only 30 pounds or so when
fully stretched and lessens as the round speeds up. That is we can only
take advantage of part of that apparent energy. My tests would seem to
confirm this.
Someone posted the opinion that velocity would be fairly constant with
large changes of mass. This too seems to agree with experimental
results. I suspect it's related to the rubber band issue above.
There was considerable discussion of how to compute this interesting
(but relatively unimportant) value. This includes a discussion of mass
as opposed to weight (where it's true that slugs are the right unit, but
pounds the way we're likely to measure it). It would seem this can be
simplified if we agree to confine our tests to the surface of *this*
planet and avoid parallel universes all together. Also there was
considerable discussion as to wanting or not wanting the .5 factor, and
what units to use. This all seems to be taken care of with the 450,000
factor in the formula Boyd suggests below (and indeed the common one):
boyd wrote:
#
# I'm going to guess and show how to calculate it.
# Assume the projectile weighs 200 grains. Assume it's traveling 250 fps.
#
# The equation is:
# energy = weight * velocity squared
# --------------------------
# 450400
# where energy is in foot*lbs
# weight is in grains
# velocity is in feet/second
#
# so for the guess:
#
# 27.7= 200* 250*250
# -----------
# 450400
#
# 28 ft*lbs is better than most air rifles but a lot less than a .22LR.
# Weigh, measure the velocity, and find out for sure.
#
There was also some cautions not to actually shoot the chronograph in
one's enthusiasm to get the truth. Fortunately, having done this a lot
of years ago, I knew to take this excellent advice.
At last, retiring to the back yard, I sent a dozen or so assorted rounds
over my brand new "Chrony", an excellent deal at $50 for the factory
rebuilt unit I might add. This saved having to set up one of my other
(not here and all more cumbersome) units.
The results were 130 to 140 fps, give or take, for rounds from the 16
grain steel shot right up through 158 grain .38 SWCs. Yea, the heavies
read on the low end (some in the 120's) but given their ten times
greater mass, it's fairly clear what's happening. This at a few feet,
although at this speed the ballistics program indicates little loss
close in.
I make it 'less than 10 fpe' for most rounds. A bummer to get hit with,
but hardly fatal by most standards. The estimate of 250 fps above (when
squared) gives a much larger estimated energy than I think is there.
A survey of damage to the fence seems to support this. Dents seem to be
'sub pellet gun' in terms of broken wood fiber.
As an aside, I think the lady that refused to sell the evil assault
slingshot to the guy that *might* shoot a cat needs to loose her job
(and before the flames start, I'm a cat lover, although I guess I love
liberty more than I'd support this BS). Consider what would have
happened if she'd refused to sell condoms to a gay man or a single one
who might visit a prostitute. As the song goes, 'minding other people's
business seems to be so high tone'.....
So there ya go.
Doug Owen, on a slow afternoon.
JerryO
#I make it 'less than 10 fpe' for most rounds.
#Doug Owen,
************************************
Thanks, for resolving this.
Especialy since it is so close to the 10.5 ft lbs I estimated from the
energy put into the rubber bands.
If only we could get more out than we put in, as seems to be implied in many
of the responses, but it is well know that the ft lbs of work done by a
spring can't exceed the ft lbs of work stored as energy in the spring.
Doug Owen
JerryO wrote:
#
# Doug Owen wrote
# #I make it 'less than 10 fpe' for most rounds.
# #Doug Owen,
# ************************************
# Thanks, for resolving this.
#
# Especialy since it is so close to the 10.5 ft lbs I estimated from the
# energy put into the rubber bands.
#
Glad you like it.
You seem to have missed a very important point, the energy loss varies
from nearly nil with very heavy rounds, to almost all for very light
ones. Like I said, 'insightful' but other factors dominate.
# If only we could get more out than we put in, as seems to be implied in many
# of the responses, but it is well know that the ft lbs of work done by a
# spring can't exceed the ft lbs of work stored as energy in the spring.
#
Not until someone tennifer coats one.....
Doug Owen
Brent & Tina Blanchard
around in the mid-70s?
Those suckers would HURT if you were in too big of a hurry to shoot after
installing them--and one side snapped off the prong when you're at full
draw! Tried to buy so-called surgical tubing in college one day, but the
chem supply lab staffer was wise to our intended and disapproved purposes.
Rats!
Ziemianski wrote:
> ...
Robert Rexford
locations...
JerryO
Doug Owen wrote
#JerryO wrote:
##
## Doug Owen wrote
## #I make it 'less than 10 fpe' for most rounds.
## #Doug Owen,
## ************************************
## Thanks, for resolving this.
## Especialy since it is so close to the 10.5 ft lbs I estimated from the
## energy put into the rubber bands.
##
#
#Glad you like it.
#
#You seem to have missed a very important point, the energy loss varies
#from nearly nil with very heavy rounds, to almost all for very light
#ones. Like I said, 'insightful' but other factors dominate.
#
#Doug Owen
Why do you think the energy loss is almost nil for heavy rounds? I believed
the energy loss would always equal or exceed 30% and therefore used a 70%
efficiency factor (I considered using 50%, but did try to show a max value
as other estimates were way higher than the energy input).
As a kid, I was told the best rubber had a 30% energy loss in the process of
compression and expansion, hence a solid rubber ball would only bounce to
70% of its height. Then came super balls.
Is the rubber used in the wrist rocket really that good?
Also for simplicity, I assumed the projectile would be a reasonable weight
(on the heavy side). I then ignored the dynamics of the rubber, the weight
of the projectile holder, and the air resistance of the whole works. The
weight of the projectile holder (and rubber bands) could have been estimated
and proportioned to the projectile as a simple ratio.
Remember we were asked about a specific kid useing we don't know exactly
what so all answers are really based on many assumptions, includeing how
strong his rubber bands were and how far he could pull them, and if he was
shooting stones (light with a specific gravity of about 2.2) or steel
(specific gravity around 8.0) or even lead (specific gravity around 11 with
some tin and antimony added). Hopefully we can rule out the denser uranium
projectiles.
I also guessed at the weight of the draw and the length of the pull. How
did you decide what wrist rocket to use and how far to pull it. How did you
verify these are similar to what the kid was doing?
You seem to imply my answer is wrong because I don't understand something.
Like maybe I thought a grain of sand would give the same energy as a 180 gr
.50 caliber ball.
I knew much lower numbers exist (down to zero when the projectile has no
weight). But intended to show a resonable upper limit (likely slightly
higher than the kid would really achieve).
Keith A. Flick
JerryO wrote in message <7pv79i$4fm$1...@xring.cs.umd.edu>...
> ...
of
> ...
estimated
> ...
Part of the energy loss (as far as the projectile is concerned) if related
to the ratio of the mass of the projectile to the mass of the band and cup.
The energy taken out of the bands has to accelerate the projectile, bands
and the cup to the same speed. The heavier the projectile the more of the
total energy is added to the projectile (because of the lower total speed)
since the bands do not have to be accelerated to as high of a speed.
> ...