OT: How did they calculate velocity back in 1873?

J Miller · Post by **J Miller** » Thu Jul 21, 2011 9:52 am

OK, so just how in the world did they calculate velocity back then? No electricity, no electronics, no photo electric cells, nothing really.

How did they do it?

Joe

bdhold · Post by **bdhold** » Thu Jul 21, 2011 10:12 am

here's the abstract of the physics paper

http://www.ncbi.nlm.nih.gov/pubmed/16021765
Hist Psychol. 2005 Feb;8(1):46-78.
Physics, ballistics, and psychology: a history of the chronoscope in/as context, 1845-1890.
Schmidgen H.
Source
Max Planck Institute for the History of Science, Berlin, Germany. schmidg@mpiwg-berlin.mpg.de
Abstract
In Wilhelm Wundt's (1832-1920) Leipzig laboratory and at numerous other research sites, the chronoscope was used to conduct reaction time experiments. The author argues that the history of the chronoscope is the history not of an instrument but of an experimental setup. This setup was initially devised by the English physicist and instrument maker Charles Wheatstone (1802-1875) in the early 1840s. Shortly thereafter, it was improved by the German clockmaker and mechanic Matthäus Hipp (1813-1893). In the 1850s, the chronoscope was introduced to ballistic research. In the early 1860s, Neuchâtel astronomer Adolphe Hirsch (1830-1901) applied it to the problem of physiological time. The extensions and variations of chronoscope use within the contexts of ballistics, physiology, and psychology presented special challenges. These challenges were met with specific attempts to reduce the errors in chronoscopic experiments on shooting stands and in the psychological laboratory.

Rimfire McNutjob · Post by **Rimfire McNutjob** » Thu Jul 21, 2011 10:13 am

I'll take a guess and go with the deflection of a pendulum perhaps? If I had no electronics, that's how I would probably do it. I'll be interested to hear from whomever might have the scoop on how Winchester actually handled that back in the 19th century.

[Edit]Ooops, looks like Bulldog has the scoop on it above.

bdhold · Post by **bdhold** » Thu Jul 21, 2011 10:17 am

even better:

http://vlp.mpiwg-berlin.mpg.de/document ... _art13.pdf
(photos and descriptions of historical instruments)

bdhold · Post by **bdhold** » Thu Jul 21, 2011 10:20 am

here is a great article about 19th century ballistics
http://www.exteriorballistics.com/ebexp ... th/221.cfm

more on the Wheatstone-Hipp chronoscope
http://books.google.com/books?id=KKFCAA ... pe&f=false

Griff · Post by **Griff** » Thu Jul 21, 2011 10:51 am

bulldog,

I take it that this is a particular interest of yours?

bdhold · Post by **bdhold** » Thu Jul 21, 2011 11:24 am

no, quick google - but the science of ballistics had to be making great strides in the 19th century, or else artillery wouldn't have been so deadly. Even massed rifle fire was made more deadly through ballistics calculations/considerations.

The first shootist I ever knew was a college buddy, a physicist at Vanderbilt, also had the first pc I'd ever seen, a Commodore 64 He had written on it a ballistics program calibrated to his Winchester mod 70 .243 ('64 with 28" stainless barrel and 3/4" muzzle dia). He was a nut for crows and used to stop his car and shoot them out to 1000 yds. He carried 5 rounds with 200-yd increments.

J Miller · Post by **J Miller** » Thu Jul 21, 2011 12:01 pm

Information overload.

Unable to comprehend at this time.

Can someone translate and distil all this down for me?

IE: Shoot bullet, measure whatever needs to be measured to see how long bullet takes to get to target .... or what ever.

Joe

Post by **Hobie** » Thu Jul 21, 2011 12:03 pm

Distilled for Joe:

Whack something of known weight with something else of known weight, measure deflection and calculate backwards from there to get the velocity.

J Miller · Post by **J Miller** » Thu Jul 21, 2011 12:06 pm

Ooooo Kayyyy, That's a wee bit too distilled. Sort of like 1% milk.
But I got the idea ... sorta.

Joe

bdhold · Post by **bdhold** » Thu Jul 21, 2011 12:24 pm

reminds me of several conversations in I, Robot
Why didn't you just say that?
I thought I did.

jnyork · Post by **jnyork** » Thu Jul 21, 2011 12:34 pm

Somewhere in my early 1930's American Rifleman magazines there is an article with plans for a primitive chronograph, IIRC is has two rolls of paper a few feet apart, something to roll them with, I dunno.

I'll try to dig it out and post it.

Ben_Rumson · Post by **Ben_Rumson** » Thu Jul 21, 2011 12:49 pm

They used a device known as a ballistic pendulum... Where a precisely specified weight target was suspended on precise length rods to form a pendulum .... Then a certain weight object (the bullet) was thrown at the pendulum from a precise distance.. The amount the pendulum swings backwards gives the ballisticians a number to calculate with involving the other concerned objects weights, lengths and angles.....Like Hobie said...” Whack something of known weight with something else of known weight, measure deflection and calculate backwards from there to get the velocity.”

Rimfire McNutjob · Post by **Rimfire McNutjob** » Thu Jul 21, 2011 1:12 pm

Ben_Rumson wrote:They used a device known as a ballistic pendulum... Where a precisely specified weight target was suspended on precise length rods to form a pendulum .... Then a certain weight object (the bullet) was thrown at the pendulum from a precise distance.. The amount the pendulum swings backwards gives the ballisticians a number to calculate with involving the other concerned objects weights, lengths and angles.....Like Hobie said...” Whack something of known weight with something else of known weight, measure deflection and calculate backwards from there to get the velocity.”

That's what I was suggesting in my first post. Imagine a small container of sand at the end of a rod. The rod and the container are of know masses and known geometry. When the bullet enters the container, it's stopped in the sand in an inelastic collision at which they both are joined and swing the pendulum. The peak in the swing at which it reaches zero velocity and begins to swing the other way is the point of maximum potential energy. Given the known mass of the bullet, this energy can be used to get back to the bullet's velocity minus some amount of energy expended on the bullet during it's deformation in the sand and generating some heat from that friction. One could probably refine this method and get a decent measurement.

The Chronometer solution also listed above seems to be accurate down to the millisecond. Using that tool, one would have to space the start and stop mechanisms a decent distance apart to get a good measurement of velocity. A good bit farther than today's light based detectors on modern chronographs. However, they were probably capable of good accuracy given a reasonable distance between the begin and end signals ... say 20ft or 30ft. I wonder if there's not one of these Chronometers sitting somewhere in a Winchester museum?

Ben_Rumson · Post by **Ben_Rumson** » Thu Jul 21, 2011 1:34 pm

I've read about the Ballistic Pendulum here and there over the years, mostly in the Rifleman when such questions as Joes came up...It maybe in Hatchers' Notebook too... Not sure what Winchester used but I'd wager the pendulum rather than the expensive and perhaps temperamental German chronoscope... With the simplicity of a pendulum if you attach the firearm to it you can measure recoil too

...
More on the subject here: http://en.wikipedia.org/wiki/Ballistic_pendulum

Rimfire McNutjob · Post by **Rimfire McNutjob** » Thu Jul 21, 2011 1:40 pm

Oh wow, good find on that Wikipedia article. There's a P.O. Ackley pendulum section in there as well.

Ben_Rumson · Post by **Ben_Rumson** » Thu Jul 21, 2011 2:07 pm

Interesting too how wood was used as the bullet capture medium on the early ones I thought..

Don McDowell · Post by **Don McDowell** » Thu Jul 21, 2011 4:06 pm

Kerosene powered chronographs

adirondakjack · Post by **adirondakjack** » Thu Jul 21, 2011 5:56 pm

Hobie wrote:Distilled for Joe:

Whack something of known weight with something else of known weight, measure deflection and calculate backwards from there to get the velocity.

Yup!

Picture the "Strong man" on the midway of the county fair who could whack the lever with the mallet and cause the sliding weight to ring the bell...... Of course that thing was rigged, but the same principle applys. It's how spring scales work as well. Ya end up with "relative" readings you can compare to a "standard" load shot against yer rig to calibrate it....

But in answer of how Winchester and other makers REALLY came up with the advertized figures. In many instances they simply GUESSED/LIED because it was darned expenive and the equipment needed to challenge subject to so many vairables who could say they weren't true? MANY of the advertized claims can't be replicated today, which leaves folks scratching heads at what is different. PERHAPS what is different is we CAN tell the truth when we see it with very inexpensive gear.....

I'm thinking of claims made by Henry of their rimfire flat, for example.....

bdhold · Post by **bdhold** » Thu Jul 21, 2011 6:44 pm

that makes a lot of sense - if you can measure momentum and know the mass of the slug, then you've got the velocity.

Beaker · Post by **Beaker** » Thu Jul 21, 2011 7:27 pm

In college one of the experiments I did in Physics was this very thing with the "Blackwood Ballistic Pendulem". But that was over 30 years ago now.

Sarge · Post by **Sarge** » Thu Jul 21, 2011 8:08 pm

They knew the speed of sound in the mid 1600's and thousands of feet may be measured. Perhaps seconds elapsed for the bullet to travel a known distance?

J Miller · Post by **J Miller** » Thu Jul 21, 2011 8:09 pm

OK, I gots it now. Thanks guys.

BAM ....................................................................................TWAPPPP.

+/%#&*+_X²"=[???]

Howz dat?

Never waz any gud at matamatiks.

Joewhoseheadiskillinghimnow.MaybeashotofSouthernComfort.

Griff · Post by **Griff** » Thu Jul 21, 2011 9:19 pm

bulldog1935 wrote:no, quick google - but the science of ballistics had to be making great strides in the 19th century, or else artillery wouldn't have been so deadly. Even massed rifle fire was made more deadly through ballistics calculations/considerations.

The first shootist I ever knew was a college buddy, a physicist at Vanderbilt, also had the first pc I'd ever seen, a Commodore 64 He had written on it a ballistics program calibrated to his Winchester mod 70 .243 ('64 with 28" stainless barrel and 3/4" muzzle dia). He was a nut for crows and used to stop his car and shoot them out to 1000 yds. He carried 5 rounds with 200-yd increments.

Teeeheeee. I did the same thing on the same 'puter, a C-64. Only I cheated, I adapted a program published in the American Rifleman... and could run any bullet I knew the BC for... even had data entry screens and decisicion screens (print tables or run different data for same cartridge. Wrote it in college for a programming class, got an A, even tho' it was only in "Basic." Never could convert it to run as well outside DOS, as I still find it much more flexible and user friendly than ANY commercial program I've tried.

El Chivo · Post by **El Chivo** » Fri Jul 22, 2011 2:25 am

I could imagine something with two linked, moving targets, the bullet passing through both, and the difference between the first and second bullet holes could be measured.

Heck, they calculated the speed of light with some manual method, turning wheels that were mounted on distant hilltops. I think that was in the nineteenth century, maybe before.

But that was before ingenuity became anachronistic.

Malamute · Post by **Malamute** » Sat Jul 23, 2011 11:11 am

Chivo has the idea of the other method I'd read of. It was a drum with paper on it that turned, and the distance between the sides of the drum and the spacing of the bullet holes related to the turning speed was used to calculate velocity.

J Miller · Post by **J Miller** » Sat Jul 23, 2011 12:14 pm

Malamute wrote:Chivo has the idea of the other method I'd read of. It was a drum with paper on it that turned, and the distance between the sides of the drum and the spacing of the bullet holes related to the turning speed was used to calculate velocity.

The turning drum method even I can understand. I'd just need help with the math.

Joe

Steelbanger · Post by **Steelbanger** » Sat Jul 23, 2011 2:04 pm

I've been digging through some books because I knew I saw a ballistic pendulum somewhere here. I found one although it isn't the one I remember, and it's in the Lyman 47th Reloading Manual, page 150. Rather than scan it I am reporting it's location for you curious folks. The explanation they printed is taken from "New Principles of Gunnery" by Benjamin Robins, 1742.

J Miller · Post by **J Miller** » Sat Jul 23, 2011 2:12 pm

Back in the late 70s we used the ballistic pendulum to differentiate between major and minor loads for our IPSC matches. It did not measure velocity though.
We'd shoot factory .45 ACP ball against it and measure the deflection as measured by an arm moving against a grid.
Then we'd shoot everything else against that recorded measurement.

So I'm familiar with the pendulum, just not all the details on how it would be used to measure velocity.

Joe

Steelbanger · Post by **Steelbanger** » Sat Jul 23, 2011 6:17 pm

Here's what Mr. Robins had to say in 1742.

"The velocity of the striking body may be determined if the pendulum, being at rest, is struck by a body of a known weight and the vibration which the pendulum makes after the blow is known."

I'm not seeing the formula to calculate velocity but I assume there is one printed somewhere.

El Chivo · Post by **El Chivo** » Sat Jul 23, 2011 11:05 pm

The turning drum method even I can understand. I'd just need help with the math.

easy as pi.

Paul Jenkins · Post by **Paul Jenkins** » Sun Jul 24, 2011 12:04 am

I made a ballistic pendulum in the 60's from P.O. Ackley directions found in his book for Shooters and Reloaders. Idid use it a number of times with .257 Ackley Imp., .357 Mag, & .25-06. Lately, with a Chrony I found the results from that homemade pendulum to have been very accurate. Of course it was very time consuming. I still have notes & calculations from 1973 and his book on reloading & wildcatting.

J Miller · Post by **J Miller** » Sun Jul 24, 2011 9:56 am

So ... if I had one of these pendulums and could figgure out the math I wouldn't need a chronograph?

OK, so how about printing some of the math that goes with the pendulum so I can get an idea of what it looks like? Just trying to get my brain's boiler to light off this morning.

Joe

Rimfire McNutjob · Post by **Rimfire McNutjob** » Sun Jul 24, 2011 12:35 pm

Most of the math is in the Wikipedia article linked to in Ben_Rumson's post. It basically boils down to this ...

The kinetic energy is 1/2 *m*v^2 which everyone is used to. If you use grains for mass and feet per second for velocity, you have to divide it all out by 7000 and by gravity. I usually use m*v^2/450450 myself where m is in grains and v is in fps. When the bullet strikes the pendulum, the target is swung back on the fixed rod and at some point comes to a stop before swinging back the other way. The point at which it reaches this peak is usually recorded in degrees of swing by some sort of wheel or pointer, etc.

Note that when it swings back, it gains height from its normal resting position. This gain in height when it reaches the peak of its swing is the point where all of the kinetic energy of the bullet has been converted completely into potential energy in the target + bullet (the bullet has to stay in the target). Potential energy is mass * gravity * height. The change in height is the sine of the degrees of swing at the peak times the length of the swing arm from the swing axis to the middle of the target. Let's do an example ...

We're going to fire a 250 grain bullet from a lever rifle in 45 Colt into a pendulum. The arm length (swing radius) is 5 feet. The target at the end of the arm is a 30lb block of wood. We'll assume the swing arm is massless but there are probably formulas for including its mass. We'll us 32.175 ft/sec/sec for gravity ... YMMV.

The bullet strikes the center of the wood block and the block has a maximum swing of 10 degrees that we measure with some sort of pointer. The gain in height of the block for 10 degrees and a 5' arm is sin(10)*5' or 0.868 feet. The mass of the block and bullet is 30lbs plus 0.036lbs for the bullet for a total of 30.036lbs. The potential energy was thus 0.868 * 32.175 * 30.036 which is 838.84 ft-lb energy. Since this is the same as the total kinetic energy of the bullet just before it struck the block, we can back that into velocity. We take 838.84 * 450450 / 250 grains to get 1,511,426 which is the velocity squared. Taking the square root of 1,511,426 gives us 1229.4 fps.

I hope I got all of this right because I'm three hard Pear Cider's into a very hot afternoon in FL and I've not taken the time to refer over to that Wiki. If I blew it, please correct me.

I think the key to accuracy of this measurement is to use a block of the appropriate weight such that you get a good amount of swing that you can measure accurately. I guessed at a 30lb block and 5 foot arm and honestly if I were actually going to build this, I would use a smaller block or shorter arm to get more swing and thus more resolution on the degree scale. Of course, if I were shooting something with substantially more energy, I might have gone with a slightly larger block.

J Miller · Post by **J Miller** » Sun Jul 24, 2011 1:35 pm

LOL, Rimfire, I could not correct you if my life depended on it. I flunked out of higher math in high school and junior college. My brain just cannot grasp it.

For instance in your formula: 1/2 *m*v^2 what does the * and ^ represent?
In the other parts m*v^2/450450 what does the / represent?

You see when it comes to higher math I AM TOTALLY LOST.

About the best I can do is take an existing formula, say for determining front sight heights, and put in those variables that change then calculate it. But only if the rest of the formula stays the same and the *^/'s are made clear.

Simply put just reading your post above made my headache worse. It makes little sense to me. I'm really sorry about that.

Joe

Steelbanger · Post by **Steelbanger** » Sun Jul 24, 2011 4:33 pm

Joe,

If you're serious about building you own chronograph, P.O. Ackley, in volume 1 of the "Handbook for Shooters & Reloaders" has all the details beginning on page 150. That is what I was looking for yesterday but only found the piece in the Lyman manual.

You should be warned that if you find packing a chronograph to take to the range bothersome, the ballistic pendulum should prove about a hundred times more difficult to transport. For example, P.O. recommends the weight of the pendulum bob be 150 pounds for heavy cartridges and 50 pounds for 22 LR and various 22 cartridges. Also recommended is to use it in a draft free room which I suppose will avoid errors of the bob moving.

Please check your PM's.

J Miller · Post by **J Miller** » Sun Jul 24, 2011 4:48 pm

Got your PM, read it and responded before I saw this response.

It's not that I find a chronograph bothersome to take to the range, I don't have one. Never have.

I was just thinking one day and it dawned on me that before electricity and electronics there had to be a way to determine velocity and I didn't know what it would be. So I started the thread.

Now a ballistic pendulum would be great if one had the property where he could set up a permanent one. No problems there. Just keep the weight constant and do the math.

Thank again for the offer.

Joe

Rimfire McNutjob · Post by **Rimfire McNutjob** » Sun Jul 24, 2011 6:34 pm

Ah .... the '*' is multiplication. The '^' is to raise to the power of another number. For example, v^2 is really v squared or simply v*v. The '/' symbol represents division so 10 / 5 is ten divided by five. I should have included those definitions. I'm so used to seeing them I take them for granted.

the telegraphist · Post by **the telegraphist** » Thu Jul 28, 2011 8:22 am

Does it really matter, it worked,who cares. They got it right, I am sure they were not hanging on the end of a chrono to see if the ballisticians got it right.
Those cartridges performed, end of story. So much BS in the world today.

J Miller · Post by **J Miller** » Thu Jul 28, 2011 8:34 am

Yeah, I does matter. I got curious how they did it way back when. I found out.

Yep, those rounds did and do work but sometimes the details are more interesting than you can imagine.
My only problem is the math. But that's been explained too, so no big deal.

Joe

J Miller · Post by **J Miller** » Thu Jul 28, 2011 8:34 am

Yeah, I does matter. I got curious how they did it way back when. I found out.

Yep, those rounds did and do work but sometimes the details are more interesting than you can imagine.
My only problem is the math. But that's been explained too, so no big deal.

Joe

Gobblerforge · Post by **Gobblerforge** » Thu Jul 28, 2011 3:39 pm

Back when I was a young'n the used to keep the numbers in the math class and the letters down the hall in the readin class. And everybody new that pie are round, cornbread's square. Just sayin.

Gobbler

BAGTIC · Post by **BAGTIC** » Thu Jul 28, 2011 6:12 pm

Sarge,

That would have given the TOF and the mean velocity but it would not have given the muzzle velocity or impact velocity. or even the velocity at any given point in the path as they didn't much understand how much drag air really caused.

KCSO · Post by **KCSO** » Sat Jul 30, 2011 12:19 am

Ballistic pendulum, made and used one for science class one time. It's simple math.

kragluver · Post by **kragluver** » Sat Jul 30, 2011 10:23 am

Hatcher's Notebook has a brief description of early chronographs (albeit not 1873 vintage!). In Hatcher's day, they used two sheets of electrically charged paper or foil placed a known distance apart, coupled to an oscilloscope or some other means of mechanically marking the time stamps when the papers were disturbed by the projectile (a mechanically rolled sheet of paper or strip chart for instance). In the old texts, you'll see "instrument" velocities quoted at 78 ft (I think that was the number). This was the mid-point between the two instrument screens or foils. This was being done as early as WW1 and probably earlier. Very clever those guys back in the analog days. Living in a digital world, its very easy to "loose" the art of analog design.