How to Photograph, Measure and Make a Cannon Field Drawing

[seacoastartillery]

     This thread will assist you in making the all-important "Field Drawing" if you want to make a cannon which closely resembles a historical one found in a park, cemetery, fort or other location like the 100 Pdr. Parrott we found in a family's backyard in Dresden, NY.

     First, we will list and show all the photos that we take to document all those details that will make your model, replica or functional recreation more realistic and interesting. There are five essential views, but we will show you all the shots we take on any gun we study and you will not lose any details that exist on the gun which has captured your interest.

     For the drawing you need only 3 tools and a loose-leaf or spiral notebook.  We usually take two medium size tool boxes full of inspection equipment when we seriously study a cannon for the purpose of creating a complete engineering drawing of it.  On this last trip to New England, we took only a 25 foot steel tape measure with concave tape, a 10 foot steel tape measure with a flat tape, and a shape duplicator and a spiral wound notebook, less than $25.00 of measuring and drafting equipment. 

Regards,

Mike and Tracy


The first two photos show why we bother to take photos at all.  Can you imagine how difficult it would be to draw all these details in the field?  You can measure the location of all these and hdw sizes, then review the photos when you get home to make sure you did not miss anything.







The first essential photo is the OAL Shot with something for scale like us.




A side view of the cascabel is helpful and reveals many breech and cascabel details.




Take a close-up of the Left Trunnion end.  The work goes on even in the rain; the photographer gets the umbrella over his head temporarily to protect the lens.




The Right Trunnion end.




We take an end shot of the cascabel which also gets some breech features like these sight hanger bosses on both top and bottom as well as the drilled center for lathe operations.



We take a top view shot of the cascabel and breech area to get other details.




We call this the "Gunner's View" shot and it gives you the relationship between any between trunnion markings and the front sight mass.  Can you see here how the US marking is in line with the sight mass?  Sometimes rear sight lines are picked up in these shots.




The muzzle shot is essential in most cases and gives you lots of markings on Rodman guns and others like Army Parrott rifles.

[BoomLover]

Thanks, Guys! Great shots, excellent info, and like the personal touch with you both in the pic, gives a good reference for size in human scale! Good job, and I'm sure the techniques will come in handy! BoomLover

[seacoastartillery]

     Thanks Boomlover; I decided to add a few more and we will do the remainder on how to use the measuring tools and get those features dimensioned on Monday night.  These  4 photos bring us up to the point where we actually start measuring ordnance. 

This is a sign on the monument's base which holds the cannon in the next few photos.  It reads as follows:  Presented to Samuel P. Ferris Post No. 61 G.A.R.  By the Howard M. Bossa Post No. 653 V.F.W. of U.S.A.  All signage anywhere near an artillery piece should always be photographed for information and possible research contacts or subjects they may present.




Here I am transferring the shape of the large reinforce radius blend via the shape duplicator to the top page of the notebook with a mechanical pencil.  Notes also go on the top page.  The bottom page contains the line drawing for the tube or carriage being studied.




We found this carton, empty, upon a supermarket shelf in Virginia.  Appropriate, don't you think, for holding cannon measuring tools?




Our cannon measuring instruments laid out on a 230 pound, 4150 steel, Round destined to become another rifled Brooke tube.




The first measurment is accomplished by using the stiff concave tape of the 25 foot tool and goes from the muzzle to the reinforce's rear face.  The Cascabel length is measured from here.  OAL is a summation of these two.  A serious technical measurement of this first dimension would involve a calibrated tape hooked to a steel square held on the muzzle face with magnets or nylon faced clamps and a 1-2-3 Block on the reinforce face at the rear to simulate that face up where the tape comes off the reinforce.  For our purpose here a little tape droop and eyeballing is appropriate and will get you very close to the actual dimensions.




     Until Monday night.

[Cat Whisperer]

AND if you note all the pictures are in a horizontal format - which lends itself well for a CALENDAR picture!

People in the pictures make them come alive.

[MikeR C]

Mike and Tracy
Thank you for including the tools and techniques for producing an accurate mechanical drawing as well as the "rough and tumble" minimum tools approach. Please continue this format. This is a very usefull thread and would apply to other large things in addition to cannons.

Thanks again for your time to post this.
MikeR C

[seacoastartillery]

     Thanks Mike, we sure have lots of fun presenting this information and we hope it will help the cannon makers out there who want to make a "stand-off" model or functional, close-to-historical cannon.  A six or ten sheet engineering drawing showing flurries of parts and blizzards of dimensions can be very intimidating to someone not familiar with that type of drawing.  Most of us can do a real good job with a line drawing and 15 or 16 dimensions. 

     The most basic of tools you can use, we borrowed from the ancient Egyptians.  Knowing your hand-span measurement can help your credibility in front of family or friends while visiting a place displaying cannon.  "How big is it?" is the first question you get.  And they are not talking about length either, it's BORE SIZE they want to know and after memorizing your hand-span in inches or millimeters you can answer those questions.

     Tomorrow night we will present some easy ways to measure difficult features on some cannons with simple tools.

Regards,

Tracy and Mike


At Old Fort Niagara we found a large siege mortar of late 1700s vintage, but "How big was it?"  Since my hand-span is 8 inches, we identified it's bore size as 8 inches.  I have an SBR half scale replica of this very mortar.




The act of measuring bore size.




At Trinity College in Hartford, Conn. we quickly identified the Dahlgren Shell Guns that we found as 9 inchers, not 11.





Almost forgot this one.  It is very helpful to take a photo which shows where you found the cannon you were measuring with it's unique surroundings.  This 100 Pdr. Parrott Rifle was found in a family's backyard in Dresden, NY and here is the "Establishing Shot" to prove it!




     Can you see how close that house is?  And this is a very rural location where most yards are huge.  A Nice sign on the telephone pole.  Note also the 8 inch mortar shells in front of the 6.4 inch seacoast and navy rifle.  Also you can see that the people who mounted this gun wanted the wrought iron rails level, not at the 3 degree forward pitch designed into the carriage!  It cost them another large marble slab to accomplish this.  Take a similar photo; you'll be glad you did.  Until Monday.







 

[Victor3]

 
     The most basic of tools you can use, we borrowed from the ancient Egyptians.  Knowing your hand-span measurement...

 Now that's 'handy.'  I carry a knife, but not a ruler.

 I never thought of measuring it. Just checked both of mine and found - to my horror - that I'm asymmetrical    Left hand 9.25", right hand 8.75".

 Hey! My foot is almost exactly.... a foot! Who knew?

 What's that someone once said about "the true measure of a man?"

[seacoastartillery]

     Tim,   We don't know about this calendar thing, thought that was closed, but every once in a while we like to share more pics and tips on getting things done.   
     
     Victor,   There aren't too many 12 inchers out there, but one we know about is right outside Admiral Dahlgren's Old Headquarters at the Washington Navy Yard.  If you get a chance to go to DC, let us know and we will meet you there take a photo of you sticking your foot down the bore! 

     Tonight we will try to present a few photos using these tools to quickly and properly get some dimensions from a variety of features from a few different cannon.  Also the done-in-the-field Rough Draft of the Field Drawing and a separate sheet showing actual shape transfers from a rifled siege gun of the type used by Confederate forces at Fort Pulaski, Georgia in 1862.

Regards,  Tracy and Mike


The lowly penny can be used for more than a tire tread depth gage.  This method for finding the width of a rifled cannon's rifling groove works, even if you have no measurement tools with you at all, just a bit of pocket change.  We place a penny in the groove against the left edge.  Then we take a photo of the penny and groove from the top.  When we get home, we make a photo or photo copy of the penny/groove subject.  We measure the penny's dia.; it is .750".  Measure the penny's image dia. It was 1.375".  Measure the groove's image.  We found it to be 2.292".  Place these values into a simple ratio formula like this:   

                                              X = Width of Rifling Groove 
   
                                               1        3               2
                                            .750" : 1.375" = X :2.292"

                                                   X = 1 x 2
                                                            3
                                               
                                                   X = 1.250

pg


This measuement should be accomplished by looking down on these features, not across to the tape which is quite distant from the elevation screw feature.  See the next photo for a better, more accurate method.




This photo shows a better method for getting this type of dimension.  You can see the various features and where they lie along the tape.




A unique use of your smaller, flat steel tape is show here.   You simply maneuver the flat tape until you have a nice circle of tape around the inside of the breeching hauser hole in this large Parrott cascabel.
 



Measuring a cylinder, in this case a reinforce on the British siege gun, is the specialty of the flat tape.  It actually measures, not the diameter like a PI tape does, but rather the circumference which requires further coputation, although a simple one.  Take the 83 and 17/32 inches and subtract one inch, because you used the one inch mark to mark the total circumference and then divide by the value of PI on your calculator or 3.1416" which is close enough.  So you get 26.27" Dia.




This method of trunnion dia. measurment is too inaccurate; use your smaller flat tape as we just did on the reinforce. 




The radius on the rear top of the percussion lock boss is captured by the shape duplicator tool on this 9" Dahlgren Shell Gun.




Here the shape duplicator gets the large radius blend at the rear where the radius ends at the origin of the hemisphere on this tube's breech.




This is a whole page of shape duplications that we pulled from a British rifle we found in New England on this last trip.




As messy as it is, this rough draft field drawing will suffice to build a nice 1/4 scale siege gun if we ever get the time to make it someday.
Sure it's easier to just buy a drawing, but there is none available on this rifle and a bunch of others in the U.S.  Besides, it's fun and there is a special sense of accomplishment when you really "Do it All" to build your own cannon!!




     Have fun!    M&T

[Cat Whisperer]

Calendar?  There will always be opportunities for the NEXT calendar.

Measurements?  When you're surprized and need some remember the 3x5 card and the standard sheet of paper 8-1/2x11.  That gets you in the ball park when you have NOTHING else.

[MikeR C]

Don't forget a US dollar bill is 6 X 2 1/2, I read this as my wife won't let me have one to measure

[GGaskill]

The problem with dollar bills as measurement devices is that they shrink as they age.

[dan610324]

in size also  ??   

[GGaskill]

 

Of the six in my pocket at this moment, the lengths are 6.15, 6.15, 6.12, 6.15, 6.12 and 6.12, but none are particularly old.

[Cat Whisperer]

How on earth could you measure one - after all they go SO FAST!

[GGaskill]

Ones are almost as useless as pennies.  Can't buy much with them.  At least the pennies have use as shims, etc.   

[subdjoe]

 Now that's 'handy.'  I carry a knife, but not a ruler.

 I never thought of measuring it. Just checked both of mine and found - to my horror - that I'm asymmetrical    Left hand 9.25", right hand 8.75".

 Hey! My foot is almost exactly.... a foot! Who knew?

 What's that someone once said about "the true measure of a man?"

A mans yard is less than a foot but more than a hand.  Something like that anyway.

[seacoastartillery]

Cannon builders,

   OOPS, almost forgot about this one. We have found an extremely useful tool that you should take with you if you go into the field to do a cannon drawing.  It is the typical carpenter's combination square.  The part that should get your undivided attention is the one foot long blade.  Used separately, it can find almost invisible junctions where cylinder shapes like the front of a 100 Parrott meets a gentle taper.  The intersection of two very, very similar tapers can be found as well.  When your drawing reflects accurately where these intersections are, you are adding important elements that coalesce into a good looking drawing which is the basis for a good looking cannon.

     The method is very simple.  On the Parrott, we knew that the cylinder/taper intersect point was between 4 and 7 inches from the muzzle face, however, in the glare of the mid-day sun, it was impossible to determine exactly where it was with our calibrated tape measure and eyeballs.  We got the 12" blade off our machinists combination square and laid it's edge, at top dead center, along the cylinder portion of the tube.  Then one must squat down and sight over the tube at the point where you believe the intersection to be.  Shade your blade as you gently slide it away from the muzzle.  Position a light colored object behind the tube/blade line like the sky, a building, dry grass field or sandy beach.  When you see a glint of light appear at bottom edge of your blade, pull it back 1/8" and try it again.  A second glint of light that becomes brighter as you slowly slide the blade away from the muzzle is confirmation that you have found the true, accurate intersect point.  Repeat and read the distance at the muzzle face.  On the seacoast Parrott, we found it to be at 5.55", which, on our 1/6 scale rifle, is .925".   That's it!  Very simple, but extremely effective.

Have fun!

Mike and Tracy

[Ex 49'er]

If you carry one of the multi-tools on your belt like a Leatherman or Gerber, they usually have a scale of some kind on the edge. My Leatherman
Supertool has an 8 inch scale on the back. 101 uses. Hope this helps.