Chronographing Artillery Pieces....

Just how does one chronograph an artillery piece? Besides very carefully? I mean one has to deal with a large cloud of dense smoke and then there's debris from the powder bag. And what If a sabot is used? And let's not forget the shockwave. I've seen novices rise from the ground like they've been mule kicked in the chest when firing an inch and three quarter gonne. :shake: That's seems an awful lot for a chronograph to deal with.

 

[robinghewitt]

 

[Bob Riegl]

Chronographing artillery is a rather involved technique. I witnessed a test done at Fort Sill( many years back ), on a piece of Russian artillery. They fired the round through a series of 2 wire loops (strung between 90' telephone poles )---about 200 yards apart---sensors detected the round and (crude computers) by computers they were able to determine the muzzle velocity and the velocity decrease at 200 yards. I don't see any amateur using a modern day Chrony being able to successfully test the miniature artillery. I have used a Chrony on BP firearms but I feel the patch material and powder trail kinda screws up the end result. :m2c:

 

[Will Bison]

I have been working on such a project since early Spring. Given the fact that I limited my testing to those items I had on hand and not purchasing expensive equipment.

Even with the use of two blast shields in front of the gun, the shock wave still knocked my dummy chrono and tripod down. (I was smart and didn't put my real clock out front)

The military now uses radar units stationed along the path of the projectile. I expect that the equipment is very costly and is probably beyond the means of the average cannon shooter.

I have used a rather unscientific approach by utilizing a stop watch and GPS. The stop watch gives the time of flight and the GPS measures the distance to the target. The distance to the target need not be an even 200, 400, 600 yards etc. I simply pick an obvious target and fire at it then find the time and distance.

My method has some obvious faults. At ranges of less than 200-300 yards you must be very exact on starting and stopping the clock. The other downside is having the ability to shoot to longer distances. I have the advantage of being able to fire for several miles if I so decide. Many cannon shooters are limited to much shorter ranges.

As I continue to compile data, a graph will begin to emerge showing time of flight and average velocity. The other limitation is being able to see the fall of shot at longer ranges. Out to about 1200 yards the ball kicks up enough dust to see it, after that it starts to get tricky.

 

Here's a thought! You struck a cord with the mention of radar. I wonder what's the fastest speed a sports type radar gun has? Baseballs are about the same size as some of the projectiles fired from hobby size artillery.

Just :m2c:

 

[rmonday2]

I have been pondering your problem about chronographing a cannon, and if I had this task.... I would pick up a couple of cheep stop watches (walmart), mount them on two separate boards app. 6x6 inches(watch in the middle) and a couple of holes in the board so you can stake it to the ground. Then mount a small brass type hinge that you could change out...say a popcycle stick that could acivate the start button on the watch. (The stick should break fairly easy and leave the watch unscaved). Then you could attach a string to the stick and around the muzzle of the cannon, ( are you starting to see where Im going?)
Attach the other to a ...... say, plywood target at a measured distance, and shoot.
Once the two are activated, remove the watches, press the two stop buttons against one-another to asure precision, and calculate the difference in time!
It'll work! It's got to.But you may have to play with the string-thing on the muzzle end.

((((xxxx WARNING xxxx)))
Never tried it, just thunk it. Good luck with what ever you try :thumbsup:Ronnie...
P.S. Sounded good though didn't it :crackup:

 

[robinghewitt]

That is a genuine picture of someone chronographing a cannon, you can see the electric wires running down to the two "wire breaker" screens.

The only real problem with wire breakers is that wire stretches some indeterminate distance before it breaks, so you'd want them tight and brittle.

I believe radar is used to measure paintball, but that's kinda slow in comparison.

Rather too big to use the spinning discs method.

I'd go for a wire breaker and use two wires mounted vertically to allow for a bit of muzzle flip. I could probably patch togther the electronics if you tell me the separation :thumbsup:

 

[WRussell]

Seems like a pretty simple electronic problem, just a gate to start a clock and another to stop it. Wire or light beam across the muzzle to trigger the start gate.

From here it gets harder. If you can rely on hitting a target, make the target out of say a row of old fence boards with a fine wire woven between them so a hit anywhere would shear the wire.

You'd have to run a bigger wire downrange, but that would be something that could be reused.

We certainly have some expert chrono talent in Squire Robin, and he has offered to help! This project sounds like it will go somewhere.

:m2c:

 

Are we talking about wire like magnet wire? ::

If so, what if one was to tauntly run a length of wire back and forth between two uprights, two sets, to insure the projectile breaks continuity. If done right wires could be easily replaced for reuse. :hmm:

Squire, what sort of distance would you recommend? You're the chronograph designer/expert. :master: :master:

 

Sorry Bill, didn't read your post until after I replied to the Squire's.

Great minds think alike!

:sorry:

 

[robinghewitt]

Squire, what sort of distance would you recommend?

I think 600mm could be a good idea :thumbsup:

I just converted one with duff optics into a wire breaker. It's designed for 60mm so you just have to multiply the distance and result by the same number.

Now I have to figure out how to test it. Wonder if it'll work :hmm:

 

[WRussell]

You the man!

:master:

You may have a new, highly profitable product here!





Maybe I'll buy one for my cannon - if I can find a place to shoot it.

:cry:

 

[robinghewitt]

You may have a new, highly profitable product here!

I don't think I'll quit my day job quite yet ::

It works but the wires are stretching. I wrapped them around either end of a tube 3" long by 5/8" diameter, then broke them with a pellet gun at around 500 fps.

I think the first wire is easier to break than the second because it was reading slow.

First shot was 10 fps slow, an extra 0.06" at the exit due to stretch. I tried soldering the wires rather than just twisting and that halved the error.

What it needs is something that conducts like copper but breaks like glass.

Increasing the separation is good, increasing the wire length is not good. Having the same mounting at either end should help.

I also think maybe the wire needs to be held under tension rather than stuck on with tape

All I need now is for CP to mail me an address to send it to :thumbsup:

 

Squire, what sort of distance would you recommend?

I think 600mm could be a good idea :thumbsup:

600mm? just under 2 feet or 600 cm? roughly 19 1/2 feet. :hmm: But whatever the distance, it has to be done in multiples of 60mm. Correct?

I just converted one with duff optics into a wire breaker. It's designed for 60mm so you just have to multiply the distance and result by the same number.

Fantastic! I think I'll try it out with Zeus, my four bore handgonne.

I'll build a couple of wooden frames, using brass wood screws and copper washers to secure the sections of wire. Running some 34 gauge, awg, magnet wire, that should snap quite nicely. Having it go vertically and horizonally, criss crossing every 6.5mm, roughly a 1/4 inch, and go with a 3'4"x3'4", 1 meter x 1 meter square.

:hmm: Would the ohmage effect the readings?::

My electronic knowledge comes from my college courses in electronic communications and peaking citizens band radios. Two instructors were former R&D techs for government contractors. ff:

Just :m2c:

 

[WRussell]

What it needs is something that conducts like copper but breaks like glass.

If it wasn't for the mess to clean up, you could use the conductive tape made for burglar alarms on windows. Stick it on the far side of the glass for a cleaner break.

I used to work with tungsten wire - it's nice and brittle, but not your average hardware store item.

You could use a very short piece of fine wire attached to the top edge of a piece of plywood that would hinge at the bottom when smacked. I'm thinking cannon balls here - not much worry about slowing the thing down.

Or... (gosh this is fun) the fence board idea again, with the wire fastened at the edge of each board so there is only a short length to stretch and break.

How about a conductive paint stripe on a piece of paper?

Or... use a saturated sugar solution (movie glass). Brittle, but no hazardous mess. (At least not after it rains) Put the conductive tape on the sugar glass.
http://www.recipesource.com/desserts/candy/01/rec0170.html

Or imbed the wire in it before it cools.

 

[musketman]

What it needs is something that conducts like copper but breaks like glass.

Aluminum foil?

How about dry-iced copper?

Could you take the Faraday Cage off the door of an old microwave and use it?

How about copper foil tape?
Stain glass workers use this to edge the glass before soldering...

 

The wire needs to be insulated from the others so that there in a single flow of electrons going in and coming out. A Faraday cage is mesh wire and would not work for our purpose.

As for copper tape, it had too much give and may be prone to breakage from the concussion to give an accurate reading.

The screen has to offer little resistance to any gases or air flow that may precede the actual projectile.

Hope that all makes sense.

 

[WRussell]

The screen has to offer little resistance to any gases or air flow that may precede the actual projectile.

What if the chrono is downrange 50 yds or so?

If the two sensors are close together you have to worry about the debris from the first one triggering the second one, I guess.

What would happen if you wove a grid of copper wire, then painted all the wires with the movie glass mix?

 

[robinghewitt]

I tried it out this morning with a wire separation of 300mm, point blank with a proofing load in my Lantaka. The video camera bravely volunteered to stay and record the event while everyone else ran for it.

Movie 202k

The result was 271.2 x 5 = 1356 fps but no way of checking it :thumbsup:

Here's a nice frame, the gun is firing right to left and it's caught the moment it broke the wires before the smoke blots everything out ::

 

[musketman]

Robin, I'm surprised it didn't go booooom, sounded more like a rocket going off...

Now why didn't you hold it?

Claypipe held his gonne for his quicktime movie... :haha:

Sure had some muzzle jump though, thanks for taking time to record it...