Chamber Dimensions Chart?

[flagman1776]

Is there a chart...  I can't find one anywhere...  which shows for each bore or chamber diameter, how much length of chamber is required for a given charge?  It would be very useful in planning a build to know the dimension to plan the chamber for. 
Example:  If you were going to plan a GB howitzer but with a 1" chamber diameter...  The recommended change weight is ~200 grains for an unpatched ball load (per the stickies).     http://www.gboreloaded.com/forums/index.php/topic,89682.0.html  But how many inches of chamber would that be?  And how many inches of chamber would a blank load get? 
 

[Zulu]

Flagman,
Double D has talked about thuis numerous times before.  Drill a 1" hole in a piece of wood.  Fill it with 200 grains of powder.  Mark a line at the top of the powder and then measure the depth of the hole.
That would be your powder chamber.
I think it is the simplest way to figure it out.
Zulu

[armorer77]

I can tell you that a 1" x 2" chamber will hold 300 grs. Ed

[Old Nukee]

You can come pretty close to getting your desired chamber size by knowing the density of black powder and the final volume of the chamber.


The density of black powder changes with grade and humidity, but if you use 250 grains per cubic inch you'll be on the safe side.


To calculate the chamber volume, square the radius, multiply by pi (3.14), and then multiply the chamber length (all in inches) to get the volume of a pure cylinder. Multiply that by the density, and you have your powder charge.


For example, a 1" x 2" long chamber would be  (0.5" x 0.5") x 3.14 x 2" = 1.57 cubic inches.
1.57 c.i. x 250 gr./c.i. gives you 392.5 grains capacity.


This formula is for a perfectly cylindrical chamber. If you have a hemispherical bottom on your chamber, that reduces the effective length of your chamber by about 1/2 of a radius.


This should get you in the ballpark, but remember to weigh a full charge just to be sure (and leave a full caliber wall thickness).


Tom

[flagman1776]

Thanks

[seacoastartillery]

    Old Nukee,   hardly anybody here remembers anything about using basic math to figure this stuff out for themselves.  For those who have a real interest, here is more stuff similar to what  you posted from a slightly different viewpoint.  Posted by Seacoast on  July 1, 2012, reply no. 17.

                                          http://www.gboreloaded.com/forums/index.php/topic,259781.0.htm



     Zulu has a quick and practical way to do it.  If we are in a hurry, this way is good, but most of the time we want to know the WHY? of what we do, so we do the math then cut the brass or copper measure to throw a precise charge. 


Tracy and Mike are visiting an artilleryman on Long Island.   

 
P.S.    We will be in Northern Maine on Sunday visiting Spuddy.     

[Double D]

So this begs the age old question, which came first, the hole or mathematical equation...

Which is easier to remember the drill a hole and measure method or  which mathematical formula to use.

To decide which method to use determine if you are millwright or an engineer.

John Browning could build a safe functioning gun design using jigs and fixtures from which more guns could be built, in three days after which Winchester engineers took 8 months to study and draw the plans to build and tool up to build Browning's guns.  In the end both methods worked.

All depends on what you want in the end and how you want to get it.

[GGaskill]

If we could agree upon the bulk densities of Black Powder (say only Goex for this example), I could write a Javascript web page similar to the round ball calculator that would accept any combination of powder charge weight, chamber diameter and chamber length and compute the other piece.  Or I could make it more generic but you would have to input the powder density yourself.

[Double D]

If we could agree upon the bulk densities of Black Powder (say only Goex for this example), I could write a Javascript web page similar to the round ball calculator that would accept any combination of powder charge weight, chamber diameter and chamber length and compute the other piece.  Or I could make it more generic but you would have to input the powder density yourself.

Great Idea George. Just use an average density.  The Powder densities are not going to all be the same, but the variation should be in decimals of diameters in the final equation. 

[GGaskill]

Take a look at this Lee Precision chart for bulk densities.  The numbers are basically grains to cm³ conversion factors (see the bottom of the page for that note.)  I would have to convert to in³ but that is simple.  For cm³, V (volume) equals w (weight in grains) times f (the Lee VMD factor from the table).  For in³, V_in³ = V_cm³ / 16.387.  Or combined, V_in³ = w * f / 16.387.