Id help please

[CarlS]

Joe,

Are there set diameters for the fuses?  In other words, are all 8-inch mortar fuses a given diameter at the top and bottom?

[joevann]

Joe,

Are there set diameters for the fuses?  In other words, are all 8-inch mortar fuses a given diameter at the top and bottom?

I believe so as far as the United States is concerned.  The attached are from the Ordnance Manuals for 1841 and 1862.  As you can see, there is no distinction for 8-inch fuzes for mortars or guns and the dimensions didn't change in that 21 year span.

[John D. Bartleson Jr.]

Joe,
  Did the manual give the max burn times and procedures to prepare the fuse for use?
After tearing off the paper cover, didn't the person preparing the fuse have to cut off the bottom groove in order to expose the the driven mealed powder at the fuse end?
John
P.s. I am surprised that the fuse body was not marked numerically with seconds.

[joevann]

That is true, John, but that information would not be contained in the Ordnance Manual, which is concerned more with manufacture and supply.  To understand how to use the fuze you must consult the Artillerist's Manual.  The paper cover gives the burning time per inch of composition and the fuze body is marked inches and tenths of an inch beginning at the bottom of the cup containing the priming composition.  It was up to the officer commanding the gun to calculate the length that the fuze should be cut.  This is the oldest type of fuze and was being fazed out in favor of paper fuzes.

[joevann]

Of course, for seacoast mortars a watercap is used, either of brass or wood body.  They are only 2.5 inches long with the same taper as the fuze hole, but slightly larger in diameter.   They take a paper fuze.

[John D. Bartleson Jr.]

But whether a time was selected or not the bottom groove had to be cut off, correct? 
So the first groove at top would be 5 seconds?
The fuse column is drivenmealed powder, not musket powder correct?
I never dealt much with mortar fuses.
Regards,
John
P.s. For my drawing do you know what color the paper cap was?

[joevann]

The grooves are every 1/10 inch.  Time wise, that depends on the burning time per inch of the composition.   If it is marked "5"  thats the time  in seconds per inch, so the first mark would indicate  0.5 seconds.  The paper is manila and the label is white.  It's easier just to show an example.  Yes, they had to be sawed.

[6lbgun]

It could either be sawed or a fuse gimlet could be used to set the burning time.
Dan

[John D. Bartleson Jr.]

Dan,
  I know it says that in the Manual, however if the gunner wanted 5 seconds then a hole would be inside the shell wall, perhaps?
Joe,
  You missed a couple of my questions.    .5 or 5 secons to the inch?
John

[6lbgun]

John,
     I'm using the range tables shortest distance and the thickness of the shells at the fuse hole.
8" siege mortar -  500yds - 10 sec - hole depth 1.25 in
10" siege mortar - 300yds - 6.5 sec - hole depth 1.6 in
13" mortar - 4,325yds - 40 sec - hole depth 2.1 in
     In the 10" mortar, a 5 sec per inch fuse could not be bored with a fuse gimlet if 300yds was called for.  It would have to be cut with a saw or a faster burning rate fuse would have to be used. 
Dan 

[joevann]

Dan is correct.  You must make  the time train open to the interior charge.  John, apparently I don't understand your question.  The fuze is labeled with the burning time per inch.  The circumference of the fuze is scored in 0.1-inch increments with a heavier score line at one-inch intervals.  If the label says 5 seconds to the inch, that means exactly that.  Each increment, though would be 0.5 second burning time because there are ten scored lines per inch.

[joevann]

Once again, Dan is correct.  The example I've shown is NOT for an 8-inch mortar. 

[John D. Bartleson Jr.]

Joe,  question 1 and 3 below did not get answered:

"1 But whether a time was selected or not the bottom groove had to be cut off, correct? 
So the first groove at top would be 5 seconds?
3. The fuse column is drivenmealed powder, not musket powder correct?
I never dealt much with mortar fuses.
Regards,
John"

[John D. Bartleson Jr.]

Thanks Dan, very thorough as usual. I didn't realize some had minimum ranges.
Interesting subject.
I noticed in the 1963 Gibbons that there is a fuse auger , an abreviated version  of the British borer that I posted.
Regards,
John

[joevann]

1.  If you wanted to go the full burn time, the fuze would still have to be cut at the bottom increment.  If no entry is made to the fuze composition, it doesn't work.

3. The fuze composition for 8-inch and 10-inch light mortars is made of 2 parts potassium nitrate, 1 part sulfur, and 3 parts mealed powder (black powder) throroughly ground and mixed.  This was done for every batch.  It was driven into the wood bodies, and a few were tested.  Adjustments were made in the proportions to get the desired burning time as it could very greatly depending on the quality of the mealed powder.  When it is driven in, it becomes hard as a rock just as in a paper fuze.  It is not a loose mixture after being driven.