Usefulness of Euclidean geometry

[Bioprof]

How often do you use concepts of geometry that you learned in high school in gun building?   Any examples of its use in barrel making or stock making?  Just curious.

[northmn]

 While its been a while since HS, (my kids would ask me if I knew Euclid personally)  I cannot say that there is anything standing out as Geometry use in my stock lay outs.  I do build from blanks.  Most is layout of lines, following certain proportions such as the wrist thickness and web thickness.  While a Lancaster layout is somewhat triangular the buttplate decides my convergence.  I do not calculate any angles.  Its kind of like the discussions of the golden mean.  You build what looks right.

DP

[smart dog]

Hi Bioprof,
Two examples:
1. Estimating the length of the angled sides of the lidded compartments for a pistol case. Essentially calculating the length of a hypotenuse from the sides joined by the right angle.  That gave me approximate length that I could cut and then fit more closely by trial and error.

2. Checking the angle of the frizzen above the pan at which it kicks over and opens under spring power. It is really hard to accurately measure that angle directly but if you know the vertical height of the frizzen above the rim of the pan at the point where it kicks over and the length from the bottom corner of the frizzen to the center of the pivot screw (things that are pretty easy to measure), the angle is simply the sine of the ratio of the vertical height divided by the length from bottom corner to the pivot screw.  Works for me.

dave 

[Mike Brooks]

I got D's in geometry.....

[Robby]

Reminds me of the time a fellow asked me how I make a long bow. I said, the long answer involves knowledge of physics, trigonometry, and enough ologies to fill Einstein's blackboard. the short answer, I take off all the wood that's not a bow.
Robby

[Nate McKenzie]

Does the Golden Mean count?

[Acer Saccharum]

Oh, no, the golden mean.  Not Again!

If I knew what it was, I am not sure I use any geometry. I must, I machine stuff all day long, but it might be more subconscious than anything.

Tom

[FG1]

Geomo who ?? Didnt have any in high school  I knew of .

[Bioprof]

I am in the process of building a wheellock pistol and the grip portion of the stock is octagonal in cross section.  I was trying to figure out how far down from the top and bottom of the stock to draw the guidelines to cut the diagonal flats.   I remembered from high school geometry that the hypotenuse of a right triangle with equal sides is the distance of one side multiplied by the square root of 2.    Therefore, the distance along the side of the triangle would be the distance of one of the flats divided by the square root of 2.  Alternatively, I suppose you could use the pythagorean theorum to come up with the same result.



You could also do like Robby suggested and just start removing wood until it looks right.

[T*O*F]

I suppose you could use the pythagorean theorum to come up with the same result.

Aren't you confusing geometry with trigonometry.  I only remember theorems in geometry, but nothing dealing with square roots until trig.

[smart dog]

Hi Bioprof,
This might help.  The width of a flat on an octagon is 2r * sin(22.5).  If your grip area is 2" wide then the radius is 1 inch. The formula then is 2*1*sin(22.5) = 2 *1 * 0.383 = 0.766 inches or just over 3/4 inches.  Draw center lines along the sides, top, and bottom of the grip and mark out the 3/4" flats for those sides centered on the lines. The oblique flats are then delineated by default.

dave

[Bioprof]

Hi Bioprof,
This might help.  The width of a flat on an octagon is 2r * sin(22.5).  If your grip area is 2" wide then the radius is 1 inch. The formula then is 2*1*sin(22.5) = 2 *1 * 0.383 = 0.766 inches or just over 3/4 inches.  Draw center lines along the sides, top, and bottom of the grip and mark out the 3/4" flats for those sides centered on the lines. The oblique flats are then delineated by default.

dave

The only problem is that the grip is not the same depth along it's length.   It flares out at the end.   What I plan on doing is to draw guidelines like you described based on the shallowest depth and then take off more wood towards the end to make it look right.   It would be much easier to just make it round in cross-section, wouldn't it???

[smart dog]

Hi Tim,
Could you simply calculate the width of flats for the narrow part and the wide part? Then draw your center lines, which are not affected by the flare. Mark the flat widths at the wide point and also the narrow point and then connect the marks with straight lines.  That would accomodate the change in diameter.  I say this because I did just that to grind a swamped barrel out of a straight octagon Green Mountain barrel. It worked like very well.

dave