Converting boolit drawings to 3d models

[Mr_Sheesh]

Hi all.

I have never seen some of the terms used on boolit drawings defined, one of my long term projects is to make models of any case and/or boolit out there, this would allow making snap caps, dummy bullets, lots of good things.

But for example if you look at https://noebulletmolds.com/site/314-152-rn-314466/, what the term "Tangent Ogive Radius 1.57 Nose Diameters" means in term of how you draw that curve, just isn't clicking for me.

I'm pretty good with math, what I need is to be able to get a formula off that that will tell me what the curve is for the boolit's nose, so I can talk my CAD package into approximating it. (Done Tensor Calc, Z plane transforms, tons of calculus of other sorts, this is "just" trig so it should be simple if I had that origin nailed down...

I could approximate it with a bunch of truncated cone sections, but something cleaner looking would be nicer!

Really scratching my head trying to figure out where this radius is measured FROM, in relation to the bullet surface.

Give me Z-Plane math or tensor calc problems and I can chug through them, but a lack of definitions sorta hamstrings me here.

[GregLaROCHE]

I’m surprised that in today’s age of computers, there’s not a program where you can paste the curve and a formula for it will be given.

[Mr_Sheesh]

If I had my tools all working I could do a least-squares curve fit to it, but sadly that's not the case. (Linear Algebra tool, that.)

[JimB..]

This might get you started, or it might not.
https://mathscinotes.wordpress.com/2011/01/11/ballistics-ogives-and-bullet-shapes-part-1/

[Mr_Sheesh]

Hmmm maybe go back to old school and use dividers to find the radius then start seeing if I can figure it out from there. Hmmm.

[JimB..]

I don’t understand that term, but doesn’t it look like the nose profile is a circle with diameter .163” and the ogive is tangent to the cylinder and the nose profile?
Seems that you can draw a right angle, the bottom is .248” in length, the height is half of .285”. On the left it is tangent to the cylinder, on the right it is tangent to the nose profile circle.
Then you do some magic and the formula for the curve drops out.

[Tom Myers]

Hi all.

I have never seen some of the terms used on boolit drawings defined, one of my long term projects is to make models of any case and/or boolit out there, this would allow making snap caps, dummy bullets, lots of good things.

But for example if you look at https://noebulletmolds.com/site/314-152-rn-314466/, what the term "Tangent Ogive Radius 1.57 Nose Diameters" means in term of how you draw that curve, just isn't clicking for me.

I'm pretty good with math, what I need is to be able to get a formula off that that will tell me what the curve is for the boolit's nose, so I can talk my CAD package into approximating it. (Done Tensor Calc, Z plane transforms, tons of calculus of other sorts, this is "just" trig so it should be simple if I had that origin nailed down...

I could approximate it with a bunch of truncated cone sections, but something cleaner looking would be nicer!

Really scratching my head trying to figure out where this radius is measured FROM, in relation to the bullet surface.

Give me Z-Plane math or tensor calc problems and I can chug through them, but a lack of definitions sorta hamstrings me here.


The Precision Bullet Design Sofware (https://www.tmtpages.com/#Advanced) help file has a diagram that might shed a little light on your problem.

Tangent Ogive Nose Detail (https://www.tmtpages.com/draw/HelpfilesAdv-5/hlp_nose_detail.htm)

The Precision Shooting Software (https://www.tmtpages.com/) website has a page that contains formulas for calculating the radius of the ogive of a bullet from measurement values of the bullet nose.

Tangent Ogive Calculations (https://www.tmtpages.com/tech/tangent_ogive.htm)

The word "Tangent" is defined as "A straight line or plane that touches a curve or curved surface at a point, but if extended does not cross it at that point".

This is the Tangent point on the curve of the ogive where the curve is going in the same direction as the bullet nose.
On a Tangent Ogive, the tangent base is the same diameter as the bullet nose diameter.
The radius of the curve of a Tangent Ogive is defined in terms of Nose Diameters
The base of a Tangent Ogive is positioned on the same vertical plane as the point where the Tangent Ogive and the bullet nose join.

A Secant Ogive is simply a tangent ogive that is shortened from the back side.
The point on the curve of the secant ogive where it meets the bullet nose diameter is at a slight angle to the side of the bullet nose.
On a Secant Ogive the tangent base is larger than the bullet nose diameter.
The radius of the curve of a Secant Ogive is also defined in terms of Nose Diameters.
The base of a Secant Ogive is positioned rearward of the vertical plane where the secant ogive and the bullet nose join.

My experience in bullet design is principally 2 dimensional but lately I have been playing aroung with the 3D printer and tried printing some of my Precision Cast Bullet
Designs and scaled cartridge casings.

I use OpenSCAD to write the code for the designs

Using the x axis for bullet length and entering the various diameter dimensions in both the "Y" and "Z" axis values, I was able to print out some very nice models.

If you need any more help with specific dimension values, maybe I can help a little.

Hope this helps.

[Mr_Sheesh]

Dividers as in https://www.artisanleather.co.uk/top-quality-wing-dividers-6-inch-2552-p.html only with a pencil at one tip

[HollowPoint]

I know what you mean about not being able to figure out that tangent-ogive radius stuff. I'm mathematically challenged. No joke; I absolutely suck at math so I go about figuring out these things in a sort of cheating way whenever possible.

Just recently I copied a 9mm bullet profile from the NOE bullet mold site just as a sample for a 3D print model. I didn't know how do the mathematical calculations of this particular bullet shape so I drew those parts that I did know how to model and then I just overlaid the image of the actual bullet profile onto my model. In the SolidWorks CAD software I'm able to do this.

Anyway; with the drawing of the 9mm bullet set on top of my model I was able to sketch the exact ogive or curvature of the nose of the bullet. I could have just eye-balled it and come close enough to be a near match but I wanted to make sure I got it as close to precise as possible.

Even better still would have been for me to have figured it all out without this cheating method but, when you're ignorant about such things as I seem to be, you just have to find work-arounds to get the job done.

HollowPoint

[GWS]

Looking at your example, start by multiplying .303x1.57 arriving at .47571 radius for the tangent curve between the nose and the straight approaching it.

Then I'd do a "LINE" command, draw a straight line, hit enter, type "ARC" hit enter (in my Autocad) hit enter again, and a tangent arc starts....give it the .47571 radius (not diameter) and draw the arc arbitrarily. Then I'd mirror the line/arc at 1/2 the boolit diameter. Then draw lines 1/2 the nose diameter off the resulting centerline and move it to the intersections of the arcs. Trim the extra lines/curves.

You may not be using Autocad, but maybe those instructions are good enough to give you enough clues to convert to how your software works.

Updated: the nose diameter is .303 not that .163.....the .163 is the end of the arc. then the bullet tip is a curve with 3 points given .... where the two arcs intersect the .163 and the intersection of the centerline and overall length.

I went ahead and drew it successfully in autocad to test it.

https://i.postimg.cc/Vk4F1DFz/Screenshot-2021-06-22-150850.png

You gave me something fun to do this afternoon....thanks! Went ahead and did the drawing and made an .stl file you might could test. Let me know how it printed. ;)

[popper]

Tangent curve from an EXTERNAL point of radii R.

[GWS]

I decided to go ahead and print one! (out of Kryptonite ;))

Quick and dirty solid print at .2 high.....and I didn't even check for flat first layer....took 17 minutes.
So what did I learn? Layer height .17 would be better.....and a higher filament temp.

I forgot to convert the Autocad file to mm.....source was inches so I drew it in inches.....would have taken 2 minutes extra time to convert.

However my IdeaMaker slicer saved me and asked if I wanted the .stl converted to mm. Was glad it had that feature. So hopefully your slicer can do that too, otherwise holler and I'll convert it in Autocad and save and upload a new .stl

Here's my Kryptonite....

https://i.postimg.cc/J0DTzgQf/IMG-3902.jpg
One problem with printing something this small is that even the skirt can't be seen to baby step proper nozzle height. Must set the skirt a couple of inches away from the model to be able to dial it in properly....
https://i.postimg.cc/2ys0bwcV/IMG-3903.jpg
And for this application I think the .2 mm layer height is a little high besides it not being squished enough. Normally would have baby stepped it in closer. Actually this PLA is not my usual Green.....the company had a source problem and substituted....I was not happy....instead of printing nice and smooth at 215C and 60C bed, this stuff has to be printed at 230C/70C.....and I don't really think that's enough. Still isn't melted enough. Will have to experiment some more with it....will never buy that brand again....too much trouble.
https://i.postimg.cc/h4XgmtZB/IMG-3904.jpg
But the .stl is right on.....just ugly using this PLA.

[GregLaROCHE]

P
I decided to go ahead and print one! (out of Kryptonite ;))

Quick and dirty solid print at .2 high.....and I didn't even check for flat first layer....took 17 minutes.
So what did I learn? Layer height .17 would be better.....and a higher filament temp.

I forgot to convert the Autocad file to mm.....source was inches so I drew it in inches.....would have taken 2 minutes extra time to convert.

However my IdeaMaker slicer saved me and asked if I wanted the .stl converted to mm. Was glad it had that feature. So hopefully your slicer can do that too, otherwise holler and I'll convert it in Autocad and save and upload a new .stl

Here's my Kryptonite....

https://i.postimg.cc/J0DTzgQf/IMG-3902.jpg
One problem with printing something this small is that even the skirt can't be seen to baby step proper nozzle height. Must set the skirt a couple of inches away from the model to be able to dial it in properly....
https://i.postimg.cc/2ys0bwcV/IMG-3903.jpg
And for this application I think the .2 mm layer height is a little high besides it not being squished enough. Normally would have baby stepped it in closer. Actually this PLA is not my usual Green.....the company had a source problem and substituted....I was not happy....instead of printing nice and smooth at 215C and 60C bed, this stuff has to be printed at 230C/70C.....and I don't really think that's enough. Still isn't melted enough. Will have to experiment some more with it....will never buy that brand again....too much trouble.
https://i.postimg.cc/h4XgmtZB/IMG-3904.jpg
But the .stl is right on.....just ugly using this PLA.

Nice! Do you think if you PCed it, you could shoot it without gunking up the bore?

[GWS]

I don't have a clue, but I did print a black kleenex box with a lift off lid for my 4Runner.......and it melted in the summer heat on my Dash. ;) Of course it was with normal PLA, not this higher temp weird stuff I used here. Also I'm guessing the light plastic won't have much range....not going to replace lead any time soon.

[HollowPoint]

This reminds me of the time I cast some .22 caliber bullets out of Hot-Melt-Glue. I wanted to see if I could shoot them out of my break barrel air guns.

I know that the bore of a .22 caliber air gun is smaller than that of a center fire gun but being that the Hot-Melt glue had some elasticity to it I was sure it would work. I was right. It did shoot out of my break barrel air rifle. That Hot-Glue bullet came out of the bore at over 1500 fps. It sounded like I was shooting a 22 rimfire in my back yard.

Yes, neighbors called the cops on me. Lesson learned the hard way. Fortunately those police officers had a sense of humor.

Those Hot-Melt-Glue bullets had no accuracy to speak of; in fact, none of the three I shot seemed to make it to the target I'd set up about fifteen yards away. I don't know if they disintegrated in flight or they just veered off horrendously before reaching that target.

I mention my failed experiment because although your 3D printed bullet may not replace lead any time soon perhaps it may be useful for short range pest control out of an appropriately chambered air rifle. Although such an air rifle may not have a tight enough rifling twist to stabilize a lead projectile of this size, an ultra light weight projectile of this size may still stabilize due to the extreme speed they'd be spinning upon leaving the bore.

Just lightly lube them with some of that silicone high-heat resistant lubricant used for high pressure air guns and they might actually work out of an air gun.

https://www.instagram.com/p/BsUFQMThp-_/

HollowPoint

[kayala]

P

Nice! Do you think if you PCed it, you could shoot it without gunking up the bore?

I don't think standard PLA will survive PC curing temperature.

[GWS]

Besides, I'm not sure PC has any merit for plastic bullets, unless it "PLA's" the barrel.......guess somebody will have to try it if they want to know. Not me. I'm behind....still shooting copper plated and jacketed. ;) Unfortunately, since Covid started I do more making of 3d printed reloading equipment and reloading ammo with it than shooting it. Not to mention, I've spent more days in the hospital than out shooting.:(

But I'll be good to go soon.... funny.....I make a .stl of a boolit just to be doing something shooting related, for Mr. Sheesh, and happy to have something to break the monotony.

[Mr_Sheesh]

Tom Myers - What I need is to get the X,Y coordinates of the radius' point of origin from the curve, I think I am figuring it out.

Today's been a really weird day, neighbor having problems breathing so I got her down to the hospital, waiting to hear test results. GF of a guy who I've known since ~1970, he's over at her place feeding her cat right now. Could be worse!

Hollowpoint - Must be nice to be able to sketch, I can use french curves etc. but any attempt to sketch with a mouse results in a mess!

GWS - OpenSCAD doesn't have a "Line" command as such, it's a programmers' 3D CAD package, not an artist's CAD package. I can stack truncated cones atop one another though, the thinner slices of cones I use, the better the result will look. So I need data points to do the math for those trunc. cones' radii or diameters and heights. In OpenSCAD the commands will look like,

translate([X1,Y1,Z1]) cylinder(r1=R1, r2=R2, h=H2-H1);
translate([X2,Y2,Z2]) cylinder(r1=R2, r2=R3, h=H3-H2);
translate([X3,Y3,Z3]) cylinder(r1=R3, r2=R4, h=H4-H3);

No sketching tools in OpenSCAD at all, though you can import things like that from other programs...

popper - Yes, and no guarantee that the location's at any specific point along the boolit's length as you could have a secant or tangent profile...

My guess is that any not thoroughly fused FDM'ed bullet would shred into a puff of itty bitty bits of filament shortly after leaving the muzzle, due to the high rotational speeds involved. Filament isn't THAT strong in tension.

[kayala]

I’m using Fusion360, which is free for hobby. Tried OpenSCAD and just can’t wrap my head around it; maybe I don’t have enough imagination to picture an object in my head and represent it as a series of additions/subtractions of geometric bodies :)

[HollowPoint]

"Hollowpoint - Must be nice to be able to sketch, I can use french curves etc. but any attempt to sketch with a mouse results in a mess!"

I may have just worded my comment incorrectly. What I meant by, "Sketch" is that in the SolidWorks software the sketch feature has tools that include a circle tool, a curve tool, all manner of tools that are considered "Sketch" tools.

I simply used the curve tool. I'm afraid my comment may have made it sound like I was free-hand sketching. I'm not steady enough to pull that off. With the curve tool I just aligned the curves to match the curvature of the bullet nose.


HollowPoint

[Mr_Sheesh]

HollowPoint - It's just that in OpenSCAD there is no "draw a line" command, you issue text commands that are programming-like commands to get it to create 2D and 3D shapes.

Different CAD packages are different :) OpenSCAD's commands are listed at https://openscad.org/cheatsheet/ if you want to take a look.

Friend used to make a very costly AutoCAD plugin for the Architecture / building / Landscaping crowd, so I am familiar with that package. It would do cost estimates for wire, plumbing, etc. for Architecture.

[Tom Myers]

Hi all.

******8

I'm pretty good with math, what I need is to be able to get a formula off that that will tell me what the curve is for the boolit's nose, so I can talk my CAD package into approximating it. (Done Tensor Calc, Z plane transforms, tons of calculus of other sorts, this is "just" trig so it should be simple if I had that origin nailed down...

******.

Mr_Sheesh,

Maybe this is what you need.

This formula will calculate the y axis at any point along the centerline (x axis) of a bullet ogive.

Let R = The radius of the ogive curve.

Let B= The y axis at the base of the ogive.

Let X= A distance from the base of the ogive.

Let Y = the y axis at the point X on the centerline of the bullet ogive.

Then:

Y = SqRt( R² - X²) + B - R

Hope this helps.

You can re-arrange the values to find the x axis distance when the y axis is known.

X = SqRt( R² - ( Y + R - B )² )

[GWS]

The only "cad" software I'm aware of that's for "artists" is blender. Great for free form where you don't have to be accurate closer than it looks right. Autocad is for architects and engineers, and I suppose we are artists in the same way programmers are artists. I'd argue that the genious plate generator Ammo Mike developed is a case in point. That's a piece of art!

I don't have the patience for programming or OpenScad.(it's an old dog/new tricks sort of thing) I suppose if I wanted to create a similar program for boolits as Mike did for plates....I might want to learn more than the rudimentary skills I learned and mostly forgot in OpenScad.

I drew that boolit in about 20 minutes....and that snails pace is only because I only started learning the 3D side of Autocad last September when I bought my Creality CR10v2. In Building design, 3d is mostly for rich customers who can't envision a building in 2D. I say rich because 3D drawings of buildings done realistically with texture, lighting, and shadows take a much longer time. Most customers are not willing to spend the money. The trades who actually build the buildings use 2D drawings, except for the rare detail you can't see in 2D.

What's neat about designing your boolit in Autocad, is that I only had to draw the section through the center line in 2D. Make it a polyline (all lines and arcs become one closed entity). Then rotate it 360 degrees about it's axis, and voila! A perfect engineered, correct 3D solid.....but it can't be another size or shape without redoing the 2D polyline. To me that's the only point of doing it in Openscad.

I printed your boolit only to see if the drawings from Noe were correct and whether I had the right idea about the arc on the ogee. They were pretty darn close.

[GregLaROCHE]

3D printed projectiles might be interesting for someone wanting to load mouse fart loads, to shoot in their garage or basement.

[Mr_Sheesh]

Thank you, folks, I think maybe that will do me, have to get a real computer going to test it though. (The current netbook is an old doddering piece of slow hardware, Core 2, not even a Duo. Lag central...) I can't even run OpenSCAD on this thing, pretty sad. Getting set to order a new machine, in a day or two.

[GWS]

I just went through that this month. I had an HP Envy 4 years old that gave up the ghost. I liked it enough that I ordered another in their custom build section of their website. Did that last time too. Was willing to wait the month. But it didn't come....instead they sent a notice that it would be 2 more weeks, and another week went by and they still hadn't started on it.....so I canceled. Went looking for another solution minus the custom build and long build window, and found an MSI that even has an Nvidea Quadro 1000 video card, which means for the first time I can even run Autocad on a 15" laptop. It came in 4 days. Works great....it's a Core i7 ninth generation with 16gigabytes of ram. Very happy so far. And a lot cheaper than typical $2000 laptop cad workstations.

Down side compared to the HP? just no SD card slots. But the SD card slot was one of the things that quit on my HP. And I found you can find plug-in SD card readers for cheap.....and if they go out just get another instead of a whole computer. the one I found reads more kinds of SD's as well.

[Mr_Sheesh]

I have been using IOGear USB to SD and Micro SD dongles for years, they have worked well for me. Until a family member stole too much from me, years ago, I was set up to be able to move data from almost any media / format to almost any media/format, have parallel port hard drives and cd-roms and PCMCIA docks and floppy drives, all the stuff needed for old machines and usb goodies o'course for new.

That MSI sounds about like what I need, Core i5 2nd gen with 8GB RAM has been the 'fast' machine here, Coffee Lake with a good video card would make things far nicer! And for one game I play, where the video drivers on the old machine were 1500+ days old, I might be able to play the game with over 10 FPS or so, "might" be a smidge less laggy!