Hmm why do paintball hits leave RING welts??

[ExtremeODD]

Everytime ive been shot (minus face mask hits) that leave welts they make a ring mark, is it when the paintball flys the fill goes to the back, so there is no paint in the tip and when it hits, the outeredge hits first then the center, but buy then its broke so that part doesnt marks. Thats my theory, is there any proof of this by comp evidence?? im confused

[VALCONE]

The answer is easy enough, lets see if I can explain it...
OK, from geometry we know a triangle is the strongest shape, and a circle, or sphere in this case, is the weakest. As the paintball hits you the front of the shell crumples, having no support. The edges around the 90* axis, however, have a lot of support from the shell around it. Thus these edges drive forward for a lot longer than the front part of the shell without crushing. And we are left with those ringworm looking marks and cuts we love so much.
V

[doc_Zox]

[RenagadeOfFunk]

:::claps hands sarcasticaly::::

...thats simple...im just glad we dont shoot triangle at each other...

[gamarada717]

That would certainly be interesting....but it would prolly be a pyramid, not a triangle. We're not in a video game, remember?

Also, the paint that is outside of the mark is also from the impact of the shell pushing it outward.

[AGD]

Valcone,

Excelent answer, welcome to Deep Blue.

AGD

[Redkey]

hmmm....

I don't think the triangle the strongest shape. I guess it would all depend on the context of where it was used. Think of a dam, a dome or even the aquaducts those silly romans built. All of those structures use an arch to distribute the loads to the outer edges of the shape

Also... if you look closely at your mask, under the correct lighting, you will see lots of rings from where the paintballs have hit.

A good way to visualize the mechanics behind this effect is to take a standard sheet of paper and roll it up into a tube about 1 inch in diameter. If you pinch the tube to collapse the diameter you'll notice very little resistance. Now, if you stand the tube on end and gently push on the top, hand covering the open end of the tube, you'll notice much more resistance to your pushing. This is *basically* the same effect that causes the ring welts... of course the impact loads peak only for an instant when the ball has collapsed enough to bring it's maximum diameter into contact with your skin.

[hitech]

Unless you are using Prefect Circle paintballs. They tend to fracture instead of collapse and do not leave the ring welt.

[VALCONE]

Redkey,
I guess I should explain. Arches and domes are great designs to work with if you have an equal amount of pressure distributed throughout the arch. They have a tendency to "fall into themselves", making them a very stable platform. This is also evident in deep-sea engineering, the constant high pressure of the ocean distributed evenly across a sphere or dome makes it very practical.
But this doesn’t change the fact that triangles are still stronger (Don’t believe those Volkswagen commercials!). In terms of simply bearing a load, or withstanding an impact, the equilateral triangle is the strongest shape. The load of a triangle is going to be distributed to only three points, rather than the infinity points of a circle. This is evident if you have any kind of CAD program that does load testing; a triangle can withstand as much as 15% more weight than an arch can (assuming that you are using the same width). For example, a bridge might be arched, but if you look at it's support structure, it will probably have crossbeams in the shape of a triangle.
By the way, your example with the paper cylinder was excellent. I was trying to think of a way to explain what I was thinking, but you nailed it perfectly.
V

[hitech]

What if the impact/load is in the center of one of the sides of the triangle?

[ExtremeODD]

wow a question about ring welts has turned into a debate about which shape is strongest, but in smart terms

[Redkey]

VALCONE,

Since we were talking spheres I figured the arch was perhaps a more suitable geometric shape. I didn't spend much time really thinking about this... i suppose I could have pulled out the statics book to add a little more meat to my statement. Instead I used the quick and cheesy way to defend my statement by saying.... "I guess it would all depend on the context of where it was used"

True, the triangle is probably the most commonly used structural element. We see it time and time again when we constrain our FEA software to certain hardpoints and tell it to fill the enevelope with a part that will handle the predicted loads. The software will optimize the size and shape of the part, modelling all types of shapes and geometries before producing a model of a part that most efficiently meets our requirments. Many of the parts come out looking very organic... It's pretty nifty stuff.

Not sure what to say about a side impact though... any thoughts V?

[nippinout]

Triangles are cheap.

[Danny77]

I thought the circle was the strongest shape, then the triangle, then the square?

Atleast thats what I learned in 7th grade

[pballinzig]

if u really think about it they said that the triangle is the strongest and the circle is the weakest. the triangle has the least amount of sides a polygon can have and in science my teacher explained to us that a circle is jus millions and millions of sections of straight lines. if u take a circle the diameter of the sun and look at it from a foot away the line would seem to be straight