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New Kickstarter with Caverns (Not DF, sadly)
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TOPIC: New Kickstarter with Caverns (Not DF, sadly)
#59471
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
Forgot: CrystaCal has a compressive strength of 13 MPa, which is 1886 PSI. Not very hard at all. (Thod's orc tower)

Excalibur is 10x stronger.

What I'm telling you is that I've used Excalibur for years, doing my own stuff and commissions, and it's VERY tough material. Again, if it breaks, it will either chip a little tiny bit (corners) or it will crack along the weakest path - the glue lines.
superflytnt
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5x Dwarvenite KS1 + 1x CoS + 1x Dungeon Dressing
1x Rooms and Passages
1x Traps I
1x Den of Evil Expansion
1x Ice Cavern
1x Wicked Additions II
+ Various individual pieces
 
#59473
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
This is all very interesting but doesn't really mean much to me as it is only numbers to me.....how about someone just does a drop test?

Dungeon stone piece
Excalibur casted piece
Dwarven Forge Resin Piece
Dwarven Forge Dwarvenite piece

all pieces should be the same shape and should be dropped from 4ft high in precisely the same manner...then we shall see...and he who is strongest shall be king:)
Stefan
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Stefan Pokorny

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#59475
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
Stefan, I feel the Dwarvenite should be given a reprieve for this test; it already fell off of a water tower and managed to stick the landing with a perfect 10. I don't know if it needs any more emotional trauma. ;)

Though I don't know much about plasters and resins, I know dwarvenite is nigh unbreakable with drop tests. Maybe for the caverns KS you could drop it from an airplane? :)
AnimeSensei
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#59478
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
AnimeSensei wrote:

Though I don't know much about plasters and resins, I know dwarvenite is nigh unbreakable with drop tests. Maybe for the caverns KS you could drop it from an airplane? :)


Excellent idea. I volunteer my backyard as the landing zone.
Kodiak3d
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Sets owned:
2 Cavern
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1 Room
2 Game Tile sets + bonuses
 
#59488
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
AnimeSensei wrote:
Stefan, I feel the Dwarvenite should be given a reprieve for this test; it already fell off of a water tower and managed to stick the landing with a perfect 10. I don't know if it needs any more emotional trauma. ;)

Though I don't know much about plasters and resins, I know dwarvenite is nigh unbreakable with drop tests. Maybe for the caverns KS you could drop it from an airplane? :)

Lol! Haven't you watched Mythbusters?... ;-) All you need to do is drop it from a sufficient height for it to hit terminal velocity.
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Me: "Sharpness 1, Knockback 1"
Daughter: "Oh man, that's sweet!"
 
#59491
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
Of course I've seen Mythbusters, but I feel that following that lead and blowing up the Dwarvenite in the end would be a waste! :)
AnimeSensei
MBS and Catacombs in Dwarvenite, please!
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#59502
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
Kodiak3d wrote:
[Excellent idea. I volunteer my backyard as the landing zone.]

This put a smile on my face all day long!

I vote this as Post of the week (narrowly beating out Jackattack accusing LordDust of being Frankenstein)
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#59504
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
I gotta admit that I find the Deep Blue and the Magma paintschemes very striking! Not sure if those are actual options because the update I found them in said backers have to vote on these optional schemes.

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#59512
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
Superflytnt,

I don’t have a Ph.D. in physics, I have one in molecular biology. I have a bachelor in Science (B.Sc.) though, which included a few university-level courses in physics, thermodynamics and mathematics. I am not an expert in physics nor have I claimed to be, but I thought my credentials were good enough (not for you apparently) to write about relatively simple physics on a forum gaming section. Could you tell us what type of formation you have and what makes you a better expert than myself? ...I don’t know what “PE/ME” mean and I don’t know how this former job of yours thought you better theoretical knowledge in physics than me.

Now about physics itself...

As you might say, this doesn't have anything to do with anything, other than the fact that you made factually inaccurate statements about the absolute usefulness of compressive strength in the determination of the resistance of a material to breaking in case it is dropped on the floor.

During Izod impact testing, compressive strength is indeed mostly what is being measured. This is because the arm head hitting the material is providing a force on the material that is equal and opposite to the actual clip that is making sure the material stays in place. The material is being compressed between 2 equal and opposite forces. What I think you are not realizing is that when an object falls on the ground, it is being applied a force (by the floor) to ONLY ONE SIDE; it is not being only compressed and I think that is what you’re not understanding and where your notions in physics differ from mine.

When an object is being applied a force, it tries to resist that force and very slightly bends around that force. The surface on the side where the force is being applied is being compressed as it tries to become smaller/shorter. On the opposite side, the surface is being extended and therefore subjected to tensile strength, not compressive strength. This is what I was trying to explain to you in my last post but apparently failed. There are lots of images (from online tutorials about basic principle of physics) depicting this phenomenon in much clearer terms than what I can write such as this one:



Here’s another image that shows the compression zone (in blue) and extension zone (in red) of an object being applied a force upon:



With the “Kung Fu master” example I tried giving you, the wood starts splintering on the opposite side it is hit because its tensile strength is failing its strength check (pun intended) before its compressive strength. Plaster has a tensile strength that is about 10 times lower than its compressive strength. I claim that if it is breaking once dropped on the floor, it is most of the times because its tensile strength fails. This is why pointing out to a high compressive strength as a sole strong indicator of shock resistance is very misleading. In comparison, PVC/Dwarvenite has a compressive strength of 9600 psi (reference) and it is way more resistant to any plaster!

You claim that it is ABSOLUTELY compressive strength that protects a material against shock. On the contrary, I claim that the properties of a material to break upon impact depend ABSOLUTELY on MANY factors including: compressive strength, tensile strength, elasticity, weight density and shape. To illustrate that each of those elements are important I’ll give examples to show that a high compressive strength is NOT necessary and sufficient to measure and/or predict the ability of an object to break upon impact.

Compressive strength: A rope & rubber (these objects have very low compressive strength yet they will never break if dropped on the floor).

Tensile strength: Porcelain has a super high compressive strength (25 000, 50 000, up to 200 000 psi; higher than Excalibur plaster). I’m pretty sure you know the outcome of dropping porcelain on the floor. This means that a super-high compressive strength does not necessarily mean that it will resist impact.

Elasticity: an elastic, a football (They will just deform and bounce back without a dent).

Shape: A piece of Excalibur plaster shaped as a thin rod, even though it might have the exact same mass as a piece of Excalibur shaped as a sphere, will break like a twig if dropped on the floor. The same sphere with a slight dent in it will be much more prone to breaking than an intact sphere.

Weight/density: Styrofoam has a negligible compressive strength. Yet, it won’t break as the force applied by the floor to the Styrofoam will be minimal as it won’t have much kinetic energy (you know about F=M*A right?).


Now, you seem to be from the very skeptical type and you might still not believe or understand me. Perhaps you might be convinced by others?

If that’s the case, I think you should read the following thread on the Hirst Arts forum.

In it, Itar himself (owner of Itar’s workshop) says that Excalibur plaster can break if dropped on the floor and that resin is much more durable. I’m pretty sure you cannot claim to have more experience casting HA pieces than him and that he’s “not an expert” on the matter. Second, please pay attention to what zombieengineer says. He’s a civil engineer (this might qualify him in your eyes as an expert) that has experience casting HA pieces. He basically says the same thing as I do regarding the importance of tensile strength if you want to see how durable your plaster really is.

I’m sorry if my post was extremely long but I hope at least that I made it clear. I really don't like it when someone claims falsely that I don't know what I'm talking about when I do.

As you say, no offense intended in the slightest by the way; I'm simply attempting to correct the record.
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#59516
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
Superflytnt,

I wanted to add the following yesterday but I could not. I am now at work in my research lab and I now have some free time as well as electronic access to the scientific litterature provided by the university I work for. In a scientific publication called the "Australian Dental Research" called "The tensile and compressive strength of plaster and stone" (You can "Google" its first page for free), scientists specialized in the mechanical properties of plaster (you might call them experts) have tested the compressive strength of dental plaster (compressive strength up to about 18 000 psi). They have used plaster in the shape of spheres, which in my opinion is the shape that would be most resistant to a shock of hitting the floor. So, they put these spheres into a compressive strength measuring machine until they broke.



In this setup you can see that there are many designs in compressive strength measuring devices. In this one, two metallic rods hold the sample and two pistons are pushing the first rod against the other. The authors found that many compressive and tensile forces are influencing the crushing of these spheres. This is because some parts of the sphere are outside from the most direct route between the two contact points with the rods. You might therefore say that this test was not only compressive in nature but I believe it is actually reflecting what is happening when an object hits the floor, because a piece of plaster would only very rarely hit the floor while completely flat. Here are a diagram of the several strengths found in these spheres under pressure:



The resulting crush tests showed that the tensile strength of those plaster pieces failed first (cracks alongside the compressive forces) and that they were much more frequent than the compressive cracks:



What I would like you to retain from these lengthy post of mine is that when someone such as myself politely asks you not to make statements about his knowledge (or his lack thereof) about a subject without yourself actually knowing if that is indeed the case and that he finds it offensive (my supposed lack of experience in casting HA pieces preventing me to speak meaningfully about it), the proper response is ABSOLUTELY NOT to say that he also lacks knowledge in another field (namely physics, preventing me to say that compressive strength is not very useful in determining the impact resistance of plaster pieces hitting the floor).



Stefan,

You're such a nice guy and I love your forum, art and products. I saw your attempts at potentially defusing an escalating and infuriating conversation and I apologize for my long and factual posts following it. I hope I showed civility and politeness in my counter-arguments. I just cannot let anyone try to affect my reputation; I have to protect it as it is important to me. Can you believe the guy even alluded that he doesn't know whether I'm a good scientist or not?
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#59518
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
biowizard wrote:
I just cannot let anyone try to affect my reputation; I have to protect it as it is important to me. Can you believe the guy even alluded that he doesn't know whether I'm a good scientist or not?

All I'm saying is that you may be an incredible research scientist, but talk about what you know, not what you don't, as an expert.
I actually said that you may be an incredible scientist, but you should not talk about that which you know nothing about, and the fact that you had to go look all kinds of websites up indicates that is precisely what you did.

Here's how it is: Impact testing (drop testing, for instance) doesn't test "shock" as you alluded to originally. That's a different test entirely. It doesn't test tensile strength solely either, which, again, you alluded to originally.

Impact testing tests ductility and hardness, with both being complex vectors of different properties. Impact testing tests fracture, and the really good ones test three failure modes. It's not only compressive strength that's being tested in an impact test - totally true - it's a matrix of ductility and hardness. If the hardness isn't sufficient, the part will fracture. If the ductility isn't elastic enough, it will shear. Impact strength is not measured in terms of tensile/compression/et. c strength, it's measured in joules of energy before failure, not PSI.

The fact is that you were originally trying to say that tensile strength was the salient feature of something undergoing impact, then you said "shock" later, neither of which is factual. This is really beating a dead horse, and as with many hobbyists I've known, the inability to be wrong about anything to the point of ridiculousness has shown it's ugly face. This is the same reason why I can't stand Boardgamegeek. Too many bloody internet experts.

Have a lovely day.
superflytnt
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Last Edit: 2013/12/12 09:23 By superflytnt.
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5x Dwarvenite KS1 + 1x CoS + 1x Dungeon Dressing
1x Rooms and Passages
1x Traps I
1x Den of Evil Expansion
1x Ice Cavern
1x Wicked Additions II
+ Various individual pieces
 
#59519
Re:New Kickstarter with Caverns (Not DF, sadly) 10 Months, 1 Week ago  
Well, I already knew these simple physics principles. You, unfortunately, did not when you started making claims about MY knowledge. Are you requesting proofs of my bacchelor's degree prior to posting here? I had to dig up all those references in order for you to stop saying that I don't know what I talk about. Have a lovely day.
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