13 replies to this topic

[TAiLsChaser]

Well instead of trying to use my fragmented memory of physics to get something interesting across, I decided to use SpaceCAD and its calculations.

From recreating a Streamline dart, I found its stock stabliity, center of gravity and center of pressure (look it up). I have pictures from the program to illustrate just what I'm talking about.



I've used this reconstruction and tinkered with it.

First, I just cut off an inch of foam.



After that, I used someone's idea of how to make a stefan dart using a SL.



As a fourth exploration, I recreated someone else's example of a proper stefan (no dart head, just foam).



And lastly, I cut an inch off the proper stefan.



I guess that's why bullets are the way they are.

If there is anyone who'd like to challenge or doubts SpaceCAD, I could email the program to you.

Perhaps this will start a revolution.

[Prometheus]

Could you email the program to me anyways? Everything looks accurate, makes sense. Nice work.

[TAiLsChaser]

Could you email the program to me anyways? Everything looks accurate, makes sense. Nice work.

I just sent it out. It's a .rar file so you'll need WinZip to open it. Plus, I added a .roc file that holds one of the pictures I posted so you can have the data I used.

[Retiate]

I don't get it, what was being made wrong? Looks to me like the short Stefan with a hotglue dome and weight in the front had the best stability. Isn't that how all Stefans are already made?

[TAiLsChaser]

I don't get it, what was being made wrong? Looks to me like the short Stefan with a hotglue dome and weight in the front had the best stability. Isn't that how all Stefans are already made?

I'm just stating that some people out there have been making them wrong. I'm clearing up as to how and why. I'm sure there are a lot of people that make them right but have no idea as to why they are "correct." Plus, I wanted to add the idea of using short darts. As you saw, they turned out alright.

[Retiate]

Ok, so it was the dart length that was making them unstable. Was that dart 1" in length?
I've got a few questions now...
Did you try cutting the dart down further and checking stability?
What about making it a bit longer?
What about different weights?
Is it possible to place the wait a bit off center on both a 1" dart and 2" dart to see which has a greater effect?
I'm pretty sure almost every dart we make will have the weight a bit off center, and if the 1" darts turn out more unstable with a slightly off center weight than 2" darts, then it won't really be worth it.

This program could end up being real handy. I'm guessing a stability of 0 is best, right? Maybe we could find the right length that gets us closest to that, as long as the darts don't end up being like a half an inch long.

[TAiLsChaser]

Ok, so it was the dart length that was making them unstable. Was that dart 1" in length?
I've got a few questions now...
Did you try cutting the dart down further and checking stability?
What about making it a bit longer?
What about different weights?
Is it possible to place the wait a bit off center on both a 1" dart and 2" dart to see which has a greater effect?
I'm pretty sure almost every dart we make will have the weight a bit off center, and if the 1" darts turn out more unstable with a slightly off center weight than 2" darts, then it won't really be worth it.

This program could end up being real handy. I'm guessing a stability of 0 is best, right? Maybe we could find the right length that gets us closest to that, as long as the darts don't end up being like a half an inch long.

No, I haven't checked that just as of yet but I can in a few minutes or so (questions 1 and 2). What amount of weight are you wanting to use? There are a lot of possibilities and since you're asking, I'd like to suit your needs.

If off-center you mean, put it behind the dome or stagger the weight (if say, they were BB's). Yeah I guess that's possible. I really just need a bit more specific questioning to get exactly what you want.

As for the scale, no. Zero is not the best by far. There are positive and SpaceCAD, since it is used to create rockets and present theoretical data as far as performance and what not, it doesn't suggest anything is really stable until about +1.5 to 2.00 calipers.

[penguin807]

Thanks TAILsChaser, now I can give proof to my cousin that he needs a weight at the end of his stefan. When I get some free time I'll have to see how I can improve the Titan missle.

There's a 30 day trial on the spacecad site if anybody is intrested.

[TAiLsChaser]

Thanks TAILsChaser, now I can give proof to my cousin that he needs a weight at the end of his stefan. When I get some free time I'll have to see how I can improve the Titan missle.

There's a 30 day trial on the spacecad site if anybody is intrested.

Glad to help. And yes, a trial is cool and all but the one I could send you is already fixed. You don't need to install. I'll work in its folder.

As I see it, the more people who know and the more people who have the power to do something, the greater chances of a new world to be made.

[Retiate]

Here's a quick paint picture of the off center weight.

I don't know if SpaceCAD will measure stability that way... If that makes sense...

I use a single 3/0 split shot weight (non-removable, doesn't have those wings). Since the package doesn't show the weight of a single one, I can't really compare it too well to the triple BB set up. I also don't have any accurate scales that measure things that small.
How's the stability for a dart 1.5" in length? That's what my darts are currently at.

[Retiate]

Sorry, internet's messing up...

Edited by Retiate, 17 December 2007 - 05:53 PM.

[TAiLsChaser]

No, I'm afraid SpaceCAD can't do an off-center weight like that, but, considering that the position of the weight could be 360 degrees at a particular radius, I'm sure if you found a way to calculate its weight from any given point, you might get your results. I may be past Calc 3 but I can't really think of a way to concretely get an answer for you.

Oh yeah. If you're talking about my "proper made stefans," a 1.5 inch dart will be at -0.44 calipers. That's only about .07 worse than the one-inch.

[Flaming Hilt]

So what you're saying is that the perfect dart is about 1" long, has a hot glue tip, and uses 1/10 oz (~3 BB's) as a weight?

Just want to make sure I got it down so -- you know -- I can start making them.

Edited by Flaming Hilt, 17 December 2007 - 09:39 PM.

[TAiLsChaser]

So what you're saying is that the perfect dart is about 1" long, has a hot glue tip, and uses 1/10 oz (~3 BB's) as a weight?

Just want to make sure I got it down so -- you know -- I can start making them.

I don't know about perfect. Yeah this dart is a an inch and a quarter but all this post is saying that, a short dart like that is more stable. However, since i decided to cut an inch off an dart earlier. My mave nor my firefly could shoot them. The only gun I have that could was my PSII. Stability is only accuracy. I'd test to make sure the short dart gets the same distances. So, don't teach the short dart idea as law now. Sure it will be a more accurate dart but unless your gun can shoot it, don't use it. I guess try making one and see if it works for you. From what I can tell, you need some real power to push it through.

PS.

I respect you for posting on my topic. To be one of the first 2000... You and the other 1999 are what forged NH to be what it is today.

Edited by TAiLsChaser, 17 December 2007 - 09:47 PM.