Search found 1202 matches

by Lentamentalisk
Mon Oct 25, 2010 8:12 pm
Forum: Ammo & Parts
Topic: Glowing Projectile for Night Flights
Replies: 10
Views: 1919

That isn't fin stabilized. It is fin-destabilized. Putting fins above the center of gravity will actually cause it to tumble. The fins should really only be on the rear 1/3 or so of the projectile, and absolutely should stop at the center of gravity. Still, a very cool projectile. I remember a while...
by Lentamentalisk
Thu Oct 14, 2010 10:20 pm
Forum: Pneumatic Cannons
Topic: Pneumatic Beer-Launching Fridge (w/pics, videos)
Replies: 9
Views: 3714

Looks pretty cool. Your canon gave me another idea for a beer launching device, or rather, more of a mortar. The idea is to have a co-ax, where you drop the projectile down the barrel. As the projectile falls, it builds up speed, and when it reaches the bottom, it hits the piston/diaphragm, cracking...
by Lentamentalisk
Tue Sep 28, 2010 9:03 pm
Forum: Off-Topic Hobbies
Topic: Vacuum Balloon
Replies: 35
Views: 5179

Right, you don't think it will work because nobody has gotten it to work yet. Your logic doesn't work though. Submarines work. A submarine can gain buoyancy in water, despite the metal shell having a higher density than the water that surrounds it. In theory, with strong and light enough materials, ...
by Lentamentalisk
Tue Sep 21, 2010 11:24 am
Forum: Hybrid Cannons
Topic: Semi-Hybrid?
Replies: 11
Views: 1865

Wow, that photo is downright spectacular!
by Lentamentalisk
Sun Sep 19, 2010 12:14 am
Forum: Off-Topic Hobbies
Topic: Applying to College
Replies: 15
Views: 1307

I've lived in Berkeley since I was 2, and it looks like a pretty good school. It is BIG. I spent time down in the combustion labs when they have their open campus days, and that was a whole bunch of fun. How much is accessible to you as an undergrad, I have no idea, but as they say, its better to be...
by Lentamentalisk
Sat Sep 18, 2010 6:59 pm
Forum: Off-Topic Hobbies
Topic: Applying to College
Replies: 15
Views: 1307

I just started at University of Vermont for ME. While not particularly well known for ME, it has quite a good program. On of the things I was most looking for was actual hands on work, of which most "good" engineering schools have surprisingly little of. Make sure to ask the students when you visit,...
by Lentamentalisk
Sat Sep 18, 2010 6:28 pm
Forum: Hybrid Cannons
Topic: Pop-Off hybrid valve
Replies: 23
Views: 2416

The issue here is how easily the piston will crack if you use a spring. Even with just .75" of piston exposed, the compressed gas pre-ignition will be exerting somewhere in the 100lb range (assuming a highish mix). The entire point of a hybrid is that it bursts at or near the peak pressure, exerting...
by Lentamentalisk
Fri Sep 03, 2010 11:11 am
Forum: Off-Topic Hobbies
Topic: Vacuum Balloon
Replies: 35
Views: 5179

Carbon fiber would not help. Carbon fiber has a particularly high tensile strength, but not a very high compressive strength. Thats the idea with styrofoam. Its generally pretty good at resisting compression. For certain, it wouldn't be practical on a small scale. But then again, anything smaller th...
by Lentamentalisk
Thu Sep 02, 2010 11:09 pm
Forum: Off-Topic Hobbies
Topic: Vacuum Balloon
Replies: 35
Views: 5179

Vacuum Balloon

Ok, here is a question in the exact opposite direction of what we deal with normally. I want to make a negative pressure chamber. I am trying to figure out a way to build a vacuum lighter than air ship. STOP. Don't tell me it is stupid. I know, helium and hydrogen, and just about everything is more ...
by Lentamentalisk
Tue Jun 15, 2010 7:34 pm
Forum: Off-Topic Hobbies
Topic: Knife Thread
Replies: 821
Views: 58375

Not a big knife person myself, but my Leatherman Blast never leaves my side. I also made a non-metallic knife out of aircraft plywood, fiberglass, wood glue, and cyano acrylate (as a hardener). I am sure the tip will dull rapidly, but honestly, all you need is one or two good stabs. I am working on ...
by Lentamentalisk
Sun Jun 06, 2010 4:50 pm
Forum: Off-Topic Hobbies
Topic: Perhaps the coolest rocketry video I've ever seen...
Replies: 42
Views: 2454

Wow. Just wow. I have seen a lot of Armadillo's progress, which is damn impressive, but this is just outstanding. Not only is it capable of doing this, but it proves that the vector thrust control is good enough to handle being knocked off course by just about anything. It was able to recover from s...
by Lentamentalisk
Wed May 19, 2010 11:59 am
Forum: General How-To & Discussion
Topic: My Homemade Chronographs
Replies: 13
Views: 3019

To get technical, there are 2 power peaks in one cycle, one positive and one negative. On 60HZ power the flicker rate is 120 times/sec. While the power to your houses may have a 60Hz cycle, florescents do not anymore. With the old magnetic ballast, they would cycle with the power to the house, but ...
by Lentamentalisk
Tue May 18, 2010 7:52 pm
Forum: General How-To & Discussion
Topic: Supersonic Airsoft BB's
Replies: 27
Views: 6544

The issue is that the "speed of sound" is how quickly sound travels, on average, not, as DYI said, the speed of the individual particles. The particles have a mean speed of the SoS, but then there is an approximately normal distribution on either side of that. It is theoretically possible to acceler...
by Lentamentalisk
Thu May 13, 2010 3:45 pm
Forum: Off-Topic Hobbies
Topic: Lathe Accident Pictures
Replies: 63
Views: 10462

"Shopped!"

[/tasteless humor]
by Lentamentalisk
Thu May 13, 2010 3:40 am
Forum: Ammo & Parts
Topic: Projectile Aerodynamics Research
Replies: 9
Views: 1900

At last! I finally found what I had been searching for! http://www.frfrogspad.com/drgshape.htm http://www.frfrogspad.com/coefdrag.gif I'll let you all know what we find out, though it may not be too unobvious. Pointy things go farther, straighter, faster. As you get farther from the target, your aim...