Connections

[Mark]

Looking at some large, clear, glittery helium balloons left over from a birthday party at my house today, I wondered if there was anything fun I could do with them. I tried to imagine how an atmosphere of helium and oxygen, say you replaced the nitrogen percentage in air with helium, like some deep sea diver might, and used this brew to run a pulsejet with a common fuel like methanol. I wonder how much if any it would step up the frequency of the pulsejet?
I learned a new word reading this article. [pulsatile] I think we need to start using this word more. Imagine such a remark, "I think your Logan is suffering from pulsatile instability." ha
I kind of like the strange flames on the link below too.
Mark
http://www.engr.uconn.edu/~cetegen/cete ... hproj.html

[larry cottrill]

From the last picture on that site, it makes me wonder whether you would get turbulence when you wanted it.

The mixtures used by divers for deep diving are not simply replacing the nitrogen in the air. The oxygen must be greatly reduced for great depth. People commonly assume that helium mixtures are used to eliminate "the bends" - this is not true. The point is to reduce the partial pressure of oxygen below toxic values at high pressure. Helium mixes are often as low as 4 per cent oxygen, and decompression stops from great depths are just as necessary as if nitrogen were involved; possibly more so. Another effect of the helium mix is that helium atoms invade rubber suit parts, which then try to expand radically as you come to the surface.

Supposedly, helium bends are "worse than" nitrogen bends, although that may just be legend, or may simply be due to the greater depths involved. I used to have a copy of the US Navy diving manual, and it had extensive information on mixture diving, but of course that's not what I was interested in at the time so I didn't exactly memorize it.

L Cottrill

[Mark]

I remember an old show with Jaques Cousteau and listening to squeaky voices using helium on some deep dive. I didn't know about the low ratios of oxygen, or how mixing O2 and He works out at the greater depths and pressures. I have seen a video of a diver underwater high on nitrogen though, it was kind of funny listening to his light hearted musings and he didn't suffer any harm. Then again I have seen some stressed hyperbaric chamber treatment scenes too.
I think there was an astronaut that kind of zoned out while on a space walk, although it was more of a setting kind of high. Or maybe it was just my imagination, running away with me.
Some days when I was working for a hot air balloon business, I would take a few breaths of helium from the tank we carried and used to release balloons to see how the wind was doing. I remember reciting "Mary had a little lamb" and hearing how funny the frequency of my voice had changed.
Mark

[pezman]

The helium in trimix is definitely there to help prevent the bends. The basic reason for using helium is that it diffuses into and out of human tissue is much more rapidly than Nitrogen, and it is similarly inert. Basically, you get a decompression obligation faster, but you off-gas the He faster as well, so your deco time is reduced.

On the decompression phase, divers generally try to breathe O2 at the upper end of the safe limit of partial pressure (about 1.4 ATA). Anything above a partial pressure of 1.6 ATM O2 raises a risk of central nervous system toxicity. Above 20 feet or so, they generally breathe pure O2, since it allows diffused gasses (He, N2 or whatever else) to diffuse out at a rate comparable to being in an absolute vacuum, w/o the risk of micro-bubbles.

The bends are a very odd beast. I was glossing over a tome on "basic" decompression diving and the diffusion dynamics are complex and very non-linear. If you get a bubble, it can promote additional bubbling. Even the best divers under the most careful profiles risk a hit, so one day you might tempt fate and get away w/o a scratch and another you can follow all the rules and end up in a deco chamber.

The more I learned about bubble blowing, the less I wanted to do it and I pretty much stick to freediving now -- when I dive at all. Cheap, very "zen" and you can pay attention to surroundings rather than equipment. The main risk is that of blacking out and this usually has a "binary" outcome -- you wake up unharmed or you don't wake up. You can get bent freediving too, but you would really have to work at it.

[Mark]

"Helium is our friend."
Mark
http://www.cisatlantic.com/trimix/descrip.htm

[Mark]

What might this have been? Might it have supported pulsating combustion?
Mark
http://cgi.ebay.com/Model-Jet-Engine-18 ... otohosting

[Mark]

This kind of looked interesting when the bid was $10.00. I would have liked to jam jar it or tried some variations on a theme.
Mark
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... otohosting

[Mark]

Strange item.
Mark
http://cgi.ebay.com/VARIAN-VACUUM-DEVIC ... otohosting

[Mark]

Sound reduction with a Helmholtz Resonator
Mark
http://techdata.mi3si.org/removeresonator.htm
http://www.popularmechanics.com/automot ... 88037.html

[Mark]

http://cgi.ebay.com/high-voltage-SCR-Co ... dZViewItem
http://cgi.ebay.com/High-Voltage-SCR-fo ... dZViewItem

[Mark]

Another pulsejet to toy with or modify or whatever you can think of to try. You can just make out the tiny spark plug in the top left bag with the tail clamp. That tail clamp fits a little loose, it isn't made to hold the jet other than to keep the tail stationary I think.
Mark
http://imagehost.vendio.com/bin/viewima ... idpay&sp=1
http://cgi.ebay.com/NIB-Bailey-Sport-Je ... dZViewItem
And another with a common but clever mounting method.
http://cgi.ebay.com/Dynajet-Pulsejet-Pu ... otohosting

[Mark]

Interesting inventive photographic technique. The abstract idea someone had for this whether discovered by accident or intentionally, anything that creates and makes you FEEL something is helpful, no matter how unlikely. Dream a dream, see what becomes of the newness.
Mark
http://www.flickr.com/photos/tags/camer ... teresting/

[Mark]

A curious shape, would be fun to try something weird like this with modifications in a pulsating combustion test. By the way, with all the types of pulsejets out there, there aren't as many jam jar philosophies. It might be fun to make a new kind of jam jar operational. Scroll down on the link to see the actual glassware.
Mark
http://cgi.ebay.com/Five-5-Lab-Glass-Th ... dZViewItem

[larry cottrill]

And another with a common but clever mounting method.
http://cgi.ebay.com/Dynajet-Pulsejet-Pu ... otohosting

The engine mount on my Buzz Bomb Trainer is exactly like this, but trimmed down "to the bone" - a 1/16-inch hard aluminum sheet ring 1/8 inch wide all around, with a lug at the bottom that bolts through a hardwood post with two no. 8 machine screws. There's a little ancillary "saddle" mount of aluminum sheet on top of the fin just in front of the rudder, which steadied the tailpipe via a hose clamp. Those two points were all there was to hold the engine on the model.

This is a very common and logical mounting for a Dynajet or Tiger Jet (or any engine designed with a head that threads into the pipe). On a model like mine, it looks downright frail - but it only has to hold 4.25 lb thrust, plus any vertical or lateral G-forces. No extra beef for crash forces, though.

L Cottrill

[Mark]

http://cgi.ebay.com/JETEX-MODEL-AIRPLAN ... dZViewItem