I want to make a portable smoke generator

[JackMcCornack]

Thanks, that should hold me for a while. chuckm, I followed your links, and found a product at Granger (90 second chemical smoke generator, 600 cubic feet, no harmful residue etc blah blah) that seems worth the risk for an experiment. At nearly 7 cf per second, it should be visible to 60 mph as a discrete line of smoke. I'll get a box of 10, fabricate some sort of chamber/wand for it and report back.

Re the legality, well...I don't plan to do it in town, I'll carry a copy of Mother Earth News with me so I can show it's for a good cause, I'll practice my innocent smile ("But officer, smoke generators weren't mentioned in the driver's handbook and it wasn't on the test!") and once it hits my wake I believe it will be diluted about 80 to 1 by the surrounding air and not too noticeable. I think I can be discreet--we have a lot of low occupancy roads in rural Southern Oregon--and surely I can talk my way out of getting my car impounded if I proooomise I'll nevernever do it again.

As for oil-in-the-exhaust generators--I've used corvus oil in my air show performances (yet another aspect of my misspent youth--if I ever write an action-adventure novel I have the "about the author" credits in the bag) but the high cfm is going to put the car in a cloud, not produce a discrete stream of smoke. Ditto re skydivers' smoke generators, they too make a huge amount of smoke. Ditto re following a smoke generating car--its wake is going to scramble the smoke into a cloud. Y'all may already know that stuff; sometimes it's hard to tell when somebody is kidding on the Internet.

I think smoke-on-the-fly might be an interesting alternative to tuft testing and/or oil-and-lampblack testing if it can be done cheaply (and discreetly) enough--and a $20 box of chemical smoke generators is less threatening to the wallet than a $1000 oil vaporizer. So give me a couple weeks and I'll tell you how it worked.

PS--Frank Lee, you may be right, it might be better to make the wand moveable rather than reposition it every trip. Maybe I can make something passenger-actuated.

[aerohead]

When you arrive at your moment of temporary insanity,please get someone to record it so we may all benefit from it, as well as pass the hat to raise funds to bail you out of jail.Kidding!------------ I'm not admitting to anything myself,but Estes model rocket dry-cell ignition systems make a great way to ignite fuzed smoke bombs that find their way into a perforated metal can which has stolen a ride on a persons rear bumper late at night on a deserted road where flash photography can capture the image of the smoke trail which a light breeze safely blows from the test track,away from any unsuspecting motorist who might happen along about then.

[Frank Lee]

DON'T DO IT!!! When Homeland Security catches you doing your terroristic activities they will either blow your brains out all over the road or send you to Guantanimo.

[instarx]

I used to do nuclear clean-room filter testing and duct tracing using smoke generators. Google DOP or dioctyl phthalate smoke generators. You can buy them or make them. Some are as small as a tin can. It will take some compressed air and a small heat source. They produce tons of smoke and it is harmless stuff. It is theatrical smoke and is what you've seen being produced in wind tunnel tests.

[instarx]

Coincidence? Portable fog generator advertised in my local Home Depot flyer yesterday for $29.95.

[MetroMPG]

FYI, someone who has worked in wind tunnel testing provided me with this information:

The stream is not actually smoke, which comes from combustion, but condensed oil vapour that forms a cloud, like steam, but more persistent. One material used is polypropylene glycol (this is not antifreeze, which is polyethylene glycol). I think that fog juice, used in the theatre industry, is primarily polypropylene glycol. It is passed through a small diameter stainless steel hypodermic tube (1/16" od) and heated by passing a current through the tube, which should be insulated and held inside an outer, non-conducting tube, like a large hollow fishing rod. The overall length is between 2 ft. and 6 ft., depending on requirement. A variac or variable current DC current supply can do the job. The voltage need not exceed about 25v.

Aerolab sells such a product. Look at www.aerolab.com select the tab 'speciality' then 'smoke generators'.

EDIT: link to smoke generator brochure PDF from that company - http://www.aerolab.com/downloadable-...enbrochure.pdf