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Liger Zero
06-17-2010, 11:48 PM
...does anyone sell a complete unit? Something that fits in a duct. I have an idea that would require a fan. Due to limitations in the electricity supply at the intended location I need an alternate energy supply. There is plenty of compressed air though.

More or less it is a vent hood over a rubber mold at a friend's shop. Going to set it up on a trip-switch so the mold opens the fan comes on and sucks the peroxide fumes up. Then a timer kicks the valve shut so there is no draft over his hot mold.

The rubber is a thermoset EPDM material, it is injected "cold" into a "hot" mold where it cures. When the mold is opened a huge cloud of peroxide fume and rubber smoke flows forth. Can't suck too much air over the mold because it throws off the thermal balance.

His shop... less than ideal. It would be a hardship to run another 120v line at this point, but he does have more compressed air than he possibly needs.

lakeside53
06-18-2010, 12:17 AM
Just blow the air down the duct.

darryl
06-18-2010, 12:24 AM
What about converting a simple air tool to drive the fan? A die grinder would be my choice, and for a couple of reasons- it already has an output shaft on bearings, and a way to mount the fan. The fan needs a 1/4 inch diameter stub, that's pretty much it. Second reason- the fan would load the die grinder down so much that its air consumption would be drastically lower than it would be in its intended use.

You would probably just wire the trigger bar down to the body and run it using an inline air valve on the line somewhere. Using a typical quick disconnect, you would have a place to occasionally drip some air tool oil.

You could set it up such than the air valve is opened to some degree when the mold lid is opened.

CCWKen
06-18-2010, 12:27 AM
No need for a fan. If you have compressed air, fix a jet in the center of the duct to blow the air out. This action will cause a vacuum behind the jet and draw air into the duct from the other end. It's the same principle used in the air powered vacuum "pumps".

wierdscience
06-18-2010, 12:37 AM
Just blow the air down the duct.

+1,just turn a 90* elbow into the center of the duct and add a 8-10" long nipple.Works just like a locomotive stack blower-


http://www.trainweb.org/tusp/sergio/lempor_stack_f_2.jpg

Duffy
06-18-2010, 12:51 AM
There is a whole science to ejector design. Large, perchloric acid fume hoods use ejectors instead of an in-line fan. Why not use a small muffin fan powered from a battery pack? . Even a fairly large one only draws a few watts and it IS intermittent duty. A 12v fan and a hefty gel battery should work a treat and it has the benefit of microswitch control. I assume this thing only has to run a dayat a time, then recharge the battery.

darryl
06-18-2010, 04:05 AM
Not sure how much flow you're going to need to extract the fumage, but it will probably be pretty significant- I'm thinking more than a few muffin fans could handle. Also, I do have a cupple problems- do you not have light there? And is there not a need for SOME electricity in that whole process? And how is the air compressed without electricity?

I might be inclined to go along with the battery and 12v fan idea. You could always set up a solar charger to keep the battery up, and maybe use a heater blower motor to remove the fumes.

It is beginning to sound like there's a lack of willingness to bring electricity to the area, though it really should be done for the sake of the project-

Liger Zero
06-18-2010, 06:13 AM
The lack of electricity has more to do with the absolutely decrepit building that houses his shop and the unwillingness of the land-lord to allow anyone to run additional lines from the breaker system downstairs. It's one of those "business incubator" deals where you rent a bay, start your business and then move out once you are underway.

With all the stuff he has to run as secondary equipment off of the existing lines, tripped breakers are a daily event for him.

Compressed air, however... is supplied from three big rotary compressors down in the basement and a smaller secondary Tractor Supply upright compressor in his shop. Air is virtually free.

Thanks for the "stack blower" tip, that'll reduce the number of moving parts. I have extensive notes from my material loader design session more than likely I can scale that up.

Farbmeister
06-18-2010, 07:50 AM
What about the NOISE of a high pressure jet of air in a metal duct?

If breakers are tripping daily then he as more issues than airflow.

I would demand my 'bay' be up to code... threaten a complaint. This guy has little chance of making it in the business world if he can't get electricity right, or negotiate/pay for proper facilities.

pressurerelief
06-18-2010, 09:06 AM
Coppus Air Blowers make several different types of air powered fans. They are intended for flammable atmospheres and other specialty situations so hold onto your wallet. They may give you an idea of what you can do though.

Take a look at, http://www.directindustry.com/prod/dresser-rand/air-mover-13998-350531.html

P/R

davidh
06-18-2010, 09:30 AM
look at a "air mover" from "texas pneumatic". similar to a stack blower maybe ? ? ? and they don't cost much !

Black_Moons
06-18-2010, 01:31 PM
+1 vote for Venturi design.

Die grinder is too high of RPM's to attach to a blade, air drill would be about right...

If the guy won't let *you* run new lines to the breaker, how about a lisenced electrition, yea we all know you can do it 'good enough', but how about just paying the proper guy for all the insurance reasons, you can be his 'apprentice' and do the dirty work to speed up the job (Drilling joists, running wire, etc)

If done on your dollar, to code by someone with proper lisenceing/insurance/certs and it improves the landlords building, whose he to complain?

brian Rupnow
06-18-2010, 04:15 PM
Search my threads and find the plans for a 5 cylinder radial steam engine. That will run just fine off compressed air, and will operate a fan with no problem.---Brian

alanganes
06-18-2010, 04:38 PM
You may know of this already, but take a look at the Exair website (http://www.exair.com/en-US/Primary%20Navigation/Products/Pages/Products%20home.aspx).

Lots of air powered air moving stuff of all sorts. I once saw one of their "air operated conveyors" used in a similar application, though not for molding. It was used to suck a bunch of dust laden air from a smallish space before it opened, to keep from contaminating a workspace. Pretty cool, and seemed to move a ton of air inn relation to the compressed air it took to run it.
-Al

Liger Zero
06-18-2010, 05:13 PM
I googled up several dozen suppliers and came up with some expensive solutions. Cheapest method right now will be a stack-blower design, I'm CADing one up right now.

Airflow is the problem I am contracted to solve, I don't have any "power" over the landlord/electric issue... nor is it my place to get involved.

I did however suggest that a move to a better business-incubator may be a sound decision.

Mark McGrath
06-19-2010, 03:06 AM
Why not take an electrical feed out of the machine panel.Keep it all together.
Compressed air is a very expensive energy medium to use on something simple like this.Electrical power is already at the machine.

Liger Zero
06-19-2010, 08:19 AM
That is an option yes... but as I said above compressed air is free at this location, it is supplied by the landlord. There are three huge rotary compressors in the basement that provide air to all the wee businesses. It is not metered, he doesn't charge for it in any way.

Ergo, this is the energy source I am tapping.

Peter.
06-19-2010, 08:26 AM
It's going to make a heck of a noise though. I bet a 1/2" open pipe will put out over 100 decibels.

Liger Zero
06-19-2010, 08:38 AM
It's going to make a heck of a noise though. I bet a 1/2" open pipe will put out over 100 decibels.

Trick is throttling it back so it "just" pulls some of the fumes and redirects them. I don't need a full power blast.

Going to the store in a little while to pick up some duct-work and supplies.

metalmagpie
06-19-2010, 03:10 PM
I used to work in the shipyards. We would always be down in some horrible oil tanks big enough to put my whole house in. Fumes for days. They used air-powered fans over the hatch covers to circulate fresh air so we didn't all die down there. Those things were REALLY LOUD!! If you didn't have earplugs in you would have been deafened really quickly. Think of your head inside a huge drum being beat on with sledgehammers. Insanely loud.

Don't commit to something before you think about the noise. Please.

metalmagpie

Paul Alciatore
06-19-2010, 03:41 PM
You could use the compressed air nozzle to directly drive a full sized fan. Aim the air at the outside edge of the fan from the upstream side and allow it to drive the fan. Aim it to strike the fan blades at 90 degrees. Adjust compressed air flow to adjust the fan speed. If a single nozzle offends your sense of proportion/balance, add a second one on the other side. If it makes too much noise, add some sound absorbing insulation inside or outside of the duct - or both.

Liger Zero
06-19-2010, 04:24 PM
My prototype at 30psi is no more louder than a big electric shop fan. It also clears my work-bench of "canned smoke" in about 30 seconds.

Go up above 50 PSI and you get a nice suction that moves a decent volume of air but it becomes about as loud as a power-saw rip-cutting a 4x6. window

I then built a cage out of wood around it, packed it with fiber-glass and put paneling on the outside... that dampens some of the noise... of course the ass-end where the air comes out makes quite a racket but the solution there is to duct that through a window , let the outside world deal with it. If we vent it through the window to the back lot it'll be fine... window looks out over a brownfield, nearest neighbor is an abandoned warehouse about 700' away.

Looks like about $400 build the duct-work, build cages and pack with fiber-glass and build a foot-switch controller. Approach the mold, step on the foot switch to clear the air, then step off to prevent a draft over the mold.

Mad Scientist
06-19-2010, 05:50 PM
Probably not big enough.
two cylinder double acting "air" engine running a fan.:)

http://i68.photobucket.com/albums/i17/mscientist/projects/p16.jpg

davidh
06-19-2010, 06:18 PM
Go up above 50 PSI and you get a nice suction that moves a decent volume of air but it becomes about as loud as a power-saw rip-cutting a 4x6. window
.

move and mount the noisy end at the window / wall opening and duct back to where you want the smoke / whatever pulled from. thats how the air movers i suggested you look at are used,

as an example, we drop a suitable duct hose into the top of a tank truck, and put the inlet right near the floor. the air mover itself is on top of the tank, and all you hear inside the tank is the whoosh of the air being exchanged. . .. . . they have such a suction that if you drop a shop rag into the duct ya better not be standing by the end of the mover . . . . or ya get the slap crappped outta ya by a rag.

oldbikerdude37
06-19-2010, 06:30 PM
Probably not big enough.
two cylinder double acting "air" engine running a fan.:)

http://i68.photobucket.com/albums/i17/mscientist/projects/p16.jpg

sweet I bet it would do the job and not suck cold air over the mold.

Liger Zero
06-19-2010, 06:34 PM
move and mount the noisy end at the window / wall opening and duct back to where you want the smoke / whatever pulled from. thats how the air movers i suggested you look at are used,

as an example, we drop a suitable duct hose into the top of a tank truck, and put the inlet right near the floor.

...brilliant. THANK you.

This is why I ask ya'll for advice. ;)

Liger Zero
06-19-2010, 06:36 PM
Probably not big enough.
two cylinder double acting "air" engine running a fan.:)

http://i68.photobucket.com/albums/i17/mscientist/projects/p16.jpg

I'm sure that would work but I honestly don't have time to build it right now. ;) Oh and where do I get plans from? :D