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Fume Hood

  1. Mar 4, 2009 #1
    I just bought this squirrel cage fan off ebay. My idea is to use it for a fume hood. According to seller it runs very well; I will clean, oil, and throw a coat of a paint on it. Got it for 20 bucks. The motor is completely separated from the cage as I wanted. However, it gives no CMF? It is a 1/4hp, 1725 rpm Dayton Wattrimmer motor. I am completely unsure of fan curve, etc.

    Think it will work out?


  2. jcsd
  3. Mar 4, 2009 #2


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    Won't work (safely)... it's not explosion-proof and is made of soft steel which will corrode like crazy. It might work briefly but never safely. Notice the bearings are in the path of the nasties. A sure death sentence for those bearings. Why are you trying to build one?
  4. Mar 4, 2009 #3
    I don't think it matters so much whether or not they are sparkless as long as the motor is outside the flow path... Perhaps the 'bearings' will be an issue, vis-a-vis sparks, uncertain.

    Considering some actually use inline motors, maybe it will last a while. I wonder if I could somehow protect the bearings or even re-locate? LOL!

    As for why I am trying to build a fumehood, I do not understand the question? If it's just a simple interrogatory, then it is because I cannot afford to buy one. I graduated from college many years ago and do not work in the chemical industry, ergo: I have no access to one. In my lab, I use an M40/42 gas mask but there are things where both a gas mask and fumehood would be proper, e.g. HF synthesis.

    Thanks for the reply! Likely I have wasted my money...
  5. Mar 9, 2009 #4


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    (Moved thread to the ME forum for a few more views)
  6. Mar 9, 2009 #5


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    I'd go to a company like American Fan & Blower to see if they have anything comperable to what you have. With squirrel cage blowers, I doubt you'll get any real differences in designs from one company to another. Take the dimensions of your unit and see if you can find something similar.

    Will it work? What do you mean by "work"? It will definitely move air.
  7. Mar 9, 2009 #6
    Didn't realize that the raison d'etre was unclear.

    The question was: "Think it will work out?" This, taken in conjunction with the prior statement: "My idea is to use it for a fume hood", should erase any doubts as to the tasks which would be the fulfillment of its 'work'. To wit, the removal of noxious fumes from the work environment in a safe and reasonably functional manner. A reasonably functional manner, would proscribe exploding, imploding, failure to remove fumes almost completely, along with anything else that a fume hood blower/fan should fail to perform that would be required.

    Mea Culpa for the lack of clarity...
  8. Mar 9, 2009 #7


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    No, the "will it work" refers to a desired flow from the fume hood through a certain amount and size of duct work creating a certain depression within the hood. Go ahead and plumb that up to 200 ft of 1 inch diameter ductwork and see how well it "works."
  9. Mar 10, 2009 #8
    I am unclear as to your meaning.

    Your question was put in quotation marks so I supposed you were referencing my own question which was something different, both explicitly and implicitly. My question was framed within the context of my post per se. And it was, put in different words: WILL THIS FAN/BLOWER 'WORK' PROPERLY WITHIN A FUME HOOD? While I did not specify the exact dimensions of the hood, I took it for granted that it would be one of workable size for an individual within a private lab. The first responder clearly understood it. It is not a complex interrogatory for anyone who knows anything about the function of a fume hood blower/motor. Working does not entail catching fire or corroding away in no time.

    Now you advise me to hook it up to to 200 feet of 1" duct? Unless I am sadly mistaken, that is a superfluous attempt at a slur. Not sure why, though... perhaps, it is just a misunderstanding on my part?

    There are many factors involved among the few different designs of these things. Motor position (direct or belt drive), blade curve, intake and exhaust dimensions, are all considerations. My post is likely too nondescript to be answerable, upon consideration. However, I fear that 'chemisttree' is correct.
    Last edited: Mar 10, 2009
  10. Mar 10, 2009 #9


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    No. I was being dead seious. Your smart *** answer left more than to be desired. I am simply telling you that an open ended question like "will it work" can not be answered unless you define what that means.
  11. Mar 10, 2009 #10
    Fight Fight Fight!.. A random insult to both of you for being not nice to each other.

    FredGavin I think it was semi-obvious that the 'will it work' question was more one of 'will it fail assuming it works in the first place' simply from the way it was phrased.

    Powerlifter my advice would be to not come back with sassy posts if someone doesnt interpret a fairly vague question correctly.

    My gut instinct is, it looks pretty a bit battered and may possibly be fine if the working fluid was air. But as you are throwing potentially flammable material and corrosives at it I wouldnt reccomend it.

    tl;dr Stop fighting, it probably would work but not for long and not safely.
  12. Mar 10, 2009 #11


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    I think Fred's point is that the question needs to be stated a bit more quantitatively, in order to be of help with any calculations. The fume hood I work with here at my work is pretty big, covering two big work stations, and moving a LOT of air. I've seen other fume hoods like at schools, where there was not much air movement, and the enclosed volume was only a cubic meter or so.

    My guess is that the OP's motor and fan might qualify for the smaller hood, but not for the larger ones that we use here. I don't think Fred or I are clear on exactly how the OP wants to use it -- like Fred asked, how big of a hood, how much air movement, and how big of a depression is needed.
  13. Mar 10, 2009 #12
    The volume of air shifted is a non issue if the blades and bearings corrode, or sparks cause the thing to explode. This never seemed like a quantitave question to me, more of a general assesment.

    I do agree with yours and Freds point that vague questions are frustrating, but in this case things got a unnecessarily abrasive.
  14. Mar 10, 2009 #13
    I posted this question: "Think it will work out?" That question is not this question: "Will it work?"

    My reply was not an attempt to be a smartass; if vague. So, feel free not to reply. Under the circumstances, I understand. What do we powerlifters know, anyway? Merely how to lift heavy objects? Self-deprecating humor... take it as that and drop it.

    I wanted to approximate this (on a shoestring budget):

    http://www.grainger.com/itemdetail_largepic.html?item=XL-2C800.JPG [Broken]

    As should be clear, the bearings are not simpatico...

    Here is all of the other detail that I have, as I STILL await its delivery... "Dayton "Wattrimmer" 1/4hp 1725rpm 115v 3.2a Single Phase Belt-Driven Centrifugal Blower Fan in Good working condition!!! Opening measures 12" wide x 10.5" tall."

    I will just wait and see. Ebay is a crapshoot. I bought Fisher DA4 Maxima Vacuum Pump for ~200 bucks, got it home cleaned it up, and it is both aesthetically and mechanically pleasing.

    Maybe it will suffice for a modest hood with short exhaust runs, long enough for me to put together a few bucks for something proper. (Assuming it doesn't explode!!!!!!!!!!!) :)
    Last edited by a moderator: May 4, 2017
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