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watson.fawkes
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Quote: Originally posted by EmmisonJ  | | [...] they said to just leave a little space between the pulley and the housing when you tighten it down, that you don't really need any type of
spacer, just leave an open space there if necessary. |
While you don't need a spacer, I might recommend a bit
of thread-locking compound on the setscrew for the pulley, since there's often enough vibration in a fan system to loosen screws.
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DJF90
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You could also use a "sprung washer". It exerts axial force on the bolt, preventing it from undoing.
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Magpie
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I like sprung washers and lock nuts also but they are really not appropriate for this application. The pulleys are affixed to the shaft using an
internal hex head set screw.
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EmmisonJ
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thanks watson, i think a thread-locking compound as you recommended is just what i need, if nothing else to help me sleep better at night knowing the
pulley's not going to fly off during operation and hit me in the head 
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DJF90
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Didnt realise it was a grub screw, sorry. For anything where the bolt head resides above the surface then a sprung washer is perfect. If the threaded
end is above the surface than use a locking nut. Alternatively, I believe you could use a sprung washer that end also
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watson.fawkes
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As long as we're talking about motor-sheave-belt-fan systems, I should mention the merits of link belt. It's a substitute for ordinary V-belts made up of a number of interlocked links. The links and the way they interlock fit right in the
groove profile of a standard sheave.
The advantages for me are principally reduced noise and vibration. They are also more energy-efficient. All these are related. Because the links are
connected non-rigidly, they're free to move and rotate with respect to each other. That means that, unlike a V-belt, it doesn't transmit torque along
the axis of the belt, decoupling oscillation modes on the two ends of the belt system. The links also move with respect to each other when the belt
passes over a sheave. A V-belt will develop internal strain, part of which is dissipated as heat.
A completely practical advantage is that you can adjust the belt length to match the dimensions of your tensioning system, rather than find the right
belt to match your dimensions.
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Magpie
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| Quote: |
The advantages for me are principally reduced noise and vibration
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This is always of interest, even if you don't have close neighbors. I do hear a little "belt slap" with my system.
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EmmisonJ
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here's an update:
so the blower is installed and seems to be running fine, i still need to put in baffles and a sash. when i closed one of the doors to the fumehood i
noticed the suction got much much stronger so that just enforces the fact that i need to put in a sash and then the vacuum will be very satisfactory.
i just generated some smoke to test this out.
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EmmisonJ
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i found a great supplier who is willing to fabricate some steel for my ducting at a great price, the problem is that its galvanized and not stainless
steel.
the fumes that will be pushed through this ducting are all solvent fumes for the most part: dcm, toluene, different alcohols, except there will also
be some hcl. of course my only concern (and major concern) is the hcl, would i be able to coat the galvanized steel with anything (ptfe spray, epoxy
paint, etc) to protect it from any hcl? or is there no question that i just need to find somewhere else and get the stainless steel?
[Edited on 11-5-2009 by EmmisonJ]
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DJF90
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Epoxy is pretty much resistant to most things. Stainless isn't perfect (its only stain-less) so I would probably opt for a coating of epoxy in either
case.
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zed
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Stainless steel usually costs a bundle. Too much! Hastalloy would be dandy....Costs even more. Galvanized is cheap, but reactive. An appropriate
paint, with primer, will generally protect it. But, very few coatings can stand up to massive amounts of either acetone or dcm.......Paint removers!
For really grueling, long term exposure to high concentrations of chemicals, the generally recommended material used to be.........wood! Probably
still is. But, wood has its limitations too.
Nothing is perfect.....Well, maybe teflon, but short of that, there is always some sort of compromise.
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smaerd
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I didn't want to start a new thread for this.
Would a fan like this suffice for 'general' purposes?
http://www.homedepot.com/Building-Materials/h_d1/N-5yc1vZ1xh...
I don't ever plan on making ether or chloroform, and even if so it would be in small amounts and in theory the air would dilute it before it hit the
fan. Would a fan like this pose a serious fire threat for dealing solvents like acetone? I know lexan is a polycarbonate plastic of some kind and
polycarbonate has decent resistance to most common things.
I really would appreciate a nice fan with a belt driven motor but have kind of a 50 dollar budget on this for right now. I just want something to make
sure volatile aldehydes, some light/acid/base exposure don't end up in my lungs or on basement plumbing, and rather outside.
Thanks for any help.
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grndpndr
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That looked like some nice sheetmetal fabrication magpie.Im assuming you had no sheet metal brakes etc. Nice work.
Ive also been wondering why occaisonal use with acids would nescessarily trash a squirrel cage fan motor if it were direct drive given the small hole
for the impeller.I wonder if there wasnt some way to dissasemble the squirrel cage to install a kind of rubber/etc washer over the motors shaft to
help prevent any incursion of gases particularly if as you say a vacum would be created away from the area of the motor shaft.Still i would be very
hesitant with flammable gases.Lacking flammable gasses in the hood, sciplus often has an nice selection of squirrel cage blowers at a replaceable
price.
@smaerd,looks nice easy to install but awfully exposed.I dont have much experience with attempting to keep moving parts moving in a acidic envoroment
but I was very suprised how little actual acidic fumes it took to gum up the works on a rel. HD drill chuck I was forced to use with a stirrer even
though the chuck itself had a very vigorous air flow keeping acid fumes away from the drill or so I thought. The tough mech. chuck required serious
lubrication and work to get it functional again despite the fact I saw No fumes. Im actually suprised the drill motor itself wasnt trashed from 2
minutes of stirring.
[Edited on 13-1-2011 by grndpndr]
[Edited on 13-1-2011 by grndpndr]
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peach
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It's interesting, to me, to note that a number of inline, direct drive, hydroponics fans are now external rotor, induction motors.
What that means is, the coils carrying the electricity from the mains are stationary and sat behind the fan blades - they don't move or make any
connections inside the fan.
The motor spins because there are some coils inside the the rotor head sat over those mains powered coils - being magnetised and moved by the one that
sits still, via induction.
For an even more simple explanation, there are NO brushes involved in the design. And it is the brushes that create the showers of sparks from other
motors (look into the cooling holes on a desktop fan, a hand drill or another similar tool at night with the lights off, and you will likely see blue
flashes from the contacts).
An indirect drive would be great, but the lack of these contacts would make the fans considerably safer than the others for things like fume hoods.
You can take some of these fans to bits to get access to the rotor and motor as well, allowing you to paint the insides with something like epoxy. Be
sure to check the fan over yourself if doing this, as stoner's tend not to be all that interested in how it works, only that it does.
I also see a complete lack of interest in scrubbers in all of these fume hood threads. If you blow a highly flammable mixture out the side of the
house, something out there could also ignite that, or if it's toxic, it could be blowing in some kids face - I believe government funded labs (like
universities) tend to duct the exhaust up to the roof to keep it away from the pockets of undisturbed air, and people, near ground level.
That aside, placing a scrubber of some form before the fan would help prevent the corrosive materials getting to the fan in the first place.
Dealing with acids, flammable and toxic things, you should always make an attempt to neutralise, minimise or entirely avoid the thing getting airborne
to start with; ideally.
This is not a guide, argument starter or recommendation, it's some ideas.
[Edited on 13-1-2011 by peach]
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grndpndr
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In a perfect world you bethca it would solve alotta problems
not to mention immediate safety but long term safety via less toxins in the air.Naturally no worries about the fan/explosions-corrosion, use of
specialized materials-processes.
Problem being how to accomplish?Activated Charcoal filter?water bath sorta arrangement? I have no clue what the cost would be for a filter capable of
handling the variety of nastys in the volume w/o inhibiting air flow and killing the operator
in the process.maybe a very large air/water bubbler?No Im not trying to be funny, purposely stupid just imagining the difficultys.Realistically though
not that any amount of pollutions acceptable Id Imagine what every hobbyist generates in the way of pollutants is miniscule in comparison with almost
any large plateshop,paint booth, small coal fired
electrical plant. Or even wood stoves from Gillette WYO on a cold day.
Really not making light of the situation it would save a fortune in components for the hobbyist if it could be made practical.
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peach
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In terms of the environment (having hugged a tree myself) at home chemistry is not an issue.
But it would be nice if it helps with it, the safety and protects your fan.
For example, chlorine can be absorbed onto activated carbon - there is a long list of others a.Carbon actually and it is ubiquitously found around gas
filters (half a kilo of air float activated carbon costs a few pounds).
Using a bubbler won't work due to the massive pressure difference required to blow bubbles through it whilst maintaining that volume of flow.
Respirators use scrubbers, and there are not that many different cartridges to deal with a wide spread of gases - it's usually along the lines of,
organics (solvents), acid gases, base gases, ammonia, halogens. Googling for cartridge composition will likely yield what is being used for each
stage, and it's likely the same thing for all the manufacturers (as this is an industry where standards MUST be maintained).
Again, by far the best option is to avoid it getting into the air in the first place.
As I just replied to magpie, chlorine, for example, can be scrubbed out of the exhaust of the glass by bubbling it through 10% NaOH - which avoids it
getting airborne in the first place. The same applies for many other gases. The more reactive, the better it works.
This is how industrial chemists deal with it when they have tanker truck quantities of harmful things trying to escape. They can't use fume hoods,
have all their staff in HazMat suits in board meetings or simply blow it out the chimneys, it needs to be dealt with as it tries to leave the sealed
process - the respirators go on if something goes wrong.
[Edited on 13-1-2011 by peach]
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smaerd
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@grndpndr - thanks for saving me the trouble. I'll look for a more 'real' fan. Yea I liked it because I am not so good with electronics and it seemed
a simple set up. Though yea your right, it'd only take a little HCL before that thing met it's fate even if it was epoxy coated.
Hmm I have a couple pounds of activated carbon for fishes(cheaply acquired).
I was actually intending to make a thread about scrubbers. I can't seem to think of a way to effectively build one. The only thing I could find was
some pot growers lining little mesh garbage cans/pencil holders with panty-hose and stuffing them with activated carbon. Obviously this is not
suitable due to the chemical resistance of panty-hose lol.
Looks like they sell them pre-made upon simple googling.
http://www.google.com/products/catalog?hl=en&q=ducting+f...
How effective these kitchen ones would be for HCL though seems like an entirely different story. It could prolong a bad fan though.
edit - I'm still having a hard-time finding an affordable fan. Induction fans running 2,000? belt driven fans $400(used)?
edit again - squrrel cage fans look affordable, but does brushless mean sparkless?
Would something like this not be ideal?
http://www.horticulturesource.com/hydrofarm-active-air-blowe...
I can't tell but it looks like the motor is directly connected to the fan. Maybe leading to sparky sparky? It appears to be metal and of a decent
quality. I doubt there would be much exposure of fumes to the motor? Blade replacement doesn't look expensive or hard.
[Edited on 13-1-2011 by smaerd]
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peach
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Brushless SHOULD mean sparkless yes. As there are no electrical contacts involved, just coils of wire and magnetic fields.
The US guys seem to have tons of squirrel cage fans lying around, but they're not so abundant in the junk of the UK. I'm not sure how many of them are
inductive and so on, but I think quite a few of them are brushed.
The cannabis farm fans use inductive, brushless motors a lot, and they're way cheaper than $2k, they're more like $50-100 and will do thousands of
CFM.
The easiest method I came up with for adding a scrubber would be to buy a sewer pipe fitting called an 'access bend' or 'access joint'. These are
lengths of pipe with a big port on the side that screws open and shut - it's big enough to get a hand in and they're used to provide inspection and
jetting points. There's a picture of one at the end.
You could easily cap off a section of this with mesh on each end and then fill the inside with your media. You can also get it back out easily enough
with a hoover. The fittings feature air tight seals and are supported by a range of couplings to fit them onto other pipes of more random size (e.g.
the inlet on a blower).
You need to be careful with the word HCl, as hydrochloric acid (HCl[aq]) and hydrogen chloride (HCl([g]) are significantly different in terms of their
ability to corrode things. Hydrogen chloride will corrode stainless steel and attack chrome. The only truly resistant materials against that level of
attack are Monel and PTFE (or one of it's sisters). You won't find or be able to afford either of those. So it's a question of making the best of the
rest. For example, these fittings are big enough to paint the inside.
You can also scrub gases by having a section of duct with water jets in it - e.g. those little garden misters you can get for automatically watering
the garden would seem like a possibility. Something like hydrogen chloride has a huge solubility in water. You then need to consider that mist getting
into the motor if it's happening upstream of it and it's inline.
A good tool for considering these things is Cole Parmers chemical resistance guide. Which rates epoxy A - Excellent for hydrochloric at 20 and 37%, as
well as the dry gas.
[Edited on 14-1-2011 by peach]
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smaerd
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Thanks a bunch as always peach. Your always willing to help spell things out and share worthy ideas. Misting is a great idea, I never even thought of
that.
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Regolith
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I hate to Necro this thread but a cheap junk source of direct drive squirrel cage fans are readily available.
The type of large microwave that mounts above a stove. The ventilation fans are quite powerful. They are meant to be the vent fans for the stove they
are above, as such the motor is somewhat out of the air stream and its not too difficult to seal the motor away from fumes. All the models I've come
across are double sided there is no reason you can't take one of the cages off (slight extra bearing load tho) to give the extra power to the other or
dual your air stream and/or have dual intakes for wider larger vent hoods.
The motor is a synchronous AC that has no brushes. It can be easily controlled with a simple scr based fan controller available at almost all hardware
stores, next to the light dimmers, don't use a regular dimmer on a motor of this type you will cause overheating and blow the motor, that is IF you
don't want the thing at full blast all the time, they can be quite loud! Many of the models have plastic fan blades (some are metal pick your
preference). Simply looking inside the bottom will show you the fans blades. here are pictures of a unit that is awaiting installation as the blower
for my oil fuelled metalworking furnace and a plastic version I just froze my ass off and tore out of a scrap micro in the garage, for pictures sake.
Both of these had a HEAFTY price tag of me being cold and patient to get (cold based on season) and a giant 0 dollars and 0 cents. When, or if(depends
on how well you seal it) they die replacements are as above not hard to get. The white between the 2 fans is a pack of coffee filters shows for a
sense of scale.
 
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sdodgen62
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why not build a hood on the same principle as an asperator works? nothing in the stream, im pondering how to build one myself and this is what im
thinking
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sdodgen62
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i'll post pics when complete
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sdodgen62
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being a carpenter by trade in thinking of using a tempered glass window unit for the sash, which is somewhat how most hood are made. pls post with
input
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Magpie
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| Quote: Originally posted by sdodgen62 | | why not build a hood on the same principle as an asperator works? nothing in the stream, im pondering how to build one myself and this is what im
thinking |
I hope you have better luck than I:
http://www.sciencemadness.org/talk/viewthread.php?tid=3625#p...
Building contractors sometimes use air jet ejectors to move a lot of air at a job site. They commonly use air at about 100 psi, and I believe they
are noisy as hell.
They are commonly known as Coppus blowers, but there are other manufacturers as well. I had quite a time finding them as I wasn't using the right
keyword, which is venturi. To find them use "venturi air blower." Here's an example:
http://www.airblast.com/Airblast%20Venturi%20Air%20Blowers.p...
[Edited on 13-1-2012 by Magpie]
[Edited on 13-1-2012 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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sdodgen62
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yeah i see magpie,
but im thinkin more 600cfm 20" attic fan as my jet of air, i see no reason it shouldn't draw more air than i want but i guess i ccould be wrong i
have been before lmao
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