Author Topic: Building a Fume Hood  (Read 16311 times)

Offline S. Heslop

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Building a Fume Hood
« on: September 06, 2016, 04:30:04 PM »
I think I mentioned this elsewhere, but i've been planning for a while to make some videos about chemistry. I'm going to start it all off with a fume hood, since that's what I can build with my current tools.

The plan so far. It's going to be on wheels so I can push it about.


A couple days ago I cut up two big boards of plywood into the various panels that will make up the thing. It's a task I was dreading but was glad to get out of the way.


Wood is perhaps not the ideal material for something like this, but it's relatively cheap and easy to work with. I am planning to make a sort of steel tray for the inside at least, to somewhat prevent fires damaging the wood.



Today I got some time to nail the bottom half together. I'm going to attach the wheels to it before I start assembling the upper half. I've also been trying out some of that polyurethane construction adhesive and it really gets everywhere.



Offline tom osselton

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Re: Building a Fume Hood
« Reply #1 on: September 06, 2016, 05:31:04 PM »
You could have used a old cabinet or Ikea it probably would have been cheaper.

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #2 on: September 07, 2016, 08:46:45 AM »
You could have used a old cabinet or Ikea it probably would have been cheaper.

Perhaps, but I like having more control over the dimensions than trying to fit it around an existing cabinet. Not sure if it would've been cheaper either. And i'd need this to be stronger than Ikea's chipboard and cam fastener construction.

Offline tom osselton

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Re: Building a Fume Hood
« Reply #3 on: September 07, 2016, 02:30:45 PM »
True I was just wondering it seems a lot of things are produced way cheaper than the cost of materials.
I've never liked chipboard!

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #4 on: September 10, 2016, 11:23:05 AM »
Got some more done. Bit of a delay since I got caught up helping prepare for a funeral.


Put the wheels on a couple days ago.


For the windows on the side of the thing I routed them. It's not easy to see in any of the pictures, but I routed a ledge on as well for the glass to fit in. For the second window I realised it's better to route the ledge first before going all the way through. Also I didn't have material to make a proper template, so I ended up making a single corner piece and moved it around as I reached each corner.


Getting the top half on was a real fiddle. I started by nailing and gluing the top to the sides on the floor, and then lifted that up onto the base. Then glued and nailed the back on to get it all square and rigid. I feel like theres probably a smarter way to assemble stuff like this but it's beyond me.

Take note of my dumb jacket.


The next step will be front bits.


So as for the jacket. I've gotten the silly idea of trying to make my 'show' more interesting (for the viewer and myself!) by giving it a scifi theme, in the form of 'skits' at the midway point and how any diagrams I draw look. Honestly I just want a chance to make props and effects, but I think it could help offset how dry the topics might be otherwise.

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #5 on: September 11, 2016, 02:39:16 PM »
Got the sides done.



I didn't think till afterwards to check if they were square, and theyre a fair bit off. They should be relatively straight and parallel though since I did put some effort into that.

RobWilson

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Re: Building a Fume Hood
« Reply #6 on: September 11, 2016, 02:54:24 PM »
Looking good  :thumbup: do you have an extraction  fan sorted?

If not I have one these going spare if you want it .



240v , quiet ish  and moves a fair old bit of air  :dremel:


Rob

Offline awemawson

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Re: Building a Fume Hood
« Reply #7 on: September 11, 2016, 03:20:00 PM »
That'll suck the side walls in like the cheeks of a toothless old man  :lol:
Andrew Mawson
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Offline S. Heslop

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Re: Building a Fume Hood
« Reply #8 on: September 11, 2016, 03:29:14 PM »
Yeah I would, thanks! I was planning to pilfer the bouncy castle blower from my dust extractor, but the thing is so tall it wouldn't fit under doorways.

I've got a car now so I could come collect it whenevers convenient for you.

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #9 on: September 11, 2016, 03:34:00 PM »
That'll suck the side walls in like the cheeks of a toothless old man  :lol:

Oh yeah that's a point. I've forgotten everything I once knew about motors, but is there any cheap way to control their speed? Alternately I could put a baffle in the way of the airflow to slow it down but the motor might rely on Full Blast to keep cool.

Wish I didn't chuck that box fan out, so I could take a look at how that controlled its speed.

RobWilson

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Re: Building a Fume Hood
« Reply #10 on: September 11, 2016, 03:36:33 PM »
Nice one .Congrats on passing your test   :thumbup:

On holiday at the moment . Back in 11 days .will PM you when back  :thumbup:

Rob

RobWilson

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Re: Building a Fume Hood
« Reply #11 on: September 11, 2016, 03:38:10 PM »
Plenty of cheep AC motor controllers on eBay


Rob

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #12 on: September 11, 2016, 03:48:52 PM »
Nice one .Congrats on passing your test   :thumbup:

On holiday at the moment . Back in 11 days .will PM you when back  :thumbup:

Rob

Thanks very much!

Offline raynerd

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Re: Building a Fume Hood
« Reply #13 on: September 11, 2016, 05:25:51 PM »
I teach chemistry and we got rid of about 6 of these a few years back, they were scrapped  :Doh:

What chemistry vids you looking at doing or what are your plans for the hood?

Offline Will_D

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Re: Building a Fume Hood
« Reply #14 on: September 11, 2016, 05:43:48 PM »
I have a degree in th e dark arts -well ok, organic chemistry - following this thread with interest!
Engineer and Chemist to the NHC.ie
http://www.nationalhomebrewclub.ie/forum/

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #15 on: September 11, 2016, 08:07:08 PM »
I teach chemistry and we got rid of about 6 of these a few years back, they were scrapped  :Doh:

What chemistry vids you looking at doing or what are your plans for the hood?

I feel like there's a gap on the internet between 'fun' chemistry videos, like what Nottingham University produces with their Periodic Video series, and then very dry recorded lectures and people showing organic syntheses. By that I mean there's no real videos that teach chemistry to about A level and beyond that are also somewhat entertaining to people with a passing interest in chemistry. On top of that it's been bothering me that I'm slowly forgetting all the stuff I learned in university, for lack of using it, and it's also been my dream to try make analytical devices like an FT-IR spectrometer. So i'm really trying to combine the two (plus the sillier desire to build props and effects) into a single video, which I believe could turn out fairly decent if I do it right. Although for this video i'm sort of probing the idea by clumsily building a fume hood and covering the 'basics' of chemistry; mostly the stuff I think is most useful, aimed at people who probably don't know a whole lot about chemistry.

I'm still working out exactly what basics I want to cover since there's alot of stuff I could leave for later videos, and it's tricky to know what the audience already knows. I think they call it the 'curse of knowledge'. George Bernard Shaw was wrong; being able to teach is a real admirable skill.


As for the hood itself, I think it's going to be mostly for show. The reactions I plan to do will be for the sake of demonstrating principles, and hopefully stay clear of anything particularly dangerous.

I met a guy a few months ago who was talking about melting beer cans in his back yard after seeing one of the many youtube videos about exactly that, but he didn't seem to know anything about the dangers involved. I advised him against it, but it got me concerned over how irresponsible those videos tend to be. They're often presented in a way that suggests it's a safe thing anyone could try, with the presenter wearing shorts and trainers and acting generally careless. But if the presenter strolled out in a full kiln suit then most viewers would probably get the vibe that it's a dangerous thing to do (or that they want to show off their cool ppe). So in the same line of thought, I think a fume hood would work in a similar way. Nobody pays attention to disclaimers and warnings, but if they see me taking all the precautions I can then they'll hopefully get the idea that it's not something to be taken lightly.

plus I don't want to gas myself

Offline micktoon

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Re: Building a Fume Hood
« Reply #16 on: September 12, 2016, 04:22:18 AM »
Sounds like an interesting project Simon, the videos and the hood. I think you are right about the casual way many things are done on Youtube by some people, some are wreckless and they have just been lucky not to been hurt. I think having the hood will give viewers the right impression that thought over safety is needed. AvE on Youtube has done some videos with sort of chemistry type experiments and they have been very popular from what I remember.
   Good luck with the videos anyway Simon  :thumbup:
 Cheers Mick

Offline DMIOM

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Re: Building a Fume Hood
« Reply #17 on: September 12, 2016, 06:46:17 AM »
That'll suck the side walls in like the cheeks of a toothless old man  :lol:

Oh yeah that's a point. I've forgotten everything I once knew about motors, but is there any cheap way to control their speed? Alternately I could put a baffle in the way of the airflow to slow it down but the motor might rely on Full Blast to keep cool.

Wish I didn't chuck that box fan out, so I could take a look at how that controlled its speed.

Alternatively, leave the fan running at full speed and arrange a simple (wooden?) valve to allow you to admit a controlled amount of air direct from atmosphere - pic below of similar arrangement on my old vacuum cleaner where sliding sleeve covers/uncovers port to allow bleed air in and reduce suction.

Dave

Offline PekkaNF

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Re: Building a Fume Hood
« Reply #18 on: September 12, 2016, 07:52:35 AM »
I have yo agree with Mick. Most of the stuff on YT is executed with reckless abandon and lack of skill is replaced with bravado.

Anyways, I would not be too worried about too much suction. For any kind of decent draught you need whole lot of flow. You probably will be blowing the exhaust up on the roof (no point of expelling it inside), ducting will take cause some loss on efficiency.

You probably need some curtain or something on the opening to restrict the opening size ot there probably will be not enough of flow to suck all obnoxous stuff out. Also a little glass barrier on the front might be a good idea, some airborne material has tendency to descend. But you probably allready know all of this.

http://www.cibsejournal.com/wp-content/themes/cibsejournal/images/2013-10/images/fig-1.png

Pekka

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #19 on: September 12, 2016, 11:22:04 AM »
That'll suck the side walls in like the cheeks of a toothless old man  :lol:

Oh yeah that's a point. I've forgotten everything I once knew about motors, but is there any cheap way to control their speed? Alternately I could put a baffle in the way of the airflow to slow it down but the motor might rely on Full Blast to keep cool.

Wish I didn't chuck that box fan out, so I could take a look at how that controlled its speed.

Alternatively, leave the fan running at full speed and arrange a simple (wooden?) valve to allow you to admit a controlled amount of air direct from atmosphere - pic below of similar arrangement on my old vacuum cleaner where sliding sleeve covers/uncovers port to allow bleed air in and reduce suction.

Dave

That could work. While the big blower would probably be flat against the top, there will be a baffle inside to try distribute the airflow more evenly. I could stick holes in the side or rear of the cabinet where that baffle is with adjustable covers to adjust the airflow.

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #20 on: September 12, 2016, 12:03:39 PM »
I have yo agree with Mick. Most of the stuff on YT is executed with reckless abandon and lack of skill is replaced with bravado.

Anyways, I would not be too worried about too much suction. For any kind of decent draught you need whole lot of flow. You probably will be blowing the exhaust up on the roof (no point of expelling it inside), ducting will take cause some loss on efficiency.

You probably need some curtain or something on the opening to restrict the opening size ot there probably will be not enough of flow to suck all obnoxous stuff out. Also a little glass barrier on the front might be a good idea, some airborne material has tendency to descend. But you probably allready know all of this.

http://www.cibsejournal.com/wp-content/themes/cibsejournal/images/2013-10/images/fig-1.png

Pekka

I've got plans for an adjustable sash. I just bought the glass today, in fact. It's not tempered so theres a potential hazard there. But it's extremely heavy at 6mm thick. I kinda forgot how heavy glass can be. The plan for counter weights was to hide them inside the sides of the cabinet but there's nowhwere near enough space to actually balance the glass. Plus the whole thing would become quite front heavy even if I could. There's also not enough travel for a pulley system.

I've built the cabinet around an imaginary garage layout, containing a larger lathe and a bridgeport mill that don't exist, so i'm hesitant to extend the cabinet forwards any further. I could maybe dangle weights off the side but that would look silly. Or I could fit weights into the space below with a really elaborate pulley system to reach them. Or maybe I could fit some long springs inside the arms and a system to lock then sash at any position. I guess theres alot of things I could do.

Offline raynerd

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Re: Building a Fume Hood
« Reply #21 on: September 12, 2016, 03:59:58 PM »
You just going to extract or filter as well? I know ours go through a simple carbon filter first.

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #22 on: September 12, 2016, 07:11:10 PM »
I've been thinking about maybe making it go through a tank i'd mostly keep empty, but can be filled with water to bubble though. But I bet that'd cause a big mess. And with the glass and counterweights i'm starting to get concerned about how top heavy the thing is. I'm planning to put some cupboards up along the wall next to the fume hood so maybe I could stick something there and just duct it in.

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #23 on: September 13, 2016, 02:46:02 PM »
Today I learned that it's impossible to cut the corners off of glass using the score method. I wrecked one of the side windows trying to do exactly that, and kept trying on the ever smaller pieces remaining. The glass just wants to skip to the edge as soon as it becomes more favourable for it to go that way than following the score, which I should've realised sooner.

I might try getting some diamond wheels for my rotary tool. It's got one of those wands so that'd help keep the coolant water away from any mains electrics.

Offline S. Heslop

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Re: Building a Fume Hood
« Reply #24 on: September 16, 2016, 07:44:05 AM »
Dang garage flooded again so there's not alot I can do while waiting for it to dry. Glad I woke up in the middle of the night just before it started raining to get all the important stuff off the floor.