Ye Olde Forge

[Screwdriver]

oops wrong thread...

 

[Screwdriver]

So now that I have a working forge, I need a working air extraction system to maintain my working lungs.

I have a couple of sheets of galvanised 1.2mm

72" x 24" and 72" x 12". Gotta make something outta that. Went through a number of iterations including some flared designs but they were all way too complex. Simple is best.

The above uses the entire "full" sheet with 1" return, one for a "safe" edge, one for mounting holes. Then a 2" offset into a 30˚ slope front. This gives me 11" drop so I can use the 12" sheet with a 1" return and a couple of tabs for joining.

Sketchup makes a great job of optimising the design to suit found materials and then dimensioning for cuts and bends.

I know right: it looks so trivially simple and obvious now! Trust me, getting a good looking shape that I could make from those bits was a real chore.

Gabro makes a quick and easy job of it...

Some of the inside corners were a bit tricky until I remembered I have a bandsaw! LOL. Makes a right racket cutting those thin sheets though.

Got them set up on the flypress though I could probably bend them just as easily with a couple of bits of angle iron. I like using the flypress!

Then I remember just in time I probably want to knock out some holes for rivets or plug welding. Then like Buridan's ass, I start dithering about using the spot welder - perfect for the job but the arms don't reach. So I'm going to have a quick looksee if I can find, make or somehow acquire some suitable arms.

 

[Screwdriver]

The main event is this bad boy.

Six foot long, four bends.

Doesn't sound too bad until you have to manoeuvre it around a cramped workshop to get at both ends.

And after all that, it still looks flat!

One 30˚ bend and one 60˚

The marks line up ok

Bent (much more sensible job for the flypress).

The bends are so strong it was hardly worth welding but I put the MIG in there so...

All done.

Just need to lift it above my head and hold it level while I bang in a couple of screws.

Should have been a video, sorry chaps but I got it up and installed.

It looks exactly how I wanted it to look. Very happy. Need to drill out some vent holes for minor extraction duties. It's not a chimney per se, just want to waft away any nasties from the propane forge. Might help keep the place cool too but I was burning off the paint from some chopped up car springs and thats not healthy even with the doors open.

 

[Dieselman 63]

The main event is this bad boy.

Six foot long, four bends.

Doesn't sound too bad until you have to manoeuvre it around a cramped workshop to get at both ends.

And after all that, it still looks flat!

One 30˚ bend and one 60˚

The marks line up ok

Bent (much more sensible job for the flypress).

The bends are so strong it was hardly worth welding but I put the MIG in there so...

All done.

Just need to lift it above my head and hold it level while I bang in a couple of screws.

Should have been a video, sorry chaps but I got it up and installed.

It looks exactly how I wanted it to look. Very happy. Need to drill out some vent holes for minor extraction duties. It's not a chimney per se, just want to waft away any nasties from the propane forge. Might help keep the place cool too but I was burning off the paint from some chopped up car springs and thats not healthy even with the doors open.

Fume hoods are worthwhile investments! Even for things like bodyfiller which tots your lungs. I’ve got a tin at home made in Poland, one of the (many) warnings on it is to keep it away from pregnant women!

 

[Screwdriver]

Fume hoods are worthwhile investments! Even for things like bodyfiller which tots your lungs. I’ve got a tin at home made in Poland, one of the (many) warnings on it is to keep it away from pregnant women!

I made a "fume hood" without even knowing it! How about that

 

[Dieselman 63]

I made a "fume hood" without even knowing it! How about that

Better change your middle name to ‘celebrity-artiste’

 

[Screwdriver]

The hood has to go on and off a few times while I sort out the vents so I made some better clips. I seem to remember literally finding this in the road a few years back. Great little tool it is too.

Never thought I'd really need to build a tower of adaptors for the Bosch but in such a cramped space, it also came in dead handy. Easier to move the bracket than take that blasted heavy thing off the wall.

The cutouts are right up against the fence.

Plan is to fit a panel with 8 off four inch drainpipe vents. They should help with water/vermin ingress and I might even fit a small extractor inside the pipes.

Only needs to waft really, not a full extraction system per se. As per my "wanted" advert, I might be better off blowing fresh air into the shed from the other end.

Fired up the forge to see if it made a difference.

By burning off some paint while straightening out a truck spring. damn but that steel is TOUGH!

No idea what I am going to make out of it. Possibly something for the garage owner where I nicked it from. For me, I'm thinking maybe some punches or cold cut chisels. They also make very good knives.

 

[gaz1]

heat rises so stick a chimney on it and allow the chimney stack to pull air up also use the method of anti down draft on chimney

you will regret a back draft

 

[Screwdriver]

Chimney is out of the question, it has to vent sideways and it's not a coal forge (yet).

Why will I regret a back draft?

 

[MattF]

Because it blows everything inwards.

 

[Screwdriver]

Because it blows everything inwards.

I am not fitting a chimney though a bitumen panel roof. End of story. This space is a lean to made from builders bandstands, a bit of fence panel and an Onduline roof. It is a quick cheap (actually almost free) bodge so I have somewhere to put the anvil and run a forge without burning down the shed.

It gets a fume hood and some vents for now. That's why I am considering a blower on the opposite side of the space. It should pressurise the room with fresh air and encourage a draft to flow out of the vents under the hood.
If all else fails I can throw the doors open. If I was going to run a coal forge, I'd brick out the entire rear section and replace the roof before I would even think about having a chimney. Over the years I might brick it out anyway...

 

[Parm]

The last thing you want to do is pressurise your workplace. Normall industrial convention is to have your room under a slight negative pressure so the extracted air goes where you want. As others have pointed out fitting a chimney is the best way forward. Any heat and emission from your furnace will be thermally buoyant and will want to rise. With a correctly fitted chimney. The buoyant air will be entrained into your capture hood and removed away from the work area. If done correctly you won’t need to spend any money on electricity to run a fan. This is a tried and tested method of providing local exhaust ventilation

 

[Screwdriver]

The last thing you want to do is pressurise your workplace. Normall industrial convention is to have your room under a slight negative pressure so the extracted air goes where you want. As others have pointed out fitting a chimney is the best way forward. Any heat and emission from your furnace will be thermally buoyant and will want to rise. With a correctly fitted chimney. The buoyant air will be entrained into your capture hood and removed away from the work area. If done correctly you won’t need to spend any money on electricity to run a fan. This is a tried and tested method of providing local exhaust ventilation

I appreciate that and I could fit a system which sucks air out into the makeshift fume hood but all I need right now is a reasonable waft of fresh air as and when required. I can always throw the double doors open. Unlike an industrial environment, there's no one working in there all day so as long as there is some ventilation, I'm happy to wait in the event of excess smoke/chemical fumes.

I can rig up a (makeshift) vent duct from some 110mm soil pipe I nabbed off a neighbour. My theory is that gas in an enclosed space is a bit "stringy". Pull lightly on one end and if there's not too much drag, the rest should follow. Since the fumes I am interested in removing are hot, they should already be happy to hang around the ceiling and dive up the hood skirt. I reckon they just need a teensy bit of encouragement.

 

[Parm]

I appreciate that and I could fit a system which sucks air out into the makeshift fume hood but all I need right now is a reasonable waft of fresh air as and when required. I can always throw the double doors open. Unlike an industrial environment, there's no one working in there all day so as long as there is some ventilation, I'm happy to wait in the event of excess smoke/chemical fumes.

I can rig up a (makeshift) vent duct from some 110mm soil pipe I nabbed off a neighbour. My theory is that gas in an enclosed space is a bit "stringy". Pull lightly on one end and if there's not too much drag, the rest should follow. Since the fumes I am interested in removing are hot, they should already be happy to hang around the ceiling and dive up the hood skirt. I reckon they just need a teensy bit of encouragement.

Have an experiment and see how you get on, but if I’m correct in understanding what you de# rice sounds like the beginnings of a push pull ventilation system. These are one of the most complex types of system to set up. Always get lots of problems with eddy currents disrupting airflow. One possible solution is to install ventilation grills in your door. With doors closed it should create air movement in the right direction, ie up and into your hood

 

[Screwdriver]

Have an experiment and see how you get on, but if I’m correct in understanding what you de# rice sounds like the beginnings of a push pull ventilation system. These are one of the most complex types of system to set up. Always get lots of problems with eddy currents disrupting airflow. One possible solution is to install ventilation grills in your door. With doors closed it should create air movement in the right direction, ie up and into your hood

It is an experiment and I am not suggesting for a minute that it's a valid solution. It is a very odd shaped room though - like a funnel! There's a narrow section at the back which opens out to the brick desk an chimney breast you see in most of the pics. So if I go for forced ventilation, I will put a vent into the rear wall, blowing fresh air into the space towards the "funnel" opening and the fume hood.

Not sure yet if higher/lower or dead centre will be best for whatever circulation that may develop. I'll probably start with cold air being blown in at head height.

 

[Screwdriver]

Here's a top view of the outline. Hood is at the top, "rear wall" at the bottom. Double door top right.

Not only does the shape look like a funnel, the roof has a pronounced "fall" so inside the space, the roof gets higher towards the hood too. Win/win I think for ducting...

 

[gaz1]

put it this way i suspect it will fail

rooms are always negative not positive

for start off too many holes 2 holes is enough as others wont get air from it will just pull from the first

if your intent is still to use use a side blower only then use it to pull air out of the room by using a venturi

easiest method put an 1" square tube inside a 2" tube or round tube the air being blown past the 1" will suck air out of the room

the fan is your problem i suspect its a side ways blow out with it if it is all you need to do is put fins on it to make it directional

 

[captain-destructo]

all them holes in the wall next you will be complaining its too cold to work in there in the winter

 

[slim_boy_fat]

all them holes in the wall next you will be complaining its too cold to work in there in the winter

Not with the forge going.

 

[Screwdriver]

put it this way i suspect it will fail

rooms are always negative not positive

for start off too many holes 2 holes is enough as others wont get air from it will just pull from the first

if your intent is still to use use a side blower only then use it to pull air out of the room by using a venturi

easiest method put an 1" square tube inside a 2" tube or round tube the air being blown past the 1" will suck air out of the room

the fan is your problem i suspect its a side ways blow out with it if it is all you need to do is put fins on it to make it directional

The tone of this message is somewhat aggressive and dismissive of my plan. I am not sure if that is deliberate.

Do you have any experience in room ventilation or are you just reiterating something Parm said? This lean-to shed is not hermetically sealed, I see no problem with having a fresh air inlet. I am not entirely sure "rooms are always negative pressure" is true either. You wouldn't want to do that in an aircraft for example, or a clean room, or a biological facility etc.

There are exactly as many holes as required thank you. Not too many. Too many for what anyway? "The others wont get air" suggests you havent read my post. Thats a simple vent, not a flue, not a chimney and they won't have a fan attached at this stage though I might fit eight fans one for each If plan A doesnt work.

A venturi would be uneccesarily noisy. I am planning for large volume low speed air flow, hence my constant reference to "wafting" air out of the space. My only slight concern is superhot fumes from the forge possibly containing combustion byproducts from contaminated metal. That should go straight up to the hood anyway, encouraged by having a fan blowing from the other end of the room and otherwise it goes out the double doors.

You keep going on about "side blowers" and "<my> problem is a side blow" but I have never even mentioned having one or planning on having one. I don't know where you get that from.

On the other hand it occurs to me that having an outlet vent at one end of a funnel (where all the heat is) and a cold air inlet at the other end is the ideal scenario for expelling heated noxious fumes. I might not even need a fan at all.

There are four square cut outs so that I can happily start burning off paint in the forge. They can easily be shut off with a simple flap or flaps, maybe a sliding gate if I feel like it. It might get soil pipe ducting because I happen to have a few lengths of soil pipe. If I had a ton of spiral wrap ventilation, I'd use that. The holes are positioned and spaced such that I can fit whatever type of outlet happens to be flavour of the month on a removable panel.

Anyhow, this is all supposed to be a bit of fun and (as I said above) an experiment. Part of the challenge is not merely making it work but making it from found materials, recycling scrap and learning how things work along the way.