How big do bellows have to be?

[rdennett]

How big should a bellows be in terms of volume of the chamber(s)? I am specifically wondering if a 5 gallon bucket is large enough to make a Japanese style bellows out of.

Thanks,
Rob

[ThomasPowers]

How big a forge are you trying to make; what do you want to do with it? 5 gallon bucket is way too large or way too small or just right depending on that information.

BTW most of the buckets are tapered and you want straight sides for a piston bellows set up. Look for large PVC pipe.

[rdennett]

How big a forge are you trying to make; what do you want to do with it? 5 gallon bucket is way too large or way too small or just right depending on that information.

BTW most of the buckets are tapered and you want straight sides for a piston bellows set up. Look for large PVC pipe.

Fortunately, the taper isn't so severe that a flexible gasket can't take up the slack. I am not quite sure what info you need, but my forge is a small charcoal forge that I would like to be able to get to welding heat without breaking my arm.

Thanks,
Rob

[ThomasPowers]

Rob; since you say it's small I guess that it's about the size of a coffee can and a bucket sized bellows will be plenty. You must remember that we have a wide range of folks here. A friend here works where 6" diameter stock is small and 40" diameter stock not unknown (and the tongs have wheels and engines and you get to ride them!). Another does miniatures and considers a bean can forge to be a "large one".

Note that the flexible gasket puts force on the sides when it gets to the small end and most folks making such bellows are trying to reduce all drag as much as possible rather than add some in.

I was bellows thrall at Quad-State when Ric did his "3 ways to make steel" demo and used his home built rectangular box bellows. It was very nice but I found I still preferred the european double lunged bellows myself

[rdennett]

Rob; since you say it's small I guess that it's about the size of a coffee can and a bucket sized bellows will be plenty. You must remember that we have a wide range of folks here. A friend here works where 6" diameter stock is small and 40" diameter stock not unknown (and the tongs have wheels and engines and you get to ride them!). Another does miniatures and considers a bean can forge to be a "large one".

Note that the flexible gasket puts force on the sides when it gets to the small end and most folks making such bellows are trying to reduce all drag as much as possible rather than add some in.

I was bellows thrall at Quad-State when Ric did his "3 ways to make steel" demo and used his home built rectangular box bellows. It was very nice but I found I still preferred the european double lunged bellows myself

Thanks for your help. I don't really see myself working steel much larger than about 1" in diameter. I actually did make a box bellows, but the piston kept getting stuck due to the inaccuracy of the tools I used to fashion it and the flexibility of the plywood it was made from. Also, I think the valve holes may have been too small to move the amount of air I wanted. I then made a set of double lung bellows, but I think the plumbing was too narrow and the firepot too deep. I have modified that, but I have not done any forging since. In any case, I know where I can score some empty pickle buckets with lids that will work, so maybe I will just experiment. I have also been thinking of a way to make centrifugal fan out of a bucket, so I may have a go at that as well.

Thanks,
Rob

[jeremy k]

Rob if you are having issues with a gasket - take a look at this simple design that most anyone could make with scrounged mat'ls..... http://www.forging-ahead.co.uk/blacksmiths_water_bellows.htm - JK

[rdennett]

Rob if you are having issues with a gasket - take a look at this simple design that most anyone could make with scrounged mat'ls..... http://www.forging-ahead.co.uk/blacksmiths_water_bellows.htm - JK

Yeah, I had seen the water bellows before, but I am not sure where I could scrounge the big barrels, nor do I have the space for them. My valve idea for the double-chambered version was more complicated. The squash ball is a neat idea.

Thanks,
Rob

[jeremy k]

Rob - I was only suppliing an example - if your forge is a small one - you can use smaller barrels/drums/buckets - that link is just one way of making something that works and if you choose....make one similar in design and as samll or large as you need. - JK

[pkrankow]

So for a brake drum forge with say an 8-10 inch drum a 5 gallon volume bellows is a nice size?

Phil

[rdennett]

Or put another way, what should the displacement be for each chamber?

Thanks,
Rob

[rdennett]

Can I do a bump?

Thanks,
Rob

[tooter]

Why not just build a traditional style two lung bellows from scrap wood and a scrounged piece of canvas? Wouldn't that be simplest?

[pkrankow]

The question isn't simplest or best, but instead what volume would be the practical minimum.

Phil

[rdennett]

Because then I have to buy the wood and canvas. I don't do this professionally and I try to avoid spending money if I can. If I were going to spend money, I would search for a Champion blower or something like it. I already have a pair of double lung bellows, but I think they are too small. Anyway, whether I am making a double lung bellows, a Japanese bellows, a water bellows or whatever, I am curious about how much air the chambers are expected to displace in a single stroke. I calculated that for a 350 cfm bellows, I would have to displace 35 cf of air per stroke assuming 10 strokes a minute which isn't particularly achievable with 5 gallon buckets which hold less than a cubic foot. However, the water bellows pictured in the link aren't much larger than a 5 gallon bucket and yet they work, so I don't think I am doing the math correctly. Any thoughts?

Thanks,
Rob

[Dave Leppo]

" I already have a pair of double lung bellows, but I think they are too small."

measure the volume of the lower chamber of the bellows you have - this is the volume they displace on each pump - make the new set bigger, by at least half.


Just MHO

[ThomasPowers]

I made a Y1K set of paired bellows from a junked printer enclosure---oak faced plywood and a junked awning; but if you *have* to buy stuff....

For my large bellows the controlling factor was to be able to get the entire thing from 2 3/4" x 4' x 8' sheets of plywood which I got cheap as they were stained. So each of the 3 "solid" pieces was cut from appx 1/2 sheet of plywood and the two "horseshoes" were interlaced and cut from the last piece.

The snout was glued up from 2x4 and 2x6 scraps and then draw-knifed to exterior shape.

The "leathers" was made from tarpaulin material scraps from a shop that did wind wings for oil drilling rigs---very heavily treated and lasted over 20 years of abusive use! (spend several summers and winters outdoors, etc)

Time to get bact building another one! I gave away my old one when I moved as I know I would never build a replacement as long as I could frankenstein that one for another decade or so!