Author Topic: Box Bellows  (Read 24876 times)

Offline Elnathan

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Box Bellows
« on: September 25, 2012, 10:50:40 PM »
My summer project this year was building a Japanese style box bellows, and since I am now about as done I as I can be without testing it on a real fire, it is time to show off a bit!

A bit of background: The box bellows are the Asian equivalent of the traditional double bellows used in Europe. In the US, they are mostly associated with Japanese swordsmiths - I took the basic design for mine out of a book on Japanese swords - but they were actually invented in China about a thousand years ago and have spread all over that end of the Pacific rim for all kinds of metalwork. They are pretty simple - a box and piston with a set of intake and exhaust valves at each end. As the piston is pushed and pulled, the intake and exhaust valves open and close alternately, the exhaust valves emptying into a secondary air chamber, often referred to as the "birdhouse" and from there into the tuyere.

Over the last six years or so I have been trying to put together a small blacksmithing outfit, without much success up until now. I don't have money to buy stuff and I am in a rather unsettled period of my life in which building a large, permanent forge is not practical now nor seems likely to be in the near future. Lately I have been looking more and more at the very minimalist equipment used by early medieval smiths in Europe and pre-Industrial Revolution cultures elsewhere. I decided on the box bellows because 1) it can be worked with one hand, necessary for a one-man operation, 2) I am a better woodworker than leatherworker, 3) it is a bit more compact than a traditional European double-lung bellows, and 4) because it can be placed on the ground and used, in a pinch, with a hole dug in the ground for a forge or a lined box placed on the ground, unlike a double lung bellows which has be used with a built-up forge. If I do get a more elaborate forge sometime in the future I can make legs for the box bellows. I am planning to use charcoal for fuel; I don't know if it will work well for coal.

Now on to pictures! Here is a photo showing the bare box. You can see the two intake valves at the top, the small hole 3/5th of the way down is the hole for the push-rod:

Another shot of the bare box showing the exhaust valves near the bottom:


Here are the valve flaps. All four are identical, made from masonite backed with cloth from an old pair of pants.


Here a couple shots with the piston and valves installed.

Inside:

Exhaust valve:


Birdhouse built:



The hole in the side is where the pipe to the forge will go. The piece of molding helps seal the joint there, since there are no screws from the inside to pull the top piece tight against the body.

And finished!



The material is mostly 3/4" cabinet-grade plywood. I put the nice side inside the box, as I wanted to have as the inside of the box as smooth as I could, to minimize air leakage. The push-rod and handle are made from poplar - probably not the most durable choice, but I was on a budget and had some 4' sticks of poplar that I could plane down nice and straight.  At the moment it doesn't have any sort of gasket around the piston or the hole for the push-rod - traditionally they do, but mine seems to work pretty well without it. I will probably add some in the future, to increase efficiency. The finish is two coats of polyurethane, not very traditional but heat  and scratch resistant.

The main box is about 36" long, 13" wide, and 21- 1/2" externally, and about 34" x 11 -1/2" x 20" internally, with a useable stroke of about 29-1/2", though I think I will probably only use about 24" of that stroke most of the time. 36" inches is about as short as you want to get - I have found that since my arm seldom pushes directly in line with the handle, the rod tends to bind a bit when the piston is drawn completely back. A longer box would help with this.

Total cost was about $30.00 for the plywood and about $8.00 for the screws, plus the use of some scrap to build the birdhouse and some leftover cans of polyurethane that my parents have had for 12+ years and where happy to see go.
« Last Edit: January 14, 2020, 07:03:13 AM by rich pierce »
A man can never have too much red wine, too many books, or too much ammunition -  Rudyard Kipling

Offline Kermit

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Re: Box Bellows
« Reply #1 on: September 27, 2012, 02:04:57 AM »
Interesting machine!
"Anything worth doing is worth doing slowly." Mae West

Offline horseman

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Re: Box Bellows
« Reply #2 on: September 28, 2012, 12:12:30 AM »
 I really enjoyed looking at the pictures and reading your explaination.   Interesting.  Also interesting was seeing Chesterton quoted.  He wrote one of Micheal Collins' favorite books.

Offline Curtis

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Re: Box Bellows
« Reply #3 on: September 28, 2012, 12:30:17 AM »
Nicely done, it should serve you well!

Curtis
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Sometimes, late at night when I am alone in the inner sanctum of my workshop and no one else can see, I sand things using only my fingers for backing

William Worth

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Re: Box Bellows
« Reply #4 on: November 09, 2012, 03:48:04 PM »
Next step, a water wheel to run it.   8)

Offline Hungry Horse

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Re: Box Bellows
« Reply #5 on: November 09, 2012, 07:10:50 PM »
Consider a tub wheel. It will not require gearing to change the direction of rotation. By spring loading the handle you could probably run it off of a cam. Just a thought.

                         Hungry Horse

Offline Hungry Horse

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Re: Box Bellows
« Reply #6 on: November 10, 2012, 06:29:07 PM »
I'm just curious as to why you decided to make a box bellows, instead of a more traditional pattern?


                   Hungry Horse

Offline Elnathan

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Re: Box Bellows
« Reply #7 on: December 05, 2012, 07:41:52 PM »
I'm just curious as to why you decided to make a box bellows, instead of a more traditional pattern?


                   Hungry Horse


Well, it actually is a traditional pattern, just not one found in Europe or America.  ;) I decided to make a box bellows instead of a western-style lung bellows because I was more confident in my ability to make a working bellows from wood than one from leather, and because it can be used with a forge built directly on the ground, whereas a double-lung bellows has to be elevated above the ground and therefore requires a built up forge.
« Last Edit: December 05, 2012, 07:42:44 PM by Elnathan »
A man can never have too much red wine, too many books, or too much ammunition -  Rudyard Kipling

AZshooter

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Re: Box Bellows
« Reply #8 on: November 23, 2014, 10:06:29 AM »
When I was a kid, my uncle wanted to forge a scraper or some kind of blade at the end of some roundstock, and couldn't get a big enough fire with the torch.

Grandpa told him to go set up the barbeque, and built a box bellows using a cardboard box that slid inside another box.  He added a long sheetmetal nozzle, some kind of flaps inside with innertube material and had it finished then the fire was ready.  It put out a pretty good blast of air, and the scraper project was finished in no time.

We played with it a little, trying to fill it with water to see how far it would squirt, but after a couple of tries, it got waterlogged and fell apart.

JB2

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Re: Box Bellows
« Reply #9 on: December 18, 2014, 07:10:44 PM »
excellent project, functional and probably simple enuff for me to build!  Not to second guess, but if it stood on end with handle up, could it be powered with a foot-pedaled spring pole?  Think spring pole lathe, Roy Underhill style.  I wondered where I was gonna get a blower for my forge, now I know! ;)

Offline PPatch

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Re: Box Bellows
« Reply #10 on: December 19, 2014, 04:16:35 AM »
Kool!

dp
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Offline KentSmith

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Re: Box Bellows
« Reply #11 on: December 20, 2014, 12:02:02 AM »
saw one in action at an event this summer.  Tight to start but once moving it supplied a nice blast with little effort, certainly more efficient looking than the trad. lung bellows i have used.