Making Great Bellows

[John Martin]

My fall-winter project that won't doesn't need to be done in the shop, is making a two great bellows. As time permits through the winter, I am going to make two great bellows, for the future shop. One for each forge. Anyhow, I was wondering what size I should make them, I've read

BP0127 Bellows Construction
&
BP0141 Building a Bellows

I was wondering how big I should make them. I also need suggestions on what kind of leather to use, and where I could look for some. I can get the wood, glue, everything, but have no idea where to get the leather from. These will be hung from the ceiling, by leather straps, and either operated by a strap that hangs down, or a wood handle. One more questio, for the top and bottom, should I glue pieces of wood together, or would plywood be acceptable??? Note, none of this is going to be historically correct. Just two double bellows that work real good for coal forges.

So while I am gathering materials, I would like to hear any suggestios, or things to do and not to do.

Thanks in advance,
John

Edited September 29, 2008 by m_brothers

[Frosty]

Instead of making two great bellows you could duct one to both forges with a diverter valve. Pumping can be done from the off forge with a couple pullies and a cord and handle.

If you're planning on using both forges at once a great bellows should handle it unless you both want BIG fire, then you could more easily share one forge.

Think canvas rather than leather, lasts longer, is easier to work and is cheaper.

Frosty

[John Martin]

Jerry, do you know where I should go about for trying to find canvas???

[the_sandy_creek_forge]

Tandy Leather

be prepared for "sticker shock"

-Aaron @ the SCF

[Frosty]

Look for "tent and tarp" suppliers. If they don't sell material they'll be able to tell you where to get it. I buy it from the local fabric store though. Should be really easy to find.

Frosty

[Rob Browne]

The canvas is a great idea and, yes, plywood would work very well for the timber bits.

Sounds like a great project.

[Max Mulholland - Tetnum]

um rip stop nylon or canvas work well leather ai a pain
and for canvas go to the local big box store (HD, lowes, wally world)and buy a canvas drop cloth

[Woody]

If you want leather, check these people out, they are where I got the leather for the bellows I made in BP 141. I also have the plans if you need them.

Brettuns Village Leather These people are cheaper than Tandy and they have any type of leather you want.

[ironrosefarms]

Great project!
One thing I picked out that could cause a problem, I don't think I would hang the bellows from leather straps. The leather will eventually dry rot and cause a serious hazard above your head. The one I helped build and install was hung with hand forged chain and timber bracing.

Also I agree canvas would be easier and cheaper to work with, the man I worked with for several years used canvas on his personal bellows (not the one I helped build). He used an old military tent that he picked up from a surplus store for very little. Then to keep the canvas in good condition he oiled the canvas. Once hung in the ceiling it was not at all obvious that it wasn't leather on those bellows...

The valves can also be made out of a heavy rubber inner tube. The bellows I mentioned above had rubber valves that he rubber cemented canvas to on the side away from the lumber (it gave the rubber more body)...

One of the biggest enemies of a bellows is rodents, the use of a hot pepper spray on the leather or canvas often will deter the varmints from chewing their way into the sides.

[Johannes]

hi ya all!
greath project!! i was thinking of building a greath bellows myself in the spring to.
I understand why lots of you advise canvas instead of leather, indeed its cheaper en has less maitanece , but it may be worth to consider the fact that leather is much more fire resistend than oiled canvas.. this is especially importand if your shop is rather small (en forge and bellows are relatively close together), of course there are flame bloking spray's on the market, but i dont know if they would stick to oily canvas??
Am i beeing overly concerned here?

[ironrosefarms]

"Am i beeing overly concerned here? "
Not at all Johannes, it is a good point that you wouldn't want to put something particularly flammable in a location prone to spark or flame. As I was reading your post the thought did occur that most tent material is coated with a fire retardent (NOT intended to make it fire proof though). The oil that my friend used on his bellows before his passing was a simple cooking oil, not overly prone to igniting without a direct flame. Non the less a good point to think about.

If leather is used it would be wise to give it a yearly checkup and put some leather conditioner on it to help ward off the fiber breakage at the creases and help keep dry rot at a minimum. The last time I seen the bellows I helped build it was full of patches because it had not been maintained.

[Jymm Hoffman]

A key feature in building bellows I have not seen here, maybe I over looked it. I have been able to make a smaller bellows out of a larger one work better and have build another smaller set, both working better than many larger ones. The tip I picked up years ago from another smith, still working at Hale Farm in Bath, Ohio. Put more leather (or canvas) on the top half, as much as a 2/3 to 1/3 proportion. The bellows on my traveling forge is only about 24" wide and about 36" long. You don't have to build 6 foot long bellows. Maybe someone that knows the measurements used a Colonial Williamsburg can chime in here. I don't believe they are very long. The ones on my traveling forge I used garment leather from a Tandy store that had it in their scrap bin. I have built with canvas, but prefer leather. If you can take your time you might be able to find a deal on some garment leather. It is very soft and pliable, works great. I have also used a bellows at a local historic site that spent way too much money on getting them rebuilt and used to heavy of leather. They are hard to work.

I would not try to valve one bellows to run two forges. Plus you will need a rigid frame to mount, or hang them regardless of where they are, overhead down low, etc.

Edited September 30, 2008 by Jymm Hoffman

[Frosty]

Using a flame retardant on the canvas is a good idea but needs to be done before oiling or waxing. Simply soak in a solution of borax and water and let it dry. You can buy commercial flame retardants too if you wish.

The thing to remember is they're flame Retardants, they won't make it fire PROOF. However, most times your bellows won't be exposed to direct flame or hot materials. Hopefully anyways! There's always the chance of a backfire, especially if they're mounted below forge height but backfires don't last long enough to light dry canvas let alone boraxed and waxed canvas. Hem the canvas! Frayed cotton catches fire easily.

Believe it or not oiling or waxing will make canvas more flame resistant than if it's dry. What happens is flame or hot materials coming in contact cause the oil or wax to boil off and carry heat with the vapors where dry cloth absorbs the heat and is more likely to catch fire. This only works for a few moments under hot material and maybe 20 secs in a flame. It is something however and every little bit counts.

What kind of oil makes a difference too, some are more flamable than others check the MSDS for the specific flash point to be sure. Waxes generally have high flash points and being dry to the touch hot scale, etc. won't stick as easily. Still, check the MSDS first.

Nobody come back and say I said oil and or wax will fireproof or even act as proper retardants on fabrics, they aren't. Oils or waxes only provide a few seconds buffer, once they get burning they go faster and hotter.

Frosty

[NateDJ]

A decently balanced /weighted flapper valve on the bottom of your firepot / tuyere should allow the blow back to escape into the ash bucket instead of into your blower shouldn't it?

[Francis Trez Cole]

when I made my bellows I put in straps so the opening pressure was not on the leather they lasted about 15 years. when I make my next set I will be canvis. In Flroida leather dose not hold up.

[Frosty]

A decently balanced /weighted flapper valve on the bottom of your firepot / tuyere should allow the blow back to escape into the ash bucket instead of into your blower shouldn't it?

Yes, it'll certainly help relieve the pressure of a backfire.

However without some sort of check valve between the tuyere and bellows or placing the bellows above the firepot, flamable gasses can and will migrate into the bellows. Then when you give it a pump fresh air/oxy plus the heat from embers fallen into the ash dump can ignite it. The resultant explosion (usually a good woof rather than a BANG) happens inside the second chamber of the bellows. If you're unfortunate enough to get a good BANG it can do serious damage to the bellows.

The addition of a positive check valve between the bellows and firepot should take care of the possibility but having the bellows mounted above the firepot WILL eliminate it. I imagine putting an inverted "P" trap like under your sink would do the same thing and still allow you to put the bellows below the firepot.

The potentially explosive gasses are formed when the blast is idle. Without the positive air flow the volatile gasses formed as coal cokes and CO formed during any combustion process will settle and flow downwards being heavier than air. These can build up to a significant quantity but as there is no air/oxy present nothing happens.

Also when the blast is idled embers are more likely to drop through the air grate and lay in the tuyere uncooled by the blast. Even if there isn't enough oxy to sustain combustion in the embers there's a chance they'll still be hot enough to ignite a flamable gas mixture when the blast is resumed.

The good thing is these gasses must obey the laws of physics and can NOT flow uphill without assistance so an inverted "P" trap SHOULD work and placing the bellows above the firepot WILL work to prevent significant backfires. You may still get little ones from the small amount of gasses trapped in the tuyere itself but these are not much more than a pop.

Backfires aren't a significant danger using rotary blowers as they're "transparent" air movers. They won't hold much flamable gas and a resultant explosion won't be contained so it won't do much more than scare the bejeebers out of you and maybe singe some hair off your crank hand.

Charcoal is far less likely to produce backfires as the volatiles have been driven off in the charcoaling process, same with a coke fire. However both will produce CO so a backfire is possible; not likely but possible.

Frosty Edited September 30, 2008 by Frosty

[CurlyGeorge]

Hey John, if you look at the forge cart in my gallery pix, you'll see that it is covered with canvas, not leather. Also, may i suggest using intake hole that are big enough. The bellows that I use has two intake holes on the bottom that are 3 inches in diameter, each. We still have to hang two window waits on the bottom section because it won't recover fast enough to pump up the top, without them. Good luck. You will love using it, once you get used to them.

[Travis Covington]

CurlyGeorge,
Can you tell me where your plans came from? I have a group of reenactors that want to help me buid one.
Thanks Travis

[CurlyGeorge]

Covforge, I didn't make it, myself. But the guys that did, got the plans from Smoke-N-Fire, I think. Then they modified it to fit the axle and hubs that they had donated. I would like to make another one, for myself, on a small enough scale that I could wheel it in and out of my box utility trailer. I hope that my pix were helpful.

[CurlyGeorge]

Frosty, on the cart forge that I use, there is a weighted ash dump on the bottom. Would it be a real good idea to sorta hold that open for a pump or two on the bellows, after taking a break, or do you think that would not be of much use? The bellows is not much higher than the intake of the tuyere. I've been lucky, in that "so far" I have had no backfires in a little over a year of using this one.

[John Martin]

Okay, well I'll keep you all updated as this process beings this month.

[Frosty]

Probably propping the ash dump open when you stop pumping would be the sure bet for keeping the flamables from building up. Then again if the bellows is higher at all you shouldn't have a problem.

I've only had a couple small backfires seeing as I use a rotary blower and learned a sharp half turn or so to get the air moving stopped them completely. First time it happened my bejeebers left for good.

Frosty

[CurlyGeorge]

Thanks for the info, Frosty. I really don't want to blow aoart the historic sites bellows. Boooooom!!! LOL.

[CurlyGeorge]

That would probably get the wrong kind of attention. LOL.

[John Martin]

lol. it might be attention, but it might be the firedepartment's.