Bellows nozzle length

[ede]

Some time ago, I acquired a mostly reconditioned bellows that didn't include a nozzle.  I would like to build a tapered nozzle with a sip roll out of 16 gauge and am looking for ideas on dimensions since I don't currently own a coke forge.  I say tapered because that is what I generally seen in pictures, but am not opposed to using straight pipe as well.   The ID of the bellows hole is 2 1/2 inches so I have that part figured out, but generally how long are the nozzles before they go in the tuyere?  Thanks in advance!  

 

 

[ThomasPowers]

Yes definitely!   (or it differs depending on how your smithy is set up.  The bellows that are set in the rafters tend to have a much longer air path than the ones set right next to the forge.  In general distance helps if  you are protecting the bellows for exposure to forge heat so the oldstyle ones with the bellows mounted behind the wall are mounted closer.)

See medieval examples in "Cathedral Forge and Waterwheel"; late 17th century in "Mechanicks Exercises" and perhaps late 19th century in "Practical Blacksmithing" (perhaps as I don't recall looking for that info in it...)

[ede]

Okay distance helps avoid backfires, good point.  Thanks for the resources, Thomas.  I will check into "Cathedral Forge and Waterwheel" which looks interesting.   I looked in the Practical Blacksmithing and I tell you, M.T. Richardson was not a fan of the bellows!  

 

[Charles R. Stevens]

Properly sized, built and balanced belows are a joy to use with charcoal and bitamith coal, but remember he was in the era of everything "scientific" and modern. So a natural predudice against the "quaint and antique" may be forgiven. Andercite and Coke do not like bellows (or hand cranked blowers for that matter). I find them suthing, and I burn up less stock.  

[ede]

That's interesting, Charles and good to hear that they can be soothing to use.  Out of curiosity, why do Coke and Andercite  not like bellows?

[SLAG]

Anthracite coal and coke are more concentrated forms of carbon. Bituminous coal has as little as 60% carbon. (smithing bituminous, coal has 70% and greater concentration of carbon).  Bituminous coal has bitumen in it. That is hydrogen-carbon chemicals called hydrocarbons. Anthracite has a much higher % of carbon and very little bitumen compounds  The bitumen compounds burn more readily than carbon. That is why air must be continuously blown into the fire to keep the harder anthracite coal burning. Coke has even less hydrocarbons in it.

Coke is produced by cooking off the bituminous fraction in the absence of air. (so the coal is not burned up in the process). Coking drives off water, propane, benzene and other  hydrocarbon chemicals in its production. These are the chemicals, in the  uncooked bituminous (soft) coal, readily burn in bituminous coal. So a continuous air blast is not necessary as it is for burning anthracite, or coke. The latter two require constant air. They will go out if the blast is stopped.

Just a little metallurgy, and chemistry for those who are interested or wondered.

Regards to "tout la gang".

SLAG.

[Frosty]

Interesting about the chemistry. I was of a different opinion but mine is from experience and not a lot of that. What I observed is probably the result of what Slag describes. What I noticed is breeze, coked bituminous coal is light weight and burns easily and HOT. Where forge coke made form anthracite is more dense is harder to light and keep lit, burns longer but not as hot.

My observation and hypothesis being that breeze is a less dense form of relatively pure carbon than anthracite "breeze" which is also relatively pure carbon. bituminous breeze has a greater surface area than anthracite breeze, oxidizes more easily = faster shedding energy more quickly and easily so it's hotter and stays lit more easily with less super charging.

I've noted the same general tendency burning softwood charcoal vs. hardwood charcoal. Less dense burns faster and hotter per volume where hardwood charcoal lasts longer but is cooler, again per volume. By weight the total BTU output is close to equal.

Those are just my thoughts based on my observations. I don't claim them as fact.

Frosty The Lucky.

[Frank Turley]

I have an old bellows that has the original nails and hardware, but to use the thing, it needs to be rebuilt. It's in a storage shed, but there's so much heavy stuff in front of it, I couldn't get to it to measure, so I'll give you a photo and a guesstimate on measurements. The bellows itself is about 5.5 feet tall excluding the tapered nozzle nose. The nozzle is of sheet metal about 4"D at the base and 1"D at the end. It's about 12" long. Although the bellows is old and well used, there is no fire damage to the end of the nozzle, so it was inserted into some kind of tuyere opening that protected it. We assume that there was a hearth and that the old fires were side blasted, not bottom blasted. I once corresponded with Ken Schwarz, master smith of Williamsburg, Virginia, and he figured that at Williamsburg, the nozzle went into a huge cast iron block that was cast with a tuyere hole through it. The iron block would have protected the nozzle and would have provided a somewhat heat resistant tuyere entry to the side blasted fire. Not everyone of that period would have had access to a cast iron setup, so there were other methods of entry to the fire.

[SReynolds]

My bellows looks like the picture above. But the nozzle doesn't blow into the tuyere. It blows into a horizontal pipe. Then the 90°ash dump the to the vertical pipe then the tuyere plate the fire sets on.

[ede]

Slag, thanks for the chemistry lesson.  What limited experience I have with a solid fuel forge has led me to preferring coke.  It sounds like one would really get a workout if trying to maintain a coke forge with a bellows so I can see the benefit of coal here.

Frank, thanks for the photo of your old bellows, that reference will help for sure.   

[ThomasPowers]

Well a well engineered double lung bellows can keep a pretty constant air flow if you keep your hammer intervals short.   Mine would let me cross the shop and take a drink from my mug on the work bench and walk back and it would still be pushing air.