I imagine a propane forge would be as noisy as the rivet forges the railroad here used to use. Very noisy. One could hear them a mile away. So one should not consider using a propane forge in a city. Right? . . . .Next, how many burners would a propane forge need to be able to easily heat an eight pound sledge hammer head, so it could be worked?
The one I built my son isn't that noisy. We run it in the garage, and if it were objectionable, SWMBO would have let us know. I wear hearing protection when something's really noisy, like a 4.5" grinder. This isn't bad at all. I patterned it after Ron Reil's designs, i.e. naturally aspirated. A forced air design would probably be a little noisier, depending on the blower.
Objectionable in this town would have been a coal fired forge, which is what the kid wanted. And SWMBO would have blown a fuse at a 12" galvanized duct sticking 4-5' above the roof ridge line.
Pete Keillor
Not at all! Of course if you are planning to heat eight pound chunks of metal you will need to crank up the volume a bit... I use a chamber with an inside volume that is about eight inches in diameter by 2 foot long and I hold it at 1750-1900F with a flame that is barely audible. If I need to crank it up for welding heat then it has a soft roar. Not what I would call loud though. This is a T-Rex burner and the forge chamber is lined with a couple of inches of Inswool. I have a commercially made forge that runs on forced air and is considerably louder and a LOT less heat efficient that I'm not at all happy with... My T-Rex in the forge I made would heat your hammer head to forging temp in about 15-20 min - single burner. Personally I would use a more robust design if I was interested in forging that much metal.
GA
I have no idea what you heard from the railyards, but I am certain it was not a rivet forge. A rivetting hammer perhaps, along the lines of a pneumatic hammer?
All the forges I have been near are pretty quiet, its the equipment around them that make noise that could be heard from outside the room, stuff like power hammers and the like.
A propane forge usually runs pretty quiet, a dull roar at best, but nothing that is loud enough to require raising ones voice to be heard over, until one gets into seriously BIG forges.
To work a lump large enough to make an 8 pound sledge head, you will need a forge large enough for it to fit into, that is all. It will heat faster if there is some thermal mass in the forge walls for it to draw heat from, otherwise the cooler mass acts as a heat sink, and cools the whole interior space. This is less of an issue with ceramic wool lined forges, as the material has little mass to heat and cool.
Cheers Trevor Jones
I'm pretty new to it all, but I just built my propane forge and have been playing with it for a couple of months.
What I've got is a forced-air burner on a forge with an interior diameter of about nine inches, and a length of about 18 inches. It
*can* get loud, but what I'm finding is that it really does not have to to do most things.I put a 0-60 high pressure regulator on the tank, and have tried everything from a tiny stream of gas to full-out. Up to about 30 PSI, with the appropriate amount of air, the forge noise is hardly noticable. When it's cranked all the way open, it makes a roaring noise- but it is not loud enough to be heard outside the garage.
Just as a note, if you do build one- 1 layer of 2300* kaowool isn't quite enough to run a forge at 60 psi, at least in mine. 15 minutes of that will get the outside of the forge glowing, and I don't much care for that- it could damage the forge body, if not cause some rather nasty fire hazards. I've been running it at about 15-20 psi for most things, and it's quite possible it would be fine at even lower pressures.
I'd feel pretty confident in saying that the forge I describe above would heat up an 8 pound hammer head. I did heat a block of some unidentified hunk of alloy steel (my best guess is that it is 4140) that was about that big to an orange heat with the intention of making an swage block from it- but found that my ability to hold it firmly enough and hit it hard enough to do that particular job just isn't quite there yet.
It takes a few minutes to get the initial heat, but recharging it is pretty quick.
The forge has one burner in the center, with a 2" diameter nozzle, and a blower attached to one end. Total cost to build it was about $20, and the only part that was even remotely tricky was mounting the gas jet into the pipe elbow. It did not require much tweaking, as I have heard the blowerless versions sometimes do, but it does require electricity.
************ It was rivet forges ok... on 90 pound natural gas and 150 air pressure. Boxes about 18 inches or 20 inches on all sides. I really missed the boat. Up until 1984 we had 3 blacksmith shops here, owned by the Anaconda Company. One at the railroad, one at a company foundry, and one on the smelter. I even knew one of the railroad blacksmiths, but never thought in a million years I would ever developed an interest. I was once in the smelter blacksmith shop in about 1954 as they re-bent (cold) a set of main leaf springs for my friend. There must have been 24 men there, with the laborers, journeymen, and apprentices. I don't know how many worked at the foundry, but I know they had some huge steam hammers. Parts of the movie 'Runaway Train' were shot in the blacksmith shop on the railroad. And the roundhouse locker-room.
UHHGGG! Thats a monster of a furnace! I can understand how you would hear it from a distance then!
Not what would be refered to as a rivet forge in most other circles though, thus my misunderstanding. The forges that are commonly known as rivet forges are a smaller version of a coal forge, set up to be fairly portable, in order to heat rivets for steel construction.
The arrangement you describe sounds like it was dreamed up by someone that wanted to get some form of revenge on the guys that had to use it, as it would make for a bloody miserable day to have to be around it running all the time. It sounds wasteful and expensive to run, too.
A gas forge or furnace built by anyone that gives a pinch of ---- for their own sanity, is a fairly quiet device.
For a forced air furnace, a 4 to 6 inch squirrel cage blower is lots of air, and gas pressure depends on how small the orfice is on the inlet pipe, with a lower pressure needed to get an equal amount of gas through a larger hole. For the forced air burner I built, with IIRC a #55 hole, I run from 2 psi to 15 psi, and can get steel to sparkle in it.
I have a friend that is casting iron with a naturally aspirated burner, and it runs quiet enough to be around for extended periods of time as well.
Cheers Trevor Jones
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