SReynolds Posted February 23, 2012 Share Posted February 23, 2012 I hope the pictures tell a story here. The small (rivet) forge has the factory number of tuyere holes; 19- 13/32 inch holes!! That is almost 7/16 inch dia holes and for a small forge like this. That is how its made. Seems like quite a lot of air holes for a small (8") fan!! The masonry forge with gigantic bellows.........5- 3/8 inch holes. That is it. Works perfectly too I might add. Use it all the time. Plenty of air flow and when you need it too. Question, what gives with these air holes? The bellows, in my opinion, would need the 19-13/32 in holes and the rivet forge would only require 5- 3/8 in holes. RIGHT??? Who thunk this stuff up?? Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted February 23, 2012 Share Posted February 23, 2012 " if it ain't broke don't fix it" Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 23, 2012 Share Posted February 23, 2012 Factor in PRESSURE. The bellows is going to squirt out that air even if the tuyere is a bit blocked. The vaned fan will stop working if it gets to a certain back pressure. So which one needs the lower restriction in the tuyere? Quote Link to comment Share on other sites More sharing options...
Ramsberg Posted February 23, 2012 Share Posted February 23, 2012 Yep, just like Thomas said, more or less. The great or double bellows, as pictured, is really a two part machine, but both parts work on a force in, pressure out basis. The force applied to the bottom chamber of course is applied by the smith and its delivery rate into the top section is determined by the difference between the force applied, the resistance produced by the head presssure in the top section and the valve passage area. The delivery from the top section to and through the grate is determined by the difference between the force applied to the air inside it produced by the weight of and on the top board and the back pressure or head resistance produced by the piping and grate in the forge. If one pumps the top section dead full and keeps pumping then the pressure on the air going to the forge is determined by the force applied by the smith to the bottom chamber. What makes a pair of great bellows so powerfull is that one only need to add more weight to the top section to get more air through the forge, assuming that one can pump against that pressure to fill the top section. A fan has the same head balance or pressure balance issues, but its head on the air(by head I am speaking of inchs of water pressure) is determined by the velocity of the tips of the fan blades. There are also a great deal more losses involved with a centrifugal fan then a bellows chamber, as in head losses in the air flow. Remember that besides the friction losses in the fan chamber, piping to the forge and grate of the forge there are also the very significant losses of the air passing through the pile of coal. That alone can accound for at least 1/2" of water pressure. Small fans with shallow blades also are not nearly as efficient at producing high head pressures as larger fans with deeper blades. So they had to design that rivet forge to give as little restriction as possible for that small fan, otherwise it wouldn't work at all! The only rivet forge I have ever used was a neat looking reciprocating lever type. I really didn't like it, it didn't seem to give enough air to the fire to do any serious work. . . which is probably because it wasn't designed for serious work and just rivets! HA!!! Caleb Ramsby Quote Link to comment Share on other sites More sharing options...
Glenn Posted February 23, 2012 Share Posted February 23, 2012 The air opening for the 55 Forge is 2-1/4 or 2-1/2 inch pipe with 2 pieces of 1/4 round stock as a grate. Lots of room for air. I control the air by diverting air out of the pipe between the fan and the forge. I have burned fines (coal dust) with this set up as well as lump coal. I use a 4 inch squirrel cage fan to generate air for the forge, with a 3 inch expandable metal pipe between the fan and forge. Quote Link to comment Share on other sites More sharing options...
SReynolds Posted February 24, 2012 Author Share Posted February 24, 2012 Yep, that helps me out! Makes sense to me. Both work really well. I have, in my possession, an old Champinion forge and it has no grate. (The tuyere I suppose??) Anyway, You can look right down into that 2- 3/4" pipe and that isn't going to work. I'm designing a new gate for the fire to lay upon. I was wondering how many holes it should have as I don't have the original as an idea like I did with the other Champion rivet forge. By the way, I had to discover the weight atop the bellows myself. I had nobody to coach me on this. I did have an exxperienced smith in the shop and his take on that was very little weight is desired, and he removed it. I then set the weights back on as it gives more of an air blast. With out that weight, it more/less settles down and blows very little air when you let go of the pole. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 24, 2012 Share Posted February 24, 2012 Each bellows-forge system is unique in my experience not to mention often tweaked to suit the primary user. My double lunged bellows I could pump to welding temp with my pinky. A friend worked at a historical Site where the people who put in the system knew squat about using one and he messed up his shoulder and hip over 10 years having to HAUL down on the cord to pump even a small fire. Generally mine did not need a weight but I hung a hammer on it when it did. I liked that the outflow took a reasonable amount of time as it gave me time to switch hammers/tongs, grab a drink, etc before it needed pumping up again. If I wanted to blow the tuyere clean of small stuff I could inflate the top chamber and still keep pumping to over drive it. The only thing I didn't like about that bellows was that it took up most the bed of my pickup when I moved it in it's frame. Quote Link to comment Share on other sites More sharing options...
SReynolds Posted February 24, 2012 Author Share Posted February 24, 2012 This one is quite large and continues to provide an air flow long after I stop. However, it is going to wear me down. I now have tennis elbow. From what I do not know, but the bellows operation among holding tongs tight to my work piece, has aged me in only two short years time. Yea, I went to the doctor. It is tennis elbow. It don't hurt to pull down on the bellows, but it gets old. I have asked about installing my large Buffalo Blower. That didn't go over well as the society has $$$$$$$ in the bellows. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 24, 2012 Share Posted February 24, 2012 Where is the pivot set on the lever? I set mine so the lever is almost at the balance/raise point so it took little effort to pull it down feeding the top chamber. The worse ones didn't have a lever with an adjustable pivot point. They just used a rope on a pully so you had to exert all the lift yourself. Quote Link to comment Share on other sites More sharing options...
Ramsberg Posted February 24, 2012 Share Posted February 24, 2012 Hey Thomas, Any idea what sizes the air passages were between the bellows and the coal? It sounds like they were very large, that would account for the light pumping required, as well as possibly rather large valves between the lower and upper chambers. Just saw your reply. Are you saying that you set the pivot on the lever so that the weight of the lower chamber was overbalanced just enough to pull itself down, but not so much that it put a load on your pull? Hey SReynolds, The port size for the Champion firepot can be calculated, but the best is to find out what size has worked very well for someone then duplicate it. Just for fun, here are some pictures of my second forge, with the fan taken off of a cloths drier, hand crank from an old meat grinder, ran out of sheet for the hood so one side is made from a 55 gallon drum that I flattened. Also my nephew looking into the fire, test burning wood pellets. That thing burned charcoal really well, but lacked enough head pressure to handle coal very well, it burned coke OK, but not great. Like an idiot I put the idler on the wrong side of the belt! Caleb Ramsby Quote Link to comment Share on other sites More sharing options...
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