Jmercier Posted May 4, 2009 Share Posted May 4, 2009 I'm in the planning stages of building a double chamber bellows for use with a portable demonstration forge for a historical re-enactment group and I have a few questions for any of you out there who have made bellows before or who use them regularly. I've read up on everything that I can find about creating one, and I know that historically they seem to average between 5 to 6 feet long and 30 to 36 inches wide. I also know of the recommendation to have 2/3rds of the leather/canvas on the top chamber and 1/3rd below rather than a 50/50 split to make a more efficient bellows, but what I cant find is, what's the smallest dimension that you can get and still be effective for a coal forge for demos? I'm looking at 4feet long by 24 inches wide as about the largest size that I think I could really lug around / set up / travel with effectively, but I'm not sure if shrinking the bellows to that dimension will result in not enough airflow for a coal fire. Is there anyone who has experience with bellows that could give their recommendations? I know that at Bellows he has the dimensions 30" wide by 40" which seems that it should be similar internal air capacity as 24" wide by 48" long , but it's still in practice a decent bit less for the latter than the former. Would a 4 foot x 2 foot bellows work? Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted May 4, 2009 Share Posted May 4, 2009 mine is 4 x 7 ft, If I work very hard at it, I can weld. here are the photo's Fenris Forge Events Quote Link to comment Share on other sites More sharing options...
Jmercier Posted May 4, 2009 Author Share Posted May 4, 2009 I just spotted this set of bellows on ebay 220344541639 which are 20inches wide by 44 inches long, which is a little smaller than what I've been planning, so it looks like while on the small side of great bellows 24x48 should probably work. I'm not so concerned about forge welding with a demo set up, since that's not the most crowd friendly thing to be doing, but i want to be able to forge comfortably =) Quote Link to comment Share on other sites More sharing options...
dablacksmith Posted May 5, 2009 Share Posted May 5, 2009 it will work fine thats bigger than what ime useing currently .. the secret is go deep ! make the leather or canvas go real deep (like 10-12 inches on bottom or more) it will increase the volume without increaseing footprint . also i went with a triangle shape instead of the typical rounded . it was what i saw on a portable forge for tinners work ..also are you going bottom draft or side draft? if bottom draft make sure you dont create any apreciable drag on the air flow .. with bellows i find that volume is more inportant than pressure ... cause you can always add weight to top of bellows to increase pressure... good luck! Quote Link to comment Share on other sites More sharing options...
Jmercier Posted May 5, 2009 Author Share Posted May 5, 2009 The forge is bottom draft, I measured my lumber and I've actually got enough width in the boards to do 48x30 if I'm careful with how i join the boards together to make the 3 "solid" sections, so I should be alright. (the dimensions are basically .75x11x48 pine boards that iv'e got, i guess they're supposed to be 1x12 boards 4 feet long) Any recommendations as to the type of joint to use between the boards ? A biscuit joint? tongue and grove joint? doweled butt joint? Quote Link to comment Share on other sites More sharing options...
Rob Browne Posted May 5, 2009 Share Posted May 5, 2009 A biscuit joint should be OK for the boards. As for the volume. If it is a bit smaller than the usual wouldn't that be like a smaller hand cranker, it just supports a smaller fire and forge? It would still work, but not for big jobs but then you are not likely to be doing big jobs at a demo are you? Quote Link to comment Share on other sites More sharing options...
dablacksmith Posted May 5, 2009 Share Posted May 5, 2009 A biscuit joint should be OK for the boards. As for the volume. If it is a bit smaller than the usual wouldn't that be like a smaller hand cranker, it just supports a smaller fire and forge? It would still work, but not for big jobs but then you are not likely to be doing big jobs at a demo are you? there is a minimum size .I have built 3 bellows for portable forges so far and if one is to small it will still work but you will not get the heat you need amd you have to pump faster and add more weight to the top of the bellows it makes um not as user frendly... it works but tou have to spend alot more time with the fire and things get marginal. I think the size discussed will work fine tho . make sure everything seals up good and it should work great! have fun Quote Link to comment Share on other sites More sharing options...
Jmercier Posted May 5, 2009 Author Share Posted May 5, 2009 Now i just hope that I can get both this and the forge i'm building done in time =) I'm supposed to be doing historical blacksmithing demonstrations for the Historic Highlanders recreation group at the rhode island highland games in 5 weeks, and I never have enough time in the shop as it is =P Thanks for the help. Hopefully I can get the 3 planks joined and glued up and ready to cut out the teardrop shape in them tonight so that thursday or friday I can take a saw to them. Quote Link to comment Share on other sites More sharing options...
Pault17 Posted May 5, 2009 Share Posted May 5, 2009 Jmercier, I am not trying to 'jack your post, but was unable to find the one I was looking for. But, this followed (in my head) what you are asking about. being a man of scant pocket change and also looking for a useable portable demo forge that is vaguely period, I chanced upon this image in an old Google on-line book. I have seen this before in the forum but after reading through post after post, I have to jut ask: has anybody built or aquired one of these? I am thinking and currently working on making on to fit an IFI special 55 forge with side blast - unless I can make it an up-blast, but with the circular double on the underside. thoughts? thanks in advance and again, sorry for 'jacking paul p.s. please move this elsewhere if need be Quote Link to comment Share on other sites More sharing options...
Grafvitnir Posted May 5, 2009 Share Posted May 5, 2009 (edited) Hi Paul and JMercier. First for JMercier here: The Celtic Knot - Building A Bellows Fed Portable Forge is a portable forge for Demos and the bellows does not look that big but he does talk about the proportion 1/3 to 2/3. Now, here: http://cd3wd.com/cd3wd_40/JF/JF_OTHER/SMALL/04-084_blacksmiths_bellows.pdf is the Inversin Bellows for the third world made with inner tubes but you could change that to leather or Naugahyde or whatever. Here is a single action bellows and a home made blower for a 55 gal forge (and it kind of looks like the picture you attached Paul): http://cd3wd.com/cd3wd_40/JF/JF_VE/SMALL/04-110.pdf Paul, I was looking for info on this kind of bellows a few weeks ago! Here is the link to my question: http://www.iforgeiron.com/forum/f11/another-bellows-question-11319/ maybe you have more info on it. I included a picture of one homemade in New Zealand. It seems they are used in the UK but nobody seemed to had a diagram Hope it helps Rub Edited May 5, 2009 by Grafvitnir Quote Link to comment Share on other sites More sharing options...
Pault17 Posted May 5, 2009 Share Posted May 5, 2009 Rub Quote Link to comment Share on other sites More sharing options...
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