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Rebuilding a Side Blast Forge

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At the shop, we have been using a side blast forge for general blacksmithing. It's a great tool as clinker can be removed quickly without great interruptions to the fire. The side blast forge relies on a water cooled tuyere. After more than ten years of great service, the air pipe finally rusted through. I have attached some photos of the surgery and reconstruction.

Forge area with tank removed:


Tank cut open with plasma cutter - at that point it was clear already that the tank needed to be rebuild as well:


Removing the air pipe with a die grinder:


Fitting the new pipe:


Rebuilding the tank from 3/16" steel plate:





Finally leak testing the rebuild tank:


It still needs to be installed and tested but this is how far I got during my holiday break.

Happy hammering.


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Is a side blast forge better than a bottom blast?  I'm just curious.  I haven't seen too many youtube videos out there from anybody in the US that's using side blast forges most the guys I see using them are in Europe or in the UK.  I've always wondered like I said if they actually work better.

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4 hours ago, Alan Longmire said:

Looks good!  And illustrates why I never built one, getting it watertight with my pitiful stick welding skills would be an impossibility.  :lol:

Just put it outside for a week and let it rust up, the rust will seal the holes.  And no, I'm not joking :-)


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Looking great already!

 If my shop had the space I would go for a side blast forge, it would be so nice to build a big reducing fire sometimes.

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Here is the latest progress:

Installed pivot for the air lever.


Plasma cutting and extremely poor sheet metal welding to repair the back. I replaced it with 16 gauge instead of 17 which might make it last a little longer:


Finally installed the tank and the tuyere:


Almost looks like new :-)


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  • 11 months later...

I have just finished building a Side Blast Forge (Mark Aspery design) with a Super Sucker Hood and 10" chimney. Now for the testing of the forge. The Bosh is connected to the Tuyere with a bottom cold water tube and the top is connected to the hot water tube. I am using used antifreeze as a coolant for two reasons, 1, shouldn't rust the Bosh and Tuyere, 2, my shop is in a unheated outbuilding. Tonight it will approach 0 F. The Hearth is covered with firebrick and wood ashes are being used not sand to fill the Hearth. The 10" chimney was salvaged from a grain auger tube that had blown over and kinked in the middle. The chimney is 4' above the shed's roof peak. the Top Hat is a 15" sq. steel plate mounted 10" above the top of the chimney by two steel posts..

The first test fire gave mixed results. I was using Anthracite Nut coal from Tractor Supply. I didn't have enough coal in the forge to make a large mound so the steel bar was inserted in the hot spot in-front of the Tuyere air outlet. the bar heated quickly. 


The Super Sucker Hood started drawing out the smoke and flame. Then, I opened the big door to the shed and the chimney stopped drawing the smoke. Why??? Anyway, I decided to move the fire much closer to the hood opening which should solve the draft problem. The clinker was fished out of the fire with the three prong rake I made in the test firing. 


The next test fire will be done with blacksmith coal and the coal will be piled much higher. Water will be used to control the fire size if it grows out of the hot zone.


My criteria for the permanent size forge was to make no component over 50#. The steel tube frame comes apart in 3 pieces. The Hearth is 2' square by 9" deep with handles. The Tuyere is not part of the Bosh, but it is connected to the Bosh by cold and hot tubes/hoses. The Blower is an old motor driven Champion blower run by a 1/3hp motor running with a 1-1 ratio is connected to the blower with a belt. The air flow is controlled with a Guillotine that is lever operated. With the Guillotine closed. the air leakage will keep the fire from dying down . to meet the 50# criteria, the Bosh was cut down to hold a little over 10 gal. If this size is too small, the top water tube will be run to a screen mesh cooling system that will set on top of the Bosh. This system was used to cool gas engines around the early 1900's.


At the next test firing I will take pictures to post.

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So you're setting it up to thermosiphon? That's cool, but a complication these didn't have. They are just an open-topped tank you top off as the water boils away.  Using antifreeze may be better.  Let us know.

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  • 3 weeks later...

The forge rebuild, top topic,  is from gross rust out of the components that are part of the water cooling system. From what I have read, the water filled components will last about  7-10 years use before rust thru becomes a problem. 


I decided to cool my forge with antifreeze because the forge is in an unheated out building. 

1, Antifreeze won't freeze in my unheated out building blacksmith shop.

2, Antifreeze has rust inhibiters so the life of the Side Blast forge should be greatly increased over using water.

3, Antifreeze can be gotten FREE from your local car dealer.

4, Antifreeze is amore effacing cooling agent over water.

5, Disadvantages antifreeze is poisonous so it must be kept from animals.


I went to our local Ford garage with two each 5 gal. containers. They were filled with used (free) antifreeze which is now filling my system.

Time will tell if the advantages of using antifreeze make good sense.


I will be taking pictures of my new Side Blast Forge with a Supper Sucker Hood when it becomes fully operational.

The 10" chimney was installed with the top rising over 4" above the roof peak. The chimney is a reclaimed grain auger tube that had a kink in the middle.

The forge can be moved to be closer to the hood. Initial tests indicate that at initial lighting of the forge, a temporary tube may be needed from the fire to the hood opening to keep the start up smoke going up the cold chimney. am alternative would be to role up newspaper, light it and place the flaming paper inside the hood to start the draw. I place the flame from by Brush Burning Torch into the hood and noted that the flame was drawn into the hood, a strong draw. 

I will need to add a steel plate behind the Tuyere to keep the stored coal ready to be raked into the fire.

The bed of the Hearth is filled with wood ashes with a small ducks nest dug in front of then air opening. I may cover the ashes that are filled up with wood ashes  to the top of the hearth's sides with a steel cover on both sides of the hearth, leaving the duck's nest open for the coal. 

I designed the forge to be fully accessible from either side. So two blacksmith can work the forge from opposite sides. I have several 130+# anvils that can be placed on each side.              At the end of the forge, there is a huge Leg Vice that is accessible from either side. The vice is fastened to a 3' x 4' 1" thick steel plate welding table.


More information and pictures  will follow when the forge is fully fired up for some heavy blacksmithing work . 

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Are you worried about evaporation? When I use my side blast forge heavily, the water needs to be refilled quite frequently. The heavy gauge sheet metal (I think it was 1/8in) from our last side blast forge lasted over ten years before it rusted out.

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Please go to the "I Forge Iron" forum where I just posted pictures and a description of my Side Blast Forge, Mark Aspery design, and a Supper Sucker Hood.


By using antifreeze, I hope to avoid rust out of the water system. I will collect more antifreeze to replace the evaporated antifreeze. More thinking, it may be possible to replace the Bosh with an auto radiator in a closed system. A fan can cool the radiator.


When I was building the Bosh, I filled it with water to find then leaks, many leaks were found. the water started to rust the interior of the Bosh. When the Tuyere was water tested. it was filled with water for over a week. Rusty water came out after the test was over. 


My big reason to use antifreeze is my forge is in an unheated building in Iowa. I expect to see temperatures with a (- F) many times over the winter. Draining 12 gal. of water at the days end and then lugging the fresh water from the well would be a real pain.


I hadn't thought about the antifreeze being boiled off. I will keep a sharp look out for this problem. I believe that the boiling point of antifreeze is higher than water, how much higher???


Thank you for your response,


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I used your instructions to make an Axe Head. Your instructions were great!  

It took me one try failure to get the process down. Then, I made two successful axe heads and have the third axe head ready for the Bit to be welded in.

After hardening and tempering, the edge is ground and honed. The hammer marks are removed by grinding, draw-filing and finish with sanding to 600 gr..

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Chimney -10" grain auger tube that was scraped, now repurposed. 





This is the rear of the tuyere. The Hot water pipe goes out the top and a similar pipe goes out the bottom. The Guillotine air Controller is used.





This is the flames being sucked into the Supper Sucker Hood.




The Bosh is connected to the Tuyere with Hot and cold piping. I am using antifreeze as a coolant. My Smithy is in an unheated building where the temperature can have a minus sign infant of the temperature.





This is the Hearth. I usually place a steel plate over the hot spot in the fire. This forms an oven to make heating much more efficient. The heated item is a blank to make a Viking Broken Back Knife. 




This is the Blower. The silver covered Flex Pipe can be easily removed for poking clinkers out of the air tube and reconnecting to a hand crank Blower. The Pulley on the motor can be adjusted to increase or decrease the diameter and thus change the air volume.



I will take pictures of the entire forge assembly for the next post.


The Mark Aspery Side Blast Forge design has the Tuyere welded in the Bosh. This is too heavy for me to move.  So, the Tuyere and Bosh are separated and connected by piping.  

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7 hours ago, Alan Longmire said:

Most of us have been banned from IFI for no particular reason we can tell, so it's not a good place to put pictures if you want us to see them.


I refuse to participate in IFI.  I accidentally forgot to delete pictures when I quoted a thread and got reprimanded and had to have my posts approved by a moderator before they could show up on the forum.  The penalty was for 30 days.  I complained to Glenn and he agreed the penalty was a little heavy handed and cut it in half!  Then less than a week later, I posted a statement that was "taken" as political and it was immediately removed and I was told my posts would have to be read and approved by a moderator indefinitely.  No amount of complaining was getting me out of that one.  Haven't bothered to post on the site since.  Shame too because I like the people on that forum.........just don't care for the owner or the moderators. 


Sorry, had to rant.  Back to the Side Blast Forge thread.

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This is an overall view of the Forge and Hood




This is smoke being drawn into the supper sucker Hood. The draw of the chimney system is much better than I anticipated.




This is the Duck's Nest with the tuyere to the left and the hood to the right.




This view shows the bosh that is connected to the tuyere with hoses. the blower is mounted on the table with the forge. The flex pipe can be removed to clear any blockage that mite occur in the Tuyere.


The heated antifreeze flowed thru the tubing into the Bosh. the top tube gets warm and the bottom tube is cold. In the summer, the system will get much warmer and possibly boil.


Are we having fun yet?


PS: Thanks for the warning about IFI.



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