Burner sizing.

P

probrwr

Joined
Dec 31, 2015
Messages
73
I am putting together a firebrick forge and trying to get my head around burner requirements.

The forge space will be 9 x 4 x 4.5. Not huge but open on the ends. I like the simplicity of the Atlas butners and the price but am concerned that the 30k unit will be too small and the 100k unit too big.

Can the big burner be throttled easily to reduce its output?

Are the other options that may be better?

Mike

Sent from my SM-G920P using Tapatalk
 
162 cu.in. - For that small a forge chamber the 30K will be more than enough.

I would suggest using a spare brick to full or partially block the rear end as needed.
 
Sorry to contradict, but 30k isn't enough for a chamber that size, especially with open ends. Given the dimensions, you would need 65k BTU to attain the 400 BTU/inch^3 recommended for welding heat. You might be able to forge with 30k, but it's still going to be on the cold side given the open ends. Definitely go with the 100k and save yourself some future headaches, it's only $10 more. Also, given the bigger burner, that will give you headroom to cut off some corners of the bricks to get closer to a round chamber. ROUND is the key to a good bladesmithing forge.

Make sure to send me a note to include a choke for you.

Charles
 
Thanks Charles. I was considering the end being closed with firebricks. I generally consider a brick type forge for forging only, so I usually go on the lower side. But, I see by your calculations that 30K would be half what is optimal.

100K will be a better match.
 
Thanks to both of you. I will order the 100k and add a note for the choke.

Trying to figure out how i make a round hole with 6 bricks . I laid two side by side. Then layed two on thier long ends perpendicular to form walls and two more across the top.

Sent from my SM-G920P using Tapatalk
 
If you are using the right brocks, just use a regular wood spade bit or hole saw. The bricks are very soft. Hard firebricks are not what you use to make a forge from ( they are for lining fireplaces and wood stoves).
 
They are the IFB bricks. I was referring to Charles saying to make the chamber round.

R/
Mike
 
probrwr said:
Thanks to both of you. I will order the 100k and add a note for the choke.

Trying to figure out how i make a round hole with 6 bricks . I laid two side by side. Then layed two on thier long ends perpendicular to form walls and two more across the top.

Sent from my SM-G920P using Tapatalk
Click to expand...

This way :)


23vye4i.jpg

amdu13.jpg

2s0e1ya.jpg
 
I actually had just figured out that the Graham forge was probably layed out that way. Need more bricks....

Sent from my SM-G920P using Tapatalk
 
Yep, that's exactly how the Graham is laid out. Here is a more traditional 6 brick layout. Just grind/carve away to make the chamber roundish instead of rectangular, it'll make a big difference.

74d3272b4ee148a2ad849d607526924d.jpg
 
I've used a 4-brick arrangement before now:



There's obviously no centre to provide the pilot location for a holesaw so I used a piece of scrap wood, holesawed a hole in it, clamped it to the top of the bricks and used it as an external pilot to guide the holesaw for the first cut. After that, there was enough meat in the hole to keep it straight for the rest of the way. I used a standard holesaw, so had to go in steps of about 1 1/2" and break out the core each time the holesaw bottomed out, but it was pretty easy.

If you've got 6 bricks, it should work well as it leaves one for the front and one for the back that you can make smaller holes in to restrict the openings.

I pinned my bricks together with welding rod. I cut the rod with a pair of end-cutters to leave a a sort of blunt chisel point on the end, chucked it in a drill and drilled through the IFB with it, snipping off the ends of the rod once it was through. Primitive but effective.
 
Why is round better? I understand the swirl part but does it make that much difference?

Sent from my SM-G920P using Tapatalk
 
It make a lot of difference. I don't know if there are any exact tests results, but based on observation, I would say a square chamber vs a round one has about 60-70% less even heating.

Angling the burner about 20° and positioning it so it creates a swirl down the chamber is very important. If planning to do HT, a round chamber is almost a requirement on a smaller forge.
 
You must log in or register to reply here.
Back
Top