Airframe Construction Shorty Core

The airframe for Shorty is constructed using five feet of 2.5" square tubing.
First, it must be cut to length, and then at a 45-degree angle.
My low-speed, high-torque, cold-cut carbide chop saw was just the tool for the job.
Once the frame was cut, then each piece needed slots cut.
A skinny wheel on a side grinder made the long cuts and a jig saw made the short cuts.
A flap disk was used to clean up all the cuts.
After the pieces were all prepped they were clamped to the welding table and tacked in place.
A final check was made that all was as it should be and then Gerry welded it all solid.
Tabs will be welded around the sides and all thread will be used to snug the airframe with superwool gasket up to the core firebricks.
The door will built next.
I have an 8 x8 piece of fire glass that will be installed for a window.

While helping Thomas to build the air frame for the shorty door today, when we got to laying out the air channels (particularly the main air inlet at the bottom) we  wondered why it has two horizontal square tubes attached to each other which share the main air opening instead of just one.
The only thing we could think of is that maybe Peter wanted to give the door more surface area to seal against that one piece just wasn't going to be enough to provide.

Gerry Parent wrote:While helping Thomas to build the air frame for the shorty door today, when we got to laying out the air channels (particularly the main air inlet at the bottom) we  wondered why it has two horizontal square tubes attached to each other which share the main air opening instead of just one.
The only thing we could think of is that maybe Peter wanted to give the door more surface area to seal against that one piece just wasn't going to be enough to provide.

That reason you mention above was following from a couple of others: the first being to provide enough space for the air stream to split and going through two 90º bends, both left and right. The tube on its own proved to be too restrictive, as long ago as for the DSR2 prototype. The second reason was how to provide a threshold for the ashes to stay in the firebox. And last but not least room for the door seal. The air inlet in the lower part of the door, as shown in the pictures of DSR2, DSR3 and Shorty alike proved to be unpractical in the long run.

So far, the air frame looks good, please go on!

Peter van den Berg wrote:That reason you mention above was following from a couple of others: the first being to provide enough space for the air stream to split and going through two 90º bends, both left and right. The tube on its own proved to be too restrictive, as long ago as for the DSR2 prototype. The second reason was how to provide a threshold for the ashes to stay in the firebox. And last but not least room for the door seal. The air inlet in the lower part of the door, as shown in the pictures of DSR2, DSR3 and Shorty alike proved to be unpractical in the long run.

So far, the air frame looks good, please go on!

All makes perfect sense. Thank you Peter.

Today Tom and I will probably get to welding the tabs on the air frame to have something for the tension rods to hold the core tightly together.

Meanwhile, some pics and a video of our progressively larger fires to cure the refractory casts.

https://youtube.com/shorts/JvUDVb8G5Yk

We finished welding and grinding on the new airframe this morning.
We placed it in front of the core where it goes to get a few shots and plan our next moves toward finishing it up.
We need a door built for it, that door will get an 8x8 window.
We need tabs welded on the frame to attach all-thread and angle iron brackets at the rear to tension it all together.

Shorty lit off much better this morning, with less steam from wet bricks and less smoke out the riser.
Gerry lifted off the riser cap to see if the double ram horns had formed and was able to take a short video of it.

The door frame is looking great so far guys. Love that Evolution chop saw for accurate & clean cuts.

Following along with your process and thinking about building my door this summer. For the air slots on the inside of the frame I'm thinking it may be easier to drill 3/4" holes for the ends of the slots and then cut with the angle grinder. Any thoughts on this approach since you have experience cutting with the jig saw? I'm pretty sure I have a 3/4" drill bit.

Peter van den Berg wrote:
That reason you mention above was following from a couple of others: the first being to provide enough space for the air stream to split and going through two 90º bends, both left and right. The tube on its own proved to be too restrictive, as long ago as for the DSR2 prototype. The second reason was how to provide a threshold for the ashes to stay in the firebox. And last but not least room for the door seal. The air inlet in the lower part of the door, as shown in the pictures of DSR2, DSR3 and Shorty alike proved to be unpractical in the long run.

So far, the air frame looks good, please go on!

When this is proven to work well (and I few doubts), I do think it will be a elegant addition to our stoves.  So far I have NOT burned the paint off of my batch rocket stove and have got that to over 500 degrees a few times (really burning hot on a triple back to back burns)   So with this AIR cooled frame set up, I expect even better results.  

I enclosed a few photos in case there are some not sure what this frame looks like.  ( the door is off and not shown)   Just the frame and then some airflow paths drawn in.

Thanks Peter for all your hard design work.  And as always, I don't mind being corrected if I have something off, Scott

Scott Weinberg wrote:I enclosed a few photos in case there are some not sure what this frame looks like.  ( the door is off and not shown)   Just the frame and then some airflow paths drawn in.

The air path isn't entirely correctly drawn, sorry Scott. Imagine the two bottom tubes are U-profiles, with the open side welded to each other. Together, they'll form a double-height tube, through which the air can freely flow without much friction at all. Looking closely to the pictures of Tom and Gerry and you'll be able to see clearly what I mean.

No problem at all,  (on the clarification)  This is a case where I had drawn it right, but it showed like the bottom two tube were not open as you described.  In reality, I do have them open, but my drawings show a big radius corner on each tube.  When in fact the radius is quite small with the center cut out.

Should work great.
cheers
Scott

Glenn Littman wrote:Following along with your process and thinking about building my door this summer. For the air slots on the inside of the frame I'm thinking it may be easier to drill 3/4" holes for the ends of the slots and then cut with the angle grinder. Any thoughts on this approach since you have experience cutting with the jig saw? I'm pretty sure I have a 3/4" drill bit.

Sounds to me like a great idea Glenn.