Forge from an air tank

[Ted Ewert]

On 6/27/2018 at 4:41 PM, Mikey98118 said:

You are over thinking things. Taper or step will give nearly the same effect.

Thinking and designing are what I like about projects. I like to try new things. Copying exactly what someone else has already built is no fun. 

[Frosty]

What Mike and I are hoping for here Ted is someone who'll take things other folk have done and come up with something better, easier, cheaper, etc. Unfortunately if what you like doing is repeating other folk's mistakes then we're going to have to look for improvements elsewhere.

Frosty The Lucky.

[Mikey98118]

What Frosty said; just so.

Even people's mistakes give some of us new facts---sometimes. Peoples triumphs give the bulk of us encouragement; that's much better.

[Ted Ewert]

On 6/27/2018 at 6:28 PM, Frosty said:

What Mike and I are hoping for here Ted is someone who'll take things other folk have done and come up with something better, easier, cheaper, etc. Unfortunately if what you like doing is repeating other folk's mistakes then we're going to have to look for improvements elsewhere.

What mistakes am I making Frosty, and where does it say I am under any obligation to your agenda? This is an experimental forge design and I have made no claims to the contrary. I welcome any constructive criticism or suggestions, but in the end it's my project and I'll build it as I see fit. 

[Steve Sells]

Many of us are very attached to our mistakes after all the work we put into making them

[Ted Ewert]

Darn right.

[Frosty]

The only obligation you're under here are the forum rules. To me? Zip. I've offered you my suggestions and the benefits of my mistakes. My last reply reflected your preference to make your own mistakes and disappointment. 

You're shop, your rules do as you wish.

 

[Mikey98118]

2 hours ago, Steve Sells said:

Many of us are very attached to our mistakes after all the work we put into making them

Sublime; I can hardly wait to use that line! 

[Ted Ewert]

Anyway, I got more cement and cast the floor this evening.

I also cut the hole in the side of the tank for the burner.

I overestimated the amount of cement I would need for the floor so I made a test casting with various size acrylic rods stuck in with release agent on them. I want to see at what stage I can pull them out without affecting the shape of the hole (or sticking). Solid rods develop vacuum issues unless they have a vent hole. 

I also started rebuilding my burner

[Latticino]

Are you planning on just having the layer of Kastolite as your only forge liner?  I think that you will find that the ~2" thickness you have there will provide insulation similar to 1/2" of high temperature insulating blanket (and be a fairly significant thermal sink/battery).  Hopefully you plan on adding at least 1" of blanket between the cast interior and the shell.

 

 

On 6/27/2018 at 1:44 PM, Frosty said:

I use crayons (approx 3/8" dia.) as lost wax cores to make the outlets

I'm in the development process for casting a new multi-outlet burner for my forced air system as well.  I found some alternate core material that I think may work well: hanukkah candles.  They are small diameter and you can even get them tapered or fluted (and they come in packs of 90...):

[Ted Ewert]

I'm planning on putting 2" of wool around the inner tube. I want to get everything lined up and secure first before doing that as a final step.

I checked the Kastolite test batch this morning and was able to easily remove all the acrylic tubes without any distortion in the cement. This was after 12 hours of setting in approximately 65 degrees. In light of this, I see no reason to use crayons or candles as a burn out medium, unless they are found convenient for their shape or economy. I am going to cast a new burner this weekend using acrylic rods (which are only about $5 for 6 feet). I have also found that after about 24 hours of setting I can shape a casting with the belt sander (Lots of dust though!). This is handy for squaring off the ends of the tube, or cleaning up any rough spots.  

[Ted Ewert]

I've been looking into the ingredients of Kast-O-Lite. It is basically a high temperature mortar type compound using a modified recipe of Portland cement, powdered quartz (SiO2), Aluminum oxide (Al2O3) and a fibrous substance to hold things together. Both Silica and Alumina have melting temperatures of over 3000 degrees F. 

What this means in terms of casting is that it is very similar to using concrete or mortar. Continued hydration after initial setting will increase the strength of the product, as well as having a similar curing duration. 

This may all be old news to you guys, but it lets me know what I can expect regarding casting parameters.

[Frosty]

7 hours ago, Latticino said:

I'm in the development process for casting a new multi-outlet burner for my forced air system as well.  I found some alternate core material that I think may work well: hanukkah candles.  They are small diameter and you can even get them tapered or fluted (and they come in packs of 90...):

What's the Dia. of the candles? Plain wax without the pigmented chalks (I think it's chalk in crayons, maybe tempra) would burn out more easily. I found the smaller the orifice diameter the greater the skin friction and more restricted the flow, it's a nonlinear ratio. 

Crayons are easy to taper if you think it's a factor or worth the effort, just roll them warm with different thickness kiss blocks. It also partially strips the paper and just that might be worth the hassle.

Frosty The Lucky.

[Ted Ewert]

After 24 hours of curing, I tested the sample for machinability. I was able to easily ream out a taper in one of the 3/8" holes.

The reamer blades will get clogged with cement but it's easily removed with a wire brush.

Next came the sanding test. I sanded that rough surface you see above on my 6" stationary sander, and also beveled the edges a bit.

I also did a test drilling with a regular steel bit in the drill press and it went through like butter.

This material holds together pretty good at this stage of curing, but is still soft enough to machine. If you remove your form at this point you can hand sand any rough edges and clean up holes with a hand drill. You can also sand it down to size if you made it a bit larger. 

I suggest doing a test sample for yourself to get the feel of the material before machining a final piece. 

One other note... I removed the pieces of rod after 12 hours and it worked fine. However, the material was still pretty soft and I think 18 to 24 hours might be better for longer pieces to avoid any chance of deformation. 

 

Ted

 

[Ted Ewert]

I poured the burner for my forge this weekend. Grandkids were down for the day yesterday so shoptime was limited. 

I used 1/4" acrylic sheet for the form, and used acrylic rods for the holes. Since I buy scraps from Tap Plastic (a dollar for a 12 x 12 inch sheet), the form including the rods cost me about $7. I taped and clamped the form together, which worked well. I used some release agent on the rods, but frankly I don't think they needed it. They were a little snug in the steel base I used, but once they got out of that they slid right out. 17 perfect holes.

The form pieces came right off too. I washed them off and they are ready to go again if I need them. 

Here's the setup (sorry about the focus):

These are 1/4" rods. I chose 1/4" to be sure there was no chance of the flame burning back into the plenum. Crayons are 5/16". In hindsight that would have been fine. 

Here it is after the pour"

I made a little raised area where the rods are to hook into the opening of the cylinder for support. That didn't turn out so great as I'll explain next.

Here's right after I took the rods out:

Everything is fine at this point. The problem arose as I began tapering the holes. I didn't allow enough space between the holes, so when the material got thin it started to crumble. The raised part is only 7/8" thick and the taper started infringing on the integrity of the outer wall. 

Consequently it turned out to look like this:

Kind of a mess! I'm thinking of cutting that whole notch off in the bandsaw while it's still soft enough. Then maybe tapering every other hole and see how that works. If it doesn't work well I'll just cast another one. 

I don't know why anyone would want to use painted wood and crayons anymore. This method of casting is much easier. 

 

Ted

 

[Ted Ewert]

OK, I cut off that notch and reamed the holes again. Turned out much better. There was a little crumbling between a couple of holes but functionally it shouldn't make any difference.

[Ted Ewert]

Had a busy day today in the shop.I finally got the forge insulated with 2" of K wool around the burn chamber. Once that was done I decided to set it up for a test run. 

It actually performed better than I expected it to. I was a little worried that the 1/4" holes might not be big enough, but that didn't turn out to be the case.

Here's it running a little rich to show the swirl:

You can also see that I goofed up the floor and had to relevel it. The new floor is still setting up so I only ran short tests.

Here's a more normal burn:

This burner runs quite smooth and adjusts well. Part of the reason for this is that I am spinning the air right after the blower. This not only mixes the gas better, but provides higher velocity at the input to the burner tubes.

Here is a picture of my air / fuel setup:

That black device right after the blower is the spinner. It spins the air CCW at a fairly high rate or speed. The unusual burner entrance takes advantage of the spin to increase the  velocity of the gas as it enters into the tubes.

Here's what the inside of the plenum looks like:

Visualize the gas spinning CCW as it enters the plenum. The exterior layer of air has the highest velocity, so when it hits the tubes it translates into higher pressure. This is how I can increase the pressure of the gas at my tubes without getting a bigger blower. BTW, I cut all those metal tubes out and just made a long, skinny rectangular hole where they were. 

I tried this setup without the spinner and the flame was smaller and spluttered a lot. 

This type of spinner is also great on the input to an Internal combustion engine. I had this particular one on my old toyota Corolla and it increased the mileage considerably.

For some reason, spinning air always burns better the a linear flow. 

 

Chears,

 

Ted

[Ted Ewert]

Finished it today. It heats metal quite well. 

[Lou L]

Seems like a clean build to me.  Id love to own it.  I’ll be rereading this thread for ideas soon enough.  Thanks for sharing your experiments with us.

[Ted Ewert]

Thanks Lou, glad you enjoyed it. If you have any questions let me know. 

[MikeTausig]

First, let me say that I appreciate the time and effort you took in crafting this thread complete with pictures. Very nice, and informative.  

As for the forge, it’s a beaut. I bet it outperforms some entry level retail rigs. I wish I had the know-how to do this. 

Cheers. 

[Ted Ewert]

Thanks for the kind words Mike, I appreciate it. This is the first forge that I built from the start with a general plan. Now I have to figure out how to beat hot metal into something recognizable.

[Glenn]

Start with what you have available and make it look like what you want. This is where modeling clay becomes the medial of choice to practice with.

[Ted Ewert]

On 7/8/2018 at 2:55 AM, Glenn said:

Start with what you have available and make it look like what you want. This is where modeling clay becomes the medial of choice to practice with.

Thanks Glen. I did manage to produce a recognizable object today. It's only a simple hook, but it's a start....

[Ted Ewert]

I made a couple of additions to the forge.

I added a little "head shield" below the burner. You can see how the swirling gas would hit the bottom of the burner.

I also added little section on the roof of the front  to try and contain some of the heat in the back

Then I got the forge up to temperature and they both fell off. Didn't matter anyway since this forge gets #@!!%* HOT! All that work I did trying to figure out just the right taper didn't make a darn bit of difference. The forge is so hot that anything coming into it immediately ignites. You can't even see a flame. The only adjustment is how much flame you want coming out the front, if any. The whole inside was bright yellow. 

 You don't want to get anywhere close to that slot either. The thing scares me a little. Heats up metal good and fast though.