Plans for building a home made furnace

[lazersteve]

Noxx,

PM me and we'll talk about it.

Steve

 

[Cobraj]

Hi all,

One thing I know is Propane, and that is because I work building, repairing and refilling propane tanks and appliances for a propane company. What the pictures are showing is ok but it could have much more info. Like, that should be a high pressure setup. This isn't something you can hook a gas grill line with regulator too a think it will work correctly. I don’t believe this type of furnace needs air supplied force added to the mix. From the pictures it is defeating the purpose of the firebox being in a cylinder shape. Forcing air in is heating the one side of the furnace cherry red while the rest stays much cooler. The idea would be to have the flame swirling around the crucible from top to bottom not heating the crap out of one point that is opposite the burner’s intake. This setup is and has been used many years in things like tar buggies and furnaces like this. I have never seen one that had any other gas or air hooked up to it then Natural Gas or Propane. The trick is to have a starting base for an orifice size, then have an air shutter that will be set and forget it. You need a high pressure regulator not a 12 ounce regulator like on gas appliances. Then you need to figure out what BTU you need, match that with a mixing (burner) tube diameter, then match that with a orifice size and have an air shutter that will handle the highest pressure the regulator can output. Once your setup at the highest pressure the air shutter doesn't need to be moved. If you buy a adjustable high pressure regulator you can adjust the amount of heat as you need it from the highest heat to a keeping the box warm to fire up again low setting.

If this doesn't make sense please correct me. It is much easier to make then you think. I believe so companies still make everything from the hose to the orifice in a high pressure burner kit. I would have to check it out too; I was planning on making one myself in a month or two. :wink:

 

[jimdoc]

Here is a link on where to get the high pressure
regulator;
http://www.cajunshoppe.com/regulator.htm

It is from a page on backyardmetalcasting;
http://www.backyardmetalcasting.com/propanerig.html

I still need to get one of these also as well as the refractory.
Jim

 

[Cobraj]

Hi Jim,

He has it all on the site GREAT! I think I'll build this one it looks like to strong of a flame but the design info looks good. Thank you! BTW no air line is added in this design I thought someone said that.

 

[jimdoc]

Cobraj,
I think that site is awesome, I have his furnace kit,
but need to finish it. I see he has added some pages
recently on melting iron;
http://www.backyardmetalcasting.com/harriette01.html
Jim

 

[Cobraj]

HI,

You could use 3/8 copper tubing that is flared 3/8 nuts and buy an adjustable high pressure like on the link, order a 100lb propane cylinder from your local propane dealer (that20lber won't last long and may freeze up). 1/4 to 1/8 adapter, plus the tubing in the specs and your set.

 

[EVO-AU]

Have you trried LINDSAYBOOKS.COM ? They have books on just about everything in the metals hobby runs, plus some designs for building furnaces. Some are electric and some are gas. Very explicit and exremely easy to build. I've built two over many years and not been disappointed.

EVO-AU

 

[goldsilverpro]

My main complaint about propane is that the tanks freeze up and will eventually shut down. Even a 100# tank can shut down in a couple of hours, in a cold climate, if you are running a large enough furnace. You can tell how much propane is left by observing where the freeze line is.

 

[Cobraj]

Hi,

That is correct. If you use it alot you could get a 420 which is 100 gallon or use 2@ 100lb tanks. The more area that is exposed to vapor the less of a chance of freezing up. Or you can use a blanket to warm it

 

[Noxx]

Does anyone tried to build one of the furnaces on
http://www.backyardmetalcasting.com ??

I would like to but I'm still looking for refractory cement lol...

 

[Noxx]

Do you guys think that it's possible to melt gold with an electric heating element of 1600 watts with 2300 °F Max element wire operating temperature ?
Thanks

 

[catfish]

Hi Noxx:

I melt all my gold with an electric furnace, 1500 watts, 117 volts AC, and at 2000 degrees. My little furnace will go to 2300 degrees F. in about 20 minutes.

The only thing is that if you melt large quanities then it takes a little longer. I normally melt the gold for a bout 30 minutes in order to be able to pour it in to a mold. Just be sure the mold is hot.

Don't make the same mistake I did. I placed my graphite mold in the oven at about 1200 defgrees F. and the damn thing caught on fire. I now heat my mold with a heavy duty heat gun for a few minutes before pouring. It works great.

Before I got my electric oven I used a mapp gas and oxygen torch and now after using this oven for the last couple of years, I would never go back to the torch. Too much sugar for a dime. Also you can keep reusing your melting dishes over and over. Cuts down the cost of doing business. It also requires very little flux to melt the gold. Not to mention the safety factor of an open flame and hot moltened metals, plus the gases they produce.

How is school going?

Hang in there, and please keep my good friend, Alfac straight, if that is even possible, ha-ha.

Catfish

 

[Noxx]

Thanks for the reply catfish.
Is it your home made furnace or you bought it ? Because I'm looking for plans for a small one. Everything I saw on the net is for melting Aluminum or Bronze... I will use a 1600 watt element (115V) rated 2550 degrees F.
Should be enough to melt gold. I don't plan to melt larger quantities of gold at the moment...
Thanks for the input about the graphite mold. I do own one too

BTW, school is going great. And I do my best to keep Aflac on the straight way ! :lol:

 

[EVO-AU]

Noxx: Havee you tried Lindsay Publishing.com ...They have plans for electric as well as gas. I have built two of their furnaces over the years. You can see them on their website. Lots of other great stuff too. Stuff on metalworking from the 1800's, Fanrastic catalogue. Want to build a potatoe cannon? ? ?

EVO :lol: :lol: :lol:

 

[Noxx]

Thanks EVO but their website isn't working... I think the good website is http://www.lindsaybks.com

 

[EVO-AU]

Thanks Noxx, I get their catalogues regularly and wasn't aware of the website logistic. Appreciate the thought. EVO

 

[Lou]

I have a good connection on high quality refractory for cheap. If you're making an electric furnace, you would very much want to have a good hot face, but very little of it, but a lot of insulating material. Kaowool or a lightweight kiln brick are the best ways to go. If you go with kiln brick, you can avoid a hotface (unless you want to melt platinum and palladium, both those both require molybdenum disilicide heating elements, which are costly, but will give you 1800C). For gold, silver, and copper inquartation, I suggest Kanthal nichrome heating elements which are good to about 1200C. Buy directly from them, or off ebay, they're the same if they're new.

I've built a few furnaces, some propane or waste-oil fired (these are for casting mainly), and others that are resistance heated (tube furnaces, and box furnace by Thermolyne). You'll find that building your own is easy, and CHEAP when compared to buying new or even used furnaces.

I've never built a resistance furnace before, but I've rebuilt/retrofitted older ones. All you need to build your own are the heating elements (1500W would be more than sufficient for what you're doing), a way to thermostat it (so a thermocouple of some sort, preferably a type S as they last the longest), refractory brick, a variac for controlling power delivery, and general electronics knowledge.

I post at www.backyardmetalcasting.com forums under the same username, and indeed, there are many good ideas to be had. If you'd like, I can ask some other members there who have built their own versions of the ''Lil' Bertha'' or Gingery based electric furnaces.

 

[Irons]

I built one a number of years ago using a large coffee can for the outside. I wrapped masking tape around the nicrome coils and wrapped that around a cardboard form the dimensions of the inside. There were 3 elements which gave me 3 seperately controllsble heat zones. Once the elements were wired in and the core inserted in the can, I poured refractory cement to fill the space between the core and the can.

Once the cement was dry, I baked it to drive out any moisture and when I powered up the elements, the cardboard core and masking tape burned away and voila, the $20. furnace.

I used it for pulling crystals from a melt and presented a paper at an student ACS meeting. I have a nice certificate on my wall from the American Chemical Society for that project.

 

[Lou]

Neat Irons!

There are some very cool things you can do with crystal pulling. Aside from zone refining, it's a damn good way to get extremely pure material (single crystals). There are even ways to make a whole crystal orient a certain way.

 

[Irons]

It was really rube goldberg apparatus.

I mounted a spindle on an old electric clock mechanism and a bit of string with some Pt wire to hold the seed crystal.

It had to be cheap because none of the faculty would sponsor me because they thought I was nuts, so I had to do it out of pocket.

When it came time to present my paper, they all volunteered to be my sponsor.

I was the only student that didn't have one that year.

I went back to visit 10 years later and they still had the apparatus and crystals on display in the main hall of the Physical Sciences building.