"Hothead" Dual Fuel Metal Melter (Part 1)

Warning melting and pouring molten metal can be dangerous if you are careless and don't take the proper safety measures, you can start a fire you can't control or suffer serious burns, safety is your responsibility, wear proper PPE,, don't pour on bare concrete, and have a dry fire extinguisher at the ready.

I built this furnace in the summer of 2016. I had built a small electric furnace when I was much younger and did a bit of casting, I loved the process and have always wanted to get back to doing some more casting.

This furnace is a Dave Gingery style furnace because it is built in three parts, the top and middle section lift out of the way when you are ready to pour, this results in less heat loss in the melt and is much safer for crucible handling.

The Furnace body is 16" in diameter by 24" high, cut from a water press. tank. Max aluminum capacity is 30 lbs. in a steel crucible. Bronze or iron 20 lbs in a #8 clay graphite crucible, #10 will fit but I don't plan to cast much iron.

I planned on two types of burners. A Reil type atmospheric burner to melt aluminum and a Lionel Oliver type waste motor oil burner for high temp. metals or when my oil barrel is full.

Plan Of Action

(Part 1)
1. Build shell and shell attachments.
2. Build carriage and lifting mechanism.
3. Install refractories.
4. Build fan and burners.
5. Finished furnace pictures.

(Part 2)
1. Build day use waste oil tank.
2. Build propane system.
3. Build casting accessories, pouring shanks, molding bench and flasks.
4. Do some casting for furnace performance testing.

So here we go with this build. I was a little short on fab. steel so I put an order in and started with the furnace shell.The first picture is the finished furnace so followers will know where I am headed with this build.

These two sketches  were early concept sketches some elements changed in the actual construction such as the pre-heat rack, but the dimensions remain the same.

The shell sections cut from a water pressure tank.

My steel order arrived.

Bottom tacked in place.

Burner port cut.

The port assemblies ready to install and a 1 1/4" burner pipe to verify clearances.

Port extension installed.

Burner adjustment spud bolted in place.

Burner pipe in installed.

The burner pipe pushed all the way in to check side wall clearance. Refractory will be 3.5" thick, so the 4" I measured is just about right, accounting for the burner flare. The burner spud will also allow for some adjustment up, down or sideways.

I should explain here that I am a bit of a packrat when it comes to collecting salvaged and discarded, interesting materials and mechanical assemblies. I have many boxes stored under workbenches full of this kind of stuff. They are all labeled but it does not make it much easier to find a piece I know I have somewhere, when I need it. Because I use alot of salvaged materials in this build, formal plans would not be easily universal. So as always I encourage potential builders to use and adapt what you have, or can inexpensively find in salvage yards etc.

I next installed 6 alignment tabs, hammered out of junk box brackets and the lifting bolts and attachments.I am using 3 1/2" shoulder bolts to extend the measurement between the lifting arms by 4". This will allow a 20" shell if I decide to play with a larger furnace in future and allow me to use the same carriage and lifting mechanism.

I designed a preheat rack into the lid of the furnace. It is important that the scrap metal you intend to melt is dry, free of moisture and contaminants. the preheat rack allows you to preheat your scrap before adding to your melt. Below, the preheat rack installed. The shell is essentially complete, The preheat rack will get a finished edge around it's circumference to avoid snags later and the middle section will get a refractory support ring but I can now move on to the mobile base.

Next I built the mobile base for the furnace carriage. The next picture is the angle iron and deck cut, mitered and clamped ready to weld.

The casters and mounts ready to install. Didn't have a matched set so, heavy iron core swivels on furnace end and standard duty on light end.

Casters installed and all welded up.

Crucible failure catch pan slide supports installed.

And just to try it out to see how it fits.

Next I welded and fitted the ingot mold/crucible failure catch pan. This one is for aluminum melts. I will make a sand lined pan later for the occasional iron melt. It is a good idea but it is not my idea, I have seen at least 2 other builders use this type of set-up.

Next I bolted the bottom section to the deck using 3/8 X 1" NC bolts and lock washers.

Next I will work on the lift assemblies. The lift assembly is bolted to the deck and can be removed if required. Sockets to support the main arch were drilled to accept 1/2" X 4" bolts and welded to the deck.

Two angle iron braces bolted top and bottom .

2000 lb. capacity worm winch and cross brace to mount it on.

The arch with lifting worm gear winch bolted in place. It is important that a self braking winch is used here to prevent accidental drops of the furnace body. A worm gear is self braking a boat type winch with pawl is not.

Here are the parts for the arch mounted lift. I made the U bolt and clamp. The rest I put together out of my junk boxes.

Next I built the lifting frame and arms to bolt to the furnace body.

Here is the lifting frame installed on the lifting arch. Bolted to and lifting the furnace body.

So the next assembly is the foot pedal lid lift. Here are the parts.

To lock the lid in the raised or lowered position I went back to the junk box and found a spring loaded plunger, combined with the flat bar from a broken quick clamp, it will lock the lid in the selected position.

 Next I will work on the lid lifting rod and struts. the lift rod is 1" hot rolled and the struts are 1 piece of 1/2" ready rod, this makes for easy adjustment at the locking nuts on the lid brackets.

Next I rolled the flat bar from a broken quick clamp into a ring and welded to the edge of the preheat rack, to finish it off.

Before starting on the refractory I still had another crucible failure catch pan to build for high temp. melts. I used the dome out of what was left of the water tank I used for the furnace shell. I sliced of 2 sides and welded on angle iron sides/slides. To Store it I welded 2 more mating slides under furnace deck. The dome is 3 1/2" deep at center, 1 1/2"s of sand on the bottom and built up on sides will easily contain the contents of a A8 crucible.

So on to the refractory installation. I made a trip to the Toronto area and picked up a good supply of refractory materials. Don't be alarmed there is enough materials in the picture below for 3 projects.
The products from left to right, 2 pails of 3000* firebrick morter, 5 bags of castable 3200* hotface, 3 bags of fireclay, on top 2 and 1/2 boxes of AP Green G-26 insulating firebrick and 5 bags of Bentonite clay for making green sand, 3 bags of southern recommended for aluminum and 2 bags of western recommended for the heavier metals brass and iron.

I also picked up a A-8 clay graphite crucible for iron melts.

 First operation was to cut and fit the G-26 firebrick. My 12" bandsaw with a dull blade did quick work of it.

Here I have cut the opening for the burner port.

The pattern for the burner port was made in 2 parts and held together with a wood screw with the head cut off and repointed.  This because the pattern will have to be removed from both directions.

Pouring day was quite hectic. First the brick was installed. Each one submerged in water (to prevent quick absorption of moisture from the hotface) then a light buttering of firebrick morter and fitted.
Then the burner port pattern placed and hotface packed around it, the bottom was poured with hotface, then the inside form was placed and hotface poured to the top of the lower section. A saran wrap separator was put in place and the middle shell section was put in place and the process repeated. The next picture is the furnace right after the forms were removed. Everything was allowed to slowly dry for a couple of days covered in plastic.

Here is a pic. of the bottom with plith block in place and a good view of the burner port.

This is a pail of the off cuts from the shaping of the G-26 firebrick.

I crushed up these firebrick off cuts and mixed it 2 parts firebrick fines to 1 part fireclay. This will be the insulating mix for the furnace lid.

 The lid with retaining wire and fender washers.

 The top vent pattern in place.

I filled the top with my insulating mix leaving 1 1/2" space from the top and around vent pattern to finish off with hotface. I also poured a couple of plith blocks with my left over hotface.

 The finished lid after drying for a couple of days covered in plastic.

Almost done next I'll work on the burner fan and burners. I have 2 surplus fans from Princess Auto but they have squirrel cage wheels, good for volume not for pressure and the motor only draws 1.5 amps @ 120 V. I also have a couple nice surplus motors also from Princess Auto that draw 3.5 amps and are rated 1/4 HP. Using D. Gingery's book "How To Design And Build Centrifugal Fans" as a guide, I made and installed 4 radial type blades into the original fan runner. This should increase press. without impacting volume. I also made a adapter plate for the new motor.

Old fan dismantled.

New motor, fan housing, modified fan runner and adapter plate ready to assemble.

Adjustable damper instaled.

Fan set up for testing with quickly made manometer.

Measured just a little more than 3" water column, the old fan could not have been more than 1". Expected some vibration but got lucky and ran smoothly.

The design of the duel fuel burner is virtually the same as Lionel Oliver's "Hot Shot"(1st picture). Mine is one size larger 1 1/4" instead of 1" burner pipe, He also used 1/8" black iron pipe for oil injection I used 1/4" brake line tube, and total length is 3" longer. In a later version Lionel extends the oil pipe to the end of the burner pipe which I did here. I did not have a 2" nipple long enough for the blower pipe and my pipe dies stop at 1 1/2" so I welded 1/2 a close nipple to the end of a 2" pipe. Hey!! it worked☺. I resisted welding the oil delivery pipe to the blower pipe, threading it instead so that if I need to make changes in the future, it can be dismantled.

The burner installed in the furnace burner port.

The fan mount is adjustable and locked down with large wing nuts.

The fan installed on the burner.

The atmospheric burner is based on the Ron Reil burners and Rupert Wenig modifications. My gas jet is drilled to a #52 drill bit. My bell reducer is 2 1/2" to insure sufficient air at high settings. This burner does not require a fan so when not burning oil this is the preffered burner, it does require higher gas pressures.

The choke is an axial type similar to the ones in this photo.

Here are all the parts to build the burner.

The burner assembled.

 To test it I made a rough 15* flare, The flare is not needed when installed in the furnace.

Set up for testing on my portable vise.

Shortly after start-up carburizing flame.

Cranking it up, oxidizing flame.

Nuetral to slightly carburizing flame. The setting desirable for melting.

Now that the burners were running I started to fire the furnace lining to finish drying it out. Brought the temp. up slowly over the course of 2 days. On the second day I decided to try the atmospheric burner in the morning heat. It lit but insisted on burning well down the pipe. No adjustments I made would get it out of the pipe. Tried it on the vise, good there. Removed welded burner pipe and filed down the weld ridge down the middle of the pipe, tried in furnace, no go .Because of furnace back pressure the venturi effect of the reducer was not generating enough velocity to overcome the flame advance. My jet was 3/4" from pipe inlet, Rupert Wenig's was 5/8" but some of R. Reil's were as much as the full length of the reducer 1 3/4" . I removed the T and jet and went with a straight pipe with a #53 jet drilled in it. After some fiddling to center it down the burner pipe, distance to burner pipe now 1 1/4". Lit on first try and did not retreat into the pipe as I ramped it up.

Continued firing the furnace, The last heat of the evening the lining had long stopped steaming, took it to a red heat as in second pic. below.

Added two grease fittings to main lift slides.

The Furnace is finished and ready for a paint job. The frame assembly is Armour Coat gloss rust paint. the furnace shell is Tremclad high heat flat black and the lid is a spray can of flame resistant paint. Here's the pictures.

So thats it for the furnace build but there is lots more to do before I can start casting. In part 2 I'll cover the waste oil tank build, propane installation, mold bench, mold flasks, pouring shanks, green sand mixing and molding. Then we will do some casting and test the furnace performance.

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