"Hothead" Dual fuel Metal Melter (Part 2)

Continuing from part 1 of the furnace build this section covers most of the accessories necessary for the casting process and I will do some casting and test the furnace performance.

(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 I will start with the waste engine oil day tank. I used a discarded 20 lb. propane tank, the valve removed and the tank well flushed out before doing any work on it. The tank when in use will hang from my garage eave from a pulley and lift rope. The height will be 10' giving about 3 PSI at the burner (borrowed idea). the tank will be heated by a 300 watt KATS magnetic block heater (my idea). Temp. will be checked periodically with a laser pointer temp. gun. The oil discharge pipe extends 3" into the tank to act as a stand pipe and prevent the krud settling out of the oil from leaving the tank. The bottom of the oil level site tube is 1/4" above the top of the stand pipe indicating the need for a refill. The cap on the fill pipe has  a channel drilled from underneath to allow the tank to breath and prevent a vacuum. 

Here is the completed tank with hose, block heater and hanging bracket.

And hanging from the garage eave.

 My waste oil barrel the idea is that by doing the occasional oil fired melt I will never have to empty it.

Next I installed the propane system. I have a small propane powered generator that I want to use for short power outages so this was in the plans before I decided to build the furnace. I decided to go with 2- 30 lb. tanks for regular use since they will be easy to refill and a 100 lb. tank as back-up. 

The next picture is a dry lay-up of the propane fuel trane. The 2-6" iron nipples and elbows still need to be replaced with brass and stainless but the trane is complete. The 2 black quick connects, connect to the 2-30 lb. tanks and the yellow capped POL fitting connects to the 100 lb. tank. The yellow 3 way valve selects either the 100 lb. tank OR both 30 lb. tanks. The pressure reducers are rated 0-30 psi and 1-60 psi. The reason for 2 reducers? The dual fuel oil burner will never require more than 15 lb. but the atmospheric burner will require as much as 30 lb. or more. Either or both can be used if tank press. allows.

Here I have cut, welded and painted a stand for the propane piping. It will get bolted down to my propane tank pad.

In the next 2 pictures is the completed installation. 

Next we will start on some casting necessities. So to get started with casting I made a couple quick molding flasks and bottom boards. These are nothing special just 2 light weight 12" X 14" flasks made from 1 X 4" strapping held together with glue and drywall screws. The line markings on the alignment pins are to keep the boxes from getting turned around. As I start to do more complicated casting I will make better flasks.

Well you can't make molds without a molding bench, ha ha well you can but its a pain. Not alot of finess here, its made from construction grade lumber but its very heavy and very sturdy. The bin will hold over 200 lbs. of molding sand and the shelf can store 7-5 gallon pails for another 300+ lbs. The roll over bars slide out for access to the whole bin. 2 coats of Tremclad enamel and its ready for use.

First step, build 3 sections the leg frame, the sand bin and the shelf.

Ready for use.

So moving on to the pouring shanks, I need one for the clay graphite crucible and one for a 5 lb. capacity steal crucible that I still had left from when I played with casting many years ago.

A little side bar. Here is a picture of some stuff I still had from when I did some casting back in the 80's. From left to right a disk sander table, lost the motor but the table is still around. A steel crucible, some sprue patterns, a blow out bulb, some aluminum handle screwdrivers (the black handled one is similar to the one used for the pattern) and a mold rammer. 

So back to the pouring shanks. For the clay graphite crucible I modified a set of surplus oversized fireplace tongs I picked up for a song at Princess Auto, years ago for this purpose. After a lot of bending and filing and bending and welding I came up with this.

After some consideration I added a flat bar across the pouring lip to help skim the crud in an iron melt.

And some handle extensions for better pouring control.

Back in the 80's when I was running my little electric furnace I was using a large set of pliers to pull and pour the steel crucibles. Not the safest method. For this pouring shank I made a handle out of 1" pipe and welded steel rod to the end. I bent these rods to engage the sockets welded to the steel crucible. Works beautifully.

Next we will mix up some green sand for molding. To start I put together a pouring and green sand mixing box. It's just 2 X 4's with a 2' X 5' 20 guage galvanized sheet metal bottom. I can mix my green sand in it and when I pour it will get a couple of inches of sand in the bottom, set up tight to the furnace I can pour 3 molds comfortably. 

Mixed up 150 lbs. of molding sand, the formula from one of D. Gingery's books:

150 lbs of fine sand 75 mesh or better.
10% bentonite clay
1% wheat flour
1/2 gallon clean water

Stopped adding water when it still felt too dry and continued to mix a couple times over.Squeezed a hand full of sand it showed good detail and broke clean without too much crumbling.

The mix will need a little further adjusting but for now I moved the molding sand inside to the molding bench and covered with plastic to finish tempering. Should improve with time as the moisture permeates all of the clay and flour particles.

Ok we are ready to start casting and test the furnace performance. to begin I will start with the testing of the atmospheric burner. I liked the screwdriver handles I cast back in the 80's and they don't need patterns to make so I will cast more of those and I will throw in a saucer just for fun. Hopefully one day I will try the cup and saucer molding test.

This is the furnace set-up. Ready to fire up.

Safety equipment and PPE , a must.

The molds and ingot tray ready to pour. The steel pot is for skimming the dross into.

First Heat

Lit the furnace at 1:32, gas press. 20 psi and furnace cold.
1:38 initial charge melted, continued to add metal till pot 1/2" from lip. 
1:48 Pot full, checked temp. 1382*F, shut furnace down, skimmed melt,inserted shank and poured first mold remainder in ingot mold.
Melt time 16 min. from cold start.

Second Heat

Returned crucible to furnace recharged with aluminum.
2:03 Burner fired up, furnace hot, added aluminum to fill pot to 1/2" of lip again.
2:16 Pot full, checked temp. 1406*F, shut down burner, skimmed and poured.
Melt time from hot 13 minutes.

For 5 lbs the melt times are amazing. You barely have time to catch your breath before moving to the next step. The pouring shank worked like a champ, slide it in and the crucible becomes part of your arm. Very good control.

The patterns

Fresh from the shake out. 

Excess aluminum poured into ingots.

All cleaned up on the power wire wheel.

The products of both melts. The handles work great on small files as well.

In preperation for my next test, I tempered my clay graphite crucible. After placing in furnace I heated the furnace to 300*F then shut it down and let it sit closed up for 2 hrs. Fired it up again and slowly raised the temperature till the crucible was a bright red heat, shut it down and closed it up. I will let it sit overnight to cool down.

I also got the used green sand remixed and back into my mold bench. Made an adjustment of 2% clay and mixed it dryer. I am hoping for a little more green strength to reduce inclusions and I think I need to vent more and pour faster to reduce gas in the mold.

So to test the Dual Fuel Burner I will first light of on propane, I will melt a charge of aluminum on gas to heat up the furnace. After pouring off the steel crucible I will switch to the clay graphite crucible with a charge of soft iron scrap, light of on propane and slowly switch to waste oil as I ramp up the firing rate. Oil burns hotter than propane, which is good since iron pours between 2600*F and 2800*F. I did not use my K type thermocouple which only reads accurately to 2400*F, so eyeballed the pouring temp.,  looking for a dazzling white melt color.

For a first attempt with iron I will pour just an open mold of a 12 lb paper weight. Actually if it machines well it will make a nice little surface plate for model work.

The aluminum part if the pour, all bedded in, ready for the cope.

Here again the pouring set-up.

Safety equipment, note the extra heavy gauntlet gloves for the iron pour.

This burner performed as well as the atmospheric burner, a little slow on the oil but I think the needle valve for thick oil is a bottleneck. I will replace this valve with a gate valve since I still had half my fan capacity available with the needle valve wide open. Total oil used, a little over one gallon. Here are the melt times.

First Heat

1:23 Furnace cold, burner on with initial aluminum charge in steel pot, gas press. 10 psi.
1:30 Initial charge melted.
1:37 Crucible full, 5 lbs of aluminum, burner off, skimmed and poured.
Melt time from cold, 14 minutes.

Second Heat

1:46 Clay graphite crucible with 12 lbs iron, 2 oz. charcoal dust and 2 oz lime in furnace, burner on.
1:50 Started to slowly feed oil.
1:58 Gas off, oil wide open, fan damper 1/2 open.
2:55 Iron melt bright white, furnace shut down, skimmed and mold poured.
Melt time 1 hr. 9 min.. As noted earlier should be able to speed this up by increasing the oil delivered to the burner.

The iron pour still red hot.

The aluminum pour shake out.

The iron shake out. 

And here is everything all cleaned up. To verify that the iron was machinable soft iron I sliced one of the lips off on my bandsaw. Cut easily with no hard spots.

The furnace exceeded my expectations when I imagined the layout for this project. Cost was close to C$600 not including all the surplus and salvage I have collected over the years and the propane and piping system which would have been installed weather this furnace was built or not. 

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.

That said there is lots of joy and satisfaction in casting metal. Its hard to beat the feeling you get when you shake a new casting out of the sand. I consider it one of the more addictive of home hobby pursuits. 

Happy Casting

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