Sunday, February 15, 2015

The Foundry: Oil Tank Redemption and Controlled Burn

After the tragic outcome of the previous foundry session, a few things needed to be fixed before we could fire it up again.

Act 1 - New Wheels
Since the original furnace wheels got lit and completely melted, we decided it would be wise to make new ones out of steel.  We couldn't just let the furnace sit there without wheels either because it would cause a height difference between the blower and the furnace inlet.  I went to work turning the new wheels out of some 3" scrap.
Turning a new steel furnace wheel in the lathe

Here is the furnace with the new wheels installed.
wheels of steel installed on the furnace
These new wheels are so fresh and shiny!  Lil Rob's 13" Daytons can't compete with these!  Below in the picture is a chunk of what used to be the original wheel.
new wheel compared with old one
Act 2 - Funnel Upgrade
The funnel I built for filling the oil tank worked well last time, however I thought it would be even better if the filtering screen were built into the funnel itself.  This way, there is no danger of particles going around the screen and falling into the tank.  I also made it more leak-proof than before by using a scrap bicycle tube to make two layers of gasket, and sandwiching the screen in between.  The screen also has the holes for the screws to go through, so it won't move.
funnel using bicycle tube as gasket
Afterwards, bolting on the pipe flange.  This threads directly onto the tank for easy filling.
pipe flange to attach funnel
Here is the funnel in action.  I was able to pour lots of oil into the can and let the screen do its job.  The leaking was even more minimal than before.  When pouring in so much oil at once, I had to unscrew the plug in the tank to the right to allow air to escape, otherwise it would be airtight and the oil would not flow in.  The oil this time was from a Chinese restaurant, and was much less viscous and cleaner than the fast food oil from last time.  The screen caught only a few bits of fried egg that were in the oil.
funnel in use on tank
Act 3 - Tank Pressure
I decided the oil tank would be pressurized by a bicycle pump instead of compressed air because of what happened last time.  I did, however, make a tire hose adaptor for the compressed air so we could quickly add the initial pressure, or in case we broke the pump.
pressurizing the tank with a bicycle pump
The bicycle pump connects to the original manifold that came with the air tank.  It was designed to be filled up with a tire hose, so you could just go to the gas station and steal the free air (free in CA at least) and not actually need to own a compressor, pretty smart.  The outlet from this was originally hooked up to the tire hose in the previous picture, but since I don't want air to be going out, I just put a pressure gauge in its place.  This gauge is one I bought a while back for this purpose, and it only goes up to 15 PSI.  I just left the original pressure gauge there because it wasn't hurting anybody, and I didn't want to buy an 1/8" plug.  The original gauge reads up to 200 PSI which wouldn't be that useful for trying to gauge 5 PSI (my mistake last time, see below).  Also, here I have moved the oil shutoff valve from the burner to the tank.  I underestimated how much clearance I would need to screw on the ball valve, so I ended up needing that long pipe nipple to extend it out of the way, a minor inconvenience, except that I was going to use that nipple for extending the oil input on the burner.
the tank's air input
Two pressure gauges? That's ludicrous!
Here is the destroyed air regulator from the tank last time.  After taking a closer look at the gauge, I realized why it never read 5 PSI.  Each division on the dial is 4 PSI, and there are only 2 divisions below 20.  That means the lowest reading on this gauge is 12 PSI!!! So in terms of stuff I learned in chemistry class, when taking a measurement of 5 PSI there is always going to be a relative uncertainty of >100%!!!  I was so angry when I realized this, I wanted to melt the regulator in the foundry, but judging by the weight, it was probably a zinc alloy, and would not mix with the aluminum, and/or vaporize and become the equivalent of welding on several feet of galvanized steel on the lungs.
destroyed regulator dial
Act 4 - everything else that wasn't important enough for its own category
Here is the piece of oil hose that had the leak in it, we just cut it off and used the rest of the hose.  This shows how hot it got, as it somewhat molded itself around the hose barb and hose clamp.  It would probably be a good idea to eventually upgrade the hose to something less susceptible to melting.
melted hose
A lot of oil dripped out of the furnace last time and caught fire in the pan.  Upon inspecting it this time, there appeared to be a tar-like residue of the burnt oil.  One chunk of it felt like asphalt.  Refining long-chain hydrocarbons from vegetable oil? What else will we accidentally do next?
long chain hydrocarbons accidentally refined from vegetable oil
One of the great things about the oil spill, is now I know exactly where everything is supposed to go!
stained cement being useful
This part was rather important, we finally devised a method of securing the burner onto the blower pipe.  We welded a piece of metal with a tapped hole next to the slot, and clamped the pipes on with another chunk of metal.  Now the burner is aiming straight down the pipe, unlike last time when it was loose.
the new burner mount
Okay, now that everything has been dealt with, it's time to fire it up!
the setup all set up
Everything worked flawlessly.  We got a really nice controlled burn this time, it was actually burning rich for a large portion of the time.  There were no crazy huge flames coming out of the bottom and top like last time, so my face wasn't in danger of being melted.  We believe the increased fluidity of the new oil might have been the difference, or the burner being aligned straight in the tube.  Another thing I did was switch out the gauge on the atomization air regulator with the one from the destroyed regulator since the original one was defunct.  This time I could actually get a reading on how much compressed air was going into the burner.  The results were shocking, because I ran it as high as 80 PSI!!!  That was when we were thrashing, I still could maintain a nice mellow burn down around 20 PSI.
crucible and ingots after pouring
We got the metal nice and hot with the crucible glowing pink.  The soap dish mold was heated on the furnace for quite a while.  When it was time to pour, there was a bunch of charcoal in the crucible since we used a lot of wood when starting the furnace.  This made skimming take a bit longer.  Also, my poor pouring technique held up the process a bit.  It's a bit hard to pour with a hole in the thumb of the glove....
soap dish die casting mold after pouring
Anyways, enough excuses, we got 2/3 of a soap dish out of this one.  Not quite there yet, but this is the best one so far!  I think next time I will heat the mold while it is lying on its side, that way the heat will be more evenly distributed from top to bottom.  We did notice more imperfections in the casting, but this is from the mold being dirty with sawdust, oil, and rust since we left it out in the rain after it got "rained" on by oil....
another incomplete soap dish casting
If we cast another half soap dish, we could just weld them together!
A few steps up from the next best attempt.
the previous casting attempt
Conclusion:
I think this session finally marks the end to the experimental phase of the foundry (which only took 4 years).  It's time to do some REAL casting now!  Things still to be done are to get some molding sand and a crucible for melting iron, brass, or whatever else we can find.

CONTINUE TO PART 10 - MOLDING SAND

BACK TO PART 9 - Oil Tank Disaster

BACK TO FOUNDRY MAIN PAGE

1 comment:

  1. I'm glad you finally found it. Great info. so when are the new articles on how to actually spray the powder coat and the proper way to cure it followed by how to shoot 2 or more coats, coming up? Thanks. Bostitch

    ReplyDelete