My Casting Blunders and Successes

[PatJParticipant @patj87806]

Using my standard "bull-in-a-china-shop" approach to learning metal casting, I continued onwards and upwards (downwards?).

I was introduced to resin-bound sand by the art-iron folks, and it looked very versatile, and worked well with iron, so I decided to try that.

I was not familiar with how to lay out patterns in flasks, and so I made one giant flask, with a very long runner.

This was yet another of many blunders.

I was able to use a few parts from this flask layout, but generally in every attempt, the metal froze before it went very far down the long runner.

This pour used my original heavy-mass furnace (don't build your furnace with a heavy mass), my original siphon-nozzle burner, diesel, and I think perhaps a shop vac output for combustion air.

Results:

I think the only usable casting I made with this pour was the flywheel.

The other castings were either partially filled, or hard as tool steel.

I was not aware that ferrosilicon needed to be added to thin gray iron castings for machinability when I made these castings. 

I still did not know how to tune an oil burner, and so it was strickly guesswork at this point.

All of these castings were for the green twin oscillator that I was building.

Again, the tall sprue and risers were totally unnecessary.

Safety Note:

Never operate a furnace near the house/garage like I did.  I cringe sometimes looking back at these old photos of the early days.

Edited By PatJ on 03/07/2022 16:27:16

Edited By PatJ on 03/07/2022 16:28:16

[PatJParticipant @patj87806]

Here are the casting results from the above iron pour.

The flywheel casting turned out perfectly, but the remainder of the castings were dreadful, and unusable.

I discovered the alloy "nocutium", which is slang for thin gray iron without ferrosilicon added, that cannot be cut even with a carbide bit. It is basically gray iron that solidifies like tool steel before the graphite has time to disperse in the casting.

I took off all the teeth on a new Portaband saw blade trying to cut the chilled iron, and that was definitely a "what-the-flock" moment.

Any of these castings that were over about 3/4" thick did not need ferrosilicon for machinability, and any parts thinner than about 3/4" thick were un-machinable.

 

 

 

 

Edited By PatJ on 03/07/2022 16:45:35

[PatJParticipant @patj87806]

The 3D printed patterns for the green twin flywheel were printed at a commercial business, and were a bit on the fragile side.

I decided to make permanent metal patterns for them, using red brass.

The mold was sodium silicate I think.

The furnace was a small stacked insulating fire brick affair, that disintegrated the very first time I used it with an oil burner.

This melt used a naturally aspirated propane burner.

Results: Failure. The melt was too cold, and so the mold did not fully fill.

I was not versed on riser size or location either at the time, and so everything was guesswork.

Did not seem to be as much gas in the red brass as there was in the yellow brass.

One more addition to the cluttered "casting failure wall of shame" collection.

Safety Note:

Once again, don't operate a furnace anywhere near a house, and not near anything plastic either.

Don't do dumb stuff like I did in the beginning.

[PatJParticipant @patj87806]

New burner design, poor furnace lid lifter design.

I attempted to cast the green twin base in iron on this attempt.

I was under the impression that if a medium-sized oil burner was good, then a BIG oil burner must be much better.

This was a very bad assumption.

The combustion air blower was a sawdust collector blower, and the burner nozzle was a 4" diameter steel pipe with two siphon nozzles inside of it. The design was experimental, and so I used some PVC pipe for some of the burner tube. For a permanent burner design, one would not want to use any PVC.

As usual, I stumbled blindly ahead, still being totally ignorant of combustion dynamics as related to a foundry furnace.

My first iron furnace was also a bumbling affair, with an extremely high mass, a lid that was 5 times too thick, and a lid lifter vertical shaft that was supported by a band around the top of the refractory.

Multiple blunders.

The refractory expanded when it got hot, causing the band to slip and rotate, binding the lid lifter, and jamming the lid open just enough to prevent removing the crucible.

This was a miserable and bitter failure for me, and I lost a good Morgan B30 crucible as a result.

Good thing I was determined to learn iron or die trying, else this experience would have finished my desire to learn how to cast gray iron.

Luckily the mold was untouched, and so could be reused.

I was making progress though, and the resin-bound mold was a very nice design.

You can see a pouring cart that I made by adding wheels to a pouring shank.

I have gotten a lot of comments about how the wheels should have rubber tires on them, not bare metal rims, but if you have ever run a foundry, you would understand why you don't want rubber or plastic anywhere near a hot furnace or crucible.

Lessons Learned:

A small well tuned oil burner operates much hotter than an oil burner and combustion blower that is sized too large for a given furnace, such as the burner used during this melt.  This huge burner ran much cooler than my much smaller first oil burner.

I also notice that I had discovered ceramic filters, and was trying one of those with this melt.

Since I did not know how to tune my oil burner at the time, my iron was not hot enough to flow through a filter like this.  I have since redesigned my runner system so that I do not need a filter (more on that later).

 

Edited By PatJ on 03/07/2022 17:29:08

[PatJParticipant @patj87806]

Here is round #2 with the same mold.

Resin molds will keep for perhaps 30 days or more if you keep them dry.

Result:

I dropped back to using aluminum, and the result was a very decent aluminum base casting.

There is a bit of flash on the nose of the casting, which was a result of the bound sand chipping off at that location when I pulled the pattern. This type of flash defect is not a problem, since you can just grind it off.

I used two runners, and two gates that were somewhat wide and thin.

This arrangement worked well.

The mold is down-filled, which is against one of John Campbell's 10 rules (no waterfall fills).

I think I used an upwards fill for later castings of this piece.

I used small holes in the high points of the cope mold, to vent off air that gets trapped in the mold.

Many will tell you vent holes are not necessary since the sand will absorb any air, but resin molds need vents since they really don't pass the air, and you will get a large trapped air bubble defect if you don't vent the high spots of the mold.

Edited By PatJ on 03/07/2022 17:41:11

[PatJParticipant @patj87806]

Here is another aluminum 356 green twin base casting attempt.

I recall initially purchasing an inexpensive pyrometer to use with aluminum, and It seems like at some point it stopped working.

I don't see a pyrometer in use for this melt, and so I have to guess that I did not use one.

Results:

Another pour too cold, with partial mold fill, and lines where the two molten metal wave fronts began to solidify before they met.

 

Edited By PatJ on 03/07/2022 18:47:44

[PatJParticipant @patj87806]

Another aluminum 356 green twin base casting.

Result:

Success but with a few air bubble defects caused by failing to vent the high points of the mold.

I purchased a MIFCO aluminum/bronze pyrometer, and used it for this pour, and so my pour temperature was exactly correct (1,350 F). I was still using a welded steel crucible, which is said to contaminate aluminum melts to some extent (probably not significantly).

I added the adjustable damper to the combustion blower intake, to control the amount of combustion air entering the furnace.

I was still using the very oversized burner.

I started using a pan to catch metal spills.

 

Edited By PatJ on 03/07/2022 19:25:33

[PatJParticipant @patj87806]

Here was another use of the too long runner layout, this time with aluminum 356.

I intended to make a permanent metal flywheel pattern half, and so I left off half of the flywheel pattern for these castings.

Results:

I got quite a few usable parts out of this melt, but the runner is about twice too long, and I don't think I used this flask layout again.

I decided to continue this build in aluminum, since I did not have a solution for the chilled thin iron parts yet (I had not yet discovered ferrosilicon).

I was getting pretty decent surface finish at a 1,350 F pour temperature.

This was before I discovered ceramic mold coat.

Edited By PatJ on 03/07/2022 19:35:40

[PatJParticipant @patj87806]

I got the wise idea I would temper the aluminum bases to an approximate T6 level, and so I bought a pottery kiln that did not have an automatic regulator on it.

I cracked the lid to maintain the internal temperature while the aluminum parts were being tempered, and the radiant heat from the elements melted the sides of my two green twin bases.

The remainder of the parts did survive the tempering process (which is close to the melting point of aluminum), and they were noticeably less gummy than untempered aluminum 356 castings.

Sort of a story of three steps forward, and two back, but I was learning with every mistake.

A T6 temper is a two-step process, with a higher temperature step, water quench, and then a lower temperature step.

Results:

I was pleased with the approximate T6 temper on aluminum 356.

I am adding an automatic temperature regulator to the kiln.

The good thing about casting your own engine parts is that if you don't succeed, you can just cut them up and remelt them again, so you basically have a relatively infinite number of chances to get it right.

 

Edited By PatJ on 03/07/2022 19:49:09

[PatJParticipant @patj87806]

I cast two more bases in 356 aluminum, and each turned out perfect.

Results:

Success, and it all seemed easier and more routine at this point.

No problems at all.

[PatJParticipant @patj87806]

Some commercial furnaces have dual burners, with burner tubes located 180 degrees apart.

I decided to try this arrangement, but unfortunately I still had no idea how to tune foundry burners, so I was unable to determine if this burner arrangement worked faster/better than a single burner.

The velocity of the combustion air with dual burners is reduced by 1/2, and so the flame produced by two burners is much more even, and the flames begin lower in the furnace.

I discovered ferrosilicon, and so I cast some ingots in gray iron.

The cut and broken small ingots appeared free of chill, or hard white spots.

This was my 4th iron pour, and I was not yet comfortable with pouring iron.

I didn't know how much ferrosilicon to added to the melt, and too much ferrosilicon causes excessive shrinkage and sometimes hot tears.

And I learned that you do not need to clean scrap iron before you melt it.  A buddy of mine demonstrated melting scrape iron that had perhaps 1/2" of heavy corrosion on the surface, and he made perfect castings with it.

If the ingot molds are cleaned, the iron will stick to them, and thus the reason to allow your ingot molds to rust.

If the ingot molds are not preheated in the furnace exhaust stream to about 600F prior to pouring ingots, the slight residual moisture on the surface of the molds will flash as you pour the iron, and the iron will explode out of the mold (don't ask me how I know this).

 

Edited By PatJ on 04/07/2022 09:21:41

[PatJParticipant @patj87806]

Having acquired ferrosilicon, I decided to try casting a pair of green twin cylinders in iron again.

This time I made a pair of molds (I only had one cylinder pattern) and I cemented the two molds together.

I used a ceramic filter, thinking that a filter was needed to control any slag that may be in the melt.

The melt was not hot enough to flow through the filter for long enough to completely fill the mold.

Result: Failed castings. The filter was not flowing enough metal at my pour temperature.

I was beginning to wonder if I would ever be able to troubleshoot the iron process well enough to allow me to consistently make gray iron castings.

[PatJParticipant @patj87806]

I built a lift-out crane for use with the B30 cruicible, and a pouring cart.

The crane and the cart worked well, but the crane really needs to be secured to the concrete, or have a wide base on it to make it more stable.

A B30 can hold about 80 lbs iron, which is difficult to lift and pour by hand.

I tried another iron pour with the cylinders, but the filter was just not working.

I was time to try a different approach, and eliminate the filter.

[PatJParticipant @patj87806]

I had quite a lot of salvaged Naval Bronze boat shaft, and so I decided to try and cast a pair of cylinders in this material.

Results:

Fail. I forgot to weight the top of the mold, and I thought the thin cement joint on the sides of the mold halves would hold things together. The mold split open, and the cope drained out.

I later found out that the stiction with this metal is so high that it would have had to have been sleeved or something.

I was beginning to wonder exactly how many different ways I would discover to make a failed casting.

I had gotten too far into this engine build to turn back now, so it was just a matter of weathering the storms, and hope for better luck as I learned the process.

I must admit things were looking a bit grim at this point.

Edited By PatJ on 04/07/2022 10:04:08

[PatJParticipant @patj87806]

I cast another set of cylinders in 356 aluminum, and even though I was using commercial mold alignment buttons, I got a misalignment on these cylinders that was just enough to be very annoying.

I did not want to learn how to make misaligned castings, but rather make castings with no defects, and so I stopped using the alignment buttons, and started carving out two divots in the drag mold, in opposite corners, and let the cope mold fill these divots, thus creating exact alignment buttons.

I welded handles onto the ingot molds, so I could easily place then in the furnace exhaust stream, to drive off residual moisture, and avoid having molten metal pop out of the mold.

An ingot mold that looks dry actually has a tiny amount of residual surface moisture on it, and that moisture has to be driven off by heating the mold in the exhaust stream.

Results:

Fail. I could not live with 1/8" misalignment of the mold halves, although these cylinders could have perhaps been salvaged. The went back into the scrap heap.

I did keep records of the total melt weight, so as to not come up short during a pour.

I think this was the last pour where I used the welded steel crucible.

From this point forward, all my melts used Morgan Slamander Super crucibles, with separate crucibles dedicated to each metal type.

Edited By PatJ on 04/07/2022 10:26:45

[noel shelleyParticipant @noelshelley55608]

Good Morning Pat, Copper alloys have a great affinity for Oxygen ! There are 2 ways to deal with this A, remove it with deoxidising cartridges at the end of the melt or B, stop it getting in in the first place. I have used both but B is simple, firstly the furnace atmosphere need to have little or no free oxygen and then since carbon also love oxygen, at the start of the melt place a small amount of crushed pea sized charcoal in the bottom of the crucible along with a few small bits of metal. DO NOT fill the crucible. start the melt and as the metal melts, feed into the molten pool more metal, pre heating in the exhaust flame. This will hold the temp down to just above melting. Once you have enough metal melted then take up to super heat (pour temp), lift out skim and pour, QUICKLY. . The thermal lag on the crucible will see the matal gain 20* after checking temp and NEVER with brass exceed 1050*c. A very simple gate cutter is a beer can cut open as a strip say 6" long and 3" wide bent into an S top and bottom radiuses different, much easier than making gating patterns. Brass will almost always fume, the boiling temp zinc is only 907*c, I need say no more ! Noel.

[PatJParticipant @patj87806]

I decided to step back and rethink my mold layouts, to get away from a long single linear runner.

I went with a radial approach, with a large sprue in the center, and I think I eliminated the filter.

I needed to start making some serious progress on this engine build (two sets of castings were made, and ultimately two engines built, one by me and one by my Canadian buddy).

It was time to find a method that worked well every time.

I made five back-to-back aluminum castings in a short period of time, perhaps 1.5 hours, and all were successful.

Result:

Total success with 5 back-to-back aluminum pours.

Edited By PatJ on 04/07/2022 10:39:59

[PatJParticipant @patj87806]

I was finally starting to feel comfortable with the aluminum 356 casting process, and reached the point where I could easily and repeatedly make quality castings.

I as you can see from all the previous attempts, there was definitely a learning curve to be dealt with.

I finished out the remaining green twin castings, and made a few spares, since my machining work needed improvement too.

Results:

Total success.

Edited By PatJ on 04/07/2022 10:43:37

[PatJParticipant @patj87806]

Then it was onto cleaning up the castings, machining, painting, assembly, and finally after much grief, running the complete engine.

This build was not so much about making an engine, but rather mastering the casting process, and I made a lot of progress by casting this engine.

Edited By PatJ on 04/07/2022 10:52:19

[PatJParticipant @patj87806]

I had originally intended to cast the entire green twin engine in gray iron, but was only successful in casting the flywheel in iron.

It was time to go back and revisit the entire iron melting process, and figure out how to cast any part in iron, regardless of whether it was thick or thin.

The next step for me was to build a new lower-mass iron furnace, and once and for all figure out exactly how to tune an oil burner to achieve maximum heat inside the furnace.

.

[EmgeeParticipant @emgee]

PatJ

That's a really good achievement to produce all the castings and then complete the machining to what appears to be a very high standard on an attractive looking engine, congratulations.

Emgee

[Richard MillingtonParticipant @richardmillington63972]

Thank you for taking the time to post this. It has been a really interesting and informative read.

[Jon LawesParticipant @jonlawes51698]

Now THIS is model engineering. You should serialise it in Model Engineer!

Superb work.

[PatJParticipant @patj87806]

Thanks all for the very kind words.  All I had to use for the green twin build was three photos of the full size engine.

It was very difficult to learn the foundry hobby, but I suppose had it all been easy, I would not appreciate it nearly as much.  I guess this is a good illustration of what someone's castings look like when you first begin to cast metal, and then shows a progression of what can be achieved over time. 

I would really like to build an IC engine next, and the one I have my eye on is a single-cylinder Frisco Standard marine engine.

I have started the 3D work on it, and Jason B and others here have actually contributed the helical gear design in 3D.

Here are some 3D screencaptures.

I am pondering how to make the cores for the cylinder head, and have that about 1/2 figured out.

 

 

Edited By PatJ on 04/07/2022 15:18:32

Edited By PatJ on 04/07/2022 15:20:35

[LukerParticipant @luker]

Enjoyed this thread! Also read one or two parts of your write-up in Live steam on this little engine, looks fantastic!

[Author]

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