Felgiebel 16,6

[F-DS]

Mold drying

 

[F-DS]

I cast the crankcase of my engine. I heated the mold with a hot air gun before casting, the casting was better than I expected, I am satisfied with this casting. I photographed both castings, for comparison.
During the casting, I had a small accident, I made a product to increase the hydrostatic pressure in the mold to improve its run-in, but the aluminum spilled instead of the exhaust hole out of the side.

 

[Rudirk]

Hallo, the part looks really better. I think you could use it for machining your engine.

 

[William May]

Truly, all that matters is what is left after machining, and it looks like you have a good surface finish on all the areas that WON"T be machined, so you are good to go. Looks like an excellent casting!
To avoid "side-flow" where the metal comes out the split line of the mold, I usually cut a small step around all the edges of the lower mold, then ram the upper mold. The result is what I call a "seal-mold" where the metal is better contained.
This is a common problem, and depending on the casting, may not even matter. If your mold is all on one half of the mold box, and if that half is the lower one, then even if you do get some side-flow, the mold still filled, and the casting will be OK.
You did a nice job on the lettering, also!

 

[William May]

I just looked at the equipment you are using to cast! (I hadn't looked at the small pics before). You didn't just do a GOOD job, you did a MAGNIFICENT job. Turning out good castings with good equipment is expected. But turning out good castings with a backyard makeshift foundry furnace like yours is an awesome accomplishment. And you even used lettering! I am VERY impressed! I would say that when you get better equipment, you will have no trouble turning out excellent castings!
Maybe you should do a section in here, about casting on a very minimum equipment and cost level. That might start a LOT of new people making castings!

 

[F-DS]

Thank you for the compliment, I'm still amazed at how the casting went. The casting section sounds like an interesting idea. Since the casting has no defects, I will use it on my engine.

 

[F-DS]

When it doesn't work
I started turning the crankcase, after an hour of machining, when I was parting the rear cover, my casting cracked. The quarry shows how the casting is porous and inhomogeneous, the shape of the casting is not everything, I have to go back to the "drawing board" and come up with another solution for the casting.

 

[F-DS]

I made a piston, the clearance of the piston rings is 0.07 mm.

 

[Peter Twissell]

Shame about the casting cracking after all your excellent work in mould making and pouring.
What was the material used for the casting?

 

[William May]

When it doesn't work
I started turning the crankcase, after an hour of machining, when I was parting the rear cover, my casting cracked. The quarry shows how the casting is porous and inhomogeneous, the shape of the casting is not everything, I have to go back to the "drawing board" and come up with another solution for the casting.

View attachment 116674

Sorry to hear about that! If you send me your address in a PM, I will send you a couple of "Degassing Discs" for aluminum, no charge.. I applaud your efforts at casting, with minimal equipment, and I am sure your posts on here are a real eye-opener to many who have thought about doing some small castings, but have been hesitant. With the amount you cast, that will last you for 10 castings, easily. I have a box full, and I only use a part of one disc for a full #8 crucible of aluminum. It is a proprietary disc that looks like a laundry soap tablet. You drop it in, AFTER you have removed the aluminum pot from the fire for pouring, and then submerge it in the aluminum with a stainless steel poker or cone. (I use a cone, with holes in it. You press it under the surface of the molten aluminum, and it starts to bubble and release gases.) These remove the oxygen from the molten aluminum, slag our the impurities, and you can then skim them off and do your pour. it is only a 30 second operation, the last before you pour the molds. You will be amazed at how much crap suddenly appears on the top of the metal. Then you use a tool with a ledge on it to skim the aluminum, and you are left with a nice, shiny pot of metal. Then you pour, and you get a lot better castings, even with the minimal equipment you work with. THE ONLY THING IS THAT THE GAS GENERATED AS IT BUBBLES IS POISONOUS! YOU DO NOT WANT TO BREATHE IT, SO STAY UPWIND OF THE METAL POT WHILE DE-GASSING.

 

[ixb1]

Ahoj F-DS
Did you saw this Felgiebel build thread?Just for inspiration.
https://www.homemodelenginemachinist.com/threads/building-the-felgiebel.27541/

 

[Mechanicboy]

Molding mistakes made by yourself: Never interrupt while pouring floating aluminum into the mold in the meantime.

When you stop pouring floating aluminum, the first part of the aluminum cools before pouring the floating aluminum again until the mold is completely filled. The reason is that the cooled aluminum will never be bonded with floating aluminum.

When pouring aluminum into the mold, keep pouring until the aluminum starts to solidify or there will only be gas blisters and shrunken aluminum that will not cover in all places in the mold.

Keep the mold as dry as possible without developing steam during molding. I am using cast sand mixed by 80% sand which has 0.5-0.6 mm grain size mixed with 20% clay.

 

[TimTaylor]

Did you use a cover flux? It will reduce the dross and minimize hydrogen absorption from the atmosphere.

 

[Mechanicboy]

Did you use a cover flux? It will reduce the dross and minimize hydrogen absorption from the atmosphere.

I never used flux in aluminium, remove slag and degassing the aluminium before pouring only. The aluminium came from old engine parts. Se at my products of cast aluminium and own made model engines.

 

[TimTaylor]

I never used flux in aluminium, remove slag and degassing the aluminium before pouring only. The aluminium came from old engine parts. Se at my products of cast aluminium and own made model engines.

Very nice work!

The reason I asked is that from the picture, it looks like the OP's casting failed due to a porosity issue. Usually this is caused by absorption of hydrogen gas from the atmosphere that is released as bubbles as the aluminum cools. Lengthy exposure time to the atmosphere and excessive superheat of the molten metal are major contributing factors. A cover flux, which is basically a salt compound, will minimize absorption. A drossing flux will separate usable aluminum (as much as 80%) from the dross. Degassing can be done chemically or mechanically. Most chemical degassing agents are chlorine or fluorine based, and as William May said earlier, the fumes generated are quite hazardous. A much safer alternative that works pretty well is sodium carbonate. It's pretty cheap in granular form and non hazardous. You simply put about a table spoon in a piece of aluminum foil and roll it into a tight packet, then use a clean steel rod to push it to the bottom of the crucible of molten aluminum and hold it there until the bubbling stops and the foil is melted. Scrape the dross & pour...

I learned metal casting in a foundry class years ago in high school, and we were taught to use fluxes, so that's what I have always done. We poured aluminum on a daily basis and brass or bronze about once a week. Once every couple of months we'd set up the cupola furnace and do a cast iron pour.....

 

[Mechanicboy]

Tim Taylor, I'ts new for me to use sodium carbonate as flux. Thanks you for information.

 

[F-DS]

The problem with casting was not the interruption of aluminum casting that would cause its incoherence, but the fact that I added 1/3 of the aluminum from the car pistons to the batch. The pistons contain a high% of silicon, which was supposed to guarantee the strength of the crankcase, but apparently its presence caused just a rough structure and fragility. I believe that the pistons are cast under different conditions than what I achieve in the home environment and therefore the material does not behave as it should.

 

[F-DS]

Today I cast another crankcase casting, this time I used a different 3-part mold, of which the first two parts are screwed together, so that the aluminum could not separate them from each other and spilled sideways. 3 parts of the mold form a chimney into which the metal is poured. I used the same one last time. I wiped all the joints of the mold for the circuit breaker with water glass mixed with sand, so that the aluminum could not flow out of the mold other than through the vent hole. I had a good feeling from the mold, it had a perfect shape and it was already quite level, the problem was again moisture, which caused me to continue to cast the crankcase. (more on photo)

Now I will focus on further machining of the crankshaft, casting has been enough so far.

 

[F-DS]

Note that the inlet and vent channels are quite well cast, probably also due to the poorly chosen material from which the mold is made. It already contains too much clay.

I used two types of molding compounds for the production of the mold, a compound with a rougher structure was used for the part with the channels, which does not create a smooth surface, but dries well and does not retain moisture in it.

 

[F-DS]