Cast iron crank

Discussion in 'Pattern making' started by ESC, Oct 23, 2017.

  1. DavidF

    DavidF Administrator Staff Member Banner Member

    WOW! those cyl head cores look like a real challenge... (or nightmare) 13 pcs??
     
  2. ESC

    ESC Silver Banner Member

    Actually 19 pieces since I had to make the intake and exhaust cores in two pieces and glue them together so they would vent. The water jacket core is two pieces to draw from the corebox, and then the core that forms the combustion chamber that everything mounts to. It took a year to make the patterns and core boxes and multiple pours before I got two good castings. They are both on the engine still.
     
  3. DavidF

    DavidF Administrator Staff Member Banner Member

    Well worth the effort i would say... :D
     
  4. ESC

    ESC Silver Banner Member

    I've been working on the draft of the crank throws and then making the follower so I can ram a mold. The repro pours so tight it is like scraping in the entire pattern to get a decent release from it. I had to add nails on some of the deep throws in petrobond and it still wanted to pull so I rammed a linseed oil mold and then embedded that in a second flask. I didn't filter the sprue so I ended up with a small slag inclusion in the cope on one counterweight, but the rest looks good.
    Now back to work on the grinder to finish it.

    IMG_20171124_152145.jpg

    IMG_20171126_165042.jpg

    IMG_20171127_165520.jpg

    I shook the second out this morning and lost detail in the cope, still a saver but not as detailed as the first. I thought I needed shrink bobs and filling those in combination with smaller gates slowed the fill enough. It is nice soft iron. I took some of LuckyGen's advice and found some old cast iron to add to the radiator scrap.
    There are old ranch dumps in the area so I may go searching for some of the old cast iron that has been thrown away.
     
    Last edited: Nov 28, 2017
    Robert, DavidF, Tobho Mott and 2 others like this.
  5. ESC

    ESC Silver Banner Member

    There is more flash on the petrobond casting, but the detail is better with sharp edges. If the journals have enough material it won't affect operation other than perhaps not enough material to balance. It will be my learning crank.




    IMG_20171128_105925.jpg
     
  6. PatJ

    PatJ Silver

    Resin-bound sand would solve a lot of your problems,and it is designed for cast iron.
    It is tricky to find though.

    The cranks look good.
    That is a long path for the iron to run, but the fill is not bad at all.
     
  7. Ironsides

    Ironsides Silver

    I am following your crankshaft pours with great interest.

    I also have been wanting to do a crankshaft pour for years but put it of because the pattern can be a lot of work.

    Those deep pockets between the crankwebs would be difficult to pull out of the sand.

    What you will find is the old cast iron shrinks a lot less than the modern stuff so you can get way with less feeders and it be can soft to machine without ferrosilicon. Modern iron is made from steel so it chills very easily, that is why ferrosilicon is needed.

    Old cast iron was made from pig iron and could be melted many times over without chilling. The only thing to watch for is some of the old time foundries use to add steel to the pig iron and that chills easily. Engine blocks made in the 1930s can be bad for that ( Fordson tractor engines).
     
  8. ESC

    ESC Silver Banner Member

    The trade off is between the 300 hrs machining from the solid and patternmaking, moldmaking and pouring. I need to spend a little more time on the draft and finish. Then I think the deep pockets between the counterweights will pull. The crank poured with the linseed oil bonded mold, it just needs slightly larger gates and elimination of the shrink bobs. I believe they slowed the filling of the cope enough that the gate solidified. Size again, and there were no shrinks in the other casting so they are not needed. Kelly had offerred to make foam patterns that do not require draft, and since they would be poured vertically they are not subject to the same shrink defects. I still need to draw something up for him, mainly for the spacing and clocking. :)
    I expect the old cast iron has more total carbon, where the newer stuff with steel and carbon additive is close to the limit and then needs the ferrosilicon to force what carbon is available out in the thin sections I pour. I picked up 20 lbs of ferrophosphorous for some of my Indian heads. Anything to get a little additional fluidity at my best temperature will help. Thanks for that tip. I won't need it for the cranks since they filled well and the one concern is that it may make the cast iron a little more brittle.
     
  9. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I'm still game for that if/when you decide you want to pursue it and have time to detail the part features.

    Out of curiosity ESC, since you already have the running V8, why do you need more cranks? Still kicking around the idea of offering a kit?

    Best,
    Kelly
     
  10. ESC

    ESC Silver Banner Member

    I made the patterns for the cast iron engine with a double shrink and than poured a working pattern in aluminum so the engine would be a dead nuts 1/3 scale. I divide motor manual blueprint numbers by 3 and enter them in the DRO or CNC program and machine the part. When I had the idea to make a blower motor, I didn't want to modify the original because it runs too well to mess with. The reason for the double shrink was so I could make the same engine in aluminum and use all the same numbers for machining. This called for the working pattern to be cast from the other metal, in this case cast iron, and then the engine cast in aluminum from that pattern. I started to dabble in CNC with a Mach3 box and a Bridgeport mill converted run from it. A lot of this documentation was lost with the photobucket fiasco , but it was on AA. I have a block with caps ready for line bore, so I decided to make the crankshaft grinder and then thought I should have a cast crank and so it goes. I am exploring ways to speed up the build since I had about 4000 hrs in the first one, but do not see a kit in the future. But then, who knows?

    Blockandcapsonmill3-1.JPG
     
  11. Ironsides

    Ironsides Silver

    It can be a trade off when adding ferrophosphorous, too much and the casting is too brittle. Too little and the molten iron won't be fluid enough. To find out the right amount some experimenting is needed to find the barest minimum that will fill up a mould without making it too brittle. Have you tried those radiator castings for your indian heads?
     
  12. ESC

    ESC Silver Banner Member

    I didn't document my charges very well, but used a carbon additive and poured chill wedges to get machineable iron. I usually start with a heel of the radiator nuggets and then add ingot or sprues after I have molten iron. The main challenge was getting the temps above 2700* F to insure the fins filled.
     
  13. Ironsides

    Ironsides Silver

    What was the carbon additive you used?
     
  14. ESC

    ESC Silver Banner Member

    It is Desulco made by the Superior Graphite Company. I think the main use is for the electric furnaces where they are charging with steel scrap and then need to add the carbon to get cast iron.
     
  15. Ironsides

    Ironsides Silver

    I used to watch cast iron being made from steel in a induction furnace at a local college. They used petroleum coke to raise the carbon level to cast iron level. If you are melting a low carbon cast iron that would be a great way to get a higher carbon level. Really old cast iron has so much carbon so adding more carbon it will just float on the surface. It is like salt, you can add so much to water and no more will dissolve. Another interesting test you can do is after adding ferrosilicon use a steel stirring rod you will find that it will quickly dissolve to a sharp point. Steel that has a low carbon level will absorb very quickly carbon from molten cast iron. So many people think that they have really hot iron when that happens. To show that is not the case place a steel rod into the furnace but not into the crucible and you will find that it will take a long time to melt whereas in seconds steel will dissolve in molten cast iron.
     

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