Miniature Tunnel Ram Intake

Discussion in 'Lost foam casting' started by Blue427, Dec 31, 2021.

  1. Blue427

    Blue427 Silver

    So the tunnel ram worked out well... 20220320_115004.jpg and I have a new part that I would like to cast on the rear of the engine 20220320_115015.jpg
  2. Blue427

    Blue427 Silver

    Attempting to make the bellhousing out of foam because I like the ribbing feature and the loft features. I don't have CNC 20220320_115026.jpg . Started by cutting two tangent circles and gluing together on the wire cutting table using a circle jig LHS ISO SB Bellhousing.png please help with how one might duplicate the ribbing. My ideas are: slice the part in segments and glue back together using thin sheets, or cut up tiny strips and glue on individually. Appreciate any comments
  3. Al2O3

    Al2O3 Administrator Staff Member

    For a one-off part and ribs that small, just cut straight strips and glue them on. You may need to take a razor knife and some sand paper to bevel and contour the edge that glues to the bell housing but those foam strips will be plenty flexible to conform to the bell. They can also be trimmed or sanded after installation. Then fillet them with wax where they interface with the bell.

  4. Blue427

    Blue427 Silver

    Thank you Kelly,
    I am pretty happy with the results so far. How should i gate this part? thumbnail.jpg
  5. Al2O3

    Al2O3 Administrator Staff Member

    Are you planning to make it hollow? If so, how are you planning to do so? What's the approximate diameter of the mounting flange?

  6. ESC

    ESC Silver

    Kelly, I believe it is hollow since it is installed over the brass flywheel, but that is just a guess.

    Blue, you seemed to have good luck with the forked sprue, so if I were doing this I would attach the sprue to
    the flange with the bell housing tilted down slightly to the rear so the interior gets a good sand fill. The face of the flange needs to be machined so the attachment point will disappear. Good Luck.

    Let's see what Kelly comes up with.
  7. Al2O3

    Al2O3 Administrator Staff Member

    Thought he might have removed the flywheel. Last picture of the pattern was just a solid.

    I'd cant it 30-45 degrees from vertical dish side up and gate into the top of the flange. I'd also make the tranny window/hole in the pattern so the sand inside the bell flows through and is supported by that through feature. You can fork the sprue and gate into the bottom too but probably not necessary on that small of a part.

  8. Blue427

    Blue427 Silver

    The wide end is approximately 3.5 inches and small end 2 inches. I removed the flywheel in the latest mockup photo. Its mostly solid, with just a 0.218 thru hole for the crankshaft. It is a protype and only constrained by mounting flange concentricity to shaft hole and looks. The plan is to start the engine using a needle roller clutch which is pressed into the brass flywheel. Behind the clutch is a 3/16 nyloc retaining nut. No starter bulge is needed.

    In the third photo you may be able to see an aluminum plate beneath the foam pattern. This plate provides thrust support for the cam shaft, connects the cooling passages for left and right cylinder banks, holds a oil seal for the crankshaft, and will be sandwiched between the block and the bell housing.
    I do like the idea of a clutch plate window to perhaps repurpose as a timing window, and scribe the flywheel to set ignition. I would machine that later, but may glue a rectangle where I imagine it to be. Also thinking it would be easier to bore the inside cavity after casting, mainly because I'm worried about shrinkage and an interrupted cut if I guess wrong or can't control the bore using foam.

    Knowing it's solid, do the above recommendations change? What are your thoughts on gluing a foam dowel on small end and feeding down only? The dowel would allow me to hold it in a four jaw chuck to set up accurately and machine the inside. The fin features would be facing up to permit sand to fill them easier. Is a 1 x 3 inch long dowel sufficient to feed using the foil funnel method?

    I sincerely appreciate the advice, and continue to enjoy reading and rereading the posts on this forum
    Tops likes this.
  9. Al2O3

    Al2O3 Administrator Staff Member

    At this point, you may as well cast it a completely solid. Small long holes are problematic. It's hard to coat and pack them. They end up incompletely cast and/or partially penetrated and/or filled with sand and will kill tooling during machining, on.

    I will always opt to machine foam instead of metal (so much easier) and prefer to cast near net shape as possible, leaving just adequate stock for more precision machining. Only exception is drilled holes. I cast those as solid and drill afterward. After all, it's why we cast.....right? As a lost foam caster, one must get their pattern making game up!

    Have you seen my pin router posts/videos? If not I can probably point you to them. Here's a trick for making circular profiles that I use on my pin router all the time.

    You can use your drill press as a pin router. Take a piece of MDF say 6x6 or 8x8 and drill a dowel hole (say 3/8") in the center of it. Add/glue some additional foam stock to the tranny end of the bell. Now glue the pattern to the MDF board centered on the dowel hole. Now take another piece of MDF about the size or slightly smaller than your drill press table and mount a dowel in the center. You can clamp the doweled board to the table and vary the distance between the dowel and drill press chuck center, and place your bell glued to board on this dowel. Then put a router bit of the desired shape (a round nose is good for contouring) in the chuck and select the maximum speed of your DP.

    You can use the depth stop and lock the quill at different depths and make circular cuts by spinning your mounted pattern on the dowel board. Then just vary the diameter and depth of cut until you achieve the desired profile. I usually clamp one corner of the dowel board and loosen the other clamp so I can swing the dowel board for +/- diameter of cut. This technique can be used for interior or exterior profiles. When done, just place the pattern board against the fence and hot wire the pattern off the board.

    It's a simple fixture that takes only minutes to make and you will use it over and over. You'll be pleasantly surprised at the accuracy and quality of result you can achieve. Mount one of those other slugs you made and use it as a practice part. You can even use a similar technique for non-circular profiles.

    I'd just cut the feature into the foam and cast it net shape. On one-off parts this small, pattern making is a bit artful, but I'd just add such features by hand, cut the opening with a razor knife, then shape it with an emery board. My wife keeps thinking she has misplaced her nail files, but they've actually made their way to my shop and have been cut down into small files for contouring such shapes. I have little sanding blocks with radiused corners. Just glue some sand paper to a piece of shaped wood

    Casting in features for machining set up and gripping is good practice. If you cast it as solid, yes just gate into the tranny end but I'd still position/cant it at an angle with the fins running vertically so flat back side isn't horizontal. It doesn't have to be round, but round will give you additional freedom in set up positioning.

    It's more than sufficient to cast. I've used a 1"D sprue to feed parts in the 5-10 lb range. In lost foam, many times, the sprue and gating design is as much about handling as it is feeding. I'd add addition length for added head pressure and additional depth of sand mold.

    DaveZ likes this.
  10. Blue427

    Blue427 Silver

    Used all the great tips including angle of sprue, wax fillets and was fortunate to have success on the first try.
    20220415_174142.jpg 20220416_102341.jpg
    PROSTOCKTOM likes this.
  11. Blue427

    Blue427 Silver

    Machining went well also because of the 1" spud cast into the back/top. I wasn't content with the flat mounting area, so hand filed it so the webs wrapped around and added a raised mounting pad for the imaginary Muncie 4-speed. This engine will be started (fingers crossed) using the removable tail shaft. Finished by very fine bead blasting. Very enjoyable process for one off parts.
    20220416_122811.jpg 20220417_124703.jpg 20220417_124725.jpg
    dtsh, FishbonzWV, Tobho Mott and 3 others like this.
  12. Al2O3

    Al2O3 Administrator Staff Member

    Looks good. Very nicely done Blue427.

  13. garyhlucas

    garyhlucas Silver

    I may be doing a sail drive adapter housing similar to this soon. Might have to destroy the current one in my sail boat to get the engine to let go of the drive. Fortunately I just changed jobs and have access to larger CNC milling machines
  14. Tops

    Tops Silver

    Gary, would love to see a thread on your saildrive repair.
  15. Blue427

    Blue427 Silver

    Just finished the engine, and it runs very well.
    Al2O3, Tops and DaveZ like this.
  16. DaveZ

    DaveZ Copper

    That is totally Awesome!!!!!!!!!!

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