Happy New Year, Foundrymen!

Discussion in 'General foundry chat' started by 0maha, Dec 30, 2022.

  1. 0maha

    0maha Silver

    I've gotten a lot of invaluable advice from this forum over the last few years, and thought I should pop in and say hello and give an update.

    My interest in metal casting started a few years ago when I had the idea of making custom derby covers for Harley Davidson motorcycles. It's been quite a process, with multiple, overlapping learning curves, but I'm finally to the point where I'm getting results like this:

    [​IMG]


    There have been quite a few dead ends and changes of direction along the way. For example, when I first started, I assumed I'd want to use block method + vacuum assist for the investment, thinking that would be necessary to get the surface detail I wanted. After a bunch of effort, I never got my success rate over 50%, so I decided to try switching to shell. Turns out shell was the way to go all along. It is SO much easier, uses way less investment material, and is just easier all around.

    My basic process goes like this:

    1) I Create the basic part in Fusion360.
    2) The Fusion360 model gets saved as an STL file, then imported into ZBrush
    3) I use ZBrush to do all the sculptural design work
    4) The resulting model gets 3D printed on my Phrozen Transform:

    [​IMG]

    5) I give the print a good going over, sanding away the layer lines and such. Any areas I intend to finish to a high polish get sanded down to 1000 grit. Anything else gets sanded to 400.
    6) I make a two part rubber mold from the print. I have a guy with a CNC router that cuts MDF frames for me that I use to give the molds some structure.

    [​IMG]

    7) Once the mold is ready, I make a wax pattern (I use Limerick from R&R)

    [​IMG]

    8) I've gone through a bunch (well, seven) of designs for my gates and sprues. That was probably the hardest part of all this. In the end, I came up with this:

    [​IMG]

    The name of the game was to get the bronze into the molds while maintaining laminar flow. The main sprue with an asymptotic taper feeding into the J-gates at the bottom seemed to do the trick.

    Out of time for the moment. I'll pick this up next week. In the mean time, if anyone is interested, I've got a website at https://omahaderbycovers.com. If you scroll to the bottom of the home page, there's a video that shows more of the process (and you can see what the sprues looked like a couple of generations ago).

    Thanks again for all the help I've received over the years. Much appreciation!

    Happy New Year!
     
    Chazza, BattyZ, Rocketman and 4 others like this.
  2. rocco

    rocco Silver

    Looks like you've perfected your process, those look amazing!!
    Happy New Year!
     
  3. Petee716

    Petee716 Gold Banner Member

    Happy New Year!
    First rate work Omaha!

    Pete
     
  4. FishbonzWV

    FishbonzWV Silver Banner Member

    Beautiful work Omaha!
    Your website is also first rate.
    Bon voyage in your endeavor.
     
  5. Tobho Mott

    Tobho Mott Gold Banner Member

    Wow, those are nice!

    Happy new years, all.

    Jeff
     
  6. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Those are very nicely crafted Omaha. I must confess, I didn't know what a Derby cover was until I searched it. Interesting name for an engine part and bigger than I thought too, maybe 6-7 inches in diameter?

    Derby Cover 1.jpg

    Have a Happy New Year and thanks for the post.

    Best,
    Kelly
     
    0maha likes this.
  7. 0maha

    0maha Silver

    Exactly right. From 1970 to today, Harley Davidson has produced six different derby cover sizes. (Much to my chagrin, since each variation makes my life that much harder). The smallest are just over 6" in diameter. The largest is 7.75".

    (If you're interested in all the details, I've got all the sizes listed here.)

    Continuing my story...

    The transition from block to shell brought with it the biggest change of all. I partnered up with a local art foundry and do all the hot work there.

    [​IMG]

    The process is pretty straightforward: I make all the waxes in my shop, then take them down to the foundry and start dipping. We use the standard R&R investment and silica sand stuff, and each wax gets six layers + sand, followed by a seventh seal coat layer.

    The foundry has a big, natural gas fired burn out oven we use to dewax the shells. Here's a YouTube video that shows the setup.

    Back to the various sizes: When I first started this project, in my ignorance, I assumed I could directly cast these things. As it turns out, some of them are so complex (on the back side, that is) that there is no way of making them other than to CNC machine them.

    Thanks to pure dumb luck, I have a son in law who's next door neighbor has a complete CNC shop in his garage. He's been instrumental in helping me get this all sorted out.

    Back to work...more later.
     
    Rocketman likes this.
  8. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Few people have an appreciation of what takes to make things like this......if you have done it or do it, you know! -Keep up the good work.

    Best,
    Kelly
     

Share This Page