48" Camelback Straightedge Pattern is in Process

Discussion in 'Pattern making' started by Melterskelter, Aug 14, 2019.

  1. Melterskelter

    Melterskelter Silver Banner Member

    Thanks, Charlie.

    It will be a reference flat for scraping machine ways.
    https://www.mmsonline.com/articles/the-art-and-science-of-hand-scraping
    Lightness and rigidity are important properties.


    Denis
     
  2. PatJ

    PatJ Silver Banner Member

    That is a pretty slick setup.
    As I recall, jhenise (Jeff, the motorcycle cylinder casting guy on AA) used threaded rods, which is a bit slow, but seemed to be accurate.
    I just use an automotive slide hammer at the center of the pattern, or sometimes in a few places on a larger pattern, with tiny blows to break the pattern bond first, and then a manual hand-lift.

    Thread:
    http://www.alloyavenue.com/vb/showt...torcycle-racing-cylinder&highlight=motorcycle

    Video:


    I think he ended up using sodium silicate bound sand, but he tried various sands and binders to find out which one he liked best.
    And I believe he uses the same sand that I do, which is OK85.

    .
     
  3. Chazza

    Chazza Copper

  4. garyhlucas

    garyhlucas Silver

    Your hydraulic lift is neat. McMaster Carr sells a commercial version for tables with a 6" stroke up to a 16" stroke with four cylinders. Actually pretty reasonable price too.

    In stock
    $576.13 Each
    47105T11
     
  5. Melterskelter

    Melterskelter Silver Banner Member


    Thanks, Gary.

    Looks like a nice unit for a table. BUT, (always the but) you can see in pics the cylinders are more than a foot long and they are powered from a single cylinder with a manifold(I think---not sure about this point). That manifold setup means the cylinders are free to move independently and rely on the table to keep them working in unison---not OK for my pattern draw where they all have to move lock-step. It would be possible to make major modifications to my bench so that they could be fit into place, but that would be a whole lot of work and then I would have to use three or four powering cylinders. (An enterprising person, to get around the height issue, might lay the cylinders prone and use a lever to translate their horizontal motion into vertical motion.) As they are, the little cylinders I drew up and made are very handy as they are shorter than my cope and drag flasks so I can just set them in place where they are needed, and because they are powered by their individual dedicated cylinders, they do move lock-step. Since I will be using them on various patterns, that ease in positioning is essential as is synchronized movement. They are not perfect, but they sure are sweet to use. I used them again today and made a nearly perfect draw of my patterns----a very difficult and risky task, for me anyway, when free-hand pulling those 48" long pattern pieces.


    Here is a video I made. I did have a little area of the outside edge (thank goodness not inside edge as I will just grind off the resulting small added metal bit) of the pattern. I think I did not talc that area very well. Will do better next time. But, this time, having learned a lesson the first time, I did position the cylinders closer to the ends of the pattern which pretty much eliminated the inclination of the pattern to rock on its long axis at the beginning of the draw. At the end of the video is a still that shows the mildly fractured edge on the outside of the pattern --- it extended about 4" in length and probably added 1/8 inch of metal in that area after I pressed the loosened sand more or less back into place. I am glad it was on the outside of the pattern as that will be easily fixed on the casting with a grinder in less than a minute.

    Next time I will talc better and do a better job of rapping the pattern loose before drawing it with the cylinders. I am still trying to sort out the nuances of the new tools.



    Hoping to melt some iron tomorrow.

    Denis
     
    Last edited: Oct 8, 2019
  6. Tobho Mott

    Tobho Mott Silver Banner Member

    Very cool. Wow, the nearest corner of the pattern really sprung out of the sand there! Was that near the broken sand?

    Jeff
     
  7. Melterskelter

    Melterskelter Silver Banner Member

    Yes, it was still not quite as free as I thought there. That sort of stickiness would have been "fatal" to a freehand pull of that pattern. The reason is I would not have been aware of the resistance as I started to lift the pattern and then it would have released and then would have overshot much like lifting a box you think weighs ten pounds when in fact it weighs two.

    The reason for the springing of the pattern is its own springiness. Both halves of the pattern are fairly springy along their long axes. The right hand side of the pattern had started upward and the left hesitated an eighth or so and then was forced loose---boing!

    Next time I will be a bit more careful to be certain the pattern is actually fully loose before proceeding with the lift. The damage to the mold was minimal in this case, but could easily have been worse.

    Denis
     
  8. Tobho Mott

    Tobho Mott Silver Banner Member

    I thought maybe you had wedged it into the mold a bit when you had pressed that end back down into the sand there, a moment before using the pedal to sproing the whole thing out.

    I can't even imagine trying to pull that thing by hand! Good job.

    Jeff
     
  9. Melterskelter

    Melterskelter Silver Banner Member

    And that maybe correct too. I am learning this as I go and feeling like I wish I had a mentor on this stuff.

    Denis
     
  10. Tobho Mott

    Tobho Mott Silver Banner Member

    I think many of us are in that same boat. Filming molding and casting sessions can occasionally be more helpful than still pictures. It has helped me on the many occasions when I've reviewed the footage and noticed mistakes I had no idea I was making at the time. I've been trying to use that to streamline my process.

    Redundant movements, thoughtless mistakes, "why do I keep adding parting dust then blowing it all back off again so many times in a row without doing anything else in between?!", seeing my ragged shop coat sleeve drag unnoticed across the parting line side of a freshly molded and cleaned off flask half, etc.

    It's been very helpful. And I've missed some of my mistakes that I filmed too, that's when YouTube eventually points them out to me in the viewers' comments.

    Like the 'steam' defects in a recent casting. I didn't see it but Chirpy immediately (like, within 5 minutes of me clicking "publish" on the 28 minute long video it appeared in) pointed out how they coincided exactly with parting dust clumps in my mold that I had overlooked:

    Capture+_2019-10-09-10-20-13.png

    Jeff
     
    Last edited: Oct 9, 2019
    Melterskelter likes this.
  11. garyhlucas

    garyhlucas Silver

    Denis,
    The system I pointed you to does not have a common manifold. What looks like a manifold is a block of 4 identical cylinders pushed by a common acme thread. So it can be hand cranked but is locked in position or can be motorized. It has been on the market for about 30 years.
     
  12. Melterskelter

    Melterskelter Silver Banner Member

    Gary,
    I think I underestimated that hydraulic system. With four independent hydraulic circuits driven in sync by either an acme screw or electric motor, the general design is well-suited to a controlled pattern lift. It would not work well in my specific circumstances, but someone might be able to apply it to their molding op ration should they need to make a lift.

    I had also been considering a screw-driven gang of 3 or 4 powering cylinders and may want to go there at some point. Having hands free is kind of nice with the foot pedal, however.

    Thank you for taking the time to point out this potentially useful option.

    Denis
     
  13. Melterskelter

    Melterskelter Silver Banner Member

    I made a new rapper and draw spikes for the 48" pattern. I felt that the previously-used spikes were not quite large enough to get to loosening of the pattern. Inadequate loosening may have been responsible in part for the stick and spring of the pattern as shown in the video above.

    So, I tigged 1/8 x 1" tabs onto 10-24 SHCS and made some threaded 3/8" diameter sockets to cyano glue in the pattern. I have just finished the work, but expect them to be significantly more secure.

    Rapper  (2).JPG

    I also made a new rapping tool out of 3/8" steel rod and 1/4 x 1" bar. I put a little bend in the handle to make it more convenient and just tacked the round bars onto the handle.

    Rapper  (1).JPG Rapper  (3).JPG Denis
     

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