Larger Moya???

Discussion in 'Burners and their construction' started by HT1, Jun 14, 2019.

  1. Jason

    Jason Silver Banner Member

    Hey Jeff... You lose man.. My wife now holds the title of queen of the ugly thrift store lamps. Almost 3ft tall. She wanted the harp off it. cost 2bucks.
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  2. OMM

    OMM Silver

    @Jason .... I think this should get spun off to a new thread. I have a few worst and best lamps using a 1/8 27 straight electrical threads.

    Electrical threads were a spin off of pipe threads with no taper. Most of the time they used schedule 40 pipe and used pipe thread pitch. They adapted this as straight pipe electrical thread. It is by most the weirdest in the industry. Over the years they have reduced the schedule 40 stipulations, and referred to this as straight pipe thread.
  3. Jason

    Jason Silver Banner Member

    yeah, I read the story on the net about how they came up with this thread. Interesting stuff.
  4. Tobho Mott

    Tobho Mott Silver Banner Member

    Finally used the 2-1/4" Moya with the taper at the front (with the gaps around the taper now plugged up) to do an aluminum bronze melt in the big furnace. No burning inside the tube this time, and I was able to switch to diesel after 6 minutes of preheat using about 5psi of propane (ie. The 0-10psi dial about halfway open. Ish.)

    That is significantly faster than I have normally able to do with the standard Moya burner. I don't know if that's because the same amount of air can come into the furnace at a slower pace through a bigger tube so it doesn't cool down the furnace as much, or if it maybe lets the combustion occur lower down or what, but it works and I like it.

    The final burner test is from 10:50-18:50, but if you watch the rest and have any ideas about my casting defects, I'm all ears, please do tell.

    I tried to do the bifilm gating stuff but I still got weird booger-holes on my axe casting which you might see sort of in the thumbnail. Smoother on the inside of the holes this time though, I think. They were on the cope side. Is it shrink maybe? Something else? The drag had some small pits near the edges as well. None of it is anything I can't clean up, but it's annoying.

    Pictures of gating:



    Booger holes:



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  5. Tobho Mott

    Tobho Mott Silver Banner Member

    Oh... Chirpy just pointed out and now I see it in the pic above of the cope that there seems to be an excessive amount of parting right where all the divots ended up. Steam from damp parting maybe?

  6. Melterskelter

    Melterskelter Silver Banner Member

    Damp parting compound??? What compound are you using—-talc? How could it be moist enough to steam and still sift nicely?

  7. Tobho Mott

    Tobho Mott Silver Banner Member

    It's chalk line chalk. Didn't seem damp, but I do keep the bottle out in my shed. Would it do that if it was really dry though? Maybe, I don't know. I'm trying to make sense of it.

  8. Melterskelter

    Melterskelter Silver Banner Member

    Can the chalk off-gas when subjected to high heat. “Chalk” decomposes fully at 825C It is calcium carbonate and so could be expected to produce CO2 on decomposition. I think it is producing CO2.

  9. Tobho Mott

    Tobho Mott Silver Banner Member

    Another lesson learned I guess... :oops:

  10. Melterskelter

    Melterskelter Silver Banner Member

    Seems like Foundry work is full of hidden lessons just waiting to be learned—-too often the hard way.

    This one comes as a surprise to me. I use talc (purchased as “after-shower body powder” at the Dollar Store) a parting agent. I am generally not very careful about how I apply it. Sometimes I know it has been laying in a pretty thick layer on parts of my pattern, but I never noticed trouble from it. Since it is supposedly chemically similar to chalk, I’m now surprised I haven’t had trouble.

    But then I looked baseball line chalk and found it is not all the same.

    It just may be that talc is more resistant to off-gassing. Next time you pour it would be really interesting if you could do a provocative test on an waste piece half of which used your current chalk globbed on and the other half using talc.

    I have seen videos of experienced casters use a soft brush to spread out parting compounds. Maybe there is a reason... I am going to be more cautious about talc application in the future. Thanks for your hard-earned lesson learned.

  11. Tobho Mott

    Tobho Mott Silver Banner Member

    I've used talc-based baby powder and this chalk line chalk for parting. Never noticed any difference. Never noticed any problems I could trace back to it either, until now.

    First bought the chalk because I remembered an old thread on AA where someone had looked up am MSDS on "real" parting compound and found it to be just about identical to (I think it was Stanley brand) chalk line. Not the brand I ended up with; I'm too cheap So I got the in-store brand. It doesn't smell like baby powder at least...

    If I shook it out of an old sock (parting bag) instead of being lazy and just using the chalk dust bottle, I would not have had those clumps and maybe the casting would have turned out better.

    The defects were nothing I couldn't grind out quick enough on my belt sander, so as lessons go I'd have to say this one was pretty cheap.

  12. oldironfarmer

    oldironfarmer Silver Banner Member

    If yo look in the cosmetics department you'll find soft brushes.

    I'm no expert but from watching others I basically brush the parting off the patterns. No way you could get it all off. Try to wipe it off your fingers.
  13. OMM

    OMM Silver

    I’ve toured three professional foundries that use pressurized air blowers (8 to 10 psi) around 3-4 inches away.

    For parting, they all use graphite powder or graphite spray. I asked one of my foundries, for some of the graphite powder and they said no!
  14. Tobho Mott

    Tobho Mott Silver Banner Member

    I do use a soft brush to remove excess powder from patterns. But not from an empty mold cavity, I try to blow out any extra parting that gets in there in hopes of not damaging the mold even with ny very softest brush. I often add some parting right after drawing out patterns, to keep any grains of sand they might get blown or flicked around while cutting gates etc. from sticking to the mold cavity, and that is when the problem clumps of parting arrived in this case. A proper parting bag and maybe venting the mold better would probably have helped avoid this, I guess.

    Sorry if I derailed the burner thread by asking about my casting defects here.

  15. HT1

    HT1 Silver Banner Member

    ok sprinkle parting using a Muslin Part Bag, sample below, I use a 6X10 you could go smaller, only fill about 1/4 full and sprinkle AT LEAST 1 foot or two above, you want a fine dusting of powder . I have to turn off my fan, while I dust a pattern to get an even layer ( light dusting) that is the key

    for parting I use Graphite Military Surplus, just like I used in the Navy Foundry . each new pattern gets rubbed down with the Graphite parting bag, then 000 steel wool , then I go back with a brush . in the Navy we had a Parts cleaning brush with 3/4 in bristles , I have never found a replacement, I use a trimmed 3/4 in nylon paint brush, it is really too soft but works, work the Graphite into all the nooks and cranny's with a brush then blow off . all the Graphite you need is now on the Pattern, in most cases, if you are having troubles with a pull, dust with Graphite and parting

    here is my blow gun of choice, completely adjustable , normally very low hold far away if blowing out a mold

    Parting I use DE Filter Powder for pools , work Put it in a Muslin bag, remember light dusting, if you get a lump blow off the pattern and start over . I work mostly in Plaques with a mirror polished finish so i need it perfect it's alot easier to sprinkle powder then buff out rough spots

    There you go Just how I doo It

    V/r HT1

    P.S. I have no Idea what this has to do with Moya's???
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  16. Tobho Mott

    Tobho Mott Silver Banner Member

    That's my fault, sorry, this is the casting that resulted from the test run of the new burner, but it has really nothing more than that that is of relevance here. Parting tips noted and appreciated!

  17. Chazza

    Chazza Copper

    Graphite creates nodular cast iron I believe, which makes much stronger cast iron.

    You should be able to buy it easily as it is used as a dry-lubricant,

    Cheers Charlie
  18. Chazza

    Chazza Copper

    The foundry-man who taught me, said to never use talc; perhaps it was for this reason.

    For years I used parting-powder from a foundry supplier, but as it ran low and I couldn't buy anymore, I experimented with dry-sand as a parting agent and it works very well,

    Cheers Charlie
  19. HT1

    HT1 Silver Banner Member

    Nodular Iron is more complicated then using graphite as a parting nice read here

    V/r HT1

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