Mini mite operation

Discussion in 'Sand Mullers' started by Paperman, Sep 2, 2021.

  1. Paperman

    Paperman Copper

    Been picking up items as I find deals on them. Found a damnear new Mini mite muller. It’s a newer cast aluminum version. The black paint isn’t even worn off the steel wheel.

    How much sand should it run at once? Assuming water green sand.

    I’ve read 25# but that seems like to much.

    How long of a run for mixing new sand, how long to freshen used sand?

    I’m sure allot of it is feel and experience, just trying to get a baseline.
  2. Melterskelter

    Melterskelter Gold Banner Member

    How big do you think your molds will be? I am wildly guessing for a half-size motor, 75 pounds to 100 pounds may be needed for a single mold for some of the larger pieces. I think I read you are planning aluminum castings. So, petrobond (or shop-made K-bond) rather than green sand may be more desirable.

    I don’t have a Mini Mite but I do mull green sand and Petro/K bond. I don’t time it, but the oil-bound sand takes only maybe 3 or 4 mins to freshen up with glycerin and a bit of 2-cycle oil. Green sand probably averages about twice that per batch as it is lumpier when put in the muller as used sand and takes longer to smash up the chunks. And that time on the green sand takes into account “pre-conditioning” on foundry floor by walking on it to crush the bigger lumps and shoveling it to mix drier sand with moister sand as that makes it easier to figure how much moisture to add to each batch.

    For comparison to the Mini, my shop-made 1 hp muller will easily mull 7.5 gallons or about 75 pounds of sand per batch. It is a vintage Red Lion (Canadian) cement mixer that has been modified and repurposed.


    Added: here is some initial build and subsequent modification information as well as some notes on operation. The upgrade to a 1 hp motor made a big improvement in performance.
    Last edited: Sep 2, 2021
  3. Paperman

    Paperman Copper

    Im new so mold size is very open ended. I plan to mount this muller to a bench that it can dump into. I can tell it will fill very fast and needs more room under it or constant attention while running. Im working on simple green sand to keep cost in line while playing/learning. Ill likley invest in K-Bond after I get my brain wrapped around the basics.

    Aluminum is the plan for now.
  4. HT1

    HT1 Gold Banner Member

    25 Lbs is not very much sand if you are making 12X12 inch flasks with a 3 inch cope and 3 inch drag you can only mull half your mold at one time.
    But that 3 minute time in the literature is a little short , I like to go out closer to 5 and of course if your mixing new Petrobond you must mull 11 minutes,

    Unless you have a source for green sand and the additives you will need, I would skip it and move straight to Petrobond, Greensand has a learning curve and petrobond is almost bullet proof, especially if you already have a muller

    good luck

    V/r HT1
  5. Melterskelter

    Melterskelter Gold Banner Member

    Here is a different take on petrobond rejuvenation. Smelko foundry supply says:
    “Reclamation of oil-bonded sands
    The reclamation of oil-bonded sands depends on how much burn out has taken place. In most cases the sand is only used once therefore reclamation is not necessary: In this case a sand aerator should be used to improve workability. If the sand is used several times, depending upon wall thickness or castings, it will lose its plasticity and/or its compression strength. In this case the sand should be reclaimed in mill or core sand mixer.

    To recover plasticity: add approx. 0,1% O.B.B.-Oil
    To recover compression strength: add approx 0,1% O.B.B.-Paste

    Use a short mixing time in the mill or core sand mixer: approx. 2 min. An optimum loosening results from additional use of a sand aerator.

    O.B.B. – Paste buckets 5kg/10kg
    O.B.B. – Oil cans 5kg/10kg

    All information given is accurate to the best of our knowledge but the user must conduct his own tests with regard to the product’s suitability. Applications, use and processing are outside of our control and must therefore be exclusively the responsibility of the end user.”

    I do not know what “paste” they are referring to. Perhaps they sell a bentone (not Bentonite) plus polar agent (various alcohols can be used but I use glycerin as recommended by Tom Cobett, the inventor of K-bond) for addition to petrobond. Their mulling time jibes with my limited experience using petrobond.
    HT1 likes this.
  6. Paperman

    Paperman Copper

    Thanks guys. Is it worth sifting sand or is there a solid resource to buy it? I have acres of beach sand, pretty fine as is. Im working on getting some Bentone.
  7. rocco

    rocco Silver

    FWIW, Smelko is located in Milton Ontario (near Toronto), they are well known for being very helpful and friendly to hobbyists, Jeff (Tohbo Mott) has dealt with them. If you were to call them with questions about their product line, they'd probably take the time to help you.
  8. Petee716

    Petee716 Gold Banner Member

  9. Melterskelter

    Melterskelter Gold Banner Member

    I will chime in to also second or third the idea of getting foundry sand. There are so many variables already in this process that if you could eliminate some,I would certainly do so. I just bought 1200 pounds of green diamond 120 mash for $.13 a pound. I was very glad to be able to purchase a known product not have to somehow improvise.
    There is more to it than simple grain size as the angularity of the greens improves their ability to lock together in a mold and hold well plus the porosity issues that you need to pay attention to so that your sand is not too impervious.

    Beach sand is likely fairly smoothly washed as it’s been worked over by the waves for centuries if not eons so it is unlikely to be very angular. Foundry sand I believe is usually made from solid rock that’s crushed up and consequently has a nice sharp fractures in it.

    Last edited: Sep 4, 2021
    Paperman likes this.
  10. HT1

    HT1 Gold Banner Member

    OK One thing I left out

    Mulling time depends on the efficiency of your muller , and obviously the OP's muller should be top notch so a lower time would be appropriate ,

    the concern of overmulling is crushing the sand and creating fines( Lowers permeability) , I run a pneumatic rubber wheel, so that is a lesser concern

    i've never had access to a sand aerator , they are very aggressive a power riddle is not the same thing,
    a power riddle doesn't deal with petrobond very well, the petrobond has a tendency to roll into balls in the riddle , so you have to constantly get into it with your hand, which is a great way to end up with metal embedded in your paw,

    Otherwise Smelko's instructions seem pretty good
    Paperman likes this.
  11. I have a Mini Mite muller. It works great but I can only mull about 2/3 of an 8x10x3+3 flask. Two flasks and I'm mulling three loads. I get busy doing other stuff so time is not a big issue, but I think about four minutes. I'm dumping mulled sand into my heap so several runs is not big deal.
    Paperman likes this.
  12. Paperman

    Paperman Copper

    Thank you, thats kinda the plan. Just batch run it and store it in buckets/drums until its needed to use.

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