Another cement mixer muller

Discussion in 'Sand Mullers' started by Melterskelter, Mar 25, 2018.

  1. I found that to be a very interesting statement. It does make sense to press and slide for good mixing. That one comment has led me to think about using my 5" wheel on the original bottom of a mixer with enough weight on the wheel to get the action desired (whatever that may turn out to be). In a "what have I got to lose" concept the wheel can always be changed to narrower or smaller if need be so long as the mounting brackets are fully adjustable. Melterskelter's square tube-fully bolt on design is absolutely perfect for making adjustments or major modifications.

    Andy
     
  2. Melterskelter

    Melterskelter Gold Banner Member

    It looks to me like some skidding helps keep moist sand from sticking to the wheel. Early on, when I was test running my muller as I was building it, I was using some dry sand. No sticking whatsoever then. But as soon as I started to run actual greensand, I noted some sticking. As luck would have it (I knew of no guidelines and just tried different positions) the sand now seems not to stick to the wheel much if at all and I think that is because the sand scrubs a bit sideways as the wheel passes over it. If some sand does stick for a while, it seems to slide off after a minute or two.

    In think a wider wheel encourages more scrubbing than a narrow one. The way I have tried to understand this is: on any wheel turning a tight curve only one narrow part of the "tread" actually is tracking tangent to the circumference. The other areas of tread are drug off the course they would "like" to take. The wheel averages all those courses and finds the course that minimizes resistance. (You have a lot of time to think about such things when mulling a couple hundred pounds of sand ;-) )
     
  3. Petee716

    Petee716 Gold Banner Member

    I don't know that it's preferred, but it was impressed on me that the "smearing" action was a big part of making a muller effective. I think both are probably equally important. As melterskelter said, the wheel will always have some of its surface skidding. I figured Since the drum turns relatively slowly and the wheel is fixed, more skid isn't going to hurt the muller any and should coat the grains of sand more effectively than just relying on compaction.


    Pete
     
  4. Melterskelter

    Melterskelter Gold Banner Member

    Looks like it is doing the job well! Are you running a 3-phase motor with VFD to get a soft start and variable speed?
     
  5. Petee716

    Petee716 Gold Banner Member

    No it's single phase. Repulsion/induction motor. J.Vibert gave me a nice explanation of how they work. http://www.alloyavenue.com/vb/showthread.php?10647-Petee-s-Muller-Build/page3
    I had never seen one before. It gives me vaiable speed control in both directions. Bonus!
    Unfortunately it was in rough shape when I got it, so it spent some time at the motor shop ($) before I put into service. Runs great now.

    Pete
     
  6. Melterskelter

    Melterskelter Gold Banner Member

    Very interesting. I had never heard of RI motors and they sound like they could be very useful. You caused me to begin reading about them. I like that! Now I understand the lever you are moving in your video.

    Here is a one minute video on this type of motor:
     
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  7. J.Vibert

    J.Vibert Silver

    I wish I could get my hands on a RV motor (adjustable spd). They're really cool imo... I have a small mountain of the RI type. Unfortunately due to the vintage of the tech, even a 1hp RI is quite large. The one 2hp Century RI I have squirreled away is difficult to lift.

    To the discussion regarding the angling of muller wheels. I too have always been lead to believe that it aids in the "smearing" of the sand, which helps bond the clay to the sand, which is the whole point in a muller, and why mixers aren't necessarily good mullers. I haven't reached the point yet, but I intend on pitching the wheels in my muller. No definitive angle as of yet.
     
  8. Melterskelter

    Melterskelter Gold Banner Member

    Last edited: Apr 1, 2018
  9. Rocketman

    Rocketman Silver Banner Member

    I recently purchased an older Simpson muller. Here's a slow-motion video of the plows & wheels in operation. Figured it might be useful reference material.

     
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  10. Melterskelter

    Melterskelter Gold Banner Member

    Wow, amazing find! Any guess as to how much down-pressure there is on the wheels? As much information as you can glean from a “real” muller is very valuable. So, any bits you can post here has to be helpful to all of us making do with homemade. For instance, how does that wear plate scraper work? Is it spring-loaded? Is it slightly inclined like a low-angle block plane blade?
     
  11. Rocketman

    Rocketman Silver Banner Member

    I can get you some really detailed pictures of the muller this week. I suppose I should start a new thread for it.
    But for now:

    The wheels aren't terribly heavy - maybe 25lbs each? I can pop one off and weigh it. They are assisted by a common spring betwixt the two via bellcranks.
    There are two plows, an inner and an outer, adjustable but not spring loaded. I am having some minor issues with the force of the sand making them rise up out of their adjusted state.
    There is an additional sidewall scraper.
    There are no wear plates on this model, it is made entirely from what appears to be cast iron. It is ridiculously overbuilt, the entire tub is roughly 1/2" thick.
     
  12. Melterskelter

    Melterskelter Gold Banner Member

    By no means would I want to overburden you with details. But, whatever information you can provide is very valuable as that machine provides guidelines for solving some of the problems that would-be muller builders can otherwise only guess at. Thanks for sharing the information
     
  13. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I can't tell for sure if Rocketmnan's Simpson has spring loaded wheels but given the complexity of the suspension I'd suspect so. If so it looks like it might be a slightly different arrangement for suspension spring loading than the one at the Simpson website. Rocketman's looks like it may allow motion and camber whereas the website looks to be just trailing arm motion. The Simpson website talks about "adaptive tooling" (that's some good marketing :)) since the pressure increases with increasing strength and depth of sand. If so knowing the weight of the wheel may not tell you what you want to know.

    Looking at Rocketman's video, the wheels look to be mounted at/near tangent to the arm. The only point that is perfect rolling motion in that arrangement is at the tangent point at the bottom of the wheel. As you progress up the wheel in deeper sand there will be increasing skid/scrub. When you look at the trail of compacted sand you can see evidence of that in the fracture lines. That all may change a little bit with wheel travel but you'd probably have to have more sand depth than recommended for the muller to make any appreciable difference.

    Per the previous comment about skid, if the orientation of the wheel is changed to produce more skid/scrub, the required input torque/power likely increases as well. I suspect there is a minimum contact pressure that's easily achieved for effective mulling but beyond that it's just differences in batch processing time. It's always nice to have good performance and tune in your equipment but if you're not a commercial foundry optimal performance probably isn't a big factor.

    Best,
    Kelly
     
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  14. Melterskelter

    Melterskelter Gold Banner Member

    I am thinking the scrubbing action of the wheel is probably not all that important. But,it happens to some extent by default and to a greater extent on relatively wider wheel than narrow ones. If you look at the video of my muller and the stills, you will see that the inner portion of the wheel is a bit rusty and the more lateral portion is fairly shiny. That is because the distance traveled by the inner portion of the wheel is less than that of the outer and for some reason the inner portion seems to keep up with the sand traveling under it better than the outer portion. The sands slides under the outer portion resulting in a polishing of that part of the wheel. So, yes, there is some scrubbing of the sand and probably that is a good thing. How important? Who knows? Sand does tend to build up on the inner half and does slide off on its own, but it never builds up on the outer half. FWIW.

    On a wheel setup like mine, if the vertical pivot axis is moved further away from the center of the wheel contact area, the wheel will tend to be drug more off of a tangent track and more scrubbing will occur. On mine the pivot axis is nearly at the center of the contact surface of the wheel and still it gets drug off a little from a tangential orientation.
     
  15. Melterskelter

    Melterskelter Gold Banner Member

    I recently made a small addition to my muller. After adding Western (sodium) bentonite to my sand, I was experiencing Increased build-up of sand on the wheel. Until recently I was using only Southern (calcium) bentonite in my sand. But, hearing some of the benefits of Western, I decided to add a pound per fifty of it to my mix that already had 2.5 pounds of Southern bentonite. True to its advertising, the Western is stickier and caused more problems with build up of sand. So, I added the scraper which I had been “thinkin about” adding for a long time. It is very simple but quite effective.

    It consists of an inexpensive door hinge and a piece of 1/8” thick steel. The angle it makes with the wheel is about right to make it tend to press down onto the wheel rather than ride over adhering sand.

    FWIW, a small but useful addition that someone else might be “thinkin about.”



    Denis
     
  16. Tobho Mott

    Tobho Mott Gold Banner Member

    A nice addition. I have a wheel scraper in mine too but it's not hinged, all it does is keep the stuck on sand from building up past a certain thickness.

    Jeff
     
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  17. Melterskelter

    Melterskelter Gold Banner Member

    Jeff,

    Keeping a manageable layer of sand on your wheel might be better than cleaning like my scraper. The sand layer prevents wear! Anyway, it sounds like your solution works well and does what is needed.

    Denis
     
  18. Melterskelter

    Melterskelter Gold Banner Member

    I upgraded my motor on the Red Lion Mixer-based muller. The cement mixer had a 1/2 HP motor on it which did OK. However, the capacity of the drum is about 60 pounds of sand and the original motor was just barely enough to turn that and would occasionally stall. That slowly became more and more annoying. So, I bit the bullet, bought a single-phase 1HP motor at Grizzly (whose home office is 1 mile from my house) and got the welder and angle grinder out. A few hours later----new motor and quieter operation. I think the original motor was installed in such a way as to put excessive tension on the chain drive and that caused noise which was augmented by the chain drive sheet metal cover. I found that relaxing the tension on the chain a bit markedly reduced noise.

    The more I cut into the old mixer the more respect I have for its design, though. The chain drive is lubricated by a grease zerk in the axle and pivot point just in front of the motor. In other words, the axle has a hole in it that delivers some of the grease from the axle itself into the chain drive enclosure. So, the chain is well lubricated. I also noted that chain, despite hundreds of hours of operation in the dirtiest possible conditions, was free of sand. The enclosure for the chain, though made of thin sheet metal and far from air-tight is very effective in keeping out dirt. In the pics the enclosure was temporarily held in place with c-clamps as the screws for the enclosure are out at the foundry.

    The old motor mounted right to the enclosure via the 4 through-bolts that hold the motor together. Unfortunately, the new motor bolt pattern did not match---too great a diameter, naturally. So a "shelf" for the motor had to be made. I made it from stuff I had in the pile of left overs. A few pieces of angle, a 3/16 plate, and some 1" square tubing made a pretty solid support. I was tempted to triangulate the support, but that would be overkill. The square tube might appear to be precarious, but it is attached with a secure circumferential weld to the angle and plate.

    Muller Motor Upgrade 2.JPG Muller motor upgrade.JPG Muller Motor Upgrade1.JPG
     
  19. Melterskelter

    Melterskelter Gold Banner Member

    Of late I noticed my muller wheel has seemed reluctant to roll and was more inclined tro plow throught the sand if the muller was more than 1/4 to 1/3 full. That is a problem as the clods of sand then aren't rolled and smashed by the wheel, but instead tend to just get pushed aside. And I surely don't want to operate the muller a less than full capacity. Why this tendency had develped was not obvious to me. The bearing in the wheel were smooth and turning freely. The wheel was free to ride up and down on the shaft that supports the wheel. But one thing I had noted was the wheel and the plate on the floor of my muller were now nice and shiny. Each began its life with some rust and roughness. But with many hours (hundreds?) of use the the wheel and the floor were polished up.

    So, today as I was mulling and the probelm seemed worse than ever, I started testing a few things. Holding a shovel in front of the wheel while the muller ran so as to deflect the stream from contacting the upper half of the wheel didn't help. Then I decided to take a hammer to the muller---that is I decided to "texture" the wheel and the floor a bit with repeated hits from a 2 pound hammer. I could see hints that the wheel seemed more inclined to roll with that "treatment" even if the rolling was in fits and starts. Next step was to grab my angle grinder and with the muller empty but turning, I started running the grinder wheel rapidly back and forth across the wheel and then did the same to the floor. Low and behold, roughing up the suerfaces was the answer. Rolling was restored and I was a happy camper. I am sure this texturing will wear smooth over time, but reapplying it now that I know what is the root cause should be no problem. It probably actually would take less than 5 minutes and likely will be necessary only every few months.

    A blurry photo of the textured wheel
    Muller Texturing21.JPG

    The textured floor
    Muller Texturing1.JPG

    Not sure if this will apply to anyone else's muller, but I thought I would pass it on. I am sort of embarrassed that it took so long for me to figure it out.

    I do think I will also add a deflector in front of the wheel to help the wheel mainly encounter sand only at or below its axle level. That should help promote rolling as well and allow full loading of the muller which will ordinarily mull 75 pounds of sand at a time.

    Denis
     
    Last edited: Mar 10, 2021
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  20. Petee716

    Petee716 Gold Banner Member

    Nice work Denis. I've had the exact issue with petrobond. Greensand not-so-much, but petrobond has always given me the issue. I finally went through a similar process of elimination and came up with the smooth floor surface being the culprit. I am also a bit embarrassed by the process. I proved it by applying strips of grit traction tape to the muller floor and the problem vanished. That's obviously not the long term solution as the tape fails in short order but breaking up the surface did the trick. Deciding how to disrupt the surface without creating an unfortunate result has been the stopper for me but seeing your results gives me some relief. I was thinking I'd actually have to scarify the surface, but it would seem that an aggressive scuffing should do.

    Pete
     

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