Tobho's HT1-Inspired Cement Mixer Muller Build

Discussion in 'Sand Mullers' started by Tobho Mott, Mar 22, 2018.

  1. Tobho Mott

    Tobho Mott Gold Banner Member

    Well, I found a bearing shop, it's right across the street from work. And if you can believe anything could be even more convenient than that, I also found some different bearings in the old lawnmower wheel I had originally considered using for the roller. I tried replacing the "dust collector" bearing with those; they fit very well and it has been working great ever since, no more problems. Woohoo!

    PhotoPictureResizer_190716_110214518_crop_542x580.jpg

    I was having to add grease after every mulling session before, to keep sort of flushing the grit out of the inside of the wheel hub so that the bearings would not get all gummed up and refuse to roll. I'm sure the sand and clay can get around these new ones, but so far it doesn't seem to be getting into them. If that changes, I have a couple of spares and I know where to go to ask for better ones...

    Furthermore, I had another GC for Princess Auto, so I picked up another one of these wheels, with the idea of the using it to double the width of the roller/compactor in the muller.

    I lined them up concentric, clamped them together, and bolted the two wheels to each other. Amazingly, the central web of these supposedly steel castings were only about 1/8" thick. The chips my drill was making sure did not look or act like steel, I'm guessing like all things at PA that are sold as steel, it's actually some sort of mystery cast iron. I could be wrong. I wasn't about to see if I could smash one with a hammer to verify...

    I had to hacksaw a 1/16" or so thick washer off of the hub of each wheel because they originally stuck out farther than the rims of the wheels, but that was easy enough. Now they sit flush against each other, rim to rim. The old wheel has maybe 1/8" wider diameter than the new one, but I'm not too worried, in time maybe it'll wear down to match. So far I'm not sure, all the mulling I've done so far has only sort of taken the "new wheel shine" off the original wheel. But it's still going to be an improvement, assuming it works...

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    I put a lawnmower bearing on either side of the double-wide wheel and saved the two from the other lawnmower wheel for emergencies.

    It was pretty easy to attach the newly widened wheel to the roller assembly. I just bandsawed the axle bracket in half and bolted it back on around the widened roller. Had to drill 5 new holes and borrow a couple of 1" 1/4-20 bolts from another project to make that happen, but that was about it. And in a stroke of luck, the scraper I made to keep sand from building up on the original wheel? Juuuust barely still fits!

    PhotoPictureResizer_190716_111520442_crop_1011x1027.jpg

    So far it's only been tested with no sand in the muller. (The real test was getting it to fit inside the muller without having to take the roller assembly back apart to fit around the scrapers etc.!) I can't see any reason why it would not work when there is sand in there. Hoping to find out for sure this weekend...

    Jeff
     
  2. Melterskelter

    Melterskelter Gold Banner Member

    Good work, Jeff.

    I very much doubt that the difference in outside diameters of the two wheels will make any functional difference. If, by some odd chance, you feel it is a problem, just get out your angle grinder with a medium or coarse abrasive disc and grind the larger wheel down a bit. If the wheels are supported so that they are free to turn and the grinder wheel engages the muller wheel at an angle, the muller wheel will rotate as it is ground and it will be possible to do a neat job of turning it down. I (we are) am anxious to hear how it works. I am pretty sure there will be a video accompanying your next update. ;-)

    Denis
     
  3. Tobho Mott

    Tobho Mott Gold Banner Member

    I'm not worried about the slight difference in diameters. And don't worry, there will probably be some video eventually but I'm not gonna make you wait til it's edited to post an update...

    Jeff
     
  4. Tobho Mott

    Tobho Mott Gold Banner Member

    I guess I lied.



    The widened wheel works great! The sand actually gets warm by the time it's fully done, from the extra friction.

    After filming that, I removed the spring that tries to not let the wheel raise up, and now it can ride up just a little, so more sand goes underneath and less is forced to flow around it.

    Yet because the wheel is being pushed rather than pulled, it still puts enough pressure on the sand to be effective. I'm super happy with it this way.

    Jeff
     
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  5. Melterskelter

    Melterskelter Gold Banner Member

    Nice work, Jeff. Looks like you have it working just fine.

    Denis
     
  6. Tobho Mott

    Tobho Mott Gold Banner Member

    It was fine, for my greensand. But my brand new 20 year old petrobond packs so hard that after a few minutes it got wadded up under the muller wheel and stalled the whole muller rather than squishing out of the way, even when all the sand I put in it was freshly riddled! (I wanted to see how the muller liked it)

    Yeah yeah, I know, the roller should be getting pulled through the sand instead of pushed, I tried, but it was easier to fit this way and it never did this before now. Price of planning as I built instead of beforehand. I'm gonna have to find room to flip the wheel around after all and put the old trampoline spring back on it, I guess.

    Jeff
     
  7. Petee716

    Petee716 Gold Banner Member

    My muller is a rotating drum-type too and I've found that petrobond is a bit more challenging to mull than greensand. The wheel stops. The biggest culprit seems to be the sand sliding on the bottom of the muller. It hits the resistance from the wheel and instead of pushing under the roller it just stops and piles up. I put some traction tape (like what would be on a steel deck or steps) on the bottom plate of the muller and the problem went away immediately, but the tape deteriorates quickly and creates some other issues so I've removed it. I'm thinking about sandblasting the track of the bottom plate to give it some grip. Greensand doesn't do it at all.

    Pete
     
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  8. FishbonzWV

    FishbonzWV Silver Banner Member

    If sandblasting doesn't provide enough purchase, how about laying down some weld tracks in a sunburst pattern.
    I would think the PB would soon polish the sandblasted floor smooth again.
     
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  9. Tobho Mott

    Tobho Mott Gold Banner Member

    Pete, feel like I have seen pictures of your spinning drum muller before, but all I can remember right now is your old vontorne muller all twisted inside out from when it jammed. I'm sure glad mine just stalls when that happens instead of self-destructing!

    When it did stall, there was a wedge shaped piece of compressed PB stuck under the leading edge of the wheel. Too tall to get bumped over, too hard to squish out of the way, too sticky or maybe too well wedged beneath the wheel to slide on the wear plate (even polished as shiny as it is from eating sand).

    A couple times in the past though, putting a little too much water in my greensand has caused the sand to want to clump up on the outer scraper and let the drum keep sliding under it as you describe.

    Jeff
     
  10. Petee716

    Petee716 Gold Banner Member

    Yeah, fun times! I learned why shear pins were invented!

    image.jpeg
    I think you're right about the sandblasting. Welding is out as the floor is mounted to plywood although I could test with a piece of scrap clamped to plywood and see if it burns it up. A die grinder might be worth a try.


    Pete
     
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  11. FishbonzWV

    FishbonzWV Silver Banner Member

    An alternative could be 1" beads laid in a stair step pattern to prevent overheating the plywood.
     
  12. Melterskelter

    Melterskelter Gold Banner Member

    BTW, Jeff, a while back I upgraded my muller by adding a 1 HP motor to it. I questioned my sanity as I was doing this wondering if it would be worthwhile.

    https://forums.thehomefoundry.org/i...her-cement-mixer-muller.286/page-2#post-27917

    But, I can tell you 5 months later that it was a very good move. Prior to making the switch, I had to be careful not to overload the muller as hard lumps could stall it. So I knew it could do just one 5-gal bucket of sand per batch. But now, it just plows right through whatever I throw into it. Sand may overflow if I scoop it too full. But it does not stall. And I can easily do a bucket and a third.

    One more thing I’ve learned over time is that I save time overall if I pre-condition the sand on the floor prior to mulling. I used to think the muller “should” be able to just manage any lumpy hard sand I could shovel into it. And it would. But it took some time to smash the large hard lumps generated by the drying of the green sand when casting iron. (This is not so much an issue with AL as the aluminum doesn’t cook the sand very hard or dry.). Now, I just dump all the sand on the floor and shovel it into a pile while smacking the larger chunks with the shovel and walking on the edges of the pile where all the lumps selectively roll. A couple times of this and the pile is uniform in moisture content—-a plus since each batch then takes the same added water. And most lumps are 1” or less in diameter. The process is much smoother and faster this way.

    Denis
     
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  13. Tobho Mott

    Tobho Mott Gold Banner Member

    Good idea. It would be nice to be able to put in a whole bucket at a time. The most greensand I ever put in mine has been maybe 3/5 of a 5 gallon bucket. I usually break up the big chunks too so I don't have to wait for the wheel to find them. That's about how much petrobond was in there when the muller stalled too, but it had been fully riddled. It didn't really need to go in the muller at the time, but I was wondering if the thing could deal with the same volume of oil sand as it can green. A couple times before it stalled, it almost stalled, but barely managed to squish out a thin wafer of sand to the sides of the wheel and keep going. I'm pretty sure a wheel on a hinge being dragged instead of pushed will fix that problem, given a suitable spring to keep it bearing down hard enough but not too hard.

    Hey Pete, if you can't some weld some bumps onto the floor because of the wood under it, could adding them to the wheel instead maybe work?

    Jeff
     
  14. Melterskelter

    Melterskelter Gold Banner Member

    Wheel diameter matters on this rolling vs plowing issue, too. You likely have noticed that the wheel is very inclined to roll if it is encountering sand only on its lower 1/3rd. But, as the sand gets deeper the sand “wave” is pressing against the portion of the wheel above the axle as well as below the axle. The more it presses above the axle, the more it neutralizes the rotational force on the wheel. So, the larger the wheel diameter, the better. I have thought about putting a deflector in front of the wheel that would push sand out of the way so that sand only hits the bottom 1/2 of the wheel. This could be tested just hand-holding a metal deflector or shovel blade so it prevents sand hitting the upper half of the wheel. Havnt done it yet.

    Denis
     
    Last edited: Nov 17, 2020
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  15. HT1

    HT1 Gold Banner Member

    OK I run a very similiar Muller doing petrobond, first , I think you are runnign a little too much sand , especially if the sand is cold, old cold petrobond is HARD to mull.

    additionally , if you look at the videos and pictures, I used a Pneumatic wheel , and alot of my mulling action comes from sand getting caught between the trailing edge of the wheel and the side of the muller , rather then Just ubnder the Wheel ,

    Jeff if you remind me early saturday morning I'll make a video of mine running Petrobond, so you can get a good look at the Mulling action if there is not a good video floating about (I dont think there is

    V/r HT1

    P.S. Isoprpyl alcohol 90% from a mist bottle seems to make the petrobond mull better , but I have always worked the sand Hot so that could be a hot sand event
     
  16. Tobho Mott

    Tobho Mott Gold Banner Member

    Thanks, I'll try and remember to remind you, and to try and find some of that 90% isporopyl alcohol.

    Jeff
     
  17. rocco

    rocco Silver

    FWIW, I get 99% isopropyl alcohol at an equestrian supply place. Last time I bought some it was $17 for a 4L jug, that was about a year ago, I'm guessing the price has gone up considerably since then.
     
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  18. Petee716

    Petee716 Gold Banner Member

    I buy the 99% from an industrial supplier for work. It's known as "anhydrous isopropyl alcohol". (No water).

    Pete
     
  19. rocco

    rocco Silver

    Pete, have you bought any in recent months? With the covid situation, I'm guessing there's probably a bit of price gouging going on now.
     
  20. Petee716

    Petee716 Gold Banner Member

    I haven't, but I'm due to pretty soon. I'll let you know.
     

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