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  1. #1
    Join Date
    Apr 2018
    Location
    Drouin Vic
    Posts
    633

    Default Sand muller build. The MULLMASTER

    I've been wanting to build a muller for ages, as I rarely get a chance to do any casting it is a cumbersome task to get my sand in a reasonable condition after it has been sitting in the bathtub of my moulding bench for months at a time. I picked up an offcut of suitable size steel pipe from the scrappy some time last year and there was a chunk of steel plate amongst a batch of sundries from a clearing sale, a mate swung me a geared motor from an MRI or CT scanner or similar and these have all been taking up space waiting for me to get around to it.
    Lockdown and bad weather combined to get the Mullmaster build started. A few pics to show the progress to date...

    Machined a hole in the base plate to mount the motor, then milled a slot for a sliding door for self-emptying. The slot was milled with a 45degree side-and-face cutter, the sides of the slide machined with the same cutter and the end radiused on the belt grinder to match the opening.

    motor mount underside.jpgtrapdoor opening cut out.jpgTrapdoor bevel detail.jpg

    Made a 2-stage reduction drive arrangement, initially belt drive but later had to convert the second stage to chain drive as the belt slipped on the 2" pulley under load.
    drive assembly underside.jpgdrive countershaft assembly.jpgchain drive.jpg

    There's a central tube with a flange-mount bearing top and bottom, the top has a hub that forms an umbrella over the bearing and provides a central drive for the wheel and paddles.
    top spindle bearing mount milled.jpgfinished paddles.jpg

    Getting the paddles sorted took more work than anticipated, the inner paddle that sweeps the sand out from against the post worked like a charm from the outset but my first attempt at the outside paddle proved too flimsy- this one sweeps the sides and also sweeps sand at the base into the path of the wheel, visible at the 5 o'clock position in the pic above. My second attempt was sturdy enough but I mounted it too close to the wheel and the sand, when moistened a bit, formed one bolus that just moved around and around with the mechanism. In the above photo, the final position seems to work well.

    The roller wheel was made from this cast-steel gadget, no idea what it was for but it was on the 5hp motor that I bought for my RPC years ago. Has also been taking up space waiting for this project.
    wheel casting.jpg
    I cut the finned business off, turned the plate down in the lathe until it went inside the wheel, then bored the hub to take a couple of roller bearings from another long-forgotten source. It makes a suitably heavy wheel for the purpose.

    I tried a couple of batches last night, 3 buckets of sand seems about the right batch size and it conditioned nicely in about 5 minutes per batch, a couple of minutes dry and then slowly adding water to taste. The feed tub under the emptying chute fits 2 batches, a little under half my sand supply.
    batching.jpgtwo batches.jpg
    Needs a fair bit of finishing work yet. I thought I'd need a latch for the trapdoor but the friction moment tends to keep it closed rather than trying to open it. I plan to make a hinged mesh top for it so I can break out a mould straight into the muller. Some switchgear is needed, currently switching it at the outlet of the RPC. Might put some braked casters on it as well, it is as heavy as it looks. Needs some guards on the drivetrain as well. I'll also make a pointy hat for the drive hub so that the sand doesn't sit on it when tipped in from the top.

  2. #2
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
    Posts
    2,651

    Default

    Nice work Pete!

    Steve

  3. #3
    Join Date
    Jan 2016
    Location
    Wodonga Vic
    Age
    38
    Posts
    633

    Default

    Also on my”one day” list

  4. #4
    Join Date
    Apr 2018
    Location
    Drouin Vic
    Posts
    633

    Default

    I know you have all been losing sleep wondering what happened to this project. Of course what's hapopened to it is it's been taking up space in my shed, getting in the way and being ignored for the past 2 years BUT I have decided to get it finished!
    I made a hinged lid for the muller out of some form-ply, incorporating a mesh screen to allow sand to be added whilst the muller is running and- perhaps- poured moulds to be broken out directly into the muller (will see how that pans out). I mounted some some switchgear including a safety cut-off that switches off the motor when the lid is opened- against the day when I am tempted to have a 'feel' of the sand whilst the thing is rotating. A bit of a fence around the mesh screen so sand can be tipped / poured / shovelled in without going everywhere and VOILA!

    lid open.jpgswitchgear and lid.jpg20231230_150244.jpg

    The MULLMASTER 15,000!!

    Name derived from the 15kg test batch (actually weighed in at 16kg but I rounded down). Turned out a very nice batch of greensand, judged from my very limited experience. Produced from the bone-dry used sand that has been sitting in the muller these 2 years.
    16kg batch.jpgimpressed greensand.jpg

    A couple of things left before I can really call it finished; it needs a 'spinner' for the top of the hub so that sand does not sit on it
    sand pile on hub.jpg
    and a lid to keep muck out when not in use.
    The spinner for the hub I think I will cast in aluminium.

    So I'm calling it 'pretty much finished'. It will take up just as much space in the shed, get in the way just as much, but now instead of taunting me with 'when are you going to finish the damn muller?' it will taunt me with 'when are you going to do some damn metal casting?'.

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