Bought a grout mixer: sand muller lookalike

More than a few guys on this forum use a modified cement mixer although the USA version is different to an Australian cement mixer.

 

Yep I used to do the old cement mixer and shotput version a many years ago. Worked pretty well for green sand. From memory I am pretty sure I got the idea from these forums.

I have long since built a muller somewhat similar to the 'Kooka Muller' seen on the Tube although mine has two mulling wheels with a completely different spring
tension system for the wheels and a different scraping set-up. Lots of trial and error

As with that and many other casting related projects reading these forums over the years has been of enormous benefit - absolutely invaluable!

I can look at the pictures now too!!!


Charlie

 

I put some crushed rock suitable for making concrete into the grout mixer to try and scrub the rust off the bowl and it nearly jammed a couple of times as the outer blade has 10mm clearance from the bottom and the outside wall where stones can wedge. I'll try and add some rubber conveyor belt and bolt it to the rotating blades to get a minimal air gap and see how that goes, failing that, some extra steel welded on the blades. I'd really like it to be able to handle a refractory concrete mix sized aggregate while I make this new furnace. Other geometries like a set of comb like fingers could work too.

 

I dismantled the faulty gearbox to reveal a surprise: I thought it'd be a housing full of stripped planetary gear teeth but it's a newer tech cycloidal pin drive according to the label. There's no obvious damage or broken parts but it's "crunchy" in one direction and smooth in the reverse direction. I flipped the nutating gears over in the hopes it was wear on the teeth but it had no effect the original direction was bad and the reverse was still smooth. I'll strip it down for the third time and pull off the two roller bearings that drive the two gear: it has two identical gears in the center that have eight spigots on a flange as the output shaft, so they doubled up on the gears for strength I guess.

There are two parallel roller bearings on eccentrics driving the gears, I'll pull them and see if they can be replaced.

 

So I stripped the unit down for the fourth time and pulled a small ball bearing so I could remove a pair of parallel roller bearings. The bearings run directly in the sprocket gear thing (cycloidal disc) which has a bore of 45.1 mm while the bearing has over 1mm gap in the bore. The part number of the bearing says the diameter should be 46.5mm. The rest of the gearbox shows no real wear in the cycloidal disc or the pins it meshes with. I'll order a new bearing and see if it fits the disc bore.

Edit: I cut the inner races off the camshaft and the bearings have failed: inner races have spalled off pieces of steel .

 

Ordered a pair of bearings, I had to order a slightly different part number: N205 instead of RN205 which comes with an outer race that gets discarded, AUD $25 each.

 

With a bit of luck the hole the bearing goes into won't be too worn at 45.13mm. There is a variant of the same part number with an outer diameter of 46.5mm that would allow boring the cycloidal disc.