Paddle Wheel Muller or Lugged Wheel Muller

I have been toying with changing the wheel I've been using on my muller from a flat-faced steel 4" wide by 8" diameter wheel to a lugged face wheel like the following drawing. This would not be a hard part to cast in iron, but the work involved in making a pattern and flasks would be many times greater than making a weldment. So, a weldment it shall be. As presently conceived it has an OD of 10" and mounts on a common 4 on 4" diameter bolt-on trailer axle hub.


It is drawn 3" wide with 7 3" wide by about 2.5 high lugs welded to a section of 5" Sched 80 pipe with .375 wall.

I think such a wheel would have little tendency to stall and plow through sand---an issue I run into when I really load up my muller. And I think the smashing action of the lugs would help break up lumps. One concern I have is whether sand will want to build up between lugs causing it to become essentially a smooth sand/steel wheel. If anyone has any experience (might well be agricultural) with this sort of design and ideas on improvements, please speak up. This reminds me somewhat of a "sheeps foot roller." Were it not for the plowing and turning action of the wall scraper and the floor scraper of the muller, I think such a wheel would overly compact the green sand.

One possible addition I am considering for the wheel would be to weld in vee-shaped bluntish wedges between each lug to split sand that otherwise might pack into the flat area between lugs. mY thought was to run it first and see if such a problem occurs only in my imagination and respond only if the need is shown.

Thoughts?

One nice thing is this part would bolt on in place of my present wheel and could easily be swapped out if I do not like it.

Denis

 

I would be afraid of a straight paddle wheel type roller of catching two blades flat to the bottom of the muller as it rolls along. It would be different if it was being driven under power with clearance.

If you interweb search 'wintage steel tractor wheels' you see ones with lugs, ones with angled bars, and ones with chevrons on the driven
wheels. On the steer wheels they are often simple ribs. The patterns get crazier on the rubber tires. In most cases there is also less of a delta between the min and max OD for the contact surface.

Maybe angle/overlap the blades a bit so there is always a little something contacting the bottom of the muller? Then use the 3D design to extract a flat pattern for the blades.

 

Your thoughts on the paddle wheel hanging up between lugs are good ones. I have been thinking that rather than allowing the wheel to “roll” on the bottom of the tub, I may suspend it so that it clears by only a fraction of an inch. Otherwise, as drawn, I think the wheel would pound on the tub base making a lot of noise on also might forge eventually deform the 1/2” plate that makes the floor of the tub.

Yes, I have never known how much the scrubbing action actually contributes. The plow on the side as well as the plow on the bottom do a fair bit of scrubbing. I am mostly interested in crunching up lumps of sand from prior melts. Those lumps tend to scoot around the wheel rather than pass under it. They eventually mostly break down. I’ll add that there is some “squishing” which I suppose is comparable to scrubbing with each paddle contacting or nearly contacting the tub base.

Yesterday I mulled without any wheel and got results comparable to my original setup.

I think I’ll just have to figure on a day of fabrication and give it a try.

The more I think about it the more I like suspending the wheel so it just barely clears the bottom of the tub.

Denis

 

One of my first thoughts reading the op was the lack of mulling continuity - the actual smearing and crushing action of the wheel becomes intermittent as opposed to continuous. It would seem that Denis' straight rendering would fluff more than mull. Tops' idea would solve that continuity issue as well as possibly minimize the potential packing of the sand.
I reread the thread by Denis on his muller build. It appears that your wheel runs at a fixed height, or at least a fixed maximum height? Mine is designed to float so the downward mulling force is strictly a function of the weight of the wheel which is fairly significant. I haven’t run it for nearly a year and have considered adding some spring-load to the downforce now that I seem to have overcome my slipping issues.

Pete

 

I do think the paddle wheel will produce the equivalent of a heel stomp with each paddle crossing the bottom of the muller especially if it is clearing the bottom by only a small fraction of an inch. So it should do more than fluff. I am mainly asking it to crunch chunks as I think the two plows provide plenty of shearing/smearing action.

My wheel rides on a round vertical bar housed loosely in a vertical pipe and trails the bar. It weighs about 50 pounds and its own weight pushes it downwards. Since I have recently increased the clay content of my sand and it has gotten sttronger and stickier, my wheel has had more tendency to plow rather than turn. I can mitigate that by running smaller loads and by occasionally scoring the wheel face to put tread on it. But, I am interested in trying a different approach that may allow me to run maximum loads and, more efficiently than a wheel c rush lumps and do so more quickly. It's not that the present wheel does not work. It does. But, ya well, I want it to work faster/better. Never happy I guess.

More vertical loading through weights or springs I do not think is the answer as I have managed to put my foot on the vertical bar and press down with my full weight while the muller is running. This was some help but by no means the full answer.

Finally, the current location of my wheel may not be ideal and if the paddlewheel does not work out, I'll try a different wheel location. If you follow the link below you will see that it is presently far to the right side of the muller. I could move it more or less 90 degrees viewed from above to be at the back of the muller. The sand depth there is naturally shallower as the muller runs and might favor rotation rather than plowing.

There are lots of pics of my original build and some power train mods chronicled here:
http://forums.thehomefoundry.org/index.php?threads/another-cement-mixer-muller.286/

With respect to Tops' cool-looking turbine wheel, I am concerned about just how closely I can space paddles without having sand clog up the paddles. He has the same number of paddles but they have a greater length to height ratio so sand has better chance to pack in the slots between----I think. I agree that his design would roll across the bottom without catching as the paddle likely will hang up if I don't suspend the wheel. His design shows rather elegant spokes that would be challenging to actually fabricate. I want to avoid, if I can, the trouble and time involved in pattern generation and casting a wheel. A simpler version of his design simply using canted straight bar stock might be an answer. Putting contoured feet on the paddles could also improve the rolling performance of my shown design. But may also lead to sand clogging.

Denis

Added, getting some warm clothes on and heading to the foundry to melt some iron very soon....

 

Thanks, that wheel is way easier to make in CAD than in real life... no cutting, beveling, welding, grinding, drilling, swearing, mill-or lathe-work
Wondering if making a Styrofoam blank (plain OD of desired wheel, ID counterbored to mate to trailer hub) and filing grooves into the OD with a large round file/rasp by hand would be a rapid and easy way to prototype this as a lost foam casting.

All the best for the pour today.

 

Well, yes, kinda. But
1) The chunks are not completely free to move out of the way as they are surrounded by other chunks and loose sand.
2) Some of the time the angle that even a free chunk would impinge on a paddle would be right to trap it and crush it even if it were not surrounded.
3) The blunter the paddles the more 1 and 2 above are true. That is why I may end up welding feet on the paddles if they are not effective enough as cut from solid stock.

Sheepsfoot rollers work because of 1 and 2. So, I have a hunch BLUNT paddles as drawn may do a decent job of crunching the rather easily-collapsed green sand chunkies that exist in recycled sand. BTW, I learned quite a while ago that using my feet (is that an old goat roller?) to pretreat the sand saves time. What I do is shovel the sand from dumped flasks on the concrete floor into a pile. Right away the big chunks tend to roll to the periphery (angle of repose favors this) and I simply walk around the pile stepping on chunks. Then I re-shovel the pile and do the same thing. Maybe a third time and I am ready to mull. The shoveling is not done primarily to deal with chunks but rather to homogenize the sand so that each load in the muller takes about the same amount of water. If I don't do this, some of the sand is relatively moist and takes little water where the next load may take quite a bit. It is just easier for me to get one load right and then do each load the same after that. ( I do check as I go. But 95% of the time the water needed is the same from load to load.)

The above is a long-winded way to say I do not know if this will work. But, I'm interested to find out.

Denis

 

I am not a big fan of mullers, you need them in a production shop that is using overhead sand and such. But I really think the best machine for conditioning sand is the Molders Friend.
I run 2 of them, a 70 inch and an 80 inch, with one I can have 12 tons ready in 45 minutes. No lumps, very uniform, very fine. For small batches of sand, say 200-300 pounds, it quicker to cut it with shovel. I think Pekay offers a machine that works on the same principle as a Molders Friend

 

Yes, green sand
It is basically a large aerator, wire brushes on an 80 inch horizontal drum. turns 800 RPM, 2 motors, one to turn the drum and one drive. Moves slowly through the heap with drum turning.
I will see if I can start a thread describing my shop, you will have a better understanding of what I do and why I do what I do.
Moulders Friend is in Dallas City, Illinois. The company was started in the late 40,s or early 50,s. The original owner sold me my first machine, a 70 inch, in 1994. He passed in 1997. The company was sold. The new owner has left the company in the care of his son. Last I saw there is no good web-site, but you can find the company on the web.

 

I amde some progress on my paddle wheel today----until my Miller 211 quit abruptly. It is in the shop on warranty with an expected 1 week turn-around. I'll finish with TIG, I guess. Not much more to do. So not a big deal. But some of the welds will be in tight places and I think the MIG would have been easier for them.

Here are a few photos of the wheel itself. The angles may not be perfect as I simply did them by eye.


The paddles are 3/4x3" hot-rolled. The hub is scrounged piece of 5" hydraulic cylinder tube---nice material to machine and cheap when found on the bone pile at a fab shop. I resisted the urge to make full length welds as the stitches made are plenty strong and long and circumferential welds would only increase distortion.

Incidentally, in taking the old wheel off, I found out that the vertical bar that attached the wheel to the muller frame was bent. This must have happened when the muller took an unexpected dive off of my truck be last summer. The bend was just visible and was enough to prevent easy and free up and down movement and very likely was the main cause of some of the plowing I was experiencing! Still, I have a hunch the paddles may be more efficent at crushing lumps. I should be able to test it tomorrow.

The support frame is ready to be tacked onto the muller frame. The previously used trailer axle hub will also serve as the hub bearing for the paddle wheel. And if the wheel does not work out, I can bolt the old wheel back on with a new and straight support rod.

Denis

 

One more thing to wonder/worry about—-will the paddles kick up sand and throw it out of the muller? That unpleasant thought occurred to me as I woke up this morning.

I will be firing up the tig soon.

Denis

 

Made my first run with a bucket of green sand and water. ANNNNNDDDD


IT WORKS and works very well. It does not throw sand out of the muller and sand does not seem to build up on the paddles. I was concerned about both of those possibilities. The sand seems to get scrubbed off the paddles as it is coursing across the paddles as it exits the wheel. It soes indeed crunch up the clods of used green sand and seems to be a fair bit faster at it than the wheel ever was. I deliberately load in very lumpy sand (lumoier than ususal) to see how it did.

I made one short video showing it in action. I will get some better light on it so the action of the black sand crossing hte paddle is better seen.

It is a "short" video so I have to just insert the linjkj address here:
https://youtube.com/shorts/Y_cyTGHOvso

Whew!
Denis

 

Looks great Denis! Glad you did not let my 'naysaying' get in the way of fabrication and experimentation. About how far off the bottom does it run?

 

1/8” clearance.
Thx

Denis

 

That is very cool, I never really liked mulled sand. I bet its fun to watch it mixing.
Strange, I like to watch the mullers run too....

 

A bit more followup on this build. I have now run five buckets of sand through it to test it and will report I am very pleased with the paddle. It crushes chunks of greensand more efficiently than the smooth wheel ever did and does not plow through the sand no matter how full I load the muller.

I suspect part of the reason for its efficiency in crushing sand chunks is dumb luck on my part. Sure, the paddles do move in a downward arc and must certainly impact chunks that way. But, just because there is limited space in the tub, there are a couple of places where the paddles turn near other fixed objects resulting in a shearing action. Any clumps caught there will be smashed. Some other good luck is that the sand stream gets somewhat compressed against the side wall of the tub as it passes under and around the wheel. This casues the sand to be forced across the spaces between spokes and that keeps those areas free of compressed sand that might otherwise convert the paddle wheel to, effectively, a roundish blob of moist sand doing nothing good.

I made a couple more vids of it in action and one video was shot in slow mo showing that very clearing action. Unfortunately YouTube compresses and degrades the video quality, but I think you can still see what is going on.

Play this otherwise 4-second video back on .25 speed to see that clearing action. I shot it in slow mo, but YT defaults to normal speed unless otherwise directed. You can see a squarish chunk of sand being ejected from each interspoke space as the wheel turns.


Here is another longer video that I now see shows the same action pretty well if played at .25 speed.




And if you just can not get enough video time watching the paddle go round and round, here is a view from above.


Incidentally, it is possible to stop the wheel rotation pretty easily by grabbing one of the up paddles. Getting a hand caught near the intersection of the wheel and the tub floor might be another matter!

So, in summary, it always better to be lucky than smart. I really like the mulled sand that results and look forward to using it to pack up a few molds. Thanks for bearing with me.

Denis