Another cement mixer muller

now obviously in Florida, I dont have to deal with the cold, But I have no problem with sand slipping, I think it maybe the Pneumatic tire I use,,, well and using Petrobond, green sand mulls a little differently

V/r HT1

 

if you look at my youtube videos, you will see my muller acts differently with the sand, it mulls mostly on the side of the muller rather then the bottom of the wheel, this is not a new concept, the Mulboro (SP?) has a mulling action closer to my muller, and no this was not some grand plan of mine, I saw the wheel at HF and threw it in , hoping it would work, but fully prepared to have to build something solid and heavy, as most DIY mullers utilizes,

V/r HT1

 

Iwas able to nearly double the capacity of my muller and still get the wheel to roll by using a blocking paddle in front of my wheel. The thing was a huge front of sand was coming at the wheel in a stream that wanted to pass over the wheel as well as under it. But, without the blocking paddle in place the wheel had little motivation to turn. But by putting the paddle in the path of the wheel it prevents sand from directly impacting all but the lower about 1/3 or 1/4th of the wheel . See post 45 above. That will not prevent the sand from sliding of course, but that is now handled by rust and scoring the wheel and the tub base plate. The limiting factor now is simply tub capacity. It can hold 100 pounds. After that sand starts to spill out. The 1 HP motor was a big plus too. But, now I can process 2 full 5 gallon buckets of sand at a go. Spreading the sand out on the floor and mixing it up and walking on it helps markedly reduce lumpiness of shaken-out sand and reduces batch time considerably.

Denis

 

This is what I do about cold petrobond. I've eliminated the torch on the right. It's not needed. Also the green wire is no longer needed to raise the elevation of my wheel. That was one of my attempts to overcome the sand sliding issue we've been talking about. Once I scuffed the floor as shown in my earlier post the problem has been completely solved requiring no intervention.
I am getting a little more sparking in the commutator/brushes area of the motor than I'm happy about, but that's a subject for another day. Otherwise the muller is working as effectively as I'd hoped.

 

I like how quiet your muller is and the rhythmic railroad train-like clicking is soothing. Interesting that just scuffing the floor makes such a positive difference. It is sweet when you get them working well, huh?

Denis

 

I just repowered my muller and not by choice, really. The pinion gear that drives the cast iron ring gear and thus the tub simply wore out and quit with a loud clunk a week ago.

Here is the chain drive case (black stamped steel) and wallowed out bearing that carried pinion


Close up of worn bearing

Pinion gear

Rehubbing the chain drive sprocket. I had a chunk of stainless round bar of the right size. So, I used that for the hub.

I thought some about casting a new gear to match the worn out gear. But besides the gear itself being worn the bronze plain bearing that carried the shaft mounting the gear was also severely wallowed out. It became evident that 1) making a pattern, casting the gear, and machining the gear plus replacing the bronze bushing with its required machining (awkward as the bearing was mounted in a large heavy frame casting) was going to be a lot of work. And, even worse, the plain bearing and gear were still going to be subject to considerable wear given the environment in which they were operating. AND that pinon gear/ rack gear train was very very noisy. Instead I decided to use an automotive 6-rib serpentine belt driven by a common alternator pulley mounted on a modified made-in-USA mandrel that would carry the pulley on one end and the large chain sprocket from the original drive system on the other end.

Here is a video of the muller operating as seen from the side.

Here it is seen from above. You can see the idler nestled between the motor and the drum. It is a common automotive serpentine belt idler mounted on an axle I welded to a moderately robust door hinge. It is tensioned by a spring whose tension is adjustable with a bolt that pulls on the spring.




A very big benefit of the repowering of the tub is that it is much much quieter. I no longer have to wear hearing protection when mulling sand!

I put a hundred pounds of recycled sand in the tube and mulled it without the slightest hesitation of the drive. I preserved the rotational speed of the old set up by using a 3 inch pulley to replace the 3" pinon gear. It rotates at 30 RPM as the motor is a 1725 RPM motor with a 60-to1 reduction between the chain drive and the 3 inch drive pulley on the 24" tub.

Denis

 

That looks well designed and executed. I’m sure once the pinion gear and bearing got to a certain point in their lives they accelerated the deterioration. The mechanism surely had plenty of use in its past life. Too bad they failed without notice.
Your mounting looks robust enough too handle the job overall, and the drum will certainly handle the belt wear pretty much forever. Hopefully the sand won’t create issues. That should last you pretty much forever.

Pete

 

Thanks, Pete. I put a lot of thought into trying to make a robust, serviceable, inexpensive, and simple as possible repair. I was amazed that all the components were in stock at various retailers here in town. Even the No.35 roller chain. I learned that serpentine belts are available in a very wide ranging number of lengths. Idlers and pulleys were cheap. All the needed items probably cost about 175 dollars.

Not shown are guards for the pulleys and the chain case top. I used polyethylene foam to make effective seals where the axles enter the chain case and sealed the case with silicone rubber. It seemed no worse for wear having served for decades in a much less well-sealed environment as originally designed. So, I think it will have virtually no sand ingress now. I’ll check it every 6 months.

I do not expect significant wear on the tub due to belt contact. Should that occur, I’d just weld a band of 1/8 or 3/16” strap in that area to build it back up. All the other components are easily sourced if needed but all the bearings are sealed. I was amazed that the typical double-cone “wheel bearing” that has carried the tub for at least 50 years in a maximally dirty environment was in as-new condition with no grease contamination or evident wear.

So, all initial indications are good. Time will tell if there are unrecognized pitfalls. But, I’ll be giving it a decent workout this afternoon as 500 pounds of sand needs to be mulled.

Denis

 

The muller is headed back out to the foundry havingf spent the last week in the shop for repairs and upgrade.

Here is a video of it running with guards in place.


And a few pics of the guards themselves.

As she looks now(I actually sprayed the fabricated parts since the photo)
No more ring gear

Chain case with fabricated cap all buttone up and fron guard below it. I sealed the cap with silicone rubber. No sand should get into chain now.

Rear guard and idler.


Will put her to work this afternoon.

Denis

 

I made another small tweak to the muller. This one was to reduce wear on the plow, reduce noise, and decrease turning resistance.

Until now my plow had simply pivoted on the vertical shaft it was welded to as pressure of the sand forced it into contact with the drum wall so that it scraped sand that might otherwise stick to the wall as well as stirring the sand in general.

By placing A small wheel between the drum wall and plow it is possible to maintain a 1/16” gap between the plow nose and drum wall. The wheel is on a pivoting arm that can be adjusted to determine how closely the plow grazes the wall.

Installing the wheel has reduced noise which was previously overshadowed by the very obnoxiously loud ring gear and pinion

I would not be surprised if some adjustments to the design will become evident through use. The wheel is a 28mmOD sealed bearing press fit into an aluminum wheel I turned. I made the wheel with an O-ring tire.

This is the plow on its shaft.

Some detail photos



Denis

 

Another well thought-out modification. It must be a great relief to have that machine running so much more quietly.
I have a bit of a cautionary tale though. Here is a picture of my first muller. It was built using the VonTorne plans found online. The drivetrain was my design. This shows the second and final iteration of the framing and drivetrain design with and without the guarding.


The initial design was not as robust, but it worked fine. The issue with it was that there was no shear pin or other provision for a jam-ups in the drum, and the first time a pea-sized piece of tramp metal got hung up in the less-than-pea-sized gap between the drum and mulling blade, the 3/4hp motor folded the drivetrain frame right in half. It didn’t damage any of the components thankfully, but the frame was destroyed. The new design incorporated a shear pin as well as a loosened drive belt which were appropriate modifications for this particular design and the next time I got a jam-up (rare), they functioned as intended.
So it’s no surprise to me that my memory always goes back to that event.

The drum on my current muller was made from a long piece of heavy duty steel shelving, probably 18ga, rolled in a makeshift roller, and then welded. It turned out pretty darn well for a novice job, but it’s not perfect. So I wouldn’t even consider direct contact of the plow. I keep about 1/4” clearance. I can’t really tell if the rind of greensand that forms around the outside perimeter gets rotated back into the mix as it goes past the plow or if it remains undisturbed. As moisture is added to the greensand I know it’s texture and stickiness makes the sands movement more likely, but I can’t really tell. I guess I could add some colorant to the sand to make a test to find out.

Now that I have scuffed my drum’s floor and the slipping action has been overcome I am more open to experimenting with different plow positions. I have not done so yet, but under the previous circumstances the plow positions were worked out to minimize the slippage and I was hesitant to touch them. As of now I still get the rind mentioned above as well as a static center pile, so I may do some experimenting. For now though I have plenty of access from the front to safely intervene with an entrenchment tool.

Pete

 

Thanks, Pete.

That is a good point concerning jamming of the drum. My drive is not quite as positive as yours for a couple reasons. First, the chain drive reduction in my setup is the first rather than the final reduction. And my belt, being serpentine, has less wedging/locking tendency than a plain vee-belt. Ultimately, my drum will stall it it encounters locking resistance. Finally, all the components of the drive are bolted or welded to the 2.5” square tube providing a very robust spine-like frame that would require huge forces to fold it.

And yes, the fact that I could mull yesterday without wearing ear muffs and just hear the gentle sounds of the motor and chain drive was really sweet.

Denis

 

That is an interesting observation to consider.

 

Here is another tweak of the muller. A few posts ago I posted about using a wheel to hold my plow off the side of the drum. That worked OK, but the bearing seemed to fail after maybe 6 hours of use. They are cheap and relatively easy to replace, but I thought about using UHMW as a tip for my plow. Making one from a scrap of UHMW I had laying about was a 5 minute job. The plow itself is made from 4 X 1/4" hot-rolled bar. So I just cut a very slightly less than 1/4 slot in the tip and pushed it on and then gave it a few whacks with a hammer. It may eventually require a fixing bolt, but seems to be staying in place after the first hour or two of use. I do not know how it will wear. It has worn imperceptibly so far. It should reduce wear on the muller drum and it is quiet.

Here is a pic.



Incidentally, a steel plow rubbing on the drum wears fairly rapidly so that after 20 or 30 hours of mulling it might have lost an inch of length.

Denis

 

Sorry to see the wheel didn’t work out. That looked like a bit of a project.
I didn’t know what UHMW is so I googled it. That looks to be quite a useful material.

Pete

 

Looks great Denis. Every shop I have been at (OK both of them ) that works on process machinery seems to have some application for UHMWPE. The name of that polyethylene is certainly a mouthful with a six-letter acronym.
I have some 'regular' HDPE from an old kitchen cutting board that I use for projects. It is great for molding epoxy as it naturally releases from it.
When I used to work on big mixers, we would have slotted holes in one side of a wiper to paddle connection to allow for some clearance and and wear adjustment.

 

In this case, the plow is mounted on a freely-turning pivot. As the UHMW wears, the wear is taken up by the plow pivoting a little more.

Denis

 

Here is the plow tip after 2.5 hours mulling. I think it is going to last a long time.



Denis