Trailer Fender Muller

I started to build a muller a few years ago, but then suddenly changed to bound sand, and so the muller remains unfinished.
I will post what I have just as a comparison between the rotating and stationary drum types (mine is set up for the stationary drum).

The shell is made from trailer fenders purchased from Northern Tool.

The bottom plate is 1/4" steel.

Vertical shaft is a trailer axle.

(some day I will get caught up with work projects and post some new material)

 

Here is the preliminary design.

I changed from all sprockets to a belt on the motor and first pulley due to the speed of the motor.

I will probably add some sort of clutch mechanism, or else a fan belt tensioner with trip-release on over-torque.

I may use a larger vertical support tube for rigidity.

Its designed to dump into a 5 gallon plastic bucked via drop-down door.

 

And I bought enough weights for a dual roller design, and I also found some larger weights, perhaps 35 lb.

I will probably use some variation of a trailing-arm design, if and when I finish it.

 

How do you mix your bound sand?

 

With a mixer. Its a commercial Hobart.

Its bigger than it looks, and a whole lot heavier than it looks.
This thing is really heavy. I bought it and the guy said "You need some help carrying it out?", which was not a question.

I said "No, I got it", but I could not budge it. I thought maybe it was bolted to the table.

Four guys wheeled it out and lifted it into the car.

I used an engine hoist to move it out of the car.
I think it weights 275 lbs.

It came with a wire agitator, and that was too flexible, so I made a steel agitator, and that works well.

I think I can mix 20 lbs of sand, or maybe 40 lbs; I will have to look at my mixing photos to see what the maximum amount is.


Edit:
I found some notes that showed I mixed 32 lbs for a drag, and so I think 40 lbs max is correct.
For larger mixes I use plastic a concrete mixing pan and a garden hoe.

 

For bound sand, they make quick work of mold making.

I have a kitchen size mixer for small molds.

 

I tried to buy one very similar to that one at a auction, it sold for over $1000! Cheaper to make my own mixer.

 

Mixers are not cheap, even used mixers like the one above.
I guess it is all the gears inside, but even then they seem inordinately expensive.

I would have made one, but did not have the time, and it would have cost me more to stop working and make one then to keep working and buy one.

It does work very well at mixing, and it is a compact unit with a small footprint, although it is not easy to move.
I guess I should put it on wheels.

The local foundry at the museum uses an inexpensive concrete mixer with the interior fins removed, and with a couple of window sash weights inside of it to help the mixing process, and they mix the same sand and binder that I use, and it works very well.
Cement mixers can be picked up cheaply; that is a good route to go for mixing bound sand.

And it is also easy to mix sand in a small concrete mixing tub, with a hoe, and that is the cheapest way to do it if you don't do a lot of sand mixing.

You can also mix bound sand in a muller, but you can get buildup on the surfaces.
I scrape all the surfaces of the mixer bowl and attachment after each day of mixing to prevent buildup.

 

so, just to get my head around the processes, mulling is for combining the casting sand properly, and sieving is used to give the sand a fine texture to improve surface finish as a first layer in a mold?

 

I have studied sand nomenclature, and I still don't understand it exactly.

Here is an information sheet on the sand that I use, and it has a chart that shows the amount of sand that can pass through a given opening size (a sieve?).

The chart lists "USA Standard Sieve Size", and then lists "Mesh".
A "sieve" appears to be defined as a mesh (a screen) that is mounted in a frame.

The OK85 that I use is a fine grained sand, and it gives a good surface finish, and the cooler I can pour and still get a complete mold fill, the better the surface finish on the part.

The other key to using bound sand is that it has to be very dry, and the sheet on OK85 lists moisture content at less than 0.25%.

Also attached is a sand chart, which I don't entirely understand.

Edit:
Looking at the OK85 chart, with a 70 mesh sieve size, 82% of OK85 sand will pass through the 0.212 mm (0.00834") hole in the mesh, and for the next largest screen opening which is 100 mesh at 0.150 mm (0.00590") only 40% of the sand will pass through.

So basically OK85 has grains that are approximately 0.00834" in diameter.

I will have to see if I can measure a grain with a micrometer.

 

Kelly-

Thanks for the clarification.

Sand nomenclature is one of the things I understand the least, but that clears it up a good deal.

OK85 does produce a pretty nice surface finish, and it works well with iron as well as other metals.

 

Would a sticky of casting nomenclature be a thing worth considering?

 

Since we're on the subject of sand..............

If memory serves me correctly, I seem to remember reading somewhere that beach sand is a No No for casting.

Is this correct even if the sand was thoroughly washed repeatedly and run through a sieve?

We have more sand here in Florida than we know what to do with.
Some areas even have fine crystal white sugar sand.