Landscape Rock Tumbler




Introduction: Landscape Rock Tumbler

About: Hi I'm kent. I am a maker with a lifetime of experience in electronic systems and automation design. I am also developing skills in 3D printing, carpentry and welding.

Leslie and I are in the process of landscaping and because we effectively live on a rock pile we decided to feature our own rocks in our landscape designs; rock gardens, edging, dry creek bed, etc. The only problem is the rocks that have been excavated during various construction activities were stained a nasty rust color, kind of the natural color of the soil here.

We tried power washing and scrubbing the stones to no avail. So my wife came up with the idea that we need to tumble them just like you would do with small stones in the lapidary craft. "How could we possibly do that?" I asked. "With a cement mixer!" she replied! And thus began the summer our neighbors will never forget - so far we have tumbled over 200 loads of rocks!

Step 1: The Bumble Tumble

My friend John loaned us an old cement mixer for the project, however it had been badly damaged when a truck backed into it so before the tumbling could begin we had to repair the mixer. The fixup included a new yellow and black paint job - hence 'Bumble Tumble'. This Instructable is not about repairing the cement mixer but as a result I have some tips on what to do to prepare a cement mixer for the task.

1. Remove the veins from inside the drum; they are necessary for making concrete but not for tumbling rocks. In fact I think they would be a huge detriment in that they would break or bend out of shape and also cause the rocks to spill from the top of the drum - this would surely shorten the life of the mixer.

2. Change the drive pulley ratio so the mixer turns slowly (about 12 RPM).

3. Grease the drive mechanism regularly.

4. Don't put the rocks in the mixer then start it, have it running first then dump a bucket of rocks in. The starting torque may burn out the motor prematurely.

Step 2: The Operation

SAFETY NOTE: A cement mixer is a powerful piece of machinery, be very careful to stay clear of the drive belt and pulleys and exercise extreme caution when working near the moving parts. Be sure to use a GFCI receptacle to power the mixer. Do not let children come near the mixer when it is operating. Also wear appropriate eye and ear protection at all times!

We tended to sort our rocks into 5 sizes; 'peas' <1 inch, 'eggs' 1 - 2 inch, 'potatoes' 2 - 4 inch, 'grapefruits' 4 - 6 inch and LARGE - anything bigger than 6 inch we did not put in the tumbler. We'd often run batches by size, however it was easier on the machine to put 2-3 'grapefruits' in with 'peas' or 'eggs', otherwise a bucket load of 'grapefruits' got pretty violent in the tumbler.

  1. With an empty tumbler drum, add 1 - 2 gallons of water, 1/2 a shovel of crushed gravel (or 1-2 shovels of 'pea' size gravel, a 1/2 shovel of coarse sand as well as a modest squirt of Dawn dish soap (or whatever is handy). Depending on your particular tumbler you might need to adjust these quantities.
  2. Start the mixer.
  3. While the tumbler is running dump in 2 - 4 gallons of stones from a 5 gallon bucket. Once again, depending on your particular tumbler you will have to gauge the quantity that best suits your machine.
  4. Start a timer for the tumble cycle. We found that 'peas' and 'eggs' took less time - about 10 - 15 minutes, 'potatoes' about 20 - 30 minutes, 'grapefruit' about 30 - 40 minutes.
  5. At the end of the cycle stop the tumbler and remove the rocks by hand into a wheelbarrow or wagon, etc (leave the sand and crushed gravel in the drum) . We used a garden wagon made of expanded metal; you want to rinse the stones off after each load and the wagon worked well for that.
  6. Rinse and repeat! We usually did 10+ loads per day and would completely drain and rinse the drum at the end of each day. The crushed gravel can be reused again but you'll likely lose the sand when changing the water.


  • Rinsing the tumbled stones right away prevents the slurry from the tumbler re-solidifying on your rocks, plus it is very reassuring to see the stones all clean and glistening! Yes, we picked out the gems for special placement.
  • Keep a tally of your loads; this becomes an interesting challenge to try and improve efficiencies and squeeze in an extra load or two each day. It can also create a healthy competition between participants. Further it provides the sense of accomplishment in your achievements.
  • We didn't discard the LARGE rocks, some of them were reasonably cleaned with the power washer. They found their place in the landscape design.

Step 3: Closing

We are extremely happy with the results! Cleaning our own rocks and using them in our own landscape creations has been very rewarding. Is it hard work? Well yeah! But we've never been shy about applying a little elbow grease to make our home look and feel better. It's cheaper than buying washed landscape rocks and a lot less work than foraging the beach and river beds for them.

We hope you get some inspiration from this and next time you kick a stone across your yard, ask yourself 'could this stone be put to better use?'.

Thanks for checking out this Instructable.

Kent and Leslie at the FrontierShed



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    21 Discussions

    I've often wondered if a cement mixer would work for this. Now that I know that it does, I think I'll need to make an addition to my tool collection. And get busy upsetting my neighbors. I'll just give them all ear plugs. Aweaome instructible. Seems very easy.

    very nice, but... safety first!

    Make sure no one comes close to the gears or pulley. Hand, finger or hair.

    You would never pass any safety assurance.


    10 months ago

    Fantastic instructable. What a great idea. Won't forget this one

    1 reply

    Just a head's up, those tempted to purchase the Harbor Freight cement mixer for this (which is often on sale and seems very reasonably priced), *the capacitor that comes with the motor will completely melt on you*. I was just using it for it's intended purpose of mixing concrete but when I left it on for an extended period [30 mins]) it started smoking and when I opened it up the capacitor was completely melted. The cap that comes with it, seemed to be made of mostly paper and plastic!

    It's a super easy fix, just buy a real metal capacitor ($30-60 depending on where you buy it). Since I was mid project I had to go to a local HVAC store for one, so of course they charged me top dollar.

    I'm bring this up so:
    a) you don't cause a fire
    b) include the price of a metal capacitor when calculating the final cost of a cheaper concrete mixer.

    4 replies

    Thank you Zach. I've found the same solution with various harbor freight tools. Simple fix and they're holding up to the big box tools.

    I have to say I am totally amazed that the old 1/4 HP motor on this mixer has stood up to the abuse we put it through this summer; over 250 loads now and some days it was running pretty steady for 6-8 hours.

    Unless it's on the back-side from the picture, It may not even have a capacitor on it, which might be why it's lasted so long. :-D

    If rust color on the stones is the problem, and it truly is the result of iron oxidizing and coating the stones, you only need IRON OUT which can be purchased from Lowe's, Home Depot, and other stores. IRON OUT comes in a white granular form in a white plastic jug. Follow directions and it removes rust from loads of items. I use it to remove the rust (hematite) from quartz crystals I collect in Arkansas.

    1 reply

    Thanks Frank. I'm trying to find Rust Out - not in our Home Depot but I'm sure I can track it down somewhere.

    Although the pictures looked like you might have solved the problem, in your video you mentioned not being able to get rid of the final “layer” of stain. You might try using muriatic acid as a final step. Should clean them right up.

    3 replies

    Thanks for the tip Robert. Perhaps my video production techniques need work; the stones we tumbled came very clean, however we have many, too large to tumble that don't come clean with the power washer so maybe we'll try the muriatic acid treatment, I've never used it so will have to read up on proper handling methods.

    1) Always Add Acid To Water. This is the first rule you learn in chemistry class.

    My 7th grade science teacher memorably demonstrated this: He had a huge beaker set over the sink with a liter of concentrated sulfuric acid. He then dumped a couple hundred milliliters of water into the beaker. It started to boil vigorously almost immediately; and it stayed at boiling temperature for most of the class.

    Muriatic acid isn't too harsh to work with; I've used it (diluted) to clean mortar haze and water stains off of bricks many times. Rinse off the rocks after scrubbing with a baking soda solution (that will foam up excitingly, but is harmless), then finally rinse with water.

    Before disposing of the muriatic acid solution down the drain, dump in baking soda to neutralize it.

    for those without access to a friend's cement mixer a barrel can be used - plastic or steel (plastic is quieter).

    A pair of parallel axels with self aligning bearings on each end with a couple of wheels on each axel. A motor with sized pulleys to turn one axel and you're in business. I've made a couple. If the barrel has a lid it can be laid flat. If no lid it has to be at an angle with a fifth wheel on the low end to keep it in place. Don't have pics otherwise I'd include them.

    Interested? PM me and I'll reply with mockup pics.


    10 months ago

    Nice idea. If the noise creates a problem either with yourselves or the neighbors, you could build a foam insulated box type cover to put over it while running. It won't stop all the noise but should reduce it a lot. I can only realize how noisy it is. I tumbled rocks before, but on a much much smaller scale.

    1 reply

    Foam sound box - good idea! Luckily we live in the country so there was some distance between the tumbler and the neighbours.