Having just one 5 gallon bucket of concrete ensures fresher mud without extra transfer work. If you have to take a phone call, cleanup is fast. Waste is minimal. Much larger mixers make sense with larger crews. Today's affordable and lightweight drills make hand held mixing possible (and can even run off solar panels) . First a warning is given: Hand held power tools can overwhelm either a user, the power too litself or things nearby. A beginner should approach such work with great care and personally assume all risk.The pages of this website are offered only as a free exchange of personal experience and evolving ideas.  The versitility and portability of the electric drill has proven useful in cement mixing. This research looks into ways of mixing with drills, inside of 5 gallon buckets. Note: These pages are placed in the public domain and are furnished "as is". The author assumes no responsibility for the use or misuse of the concepts in this series. All authorities should be satisfied first, as might be required, by relevant laws, before any building proceeds.

A helix impeller which is less than half the bucket width creates a mini whirlpool inside the helix impeller itself. This uses less power than a full bucket sized whirlpool. A small helix acheives layer inversion more efficiently than a small fan like blade, as the whirlpool propels itself inside of bucket. However a full width fan like blade can work very smoothly , given more power. A whirlpool is needed to invert stratified layers within the bucket and mix them. I've been measuring amperage and a full bucket width impeller can run more than 8 amps at 300 to 500 RPM drill speeds. High amperage power surges apply the excess amperage as heat within the motor. We might check this further with precision. Does surging a 7 to 8 amp drill motor from 11 to 16 amps, on a regular basis hurt the motor? May we assume amperage of a drill rating is worth heeding?   Very intermittent surging and with lower surges, has, for some users, seemed not to hurt a drill in practice. Perhaps the heat was low enough compared to other cases of motor burnout.  A Fluke 36 Clamp On Meter has been used to digitally measure actual electrical current usage, (leading to general opinions on this page). For example, the "S" shaped impeller pictured below was used to whirlpool a common 5 gallon bucket of mix. A "Superhawg", 13 amp, 450 RPM  angle drill was used. Readings generally ranged just under 13 amps for a reasonably thick mortar consistency of mix. Only once or twice , (within several buckets of mixes), did the amperage exceed 13 amps, (just for an instant each time, due to stiffer ingredients). Faster- smaller drills especially need reduced loading and a smaller helix lightens the load and improves the range into difficult, sticky or fibered mud. Bakers were perhaps the first to use slim spiral bits to mix stiff dough. Or was it some other trade? The author started experimenting with junk auto-truck springs for concrete mixing, on a quest for small scale, low tech automation in mixing. That is the quest and motivation for this prototype experimentation. More recently, ultra low cost rebar corkscrew mixers are also tested.

Picture Above: A cheaply made mixer experiment using a drill with a car spring for bit/ impeller. It is resting on a simple hanger which can very easily engage an electric trigger switch to allow stirring while adding material. See a building under construction which used only this mixer for tons of concrete mixing. Below, same drill mixer hangs from a welded rebar stand with slow feed hopper. Drill vibration vibrate-feeds dry mix into bucket. Bucket is held by auto wheel with rags tied around to softly grasp the bucket but allows bucket to turn slowly. Some small auto wheels are nicely sized and tapered. (Just cut out hub area). Add just enough rag to hold pail or adjust for slow bucket rotation which wipes the full bucket-- Almost hand free operation, while the mix is very wet, (water first). Strategy is to add last of the dry aggregate last. Critical point here: the helix whirl pool might haveto move around bucket or the bucket has to slowly rotate to get the whirlpool to finish mixing all contents of bucket. Some testers have not appreciated this aspect.  Beware, it does take determination to prototype tools, to balance spinning impellers and to understand contexts of details.


The whirlpool of a corkscrew mixes top and bottom layers inside itself. Additionally, it can sweep the side, the bottom and even rotate the bucket slowly around. The effort needed to assure this is rewarded only by cheaper toolsets. People with better budgets or grander scales of operation will not likely find this useful. For a corkscrew with half the bucket diameter-- The whir pool is kept to a small fraction of the bucket volume which eases the load on the drill. Yet the whirlpool keeps mixing the otherwise stratified layers inside a bucket. Layer stratification represents poor mixing. By comparison a full bucket width impeller, can indeed whirl the entire contents of the bucket but does require more power to do so. Also, full bucket whirlpools are difficult to achieve with some particular mixes. Extra heavy drills are available, like the "Superhawg" above (US$340).  The weight and bulk of these drills has admirably been reduced with modern technology, but the prices can run very high for the best drills. Slow enough speeds are not popular with most drill uses. Slow speeds most suitable for plastic buckets are available from gear motors but gearmotors are to heavy too hand hold. The helix impeller research focuses on "small is beautiful", low cost small "whirlpool" mixing and needs only one standard item: the ordinary, widely available drill along with moderate improvisational skill.

(More Pictures To Come)

(More pictures of experimental progress will be added).  The "S" shape is conveniently made from two half turns of a car-strut spring and welded together to form an "S".  The shaft is welded to the center of the "S".   This impeller can turn smoothly and has a reversible feature when turned clockwise vs counter clockwise. It can hook and draw ingredients away from bucket edge or do the reverse. The reverse is a good way to expel fibers which can in higher doses, excessively accumulate on impellers. Modern drills like the "Superhawg" offer easy electrical switch for reverse rotation.


(More Pictures To Come)

Next on right side of picture above- The "S" has been separated into two "C" parts. One "C" part sweeps the bucket bottom, welded to shaft end. The other "C" part is a little higher on the shaft and angles down to gain more vertical propulsion inside bucket. The arrangement has seemed helpful for larger, (egg sized) aggregates. Half of a bucket diameter happens to equal a very common spring/ strut size to be found in older automotive junk.


Still needing improvement(above) is a dual "C" section mixer more like a sculpted boat propeller shape. For a ferrocement mixer bit, cement could fill the space between two curve shaped rods.

Next is photo of crude version mounted on gear motor, (mixer is hinged with counter weight). Here, a conic section) agricultural bucket is used instead of plastic.


Next above is latest prototype with two spring sizes welded into progressive double helix. Above to right is spring section welded to flight section.More reports will follow eventually.

Next- Above is two flight sections for study with fiber mixing. (However a slower gear motor needs to be fitted, without time available here at enerseasrch). Below on left is my first full- sweep- bucket- mixer which was mounted on a 14 amp gear motor.  It was made of random ring parts of alloyed industrial scrap. In it's last uses from many years ago, I was too preocupied to wash this impeller between batches.


Above Right- A cheap effort to mimic the flat ribbon impeller similar to a "flight", see below. (A parallel bar was welded to a larger spring for a gear motor to impart greater loft for finer mixes but more loft demands more power. Sleeker bits are better. Below a short piece of spiral "flight" was used, (a little wider than half the pail diameter). Flights are used for particle conveyors and much more expensive than bending a helix. For dedicated fine grit cement mixing, it is far cheaper to put 2 helixes together or add a little curved plate at bottom. (See methods to bend corkscrews or to weld car springs below). The flight was tested for mixing fine cement, nearly instant mixing with well timed feeding of ingredients. The flight "pushes" enough to feed a radial peristaltic pump, (recycled radials).  Metered feeding of ingredients for batch mixing is a reasonable possibility.  A stack of old pulleys (found as junk), were welded together to adapt gear shaft to mixer shaft, (different sizes). (These are tin metal and require careful use of mixer, to avoid breaking). A counter weight (an old farming plow), is used to ease lifting of gear motor. (Odd framework is simply recycled bits and pieces had on hand). Reversible motor is a plus. One can reverse direction to push last minute additions to bottom. The pail/ bucket can rotate slightly as the impeller mixes. This evenly wipes all of the sides. The height of pail is controlled with just enough sand in base so that pail bottom is also wiped/ scraped.


The helix mixer above was cut from a "flight" which is a flat ribbon like helix. It was cut and sculpted at the bottom tip with alloy welding rod. The bottom tip has a slight fin like shape to it which helps veer the tip closer to bucket corner. This mixer is mounted on a 14 amp gear head motor, which in turn is mounted on a hinging stand.

Next, below is a foot pedal bucket grabber for plastic buckets. It was improvised from auto wheels.

How did I build prototype mixers from scraps?

It's easy for a serious prototyper but maybe not for a other persons. Creative cementitious work generally requires sufficient inspirational motivation to push through the difficulties. This page and other linked pages generally reflect the agony and ecstasy of creative prototypes and thinking outside the box!

I don't have a machine shop. Left over materials and odd scraps provide ample shims and braces. Coffee cans or tins may fit inside of a car spring. Wrap the cans/ tins with scraps of sheet metal or mesh for a snug and more accurate fit. Face the solid end of tin/ cans at corkscrew ends. Push a straight rod through center (pre-punched-drilled can/ tin ends). The rod should protrude far enough from one end to become the drive shaft. Loosely lay a bar scrap across shaft and corkscrew at same protruding end and weld. Then, cut away alignment end of shaft just below weld. Weld three "bumps at shaft end so that drill chuck can grab tighter. If you don't have a lathe for precision grinding, this can give good slip proof centering in drill chuck. A broken SD bit also avoids the hassle of tightening chuck in the middle of cement work. Or if you can stand the delays, weld the chuck to the shaft, preferably an old worn out chuck, (cringing while welding a chuck forever closed ;) Oh well, that solves major frustration when tired of tightening chuck every ten minutes. This makes a slightly wobbly mixer that works acceptably, proves the theory, but wears down unevenly. So when you see that, bend shaft to compensate, and re-weld to wear out other side ;) Below are my only photos on hand which show a "do it your self" alignment and welding. A stock coupler was selected to match a gear motor shaft. It was temporarily held with a snug fitting socket wrench and rod to allow alignment with spring. This spring is a small one intended to absorb shock. At other end a double helix impeller was welded, (see below).

A side note is don't fear using rusty junk. Our disposable society needs to reuse more junk, (hereby becoming a sustainable society).

Bigger and bigger bits will tempt the experimenter. Below is a bucket wide, double helix impeller with steeper pitch than car springs. Powerful gear motor is much heavier than a full pail of cement. Hinging the bottom base drops pail for loading and unloading. Crank is seen to left in picture, for fast hinging up and down of bucket. A lever (seen on ground) with steel band grabs the bucket tightly. Here the problem was that the entire load of mud was too often mobilized and turned with double helix impeller, (instead of mixing). I meant to remove or reduce the bottom bucket scraper, (not easily seen). For vertical impellers which are close to pail diameter, a counter acting but at the same time stationary impeller would seem critical. A stationary helix would simplify design requirements. The idea here is to explore controlled reflexive flows of mix material for continuous mixing. This might prove useful for automatic batching and feeding to cement pump. 

An abrasion resistant alloy is preferable. One problem with ordinary plastic pails is the tendency for the pails to warp into an oval shape, (due to heavy cement lifting). If mixer users could collectively demand wear resistant alloys, there are small alloy part producers who will customize ideal parts. A light weight alloy pail and machine balanced impeller are reasonable to ask for. Let me add your name to start a list of interested users. One person's small market impact alone is not enough. I'm willing to help promote better mixers on a non-profit basis. I'm looking for would be developers, entrepreneurs and vendors to work with. I prefer to remain a prototyper and artist.

Below: For cement preservation as well as faster production, a plastic bin is used to hold cement. Bags are designed in such a way as to absorb atmospheric moisture and unfortunately are harmful to cement in a humid climate. Measured amounts of cement are scooped and added to mixing pail seen in pictures. A simple, movable metal frame above bin with a knife like projection pierces bag. Once pierced the bag may be opened by pulling opposite ends up and shaking. The bin is easily open and shut in case of rain. This bin size holds 3 bags which allows uninterrupted mixing of considerable "mud". (One should avoid plastic bins which are or become brittle and break. Look for guarantees in product data).


Here is my testimonial on why i prefer bucket mixing.

I started one-man contractor work with a rubber paddle mixer but eventually got rid of it. (Wheel barrow load size). Usually i've worked solo, so keeping cement shaded, (cool), washed, covered from rain, in addition to the wheel barrow... plus keeping the batch tempered, the work in stride and smoothed as well.... Failing to keep materials cool or a bulky batch from over heating. Plus maintaining every other mechanical thing. Minimizing tool surface contact with cement saves time. The less contact the better. It doesn't need much cleaning or sun shading.

You might not fit that spray shovel into a bucket, but i see using a simpler spray lid adapter which could work more simply still. Just remove mixer and put on this spray lid. Heft it to shoulder and shoot like bazooka, (swords to plow shears).

I would love an automatic bin fed batcher that could fill my pail like a soda machine. I have been building toward this for years but pulled through. Last but not least is the physical space consumption of a project. Big equipment can get in the way, tear up a yard, loose material, crush the wife's flowers and always costs 10 times more than auto repair for equivalent parts. Blessed are the poor... At least they have fewer equipment problems ;)

FC chat group, with big archive online. Use a search engine like google to tap into many opinions about ferrocement.

 A page describing sand molded concrete and ferrocement sculpture. "Earth Molded Concrete: Artisan Secrets"

Comments are invited. Consultancy or constructive cooperation is offered.

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