Cob Re: Commercial clay production

[SANCO Enterprises <Paul & Mary Salas>]

Keith , John and other Commercial Mudders,

Getting mud to a wall surface that is well prepared and economical has been a

challenge for those building in the field.  In evaluating those who are
successful adobe
brick manufactures generally use pug mills, paddle mixers and conveyor belts
to deliver
the material to a lay down machine that forms 25 bricks or more at a time.
The lesson
here is in the mixing followed by the methods used by those in the plastering
field who
use plaster pumps. The mechanics involved have to be combined into a single
system.

 In this example, John Glassford  wrote
snipped
   > We are in the process of rendering/stucco some 250 face square metres at
the
moment in earthen/clay/straw>

   >however at CASBA's International Straw Bale Conference I met Harald Wedig
from
Germany and he is in the process of tracking down a pump as follows by
Harald's
reply.>

In response to this commercial need and especially cost reduction
(time/labor/material) I
developed a total mechanical hydraulic system to mix/pump/spray clay soils.
The essence of the machinery is as follows.

 1)  I adapted a material feeder that consists of a hopper with counter
rotating tines
similar to that used to in a manure spreader to break up clumps.

 2) The dry/damp soil material is conveyed to feed wheel proportioner that
places a fixed amount of material into a mixing 9" variable speed auger. At
the same time as the
material enters the auger, water or water/stabilizer is introduced at a
metered rate depending on the moisture content of the soil.  The mixing auger
is on an incline of 30 degrees with notches cut out of the auger to cause a
folding action of the material as it travels the 10 feet to the end of the
auger.

 3) At this point we apply the lesson from the plaster folks.  I purchased a
Little Giant
plaster pump for $300, removed the motor and the small screw pump and
retained the paddle mixer blades in tact. At 90 degrees to the length of the
mixing tub I cut out a slot to accept a 7" pipe that extends 12" beyond each
side of the tub. After notching the tub so that the pipe nested 50% of its
diameter in the tub, the pipe was marker and also notched to create a void
from the tub to the pipe.  A 6" compound feed screw was adapted to fit the
pipe with flange and shaft at one end. Hydraulic motor was fitted. The
process here is to accept the premixed material from the screw conveyer and
allow for continuous mixing in the tub when the conveyor is stopped. This
prevents settling or separation of the soil material.  The compound screw at
the bottom of the tub is used to convey the soil material into the pump.

 4) We continue the lesson from our plastering friends.  The small 1-1/2” x
14” pump that comes with the Little Giant plaster pump is too small to handle
the heavy viscosity of clay soils.  Here we need to learn from our industrial
friends who are involved in pumping heavy fluids such as asphalt, slurries,
syrups or grouts in mining applications.  I purchased a 6” ID x 3 ft long
Moyno pump manufactured by Robbins/Meyers for $170 at a USDA Farm Lab sale on
a sealed bid.  The pump is based on the Moineau design and most pumps of this
type are now manufactured in Germany.  A new pump is VERY expensive,
therefore look to auctions, surplus equipment dealers etc. for bargains.  The
pump screw is elliptical and encased in a very heavy rubber boot.

The Moyno pump can be fed from both sides or from the top.  I placed the pump
parallel to the tub and connected by way of a flange, the tube protruding
from the tub containing the compound screw.  The pump is capable of pumping
32 gallons of material per minute at 300 RPM and 1400 PSI and will pump the
material in almost a dry state.  The pump discharge was reduced to 2” and
standard 2” concrete hose was adapted with vic-fittings. This permits a
variety in application methods.  The material may be allowed to flow freely
and be used as in cob construction.  The hose can be fitted with a shot-crete
nozzle and sprayed as mixed or the hose fitted with a gunite nozzle and
additional water added for finer material application.

The entire machine can be used for plaster or concrete as well just by
changing the in-feed materials.  Everything else remains the same.

I received a USDA federal grant to demonstrate the feasibility of
constructing full scale homes utilizing this equipment and various
combinations of soil mixes.  The project starts May 15 and ends Nov. 1,
1999.  Hope this gives some of you inventor types some ideas.  If you want
specific info, write me privately.

Paul