[Cob] those pics of the beautiful tree-sculpted wall...

[Shannon C. Dealy]

On Sun, 11 Jan 2004 ataraktos at hotmail.com wrote:

[snip]
> (from potkettleblack.com) were in the results of my 'tractor cob' search
> - is this wall an example of tractor cob? as i can't foresee ever having
> enough time (or feet!) for a traditional cob house, i'd be interested in
> anyone's opinions about tractor cob.

Some problems with tractor cob are:

    - tractor cob mixes are not as uniform, with feet mixing you can tell
      if there are problems with the mix and adjust accordingly (to much
      or to little sand, clay, straw, or water), and then ensure that
      it is properly mixed.  With large tractor mixes it is much more
      difficult (bordering on impossible if you mix on bare earth) to make
      changes in the mixture once the mixing has reached the point where
      you can tell if there are problems with the mix.

    - if you mix on bare earth it is more difficult to get the desired
      mix ratio (due to picking up additional earth from the mixing
      surface).  At least one tractor based mixing method (there are a
      few different approaches) probably doesn't suffer as much from
      this problem, but it also gives the worst mixing of any approach I
      have seen.  If you have a large concrete or asphault pad/street
      available for mixing on, this is not a problem.

    - Buying or renting a tractor or skid loader costs money, and is not
      an option available to everyone.

    - Noise and pollution -- don't know how important this is to you, but
      there are always trade offs, the building I'm sitting in right now
      was all mixed with a skid loader using lots of sand hauled in from
      off site, the building next to it was done entirely by hand and foot
      work with nothing but jars for windows brought in from off site.

Shannon C. Dealy      |               DeaTech Research Inc.
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