[Cob] rotavator cob

[Robert Alcock]

On the topic of rotavator (rototiller) cob. We mixed nearly all the cob 
for our 2-story, 2000-square foot cob/straw bale house and study centre 
(www.abrazohouse.org) with a rotavator. We had tried a cement mixer, but 
found the cob to be much too lumpy and wet -- the roto-cob was just fine.

We were a bit experimental with the mix -- instead of using just 
clay-sand-straw we substituted wood shavings for 50% of the sand to try 
and get a better insulating wall. The wall is still standing up, and our 
house stayed warm enough this winter with just a woodstove for heating 
and hot water... so I guess it must have worked!

I really can't imagine us ever getting the house finished without using 
machines for mixing cob (we also used a cement mixer for the plaster and 
the floor screed, etc.). Of course you could make the point that our 
house is too big anyhow, I wouldn't argue with you! But if we had done 
all that with volunteers, the embodied fossil energy in the food they 
ate would be many times greater than the amount of fuel we used in the 
rotavator.

Here's a picture of mixing the cob subfloor with the rotavator in situ 
(inside the house).
http://www.abrazohouse.org/?page_id=56&g2_itemId=1931&g2_GALLERYSID=TMP_SESSION_ID_DI_NOISSES_PMT

Glorious mud!

Robert




>>
>> Hi Ed! i just read your comments to Marlin Nissen in the "Coblist" regarding the production of cob with a rototiller. You mentioned that you do the mixing with a 5HP tiller.I am about to start mixing for a 1500 sq feet house.
>>   Could you please share with me your experience and perhaps pictures? What about the long straw? Doesn't it get clogged to the rotor? Doesn`t it get cut into smaller pieces by the blades from the tiller?  I was thinking about renting a bobcat, but perhaps the rototiller is a better and cheaper solution...and I'd appreciate it if you'd share your experience. Thanks a lot!  Eric (EW)
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