WHAT IS A PAN MIXER?
A mixer filled through an opening at its top, for concrete, usually a pan or drum within which is mixing blades revolve about the axis, for mortar,usually a trough within which mixing paddles revolve about the horizontal axis.
WHY PAN MIXER?
Generally we prepare our premix (earth + sand) for cob with the help of JCB. But recently we tried something new as an experiment with the help of JCB, that includes the preparation of the final mix (premix + straws). At start it was great to know that we won’t have to stomp with our feet and also a large batch of cob was being prepared at one go. But later on we realised that the experiment was not successful even after getting a regular supply. It was because of the lack of homogeneity and the quality of cob.
As the monsoon is arriving and the walls still have to go up as per the plan. So we were really looking forward for some alternative for faster cob technique. And then Prasad came up with this idea of “Pan Mixer” out of the blue. That was really a relief for all of us. But still there was a long way to gobecause with the pan mixer too we had to experiment a little. So there was a scope with Pan Mixer.
Exp1- We started with the first experiment where the direction of the blades in the pan mixer was clockwise (i.e. forward).Initially we started with a dry mix (premix) of earth and sand (4:1). After that we added water is such a way that the consistency is in middle. Then 5 barns of straws were added.
Observation: Straws started to break and all the long straws were gone. That was because of dry mix and the force of the blades of mixer the straws were twisted and broke immediately. So this method failed.
Exp2- After that we went for a little wet premix and then added the straws slowly. The ratio of the mix was same and only the water content was different.
Observation: Slowly during the mixing, straws absorbed the water in the premix and after that again the straws were breaking.
Exp3- This time we tried it a bit differently. We started with the dry mix and before mixing the dry mix properly we started adding the water. After that it became more wet and blended out nicely. This time the ratio of earth and sand was (16:4 1/2). Due to the high content of water, the mix was too sticky so the quantity of sand was increased a bit. After that we added straws immediately in 5 minutes, trying to finish the whole mix quickly all in 15 minutes of time. Also in this trial a few changes in the machine were made to make the process more workable and easy.
Observation: This mix was homogenous and the long straws were there. This experiment was successful.
CHANGES IN THE MACHINE
• Firstly there the change in phase and the reverse switch was introduced with Prasad’s help.
• Then out of the 4 blades, one of them was changed. As there was some stone that stuck between the blade and the surface of the mixer, due to which it got bended. Also after that the blades were shifted 5 mm apart from the surface of the mixer, where they were in contact of it. That was from sides and the bottom.
• Faster cob
• Bigger batch as compared to foot cob
• We could get long straws when done properly
• Homogenous mixture
• Cleaning takes time
• Requires a lot more people and coordination
• Volume produced is only 0.25cu.m .
• Wet mix so only a thin layer can be laid at one go.
• Wet mix tend to wrought after 2 days because of more water content.
• Evaporation of water tends to leave more water cracks if not shaded and treated well after laying.
• Few times because of more load the mixer stopped so repairing was often required.
• Loading and unloading needs to be planned because it’s a bit time taking.
The workability of pan mixer can be improved as there is a lot of scope. We are not done yet and still looking forward for better solutions &results. We are not giving up! Thanks to Prasad for this great machine.