Follows crude ASCII | |M| | | | | | | : : | |========|=|========| | | | | | | | | |--------| |--------| | #### |*| #### | |____________________= drain tap legend | walls of tun : perforation in vertical pipe for return flow == liquor level -- false bottom |M| 6 volt motor inside 30mm vertical pipe | | 30mm pipe mounted in centre of circular tun ## coiled 2000w element |*| propeller connected by vertical shaft to motorOur tun is an old domestic water boiler made of copper.
The propeller is cut from dog food tin lid.
Motor is from electric typewriter.
False bottom is 1/4" copper wire screen overlain with copper gauze fly wire both held together by a ring of PVC pipe split lengthwise and wrapped around the whole thing as a retaining clip.
False bottom rests on 1/2" slices cut from PVC pipe and siliconed to tun base.
Whole is wrapped with 1/4" polystyrene foam and light aluminium sheeting for insulation. An alloy lid completes the system.
With this system we process 10-13 kg of grain. Liquor gently flows from centre of tun up the vertical pipe and out over the top of the grain bed.
The motor is controlled by variable speed controller from the hobby shop.
Important to start motor very slow and then steadily build up speed; otherwise you can compact the grain bed.
Element is controlled by an electronic thermostat with the sensor mounted beneath the propeller and only 5mm from the element. We have never had scorching problems and have no build up on the element.
As an extra safeguard against scorching, there is an electronic simmerstat in series with the thermostat. The simmerstat is set to allow power to the element on a 4sec on and 1 sec off cycle.
I suspect that the simmerstat is un necessary, provided the pump keeps running scorching should be no trouble.
This tiny Archimedes pump runs continuously during the mash and the grain bed is not touched after the initial doughing in. Pump is turned off at sparge stage.
The vertical pipe has several perforations and a sliding sleeve on the outside. The sleeve is used to cover the perforations during dough-in thus preventing grain falling down the pipe and clogging up the system. The sleeve also adjusts the height of the liquor return point to just above the liquor level.
The 3/8" perforations are drilled at a tangent to the surface of the pipe.
A plastic ring internal dia 2.5", external dia 7" floats on top of the liquor. The return flow from the angled perforations hits this ring and causes it to gently rotate thus evenly dispersing the liquor over the top to the mash. This prevents channelling.
During the sparge we run the sparge water from a hand-held vinyl hose onto this floating ring.
An automatic gentle hands-off dispersal of the sparge water could be achieved by plumbing the sparge water into the central riser pipe below the motor and above the grain level.
The sparge water would then exit via the same perforations used by the Archimedes pump onto the dispersing ring and across the surface of the mash.
With this system the pump needs to deliver a head of only 0.5cms in order to successfully circulate the sweet wort.
For large rapid temperature changes the simmerstat can be set to continuously on.
Temperature changes are in fact rather slow. This causes us no concern since we can leave the unit un-attended while we get on with serious business of critical appraisal of earlier brews.
We mash in with 2 lit per kilo then after the protein rest add another 2.2 lit hot water per kilo of grain to expedite the temp rise to mashing temp.
Once desired temp has been achieved, even steady temperature is maintained throughout the grain bed within 0.5 deg C.
I have left the system quietly mashing away all night with no discernible (at least to my palate) adverse results. For overnight a blanket over the masher reduces potential heat loss.
Credit for the original design concept belongs to Les Howard of South Oakleigh, Melbourne Australia.