Make you own Thermopot Mashtun

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Make you own Thermopot Mashtun

Postby Pakman » Mon Jan 01, 2018 19:12

Back in December, RobDob (of this parish) was clearing out the remains of his brewing kit which I purchased from him.

The collection included two shiny pots, a 30L and a 15L.

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This was the 30L pot.

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And this was the 15L pot, which had a weak handle so I removed them to prevent accidents.
I decided to build a thermo-pot mashtun from them both to replace my picnic cooler model.
Starting with the 15L pot, I drilled a hole in the bottom to allow a bottom drain in order to reduce deadspace.
I used a section of broom handle and a circular hole in a piece of wood to create a recess in the bottom of the pot so that the drain fitted into a dip.

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The 15mm Tank Connectors I had in stock were quite high so I modified one by drilling holes through the fixing Hexagon. The next picture shows before and after.

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I then fitted the modified drain into the bottom of the pot and ran 15mm copper pipe out to the side via a soldered right angle bend.

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I removed the original tap from the 30L pot and cut a support pad from 60mm thick Kingspan insulation, and made a groove from the centre to the edge to allow for the drain pipe. This would ensure the inner pot would sit solidly inside the 30L pot. I then fed the drain pipe out through the original tap hole on the 30L pot as I lowered the smaller one down inside so to sit on the Kingspan block. Unfortunately I didn't photograph this part as it was quite fiddly to get the outlet pipe to be in the right place. I ended up using a loop of string through the hole and round the pipe to guide it in place.

The small pot inside was loaded with bricks to hold it exactly in place and the top sealed with tape to stop any insulation foam going inside. The top edges of both pots were also protected with tape before the builders foam application was injected between the inner and outer pot to provide insulation.

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The completed job was left to harden for about 2 hours before trimming and cleaning to reveal the insulated pot.

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I then turned my attention to a grain filter. In my existing coolbox I have successfully used clear plastic sheet with lots of 1mm holes drilled through as a grain filter so I decided to do the same again. In order to cut a 305mm circle I made a 'jig saw' jig. I drilled a 1mm fixing hole in the centre of the sheet and used a panel pin to fix it to a wooden board. I then clamped the jig saw blade exactly 152mm from the centre fixing and then rotated the sheet under the operational saw to get a circle cut.

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Once the circle had it's edges cleaned up, I stuck graph paper to the top edge and started drilling 1mm holes at every line intersection except for close to the edges.

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Two and a half hours (and approx 2100 holes) later I then fitted spacers (feet) to the bottom surface and a handle in the centre of the top to assist getting it out for cleaning.

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I then checked it for fit but will have to wait for the Silicon Tube to arrive before I can create the perfect edge seal required. I will use 1mm split wall hose to fit around the edge of the filter. The next photo shows the filter in place in the bottom of the mash tun. You can also see that I used a piece of old hose to create a waterproof thermal barrier between the two pot tops.

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A test using water this afternoon has shown that there is a very small amount of deadspace (19mL measured) once the mash tun has drained. I'm happy with this as it's much better than the amount wasted using a top drain false bottom.

I have thoroughly enjoyed this 'make' and will be making a Kingspan cover for the stainless steel lid before my first brew.

I'll report on how it goes.

Graham :cheers1:

If they say money cannot buy happiness - then explain motorcycles and beer! :thumb:
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Pakman
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Re: Make you own Thermopot Mashtun

Postby BigYin » Sun Jan 14, 2018 13:28

Really nice build :thumb:

Just a thought/question - if you were to cut a hatch on the base of the outer pot underneath the central drain pipe connector, would that have made the setup easier, and also allow access in future should a leak develop?

Probably too late for your build - and I'd accept the chances of a leak developing are probably slim - but might be a worthwhile consideration for anyone else considering this?
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Re: Make you own Thermopot Mashtun

Postby Pakman » Thu Jan 18, 2018 21:04

BigYin wrote:Really nice build :thumb:

Just a thought/question - if you were to cut a hatch on the base of the outer pot underneath the central drain pipe connector, would that have made the setup easier, and also allow access in future should a leak develop?


Yes, that would be a good idea apart from the thickness of foam that I would lose in the base, this would reduce the thermal protection. :nono:
As it turns out, I brewed with it a couple of weekends ago when the ambient temperature was 3C (the joys of outdoor brewing) and it worked quite well although lost 2 degrees more than I wanted over 90 mins. I've now created a custom lid and wrapped the outside with four layers of silver bubble insulation I found hiding in the shed. Hopefully give it another go this weekend. :pray:
Graham

If they say money cannot buy happiness - then explain motorcycles and beer! :thumb:
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