Irish Bokmini build

Vapor, Liquid or Cooling Management. Flutes, plates, etc.

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atticpc
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Posts: 62
Joined: Sun Jul 27, 2008 11:21 pm
Location: Ireland - The West

Irish Bokmini build

Post by atticpc »

A few months I set off on the process to build a Bokmini. This is now up and running successfully. I took some photos of the process - not as many as I had intended - but I got some so I wanted to document the process. Thanks to the forum for all of the help that I got leading up to this build. In particular I would like to mention Hookline and Pikluk's posting on his bok build at http://homedistiller.org/forum/viewtopi ... =17&t=5829.

I am lucky in that my now retired father trained as a fitter and turner in the days when engines needed to be re-bored every 10,000 miles. If you didn't have a tool to do a job well then you went off and made the tool. Very useful guy to have around. I think that things would have been much more complicated without him. When I had all of my parts collected I mailed him a print out of Pikluk's posting along with a few other bits and pieces. One of the things that I sent on was a photo of Hooklines's double coil cold finger condenser. I got a call a few days later. He wanted to know how long the coil should be as he had made up a 12" coil. Said that 6" would be better so off he went and did that as well. As a result I never did manage to actually see what he did bending the coil but I put together some photos anyway.

This is a photo of the manderal that he made to bend the inside coil.
inside manderal.jpg
Image of the manderal to bend the outisde coil.
outside manderal.jpg
This is the outside manderal set up to bend a coil.
manderal setup.jpg
The coil bending in process.
Turning a coil.jpg
The finished coils.
Finished Coil.jpg
I ended up with two coils - At a water flow of about 1 litre a minute the small one will almost knock down 2800 watts. If the water flow is turned up it dows. I have no idea what the large coil is capable of.

The coil is closed off on top - but it just loosely sits on the top of the column so there is no possibility of a pressure build up. One of the nicest things about these coils is the cap. I could not manage to buy anything - so my dad made the cap out of a piece of an old copper hot water tank. The copper in the tank would be about .8 mm thick. I don't understand the process but on his wood lathe he turned a bit of wood to be the same diameter as my pipe. He then heated up the bit of copper plate and spun it onto the bit of wood. I would really have liked to see this.

So now the most complicated bit has been completed - we have a working coil. Onto the boiler. As per the normal process this is a beer keg. In Europe the standard kegs seem to be the S? type. These have a threaded screw in the column - so I wanted to use this. As I was unable to get the nice copper threaded fittings that the guys in the US use I opted for slip fittings.

Keg top
Keg top.jpg
Keg connector components.
Keg Connector components.jpg
So what you see in the image above is the stainless steel threaded piece that holds everything together in one of S type kegs along with a 1.5" to 2" slip fitting connector. My symplistic mind said - "My brother has a tig welder - he can weld those together and the job is done". I was told that would not work. (though there is a recent posting that has said you can tig copper and SS using a silocone bronze rod). So what dad suggested was to mill out the centre of the screw fitting and then press the copper slip fitting into that. We could then use some soft solder to complete the joint. That almost worked!!

There was a sharp little crack when we pressed in the copper slip fitting - the SS screw had cracked - bugger.
broken connector.jpg
All however was not lost. Out came a stainless steel electric welding rod. There was a single buzz - I thought that he was just testing the arc - nope - connector welded. Back into the lathe.
skimming connector.jpg
This is what we ended up with.
completed connector.jpg
Now - onto the rest of the keg. This is what needed to be fitted.
Keg Components.jpg
We have 2 1500 240V elements, a 1" SS connector, 1/2" connector and a 1/2" valve to drain the keg.

The holes were drilled using standard bimetal hole saws. They were not expensive and came from Aldi - a cheap German supermarked on a special offer.

This is the keg with holes drilled for the elements.
Keg with drilled holes.jpg
The secret to easy drilling of holes in SS kegs. Some 40 year old cutting compound.
cutting compound.jpg
I won't say that the SS cut like butter - but it certainly put up less of a battle than I had expected.

So now while waiting for my brother to arrive with the Tig welder (great to have family) time to build the column. We used a miter box to cut the slots. It can't go wrong that way. You do need to be really careful to make sure that you get the orientation correct though or you could easily end up cutting you slots going the wrong way. That would not have been pretty.

Cutting the slots.
Cutting the slots.jpg
Completed slots.
completed slots.jpg
Plates - made from a bit of old copper hot water tank. Nice as the copper is only about .8mm thick it fits into a single saw blade cut.
Plates.jpg
They look a bit scruffy but work just fine.

This is what the inside of the head looks like looking down at the bottom plate
Completed Head 1.jpg
The completed pot
Pot.jpg
Pot top with connector in place - just screwed in with a little PTFE.
Pot top.jpg
Pot still mode - this is while using the head and a 16" column.
pot still mode.jpg
Short Reflux mode - using the head and a 36" column.
short reflux.jpg
Tall reflux - using head, short 16" column and 36" column
Tall Reflux.jpg
All connections are slip fittings. They are sealed using a few turns of PTFE and then a wide rubber band (as per the PDA1) to keep the PTFE in place.

As the voltage in Europe has standardised on 230v I actually get about 1400 watts from the 1500 watt elements. So the heat up is done on 2800 watts. Stripping mode is short column on 1400 watts. Pot still spirit run is on short column at 700 watts (both elements in series).

I have done two reflux spirit runs. Both the pot and the column were insulated and I was in tall mode which gives me a 4.5 fool column. I did one at 1400 watts at about 500 - 600 ml take off per hour and one at 700 watts at 400 ml take off per hour. Starting off with low wines of 38 - 40 % the distillate came out at about 93 - 94%. I'm a bit disappointed with this. I really wanted to get up to the mistical 95.5%. I'll get there eventually.

So - that was my build - hopefully I didn't bore anyone too much. Happy distilling.
rad14701
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Re: Irish Bokmini build

Post by rad14701 »

Nice build review, atticpc... I've been trying to remember who all I know that has lathes so I could whip up a few mandrels myself, but not for use in the lathe, but in a jig and probably wooden mandrels... Great work...
minime
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Re: Irish Bokmini build

Post by minime »

Outstanding documentation, A pleasure to read and review. Your Dad is the kind of guy I'd love to meet. Hat's off to him :D
punkin
Master of Distillation
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Location: Northern NSW Oz Trail Ya

Re: Irish Bokmini build

Post by punkin »

Very nice post.

Did ya temp correct before your reading? Like you i think it should perform better, one of the reflux guy's will no doubt come to your aid with a simple fix.... :wink:
atticpc
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Joined: Sun Jul 27, 2008 11:21 pm
Location: Ireland - The West

Re: Irish Bokmini build

Post by atticpc »

Hi Punkin, Minime

Yah - I re-took my readings the following day when everything was at room temp - so they should have been about 19 degrees Centegrade.

One thought is that given the column is made up of 3 seperate pieces it may not have been a vertical as it should have been. It would have been pretty good - but not perfect. Is this really vital or a nice to have?

Yup - dad is pretty cool. Funny how you get to realise how cool your parents are when you grow up and have kids of your own. You end up hopeing that you are as cool as they were :-)
rad14701
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Re: Irish Bokmini build

Post by rad14701 »

With a long reflux column like that you may need more than 1400W to get the output you are expecting... Sounds like you're running without a controller and, if so, they can be of great help... More heat will yield more reflux which will yield higher ABV at a greater rate... Hey, maybe 1600W - 2000W would get you where you want to be...

Also, make sure you have an adequate vent hole in your column cap... The better the condenser section can breath, the better it will perform...
Last edited by rad14701 on Sun Dec 07, 2008 2:43 pm, edited 1 time in total.
HookLine
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Re: Irish Bokmini build

Post by HookLine »

Nice work, atticpc and dad.
Be safe.
Be discreet.
And have fun.
decoy
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Re: Irish Bokmini build

Post by decoy »

thanx atticpc, nicw work and well documented..

its made me think about a few more things to do..

cheers..
rockystill
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Location: Colorado

Re: Irish Bokmini build

Post by rockystill »

Hey atticpc,

I know this thread is old...I hope you're still lurking around. :)

I have a Guiness keg too (Type U) and after my very brief foray into angle grinding (didn't go well), my plan is to flip the keg and use this threaded column as a drain. But I wanted to attempt this without any welding on the bottom. I'd like to find some kind of 2" to 1" reducing nipple, then I can use some standard parts with a ball valve for that drain.

But I'm not sure of the thread specs on this keg. ID definitely looks like 2", but is this a NPT thread? I've googled around but can't find anything.

Image
Last edited by rockystill on Thu Aug 09, 2018 8:51 am, edited 1 time in total.
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Jimy Dee
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Re: Irish Bokmini build

Post by Jimy Dee »

Hello, u in our emerald Isle? If so, any where down south? I would really like to befriend some one near by. Jimy Dee

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