Bokakob VM Modification

[Anavrin]

Hi Guys

I've decided I'm going to take a hacksaw to my Boka and fit a VM takeoff just below the slant plates, I've just placed an order tonight for all the copper pipe and fittings.

It's going to have a tee piece in the main 54mm column with a 28mm take off to a 1inch gate valve, from there I will turn down 90° and reduce to 15mm, this 15mm pipe will have a 28mm jacket around it as a Liebig (length yet to be decided)

The plan is to be able to take off the fores and heads using the output from the boka slant plates, then open the VM valve for the hearts run, as the VM output size is 1inch and the main column is 2inch I will have a reflux ratio of 4:1 in VM mode, from the research I've done the reflux in the main column should be enough to suppress most of the tails so it will simply stop producing when the tails start to come through (someone please correct me if I'm wrong).

It will also work as a much quicker pot still without the cooling coil and slant plates, I will make the boka section removable and just fit a solid cap for stripping runs.

I'll start work soon and post my progress on here.

[Capt-Cudellez]

Hi Anavrin, I run a VM/LM combo, that does what you are planning. LM to take off the heads then switch to VM for hearts collection. (Click for a bigger pic)



The benefits are you don't foul your product condenser with heads. The VM is such a good design that some folks would argue that the amount of smearing in minimal anyway and this is a lot of additional build effort for little improvement. But its fun to play about with different set ups.

As for VM stopping producing tails, well...yes and no.

The VM works by the fact that alcohol vapour is heavier than air, so by the time the vapour is about 40% it stops outputting and goes into 100% reflux. So with a VM you will never extract every last drop. BUT......
The difference between hearts and tails is only 0.1-0.2 oC of vapour temp. I can pull really foul concentrated tails at over 94%. I don't want that in my product condenser either.

I don't think these very concentrated tails really clean up with re-running, so I choose to keep them in the boiler, and flush them to waste when emptying the still.
If you wanted to collect every last drop, you could switch back to LM to do this.

One other thing, you are talking about capping the still and using the VM condenser as a pot still. I'd consider only doing this when if you remove the valve. It would be easy to have a brain fart and have the valve shut by accident, which would be a disaster.

Why not have the VM/LM section remove as one piece, and have a separate pot head, you can use the VM condenser on both?

[Anavrin]

My last run on my BOKA has decided for me that it's now time to do the VM mod, I'm gonna start the build pics on this thread.

Hopefully make a start today

[Anavrin]

Ok I've officially divorced my Boka and done it Henry VIII style by chopping its head off!
See below

Laid out


Cut off the output the liebig cooler as I wanted it shorter anyway


This is kind of how I want to to look




I will fit a stainless gate valve between the two 28mm brass fitting in the VM take off arm.

[Anavrin]

Got a bit more done before I had to stop to watch the darts final on Sky, I debated for a while wether to keep my original boka head but decided in the end to chop it off and start again.

Got my jig out for the slant plates that I made last time to cut some new slots at 30°


Here's the new one next to the old section I cut out, last time I sandwiched the plates inside a coupling section but this time I'm just going to solder them into the sides of the pipe.



Here's the plates soldered in place, they should look a lot tidier after I've filed them flush with the column and polished it up.



Here's a bottom view of the lower slant plate, I've made sure I cut into the plate so the point where the liquid overflows is lower than the edge of the plate, this is something I missed when I made my last one, think it was spotted by YHB on my last build post and it's the main reason I decided to make a new boka head.



So far so good, can't believe how much I've got done in a day, I better get my stainless gate valve ordered, I could be running a junkahol run this time next weekend >:D

[Anavrin]

Couldn't help but get a little more done before bed

I've cleaned up the solder from around the slant plates and given it a good polish with a stainless steel pot scrubber, I've also soldered a 6mm tube for the temp probe and a short bit of 8mm tube for the output tube, can't believe how well it's cleaned up.

BOKA PORN!!!

[Almanac]

The cap on your coil looks like it's completely closed with the tails from the coil fitted through it using compression fittings or is there an opening in the cap?

AM

[Anavrin]

Yeah this one has three 4mm holes in a line between the two compression fittings, I might do away with compression fittings and solder the tails into the cap so there's no chance of a leak.

[Almanac]

I just cut out a 1" disc in the cap on mine and just threaded the tails through that. I was a bit paranoid about any chance of even the slightest pressure build up being even remotely possible

AM

[Anavrin]

Got a bit more done last night




Now I can see what it's gonna look like :-)

[Anavrin]

FIN

[Boozoid]

Looks lovely and neat.
I'm interested in how you get on with this.. my Boka might get the same VM treatment.

What plastic is the seal made from in the ball valve?

[Anavrin]

Hi Boozoid

The seal in the ball valve is PTFE, that seems to be the standard for stainless steel valves, it is very stiff to turn though! Might need an extention tube for the lever and some good oven gloves to hold the main colum as I turn it.

[Capt-Cudellez]

..... it is very stiff to turn though! Might need an extention tube for the lever and some good oven gloves to hold the main colum as I turn it.

------------------------------------

That is the down side to using the cheaper ball valve over the gate, you need to hold the column steady as you turn it, with the gave valve all the force is centered and you can do it with one hand.

Good job on the column btw, I really don't like valves on a pot still, but it depends on how you are attaching the cap? Or how is that thermo probe sealed, if you accidentally closed the valve would the cap or probe "pop"?

[Anavrin]

Hi Capt

Yeah the top section, be it boka or pot top will only be held in place by a silicone sleve around the outside of the column, so if ant pressure did build up, it would pop the top off before anything catastrophiphic could happen.