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Thermal Syphon And Melting Copper


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#1 tennentslager

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Posted 07 February 2016 - 09:38 PM

I want to make a hot tub for my hut garden.
Attached File  IMAG0997.jpg   27.79K   10 downloads
Pretty confident about making the tub...
Not sure about the heating of the water. Does this design stack up?
The basic idea is you contain a wood fire inside a doctored gas canister. The top of the canister has a pipe/ heat exchanger set up. I don't know how to do this yet.
The you tube way looks beyond me so reckon I'd have to pay someone to do it for me.
Questions...Will it work? Will it get hot?
I don't mind having the fire going for a few hours as I'm sure you'll agree the hot tub is for having a nice smoke in the evening watching the stars so Plenty of pottering time to stoke the fire.
Any thoughts most welcome.

#2 PeterW

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Posted 07 February 2016 - 09:46 PM

Quickest way is not to use copper...

Make a black iron manifold out of some 12" sections of 25mm pipe and some tees/elbows so you have a rough grill and then tack weld this to the back of the gas cylinder so its in direct contact. Bottom pipe then connects to bottom of the tub, top goes back in about half way up (stops you scalding yourself !

Even quicker is submersing the entire gas cylinder into the hot tub .... http://www.forestfla...d-hot-tubs.html

#3 tennentslager

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Posted 07 February 2016 - 10:04 PM

Thanks Peter,
Great link but...there's the fun of making it and I'm more in the one thousand budget rather than five.
:)

#4 PeterW

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Posted 07 February 2016 - 10:43 PM

I agree...!

Its on the list for when everything is done....

DIY Snorkel Stove is whats needed...now where is Onoff when you need some fabrication...

http://www.cowboyhot...s/IM000412a.JPG

#5 Nickfromwales

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Posted 07 February 2016 - 11:04 PM

It'll work ok, just need to be careful not to overheat it :blink:
I take it you understand about it being gravity circulation, so height of heater / tub is critical
Regards, nick.

#6 Onoff

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Posted 08 February 2016 - 07:28 AM

Ah! The garden hot tub, it's on her list.

My tentative musing was GRP over EPS. Thinking on the lines of a dead level central pole with a shaped hot wire cutter you rotate to form the nicely curved seating area. Then lay it up in GRP. Or render.....

Cheap bubbles.....big vacuum cleaner?

Oddly enough for a number of years I've worked pretty closely with the NZ company who make the critical sheet metal components for this where you might get some ideas:

http://www.kiwitub.com/

EDIT: One of the best hot tub builds I've seen was what I can only describe as a "stoners" build. Take two old sofas and set them facing each other about 2' apart. "Cap" the ends with a couple of sheets of ply. Put two ratchet straps round the "assembly". Drape big, heavy duty tarp over the lot and fill with water. Tarp settles to the shape of the sofas and everything pushes out tight held against the ratchet straps.

Edited by Onoff, 08 February 2016 - 07:34 AM.


#7 Triassic

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Posted 08 February 2016 - 07:35 AM

Or save your time and buy one http://www.bidspotte...ogue-id-bp10880