Minimum radius for bending 10mm microbore

[Kev888]

Hi,

Does anyone know the minimum radius you can reliably bend 10mm micro bore to (without heat, external bending springs or mini benders)? I'm thinking of making a small coil by wrapping the pipe around something cylindrical, but I've not had reason to test the limits before.

Cheers,
kev

[bigdave]

If youve got a 20m length you could perhaps cut a 1m length and keep bending until it creases or splits?

[Kev888]

Yeah, unfortunately though I don't have it yet, and (amazingly) seem to have run out of all my off-cuts - was trying to decide on the options before I buy it.

I just found this heat exhanger build though - seems there are ways of going very, very small. Would be a bit of a faff, but at least it looks like if all else fails there's no danger of buying the tube and then being unable to make the coil.

Cheers,
Kev

[WishboneBrewery]

I made this http://pdtnc.wordpress.com/2009/06/17/e ... t-cooling/ which was last used as a comedy trumpet at our house warming party! No other use for it.
Its probably just wrapped around, 10mm copper is very soft when you first buy it but you'd need to secure the thing your are wrapping it around and the end of the 10mm copper, I would guess you could form it around a 22mm or 28mm pipe without too much deformation.
You could clamp both the bending mandrel (28mm pipe) and the end of the 10mm in a vice, so tight as to destroy the parts in the vice which you would later cut off

[Kev888]

Thanks for that - got some microbore now so I'll give it a try.

Cheers
Kev

[jmc]

Hi

With domestic copper pipe its common to use a bending spring inside the pipe to stop it kinking.
I know thats not suitable for micro-bore copper, but I read somewhere that using the same priciple that you could use a water to support the pipe rather than a spring.

Sounds wierd, It works on the principle that water is incompressible, so you'd need to seal ends and fill pipe totally with no bubbles.

Another option may be to use sand inside the pipe to support it.
See http://www.ehow.com/how_4814553_bend-steel-tubing.html

If this works for steel tubing it should be a breeze for micro-bore copper.

ATB
John

[Kev888]

Yeah, you can get external springs for microbore instead, but I think with the sort of length I'm thinking of (its a long narrow IC) they would be quite fiddly and annoying to keep moving along - in my experience they can take a bit of aggro to free each time as the tube compresses up against them. So maybe the water or sand approach that you mention, or the salt in my link above, would be easier.

Anyway, initial success to report: I've just made a 26-turn coil of about 13cm internal diameter once it relaxed, by wrapping it around a norman-sized Co2 cylinder. It doesn't take much to kink it at that sort of radius so it took a little practice but in actual fact was no biggie in the end and didn't need any extra support. Thats the outer coil, and about 11m long in total so would be sufficient if I don't manage more. However, I'd like to make an inner coil too, and that may well need sand or something - its probably going to have to be wrapped around something like a wine bottle. Maybe tomorrow though, think its time for a beer and a hobnob now ...

Cheers
kev

[Gricey]

I have a microbore SS chiller from Hamstead Brewing Centre. Considered a second coil but I like the look of Jamil's whirlpool chiller - needs a pump but seems like a seriously good idea. Have you not thought about that? If you have, and have binned off the idea, interested why (as I'm always planning my utopian fixed installation........)

[Kev888]

I have a microbore SS chiller from Hamstead Brewing Centre. Considered a second coil but I like the look of Jamil's whirlpool chiller - needs a pump but seems like a seriously good idea. Have you not thought about that? If you have, and have binned off the idea, interested why (as I'm always planning my utopian fixed installation........)

Ha! - great minds and all that. Yes I was thinking of recirculating wort between the IC coils - though haven't decided if this will be a true wirlpool or not. I've only got a pump rated to 85 degrees C, so had initially been thinking of a plate chiller before the pump, but following polymoog's recent thread I'm now going with a smallish IC (which i personally prefer) and just waiting a bit for the boiler to cool enough before I begin recirculating with the pump.

The inner coil is partly intended to speed up the bit before recirculation begins and partly to double the flow through the IC - in the future I may want to pump water through it instead of using mains pressure, and most of the cheaper/quieter water pumps prefer low pressure and higher flow rates.

Cheers
kev

[Kev888]

Okey dokey, some progress to report. I managed to wrap the inner coil around a wine bottle this morning. It took a surprising amount of effort, although that may partially be due to having started last night by 'emptying' the rather nice Gran Reserva first - nothing but the best for this IC

Here are the coils and their 'formers'. Got slightly carried away with the smaller one so its taller than I intended - it'll be about 6.5m long when finished, making 17.5m in total when combined with the bigger coil:


And here are the two coils nested - notice how the 10mm microbore flattened; its fine in this case but I don't think I'd fancy going much tighter without something to support the tube:


Now I have to decide if I'm going to stretch the coils out vertically to let wort between them, or keep them tight and recirculate wort between the two. I had intended the latter, but now am considering that means more tubes to sanitise (since my pump won't take boiling wort) and that defeats one aspect that I like about ICs.

So I'm either going to stretch the tubes and have some sort of electric stirrer (or maybe an electric system of jiggling them up and down in the wort), or have a minimal 'nozzle' at the bottom of the IC that will completely immerse and so self sanitise without extra attention. I'm going to have to sanitise some hose separately anyway, as that'll be used for emptying the wort after cooling, so the recirculation side of the piping is okay.

Hmm - any thoughts on stretching and mechanically stirring vs keeping them compact and recirculating between them?


Cheers
kev

[trucker5774]

I have used silica sand inside the pipe to allow tight bending You could also try 8mm

[WishboneBrewery]

Nice looking bit of work

[Kev888]

I have used silica sand inside the pipe to allow tight bending You could also try 8mm

Yeah, think I'd have had to do something like that if I went any tighter; sounds similar to the water and salt ideas. I did consider a third coil too actually, but you wouldn't get much total length in something that small a diameter so I decided to call it quitts. I guess 8mm would have been easier too, but I wanted the bigger bore of 10mm in case I decide to later pump water through the IC with a lower pressure pump.

Nice looking bit of work

Ta! Its certainly more attractive looking than my recent efforts with flattening a hot water cylinder coil :-/

Cheers
kev

[bosium]

Nice work, I wish mine came out that nicely! How did you get the coils so uniform? Did you anchor the microbore to the former somehow?

[Kev888]

Thanks! I think it was by wrapping the coils tightly against each other that helped keep them uniform (ish). Previously I've wrapped them more openly and they've been a bit random; this time I thought I'd wrap them tightly and then stretch the 'spring' out afterwards - only now I can't decide if I should still do that or just leave them tightly wound and recirculate.

For the bottle coil I gaffa taped the end of the pipe to the bottle to begin with, and after a few turns was able to release it and hold the coil rather than the bottle to wind on more pipe - needed a lot of gripping force/effort though. For the cylinder I just bent/kinked the pipe around the valve to stop it slipping - in retrospect perhaps not the safest; there's no guard around the valve of that cylinder and the springiness of the tube kept trying to tipple it over. In both cases there was a bit of a ragged tail to the start of each coil that I sawed off afterwards

Cheers
kev