Tube Sizing for Model Applications

[derekwarner_decoy]

Hi PD's.....I cannot stay long as I plan to set a few rabbit traps to catch a few & make rabbit stew.....[things a tough in OZ with this financial crisis] 

OK - my question......why so many differing tube sizes?

1) Nick from Monahan uses 5/32" [3.98 mm] OD copper tube for steam inlet & outlet....but am not sure of the ID
2) Fabrice from Anton appear to use a combination of 3 & 4 mm OD brass tube for steam & water pilot pressure to the gas regulator....with 2 mm OD brass from the gas tank to the regulator....& into the burner...again not sure of the ID in each size
3) JMC I believe..... use the same sizings as Anton
4) Sandy from ACS nominates 1/8" [3.17 mm] OD copper tube ....heavy wall
5) John  [bogstandard] from memory has a preference for 1/8" [3.17 mm] OD copper tube ....heavy wall

Essentially we have three variants here.....[cold drawn seamless]

CDS brass in varying sizes
CDS copper in varying sizes
CDS copper in varying sizes which is also annealed that create those dogs legs [bent beyond belief] that we see

These are very complex questions ....consider a vessel steaming along [paddle-paddle-paddle] & then stop the vessel ....what happens to the steam in the line between the boiler & the engine...it wants to condense & loose all energy & then provide the engine with a gut full of oily water 

So whilst we could all enroll as mature age students @ University [again] & re-study Bernoulli & PD's [pressure drop]  ...is there any rhyme or reason for the selections?

For those that have four days off  ...............Derek 

[poodge]

I use 1/8th thickwall like John and Sandy,because it's so easy to get.Most car parts outfits will sell you as much or as little as you want(within reason).They also have 3/16th and 1/4",haven't seen any 5/32 though.
Hans.

[kiwimodeller]

Stewart Turner and Cheddar also used to use a 5/32 a lot of the time but I have no idea why - maybe just to make sure that we had to buy our fittings and tubing off them! I would have thought that copper was preferable to brass just from the work hardening aspect? In future Derek you are not to set puzzles like this unless you already know the answer! Ian.

[poodge]

Sorry,Ian,I should have mentioned I was referring to copper.Regards.Hans.

[bogstandard]

I use 3/32", 1/8" and 5/32" O.D. mainly, sometimes a bit of 3/16" and 1/4".

In the UK we have been using these sizes for many years to replicate the 'scale' look of models.

Copper tube is the ideal, plenty strong enough for what we need, a good range of sizes cheaply and readily available, and the most major thing, it is very easy to bend and shape into the shapes that are used on the 'real' things.

It seems that the mainland Europeans use mainly brass, which IMHO is totally the wrong material to use, it easily fractures when in a vibration producing environment, mainly because it work hardens under those conditions. It is a pig to bend accurately, and to small diameters, without wall collapse, and the material leeches out zinc under hot water and steam conditions, making it weak and liable to failure.

It might be that the mainland Europeans are too pig headed to use copper, because we were there first, and they are still a hundred years behind our modelling techniques. Plus it seems, copper is only mass produced in imperial sizes, and I am sure European modellers won't admit that imperial sized materials for making models is correct, it has to be metric to be any good. Their loss, not ours. You might find that if they did standardise to copper on the Continent, then it would be at 5/32", as that is almost exactly 4mm, and they could use that without losing too much face.

Bogs

[andy]

Hi
I use what I get. The ANton engine has the 3x4mm brass tubes. But the steam tube (source) of my DIESSEN engine as an ID of 8mm and exhaust of 10mm. That´s due to  the piston diameter of 19mm and 36mm.

Andy