a conundrum

littlefeller

littlefeller

Zorg Guru (IV)
British Zeds
The M44 Massive
Joined
Oct 18, 2015
Points
168
Location
evesham
ok folks i have a small problem. i need to fit a seamless tube inside another seamless tube which when fitted will be gas tight, now i cant fit an o ring as the tube walls are only 1.6mm thikness, now here is the question - the inner tube has an OD of 19.05mm and the tube it needs to go into has an ID of 18.96mm so how close does it need to be for me to heat up the outer tube and push the inner tube inside so as when it cooled it didn't deform the inner tube and allow gas to escape?
 
You lost me at seamless tube!
 
ok i will explain, the tube that needs to go inside the bigger tube is 19.05mm while the hole it needs to fit into is 18.96mm so is 0.09mm too small, if i heat up the outer tube it will expand enough for the other tube to slip inside but when it cools it will return to 18.96 so how much would it deform the tube inside?
 
the next question in anticipation of answer to the above is how do i reduce the size of the inner tube without the use of a spindle grinder (by hand :eek:) and still form an air tight seal to say 150 bar, yes i know im asking a lot here.
 
This is a suck it and see scenario. You only want to go 9 hundredths of a mill so I reckon it is achievable. Get some bits of tube the same as the ones you want to work with and experiment.
 
That is never going to work, to be gas tight, you need a female connection with a gas tight seal in the male connection.

vamtop-3d.jpg
 
Ok, so you're heating the larger tube. Chuck the smaller one in the freezer then try it.

Tony.

ps. It works with gudgeon pins.
 
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the gas seal is achieved with a rubber o ring attached to a valve that is in the smaller tube, this valve will be moved forward to allow this seal to pop out of the end of the smaller tube, I will then use a slightly larger seal on the valve, the seal cant go backwards as it is now has the smaller tube edge right behind it, so I suppose it does not have to be that cock-on, but at the same time I don't want a pigs ear.
 
littlefeller said:
ok folks i have a small problem. i need to fit a seamless tube inside another seamless tube which when fitted will be gas tight, now i cant fit an o ring as the tube walls are only 1.6mm thikness, now here is the question - the inner tube has an OD of 19.05mm and the tube it needs to go into has an ID of 18.96mm so how close does it need to be for me to heat up the outer tube and push the inner tube inside so as when it cooled it didn't deform the inner tube and allow gas to escape?
Click to expand...
Sorry I need more wine before I contemplate this one :drinks::drinks:
 
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