Unsticking aluminum tubes

I need to lengthen a solar blanket roller, to reuse it on a larger swimming pool. The roller is two aluminum tubes, about 4" diameter, end to end, linked by a third tube inside, ridged so that it touches the enclosing tubes at about 8 points. How to extend this telescopic tube sysem? Hammering on the inner tube (reached by a crowbar) earns me half an inch a time, but I am apprehensive about building up a burr on the aluminum, that would jam the tube permanently.
Is there any useful trick to unstick telescopic tubing?
--
Don Phillipson
Carlsbad Springs
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Don,
Rather than a crowbar use an appropriately sized tube. A tube that slides freely into the 4" tube and makes good contact with the inner tube is what you want. Have someone hold the outer tube while you whack at a scrap of 2X4 placed on the end of driving tube.
Dave M.
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This is (sort of) what I am trying to do, hammering on a T-section garden stake, while the outer tube is braced by bungee cords to a trolley, and the far end free. Air pressure cannot be used (many screw holes in both tubes). If I can lay hands on a propane torch I shall try warming up the outer tube, in case it helps. Thanks to all for suggestions.
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Don Phillipson
Carlsbad Springs
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On Sun, 28 Apr 2013 18:00:40 -0400, "Don Phillipson"
Shouldn't be hard. Anyone who can afford a pool can afford a propane torch. Lots of uses.
I shall try warming up the

Sounds very likely to me. I think you need a helper, maybe two. Two to pull and one to heat. If possible, pull before the inner tube heats
MAPP gas is hotter than propane, but in this case I don't think it will matter.
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chill the smallet diameter tube and heat the outer tube should loosen them up somewhat. How much is the overlap, inches or feet or yards or what?
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On 4/28/13 11:48 AM, Don Phillipson wrote:

Could you seal the ends of the tubes? If so, maybe a little bit of air pressure in the tube plus percussive maintenance. A reminder though. It's pounds per square inch and 3.14 X the radius squared at the ends of the plugged tubes.
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Oiling?
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