Non Laverda - Setting water and oil hoses to a particular shape.

G

ghwallice

Hero member
Location
Ipswich
I'm trying to replace oil and water hoses on my car, and they want many dollars. Some are not available as aftermarket fittings.

As a sparky I quite often cold bend and heat bend conduit, and with my stuffing around in the shed, Perspex, plastics, blah blah blah. Not that I really understand the composition.

BUT, If I buy a straight length of oil resistant hose, say 25mm ID, put an internal bending spring through it, set out a pattern on say a block of wood, is there any process I can use that will "set" the hose to the shape?

Regards, Greg

 
I think those pre-formed hoses that you can get for car radiators, heater pipes, etc. are moulded in that shape. I don't know of a process to put a permanent bend in a large diameter flexible hose. Happy to be told that I'm wrong though.

On occasions when I've wanted a pre-formed hose that's unobtainable, I've rummaged through the pile at Supercheap Auto and found something that's near enough. Sometimes you need to cut and join them with a piece of straight copper pipe and a couple of hose clamps to change the angle or length, or both.
 
Greg, plastics have a memory, depending on the cross linking of molecules at manufacture, if you add heat to the plastic, in most cases it will try to return to its original state.

In some plastics, it can be air blown to a larger dia than extruded, and stretched in length, also at the same. If you add heat to the finished produuct, it will attempt to return to its extruded size, read shrink in both MD and transverse directions. It?s how shrink film and tubing is made.

Consider a length of cable shrink tube, in this case, it has MD (machine direction, length) that has not been stretched, but blown to a larger dia than when extruded.
So add heat to the tube and it will, in the main try to return to the same dia as extruded, but not shrink in length (much)

Rubber is very similar. There are two ways rubber is set to curves, bends etc.

Moulded in a form or, mandrel bent. The mould is easy to understand, but mandrel bent rubber tube is, of course, done one a mandrel bender, but, it is recoated with a hot rubber coating, and let to cool.

You may remember seeing rubber radiator hoses, on old Bedford?s and tractors and the like, which looked like they were wrapped in a protective cloth/rubber compound (basically vulcanised to the original form ...... that?s a typical mandrel bent hose. With the outer wrap acting as the memory agent.

Basically, you are fucked.

If you need, such specific bends, you could well consider inserting a copper tube of similar OD, to the ID of the rubber tube, and have that mandrel bent.
 
chrisk said:
Basically, you are fucked.
Click to expand...

Yep, that's about where I got to!

Thanks for the indepth response though. I've been heat bending electrical conduit, Perspex, ect ect for years, and was wondering if there was a way it could be done with rubber hose.

Regards, Greg
 
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