Bending Oval Tube......... 1

[bisonlee]

Does anyone out there know how to bend oval tube. i am considering using it on a frame and wondering if i can use the old fill with sand and heat method or should i pay someone to do it for me. thanks

 

[evelrod]

Everybody seems to be avoiding this question. Give it a try on a test tube (pun) and you will see that it works quite well as long as the bends are kept very shallow. Once you crimp the test tube, you will know how far you can go. Just be careful and heat a large enough area of the tube and remember that the sand will be VERY hot when you pour it out. Pro shops like H & L Metals of Long Beach can handle the job if your reluctant to give it a try. I am sure that motorcycle shops that fab their own frames would be a source, also.

Rod

 

[bisonlee]

thanks for that. i will give it a go. i am in australia so it might be a bit hard to get to the shop you mention

 

[amorrison]

This might be worth a try...
Locate in the tube at the bend location a piece of (rectangular cross section) wood - locating with string if it is deep in the tube.
When the tube crushing occurs the minimum "diameter" tube collapse will be the thickness of the wood.
Abandon the wood in place if you can't get it out.

 

[okeng]

Anyone ever tried freezing water in the tube and then bending it, relying on the ice to support the inside? You'd have to NOT plug the end so as not to split the tube. This came up in a discussion I had a while back trying to figure out how to bend square tube without crushing it (or buying an internal mandrel). Haven't had time to try it. Obviously, you would have to bend it cold.

 

[aussieconrad]

is it possible to get round tube bent, then to compess it to the appropriate oval?
if the compression was done in a steel jig so that the extents of the jig were "sloppy" to start with then as the tube deformed the widths of the jig set the longer dimension of the oval it should work ok.
we found getting mandrel bends done cost AUS$15 a bend in newcastle (not at an exhaust shop, but with a proper mandrel bending place). and only took a day (dropped off, picked up)
the only problems are that the bend radius would have to be at whatever their die was and obviously this method could take a bit to set-up

what u think?

 

[jcai]

GOOD MORNING FOLKS
AM IN AUSTRALIA - SEEMS LIKE THIS COUNTRY HAS LOTS OF BUDDING ENGINEERS WILLING TO TRY JUST ABOUT ANYTHING !
AM OLD AIRPLANE ENGINEER/ELECO - BUT ALSO OVERHAUL / REFURB OLD MOTOR CYCLES FOR HOBBY - MANY YEARS AGO WHEN I WAS DOING INSTALLATIONS OF PVC TUBE - WE USED LONG SPRINGS + LENGTH OF WIRE PRIOR TO BENDING WITH SOME HEAT - I WONDER WOULD THAT WORK ON OVAL TUBE - I PRESUME YOU MEAN STEEL ? PROBLEM MIGHT B ETO GET IT OUT AGAIN - YOU DONT SAY WAHT O.D. /I.D. OR WALL THICKNESS OR MATERIAL SPEC. ?
FURTHER BACK I WATCHED THE GUYS ON RADIAL ENGINES FILLING ALUMINIUM ALLOY HYDRAULIC PIPES WITH FINE SAND AND PATTING WITH TABLE TENNIS BATS TO ENSURE THE PIPE WAS PACKED SOLID -THEN HEATING WITH BLOW TORCH AND FINALLY BENDING AROUND TIMBER MOLDS . REMEMBER THE TUBE NOT ONLY CAN WRINKLE ON THE INSIDE OF THE BEND -IT ALSO WILL STRETCH THINNER ON THE OUTSIDE SO IS WEAKER THERE - STRUCTURAL INTEGRITY MAY SUFFER - ALSO CORROSION PROFF THE INSIDE BEFORE WELDING ETC. BMW R-60 FRAME ETC IS BUILT WITH OVAL AND ALSO TAPER STEEL TUBE - TRUST THAT HELPS - J.C.

 

[GhostDon]

There are commercial metal alloys specificaly designed for this purpose. They are "Fusible Alloys" containing Bismuth, Cadmium, Lead, Antimony, and other metals that are alloyed to form a solid inside the tube for bend support. The nice thing about these products is that to remove the alloy after bending you submerge the part in water or oil below the boiling of water where they melt and can be poured out for reuse. One manufacturer is "MCP" located in Great Britain. I hope this is what you are looking for.