To The Point - Aluminum Monocoque

Orange Bikes started producing frames way back in 1988, and have been doing things differently ever since. Eight years later, when bicycle production was heading East, Orange decided to bring it back to home shores and produce frames in the UK. The X628 frame in 1996 paved the way for what would come later and was thrust into the limelight by a young American named Missy Giove. Since then, subtle refinement and gradual evolution of a proven design have been Orange's hallmarks with that thinking producing multiple World Championship, World Cup and National titles across the world.


What is aluminum monocoque?

Aluminum monocoque is a structural approach by which a frame is produced from aluminum alloy sheet. A single, external, aluminum shell forms the main structure and provides the structural support any load placed on the frame. It’s worth pointing out that aluminum monocoque encompasses a wide variety of different techniques that can produce a similar result. True aluminum monocoque arguably only exists in rocket construction and most bicycle, automotive, marine and aeronautical applications are closer to semi-monocoque as they use multiple monocoque structures to create the end product or internal structures within the outer shell/skin.

Do you use a specific monocoque technique?

All our monocoque frame parts are produced by folding aluminum sheet using a shaped vertical press. The press-heads determine the angle the metal is folded at and dictates the shape of the tube created. It is possible to hydroform aluminum monocoque parts to produce a bicycle frame. We use our current method of monocoque construction owing to our expertise and background in producing frames the way we have done since 1996. We produce the vast majority of the frame’s component parts via a single process rather than a mixture of different techniques.

Why have Orange decided to use this process?

Use of monocoque allows the creation of a bike frame with a reduced number of stress points and allows stresses to be dissipated more evenly throughout the frame.


What materials do you use?

6061-T6 aluminum makes up the vast majority of our monocoque construction. Compared to other tempers of the same grade and other grades of aluminum alloy, 6061-T6 exhibits a better combination of higher strength, better workability, higher corrosion resistance and is more easily welded. 6061-T6 is also one of the most common and widely available grades of aluminum alloy which helps keep supply consistent and costs down. 7000 series aluminum is generally cheaper and is more easily welded, but is heavier and isn’t de-stressed by a post-weld heat treatment which is an important factor for us. 6061-T6 produces the lightest, strongest frame compared to any other grade of aluminum for our given construction technique.

How does the process work?

A single sheet of 6061-T6 aluminum alloy is loaded into a turret punch to cut out the required pieces. We produce as many of a single piece per sheet and the programmes reduce wastage where possible. The flat pieces are not inherently stiff but are easily folded. Minor folds increase the stiffness of the cut pieces exponentially. A downtube, for example, is folded several times from the horizontal until its sides almost touch and the increase in stiffness is dramatic. Aluminum hardens more when worked than other materials such as steel, and this part of the process sees it worked several times. Once the individual pieces are cut out, they make their way to the welding floor where the individual components are TIG welded together to create the outer shell. Almost all the parts for producing a front or rear are produced in this way. Anything that requires a finished edge (dropouts, shock mounts, bearing housings, etc...) are produced by a laser cutter or CNC machine off-site. Like in aerospace and automotive monocoque designs, we use structures within the outer shell to add strength to the outer shell and to better resist torsion. This internal structure is best exhibited in the rear swingarm where parts cut from different thicknesses of aluminum sheet are welded in to provide support in crucial areas. After welding, the front and rear triangles make their way to an alignment table before heading off for heat treatment that restores the material’s temper (T6) lost during welding. This process removes the stress from the frame and ensures consistency of the material properties throughout. The frames are aligned once more after returning from heat treatment.

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