Materials On Bicycle Frames Engineering Essay

Materials On Bicycle Frames Engineering Essay


Throughout history the construct of the bike has been used and manipulated with stuffs from all over the spectrum exercised. In recent old ages, machining methods have become advanced plenty to pull strings all different classs of metals, from the most popular being steel, to debasing Ti based metals, nevertheless non merely metal stuffs are being used. Carbon fiber, a generic term of the composing of C fiber weave and epoxy rosin, is the universe ‘s most recent popular stuff to be used on practically everything in the automotive industry, from gear boss to the complete human body on the Porsche Carrera GT for illustration, which is easy spread outing into the bike market and beyond. Nowadays bike makers have an evident limitless array of stuffs, fall ining procedures and completing techniques, which should theoretically be able to bring forth the “ best ” bike frame on the market. Taking modern twenty-four hours complications into history, the “ best ” bike frame stuff ( s ) are possibly inappropriate in footings of fabrication monetary value and market sale value. Despite this, utilizing Cambridge Engineering Selector ( CES Software ) , by puting up technology restraints, looking at material choice indices and lading forms on constituents ; a individual “ best ” stuff is to be determined.

Merchandise Definition

As non all bikes are aimed at the same user market, with the purpose to plan a motorcycle for different intents such as ; mountain motorcycles, metropolis motorcycles, leisure motorcycles, route motorcycles, race motorcycles, etc. the restraints and aims of how the bike frame should respond under force per unit area during usage are different. It is because of this, the “ best ” stuff can differ from bike type, and hence a class of motorcycle must be specified.

The bike class to be specified is a little sub-category of route motorcycles called fixed gear motorcycles or “ fixies ” . This class of motorcycle has late sprung up all over the universe, with its major rebellion taking back to Brooklyn, New York ; nevertheless a cult following has arisen in major metropoliss around the Earth. This type of motorcycle and cycling manner lends its beginnings back to track racing, where the same manner of motorcycle is used in the Olympics and other motorcycle featuring events. The fixie manner has become popular on the route for its legerity and acceleration about town for transposing every bit good as its fittingness association for of class merely holding one cogwheel. This sub class of motorcycle is frequently used for portion diversion, portion fittingness usage, yet chiefly as a agency of conveyance in and around town.

This recent rebellion has uncovered many different stuffs of motorcycle frame, from old 1980 ‘s path motorcycles made from steel to late manufactured aluminum and C fiber composite frames which are used on this type of motorcycle and manner of siting.

Figure 1. Charge Plug TI. Charge ‘s Ti fixed gear double butted frame with labeled frame constituents [ 1 ]

S-Works Langster Frameset

Figure 2. Specialised S-Works Langster. Aluminium frame with “ C monocoque ” fork. [ 2 ]

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Figure 3. Many fixie motorcycles adopt vivacious coloring material combinations, an development that has come about by art and media in modern metropoliss. [ 3 ]

Materials Selection Possible Constraints

The frame constituents will be capable to different forces, of which several will see the same force depending on different loading conditions. The place tubing will see changeless compaction forces from the weight of the rider every bit good reactions from route forcing back up towards the rider, whereas the down tubing will see tensional forces keeping the tender country together with the fork assembly ; nevertheless braking will give rise to compaction. Other characteristics such as the place corsets will see changeless compaction and sidelong emphasis from the braking mechanisms, of which stiffness is a critical belongings of the stuff. Young ‘s modulus or stiffness is besides really of import in the design of the forks due to instantaneous braking promoting the forks to flex.

Figure 4. Tension and compaction forces moving on motorcycle frame


The denseness of the stuff will impact extremely the efficiency and feel of the motorcycle when ridden. More energy is required to brake or speed up the motorcycle that has a high denseness frame, accordingly doing the motorcycle difficult to command and maneuver. A lightweight stuff is critical to make the ideal bike frame to better maneuverability, braking and acceleration public presentation. This is why a restraint of denseness is to be limited at 5000 KG/M^3. This encompasses common frame stuffs such as aluminum and Ti metals. [ 4 ]

Young ‘s Modulus

The stiffness of the frame is critical to forestall fictile distortion of the frame when ridden over obstructions, nevertheless if the frame is excessively stiff at that place will excessively much quiver from route surfaces. A restraint of stuffs above 30GPa are acceptable for the intended usage, nevertheless stuffs above 400GPa are considered excessively stiff and will ensue in a harsh incontrollable bike. [ 4 ]

Tensile and Compressive Stress

Tensile emphasis occurs on many of the constituents of the bike frame and is a common neglecting belongings by overloading the frame which accordingly makes it a high precedence factor. Materials above of tensile emphasis value 300MPa and above are acceptable. Compaction is besides a major emphasis force abundant in the bike frame, in topographic points such as the rear place corsets and place tubing from gravitation drawing the weight of the rider toward the land. Poor compressive forces will interpret into a muss of buckled piping. [ 4 ]

Output Strength

The output strength determines the sum of force required to plastically deform the stuff of which the stuff is for good deformed after giving. This can be applied to sudden impacts or over burden of the frame which can take to failure of the frame, possibly ensuing in hurt when ridden. The higher the output strength, the higher force the frame will be able to defy which is favorable in frame design. [ 4 ]


Elongation relates to brittle and ductile belongingss of a stuff, where high per centum elongation leads to ductile belongingss and low per centum elongation leads to brittle belongingss. If a stuff is excessively brickle, it theoretically could fracture into little parts which are to be avoided when cycling. It would be preferred for the stuff to plastically deform to a big extent earlier failure as this will forestall hurt if a sudden halt is experienced. A stuff with a really high per centum elongation is besides to be avoided as the frame will non maintain its form and deform with the weight of the rider. Materials below 40 % elongation will supply favorable elongation belongingss. [ 4 ] [ 5 ]

Fatigue Strength

The maximal cyclical emphasiss can be examined and applied to a bike frame straight, miming the insistent emphasiss when ridden. This can therefore generalize the life of the bike frame given the sum of insistent burden applied when ridden. [ 4 ] [ 5 ]

Tortuosity Stress

Tortuosity burden occurs upon acceleration of the bike where the frame is moved from side to side under the sidelong forces applied by the rider from the torsion applied. The usual sidelong burden on the frame is transferred to little longitudinal burden. The tortuosity capablenesss of the stuff must be taken into history which besides extremely affects the connection processes of the bike frame. [ 4 ] [ 5 ]

Material Objectives Set-up and Index Selection

To happen the “ best ” stuff for a fixed cogwheel motorcycle frame, the chief aim is to prioritize technology public presentation ; cut downing weight, increasing stiffness. The legerity of the frame is the chief feature of which turning reactions, acceleration and slowing public presentation are critical to a successful fixed cogwheel motorcycle to be used in and about town every bit good as for preparation intents.

The indices used to input into CES will specify stiffness-limited design at minimal mass.

The frame features that are tensile loaded, making a tie between two other frame beams will utilize the index Young ‘s Modulus / Density, E/ I? . Increasing this index will turn up suited stuffs that exert stiffness, combined with low denseness, nevertheless besides giving the best tensile belongingss.

The compaction index, for constituents loaded in compaction, is ( Young ‘s Modulus ^ A? ) /Density, E1/2 / I? will besides turn up the best stuffs for that type of lading. For constituents loaded in flexing the index ( Young ‘s Modulus ^ A? ) /Density, E1/2 / I? , will besides be used.

For strength limited design, turn uping the best stuff for tensile strength before giving up and fictile distortion of the frame occurs, the index output strength/density, I?f / I? , is to be used. Locating the best stuff for compaction strength will besides utilize this index. For the seatstays and fork constituents, loaded in bending, the index I?f2/3 / I? will be used.

Maximizing these indices will turn up the best stuffs for each specified type of lading. [ 6 ]

Results utilizing CES

Function: Bicycle frame

Constraints: Must non neglect under rider weight and route reactions.

Aim: Overall mass of bike frame is to be reduced, without giving stiffness and strength.

Variables: Material pick, material subdivision form, completing techniques.

Before inputting restraints, the graphs of Young ‘s Modulus over denseness and output strength over denseness appear as follows utilizing instruction degree 2:

Figure 5. Young ‘s modulus over denseness CES.

Figure 6. Output strength over denseness. CES.

Inputting the restraints, CES outlines groups of stuffs that meet the restraints:

Figure 7. Young ‘s modulus over denseness utilizing restraints. CES.

Figure 8. Output strength over denseness utilizing restraints. CES.

CES package has outlined different stuffs from the groups: complexs, metals and metals, and proficient ceramics. These stuffs are:

Aluminum metals

Titanium metals

Beryllium metals

Carbon fiber complexs

Magnesium metals

Silicon based proficient ceramics

Aluminum metals

Aluminum metals are highly light and shows marks of high elongation, these factors direct aluminum toward being a good campaigner for a bike frame, nevertheless aluminum has a low immature ‘s modulus value and certain metals exhibit low tensile strength values. These belongingss may give the bike frame flexibleness, nevertheless current aluminum bike frames are surely non flexible as they tend to hold a larger diameter top tubing and general radii over the frame constituents to counter act this. The weariness values for aluminum metals are really low, which indicates that after a while the frame will check and neglect, which is decidedly something to avoid. Current bike frame makers use bordering engineering in aluminum frames to battle this, by increasing the thickness of the tubing at where the stuff is needed most. [ 4 ]

Titanium metals

Titanium metals are about double the weight of aluminum metals, yet around half that denseness of steel metals, doing up for this are the high tensile strength and Young ‘s modulus values which enable to border to be manufactured from dilutant tubing subdivisions than aluminum which cut down overall weight. The weariness values are besides high which means that the frame will last for a long clip. [ 4 ] [ 7 ]

Magnesium metals

Magnesium metals are even lighter than aluminum metals and have a somewhat better fatigue value. Magnesium alloys besides have a low Young ‘s modulus value, lower than aluminum which indicates flexible frame belongingss which will hold to be yet once more solved utilizing tube subdivision thickness design. Magnesium alloys look promising and have good belongingss that can be applied to a bike frame, nevertheless they have low corrsosion opposition which has to be overcome by surface interventions. On the current market, few frames have been made from the stuff as they tend to be really expensive. [ 4 ] [ 7 ] [ 8 ]

CFRP, Carbon Fibre Re-enforced Plastic

CFRP, a composite stuff, is lighter than all the metals antecedently mentioned every bit good as holding high a Young ‘s modulus, tensile value, and comparatively high weariness strength values. This stuff is presently being used all over the bike market, from purely track motorcycles to route race drivers, complete frames or portion CFRP frames, and constituents used in mountain bike off route frames. The modulus of the epoxy rosin is highly low, ensuing in a brickle stuff ; which accordingly affects the method of which the CFRP beds are applied. CFRP has good tensile belongingss, nevertheless non really high compaction or tortuosity belongingss, so the angle at which the C fiber beds are applied must be taken into consideration, otherwise turning decompression sicknesss could turn the frame into a fractured muss. This is besides apparent in the highly low elongation value, 0.032 % – 035 % [ 3 ] [ 4 ] [ 8 ]

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Figure 9. Multiple fractured CFRP frame. [ 9 ]

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Figure 10. Fractured CFRP fork. [ 9 ]

Technical Ceramicss, Silicon Carbide

Silicon carbide, unlike ceramics in general has a good tensile value similar to that of Ti, aluminum and CFRP, and a immature ‘s modulus value four times that of Ti. This implies that Si carbide has a positively good mentality on a perspective bike frame, exposing high weariness values and holding a somewhat lower denseness than Ti. Silicon carbide does nevertheless hold a low per centum elongation at 0 % [ 3 ] which boasts the possible for bring forthing a intercrossed stuff to increase this value. [ 4 ] [ 11 ] [ 10 ]


Beryllium is frequently used as an debasing stuff to increase hardness belongingss, nevertheless it besides has a really high immature ‘s modulus value and is lightweight. Beryllium could non be used to entirely fabricate a bike frame as it is toxicant, particularly with inspiration. [ 12 ] [ 5 ] [ 4 ]

It is seeable to see the groups of stuffs normally used on bike frames from the graphs produced ; nevertheless there are non any specific stuffs shown. Enabling instruction degree 3, the database of stuffs becomes more specific and stuffs that do non run into the restraints are ignored. By maximizing the indices, single stuffs can be identified.

Figure 11. Output strength over denseness utilizing instruction degree 3 CES, restraints and maximised indices set-up.

Figure 12. Young ‘s modulus over denseness utilizing instruction degree 3 CES, restraints and maximised indices set-up.

CES package has located Cyanate ester/HM C fiber UD composite 0A° lamina by maximizing the indices as the best stuff for a bike frame. The unidirectional lamina allows the tensile and immature ‘s modulus values to be unvarying within the stuff, instead than hold a directional flow providing room for failure by tortuosity. The composing of 30-40 % polymer and 60-70 % C fiber maintains a high degree of stiffness and fatigue strength from the C fiber and reduces the toffee belongingss of the polymer rosin.

The CES result may hold located the “ best ” stuff for a fixed cogwheel motorcycle frame, with the nonsubjective minimise the weight of the overall frame, without giving stiffness and strength, nevertheless fall ining procedures, surface treatments/coatings and forms need to be considered.

Joining procedures

Current CFRP frames are either manufactured by utilizing cannular Lugs of aluminum or Ti, and so pre-made CFRP tubings aligned and stuck into topographic point with farther layered CFRP and epoxy adhesives. The connection between the two different types of stuffs has led to corrosion and weakness, which has directed makers to make frames entirely utilizing CFRP. Continuous laminating can be used to cover a spindle of which the remotion of the spindle gives rise to a molded tubing or hollow subdivision necessary for the specified constituent. One method used to make low batch Numberss of CFRP frames is autoclave molding, which builds up the CFRP beds by manus, this technique creates a monocoque CFRP shell which has superior stiffness, strength and is highly lightweight ; frames lower than one kilogram have been produced. [ 8 ]

Shape Factors

Cyanate ester/HM C fiber UD composite 0A° lamina has a maximal form factor value for elastic bending ( Max I•eB ) of 12.3. By utilizing this value, the form efficiency can be compared against other stuffs finding if other stuffs exhibit better stiffness and opposition to flexing belongingss.

Using CES a graph can be drawn of Young ‘s modulus over denseness with the index I? /E1/ 2, which will demo the maximal bending stiffness whilst cut downing weight. As the form of the stuff is non fixed, in general stuffs used for lightweight structural aims require low I?/ ( I†eBE ) 1/2 values. The stuffs will be selected as they provide the best belongingss. [ 10 ]

Figure 13. Young ‘s modulus over denseness utilizing the index I? /E1/ 2 =C.

By comparing metals used often in the industry of bike frames against the CFRP based stuff CES located, it is possible to see the benefits of foremost the form factor attributed to aluminium, giving it good structural belongingss despite its low immature ‘s modulus value. However the lower value of the determined CFRP stuff means that it has better form efficiency and will hold better in service belongingss at supplying a lightweight stiff bike frame, resistant to bending forces.

The Ti, given its stiffness will be able to bring forth a lighter frame than one made of steel and aluminum, yet does non hold a better bending form factor shown by the aluminium metal. Magnesium, despite holding the lowest modulus has a maximal bending factor lower than the aluminium metal, which is one of the grounds why it is going an progressively popular base metal for bike frames. [ 10 ]


I? Mg/m3

Tocopherol GPa

I¦e Max

I? / ( I•e, max E ) 1/ 2

Cyanate ester/HM C fiber UD composite 0A° lamina





6061 T4 Aluminium





Titanium 3AL 2.5 Volt





Magnesium AM100A Cast T6





Hybrid Bicycle Frame

The utmost stiffness of the Cyanate ester/HM C fiber UD composite 0A° lamina bike frame will make a really stiff drive, of which the route surface will be felt through the frame to the rider. One manner to forestall this is to utilize larger or thicker Surs, which will cut down quiver, nevertheless will significantly increase clash and cut down top velocity and acceleration times. A method to cut down these jobs would be to develop a frame that utilised a twosome of stuffs and blended them together to give longitudinal damping belongingss yet maintain the transverse stiffness and lightweight belongingss. This could be achieved by utilizing Ti on the chief triangular frame due to its 5-10 % elongation belongings, highly high weariness, tensile and lightweight belongingss ; and utilizing the CFRP on the concatenation corsets, place corsets and fork constituents for its highly high form factor and flexing stiffness value. This will besides make a high weariness opposition of the frame doing it last for many stat mis of equitation, nevertheless jobs may happen with the connection of the two stuffs when utilizing acrylic based or epoxy gums to bond the two subdivisions together as this interferes with the construction and could take to corrosion or failure from lading. [ 8 ] [ 7 ] [ 6 ]

A intercrossed stuff could be answer to making the perfect motorcycle frame utilizing silicon carbide, B carbide and aluminum, besides known as MMC duralcan metals, or alumina B4C metals. Alloys utilizing these stuffs have already been created, doing usage of Si and B carbide ‘s mechanical belongingss and uniting them with aluminum ‘s structural advantages.


I? Mg/m3

Tocopherol GPa

I¦e Max

I? / ( I•e, max E ) 1/ 2

Alumina/50 % B4C complex





Duralcan Al 10-Al203





The aluminum carbide complexs exhibit good bending factor values every bit good as high Young ‘s modulus values, fatigue strength, tensile strength and really high compressive strength, which makes the material promising for usage as a bike frame.

Surface Treatments

Surface interventions such as anodising are common in today ‘s current bike market, for illustration on aluminum where the reactive surface is covered with an oxide bed and the thickness controlled utilizing anodising. This prolongs the life of the frame by cut downing the hazard of corrosion. Electroplating is besides used for corrosion opposition or to better hardness, this method is normally used on metals ; nevertheless non-metals can be plated one time painted with an electrically conductive stuff. This can give metals glistening mirror coatings, synthesising the expression of normally expensive stuffs such as gold or Ag. For metals and non-metals, organic dissolver based pigments are widely used to give the frame exciting colorss and coatings. Organic dissolver based pigments are normally applied to carbon fiber ; nevertheless it is sometimes preferred to demo the workmanship of the C fiber in its natural signifier demoing the weave form. [ 4 ] [ 10 ]


The best stuffs for a fixed cogwheel route motorcycle come in the signifier of C fiber re-enforced plastics ; this is because of the lightweight, high modulus frames they create. The form factor contributes extremely to the success of the stuff by making stiff cannular subdivisions that are immune to flexing and fictile distortion besides improved by their high output strength values. The tensile and compaction belongingss shown by the stuff are really high and work good at absorbing daze, administering the emphasis throughout the frame. The orientation of the C fiber is really of import as this affects the tensile and compaction values that the stuff can take before break in the longitudinal and cross waies, vital to the frame remaining in one piece when turning, slowing or speed uping quickly. A uni-directional laminate is preferred as the fibers provide optimal emphasis and strain abilities.

The metals mentioned provide lightweight solutions to the bike frame ; nevertheless each has issues, whether it is low immature ‘s modulus or weariness bounds that need to be addressed. These issues are normally solved by agencies of debasing or utilizing form factors to increase or diminish tube thicknesses or usage of butting and other connection procedures.