Engineering Report the Bicycle

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Engineering Report

Recumbent Bicycle

Reynolds 853

The Reynolds 853 is a steel alloy created by Reynolds Cycle Technology, a manufacturing company based in Birmingham, England. It is composed of several elements solely including iron, carbon, chrome and molybdenum but also includes silicon, copper and manganese.

The Steel’s physical properties include a stiffness level similar to mild steel. With the addition of chrome and molybdenum the steel can be strong enough to butt or be thinned down in the middle, thus making the material lighter.

It has an excellent strength to weight ratio obtained from heat-treatment used in its formation. The heat treatment used for this steel does not use quenching rather uses air cooling or air hardening. This results in the steel having a finer grain and raises the yield strength in the material. Subsequently due to air hardening the material’s strength increases as the materials temperature cools. This unique air hardening property of Reynolds 853 provides additional stiffness through reduced micro-yielding at the joints, allowing stiffer products with excellent fatigue strength. This gives it an added resistance to all loads put on it and a resistance from damage.

In assembly Reynolds 853 steel is suitable for TIG welding and brazing, using lugged or lugless construction. The production process ensures tight tolerance, gauge tubes. The strength to weight ratio of 853 is close to that of quality titanium frames. It however can not be brazed.

The cost of the material can be relatively cheap once equipment used for making the product is obtained, i.e. casts, assembly lines, elements, etc. Maintenance to production equipment is the only other factor needed to take into account

Reynolds X100

Like the 853 steel alloy, Reynolds X100 is a product of Reynolds Cycle Technology, based in Birmingham, England. It is an aluminum alloy composed of both aluminum and lithium. The material was derived from aerospace projects and commonly used for custom bike builds but has limited production due to the uncommon availability of the raw materials.

Behind steel, aluminum is seen as the second most common material and is most likely to overtake steel as most popular material used for frame design. It is 12% stiffer and 20% lighter than steel in its most common bike frame design. Aluminum is rust proof and dampens vibrations 20% faster than steel.

With the addition of lithium to the alloy its strength and stiffness properties significantly increases while its density decreases. As a consequence to the increased stiffness the frame has very little flex. The power produced by the rider is transmitted very well however it poorly absorbs shock from rough roads and coarse chip bitumen. The frame is recommended to be used by sprint cyclist and not so much the average rider.

In order to obtain the strength and stiffness that is provided by the material the aluminum must be very thermally treated after being welded, then quenched, and then artificially aged before assembled. To further increase the stiffness and decrease the weight of the material the diameter of the tubes of the frame can be increased while maintaining the wall thickness, making a tube that is eight times as stiff, but only twice the weight. Though using this method runs the risk of being unstable if the walls of the tubes are thinned out to much.

The cost of the initial materials is relatively cheap but in the case of mass production the availability of the materials may be too small. Also the precision of the above method with heat treatment may both cost money and time and may be too much trouble for mass production.

Titanium Alloy

Titanium alloys are metallic materials which contain a mixture of Titanium and several other elements such as aluminum and vanadium. Most titanium frames are 3% aluminum and 2.5% vanadium though a stronger alloy, 6% aluminum and 4% vanadium is increasingly used.

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