History and evolution of BikesIt is believed that engineers have been dreaming updifferent versions of bicycles since the 1500s.
According to IBF (internationalBicycle frame) iterations of bicycle frames had existed a long time before westarted using it as a mode of transportation. According to the data that hasbeen found it points to an Italian engineer named Giovani Fontana and creditshim for the beginning of what led to the modern day bicycle. Although to keepin mind what he had created some 600 years ago had very little resemblance totoday’s bicycle, it had four wheels and a loop of rope connected by gears. Some 400 years later the world as a whole faced a shortageof horses brought on by the eruption of mount tambura in Indonesia which led tothe ash cloud dispersing all around the world, the effect of this ash cloud hasbeen such that it lowered the global temp which in turn meant that cropsstarted failing around the world and animals including horses started dying. To battle the shortage of horses In 1817 Drais came out witha two-wheeled vehicle which came to be known all around Europe as the hobbyhorse. The hobby horse had been reported to have weighed in at 23kg, had 2wheels attached to a wooden frame, an upholstered leather saddle was nailed tothe frame in order for the rider to sit on and steer the vehicle with arudimentary set of wooden handlebar. This design of Drais had no gears nor didit have any pedals leaving the riders to push the device with their own feetwhile sitting down in a rather awkward position.
Fig 1Soon after it made its introduction in UK, A British coachmaker by the name of Denis Johnson concocted his own version. According to theNational museum of America by 1820 the popularity of these bikes had faded awaydue to the respected countries banning the bikes in sidewalks. This was due tothem obviously being a danger to the pedestrians as they were unsteer-able.In 1860 bikes made a comeback due to the addition of pedalsand fixed gear system, although as to who to credit for this modern alterationsis still a topic that is covered in ambiguity. The ride was so bumpy that thefirst riders brave enough to go on one of these titled it the bone shakeralthough the more famous name is velocipede. During these period the wood wasgoing out of fashion for being the main choice for a bike frame and Metals werestepping in, this transition allowed for the bike frames to be built more elegantlyand metal being stronger than Wood and thus allowed the usage of less materialfor a stronger frame which reduced the frames Weight and allowed it to bemanufactured more rapidly and reduce production cost, this ultimately increasedthe Market size of bikes. A German engineer named Karl kech claimed that he was the firstto attach the pedals and gear to the hobby horse although he was unsuccessfulin his claim and the patents in fact went to a French carriage maker named PierreLallement. Fig2 Few years afterwards another problem arose, theconsumers wanted to go faster.
There were 2 different options to take in orderto make the bike go faster either change the gear ratio of the bike and makethe drive train indirect or change the size of the wheel that the pedal wasstuck to. Herein lied a problem in the fact that although the direct drivetrain was a revolutionary step forward for bikes it meant that the only way toincrease speed for bike was to increase the diameter of the wheel the pedal isstuck to. Increasing the diameter of the bike would mean that the bike wouldtravel further per revolution that the wheel takes, but engineers had anotherproblem to tackle in this field as well, the wheels of that time were too heavyto increase it any further.
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In 1869 wire spoke tension wheel was created, this kickedoff the start of larger front wheels for bikes. This new invention was so goodthat it has been reported that front wheel of bikes around that time hadreached up to 5FT. This was named “Penny farthing” although it was claimed byadverts of that time the bike was lightweight it still weighed in at staggering40 pounds. Fig 3 Although this was a very simple solution to a complicatedproblem, it caused yet another problem. The riders themselves were falling offof the bikes and the height being so great from the ground fairly few of themwere getting injured which led to the market size remaining rather small due tothe fear factor it came with. The Engineers went back to the drawing board andquickly realised that the only way to improve this situation is to go towardsthe route of using an indirect drivetrain. This allowed for the wheels to bereduced dramatically while keeping the speed of the bike similar. And thus the “Safetybike” was born.
Needless to say the name came from the fact that how safe itwas to ride in comparison to its predecessors. The safety Bike was so popularthat to a certain extent it had managed to liberate the women of that time, asmany of them were able to, for the first time in their life travel independently By 1885 all the major bike producers of UK had producedsafety bicycles which consisted of the diamond shape frame. Diamond shape frameThis is by far the most popular design when it comes to bikeframes, the design have been serving its purpose for a very long time and it isstill recognisable from the time of its advent in 1990s when it was firstintroduced for a “safety bicycle”.
The diamond shape frame gets its name due to the fake thatit has double triangles for a frame which makes it sort of look like a diamond.As mentioned it is still recognisable which only means that the frame has beenlargely left unchanged. This is due to the fact that the double triangle shapeis one the strongest shape one can form.
Over the years it has proved to theworld of its great usage of material which leads to less wastage when formingthe frame, it can also take a heavy beating and still be rideable. As Paoloexplains that structurally speaking the frame is rather extraordinary he alsogoes onto say when one observes engineers in their pursuit of strong structuresthey tend to almost always fall back to the triangle shape and the diamondshape frame essentially being a triple triangle structure, it’s no surprisethat it turns out to be a strong structure.The diamond shaped frame allows for the bike to change itsconfiguration by altering its geometry with only a few tweaks. For example givingthe frame a relaxed angle and longer wheel base allows riders to ride theirbike for longer for comfortably while tightening up the frame geometry willgive you a road racer in essence.
Fig 4The triangles consist of the parts below:Head tube- It is the tube that sits at the frontof the frame and is usually of circular shape. The front fork steerer tube ismounted within it. As can be seen from the picture below the tube has ballbearings in-between the steerer tube in order for it to be turned and issecured in place via the usage of Bolt, star nut or bung Fig 5Top tube – This is what determines how far awaythe seat tube is from the head tube. Needless to say the length the top tubethus plays major role on the reach of the Bicycle .
The length of the Top tube determines whatthe bike may be used for, as an example a shorter top tube is used in conjunctionwith a slightly raised head tube when it comes to cyclo sportive bike. Fig 6 Seat tube: It connects to the other side of theTop tube. According to bike cad “The effective seat tube length is the distance between the bottombracket and the point at which a virtual horizontal top tube would intersectthe seat tube.” According to this explanation, the seat tube is what keeps thebike frames front triangle and back 2 triangles together in a single structure. Fig 7 Down tube: This is what connects the headtube and bottom bracket and thus one can imagine the tremendous force that isapplied to this particular tube.
It experiences the torsion of twistinghandlebars at its junction with the head tube and the pedalling forces at thebottom bracket. As explained by Timothy Jon; the down tubes length is theresultant of the designer’s decisions on the length of head tube, seat-tube andtop tube.Fig 8 Chain stays- It connects the down tubeand seat tube via the bottom bracket shell to the bottom of the seat stay viathe rear fork ends. It runs parallel to the chain and its length is measuredfrom the centre of the bottom bracket to the centre of the rear axle.James Olson a leading bike designerexplains in the article Buyers guide: Bicycle geometry: “The purpose of the chainstay is to lock the rear axle in place”.
Every time the rider delivers power tothe pedal of the bike, due to the force incurred the bike tries to twist therear axle. Again, much like the seat and head tube,the shape and length of the chain stay wholly depends on the function the bikeplays. Fig 9 Below is a standard bicycle size geometry whichwill be used later on in order to design the bike frame on CAD. Inseam (In.) Height Shoe size Frame size cm (c-t) Top tube cm (c-t) 36 6’4” 11.5 62 59 35.5 6’2.5” 11 61 58 34.75 6’1” 10.5 60 57.5 34.25 6’0” 10.5 59 57 33.75 5’10.75” 10 58 56.5 33 5’9.5” 9.5 57 56 32.5 5’8.75” 9 56 55.5 32 5’8” 9 55 55 31.25 5’7” 8.5 54 54.5 30.75 5’6” 8 53 54 30 5’5′ 7.5 52 53 29.5 5’4.5” 7 51 52 29 5’4” 7 50 51 28.5 5’3” 6 49 51 Fig10: Bicycle size geometry chart
