Vyrus, why a slooping?
BEAUTY AND TECHNIQUE
A bicycle is an object of technique and emotion. The emotion is transmitted by aesthetic and technical solutions chosen for its construction: their essential structures illustrate the production technique. From these, the slooping design is used in a majority of cases as a simple aesthetic alternative to a bicycle plan more than a century old. This traditional plan consists of the classical frame with a seatpost used for connecting the saddle to the frame itself. This answers to a “traditional aesthetic rule”, developed over the time and grown to be a primary condition for the bicycle dimensions.
If we agree to this traditional aesthetic rule, a bicycle is believed “good and beautiful” only if some of its components are in a reciprocal position and dimension.
A slooping design somewhat modifies this rule. Born in the beginning with important technical criteria for the fulfilment of almost all kind of biker measurement need with few frame sizes, has been reutilized almost exclusively for the construction of bicycles with the seatpost more jutting out, a condition deemed fundamental for the bicycle “beauty”.
We need to consider that the lengthening of the seatpost projection usually implies some drawbacks. On the saddle is approximately applied 30% of the reaction force of the push on the pedal and the saddle is the primary responsible of our comfort. The seatpost jointure is usually achieved by a mechanical binder working on a restricted segment of the surface. A longer leverage (the seatpost) will certainly worsen the energy transmission: there will be more stress on the frame and amplified anelastic vibrations. Again, because it’s longer, the seatpost will amplify the road asperities transmitted to the saddle in a direct proportionality way, diminishing the comfort.
AN INNOVATION HISTORY
With his Vyrus frame, C4 proposes a solution to the road frame, incorporating the seatpost in the carbon monocoque main frame, developing a monolithic assembly of a big visual impact and with unique technical qualities.
Already in the past this technical solution has been utilized for other bikes, the forerunner was the Phirana, pioneering prototype of chrono bike exhibited at the start of the 1985 Giro d’Italia. It was based on a carbon monocoque frame with some remarkable technical solutions for that time. Between these the front wheel with a greatly arched special profile and the frame prolonged to the saddle with a winged portion of the frame itself. The saddle was connected to the frame by a very short seatpost allowing only a minimum of linear adjustment needed by the biker, at that time the wonderful and never forgotten Roberto Visentini.
Vyrus carries on this construction plan adding the cherished comfort, thanks to the section of the shaft round and not winged and to its single-piece monolithic construction like all C4 frames. This monolithic construction lets the creator, in possession of necessary knowledge and experience, to diversify with effectiveness different portions of the main frame carrying out dissimilar requirements.
Thus in the Vyrus frame, as on all C4 frames, its designer Marco Bonfanti sought to exalt performance, persuaded that the better thing for a carbon structure is to give it an elasticity differentiated in the various portions, following his knowledge, developed from the exclusive experience in planning and building carbon monocoque frames since 1986.
A basic consideration on which sometime there’s some puzzlement is the necessary discrimination between frame and bicycle. The frame is not the bike and, contrary to common belief, technically they’re two things well apart.
For common biker point of view this distinction between main frame and bicycle affects two primary factors, the first being bike resistance or better rigidity to the torsion, and the second, biker’s personal measurements.
TORSION RIGIDITY
Bicycle fluency is an essential issue for the performance. If its wheels are not perfectly lined up there are immediately running frictions abating velocity, thus frame and fork resistance to torsion are essential aspects. It’s in their ability to maintain the wheels lined up the true secret of an excellent bicycle.
A bicycle assembled with a reduced height frame will worsen its stiffness to the torsion. This is an applicable consideration if are fixed in space the details where are applied the forces acting on our bike, that is saddle, handlebar and pedals. In the same conditions, supposing non deformable elements and identical positions in space of saddle, handlebar and pedals, a bicycle with a smaller frame will have lower resistance to the torsion than another bike with a bigger frame. Or better, the smaller frame will be more stressed therefore will be more distorted under strain. This an unpleasant result because the primary function for a frame is to keep the wheels lined up: it’s in this way that it’s possible to achieve running fluency. This is a simple physics application discovered by Archimedes more than 2000 years ago: he said, “Give me a fulcrum and I shall move the world!”. Now, this law applied to a bike frame bring us to consider that a larger base (the larger frame) gives us more stability to stresses. In any case, all agree that in a frame a bigger diameter main tube increases torsion rigidity in a bicycle: the bigger diameter augments the inertia momentum of its section. The same happens for the frame measurements: the bigger the frame the bigger the inertia momentum.
In the Vyrus frame, the tubular sections making the frame have been deliberately enlarged so to ensure to the bike, with their high inertia momentum, torsion rigidity very very high, even with a slooping frame. The section replacing the seatpost has a diameter of no fewer than 40 mm, so developing a stable elasticity for the comfort. In the same time giving the sturdiness and torsion rigidity needed for high performances.
Using a slooping project for the Vyrus frame allowed to the designer the increasing of the distinction between elastic reactions in different portions of the frame, adapting them to performance and comfort, better than it’s possible with a traditional frame project with its classical top tube in a horizontal arrangement.
Performances are improved because the connection between the stem and the pivot of the rear wheel is more direct. To its rigidity provides the large diameter of the tubular portions and the subsequent volume connections between the frame constituents.
In the Vyrus frame the stem is higher than in a normal frame of the same dimension and this increased height produces a superior sturdiness in its steering portion. This happens because the head tube binds the fork: it’s from it that the road strains, through the rolling bearings in the headset, reach the frame. More distant the bearings are, bigger will be the torsion load the system can bear. Furthermore, a higher head tube permits the handlebar assembly with fewer adapting rings.
BICYCLE PERSONAL MEASUREMENTS
Bicycle measurements are surely the more controversial dispute in the bicycle world. To a single requirement, that is to a single biker, different producers offer personalized frame measurements. Yet the bicycle use is the same; there should not be good reasons for dissimilar interpretation. In reality the bicycle is utilized with several positions during its use: the road slope having the bigger effect on these positions. A slope variation changes the weight distribution on the saddle and on the handlebar. The biker thus needs to find a new balance in the pushing on the pedals and achieves it moving on the saddle. To these movements on the saddle contribute also other causes like the fatigue accrued, the amount of energy we’re in that moment applying and wind state, never forgetting that this one represents by far the bigger opposition to our moving forward.
The biggest misunderstanding is produced by common belief that frame measurements are bicycle measurements. In reality no one can take without proof a decision about a bicycle height. This height is directly obtained climbing in the saddle and adjusting its elevation. Now, the fact that the frame under the biker has a specific height means only that the seatpost is visible for a few centimetres: it’s an effect of the applying of the traditional aesthetic rule we spoke about before. This height is due to, other than to our personal measurements, even to the kind of saddle, to the stuffing of our pants, to our pedals, to the shoes we use and to our usual ankle articulation extension. The alterations due to these factors expose how absurd is to affirm that a particular frame height is “custom”, meaning a technical measurement. A demonstration is the fact that a bike saddle has always to be fine-tuned. It is possible the production of a bike with this predefined height but only knowing the height of a previously well adjusted bike. In no sport where exists an interaction between man and equipment there’s the possibility to evaluate the man and to bind the relative position. Not even in F1 where, with a lot of money, they take measurements of all things, exists a different alternative for selecting the correct distance between pilot seat and pedals than shaping it to the person who thus chooses how to interact with the item. Someone perhaps believes that it’s possible to take measurements of himself and from this decide within millimetres accurate regulations for seat position, pedal or wheel distance for a new car? How much backache…
Why this happens? Because interactions with equipment gives to the user “personal feelings”, that, being exactly that, feelings, can be transformed in millimetres only with a measurement of the object, not the other way around.
A biker interaction with his bicycle takes place through the saddle, handlebar and pedals. The frame between them is not even touched for the period of its use, there’s not a direct interaction. It’s easy to understand how, established in the space saddle, handlebar and pedals measurement, it’s possible to obtain our personal bike measurements, independent from the frame. If we need a frame respecting in the bike that traditional aesthetic rule, we’ll have predefined frame measurements in a wide enough dimensional range. This range is wide because the traditional aesthetic rule has not exact and well-defined dimensions; it’s an aesthetic effect, wide because the bike use positions are changing as we’ve seen before.
In the Vyrus frame, the measurement for the saddle height is executed only if the customer specifies the distance between the crankarms centre of rotation and the top central point of the saddle plane. It’s possible to adjust it only for a height of about 15 mm for personals adjustments of future saddle, shoes and pedals replacement.
In the Vyrus frame the distance between saddle and handlebar changes in a deliberately progressive way. The Vyrus distinctive saddle tube inclination and the fact that it’s noticeably not aligned compared with a traditional frame, allow saddle height positions progressively changing, compared with a traditional frame. This distinctive inclination and not alignment are due to an analysis of saddle, handlebar and pedals measurements obtained from hundredths and hundredths of finished bicycles. This analysis highlighted how the modification in space of these elements follows a constant progression, identifiable in the directrix where Vyrus saddle tube is positioned. It’s so possible to obtain a frame with a high adaptability to personal measurements, clearly better than a frame with a classical design.
FLUENCY AND VELOCITY
It is perhaps not widely known that a road bicycle is the mechanical device that, propelled only by human energy, generates the maximum velocity. Obviously, different bicycles give different performance, with consequent different velocity. Technology, materials, dimensions and manufacture quality, all impact on the bicycle performance. The biker applies his own energy through the traction on the handlebar, the saddle support and the push on the pedals. The “machine” bicycle converts this energy in rotating movement by the rear wheel that, thanks to the tire friction with the ground, permits movement and thus velocity. From physics textbooks we learn that the friction coefficient is always minor than one in bicycle tire: this means that the rear wheel is always skidding, a little, but skids. This skidding is what has to be reduced for getting back efficiency and with it velocity.
Energy application by the biker in a pedal rotation is not constant but has a maximum and minimum points because of crackarm mechanism geometry: thus while pedalling there are incessant changes between a maximum and a minimum on energy transmission on the rear wheel. With the maximum push there’ll be a maximum in the rear wheel skidding resulting in a minimum of performance. That is, we’re pushing ourselves, our legs are turning fast but the bicycle covers not so much ground. If instead we’re pedalling on a Vyrus frame, it will automatically settle the issue thanks to its extraordinary elasticity. It has been created for working like a big rigid spring: it will bend in an elastic way in the maximum energy application instant, reducing the force (torque) applied to the rear wheel, reducing so the skidding on the ground and increasing the bicycle performance.
The energy increase accomplished by the frame during the push on the pedal in the maximum thrust phase is returned by it in the minimum thrust phases. The frame itself increases thus the energy in a moment of the pedalling cycle when the rear wheel is in the minimum point and can transmit to the ground more torque without noticeably increasing the skidding. The carbon and epoxy resin composite produced by C4 has a hysteresis loop very narrow. (The hysteresis for a material is how much energy itself uses for a deformation if cannot give back). Our hysteresis value is next to zero and this tells us two things: first, that energy absorption by our frames while deforming is returned practically in its totality in the “useless” phases of our pedalling; the second one, ensures an exceptional resistance to stress by the material, a feature the always offered by composite. To pedal on a Vyrus monocoque carbon frame, stamped in one single piece without joints, planned and manufactured so to work like a big spring, gives the guarantee non only of maximum performances thanks to better movement efficiency by the rear wheel, but ensures also an incomparable comfort exalted by the saddle tube, developed to its maximum.
Those extremely stiff and break-back carbon frames are not surely C4: they are frame manufactured with wrong planning theory. Vyrus is not produced with glued joints, it’s one single piece. Glued joints have good endurance to stress only if the joint is extremely stiff, with much reduced elastic movements between connected components, whereas a fracture is almost assured: to avoid it the price to pay is backache. A spring is never jointed, glued or welded, it’s always a one single piece. Not all in a Vyrus frame is in carbon composite: for those little parts where to insert the front and rear wheels the material used is made of exceptionally high quality aluminium alloys (avional 2024). It’s common knowledge that light alloys are basically plastic materials with a reduced elastic field, with a very wide hysteresis loop. Because the little details assembled with those alloys are so tiny they cannot ruin our frames general elasticity. By contrary they work very well for those mechanics assemblies for which they are employed and for which instead the carbon is not suitable. Carbon, even if costs 20 times more than the aluminium alloys we buy, is not apt to be drilled, threaded and mechanically compress by bolts. For this reason those particulars are essential for assembling the bicycle.
The idea “the stiffer it is, the better it is” is an enormous technical mistake. A frame stiffer than wheel resistance will produce in them a massive skidding, with a dreadfully low bicycle performance. The purpose for good frame is to make a fast bicycle, not to be the stiffest under test. The Vyrus stiffness is the maximum allowed by last generation wheel.
From a cinematic point of view, a bicycle is a relatively simple item: two wheels, one for advancement, and the other for direction, without suspensions. There are not therefore alignment changes when moving. To obtain maximum fluency while changing direction, steering geometry must be neutral, nor over-steering nor under-steering. This so to avoid that, in the reduced contact zone between front wheel and the ground (a little ellipsoid), takes effect a lateral force factor generating an undesired friction and reducing both bike fluency and, significantly, bike roadholding. To fall while turning, perhaps in a slope, is not surely a happy occurrence. The pushing on the pedal, alternate and with a force application position lateral compared with the vehicle axis, develops a force component pushing on its side the bike. The right foot, pushing, moves the bike towards left, the left one pushes it towards right. The biker, for a straight advance, compensates this movement with a suitable little steering on the opposite side, lightly inclining the bike (for effect of the steering geometry, to every steering corresponds always a bike inclination proportional to velocity).
If the frame and the fork form an under-steering or over-steering bicycle we’ll run always with an additional friction, a little brake always engaged, even going straight. For this reason first thing we design, planning a new frame, is a steering geometry totally neutral. For performances this is important as much as the monocoque fabrication in a single piece or as the stamping technology. The Vyrus follows this design as all frames planned by Marco Bonfanti.
The chain on the bike is in an asymmetric position. Its maximum tension is over 1000 kg. Because of this 1000 kg, working in an asymmetrical way, the frames twists and thus the rear wheel alignment is lost: so ends fluency. It’s not possible to pretend those 1000 kg are nonexistent. In all its history, for counterbalancing this deformation, C4 has always planned and manufactured its frames with asymmetrical thickness and fibres direction. How much and where they are asymmetrical is a little secret C4 keeps for creating his very fast bicycles.
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