By closing at least provisionally the section of the three patents filed by Aprilia regarding the aerodynamics of MotoGP, we shared with you a small discovery in another area…
Indeed, by digging around to find the patents themselves in order to read them, we sometimes come across more interesting things, even extremely interesting as is the case for the patent WO2024028318A1 published this year 2024 by the already known Marco De Luca associated this time with Germano Bergamo on behalf of Piaggio.
Marco De Luca, you already know, an engineer who worked at Lamborghini, Mercedes AMG and McLaren before taking over in 2019 at Aprilia as head of the department responsible for designing the RS-GP chassis, its aerodynamic development, engine and brake cooling, design of the snorkel, air box, exhaust system and fuel tank. In short, a size!
But if 3 patents had been filed in the field of the aerodynamics of the beast, until now nothing concerned the quite original chassis of the RS-GP, which we had nevertheless revealed exclusively on several occasions. The Aprilia frame (made of aluminum, the carbon version having never been seen...) in fact takes up the concept inaugurated by Suzuki, with bolted engine supports (today with 3 screws compared to 5 on the late GSX-RR ), and this, from 2017 (see here) then again in 2022 in a new version (see here).
But as we can see in the following photo, while Suzuki could change the rigidity of its frame by changing the bolted elements, at Aprilia we opted for another, more advanced solution: connecting said supports to the frame itself by tie rods. also called struts. But “intelligent” tie rods…
Let's be honest, the subject is so sensitive that some of our photos (not this one) were sent back to Noale, generating phone calls to kindly ask us to remove them, under penalty of harming the careless mechanics, which we we obviously did. But at the start of the 2024 season, the patent concerned makes the matter public, and our objectives will not fail to enjoy themselves at the first opportunity...
The Aprilia patent sheds light on some technical subtleties of MotoGP:
« The state of the art includes motorcycle frames made of aluminum or composite materials to meet the needs for lightness and rigidity. Motorcycle frames usually have a "U" or "O" shape to connect the steering column to the rear wheel swingarm. The frames also allow the anchoring of the propulsion engine. Typically, the engine is installed directly on the chassis.
In some chassis, the engine is installed on the chassis by means of brackets for rigidity reasons. The brackets are connected to the chassis by means of connection means and the engine is installed on the brackets. In this way, the frame stiffness can be adjusted and the longitudinal and lateral stiffness can be optimized. In practice, the rigidity of the supports is less, or in any case different, from that of the frame and allows twists and typical movements of the engine to be only partially transferred to the frame.
In this latter type of chassis, the supports are designed to have sufficient longitudinal rigidity to avoid the so-called “chassis closing” phenomenon, that is to say excessive advancement of the engine relative to the steering column during the braking. This phenomenon is even more noticeable on racing motorcycles, particularly those in MotoGP. In these motorcycles, the frames are extremely affected by the deformations caused by braking, which are much more powerful than those of normal motorcycles.
To solve this "frame closing" problem when braking, engine mounts are usually oversized, but this results in greater weight and a loss of performance, in terms of stiffness, in corners, as the frame becomes more rigid. in longitudinal deformations, but also more rigid in lateral deformations.
The aforementioned drawbacks of the prior art are now resolved by a motorcycle frame, which comprises a main body extending in a longitudinal direction and a pair of supports connected to the main body and configured to at least partially support an engine, wherein said framework includes a pair of spacers configured to be rigid in compression and free in tension. Each spacer is connected at a front end to the main body and at a rear end to one of said supports. The frame thus designed has greater rigidity. When braking, the mass of the engine tends to move forward, unloading its weight partly on the supports and partly on the strut. Conversely, during acceleration, the strut is free to extend and the engine only unloads its mass onto the supports.«
In this way, the pair of struts helps absorb the compressive loads acting on the main frame, while remaining unused and unimportant when loads, other than those of compression, act. These compression loads are mainly those that develop during sudden deceleration and braking of the motorcycle, and tend to "close" the main body of the frame, i.e. generate angular momentum clockwise in Figure 2. The function of the struts is to increase the rigidity of the supports during braking and to dissipate the forces mainly on the part of the main body which is close to the column of management. In this way, the motorcycle is more stable when braking, allowing the rider to enter a corner in a more fluid manner.
At the same time, the pair of struts is “transparent” in other operating conditions of the motorcycle, for example when cornering or accelerating, allowing labile deformation of the chassis and supports. In this way, greater flexibility of the frame is ensured, which is necessary especially in the acceleration or cornering phase. The flexibility of the frame allows more grip from the tires, and therefore more traction when accelerating out of corners.
In extreme terms, the frame is very rigid when braking, but flexible when cornering and accelerating. This is how Aprilia has just invented the variable stiffness frame.
Two types of struts have been made by Aprilia in MotoGP.
Aprilia MotoGP
