The secret about a motorcycle frame

Basic advice: We can say that an excellent athlete, in addition to having a vigorous heart, also needs strong bones and muscles to support it. Just like a motorcycle, they must have an excellent frame, in order to drive a high-performance engine.

Let’s find out the secret about the motorcycle frame.

If we say, the engine is the “heart” of a motorcycle, then the frame is the “skeleton” of the motorcycle. The frame is closely related to the handling performance and riding comfort of the motorcycle. The frame supports the engine, provides a fixed position for the steering gear and rear shock absorber, carries the rider, passengers and their luggage, as well as providing mounting locations for the fuel tank and battery.

If the parts of a motorcycle are disassembled, such as the oil pump, the inner tube or the battery, we can clearly observe the use of this “skeleton”. At the front of the frame, we can find where the head tube is mounted; at the rear of the frame, you will see that the swingarm meets the frame. Some frames are tightly coupled with the motor, that is to improve the overall stiffness of the frame;but the opposite is also true, that some motorcycles do not have a frame in the strict sense, you can only see the front subframe and the rear subframe mounted directly on the engine.

There are many kinds of materials for motorcycle frame. In the beginning the motorcycle was a bicycle with an engine, therefore the most common materials of a frame is the bicycle of steel tubes. In the development of material technology opens up new possibilities, with the inherent requirements of improving motorcycle performance, there are more choices in frame materials, in addition to common steels, various materials have been used, such as aluminum alloys, magnesium alloys, titanium alloys, and carbon fibers. Therefore the frame is appeared with various materials.

There are many types of frames, there are also varieties of materials. We can say, there is no perfect framework that can conquer the world.

Which structure and material to choose for a specific model motorcycle frame involves model positioning, mass distribution, required stiffness, dynamic performance and speed.

1.Steel tube cradle frame

Basic structure: there is a single cradle, a double cradle and a semi-double cradle, etc. The double crib frame consists of two single crib frames side by side. Usually the top double tube beam is simplified to a thicker single tube beam. The semi-double bassinet frame is between the double bassinet frame and the single bassinet frame, the upper part is simplified as a single-tube beam, the lower tube is also a single-tube column, and the lower part is a double tube beam.

Its advantages: simple structure and low cost in production.

Uses: It is mainly used in trams, cruisers of small, medium displacement that do not pursue high speed and is used in retro motorcycles.

Model represented: Yamaha SR400.

YamahaSR400 positioned in retro leisure riding. Therefore, this large single cylinder has not been strengthened. The manufacturers have announced its power output is 17.1kW（6500r/min）, the maximum nut is 27.4N m（3000r/min）, the red line speed is set to 7000r/min. Though its power performance is not great, but it is served in daily commute and cruise trip.

Although the power output is not great, it is sufficient for daily commuting and cruising trips. When starting, benefit from the displacement is 399mL, large single cylinder with strong torque at low revolutions, its energetic is from 2000r/min. And it is well configured on the new electronic injection system.

The SR400 high-strength tubular steel frame, used with a slim semi-double cradle frame, works well with the large single-cylinder engine.

The structure of SR400 has never changed, it has been achieved in the balance of strength, stiffness and weight. This steel tube frame hides a secret mystery: motor oil is stored in the main down tube of the frame.This design allows the SR400’s engine to use a dry sump frame configuration, this can reduce the overall height of an engine, increase higher ground clearance and provide ample cornering clearance. When driving on the road, when passing a curve, we can feel that the SR400 is flexible and its handling is labor-saving, due to the slim size of the single cylinder, the turning space is wide, so it is easy to take the curves. Of course, an SR400 retro single-cylinder road car can’t be raced that much.

If you are driving on a straight road, put the gear in 5th, it can run up to 160 km/h. But, at this point the motor feels rough and its vibration is going to be very apparent. The most suitable speed of this motor is between 3000r/min and 5000r/min. At this time, the single-cylinder engine makes a very rhythmic sound. The power output, the frame and the suspension system work together in harmony. If it runs at a speed between 80km/h and 100km/h, both the rider and the passenger will feel very comfortable. If the bore, stroke and displacement remain the same, then the Monster 1200R has gotten more violent.

2.Steel tube lattice frame

Basic structure: It is used in the round or oval tubes, Through the welding or brazing process, it is equipped with a lattice structure. It is made up of steel tubes and is usually triangular, which is for better structural stability.

Its advantages: robust construction and lightweight quality.

Uses: It is mainly used in street cars.

Model represented: Ducati monster 1200R.

If the bore, stroke and displacement are going to stay the same, then the Monster 1200R is going to be more violent.

Peak power is increased by 10%, peak torque is increased by 5.5%, up to 117.7 kW（9250r/min）and 131.4N m（7750 r/min）.

This engine has a peak power increase, while the power is improved throughout the rev range: the torque at low revs is strong, at only 3500r/min, the engine can do a 75% transmission. As speed increases, the L-type twin is going to be more excited.

In the mid range the throttle speed is going to be strong until the boost continues until the red line speed is 10500r/min. Through the test, from standstill to 100km/h, it only takes 3.2 seconds to accelerate and the top speed can exceed up to 250km/h.

Monster 1200R inherits Ducati’s classic chrome-molybdenum alloy steel tube lattice frame. The frame locks directly into the cylinder head, borrowing advanced technology from the Panigale super sports car, while reducing weight, achieving exceptionally compact structure. At the same time, large diameter chrome molybdenum alloy steel pipe is used, to effectively increase torsional rigidity, help improve sports performance. To increase the space in the curves, it is increased in the configurations of the frames, in front and rear it is increased by 15mm, in the height of the seat it has an increase of 830mm.
Comfortable driving posture is guaranteed. At the same time, the driving control on the road and on the track is optimized, between these three a good balance is achieved.

3.Mixed frame structure

Basic structure: Its main structure is steel lattice frame. But at the back of the bottom of the frame, an alloy plate is added to strengthen.

The steel lattice frame at the top is connected with the motor, and the alloy plate at the bottom rear is connected with the rear rocker.

Its advantages: its structure is robust, low weight of quality, the force is increased little by little.

Uses: Primarily used on high performance NK street cars.

Representative model: Apulia Dorsoduro 900.

Europeans like tire cars very much, Apulia is the famous brand in Europe, this brand is an expert in tire skating and has won several tire skating world championships. They mix with the experience of the Dorsoduro 900 track, bringing a different passion to the riders.

The latest generation of Dorsoduro 750 has garnered wide accolades, but compared to the excellent frame, the 750mL twin-cylinder powerhouse doesn’t get as many accolades, especially when compared to similar Ducati models. Facing each question, Apulia gave the Dorsoduro 900 answer, fighting the anti double V cylinder against the Ducati double L cylinder.

The maximum power of the Dorsoduro 900 was increased to 70.0 kW (8,750 R/min).

The maximum torque increased to 90.0 N m (6500 R / min), it has surpassed the previous generation.

Apulia claims that the Dorsoduro 900 has superior torque to the Dorsoduro 750 at full throttle and a flatter torque curve that allows riders to precisely control power distribution.

4.Aluminum alloy double beam frame

Basic Structure: Double beams span the engine from the steering head to the front end of the swingarm. The double beams are designed as short as possible in order to have greater rigidity.

Its advantages: high strength and high rigidity.

Uses: Mainly used for super sports cars.

Representative model:YAMAHA YZF-R1.

Yamaha fought against the new engines of the last generations, such as HP4 and RSV4. YAMAHA launched YZF-R1 to be a new platform. Its new design is equipped with four cylinders in parallel and its maximum power is increased to approximately 148kW, it is not necessary to take forced air, compared to the previous generation it has been increased by 10%.

When we talk about reducing weight, YAMAHA has had many thoughts on them and the most representative is the engine connecting rod. This connecting rod groupset is made of special technology, and its material is titanium alloy. Compared with the traditional steel connecting rod, the weight can be reduced by 40%, the inertia is greatly reduced.

Also, the newly designed crankshaft can be reduced by 20%, this makes the engine very sensitive, especially in the high speed area. In addition, the 4-2-1 structure exhaust system is used, made of titanium alloy material, the rim is made of magnesium alloy. This allows the front and rear tire mass to be reduced by 4% and 11% respectively, to improve practical acceleration and braking.

Those lightweight, high-strength materials can reduce the weight of the YZF-R1 to 179kg, and even if the fuel tank is full of gas, the weight is not going to exceed 200kg.

5.Monocoque

Basic structure: actually the monocoque is the most widely used in the sedan field. The monocoque frame of the motorcycle is composed of a unit structure, adopting a hollow structure, and the outer shell bears the load of many parts, such as batteries.

Its advantages: its strength and rigidity are very excellent, but it has a high cost in production.

Uses: Mainly used in supercars, sports touring motorcycles.

Representative model: Kawasaki 1400 GTR.

Sports cars have high standards, including the combination of abundant power, natural handling, comfortable driving and support for passengers to travel thousands of miles per day and long distances throughout the state. So this number becomes a handful. Without a doubt, the Kawasaki 1400 GTR is among this handful.

What makes the 1400GTR proud is the engine with a displacement that reaches up to 1352mL. This being the power heart of the “Super Ninja” ZX-14 is the largest displacement parallel four cylinder engine can produce a maximum power of 114kW (8800r/min) and a maximum torque of 136N m (6200r/min). min).

In addition, the rider does not have to worry about running out of power when riding it. Acceleration and overtaking are extremely simple.