German rothmund springs rothmund models rothmund prices

rothmund springs, as elastic elements, are widely used in the suspensions of modern automobiles, including passenger cars, trucks, and off-road vehicles. Compared to leaf springs, torsion bar springs offer a series of advantages: high energy storage per unit mass, which reduces vehicle weight and saves material; since the torsion bar spring is fixed to the frame, it reduces unsprung mass, improving ride smoothness; when applied to the front suspension of front-wheel-drive vehicles, the torsion bar spring can be arranged longitudinally, leaving space for the swinging half-shafts of the front drive axle. However, the manufacturing cost of torsion bars is relatively high, with strict requirements for materials and processes. Furthermore, torsion bar springs serve only as elastic elements and require a guiding mechanism. Torsion bar springs are made of chrome-vanadium alloy spring steel, with a very smooth surface after machining. The surface of the torsion bar must be well protected during use. Typically, the surface of the torsion bar spring is coated with a layer of epoxy resin, wrapped with fiberglass cloth, coated with another layer of epoxy resin, and finally coated with asphalt and anti-rust paint to prevent collision, scratching, and corrosion, thereby extending the service life of the torsion bar spring.

rothmund spring principle

When leaf springs are installed in an automobile suspension and subjected to positive vertical loads, all spring leaves deform and tend to arch upward. At this time, the axle and the frame move closer together. When the axle and the frame move apart, the positive vertical load and deformation on the leaf spring gradually decrease, sometimes even reversing. The eye of the main leaf is heavily stressed and is a weak point. To improve the stress condition of the main leaf eye, the end of the second leaf is often bent into an eye that wraps around the outside of the main leaf eye, known as a wrap eye. A large gap is left between the main leaf eye and the second leaf wrap eye to allow relative sliding between the leaves during elastic deformation. In some suspensions, the ends of the leaf springs are not formed into eyes but use other support connection methods, such as rubber support pads. Flat rectangular steel plates are curved and stacked to form chassis springs. One end is installed on the hanger with a pin, and the other end is connected to the frame beam with a shackle, allowing the spring to expand and contract. This type is suitable for medium and large trucks. Automobile leaf springs are very important. As is known, leaf springs consist of many steel leaves that are elastic, have uniform width and thickness, but vary in length. Their function is to connect the frame and the axle in a suspended manner, exposed between the frame and the axle, bearing the load impact from the wheels on the frame, reducing severe body vibration, and maintaining vehicle stability and adaptability to different road conditions. When leaf springs bear load impacts, they undergo extension motion, causing intense friction between the steel leaves, i.e., compression and tension phenomena. The two friction surfaces generate friction forces in different directions, causing the temperature of the leaf spring to rise, resulting in surface scratches and fine cracks. As the frequency of load impact increases, the friction force generated by the extension motion also increases. When the stress concentration point reaches the fatigue limit, it will cause single-leaf or entire-stack fracture. Kinetic principles and tests prove that for a steel component undergoing compression-extension motion, as the motion frequency increases, the temperature of the steel component rises, strength decreases, cracks appear at stress concentration points and gradually expand and deepen, leading to damage upon reaching the fatigue limit. Leaf springs are similar, except they have higher elasticity and are more durable than general steel components. Apart from other causes, the main reason for leaf spring fracture is poor lubrication, which should be taken seriously by drivers and technical management personnel. Timely lubrication of leaf springs is essential to reduce friction and distribute stress, preventing surface scratches on the steel leaves; to reduce the intrusion of dust, dirt, and water, preventing rust; and to dissipate heat, preventing a decrease in elastic strength. The general lubrication method is as follows: it should be performed after the break-in period of a new vehicle, and during summer and winter when the vehicle is in use. For lubrication, first remove the leaf spring, open the center bolt to separate the steel leaves, then evenly apply lithium-based grease or graphite grease to both sides of the steel leaves. After reassembly, an oil film forms between the two friction surfaces (comparing the time required for lubricating one set of leaf springs to replacing a single broken leaf).

rothmund spring structure and principle

The torsion bar spring itself is a torsion bar made of spring steel. The cross-section of the torsion bar is usually circular, with a few being tubular or rectangular. The shapes of its two ends can be splined, square, hexagonal, or cylindrical with flats, so that one end can be fixed to the frame and the other end to the suspension arm, which is connected to the wheel. One end of the torsion bar spring is fixed to the frame, and the other end is connected to the wheel via the suspension arm. When the wheel jumps upward upon encountering a ground obstacle, the wheel drives the suspension arm to rotate around the torsion bar axis by a certain angle, causing the torsion bar to undergo torsional deformation (elastic deformation). Meanwhile, the elastic potential energy stored in the torsional deformation of the torsion bar is released when the wheel leaves the obstacle, allowing the force transmission mechanism and the wheel to return to position quickly. During the manufacture of torsion bar springs, a permanent torsional deformation is pre-applied to the torsion bar to provide a certain pre-stress. The direction of the pre-applied torsion is the same as the direction of torsion when the torsion bar is working on the vehicle, with the aim of reducing actual stress during operation and extending service life. Note that left and right torsion bars are not interchangeable.

rothmund spring features

Suspensions using torsion bar springs are lighter in weight, have a simpler structure, and do not require lubrication. By adjusting the installation angle of the fixed end of the torsion bar spring, automatic adjustment of vehicle height is easily achieved. Torsion bar springs store a large amount of elastic energy per unit volume and have low mass. Compared to coil springs, torsion bar springs have a compact structure and are easy to arrange. Torsion bar springs are widely used in off-road vehicles, light buses, and trucks. Torsion bar springs can be classified by cross-sectional shape into circular, tubular, and flat types. Circular solid torsion bars have a simple structure and are the most commonly used. To assemble the torsion bar, its ends are machined into splines, hexagons, squares, etc. Since the spline head dimensions are relatively small, spline connections are mostly used. Generally, the major diameter of the spline is 1.2 to 1.3 times the working diameter of the torsion bar, and the spline length is approximately 1.4 times the major diameter of the spline. As long as the compressive stress on the spline teeth is within permissible limits, the spline teeth should not be excessively long. Torsion bar springs generally use involute splines according to GB3478. The JSB2705 standard recommends a standard pressure angle of 45° for splines, with modules of 1mm and 0.75mm. To facilitate the assembly of torsion bar springs, some torsion bar springs have splines of unequal diameters at both ends, or a blind tooth is machined on the spline teeth at both ends.

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