Universal joints with thermoplastic body members are used in light industrial applications in which their self-lubricating feature, light weight, negligible backlash, corrosion resistance and capability for high-speed operation are significant advantages. Universal joints of special construction, such as ball-jointed universals are also available. These are used for high-speed operation and for carrying large torques.
They are available both in miniature and standard sizes. The angular-velocity ratio between input and out put shafts varies cyclically at two cycles per revolution of the input shaft. In selecting a joint the effect of these fluctuations on static torque, inertia torque and system performance needs to be kept in mind. The non uniformity of the transmission can be eliminated by using two appropriately phased universal joints in series, as shown in Figure 2.
In such cases the velocity variation induced by one joint can be made to cancel that of the ot her, thereby transmitting a constant angular velocity ratio between shafts.
The angular velocity fluctuation of the intermediate shaft, however, cannot be avoided. Two universal joints in series also permit coupling of two laterally displaced shafts single Cardan joints are limited to intersecting shafts.
Single Cardan joints have the following advantages: Low side thrust on bearings. Large angular displacements are possible. High torsional stiffness. High torque capacity. They have the following disadvantages: Velocity and acceleration fluctuation increases with operating angle.
Lubrication is required to reduce wear. Shafts must lie in precisely the same plane. Backlash difficult to control. The angular displacement of the output shaft does not precisely follow that of the input shaft but leads or lags, again with two cycles per revolution.
The angular-velocity variation as a function of operating angle is illustrated in Figure 3. The peak displacement lead or laq. Baranyi, Design News, Sept.
The table should always be consulted for exact numerical values. The static torque transmitted by the output shalt is equal to the product of the input to torque and the angular-velocity ratio. The angular acceleration gives rise to an inertia torque, as well as to vibrations.
The inertia loading often determines the ultimate limit on the speed of operation of the joint. Recommended speed limits vary depending on operating angle, transmitted power and nature of the applicatlon. View Cart Checkout.
A u-joint universal joint is basically a flexible pivot point that transmits power through rotational motion between two shafts not in a straight line. The u-joint needs to be flexible to compensate for changes in the driveline angle due to the constantly changing terrain under the vehicle. The u-joint is one of the oldest of all flexible couplings.
It is commonly known for its use on automobiles and trucks. A universal joint in its simplest form consists of two shaft yokes at right angles to each other and a four-point cross that connects the yokes. The cross rides inside the bearing cap assemblies, which are pressed into the yoke eyes. One of the problems inherent in the design of a u-joint is that the angular velocities of the components vary over a single rotation.
The yokes that hold the u-joint bearing caps are sometimes referred to as ears. The bearing caps of the u-joint are pressed into the yoke ear and held in place with a c-clip half circle , an internal snap ring, or a full-circle snap ring.
Over time and under harsh conditions c-clips tend to wear into irregular shapes and fall out. When the c-clip falls out eventually the u-joints bearing cap will work its way out of the yoke. This damage is very difficult to repair and usually requires the purchase of a new inner or outer axle shaft or costly driveshaft repairs. Standard u-joints are not designed to run at extreme driveshaft angles unless they are specially constructed.
Extreme angle driveshafts are achieved by using a double Cardan constant velocity joint. This is basically a joint with two u-joints. This table is based upon the joint at rated load and life. Going above the rated load or angle will decrease the u-joints life. As a rule of thumb, for each doubling of the operating angle, RPM, or load, the lifetime of the joint is decreased by half.
Rated lifetimes are on the order of hours. In the typical off-road vehicle, a suspension lift is done to increase clearance and allow larger tires to be installed.
Thus, the double universal joint acts as a constant velocity joint. You can see a similar arrangement in rear wheel driven automobiles Fig. You can see that the drive shaft is fitted between two universal joints. So the speed output at the second universal joint will be same as the input. The double universal joint described in the previous session is a constant velocity joint. However more efficient constant velocity joint designs, they do not require an intermediate shaft have evolved over time.
Some of the popular CV joints are listed below. He provide quality engineering education on his YouTube channel. Sabin is a very passionate about understanding the physics behind complex technologies and explaining them in simple words. To know more about the author check this link.
Ltd All Rights Reserved. How does a universal Joint work? February 9, Invention of universal joints dates back many centuries. Why Universal Joints are used? The spin of the cross When the shafts are at an angle the motion is quite different. Fig:4 The ends of universal joint turn in different planes To make the red ends move along the inclined plane, the cross has to spin along the axis connecting the green ends. Fig:5 The shaft connecting the green ends should spin to accomplish this movement To make the cross spin concept clearer, just imagine what happens when the spin of the green axis is halted.
Fig:6 hypothetical movement to illustrate the need of cross spin It is clear that, such a situation is impossible. The effect of cross spin The spin of the cross makes a huge difference in the speed of the output shaft.
Fig:5 Forward spin of the shaft during the first 90 degrees Fig. Fig Angular displacement of the output shaft during degrees turn Just by taking a simple time differential of this displacement graph we can find out speed of the output shaft.
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