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Circular motion
Published in William Bolton, Engineering Science, 2020
Figure 23.5 shows the basic principles of operation of one form of such a centrifugal clutch. The weights are carried on the free ends of bell-crank levers. When the clutch rotates, the weights are thrown outwards as a result of the circular motion and the resulting pivoting about the pivot causes the pressure plate to become engaged with the driven plate and so torque is transferred. The net force between the plates is F – P, where F is the centrifugal force and P the force exerted by the spring. Thus the frictional force between the pads is μ (F – P), where μ is the coefficient of friction between the pad materials. The frictional torque is thus μ (F – P)R, where R is the radius of rotation of the plates. If there are n such arrangements spaced round the shaft then the total frictional torque T is nμ (F – P)R. The power transmitted by a torque is Tω, where ω is the angular velocity, and so the power transmitted by the clutch is nμ (F – P)Rω.
Wind Tunnels
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2020
In wire-type wind tunnel balances only wires are used to support the model. All the load components are transmitted to the measuring device by these wires. Wire-type balances are probably the simplest and easiest to build. But they have several disadvantages due to the use of too many bearings and bell crank systems, friction of the wires, and high damping requirements. Further, it is extremely bulky since the support system should be very rigid. The disadvantages of wire balances are the following. Large tare drag because of the exposed wires. It is difficult to streamline the wires and hence it is difficult to determine the magnitude of tare drag accurately.Bearings and linkages cause zero error.Wires have the tendency to crystallize and break.Space occupied is very large.
Wind Tunnels
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2016
In wire-type wind tunnel balances only wires are used to support the model. All the load components are transmitted to the measuring device by these wires. Wire-type balances are probably the simplest and easiest to build. But they have several disadvantages due to the use of too many bearings and bell crank systems, friction of the wires, and high damping requirements. Further, it is extremely bulky since the support system should be very rigid. The disadvantages of wire balances are the following. Large tare drag because of the exposed wires. It is difficult to streamline the wires and hence it is difficult to determine the magnitude of tare drag accurately.Bearings and linkages cause zero error.Wires have the tendency to crystallize and break.Space occupied is very large.
Comparison of loosening behavior of bolted joints using plain and spring washers with full-threaded and plain shank bolts
Published in Mechanics Based Design of Structures and Machines, 2023
Shriram Dravid, Jitendra Yadav, Santosh Kumar Kurre
An indigenously designed and developed test rig as shown in Figures 1 and 2 was used to maintain a constant load on the joint at constancy frequency. The pulley at the free end of the bell-crank lever arm carried an unbalanced mass. The radius of rotation of this mass was adjustable. The pulley is rotated by an electric motor, giving rise to unbalanced force, causing up and down oscillations of the arm at forcing frequency. The smaller arm of the bell-crank lever transmits the force (amplified 12 times) to the bolted joint. With this arrangement load of more than 1 ton can be applied on the joint. The experiments have been performed for constant load of 1 ton. The joint used in this study was single-bolted lap joint. A load cell mounted in series with the joint was used to measure the force applied on the joint. Loosening angle was measured as a function of the number of load cycles by measuring it after a fixed interval of cycles. The arrangement for angle measurement is shown in Figure 3. Since the load is constant, the single phase AC motor is used and it gave constant speed.
Topology optimization and finite element analysis of a jet dragster engine mount
Published in Cogent Engineering, 2020
Sanjana Ramesh, Rafael Handal, Matthew J. Jensen, Razvan Rusovici
Lucas et al. (2006), optimized the topology of a bell crank used in a Formula SAE student competition race car in 2006. The new 2006 bell crank was compared to that used in the 2005 competition. Altair OptiStruct topology optimization software was used in order to reduce weight from the 2006 bell crank model whilst maintaining yield strength. Given the results, they had a 24.3% mass reduction from the 2005 model. The 2006 bell crank had a mass of 140 g and obtained a yield increase of 30% (15.9 kN yield load). The results also demonstrated that weight reduction helps vehicular performance. Their 2006 car’s final weight was of 223 kg (2005 model was 246 kg) and ended up third place in the competition. Their time recorded in the 75-m acceleration event was of 4.137 s. This is a drastic improvement to the car model they had in 2005 which ran a time of 4.634 s.
Hybrid Human Error Assessment Approach for Critical Aircraft Maintenance Practice in the Training Aircraft
Published in The International Journal of Aerospace Psychology, 2022
Ebru Yazgan, Elif Kılıç Delice
The elevator is a component of primary flight controls that are needed to securely control an aircraft during flight. These controls consist of ailerons, elevators (or, in some installations, a stabilator), and rudder, as shown in Figure 2. Movement of any of the primary flight controls makes the aircraft turn about the axis of rotation associated with the control surface. The ailerons control motion around the longitudinal axis (roll), the elevator controls rotation around the lateral axis (pitch), and the rudder controls movement around the vertical axis (yaw; Skybary, 2017). In addition, movement of any of the three primary flight control surfaces (ailerons, elevator or stabilator, or rudder), changes the air flow and pressure distribution over and around the air foil. These changes influence the lift and drag produced by the wing and control surface combination, and allow a pilot to control the aircraft about its three axes of rotation (Federal Aviation Administration, 2016). The main pitch, elevator control movement, is bringing the nose of the aircraft up or down relative to the tail. Thus, the aircraft can gain and lose altitude. If the nose is down, the aircraft is gliding or descending; if the nose is up, climbing occurs. Figure 3 gives an illustration of the elevator control system from the aircraft maintenance manual (AMM) of a Cessna 172 type training aircraft. As stated in the AMM, the elevators are operated by power transmitted through forward and aft movement of the control yoke. This movement goes to the elevators through a system that has a push–pull tube, cables, and bell cranks. The elevator control cables, at their aft ends, are attached directly to a bell crank that is installed between the elevators. This bell crank connects the elevators, and is a bearing point for the travel stop bolts. A trim tab is installed on the right elevator (CESSNA Aircraft Company, 2007). The Cessna 172 Series aircraft type weighing less than 5,700 kg, as shown in Figure 2, is a four-seat, single-engine, high-wing and fixed-wing aircraft, the most produced and popular training aircraft in the world.