Sprocket Teeth Research Articles

Experimental investigation of link tension and roller-sprocket impact in roller chain drives

This paper presents the results from a recent experimental investigation into the dynamic behavior of roller chain drives. A strain gage mounted on a link side plate was used to determine chain tension during normal operation over a wide range of linear chain speeds and preloads. The test machine also included specially instrumented idler sprocket that allowed the measurement of the horizontal and vertical components of the bearing reaction force. The roller-sprocket impact force was then computed by an experimental transfer function approach facilitated by a Bruel & Kjaer 2032 dual channel spectrum analyser. Observations about the data include: •• As is typically assumed, under quasi-static conditions, dynamic effects can be neglected without introducing significant error.•• As chain speed increases, dynamic effects become increasingly important.•• As is the case for belt drives, the average tight side chain tension can be expressed in the classical form of the preload, the driven load, and the load due to centrifugal force with only modest error over a wide range of linear chain speeds.•• The tension in a chain link increases very rapidly as the link exits the driven sprocket. The increase from loose side to tight side average tension occurs over less than two sprocket teeth.•• The tension in a chain link decreases very rapidly as the link enters the drive sprocket. The decrease from tight side to average loose side tension occurs over less than two sprocket teeth.•• Transient spikes are present in the tension data at the point were the link exits the driven sprocket and at the point where the link enters the driven sprocket.•• Impact force tends to increase as chain tension increases, however the relationship is not monotonic.•• Impact force tends to increase as chain speed increases, however the relationship is not monotonic.•• For a chain traveling in the horizontal direction, the vertical component of the impact force is much larger than the horizontal component.•• The magnitude of the horizontal component of the impact force increases more rapidly than the magnitude of the vertical component as the chain speed increases, indicating that the angle of impact (as measured from a vertical line) increases as chain speed increases.

Coupled response and noise of roller chain drive systems

A chain drive system consists of a closed loop roller chain wrapped around two or more sprockets. One of the most significant noise sources in an operating roller chain drive emanates from the repeated impacts between the chain links and sprocket teeth during their meshing. Previous studies on the local-global meshing of the chain with the sprockets only considered the dynamic transverse motion of an axially moving chain while uncoupled from the sprockets. In this study, the analysis is extended to axial-transverse motions of the moving roller chain coupled with the dynamic response of the rigid sprockets over which the chain is wrapped around. The analysis thus integrates the local impact meashing to the global response of the chain-sprocket system. Numerical simulations of the analytical model showed that the coupling effects between the two sprockets, the two chain spans, and the chain-sprocket meshing impulse intensity increase with decreasing sprocket inertia and chain longitudinal stiffness. Controlled tests on a roller chain/two-sprocket system verified the results of the numerical simulations; that the meshing noise SPL is directly related to the chain speed and its vibrational characteristics. [Work supported by the GM Currently at GM Research & Development Center.

Contact forces in the non‐linear dynamic analysis of tracked vehicles

AbstractIt is known that when two springs are connected in series, the stiffness coefficient of an equivalent system that consists of one spring is less than the stiffness coefficients of the original springs. Experimental observations indicate that this fact can be very useful in determining the overall vibration characteristics of tracked vehicles. This simple fact is used in this investigation to develop a computer aided analysis procedure for the dynamic simulation of large‐scale tracked vehicles. The track is considered as a closed kinematic chain that consists of rigid bodies connected by revolute joints. The contacts between the track links and the rollers, the sprocket, and the idler are represented by non‐linear continuous force models. The stiffness and damping coefficients in these contact force models are determined by studying the viberation characteristics of the tracked vehicle. The tooth of the sprocket is defined using three surfaces. These are the left, the bottom, and the fight surfaces. Three successive transformations are used to define the contact kinematic relationships between the sprocket teeth and the pins of the track links. The equations of motions of the vehicle are formulated using the Lagrangian approach. Non‐linear constraint equations that describe mechanical joints and specified motion trajectories in the system are adjoined to the differential equations of motion using the technique of Lagrange multipliers. The resulting mixed system of differential and algebraic equations is solved numerically using a direct numerical integration method. A Newton–Raphson algorithm is used to check on the violations in the kinematic constraints. The results presented in this paper are obtained using a 54 body planer tracked vehicle in which the track consists of 42 rigid links connected by revolute joints.

Meshing noise from timing chain drives

Controlled experiments on a specially constructed timing chain drive test stand have shown that the most significant noise source in roller chain drives is from impacts between the chain links and the sprocket teeth during their meshing process. Despite its importance, a study that can analytically predict and experimentally verify the characteristics of meshing noise has yet to be performed. A method is presented that can quantify the meshing noise as a function of the critical system parameters, such as chain speed, tension, mass and shape of chain links, and sprocket geometry. A comprehensive model that integrates the chain transverse and longitudinal vibrations with the sprocket motion is developed. The approach also couples the local meshing impulse with the global system dynamic response of the vibrating chain. Parametric tests were carried out on a test stand in which a roller chain and up to three sprockets could be tested. Besides the chain speed and tension, the local vibration and the sound pressure levels are recorded. This fundamental investigation provides new insight into roller chain noise problems. [Work supported by General Motors Corp.]

Periodic Shock Pulses Occurring in a Rooler Chain Driving System with a Reduction Gear.

This paper describes research on periodic shock pulses occurring in a roller chain driving system, which is used as the bed-sliding mechanism of X-ray diagnostic tables. The shock pulses, which had the periodicity of a mesh frequency between the chain and the sprocket, were observed only when the bed was moved downward with a loaded mass in a certain weight range. This roller chain system consists basically of a driving motor, a reduction gear, and two-stage chains and sprockets. Using an experimental device modeling the roller chain driving system, the shock-pulse phenomenon was investigated by changing the weight of the mass, the tension of the chain and the number of sprocket teeth. It was found that the phenomenon occurred due to periodic hits between the gear teeth at the reduction gear, which were caused by torque oscillation between the roller chain and the sprockets of the second stage. Theoretical analysis on torque oscillation was performed, which led to the elimination of the periodic shock pulses from the roller chain driving system.

Experimental evaluation of chain noise

Chains are commonly used in automotive powertrains for their reliability and durability. However, chain drives can be noisy, and thus a fundamental understanding is needed. One of the fundamental sources of this noise is the impact of the chain roller on the sprocket teeth. To investigate the mechanism behind this impact, an experimental apparatus has been designed, constructed, and tested. The test stand is composed of a high-speed stepper motor (6000 rpm) driving a two-sprocket chain drive with a simple flywheel at the output. The signal from a strain gauge instrumented on one sprocket tooth is extracted by means of a slip ring. This instrumentation will be used to conduct a parametric study to examine the relationship between impact and various system parameters, such as chain tension and speed. [Work supported by General Motors Corporation.]

Modeling and analysis of chain drive systems

Chain drive noise caused by meshing between the chain link and the sprocket has been recognized to be an important problem in the design of automotive powertrains. This paper presents a new dynamic model that integrates the local meshing mechanics with the global chain vibration characteristics. The chain is modeled as an axially moving, heavy string under tension. The upstream boundary condition is considered to be fixed, while the downstream boundary condition depends on the impact load between the sprocket tooth and the meshing chain link. The chain/sprocket impact load is derived based on the Lagrange's impact equation, and is a function of the system's dynamic characteristics. A parametric study is performed based on this model. The relationships between the impact load and the important system parameters, such as chain tension, chain speed, chain inertia, chain length, and pitch, are quantified. The chain response under the meshing effect is analyzed. The results of this fundamental research are useful in optimizing such mechanical systems. [Work supported by General Motors Corporation.]

The effects of the pitch difference on the load distribution of a roller chain drive

An analysis is presented to determine the effects of pitch difference, friction, and centrifugal forces on the load distribution of a roller chain. Load distribution curves for chain links and sprocket teeth as a function of the angle of rotation of the sprocket, as well as plots of the sprocket and roller chain interaction are given. Friction is shown to cause a higher tooth load on a driven sprocket than that of a driver sprocket.

Experimental load distributions for double pitch steel roller chains on polymer sprockets

An experimental study was conducted to measure the load distribution in steel roller chains on polymer sprockets and determine the effect of material modulus of elasticity, tight-side load, slack-side load and pitch difference. A chain load distribution test machine and a single sprocket tooth test machine were designed and constructed to conduct this investigation. Theoretical results obtained from a geometric progression load distribution model and a spring model load distribution analysis were compared to the experimental results.

Experimental Determination of the Roller Chain Load Distribution

An experimental study was conducted to determine the effect of elastic properties, geometric variations, and lubrication on roller chain load distribution. Comparison was made with the theoretical results for a test chain on a 20-tooth sprocket. The load distribution was found for a large number of cases to be independent of the elastic properties of the chain and the sprocket. The load distribution for the chain on a driver sprocket differed from that for a chain on a driven sprocket because of the change in direction of the friction force. Lubrication had no noticeable effect. A large pitch for the sprocket teeth was found to amplify the tension in the chain link.

Sprocket tooth engaging track noise suppression means

A noise attenuating system for the tracks of a track-laying vehicle. A plurality of noise attenuating devices are disposed about the track chain of a track-laying vehicle, one device mounted upon each track shoe. Each device is comprised of a preloaded spring means in the form of a block or pad of elastomeric material and each device is mounted upon the inner circumferential portion of an individual track shoe. A wear plate means is included for directly engaging the radially outermost portions of the teeth of the driving sprocket of the track-laying vehicle. The devices are disposed so that the outermost edges of the sprocket teeth engage the wear plates prior to engagement of the track bushings with the sprocket notches and are also disposed so that metal-on-metal contact between the leading and trailing edges of each respective link shoe is preceeded by contact between each respective leading edge and the elastomeric material from which the spring means are composed.

A New Sprocket for Theatrical 35mm Projection Equipment, Designed to Limit Film Damage

An answer to the problem of premature film damage in theatrical exhibitions is found in a new sprocket-tooth shape. Torn film often occurs when heavy film tension causes the sprocket tooth to deform the driven edge of the perforation. Lateral film movement causes the tooth to cut into the perforation corners. A redesign of the projector sprocket must take into consideration the importance of handling films with CS perforations as well as the standard KS perforation. The new VKF (Very-Kind-to-Film) sprocket design follows standard center-to-center dimensions, but involves an increase in overall tooth width and adds a radius at all tooth corners so that no sharp edges can contact the perforation, and there is no opportunity for the tooth to contact the corners of the perforation. The design will accommodate either KS or CS perforations. The VKF sprocket is an attempt to make the possibility of film damage less likely, to reduce wasteful film loss, to limit the time spent on film repair, and to make screen presentation more pleasing to the patron.

On the analyses of sprocket load distribution

This paper presents a spring model analysis for the load distribution in chains and in sprocket teeth and compares the results with those from a traditional force-balance analysis which does not include a consideration of elastic properties.

Gimmicks and Gadgets

Featured in this month's “Gimmicks and Gadgets” is an idea to replace worn sprockets. The procedure entails building up the teeth of worn sprockets with excessive weld material and then grinding them to fit the original shape.

Thermomechanical treatment with roller burnishing of sprocket teeth

Thermomechanical treatment with roller burnishing of sprocket teeth

A Photometer for Measuring the Output of Timing Lights

A highly sensitive pulsed-light photometer, which has three stages of solid state amplification, measures the intensity of tiny pulsed-light sources which occur in camera timing markers on high-speed cameras. It measures the relative intensity of a 20-mil diameter pulsed-light spot, but is not affected by direct sunlight. One form of the light probe which fits between the sprocket teeth of a 16mm camera is suitable for checking the reliability of camera timing out on the range. The thin-probe mount which carries only one stage of amplification is connected by a cable to a case containing the other stages, the meter and range switches.

Super 8 Processing with a 16mm Sprocket Machine

Specially designed combination drive sprockets have been substituted for the conventional 16mm drive sprockets in the processing machine. By an offset splice between Super 8 film and regular 16mm film or double 8mm film, the film is automatically transferred to the proper set of sprocket teeth.

Cine Spectrograph

To study time varying spectral characteristics, a spectrograph has been devised capable of recording successive spectra of an object on continuously driven 70-mm film. Each of the 5000 exposures per second recorded by the instrument consists of five spectra recorded simultaneously. Four of these are of the selected source, with the fifth being of a tungsten source to provide spectral calibration of the film. The film is brought out of a magazine, past a film drum, and onto a takeup spool. The drum has sprocket teeth which engage a length of film in the neighborhood where exposures are made. Attached to the drum is a skirt in which are cut eighty slanting slots. These rotate directly in front of a slit assembly consisting of five parallel slits each fitted with a neutral density filter. The slots act as a shutter, admitting light only through the areas of the slits exposed by a slot. Since unit magnification optics are used, the image travels with the film. Spectrograms of sources available in the laboratory are discussed.

High-Repetition Rate Stroboscopic Light Source

The open time of a Fastax rotating-prism shutter is 40 μsec at 5000 frames/sec. Better action-stopping is achieved with a 1-μsec stroboscopic light. A 5C22 triggered by Fastax sprocket teeth discharges a 12-kv pulse-forming network into an Edgerton lamp 5000 times/sec. An area 3 × 3 ft is adequately illuminated for reflection photography with ASA 100 film at f/2.7.

A New Basis for the Rating of Roller-Chain Drives

Abstract Reference tables giving horsepower ratings for roller transmission chains are commonly based upon certain allowable working pressures per square inch of projected bearing area at the chain joints. The allowable working load is assumed to increase in proportion to the projected area of the pins and to decrease with an increase in chain velocity and an increase in the “centrifugal pull” of the chain. An analysis of the bending action of the links at both driving and driven wheels and the work of friction between pins and bushings yields an algebraic expression for the beat generated per minute, or for the rate of wear in the chain. This is proportional to the rate of elongation of the chain; and this rate of elongation is found to be directly proportional to the horsepower transmitted and inversely proportional to the pitch, the length of the bushing, the number of links in the chain, and the product of the number of teeth in the two sprockets (very nearly). A set of tables is developed based upon chain velocity and the number of teeth in both sprockets. The horsepowers taken from these tables are such as will produce approximately the same rate of elongation in all drives whose design and operation conform to average conditions. Similar tables are computed on the basis of the rpm of the smaller sprocket instead of the chain velocity. These tables also allow for the extra pull on the chain due to centrifugal force, and for the chain lengths and center distances necessary to keep the rate of elongation within the limits allowed. An examination of these tables shows that, with certain combinations of sprocket teeth and chain lengths, loads twice as great as those usually given in tables can be transmitted. And these figures seem to be supported by actual practice. The subject of limiting speeds for sprockets is treated and three sets of limiting conditions are investigated, namely: (a) the effect of a single impact between chain rollers and sprocket teeth, (b) the energy of impact per tooth per minute, and (c) the effect of centrifugal action. A table is compiled giving maximum chain velocities and sprocket speeds, based upon these investigations, for various chains and various numbers of teeth in the sprockets. This table shows the conditions under which certain chains can be operated at velocities above 3000 fpm and other conditions under which the same chains should not be operated at more than 240 fpm.