Adjustable Ice Fishing Tip-Up

An ice fishing tip-up includes a base frame adapted to span a hole in a layer of ice over a body of water, and carrying a mast which is extendible through the hole into the water. The mast includes a shaft fixed at its lower end to a spool of fishing line and at its upper end to a cam cylinder with a helical groove formed in its outer surface. A signal staff is spring-biased to a raised position and is movable to a lowered position received in one of the convolutions of the helical groove. A pull on the fishing line rotates the cam until the staff reaches the end of the helical groove, releasing it to its raised position, the amount of pull required to trip the staff being adjustable with the cam groove convolution in which it is retained

Compliant Pliers

The pliers include an endless loop, a top jaw appended to the endless loop, and a bottom jaw appended to the endless loop. The endless loop includes in series a top grip handle, a spring segment, a bottom grip handle and a compliant strip interconnecting the top and bottom grip handles. A rolling surface on the top grip handle rolls on a contact portion of the bottom grip handle. The rolling action causes the compliant strip to flex which causes the top and bottom jaws to move toward one another. The endless loop provides a built-in automatic spring and enhances lateral stability

Experiences in the Integration of Design Across the Mechanical Engineering Curriculum

The Faculty of the School of Mechanical Engineering at Purdue University have effected a major change in the Purdue Mechanical Engineering program by integrating design throughout the curriculum. In doing so, a significant level of faculty interaction has been achieved as well. The goals of the curriculum revision are: (1) to improve student skills in how to solve open-ended design problems, (2) to reduce the core of the curriculum to allow flexibility in course selection, and allow time for solving design problems, (3) to improve student skills in team work and communications, and (4) to improve student skills in using computers as tools for solving engineering problems. Reduction of the core allowed the addition of a sophomore cornerstone design course. This cornerstone course teaches students how to solve open-ended problems, bridging the gap between solution strategies that are effective for the science and mathematics courses, and those needed to solve open-ended engineering problems. The design fundamentals taught in the cornerstone course are applied in the core courses, such as heat transfer, thermodynamics, instrumentation, and machine design. The senior design experience comes primarily from a design elective and the capstone design course. This paper presents an overview of the curriculum revision process, and the changes which resulted from it. It also discusses the issues associated with infusing design projects into core courses which have traditionally focused on teaching engineering science fundamentals. Plans for the future evolution of the curriculum are also discussed

Compliant Mechanisms -- Memory Lane and Some Novel and Exciting Applications

A set of chance happenings led to the beginning of formalization of a research area, termed “compliant mechanisms,” around early 1980s. This presentation takes one down that memory lane describing how it all came about. What appeared to be a modest beginning, in time would exceed every expectation and more, and continue to proliferate with applications into multiple disciplines. Some very recent theoretical developments in compliant mechanisms are discussed, that offer fundamental discovery, with the potential for innovating exciting design applications

Mechanical Advantage of a Compliant Mechanism and Significant Factors Affecting IT, Using the Pseudo-Rigid-Body Model Approach

Although work related to mechanical advantage of compliant mechanisms has been presented almost two decades ago, unlike many rigid-body mechanism systems, this performance measure has seldom been used. In great part, the reasons are attributed to, one, the relatively recent development of and a lack of familiarity with this technology and, two, the complexity of the understanding and evaluation of mechanical advantage of compliant systems. In an effort to simplify the evaluation, this work uses the pseudo-rigid-body model (PRBM) of a compliant mechanism, along with traditional notions of power conservation and angular velocity ratios using instant centers. As a first step, the inherent compliance in the mechanism is neglected in determining its mechanical advantage, followed by considerations to optimize its structural configuration for enhancing its mechanical advantage. The PRBM methodology, which offers us a way to estimate the characteristic compliance of the mechanism, now enables its inclusion in determining the mechanical advantage of the compliant mechanism. Two significant factors affecting it are i) the structural configuration of the PRBM, and ii) the energy stored in compliant elements of the mechanism. Several case studies are presented, which suggest that minimizing the latter contribution relative to that of an optimized structural configuration may improve the mechanical advantage of a compliant mechanism. Nonetheless, its effect on the mechanical advantage cannot be neglected

Steady-State Response of Periodically Time-Varying Linear Systems, with Application to an Elastic Mechanism

This paper presents the development of an efficient and direct method for evaluating the steady-state response of periodically time-varying linear systems. The method is general, and its efficacy is demonstrated in its application to a high-speed elastic mechanism. The dynamics of a mechanism comprised of elastic members may be described by a system of coupled, inhomogeneous, nonlinear, second-order partial differential equations with periodically time-varying coefficients. More often than not, these governing equations may be linearized and, facilitated by separation of time and space variables, reduced to a system of linear ordinary differential equations with variable coefficients. Closed-form, numerical expressions for response are derived by dividing the fundamental time period of solution into subintervals, and establishing an equal number of continuity constraints at the intermediate time nodes, and a single periodicity constraint at the end time nodes of the period. The symbolic solution of these constraint equations yields the closed-form numerical expression for the response. The method is exemplified by its application to problems involving a slider-crank mechanism with an elastic coupler link

Efficient Method for Evaluating Steady-State Response of Periodically Time-Varying Linear Systems, with Application to an Elastic Slider-Crank Mechanism

This paper presents the development of an efficient and direct method for evaluating the steady-state response of periodically time-varying linear systems. The method is general, and its efficacy is demonstrated in its application to a high-speed elastic mechanism. The dynamics of a mechanism comprised of elastic members may be described by a system of coupled, inhomogeneous, nonlinear, second-order partial differential equations with periodically time-varying coefficients. More often than not, these governing equations may be linearized and, facilitated by separation of time and space variables, reduced to a system of linear ordinary differential equations with variable coefficients. Closed-form, numerical expressions for response are derived by dividing the fundamental time period of solution into subintervals, and establishing an equal number of continuity constraints at the intermediate time nodes, and a single periodicity constraint at the end time nodes of the period. The symbolic solution of these constraint equations yields the closed-form numerical expression for the response. The method is exemplified by its application to problems involving a slider-crank mechanism with an elastic coupler link

Design of a Compliant Mechanism to Generate an Arbitrary Nonlinear Force-Deflection Profile

This paper presents a compliant mechanism that can generate a wide range of force-deflection profiles. This partially compliant mechanism is comprised of a wedge cam with a compliant follower. The designer specifies the material and geometric properties of the compliant segment, as well as a desired force-deflection profile. A cam surface is then synthesized that helps generate this profile. The synthesis method is validated experimentally with the help of two case studies. Some possible areas of application include robotics, variable stiffness actuators, electrical connectors, design for automotive crashworthiness, and variable resistance exercise equipment

Bistable Compliant Four-Bar Mechanisms with a Single Torsional Spring

Significant reduction in cost and time of bistable mechanism design can be achieved by understanding their bistable behavior. This paper presents bistable compliant mechanisms whose pseudo-rigid-body models (PRBM) are four-bar mechanisms with a torsional spring. Stable and unstable equilibrium positions are calculated for such four-bar mechanisms, defining their bistable behavior for all possible permutations of torsional spring locations. Finite Element Analysis (FEA) and simulation is used to illustrate the bistable behavior of a compliant mechanism with a straight compliant member, using stored energy plots. These results, along with the four-bar and the compliant mechanism information, can then be used to design a bistable compliant mechanism to meet specified requirements