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In many applications, control system equations are being processed in a digital computer. Digital-to-analog (D/A) converters are then used to make command signals compatible with analog final control elements. It is more desirable to design a highly integrated system which uses a digital servo and does not require D/A conversion. However, digital hydraulic servo valves have not yet been highly developed, and some types are quite complex. It was the object of this program to design a hydraulic digital servo which uses the standard, proven two-stage electrohydraulic servo valve. This was done by having the servo valve itself perform the function of a D/A converter. It accepts digital signals in computer format and quantizes actuator velocity. Initial design studies were performed, followed by analog and digital computer studies. A breadboard unit was built and evaluated. Two main conclusions have thus far been reached: 1.

This paper presents a recent development in single-stage servovalve design. The new concept offers unique performance capabilities which overcome some of the serious shortcomings of conventional single-stage servovalves. In addition to the physical description of the new design, a performance comparison is made with existing single-stage and two-stage servovalves. Emphasized in this comparison are closed-loop system accuracy and hydraulic power utilization; performance areas where conventional single-stage valves have been notoriously deficient. Hydraulic flow forces acting on a nozzle-flapper valve are utilized to advantage in the new design. A section of this paper discusses these forces and presents empirical data on typical servovalve configurations.

The new type of fluid device described in this paper is closely analogous to a vacuum tube cathode follower amplifier. It provides an output pressure equal to an input control pressure, but with a high input impedance and low output impedance providing a power gain. A string of balls moving in response to pressures acting on the ball surfaces provides the basic valve action. Because of its structure and the use of balls as the control elements, this device is relatively easy to manufacture, does not require a lubricating fluid and can be operated at high temperatures.

The temperature dependence of various physical properties of alumina and beryllia ceramics are presented along with some important chemical and nuclear considerations. Properties in the cryogenic temperature regions are stressed. The data presented will be a composite of information gained in the Research Laboratory of Coors Porcelain Company and from literature sources on cryogenic properties of alumina and beryllia material.

The actuation system for the Saturn V S-IC stage is described and compared to the Saturn I system. The use of mechanical feedback actuators that result in a significant increase in system reliability and the damping of load resonance is discussed. The unprecedented component sizes and system requirements are cited. The components of the S-IC stage engine gimbal actuation system are similar to and a direct evolution of those used in the Saturn I vehicle system. The major system components are the fluid supply, a filter manifold, lines, and the actuators. The system is the essence of simplicity. As a fluid power source, fuel is taken directly in a single path from the high pressure side of the engine turbopump. Flow from the actuators is returned to the fuel system rather than to a reservoir. Because of the small number of components and the design concepts used, the reliability of this system is high.

This paper describes the engine actuation system for the second stage (S-II) of the Saturn V vehicle. Four separate hydraulic systems provide thrust vector control for the vehicle during S-II boost by positioning the four gimbaled engines. A summary of the resulting system and component design and performance characteristics is included. Methods of controlling contaminants and controlling the temperature of the system in a cryogenic environment are also presented.

This paper discusses the mechanical, hydraulic, and heat transfer aspects of designing a hydraulic system to gimbal the engine on the Saturn S-IVB Booster Stage. This stage requires restart capability after a moderate period of orbital coast. The design configuration which satisfies the overall functional and environmental requirements is shown. Specific areas of discussion include: 1. Design of a hydraulic pump assembly which must be mounted on an accessory pad which may be as cold as -297°F before pump operation and subjects the pump installation to thermal shock (-297°F to +900°F) during operation. 2. Design of an electric motor driven hydraulic pump for operation in the vacuum of space. The results of certain laboratory tests which have been conducted pursuant to the development of the system are discussed.

Power-amplified actuation systems for space vehicles are becoming a necessity with the advent of manned, lunar-mission space vehicles. Various actuation system types must be evaluated to appraise their ability to withstand the severe low-temperature and hard-vacuum environments that will be encountered. Problems must be solved through extensive analysis and breadboard test programs to ensure optimum subsystem selection and prove reliability before detailed design of space vehicles. This paper reviews a lunar-vehicle hydraulic system analysis and development program. The actuation tasks of many types of advanced space vehicles are determined. Subsystem trade studies presented for some of these tasks include evaluation of hydraulic, pneumatic, and electromechanical approaches to control requirements determined. The problems of developing hydraulic systems for long stay times in severe lunar environments are discussed.

A simple evaporation method for cooling cryogenic liquids to their normal boiling point, or lower, is presented. The method employs a relatively small, in-line device, known as the vortex subcooler, to accomplish rapid mass transfer cooling without the use of moving parts. The unit induces partial vaporization of the liquid in a vortex tube through localized pressure reductions. The performance of a small unit, based on the continuity, momentum, and general energy equations, is developed and the theoretical results for superheated water, liquid nitrogen and liquid hydrogen are shown. These theoretical results compare favorably with experimental results obtained from a prototype unit, of comparable size, operating with superheated water.

This paper explores some of the actual and potential uses of the computer within the construction industry. A detailed analysis of computer applications in the areas of accounting and control, equipment management and estimating, engineering, and job management are discussed. The feasibility and economics of renting a computer system or buying computer time is delved into. The most significant advantage of a computer system is that current, up-to-date information becomes available. upon which to base management decisions.

Significant changes in the Army's maintenance program are discussed. The most important is the emphasis on equipment reliability and maintainability. For new equipment under development, specifications such as MTBF or minimum periods between servicing are being established. For field equipment, for example, inspection schedules have been altered, test gear has been modernized, and new maintenance techniques have been developed. Equipment Service Criteria, the Army' s graduated pattern of maintenance support, the standards for such support, the Army Equipment Record System, and the Early Support Concept are also described.

An example of an alternating current electric drive system is described together with a discussion of the control system. An estimate of current status of this type of drive system is presented together with future projections. Challenges exist for improvements which could alter the future projections and some of these are discussed. Only generalized conclusions are drawn on the applicability of these drives for industrial application.

The results of theoretical and experimental research are presented to demonstrate the importance of matching or “tuning” the fundamental time parameters of the excitation characteristics of compaction equipment with the time parameters of the soil being compacted. This “tuning” is a very important economic factor in practical situations where large masses of earth materials must be placed and compacted very rapidly to desired specifications. The degree of tuning is expressed as the ratio of the time of loading or excitation to the characteristic time parameter of the soil compactor system. Operational response at proper values of the time ratio may well give maximum efficiency for compactive effort. Fundamental time parameters of the soil as well as the soil compactor system are needed for proper compaction equipment design. These parameters are presented using theoretical analyses of rheologic systems and comparison with static and dynamic response spectra of actual soils.

A new entry into the field of electric power generation is the fuel cell. This is an energy conversion device which needs a supply of fuel and oxidant from an external source. The greatest interest shown in the fuel cell to date is for use in marine propulsion; however, interest has been shown in its application to vehicle propulsion.

This paper described the compaction of earth, rock, and natural local materials used in the construction of roadbeds for highways. A historical survey of compaction is presented, as are proper methods of compaction, proper amount of compaction, and cost of compaction.

Utilizing suitable techniques and equipment, job operating conditions can be measured on an earthmoving machine. Recordings of these measurements are a guide to establishing laboratory test procedures and aid evaluation of the results for predicting component life expectancy. With such information, the engineer has an effective tool for designing a reliable product.

A study to define accurately and discover new parameters of productivity for the contractor has resulted in a new design concept in off-highway trucks. This new concept has been first applied in the International Model 180 Payhauler, a rear dump vehicle of 45 ton rated capacity. The function and form criteria are discussed by components and systems in terms of the complete vehicle and on the job applications.

Piston engine air cleaners available today provide acceptable engine protection. Justification of expensive self-cleaning or automatic air cleaners of the future must be on the basis of costs - total costs which include maintenance cost as well as initial or original cost of the air cleaner. The authors present the broad facets of measuring total costs, relate them to present day air cleaners and project them to the self-cleaning air cleaner. It is concluded the self-cleaning air cleaner is needed and can be justified on the basis of lower total costs in certain applications. In projecting the data, the field and lab performance and maintenance experience obtained on the Cooper-King Self-Cleaning Air Cleaner was used as a bench mark.

A major shortcoming of many reliability programs is that they are initiated after the product is in production. Reliability prediction in the earliest design phase of a totally new product is an effective means of assuring proper emphasis and direction of the development program. This paper discusses the application of failure mode identification and analysis relative to a new product without benefit of field failure data. The procedure to accomplish this purpose is explained and appraisal methods are also described.