Evaluation of a high performance, fixed-ratio, traction drive

A test program was initiated to evaluate the key operational and performance factors associated with the Nasvytis multiroller concept. Two sets of Nasvytis drives, each of slightly geometry, were parametrically tested on a back to back test stand. Initial results from these tests are reported. One of these units was later retrofitted to the power turbine of an automotive gas turbine engine and dynamometer tested

Evaluation of a high performance fixed-ratio traction drive

The results of a test program to evaluate a compact, high performance, fixed ratio traction drive are presented. This transmission, the Nasvytis Multiroller Traction Drive, is a fixed ratio, single stage planetary with two rows of stepped planet rollers. Two versions of the drive were parametrically tested back-to-back at speeds to 73,000 rpm and power levels to 180 kW (240 hp). Parametric tests were also conducted with the Nasvytis drive retrofitted to an automotive gas turbine engine. The drives exhibited good performance, with a nominal peak efficiency of 94 to 96 percent and a maximum speed loss due to creep of approximately 3.5 percent

Parametric tests of a traction drive retrofitted to an automotive gas turbine

The results of a test program to retrofit a high performance fixed ratio Nasvytis Multiroller Traction Drive in place of a helical gear set to a gas turbine engine are presented. Parametric tests up to a maximum engine power turbine speed of 45,500 rpm and to a power level of 11 kW were conducted. Comparisons were made to similar drives that were parametrically tested on a back-to-back test stand. The drive showed good compatibility with the gas turbine engine. Specific fuel consumption of the engine with the traction drive speed reducer installed was comparable to the original helical gearset equipped engine

Life analysis of multiroller planetary traction drive

A contact fatigue life analysis was performed for a constant ratio, Nasvytis Multiroller Traction Drive. The analysis was based on the Lundberg-Palmgren method for rolling element bearing life prediction. Life adjustment factors for materials, processing, lubrication and traction were included. The 14.7 to 1 ratio drive consisted of a single stage planetary configuration with two rows of stepped planet rollers of five rollers per row, having a roller cluster diameter of approximately 0.21 m, a width of 0.06 m and a weight of 9 kg. Drive system 10 percent life ranged from 18,800 hours at 16.6 kW (22.2 hp) and 25,000 rpm sun roller speed, to 305 hours at maximum operating conditions of 149 kw (200 hp) and 75,000 rpm sun roller speed. The effect of roller diameter and roller center location on life were determined. It was found that an optimum life geometry exists

Parametric study of manned life support systems. Volume 1 - Summary Final report, Jul. 1967 - Aug. 1968

Summary data on methodology, mission and vehicle criteria for parametric study of manned life support system

Full-scale transmission testing to evaluate advanced lubricants

Experimental tests were performed on the OH-58A helicopter main rotor transmission in the NASA Lewis 500 hp helicopter transmission test stand. The testing was part of a lubrication program. The objectives are to develop and show a separate lubricant for gearboxes with improved performance in life and load carrying capacity. The goal was to develop a testing procedure to fail certain transmission components using a MIL-L-23699 based reference oil and then to run identical tests with improved lubricants and show improved performance. The tests were directed at parts that failed due to marginal lubrication from Navy field experience. These failures included mast shaft bearing micropitting, sun gear and planet bearing fatigue, and spiral bevel gear scoring. A variety of tests were performed and over 900 hrs of total run time accumulated for these tests. Some success was achieved in developing a testing procedure to produce sun gear and planet bearing fatigue failures. Only marginal success was achieved in producing mast shaft bearing micropitting and spiral bevel gear scoring

Parametric study of manned life support systems. Volume 2 - Parametric relations and scaling law Final report, Jul. 1967- Aug. 1968

Parametric relations and scaling laws to describe manned life support system

Advanced stratified charge rotary aircraft engine design study

A technology base of new developments which offered potential benefits to a general aviation engine was compiled and ranked. Using design approaches selected from the ranked list, conceptual design studies were performed of an advanced and a highly advanced engine sized to provide 186/250 shaft Kw/HP under cruise conditions at 7620/25,000 m/ft altitude. These are turbocharged, direct-injected stratified charge engines intended for commercial introduction in the early 1990's. The engine descriptive data includes tables, curves, and drawings depicting configuration, performance, weights and sizes, heat rejection, ignition and fuel injection system descriptions, maintenance requirements, and scaling data for varying power. An engine-airframe integration study of the resulting engines in advanced airframes was performed on a comparative basis with current production type engines. The results show airplane performance, costs, noise & installation factors. The rotary-engined airplanes display substantial improvements over the baseline, including 30 to 35% lower fuel usage

Cycloidal-drive joint design for wearable exoskeletons

This thesis\u27s scope was to construct a highly back drivable and compact joint design that can be used for wearable exoskeletons specifically designed to assist with rehabilitation. A compact cycloidal gear transmission was designed to satisfy the compactness requirement while ensuring the minimum torque is required for backdriving the mechanism. The joint was designed based on the compact cycloidal drive specifications, and the backdrivability test was performed to measure the minimum torque required (1.20 Nm) to backdrive. The joint design incorporates various important features such as rotation lock feature to prevent hyperextension, a housing design that offers the benefit of using the joint for the left and right limb, a motor mount that securely holds a brushless DC motor, and a sensor bracket that securely positions a control sensor over the motor for controlling the motor position and speed. Successful evaluation of the 3D printed prototype validated the integrity of the design

More Electric Landing Gear Actuation Study

This report addresses the problem of landing gear actuation system design on more-electric aircraft (MEA). Firstly, information about more-electric aircraft and more-electric actuators was gathered and sorted. Current more-electric landing actuation system applications and researches were also summarized. Then several possible more-electric landing gear actuation concepts were identified. To evaluate these concepts, the case study method has been used. A concept aircraft “MRT7-T”, which has similar maximum takeoff weight to that of Boeing 787, has been chosen as the design case. Systems of different configurations and architectures were designed for this aircraft. In the end of this study, a comparison between different more-electric landing gear actuation systems, and also with traditional central hydraulic system was made. The best concept was proposed. More-electric actuation technology has made considerable progress in the last two decades. However, most of the applications and researches have focused on flight control actuation and brakes. Using more-electric drives for landing gear actuation has been well known to be difficult, for the reason of massive power needs and difficulties in achieving redundancy levels. Famous more-electric research projects like POA and Power-By-Wire only gave recommendation of using electro-hydrostatic actuators (EHA) in landing gear actuation. And no further information is available to the public. In this study, DHS (distributed hydraulic system), EHA (electro-hydrostatic actuator) and EMA (electro-mechanical actuator) were identified as candidate solutions. Design requirements such as retraction time, load and redundancy levels were derived through analysis. As a unique feature, landing gear kinematics concepts were also subject to optimization. Various kinematics concepts were proposed and analyzed in detail, to provide favorable loading and geometrical conditions for the systems. Kinematics design guidelines were built through discussion. Different motors such as AC induction motor, BDCM (brushless DC motor) and PMSM (permanent magnetic synchronous motor) were evaluated for use. Different system architectures were also explored. The multi-discipline optimization method has been extensively used in the design process of the systems. Firstly, each node of the actuation systems was optimized. Then optimizations were made to the systems. Performances of each system were analyzed in several aspects such as weight, power, reliability and maintenance. Comparison of different systems was made through scoring method. The results suggested that DHS, EHA and EMA are all applicable for landing gear actuation. And isolated EHA is the best