Characterization of Leg Push Forces and Their Relationship to Velocity in On-Water Sprint Kayaking

The purpose of this work was to describe the leg-muscle-generated push force characteristics in sprint kayak paddlers for females and males on water. Additionally, the relationship between leg pushing force characteristics and velocity was investigated. Twenty-eight paddlers participated in the study. The participants had five minutes of self-chosen warm-up and were asked to paddle at three different velocities, including maximal effort. Left- and right-side leg extension force were collected together with velocity. Linear regression analyses were performed with leg extension force characteristics as independent variables and velocity as the dependent variable. A second linear regression analysis investigated the effect of paddling velocity on different leg extension force characteristics with an explanatory model. The results showed that the leg pushing force elicits a sinus-like pattern, increasing and decreasing throughout the stroke cycle. Impulse over 10 s showed the highest correlation to maximum velocity (r = 0.827, p < 0.01), while a strong co-correlation was observed between the impulse per stroke cycle and mean force (r = 0.910, p < 0.01). The explanatory model results revealed that an increase in paddling velocity is, among other factors, driven by increased leg force. Maximal velocity could predict 68% of the paddlers’ velocity within 1 km/h with peak leg force, impulse over 10 s, and stroke rate (p-value < 0.001, adjusted R-squared = 0.8). Sprint kayak paddlers elicit a strong positive relationship between leg pushing forces and velocity. The results confirm that sprint kayakers’ cyclic leg movement is a key part of the kayaking technique.

Kinematic parameters of crawl swimming in swimming athletesfrom images captured with the aid of home artifacts as a support of equipment for filming

Analysis of the underwater movements of a swimmer is of fundamental importance in sports, given that the characterization of the propulsion of swimming takes place in the submerged phase of the movements. Given this finding, this homemade artifact built from materials available on the market, such as PVC pipes and fittings; skateboard wheels and roller skates, and relatively low cost, may or may not positively influence the performance of professional and amateur athletes, to improve sports performance and prevent injuries. The objective of this pilot study, for possible collections for sample calculation, was to verify the effectiveness of a home model of support for the cameras during the capture of images for the analysis of movement, in swimming athletes. The study proposed as a method to couple two Go Pro Hero4 cameras to the homemade artifact, one submerged to capture underwater images and another above water level that served for observation of the aerial phase of the stroke, as well as for better framing during the capture of the real-time images, transmitted to the tablet placed on the artifact, which was conducted by an operator positioned on the edge of the pool and moved parallel to the athlete during the execution of the swim. One female swimming athlete from the city of Campos dos Goytacazes-RJ was selected, who performed a 25-meter crawl test, which consisted of two 25-meter shots, with an active range of five minutes between them.For the analyses, the angulations of the lower limbs (ankle, knee, and hip), hip leveling, and the time of the complete stroke cycle, as well as the time of the respective half-cycles, were taken into account. It is concluded that this home artifact modelof support for biomechanical analysis of swimming was able to present its effectiveness relative to the purpose, with the obtainment of images subject to analysis. However, there is a need for additional studies, as in compliance with the decrees related to social isolation, it was not possible to film underwater a larger number of athletes, as well as their respective analyses.

A tail’s tale: Biomechanical roles of dorsal thoracic spine of barnacle nauplii

Many marine invertebrates have complex life histories that begin with a planktonic larval stage. Similar to other plankton, these larval invertebrates often possess protruding body extensions, but their function beyond predator deterrence is not well-documented. For example, the planktonic nauplii of crustaceans have spines. Using the epibiotic pedunculate barnacle Octolasmis spp., we investigated how the dorsal thoracic spine affects swimming and fluid disturbance by comparing nauplii with their spines partially removed against those with intact spines. Our motion analysis showed that amputated Octolasmis spp. swam slower, in jerkier trajectories, and were less efficient per stroke cycle than those with intact spines. Amputees showed alterations in limb beat pattern: larger beat amplitude, increased phase lag, and reduced contralateral symmetry. These changes might partially help increase propulsive force generation and streamline the flow, but were insufficient to restore full function. Particle image velocimetry further showed that amputees had a larger relative area of influence, implying elevated risk by rheotactic predator. Body extensions and their interactions with limb motion play important biomechanical roles in shaping larval performance, which likely influences the evolution of form.

Development of a Two-Stroke Cycle Engine for Use in the Agricultural Aviation Sector

Reciprocating internal combustion engines have wide application in agricultural, recreational and experimental aircraft, resulting from their low cost and less complex maintenance compared to other engines. Thus, this work analyzed the performance of a conventional four-stroke engine operating in the two-stroke cycle by means of direct fuel injection and mechanical air supercharging. The use of a supercharger was essential in this design to provide adequate gas exchange inside the cylinder during the long valve overlap required, while direct fuel injection made it possible to reduce the short circuit of air-fuel mixture to the exhaust. Due to the double ignition frequency compared to a four-stroke engine, it was possible to obtain a large power density (40 kW/L) at a speed of 2400 rpm, also a specific fuel consumption of 270 g/kWh with gasoline and 400 g/kWh with ethanol. The use of ethanol in replacement of gasoline made it possible to operate at full load (160 Nm/L) at 800 rpm without the occurrence of knocking combustion.

Coordination changes in front-crawl swimming

We report the evolution of the coordination with velocity in front-crawl swimming which is used in competitions over a large range of distances (from 50 m up to 25 km in open-water races). Inside this single stroke, top-level swimmers show different patterns of arm organization. At low velocities, swimmers select an alternated stroke with gliding pauses during their propulsion. The relative duration of the gliding pauses on a stroke cycle is independent of the velocity in this first regime. Above a critical velocity, the relative duration of the gliding pauses starts to decrease as speed increases. Above a second critical velocity, the gliding pauses disappear and the swimmers start to superpose their propulsion phases. These three regimes are first revealed experimentally and then studied theoretically. It appears that below the first critical velocity, swimmers use a constant coordination index and vary their speed by varying their propulsive force to minimize their cost of propulsion. For larger velocities, swimmers use their maximum propulsive force and vary their recovery time to increase further their speed. The physical model developed is general and could be applied to understand other modes of locomotion.

2019 Nominations for ASME Historic Mechanical Engineering Landmark Status: Rail Transportation Category

The ASME Rail Transportation Division submitted five nominations in 2019 for ASME Historic Mechanical Engineering Landmark status. The nominations are for examples of significant railway technologies involving mechanical engineering and built between 1920 and 1964: 1. SBB 14253 “Crocodile” locomotive (1920): pioneering electric heavy-duty Swiss mountain locomotive, with pioneering features found in many subsequent electric locomotives. 2. Winton 8-201 prototype diesel engine (1933): only surviving of two experimental engines which preceded all GM-Electro-Motive 2-stroke cycle diesel engines for locomotives and other applications; first locomotive diesel engine with lightweight welded steel crankcase and unitized fuel injectors. 3. B&O 50 locomotive (1935): sole surviving example of the first (5) standalone, modular, non-articulated high-speed diesel locomotives from Electro-Motive, functional prototypes for the later “E” passenger and “FT” freight locomotives. 4. Cooper-Bessemer prototype diesel engine (1953): sole surviving example of (4) predecessor 4-stroke cycle diesel engines built for GE Transportation for field test locomotives prior to GE becoming a domestic locomotive manufacturer. 5. SP 9010 locomotive (1964): sole surviving example of (21) experimental German-built diesel locomotives for heavy-duty US mountain railroad operation using a hydromechanical torque converter transmission instead of electric traction motors; proved concept of higher-power and improved wheel-to-rail adhesion. All five nominations were submitted to the ASME national History & Heritage Committee for review. This paper provides a description of each nomination and the status of each proposed railroad Historic Mechanical Engineering Landmark.

Two-Stroke Wankel Type Rotary Engine: A New Approach for Higher Power Density

The Wankel engine is a rotary type of four-stroke cycle internal combustion engine. The higher specific power output is one of its strong advantages. In Wankel rotary engine, every eccentric shaft revolution corresponds to one four-stroke cycle, whereas conventional reciprocating engine fulfills four-stroke cycle in two crankshaft revolutions. This means the power stroke frequency is twice that of conventional engines. Theoretically, application of two-stroke cycle on Wankel geometry will duplicate the power stroke frequency. In this research, a single-zone thermodynamic model is developed for studying the performance characteristic of a two-stroke Wankel engine. Two different port timings were adapted from the literature. The results revealed that late opening and early closing port geometry (small opening area) with high supercharging pressure has higher performance at low speed range. However, as the rotor speed increases, the open period of the port area becomes insufficient for the gas exchange, which reduces power performance. Early opening and late closing port geometry (large opening area) with supercharging is more suitable in higher speed range. Port timing and area, charging pressure, and speed are the main factors that characterize output performance. These preliminary results show a potential for increasing power density by applying two-stroke cycle of the Wankel engine.

Analysis of the applicability of a common rail pump for an aircraft engine

The paper presents an analysis of the possibility of using a common rail pump to supply an aircraft compression-ignition engine. It is an engine with a two-stroke cycle, three cylinders, opposing pistons and 100 kW power. Its each combustion chamber is supply by one or two injectors controlled by electromagnetic valves. In order to assess the possibility of using a common rail pump, four high-pressure pumps were tested on a bench. They are piston pumps differing in the number and geometry of their pumping sections. The analysis included the pumping output, the torque on the pump drive shaft and the power needed to drive the pump. The weight and overall dimensions of the pump were also considered, including the arrangement of the pumping sections and the way the drive is transmitted. The research allowed to optimize the engine power supply system depending on fuel demand and the way the pump is mounted on the engine.