Inertial Properties of Football Helmets

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
James R. Funk ◽  
Roberto E. Quesada ◽  
Alexander M. Miles ◽  
Jeff R. Crandall
Keyword(s):  
Athletic Performance ◽  
Center Of Gravity ◽  
Moment Of Inertia ◽  
Head Protection ◽  
Hybrid Iii ◽  
Football Helmets ◽  
Male Hybrid ◽  
The Moment ◽  
Athletic Equipment

The inertial properties of a helmet play an important role in both athletic performance and head protection. In this study, we measured the inertial properties of 37 football helmets, a National Operating Committee on Standards for Athletic Equipment (NOCSAE) size 7¼ headform, and a 50th percentile male Hybrid III dummy head. The helmet measurements were taken with the helmets placed on the Hybrid III dummy head. The center of gravity and moment of inertia were measured about six axes (x, y, z, xy, yz, and xz), allowing for a complete description of the inertial properties of the head and helmets. Total helmet mass averaged 1834±231 g, split between the shell (1377±200 g) and the facemask (457±101 g). On average, the football helmets weighed 41±5% as much as the Hybrid III dummy head. The center of gravity of the helmeted head was 1.1±3.0 mm anterior and 10.3±1.9 mm superior to the center of gravity of the bare head. The moment of inertia of the helmeted head was approximately 2.2±0.2 times greater than the bare head about all axes.

scholarly journals Control system based on tracking balance car

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
Yuechang Shi ◽  
Mingwei Xu ◽  
Jiuxin Gong
Keyword(s):  
High Speed ◽  
Center Of Gravity ◽  
Moment Of Inertia ◽  
Stable Operation ◽  
Running Speed ◽  
Approach Angle ◽  
Car Model ◽  
Departure Angle ◽  
The Moment ◽  
The Impact

For balanced cars, to achieve high-speed and stable operation, two efforts should be made. The first is to make the center of gravity of the car model as low as possible, which is conducive to upright stability. The second is to make the quality as concentrated as possible. Make the vehicle's steering more flexible and reduce the vehicle's moment of inertia. At the same time, the approach angle and departure angle of the car are very important considerations, because the running speed of the car model requires the car model to maintain a certain forward inclination to obtain acceleration. When the car model goes uphill, it also needs to consider the impact of the slope. Hanging the chassis requires a certain distance from the ground while lowering the center of gravity. The battery is the heaviest piece in the entire car. The location of the battery almost determines the height of the center of gravity, the size of the moment of inertia, and the departure angle of the approach angle. In order to reduce the noise of the car to the accelerometer and gyroscope, the sensor should be installed as low as possible.

scholarly journals Exploration of Center of Gravity, Moment of Inertia, and Launch Direction for Putters with Ball Speed Normalizing Face Properties

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 2
Author(s):  
Jacob Lambeth ◽  
Dustin Brekke ◽  
Jeff Brunski
Keyword(s):  
Weight Distribution ◽  
Design Strategy ◽  
Center Of Gravity ◽  
Moment Of Inertia ◽  
Sweet Spot ◽  
Ball Speed ◽  
Impact Location ◽  
The Face ◽  
The Moment ◽  
Novel Design

The forgiveness of golf putters is traditionally achieved through weight distribution. Putters are often designed with large footprints, which help to increase the moment of inertia (MOI), but consequently move the center of gravity (CG) farther behind the face. The use of higher MOI putters will result in less ball speed loss on impacts away from the sweet spot (i.e., more forgiveness). It has been shown that certain face properties, such as milling patterns, grooves, or soft inserts, can be leveraged to have a similar effect. This paper explores the relationships between impact location, MOI, CG depth, discretionary mass placement, and launch direction for these putters. A novel design strategy is proposed. Minimizing CG depth for putters with ball speed normalizing face properties, even at the expense of MOI, can result in more consistent launch direction and distance control for the average player.

Lamboley Test of EC-12 Model Yachts

1995 ◽  
Vol 32 (01) ◽  
pp. 33-42
Author(s):  
Lon Robinson ◽  
Larry Robinson
Keyword(s):  
East Coast ◽  
Center Of Gravity ◽  
Simultaneous Equations ◽  
Moment Of Inertia ◽  
Radius Of Gyration ◽  
Pendulum Test ◽  
The Moment ◽  
Righting Moment ◽  
Boat Speed

Comparative evaluations were conducted using a Lamboley pendulum test to determine the radius of gyration in the pitch axis and to locate the center of gravity of the East Coast 12-Meter (EC-12M) model sail yachts. The Lamboley simultaneous equations were solved using a computer programmed for this purpose. From these data, the righting moment at 20 deg heel and the moment of inertia in the pitch axis, without the rig, were calculated and plotted. Critical pitching frequencies were calculated, assuming a nominal mast and rig; and critical wavelengths were calculated and plotted versus boat speed.

Perception of the moment of inertia of hand tools

1982 ◽  
Author(s):  
Carol Zahner ◽  
M. Stephen Kaminaka
Keyword(s):  
Moment Of Inertia ◽  
Hand Tools ◽  
The Moment

Research on the identification of the moment of inertia of PMSM for industrial robots

2020 ◽  
Author(s):  
Chuanwen Zhang ◽  
Guangxu Zhou ◽  
Ting Yang ◽  
Ningran Song ◽  
Xinli Wang ◽  
...  
Keyword(s):  
Industrial Robots ◽  
Moment Of Inertia ◽  
The Moment

On the nuclear equilibrium deformation and the moment of inertia of the band

1971 ◽  
Vol 34 (4) ◽  
pp. 255-256 ◽  
Author(s):  
S.A. Hjorth ◽  
J. Oppelstrup ◽  
G. Ehrling
Keyword(s):  
Moment Of Inertia ◽  
Equilibrium Deformation ◽  
The Moment

New Theorems for Moments of Inertia

1993 ◽  
Vol 21 (4) ◽  
pp. 355-366 ◽  
Author(s):  
David L. Wallach
Keyword(s):  
Regular Polygon ◽  
Moment Of Inertia ◽  
Regular Polygons ◽  
Centre Of Mass ◽  
Moments Of Inertia ◽  
The Moment

The moment of inertia of a plane lamina about any axis not in this plane can be easily calculated if the moments of inertia about two mutually perpendicular axes in the plane are known. Then one can conclude that the moments of inertia of regular polygons and polyhedra have symmetry about a line or point, respectively, about their centres of mass. Furthermore, the moment of inertia about the apex of a right pyramid with a regular polygon base is dependent only on the angle the axis makes with the altitude. From this last statement, the calculation of the centre of mass moments of inertia of polyhedra becomes very easy.

Dynamic Modeling of the Torsional Vibration of the Slewing Mechanism of a Hydraulic Excavator

2012 ◽  
Vol 253-255 ◽  
pp. 2102-2106 ◽  
Author(s):  
Xu Juan Yang ◽  
Zong Hua Wu ◽  
Zhao Jun Li ◽  
Gan Wei Cai
Keyword(s):  
Torsional Vibration ◽  
Natural Frequencies ◽  
Planetary Gear ◽  
Moment Of Inertia ◽  
Hydraulic Excavator ◽  
Planetary Gear Trains ◽  
Vibration Model ◽  
Gear Trains ◽  
The Moment ◽  
Relationship Of

A torsional vibration model of the slewing mechanism of a hydraulic excavator is developed to predict its free vibration characteristics with consideration of many fundamental factors, such as the mesh stiffness of gear pairs, the coupling relationship of a two stage planetary gear trains and the variety of moment of inertia of the input end caused by the motion of work equipment. The natural frequencies are solved using the corresponding eigenvalue problem. Taking the moment of inertia of the input end for example to illustrate the relationship between the natural frequencies of the slewing mechanism and its parameters, based on the simulation results, just the first order frequency varies significantly with the moment of inertia of the input end of the slewing mechanism.

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