An improved rotable mass for a flywheel characterized by a plurality of coaxially aligned, contiguous disks mounted on a spin shaft is presented. Each disk of the plurality is formed by a plurality of woven fibers disposed in a plane transversely related to an axis of rotation with the fibers of alternate disks being continuous throughout their length. The mid-portion of the fibers of the remaining disks of the plurality is removed for defining annular voids concentrically related to the spin shaft

Weyler, G. M., Jr.

English

NASA Technical Reports Server

United States Patent 
Weyler, Jr. 
[54] ROTATABLE MASS FOR A FLYWHEEL 
[75] Inventor: George M. Weyler, Jr., Huntsville, 
[73] Assignee: The United States of America as 
Ala. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
1211 Appl. No.: 632,111 
[22] Filed: NOV. 14, 1975 
[51] Int. C1.2 ............................................... GO5G 1/00 
[52] U.S. Cl. ................................... 74/572; 15/230.16; 
15/230.17; 29/125; 428/133 
[58] Field of Search .................. 74/572; 428/133, 138, 
428/212; 15/230.12, 230.16, 230.17; 29/125 
[561 References Cited 
U.S. PATENT DOCUMENTS 
188,670 3/1877 Poole ................................. 29/125 X 
4,098,142 
WI Jul. 4, 1978 
520,516 5/1894 Cleary ............................... 15/230.17 
2,027,425 VI936 Hall ................................... W230.16 
3,296,886 VI967 Reinhart, Jr. .......................... 74/572 
3,788,162 VI974 Rabenhorst ............................ 74/572 
Primary Examiner-Samuel Scott 
Assistant Examiner-Randall Heald 
Attorney, Agent, or Firm-L. D. Wofford, Jr.; John R. 
Manning 
VI ABSTRACT 
An improved rotatable mass for a flywheel character- 
ized by a plurality of coaxially aligned, contiguous disks 
mounted on a spin shaft, each disk of the plurality being 
formed of a plurality of woven fibers disposed in a plane 
transversely related to an axis of rotation with the fibers 
of alternate disks being continuous throughout their 
length, while the midportion of the fibers of the remain- 
ing disks of the plurality is removed for defining annular 
voids concentrically related to the spin shaft. 
3 Claims, 3 Drawing Figures 
12 
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U S .  Patent July 4, 19-78 4,098,142 
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It is, therefore, apparent that even though substantial 
ROTATABLE MASS FOR A FLYWHEEL efforts have been made to improve rotary energy stor- 
age devices by fabricating the rotatable masses of such 
devices from fibers characterized by low density and ORIGIN O F  THE INVENTION 
The invention described herein was made by an em- 5 exhibiting high tensile strength characteristics, further 
ployee of the United States Government and may be advances in the design and fabrication of rotatable 
manufactured and used by or for the Government for masses for energy storage devices are highly desirable, 
governmental purposes without the payment of any or even necessary, in order to enhance the adaptability 
royalties thereon or therefor. and use of such devices in the continuing effort to ac- 
10 quire a solution to the problem of efficiently utilizing 
available energy. BACKGROUND O F  THE INVENTION 
1. Field of the Invention It is, therefore, the general purpose of the instant 
The invention relates to energy storage devices, and invention to provide an economic and practical rotat- 
more particularly to an improved rotatable mass for an , able mass for a flywheel which is characterized by in- 
energy storage device adapted to be employed as a 15 creased energy storage capabilities and an operational 
flywheel. life of increased duration. 
Because of the so-called energy crisis, renewed inter- 
est has been experienced for energy storage devices 
capable of storing energy obtained at low costs for use 
under different conditions at later periods of time, 
As discussed in Scientific ~ ~ ~ r i ~ ~ ~ ,  December, 
and have long been used for storing energy. However, 
until recently it thought that the use of flywheels 
was severely limited due to factors including weight of 
the rotatable mass forming the rotor, and fabrication 
costs. 
OBJECTS AND SUMMARY OF THE 
INVENTION 
20 It is, therefore, the object of the instant invention to 
provide an improved rotatable mass for a flywheel. 
flywheel which overcomes the aforementioned disad- 
vantages and difficulties, without sacrificing the recog- 
It is another object to provide a durable rotatable 
mass for a flywheel which is economic to fabricate and 
practical to employ in storing inertial energy. 
the increased stress encountered when increased angu- 
1973, Volume 229, No. 6, flywheels are notoriously old It is another Object to provide a rotatable mass for a 
25 nized energy storage characteristics thereof. 
As is known* the amount Of energy which can be It is another object to provide an improved rotatable stored in a flywhee1 depends largely the weight Of 30 mass for a flywheel which is capable of the rotatable mass and the angular velocity at which the 
mass is caused to spin. The limit of the amount of en- 
ergy which can be Of a 
of the material from which the mass is made. 
lar velocities are imposed thereon. in the These and other objects and advantages are achieved 
35 tiguous disks, each being fabricated from a plurality of 
woven fibers, mounted on a common, concentrically 
most suited related shaft, the fibers of alternate disks being continu- 
for use in fabricating a rotatable mass for a flywheel are ous while the midportion of the fibers of the remaining 
characterized by low density and high tensile strength. disks are removed for defining annular voids, as will 
Recently, efforts have been directed to developing ro- 40 become more readily apparent by reference to the fol- 
tatable masses for flywheels from such materials. The lowing description and claims in light of the accompa- 
results of such efforts are typified by the devices de- nying drawings. 
scribed in the disclosures of U.S. Pat. Nos. 3,296,886, 
3,788,162and 3,859,868. BRIEF DESCRIPTION O F  THE DRAWINGS 
FIG. 1 comprises a perspective view of a flywheel 
continue to be plagued by the destructive effects Of including an improved rotatable m a s  which embodies 
stress, both tangential and radial, which results from the principles of the instant invention. 
angular velocities operatively imposed on flywheels. FIG. 2 is a fragmented cross-sectional view taken 
For example, flywheels having a solid mass of thick- generally along line 2-2 of FIG. 1. 
ring configuration, formed from CirCumferentiallY 50 FIG. 3 is a fragmented, partially sectioned top plan 
wound glass fibers, embedded in an epoxy, fail at speeds view of the rotatable mass shown in FIG. 1. 
flywheel ultimately is determined by the tensile Strength through the use of a plurality of coaxially aligned, con- 
2. Brief Description Of The Prior Art 
It has been suggested that the 
However, those engaged in the design of flywheels 45 
far below the limit set by the tensile strength of the 
fibers. Usually, this is because of progressively worsen- DESCRIPTION OF THE PREFERRED 
ing radial delamination within the rotary masses of the EMBODIMENT 
flywheels. 55 Referring now to the drawings wherein like refer- 
Additionally, where a flywheel mass is mounted on a ence characters designate like or corresponding parts 
shaft extended through an opening formed therein by throughout the several views, there is shown in FIG. 1 
removing materials from the center of the mass, the a flywheel, generally designated 10, including a rotat- 
flywheel is subject to failure, due to the resulting able mass 12 which embodies the principles of the in- 
stresses in the zone immediately adjacent to the opening 60 stant invention. 
formed by the removal of the materials. In instances The mass 12 is, as shown, affixed to a spin shaft 14 
where fibers are arranged in parallelism and then which supports the mass for rotation in order to store 
bonded together for forming a disk-shaped rotary mass, inertial energy, in accordance with principles will un- 
in a manner such that the fibers lie along cords of the derstood by those familiar with the design and opera- 
mass, the flywheel is subject to failure during high 65 tion of flywheels. 
speed operations, for substantially the same reasons as The mass 12 comprises a plurality of laminated disks 
are flywheels formed from circumferentially wound 16 and 17 which are bonded together to form an inte- 
glass fibers, as hereinbefore discussed. grated structure. Each of the disks 16 and 17 consists of 
3 
4,098,142 
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a plurality of orthogonally related fibers 18 woven to through conventional weaving techniques and the disks 
form a relatively fine mesh or screen. The specific mate- 16 and 17 can be bonded together and to the spin shaft 
rial from which the fibers 18 are formed is varied as 14 utilizing commercially available epoxy, the mass 12 
desired. It is to be understood, however, that the mate- can be fabricated economically. Of course, the number 
rial from which the fibers 18 are formed possesses high 5 of disks employed is varied as desired, however, it is 
tensile strength characteristics. Such material is typified noted that the disks 16 should be disposed in alternate 
as titanium, steel, molybdenum, and fused silicon, as juxtaposition with the disks 17 in order that the voids 20 
well as various synthetic and organic fibers. readily can be utilized in accommodating the axial ex- 
As can be appreciated with those familiar with the pansion of the material of the disk 17 as the fibers are 
design and operation of energy storage devices which 10 separated for receiving the spin shaft 14. Moreover, by 
utilize basic principles of the flywheel, the radial and employing a woven material in forming the disks, the 
tangential stresses tend to be greater near the inner radii ease with which separation of the fibers is effectcd for 
of the employed rotatable mass and drop to a minimum receiving the spin shaft 14 is greatly enhanced. 
at near outer radii. Of course, the rotatable energy storage device which 
Therefore, as is best illustrated in FIG. 3, the fibers 18 15 embodies the principles of the instant invention is par- 
of alternate disks 17 are, during fabrication of the ticularly adapted to be statically and dynamically bal- 
flywheel 10, spread apart near the midportion thereof a anced. 
distance sufficient for receiving the spin shaft 14 with- Although the invention has been herein shown and 
out fracturing fibers. Of course, the spreading of the described in what is conceived to be the most practical 
fibers tends to displace the material of the disk and to 20 and preferred embodiment, it is recognized that depar- 
increase the thickness or axial dimension of the disk tues may be made therefrom within the scope of the 
about the periphery of the spin shaft 14. Thus a thick- invention, which is not to be limited to the illustrative 
ened midsection is imparted to each of the disks 17. In details disclosed. 
order to accommodate the increased thickness of the I claim: 
disks 17, the midsection of the fibers of adjacent disks 16 25 1. An improved rotatable mass for a flywheel com- 
are severed and circular portions are removed from the 
centers of the disks 16, whereby annular voids 20 are a mass including a plurality of contiguous, coaxially 
formed at opposite sides of each thickened midsection related disks, each disk being formed of a plurality 
of the disks 16 for receiving the material displaced from of woven fibers disposed in a plane transversely 
disks 17, as illustrated in FIG. 2. related to an axis of rotation extended through the 
The disks 16 and 17 are bonded together utilizing ally mass, thc fibers of alternate disks being continuous 
suitable bonding material such as epoxy resins and the throughout their length; and 
like and thereafter similarly bonded to the spin shaft 14. a spin shaft extended through the mass in concentric 
Thus the mass 12 is bonded into an integrated body relation with said axis of rotation. 
rigidly affixed to the spin shaft. 2. The device of claim 1 wherein the midportions of 
The improved rotatable mass 12 of the instant inven- the fibers of the disks interposed between the alternate 
tion, when driven in rotation, tends to more efficiently disks are removed for forming an annular void concen- 
employ the tensile strength of fibers 18 due to their trically related to said spin shaft. 
interwoven and directional relationships. Further, be- 3. The energy storage device of claim 2 wherein said 
cause the fibers 18 of disks 17 have uninterrupted 40 alternate disks are bonded to said spin shaft and the 
lengths, the strength of the mass 12 is enhanced, near disks interposed between the alternate disks are bonded 
the inner radii. Since the materials from which the mass to said alternate disks. 
12 is fabricated can easily and readily be provided 
prising: 
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60 
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Rotatable mass for a flywheel

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