RD-RI59 622 TRANSHISSION ACOUSTIC VIBRATION TESTING(U) UNITED via TECHNOLOGIES CORP STRATFORD CT SIKORSKY AIRCRAFT DIV C YOERKIE ET AL. JUL 85 USAAVRACON-TR-83-D-34 UNCLASSIFIED D AAK5I92- - 82-CSSF/61/3 NL I0013EI sonl*. mommmmoii-m NNNNNEl
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RD-RI59 622 TRANSHISSION ACOUSTIC VIBRATION TESTING(U) UNITED viaTECHNOLOGIES CORP STRATFORD CT SIKORSKY AIRCRAFT DIVC YOERKIE ET AL. JUL 85 USAAVRACON-TR-83-D-34
UNCLASSIFIED D AAK5I92- - 82-CSSF/61/3 NL
I0013EI sonl*.lf.~fmommmmoii-mNNNNNEl
1.8.
1111L2 111.
NATION -W EUO TNAOS-16
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AD-A159 022USAAVRADCOM TR-83-D3-34
TRANSMISSION ACOUSTIC VIBRATION TESTING
C. Yoerkie, A. Chory
SIKORSKY AIRCRAFT DIVISIONUNITED TECHNOLOGIES CORPORATIONStratford, Conn. 06602
July 1985
Final Report for Period September 1982 - November 1983
App roved for public release;distribution unlimited. I
Prepared forAVIATION APPLIED TECHNOLOGY DIRECTORATEU.S. ARMY AVIATION RESEARCH AND TECHNOLOGY ACTIVITY (AVSCOM)Fort Eustis, Va. 23604-5577
DU IiLL WrAVSCOM - PROVIDING LEADERS MhE DECISIVE EDGE
85 09 09 012. . . . . . . . . . .
AVIATION APPLIED TECHNOLOGY DIRECTORATE POSITION STATEMENT
%-, This report provides comparative acoustic (high frequency) vibration data on a baseline BLACK' HAWK helicopter main transmission and three experimental configurations of that gearbox. Tests
were limited because of the existence of only one set of experimental hardware: a stainless steelhousing and a high contact ratio planetary gearset. A significant result involving harmonics abovethe planetary mesh frequency offers a challenge for additional research.
Mr. M. L. Pedersen of the Propulsion Technical Area, Aeronautical Technology Division, served asproject engineer for this effort.
DISCLAIMERS
The flndings in this report are not to be construed a an official Department of the Army position unless sodeignated by other authorized documents.
When Government drawinga, specifications, or other duta are used for any purpose other then in connection with adefinitely related Government procurement operation, the United States Government thereby incurs no responsibility
* nor any obligation whatsoever; and the fact that the Government may have formulated, furnished, or in any waysupplied the said drawinga, specifications, or other data is not to be regarded by implication or otherwise as in anymanner licensing the holder or any other person or corporation, or conveying any rights or permission, to manu-facture, use, or sell any patented invention that may in any way be related thereto.
Trade names cited in this report do not constitute an official endorsement or approval of the use of such
commercial hardware or software.
DISPOSITION INSTRUCTIONS
Destroy this report by eny method which precludes reconstruction of the document. Do not return it to theoriginator.
. -.' ". , . ... ...- --..... •.. ° ...... -o. .••o..- - - - - . .- - - ,- .,oo.,
UnclassifiedauCURaev CLASSPICATSON OF THIS PAGE
REPORT DOCUMENTATION PAGEaREOT SECURITY CLASSIFICATION lb. RESTRICTIVE MARKINGS
Unclassified_______________________21L SECURITY CLASSIFICATION AUTHORMITY 3. OISTRIBUTION/AVAILAMILITY OF REPORT
Approved for public release;ft OECLASSIPICATIONIOOWNGRADING SCH4EDULE distribution unlimited.
&. PORMING ORGANIZATION REPORT NUMBER(SI S. MONITORING ORGANIZATION REPORT NUMBERS)
USAAVRADCOM TR 83-D-34
a AEOP PERFORMING ORGANIZATION lb6 OFFICE SYMBOL 7&. NAME OF MONITORING ORGANIZATION
Sikorsky Aircraft Division (if6UaPD e) Aviation Applied TechnologyUnited Technologies Corporation[I Directorate
S.ADORESS (City. Stt and ZIP COduI 7b. AOOR11681 (City. State ond ZIP Code)
U.S. Army Aviation Research and Tech-Stratford, CT 06602 nology Activity (AVSCOM)
______________________________Fort Eustis, Virginia 23604-5577S.NAME OP PUNOING)SPONSORING h.OFF ICIE SYMBOL 9. PROCUREMENT INISTRUMENT IDENTIFICATION NUMBER
ORGANIZATION (if apPl~eable)
Sa. ADDRESS ICity. State 410d ZIP Code) 10. SOURCE OP FUNDING NOS.
PROGRAM PROJECT TASK WORK UNITELEMENT NO. NO. NO. NO.
63201A I LM62018372 01 0" EK11. TITLE linclud' S.aurity CkeM'I~eation)Transmission Acoustic Vibration Testing_______________________
12. PERSONAL AUTHORMS
C. Yoerkie, A. Chory13&. TYPE Of REPORT 131;6 TIME COVERED 14. DATE OF REPORT (Yr.. Mo..7a) 15. PAGE COUNT
F Final P ROMSA_2 TO NV9July 1985 75IS. SUPPLEMENTARY NOTATION
17. COSATI COOES a. SUBJECT TIERMSJ~onllnu on reveme if necempry and Identify by block numuber)
P1 iLO GROUP I sue. an. elico ter.Transmssion - -Steiftess Steel HousingHigh e'ontact gKatio AQars; .near Reash Fi~equency;Buttress ?ooth R2ears _- Acoustic.Milbration -<'
ABSTRACT (Continue on a,..,.. if necenov and identify by block numnbar)
T,'Laboratory tests were conducted to determine the individual and combined effects of ahigh contact ratio (HCR) planetary gearset and a stainless steel housing on the acoustic(high frequency) vibration signature of the BLACK HAWK helicopter main transmission.Vibration levels at the planetary mesh frequency increased significantly with thestainless steel housing, but increased unexpectedly with the HCR planetary. The primaryreason for the increased response with the 1.ICR was the reduced gear Iface wid s.
211 OISTRI*UTION/AVAILABILITY OF ABSTRACT 21. ABSTRACT SECURITY CLASSIFICATION
12.NAMEP RESPNIBLED 1 SNIVAL AS1 TELEHON NUBE D. OUFICE SYMBOLssiie
UtNLAMSE RUPNLIBLED9 E IVUAS RPb. TEEHN DTMBC USERS OFIC UncassfieL.~ 804)ud 87-40 mAeRTTY-ATL. ~ ~ ~ ~ ~ Inld Pedrse C0)oda40)SVR-Y-
*DO FORM 1473,83 APR EDITION OF I JAN 73 IS OBSOLETE. UnclassifiedSECURITY CLASSIFICATION OF THIS PAGE
PREFACE
This report presents the results of a test program conductedfrom October 1982 through November 1983 by Sikorsky Air-craft, Division of United Technologies Corporation, unoerApplied Technology Laboratory Contract DAAK51-82-C-0040.
Technical monitorship for the effort was provided by Mr. M.L. Pedersen of the Applied Technology Laboratory, U.S. ArmyResearch and Technology Laboratories (AVSCOM)* with signifi-cant assistance from Mr. J. Coy of the Propulsion Laboratory,U.S. Army Research and Technology Laboratories (AVSCOM) andMr. F. Oswald of the NASA-Lewis Research Center. Projectmanagement was under the direction of Mr. J. Mancini, withTechnical direction provided by Messrs. J. Kish and L. Hager.Technical support was provided by Messrs. C. Yoerkie, A.Chory, P. Arcidiacono, R. Schlegel, H. Frint, and R. Haven.
, j,
°'"X"
*Redesignated Aviation Applied Technology Directorate, U.S. ArmyAviation Research and Technology Activity (AVSCOM), effective1 July 1985.
iii
• ...... . . • • , - . - . . . . . . 4 - 4 - - . - 4 . . 4 . . . . 4 4 4 4 . , .. o . - , - . . ° ° . o , . • - , . ° . . , . . .-''' -44- '" .4- '"-4,7 "- . -"""." '. ."."." -" ,--" " -- ,.-.- ''.-.-.- . . - - -" """"""""-""-". - ," - ' "- " -
TABLE OF CONTENTS
Page
PREFACE . . ............ ....... iii
LIST OF ILLUSTRATIONS ............... vi
LIST OF TABLES ........... ...... .... ix
INTRODUCTION ................. ..... . 1
TEST HARDWARE .............. ..... . . 3
General . ..... ............. 3Housing .. ..... ............ 6Planetary Gearset. . ........... . 8Test Configurations. ........ . .... 18
INSTRUMENTATION ................ . 19
TEST FACILITY ........................ . 27
PROCEDURE................... . 31
RESULTS AND ANALYSIS ............... 32
Cabin Noise and Acoustic Vibration ...... . 32Wide Band Levels .............. 36Effects of Power and Speed .... ......... 44Narrow Band Levels....... . . .... 51Explanation of Sidebands . . . .. . . . ... 56Planetary Gearset Variation..... .. . .. 58Summary ....... .................. 71
CONCLUSIONS ....... .................... ... 74
RECOMMENDATIONS .................. 75
..
9-
LIST OF ILLUSTRATIONS
Figure Page
1 Gearbox and Acoustic Treatment WeightTrends ......... .................. 1
2 UH-60A BLACK HAWK Helicopter ... ....... 3
3 BLACK HAWK Drive System ..... .......... 4
4 BLACK HAWK Main Transmission ... ....... 4
5 Baseline Gearbox Cross Section ... ....... 5
6 Experimental Gearbox Cross Section . ... 6
7 Baseline Magnesium Housing .... ........ 7
8 Fabricated Stainless Steel Housing . ... 8
9 Standard Contact Ratio Gearing ... ...... 9
10 High Contact Ratio Gearing .... ........ 9
11 Buttress Tooth Form .... ............ .. 10
12 Baseline Planetary .... ............ .. 11
13 Experimental Planetary ... .......... ... 11
14 HCR Spacer and Bearing Nut . ........ ... 12
15 HCR Sun Gear ..... ............... ... 12
16 HCR Planet Gear/Bearing ..... .......... 13
17 HCR RingGear.... .................. 14
18 HCR Planetary Assembly ... .......... ... 14
19 Instrumentation System .......... 20
20 Baseline Gearbox Accelerometer Scheme . 21
21 Instrumented Transmission Overall View . 22
22 Accelerometers on Left Foot .. ........ ... 23
23 Accelerometers on Left Side .. ........ ... 24
24 Accelerometers on Right Side ....... 25
vi
LIST OF ILLUSTRATIONS (Continued)
Figure Page
25 Accelerometers on Rear ..... ..... ... 26
26 Transmission Test Facility .. ....... ... 28
27 Test Facility Schematic ... .......... ... 29
28 Test Facility Console ..... ........... 30
29 BLACK HAWK Cabin Sound Pressure Levels . 34
30 Baseline Gearbox Acceleration Levels . . . 35
31 Baseline Gearbox PSD (Sheet 1) . ...... . 37
32 Baseline Gearbox PSD (Sheet 2) ... ...... 38
33 HCR Planetary PSD (Sheet 1) .... ........ 39
34 HCR Planetary PSD (Sheet 2) .... ........ 40
35 Steel Housing PSD .... ............. ... 41
36 Steel Housing and HCR Planetary PSD . ... 42
37 Production Gearbox PSD ..... .......... 43
38 Vibration Levels at Planeatry Mesh(Comparing Planetaries) ... .......... ... 45
39 Vibration Levels at 2X Planetary Mesh(Comparing Planetaries) ... .......... ... 46
40 Vibration Levels at Planetary Mesh(2000 SHP) ...... ................ ... 47
41 Vibration Levels at 2X Planetary Mesh(2000 SHP) ...... ................ ... 48
42 Vibration Levels at Planetary Mesh(Comparing Housings) .. ........ ..... 49
43 Vibration Levels at 2X Planetary Mesh(Comparing Housings) .. ........... ... 50
44 Narrow Band Acceleration Levels (MagnesiumHousing) ........ ................. 53
vii
. . . . . . . . . . . ..o
7 7 7 TO I
LIST OF ILLUSTRATIONS (Continued)
Figure
45 Narrow Band Acceleration Levels (SteelHousing) ........................ . 54
46 Narrow Band Acceleration Level Repeat-ability ..... .................. 55
47 Tooth Pitch and Spacing Variations . . .. 58
48 HCR Sun Gear Lead ... ............. 59
49 HCR Sun Gear Profile ..... ........... 60
so HCR Sun Gear Pitch, Spacing and Index(Drive Side) .................... . . 61
51 HCR Sun Gear Pitch, Spacing and Index(Coast Side). ................... 62
52 HCR Ring Gear Lead .... ............ .. 63
53 HCR Ring Gear Profile . ........... . 63
54 HCR Ring Gear Pitch, Spacing and Index(Drive Side) ................ 64
55 HCR Ring Gear Pitch, Spacing and Index(Coast Side) ................. 65
56 HCR Planet Gear Lead ... ........... ... 66
57 HCR Planet Gear Profile .............. .. 67
58 1CR Planet Gear Pitch, Spacing and Index(Drive Side/Ring Gear Mesh) .......... ... 68
59 HCR Planet Gear Pitch, Spacing and Index(Coast Side/Sun Gear Mesh)......... . . . 69
60 NASTRAN Calculated Natural Frequencies. . . 73
viii
.~~ ~~~~~ ~~~~ ~~~~~ -. ' -- -- -- -' -, -. -° --*-
-. , '-"- .-.- -°-. .-.-. .-.- . . . . . .
LIST OF TABLES
Table Page
1 Planetary Gears Tested ... .... ..... 15
2 Sun-Planet Gear Mesh Data . . . .. . .. . 16
3 Planet-Ring Gear Mesh Data .... ........ 17
4 Accelerometer Identification ... ....... 20
5 Test Sequence ..... ............... ... 31
6 BLACK HAWK Main Gearbox Frequencies .... 33
7 Planetary Mesh Sideband Frequencies .... 52
8 Baseline Planetary Tooth Measurements . . . 70
iX
..............
INTRODUCT ION
Transmission acoustic (high frequency) vibration signatureshave become increasingly important because of the weightpenalty associated with soundproofing material required toprotect the helicopter cabin. As gearboxes have becomelighter because of technology advances generally relat-d tostructural efficiency, more acoustic treatment has beenrequired because the noise generated by the transmission hasincreasesd (Figure 1).
1500- MAIN GEARBOX _
& ACOUSTIC TREATMN
WEIGHT10-
(LB)
MAIN GEARO0
o I --147 ,N7 1977 1987
DESIGN CALANDER YEAR
Figure 1. Gearbox and Acoustic Treatment Weight Trends.
The increased noise from lighter weight helicopter trans-missions can be attributed to increased gear tooth deflec-tions, higher strain density of the shafting, less energydissipation, higher vibration inherent in thin-walled hous-ings, and higher dynamic loads transmitted from the trans-mission to the airframe.
.L["
• - " : " | " k ' I i'" " '" - "& p" " |' - = ' °'' '"' " ' " '' . - o- ,", * .* • 1
The objective of this program was to assess the effect of twoadvanced technology components, a stainless steel housing anda high contact ratio planetary gearset, on gearbox vibrationin the range of frequencies important to cabin noise. Fromthese comparative vibration signatures, an inference of theeffect of these components on cabin noise could be attempted.A more rigorous assessment would require testing severalsamples of each design on an aircraft to account forstatistical variations and for program mounting dynamics;such an evaluation was beyond the scope of this effort.
2
........................................ ....... .......
. .
TEST HARDWARE
GENERAL
The BLACK HAWK helicopter (Figure 2) is the Army's advancedtwin-engine utility helicopter manufactured by SikorskyAircraft.
Figure 2. UH-60A BLACK HAWK Helicopter.
Two GE-T700 turboshaft engines deliver power to the BLACKHAWK drive system. The drive system (Figure 3) consists ofthe main gearbox, which combines engine power, drives themain and tail rotors, and provides secondary subsystem power;the drive shafts, which deliver power to the tail rotor; andthe intermediate and tail gearboxes, which provide the properspeed and angle changes for the tail rotor drive system.Rotational speed is reduced from 20,900 rpm at the enginesto 258 rpm at the main rotor and 1190 rpm at the tail rotor.
The BLACK HAWK main transmission was used as the baseline inthese acoustic vibration tests. This gearbox (Figure 4)weighs 1245 lbs, including the oil cooler and blower andrelated hardware; the gearbox rating is 2828 SHP. It is ofmodular construction which permits interchangeability of theleft and right input modules and accessory sections.
3
*TAIL
GEAR B X -
TAIL ROTOR
OIL COOLER DRIVE BHA"T
OIL COOLERSLOWER
MAIN ROTOR
INPUT MODLE AFEABO
MAIN TRANSMISSION[4
ACCESSORY ENGINESECTION
Figure 3. BLACK HAWK Drive System.
Figure 4. BLACK HAWK Main Transmission.
4
A cross section of the baseline gearbox is shown in Figure 5.Power from two bevel input pinions is combined at the mainbevel gear and is transmitted to a single-stage, fixed ringgear planetary unit, the carrier of which is attached to themain rotor shaft; maximum power (takeoff rating) per inputmodule is 1414 SHP.
ACCINOIONYMIODULE A
ENGINEO
INPU Cam TAX TAKE*Of1
DNIVE SHAFTINGGEAAR
moutingueeh to tOUNGrmu by FOOT
INPUT
PINION e d teA r
SUN OEMM
-PLANET
IENGINF PLANET
Figure 5. Baseline Gearbox Cross Section.
The ring gear is attached to the main housing near themounting feet, which attach the transmission to the airframe.vibrations induced by gearbox internal components and espe-cially by the planetary gearset and the transfer of thosevibrations to the airframe cabin impact significantly oninternal cabin noise. Since an experimental, housing andplanetary gearset for the BLACK HAWK transmission weredeveloped under a previous program (Reference 1), thesecomponents were appropriate and available for evaluation inthis vibration survey. A cross section of the experimentalgearbox is shown in Figure 6.
1. Advanced Transmission Components Investigation - SteelHousing, Planetary Gearing, and Bearing Development,Sikorsky Aircraft, USAAVRADCOM TR 82-D-11, Applied Tech-nology Laboratory, U.S. Army Research and TechnologyLaboratories (AVSCOM), Fort Eustis, Virginia (to bepublished).
5
0OUTE SHAFT
SMAIN HOUSING"-" PINION
lierad tu ssmbyweg 110 ous Thehouinincrpoaerou mounting. feet.and ontn inrfo-w
o.,v r GEARr ,
- HOUNTING
.iut mloduleasnd aeitailg takeoffnassebl.r outioad to mciig h' posiion thenfis maintrcnro back etgs are loatds onThe
lin~exernad suc ofstemlwehi0ons Th housing
6OOTINPU Touls n a a t e a. Ma
oi o *hePINION' m nrt c brackets r l a on the
M ~~~~~ ~ ~ RM GEARl ufc o h huig
PLANEENGIN
°ooM
DRVENO
Fiue6 xeimna eroCosScin
HOUIN
The baeiehuig(iue7 sasn odZ4Amgeiumalycsigwihn 5 pud ro omciig h
hosn isteoiihmcie.ndwih 0 ons h
mahie catnosfte ih44sus ies uhns
an.net o sebyo hetasiso opnns h
lie n tdasml eg 1 ons h osn
Figure 7. Baseline Magnesium Housing.
A fabricated sheet metal stainless steel main housing wasdeveloped as an experimental replacement for the magnesiumhousing (Reference 1). This housing would be suitable forelevated temperature operation and has good corrosion resis-tance. The principal design criteria for the fabricatedhousing were stiffness equal to or greater and weight 20% lessthan the baseline housing.
The fabricated housing consists of a sheet metal shell withwelded stiffening ribs and load bearing struts (Figure 8).The ribs and struts provide the load bearing paths for theinput modules and tail takeoff module and transfer rotorloads to the airframe; the shell reacts shear loads and re-tains the lubricating oil.
The basic structure consists of a frustrum of a cone. Themain rotor shaft upper bearing support ring is welded to thetop of the cone. A flanged ring is welded at the base of thecone and provides the mounting surface for the planetary ringgear. The flanged ring includes the four mounting feet andthe support for the internal straddle mount, which bolts intothe fabricated housing and serves as the outer shaft lowerbearing support and as the combining pinion bearing supports.The two inputs are cylindrical housings with flanged ringswhich house the combining pinions and support the inputmodule housings. A cylindrical housing with a flanged ringsupports the tail takeoff.
7
1 " "o -"'1 .' -' • " ",' '-'' "" ' .. . ' % ' ' ' ' ' ' .' ' ' ' " ' ' ' "
Figure 8. Fabricated Stainless Steel Housing.
PLANETARY GEARSET
In a conventional, standard contact ratio spur gearset thecontact ratio falls between one and two (Figure 9). In highcontact ratio (HCR) gearing the contact ratio is alwaysgreater than two and a minimum of two teeth will be in 3contact at all times (Figure 10). If the teeth are made with B
sufficient accuracy, which is the case in most helicoptergears, the high contact ratio gearset has the property oftooth load sharing. Thus, for the same face width, the loadper tooth is reduced and the resulting tooth stresses arereduced.
Another approach would be to use the same allowable stressesand thereby reduce the face width and hence gear weight(Reference 1). In combination with the HCR gearing, teethcan be further strengthened by buttressing, where unequalpressure angles exist on the driving and driven sides of thetooth. Figure 11 illustrates an HCR buttress tooth gearhaving a 20-degree pressure angle on the driving side and a23-degree pressure angle on the coast side. For the sametooth thickness at the pitch circle, tooth thickness isincreased at the base on the coast side, thus reducing toothbending stresses. With the buttress feature, the advantagesof the 20-degree drive side pressure angle are retained;lower pressure angles increase the contact ratio and reducegear separating loads, presumably leading to smoother,quieter operation.
9
. . . . . . . . .
.. . . . . . . . . . . . . . . . . . . . . . .
FIITIA POINTOF CONTAOT CONTACTN
TRANSESSRE PLAN
AINGLAEOU
TRANSVERSE PLANE O OTC
Figure 0. Higdar contact Ratio Gearing.
SIUTAEU
......................* ~ ~ ~ FIA P... .OINT.%.'
I
, PRESSURE ANGLE 2 -- ADRIVE SIDE 2 PRESSURE ANGLE
PITCH
Figure 11. Buttress Tooth Form.
The baseline planetary consists of a cantilevered planetcarrier with spherical roller bearings (Figure 12). Theplanetary receives power from the main bevel gear through afloating spline on the sun gear and transfers it to the mainrotor shaft through a locked spline in the carrier.
The experimental HCR buttress planetary (Figure 13) issimilar in design to the baseline planetary but has threemajor differences:
1. Face widths were reduced approximately 15% to saveweight by taking advantage of the increased strength ofthe HCR gear teeth.
2. The spherical roller bearing outer race was integratedwith the planet gear.
3. Gear material was changed from AISI 9310 to CBS 600steel, a high hot hardness gear steel.
HCR buttress components are shown in Figures 14 through 18.
10
SPLINE
PLANET GEAR
RING EARBEARING. OUTER RACE
SPHERICAL ROLLER PLNTSUN GEA
Figure 12. Baseline Planetary.
INTEGRAL OUTERRACE/PLANET GEAR
RING GEAR
LINER PLANET CARRIER
Figure 13. Experimental Planetary.
Figure 14. HCR Spacer and Bearing Nut.
Figure 15. HCR Sun Gear.
12
•~~ ~~~~ ~~~ J--,. . - - . . . . . -. . . . . . - .. - . . ,.; .,." .. ,. .,,b 21
AAA
Ii
Bearing GearI
Assembly
Figure 16. HCR Planet Gear/Bearing.
4" 13
-I
Figure 17. HCR Ring Gear.
Figure 18. HCR Planetary Assembly.
14
Part numbers and serial numbers for the planetary gearstested are listed in Table 1. Basic gear tooth data areshown in Tables 2 and 3. Table 2 describes the sun-planetgear mesh data for both configurations. Primary differencesin gear tooth geometry are reflected by such key parametersas pressure angle, base circle diameter, and outside dia-meter. Table 3 lists data for the planet-ring gear mesh.
Table 1. PLANETARY GEARS TESTED
Nomenclature Part Number Serial Number
BASELINE PLANETARY
Planet Gear 1 70351-08171-105 00063i " 2 70351-08171-105 00070i " 3 70351-08171-105 00072
" 4 70351-08171-105 00073" 5 70351-08171-105 00074
Sun Gear 70351-08172-101 B22600020Ring Gear 70351-08177-101 B22100002
HCR BUTTRESS PLANETARY
Planet Gear 1 38017-01102-101 002" 2 38017-01102-101 005" " 3 38017-01102-101 007
" 4 38017-01102-101 008" 5 38017-01102-101 011
Sun Gear 38017-01101-101 011Ring Gear 38017-01103-101 001
15
*1I
Table 2. SUN-PLANET GEAR MESH DATA
BASELINE HCR BUTTRESSPARAMETER TOOTH FORM TOOTH FORM
Sun Planet Sun PlanetGear Gear Gear Gear
Number of Teeth 62 83 62 83
Diametral Pitch 8.857 8.857 8.857 8.857
Contact Ratio 1.676 1.676 2.186 2.186
Pressure AngleDrive Side 22o30 ' 22o30 ' 200 200Coast Side 22o301 220301 230 230
Pitch Diameter (in) 7.000 9.3711 7.000 9.3711
Base Circle Diameter (in)Drive Side 6.4673 8.6578 6.5780 8.8060Coast Side 6.4673 8.6578 .4436 8.6262
Outside Diameter (in) 7.2259/ 9.5970/ 7.3756/ 9.5970/7.2209 9.5920 7.3706 9.5920
Root Diameter (in) 6.7324/ 9.0888 6.7291/ 8.9505 B
6.7224 9.0788 6.7191 8.9405
Chordal Tooth Thickness .1758/ .1758/ .1940/ .1577/(in) .1748 .1748 .1930 .1567
Chordal Addendum (in) .1140/ .1137/ .1877/ .1129/.1115 .1112 .1852 .1104
Index Variation (in) .0008 .0008 .0008 .0008
Spacing Variation (in) .0002 .0002 .0002 .0002
Maximum True Involute 6.8073 9.1563 6.8289 9.1033/Form Diameter (in) 9.0480
Rotational Backlash (in) .003/ .003/ .005/ .005/.005 .005 .003 .003
Minimum Fillet Radius .055 .047 .032 .025*(in)
Face Width (in) 3.200 2.970 2.300 2.540
16
Table 3. PLANET-RING GEAR MESH DATA
BASELINE HCR BUTTRESSPARAMETER TOOTH FORM TOOTH FORM
Planet Ring Planet RingGear Gear Gear Gear
Number of Teeth 83 228 83 228
Diametral Pitch 8.857 8.857 8.857 8.857
Contact Ratio 1.771 1.771 2.189 2.189
Pressure AngleDrive Side 22o30 ' 220301 200 230Coast Side 220301 220301 230 200
Pitch Diameter (in) 9.3711 25.7424 9.3711 25.7424
Base Circle Dia. (in)Drive Side 8.6578 23.7828 8.8060 23.6960Coast Side 8.6578 23.7828 8.6262 24.1899
Outside (Inside on Ring) 9.5970/ 25.5215/ 9.5970/ 25.3781/Dia.(in) 9.5920 25.5165 9.5920 25.3731
Root Diameter (in) 9.0888/ 26.0368/ 8.9505/ 26.0234/9.0788 26.0268 8.9405 26.0134
Chordal Tooth Thickness .1758/ .1758/ .1577/ .1940/(in) .1748 .1748 .1567 .1930
Chordal Addendum (in) .1137/ .1151/ .1129/ .1846/.1112 .1126 .1104 .1821
Index Variation (in) .0008 .0012 .0008 .0008
Spacing Variation (in) .0002 .0003 .0002 .0002
Maximum True Involute 9.1563 25.9596 9.1033/ 25.9413Form (in) 9.0480
Rotational Backlash .005/ .005/ .005/ .005/.003 .003 .003 .003
Minimum Fillet .047 .048 .025 .025Radius (in)
Face Width (in) 2.970 2.380 2.540 2.000
17
............... .. .. - ... i . < - - ?-L-..
TEST CONFIGURATIONS
In addition to the stainless steel housing and HCR planetarygearset, a thrust-carrying cylindrical roller bearing wasdeveloped as an experimental replacement for the conventionalball-roller bearing combination on the high speed inputpinions in the BLACK HAWK transmission (Reference 1). Theseroller bearings were used in the input modules of the fourprimary gearbox configurations tested during this program(the production gearbox retained conventional ball-rollercombinations), essentially to accrue additional running time;they were not involved in this program and did not affect theresults.
The following configurations were tested:
* Baseline transmission (with input roller bearings).
* Baseline transmission with the HCR planetary (and inputroller bearings).
Baseline transmission with the stainless steel housing(and input roller bearings).
Baseline transmission with the stainless steel housingand the HCR planetary (and input roller bearings).
* Production transmission (production BLACK HAWK).
18
................................................
INSTRUMENTATION
The range of frequencies of vibration levels which poten-tially contribute to the acoustic characteristics of anaircraft is approximately 400 to 6000 Hz. The instrumenta-tion system (Figure 19) included accelerometers (B&K Model4321 triaxials at the foot locations and B&K Model 4375 else-where), charge amplifiers (B&K Model 2635), tape recorder,analyzer (HP 5423A), and plotter appropriate for theserelatively high frequency vibration measurements. Eighteenaccelerometers were installed on the main and input modulehousings. Details of locations and the transmission compo-nents contributing the primary vibration signature are listedin Table 4. Figure 20 shows the accelerometer scheme for thebaseline gearbox. An overall view of the test transmissionwith the stainless steel housing is shown in Figure 21.Detailed views of several accelerometers are shown in Figures22 through 25 (numbers are keyed to Table 4). The productionBLACK HAWK main gearbox was tested with only limited instru-mentation (two accelerometers on the ring gear, one on thetail takeoff ring, and one on the left input ring).
Prior to testing each configuration, all instrumentation andwiring were checked and calibrated. Calibration signals wererecorded on tape. The tape recorder was run at 30 inches persecond in the wide band mode to achieve optimum frequencyresponse while maintaining low phase distortion charac-teristics; one channel was reserved for voice annotation ofthe test conditions, while another channel recorded a timecode signal to facilitate subsequent data reduction. Aftereach gearbox reached a steady-state operating condition, theconditioned accelerometer signals were recorded for approxi-mately 2 minutes. This provided sufficient data for theanalyzer to produce 64 individual fast Fourier transforms foreach test condition; these 64 spectra were averaged to formeach of the composite amplitude spectra shown in this report.The analyzer was operated on auto spectrum and free runtrigger.
19
" : , ' :' -:': , ,-. . ,.. . ,.:, .-. .. . . . , . -, .
Table 4. ACCELEROMETER IDENTIFICATION
Number Location Component Direction
Main Housing
1 Forward Foot Attachment Point Longitudinal2 Forward Foot Attachment Point Lateral3 Forward Foot Attachment Point Vertical4 Left Foot Attachment Point Longitudinal5 Left Foot Attachment Point Lateral6 Left Foot Attachment Point Vertical7 Tail Takeoff Ring Tail Takeoff Bearing Vert/Radial8 Upper Right Rib Outer Shaft Longitudinal
Upper Bearing9 Upper Right Rib Outer Shaft Lat/Radial
Upper Bearing10 Upper Right Rib Outer Shaft Vertical
Upper Bearing11 Left Input Ring Combining Pinion
Bearing Vert/Radial12 Right Input Ring Combining Pinion
Bearing Vert/Radial13 Lower Flange Ring Gear Lat/Radial14 Center Cone Housing Sidewall Normal
Input Module Housings
15 Left Inner Input Gear Bearings Vert/Radial16 Left Outer Input Pinion Bearings Lat/Radial17 Right Inner Input Gear Bearings Vert/Radial18 Right Outer Input Pinion Bearings Lat/Radial
ACCELEROMETERS(BAK 4M76 a 4Ml)
GER O AMPS -RECORDER AALYZER PL OTTER
VOICE DATA REDUCTION
TIME CODE
DATA ACUIsmON
Figure 19. Instrumentation System.
20
0LATERAL/RADIAL 0 VERTICAL/RADIAL.
N @VERTICAL/RADIAL
@jLONGITUDINAL
C)LATERAL/RADIAL
0iDW ®VETICAL/RADIAL
~LONGITUDINAL -:* o -
0 VERICAURDIALNORMAL
ORDIAL/ @0ATERAL/RADIAL
Figure 20. Baseline Gearbox Accelerometer Scheme.
21
NI
Figure 21. Instrumented Transmission Overall View.
22
N°
5
Figure 22. Accelerometers on Left Foot.
23
AI
ik
Figure 23. Accelerometers on Left Side.
24
[.2
Figure 24. Accelerometers on Right Side.
25
Figure 25. Accelerometers on Rear.
26
. . . . . . . . . ... . . .
TEST FACILITY
All testing was conducted in the BLACK HAWK main transmissiontest facility (Figure 26). This facility was designed forfull load, full speed testing of production BLACK HAWKgearboxes and employs a regenerative torque principle. Thetest gearbox, six commercial gearboxes, and a slave gearboxform one or more closed mechanical loops (Figure 27). Eachclosed loop can be dynamically torqued to produce represent-ative gear and bearing loads in the test gearbox. Loading isachieved with helical gear type torquing devices which can beactivated while rotating, thus avoiding start up under load.This regenerative setup uses approximately 10 percent of thepower of a load absorber system because the drive motorssupply power only to overcome frictional losses. The slavegearbox is a production gearbox modified to operate inreverse and is used to simplify the torque loops.
The control and instrumentation consoles (Figure 28) wereadjacent to the test facility in a protected area. Althoughall key parameters were monitored with measuring devices, awindow directly behind the console allowed the operator toobserve oil leakage or other gross fault indications. Theprimary control inputs of speed and load were directly infront of the operator. Dual functioning pressure and temper-ature gages are shown on the far right, above which arewarning indicators such as chip detectors or rapid pressurechange warning lights. The buttons between the primarycontrols and gages are the motor start-up switches. Directlyto the left are the oil flow and vibration meters, used todetect low frequency vibration-induced distress in the testor facility gearboxes. On the far left are the data record-ing devices and automatic shutoff switches. The facility wascompletely controlled from this console; instrumentation forrecording acoustic vibration measurements was an independentsystem which could be interfaced with the main facility whendesired.
27
... ..............
Figure 26. Transmission Test Facility.
28
7. -----
20900 RPM 187/ P
20900 RPM
INPUT SHAFT 6001~RPM
MOTO I__ TORUIN
TAIL
GEARBOX
TEST SLAVEGEARBOX GEARBOX INPUT TORQUING
GEARBOX
DRIVE
MOTOR
REDUCTIONGEARBOX
Figure 27. Test Facility Schematic.
29
dkm.s d wm k i b n ml mx, u a : . . . , , . = . , . . ,, . ." -. . °.." ' .% " . .- .% % ' ." B% " o." . " ."
-~~~~~~~~ ~ 7 7 -. rr - .------ --
Figure 28. Test Facility Console.
30
PROCEDURE
Each test gearbox configuration was assembled and installedin the test stand and then fully instrumentated and serviced.
After satisfactory check of all instrumentation at low speedand load levels, speed was increased to 100 percent normaloperating speed and inlet lube oil stabilized at 160 ± 40F.Testing was then conducted as specified in Table 5.
Table 5. TEST SEQUENCE
Power (SHP)
Test Left Right Tail PercentCondition Input Input Takeoff Speed
1 500 500 100 1002 750 750 100 1003 1000 1000 100 1004 1000 1000 200 100.5 1250 1250 200 1006 1400 1400 200 1007 1000 1000 100 968 1000 1000 100 989 1000 1000 100 100
10 1000 1000 100 10211 1000 1000 100 10412 1000 1000 100 10613 1000 1000 100 10814 1000 1000 100 110
Power and speed were varied independently, and each testcondition was maintained for a sufficient length of time tonormalize gearbox operating parameters and record the re-quired test data. After the variable load testing, speed wasvaried in incremental steps of 2 percent (variations inhelicopter rotor speed can result from fluctuations in enginespeed or from an overspeed condition during autorotation).Data were acquired on the production gearbox at three loca-tions (with two accelerometers on the lower flange to insuretaking data at the critical ring gear location) for a fewspeeds and torques because measurements were limited to afour-channel tape recorder during this test.
31
RESULTS AND ANALYSIS
CABIN NOISE AND ACOUSTIC VIBRATION
The objective of this test was to assess the effect onvibratory excitation levels (which impact cabin acousticlevels) of the two experimental gearbox components. There-fore, it was important to identify the sources of BLACK HAWKcabin noise and the frequencies at which they are generated.Acoustic measurements were taken in the BLACK HAWK cabin witha microphone and tape recorder. These measurements and therelated analysis were conducted under a separate program(Reference 2).
The tape recordings were analyzed using fast Fourier trans-forms to identify those frequencies at which cabin noiselevels were generated. The noise level or sound pressurelevel is described as
= 20 log (P/Po) (1)
where Lp = sound pressure level in dB
P = pressure measured with sound level meter
Po = reference pressure = 20p Pascal = (20 x 10-6 Pascal)x (1 psi/6.895 x 103 Pascal) = 2.901 x 10- 9 psi
Figure 29 is a narrow band sound pressure level spectrum atthe center of the BLACK HAWK cabin with the helicopter cruis-ing at 150 kt; transmission gear mesh frequencies arelabeled. The absolute decibel levels are not shown becauseacoustic narrow band noise data are classified. Although thenominal audible range of frequencies is approximately 20 to18,000 Hz, the critical hearing range is 500 to 5000 Hz interms of both annoyance and speech interference; the plane-tary mesh and its second through fifth harmonics are clearlydominant in this important frequency range. A major path ofvibratory energy at this mesh frequency appears to be fromthe ring gear, through the housing to the attachment points,and into the airframe. This vibratory energy, once in theairframe, radiates from panels ' and windows into the cabin inthe form of acoustic energy or noise. Consequently, ringgear accelerometer vibration levels at acoustic frequenciesprovide an appropriate indicator for comparing the effect ofvarious gearbox modifications on cabin noise levels.
2. Data from Contract No. DAAJ01-73-C-0006, Flight VehicleInternal Noise Survey For The UH-60A.
32
For conventional gearing the mesh frequency is defined as
Mesh Frequency = (RPM/60) X (number of teeth) (2)
For a simple planetary (rotating input sun gear, fixed ringgear, and rotating planetary carrier for the output as in theBLACK HAWK), the planetary gear mesh frequency, fpm' is
fpm = (N s/60)(1-S/(S + R)) S (3)
where (from Tables 2, 3, and 6)
S = 62 teeth = No. of teeth on sun gear
R = 228 teeth = No. of teeth on ring gear
N = 1206.3 RPM = sun gear speedS
therefore,
fpm = (1206.3/60)(1-62/(62+228))X62 = 980 Hz (4)
Table 6. BLACK HAWK MAIN GEARBOX FREQUENCIES
RotationalSource Speed Gear Mesh(at 100% Speed) (RPM) (Hz) Teeth (Hz)
Input Pinion 5747.5 95.8 17 1628.5
Main Bevel Gear 1206.3 20.1 81 1628.5
Sun Gear 1206.3 20.1 62 1246.5
Planet Gear 450.5 7.5 - -
(about its axis)
Planet Gear 708.4 11.8 83 980.0
Ring Gear - - 228 -
Tail Takeoff 4115.5 68.6 34 2332.1
Lube Pump 3266.6 54.4 12 653.3
Output Shaft 257.9 4.3 - -
33
- . . . . ... . . . . . . .
I.'-I
I- ww >z w4 0.j z
OC WSOUND _j PPRESSURE w ZLEVEL 4 .,W 13) 9 .x I-
X, us
Mdin4.ja.
10 dB
)--
CONDITIONS: LEVEL FLIGHT AT 150KTCRUISE POWER (1000SHP PER ENGINE)
0I I I I I I02000 4000 amO
FREQUENCY (Hz)
Figure 29. BLACK HAWK Cabin Sound Pressure Levels.
Test results associated with acoustic vibration measurementsare extensive because of the number of accelerometers, thevariability in speed and power, and the wide range of excita-tion frequencies. A relative logarithmic scale was used,which gives vibration levels in decibels (dB). For ameasured acceleration the vibration or acceleration level is
L= 20 log (a (5)10 ref
" where L = acceleration level (dB)a
a = measured acceleration, in/sec2
aref = reference acceleration = 1 micro g
= (1 x 10-6 g) x (386 in/sec2 per g)
= 3.86 x 10- 4 in/sec2
8 = gravitational acceleration = 386 in/sec2
34
... ..-.- ..................................... ,......... ,,-!t;?-".;..".:,"", ,' -. :".e' "- - . ..: , " " • ' . -.,-. r~ i. ;I &,'d d mdnl t /llmld..d i
-. *i -TV -
A power spectral density (PSD) plot of the baseline gearboxvibration from the accelerometer mounted on the ring gear isshown in Figure 30. Since the value of the peak vibration isapproximately 129 dB, the measured acceleration is
a = 10 (La/20) x aref = 106.45 x 3.86 x 10-4 (6)
a = 1090 in/sec 2 = 2.82g
Using a reference acceleration shows how accelerometer mea-surements can be converted to PSD plots; the actual PSDreference is given as 1076 g 2/Hz.
140
RING GEAR ACCELEROMETER1000 SHP PER INPUT
* POWERSPECTRAL PLANETARY MESHDENSITY 120 (960 Hz)
Ids)PLANETARYUPPER SIDEBANDS
110 PLANETARY
LUBE PUMP LOWER -GEAR MESH SIDEBANDS'
100 (53z
90-
so-
070 - t
400 Soo 800 1000 1200 1400 1600
FREQUENCY (Hz)
Figure 30. Baseline Gearbox Acceleration Levels.
35
WIDE BAND LEVELS
Wide band power spectral density (PSD) plots are shown inFigures 31 through 37 for the four experimental configura-tions and the production gearbox. Plotted data were taken at
.* 100% speed and 1000 HP per input (test condition 9), selectedas typical of normal cruise conditions for the BLACK HAWK.
*" For the two configurations with the magnesium housing(Figures 31 through 34), plots include the housing sidewall,right input gear bearings, tail takeoff bearings, leftcombining pinion bearing and ring gear. For the two con-figurations with the stainless steel housing (Figures 35 and
-* 36), housing sidewall readings were not taken because theaccelerometer mount could not withstand the vibration levels.Plots for the right input gear bearings with the stainlesssteel housing were omitted since they were essentially thesame as those shown for the magnesium housing (input housingswere magnesium in all tests).
These auto spectrum plots of acceleration signals are repre-sentative of data taken from all accelerometer locations atthis test condition. The plots show vibratory response ofeach accelerometer to dynamic excitations over a frequencyband of 0-6000 Hz, vibratory response of each of the testconfigurations, and relative vibration levels for eachexcitation. The PSD reference is 10- 6g2/Hz for Figures 31through 37.
36
140
120.
PSD 100(di)
80TAIL TAKEOFF BEARINGS
ACCELEROMETER 7Go_ I I I I I
0 3O0 mm0
FREQUENCY (Hz)
140
120
PSD 100(dB)
80 LEFT COMBININGPINION BEARING
60 ACCELEROMETER 11
0 3000 6000
FREQUENCY (Hz)
140
120,
PSD(dB) 100
80.. RING GEAR
ACCELEROMETER 13
0 3000 8000FREQUENCY (Hz)
Figure 31. Baseline Gearbox PSD (Sheet 1).
37
• ' - '* ' -', '"" ' '* ' """ "r '- * : - -" • ' ' ' * ' . ' ' . ' " . " % '
*. .,
.. .- ." " % % *' " '-" - -" . ., ' '
II
140-
120
(dE) 100
HOUSING SIDEWALLACCELEROMETER 14
30O 6000
FREQUENCY (Hz)
140-
120
PSD(dB)
RIGHT INPUT GEAR BEARINGSACCELEROMETER 17
03000 000
FREQUENCY (Hz)
Figure 32. Baseline Gearbox PSD (Sheet 2).
38
............................................................................. ,,.,- immn --uumm~ --,
140-
120-
PSD 100(din)
so TAIL TAKEOFF BEARINGSACCELEROMETER 7(I
0 3000 mFREQUENCY (Hz)
140-
120-
PSD(din) 100
7LEFOT COMBINING
;F PINION BEARING601 ACELRMEE 1
0 3000 000FREQUENCY (Hz)
140-
120-
PSD
ACCELEROMETER 13
0 3000 000
* FREQUENCY (Hz)
Figure 33. 11CR Planetary PSD (Sheet 1).
39
140.
120
PSD(dBy 0
80
HOUSING SIDEWALL
ACCELEROMETER 1460 I I I 1
300 a0m
FREQUENCY (Hz)
7
140.
PSD. 100.
(dB)
80
RIGHT INPUT GEAR BEARINGSACCELEROMETER 17e oII I II
0 30QO 000
FREQUENCY (Hz)
Figure 34. HCR Planetary PSD (Sheet 2).
40
... , ., 1"4 "
140'
120-
P8D 00(dB)10
BooTAIL TAKEOFF BEARINGS
ACCELEROMETER 7s0o
0 306 6000
FREQUENCY (Hz)
140s
120-
PSD(dB) 100A
80 LEFT COMBININGPINION BEARING
60 ACCELEROMETER 11
0 3000 Go0dFREQUENCY (Hz)
140r
120-
P80 100(dBn)
soRING GEAR
ACCELEROMETER 1360. 1 1
o3000 6000
FREQUENCY (Hz)
Figure 35. Steel Housing PSD.
41
140
120-
PSD 100* (dB)
s0 TAIL TAKEOFF BEARINGSACCELEROMETER 7
0 3W6000
FREQUENCY (Hz)
140~
120-
PSD
(dB) 100 J.A k~so. LEFT COMBINING
PINION BEARINGACCELEROMETER 11
600 0 6000
FREQUENCY (Hz)
120
PS0 100
(dB)
ACCELEROMETER 13
0 3000 6000
FREQUENCY (Hz)
Figure 36. Steel Housing and HCR Planetary PSD.
42
.140}
120J
POD 100(dBn)
TAIL TAKEOFF BEARINGSACCELEROMETER 7
0 3000 e
FREQUENCY (Hz)
140'
120PSD(din) 0
so . LEFT COMBININGP INION BEARING
ACCELEROMETER 11600
FREQUENCY (Hz)
140
POD 100(dB)
60
LRO ACCELEROMETER 1361D0 1 1
0 3000 6000
FREQUENCY (Hz)
Figure 37. Production Gearbox PSD.
43
EFFECTS OF POWER AND SPEED
Speed and load sensitivities based on ring gear accelerometerdata for each configuration were plotted for the planetarymesh frequency (980 Hz) and two times the planetary meshfrequency (1960 Hz). Figure 38 shows auto spectrum plots ofacceleration signals at the planetary mesh frequency.Figures 39 through 43 compare power and speed for variouscombinations of test gearbox configurations and excitationfrequencies. By choosing a constant reference (100% of mainrotor speed), the variation of vibration levels were plottedas a function of planetary horsepower only (Figures 38 and39). These figures show vibratory power levels contained ina 125-Hz band about the central frequency. This bandwidthincludes 28 main rotor shaft modulation sidebands (14 belowand 14 above) around the planetary mesh frequency. Thisprovides a good representation of all the energy contained inthe planetary mesh and its sidebands since the sidebandlevels are approximately 20-30 dB lower than the peak at theedges of this bandwidth. The levels shown are determinedfrom
Power = 12 PSD dw (7)
where w2 -w = 125 Hz
and W1 *W = planetary mesh frequency (or twice mesh frequency)2
The PSD reference is 10-6g for Figures 38-43.
44
c-- . . . . . . .
MAGNSIDMHOBID G
4 0 . ........... ........ .................... .....• ......... .......... .., ......
: D
148~ I
00
0 0 *HCR Gears
. U Standard GearsIO U .......... ......... .. ...... .. .............
! 125 - o ,o I -s~ Ioo -o oo500 1000 1500 2000 2500 3000
Power (SHP)
5 STArSS STEEL OUING
140 .... ...
13 .
!0
0 HCR Gears130 ... Standard Gears13 0 . .. ...................... .. ....... ... ............ ............. 0 S a d r o r
125 500 100,0 1500 ZUoo 2500 3000
Power (SHP)Figure 38. Vibration Levels at Planetary Mesh
(Comparing Planetaries).
45
*.Z" -. -. -i- .i' -. '.- i.? .'- ;. . i .. .. .. . . ... .. ..-- .,. .../ -. -. , . - -.- -. .-.-- , .. - .-. .,. . - ... .- .. .- -.. ....-
140
13 8 ......................... ......................... U....... .........................
MUMo
13 6 ......................... .................................... ........ ...........
0000
0 13 4 ............. ............ ........... .- .............. ...... .. ....... .
132 .......... : ...... ............. * HCR Gearu
0 Standard Gears
130 .500 1000 1500 2000 2500 3000
Power (SHP)
STAULES STEMLHUW;-"140 I I- " I -I
1 0
13 8 ........ .... ............ .. ........ i ............e ......................................
M:
13 6 ...................................... ............. i............ ............. .............
.0>
134 . .............. ............ .......................... ........... • H R G e
:" N Standlard Gears
130
- Power (SHP)
Figure 39. Vibration L~evels at 2X PlanetaryMesh (comparing Planetaries).
446
132 0 HR GearC..-... - ..- ..130 ... -.. i -".I. . - ' - ".... ".- .-.E.".,:" ...' -'
D..' .''.2, .'.',2.',- ,,''':', ',.'"'..''-.-''-.-' 1000''. -'"."1500 .". ."2000." " 2500' . ."-", -3000' ""
145 ............I........... .......... . .. ....
0 4
130-
00D 4 160 165 116 115 120Percent Speed
145
.. .... ... .. ..
135 .... .... .... .... . ... ..
- 0 94CR Geors
- N Standard Gears
130- Y I~0o 95 100 105 110 115 120
Percent SpeedFigure 40. Vibration Levels at Planetary Mesh (2000 SHiP).
47
JI
1U2-
""14 0 . ..................... " ..... ...... .......... .......... :......................... ........
0C U1 3 6 . .. ............ ....... . --. .. ... ... ... . ... ......... .. . ... . .. . . . . . .
> 0 HICRGCoors
U Standard Gears
132- -90 95 100 105 110 115 120
Pem-ent Speed
STAINLBSS STEELHOSG142-
14 0 . . . . . ,. . . . .. . . . . . l~ ....... .... ...... ..........
13 8 .. .. ... ..... .... .... . ........ . o... .... .. .
0U
0
Z ~ 136 ..... ........... .... .....
0 HCR Gears
134 Standard Gears
1,3 4 .......... .......... .. ......... ........... ...........
132-90 16 100 '105 110 115 120
Percent Speed
Figure 41. Vibration Levels at 2X Planetary Mesh(2000 SHP).
48
140 . ........... .................. "I... ...... ................
-". * *.136 * .................................. :........................
..1..... ............ ... ..... . . ......
100
13 5 ..... ...... . .. .. ....... .. ...............
130
* . . . Magnesium Housing
1125- m
500 1000 1500 2000 2500 30Power (SHP)
H~t PLANETARY145-m-
140 .... .. ............ .. ..
125
5010 10,00 1500 20,00 2500 3000Power SHPW)
Figure 42. Vibration Levels at Planetary Mesh(Comparing Housings).
49
*~ ** . I.... ****** ****** %~* . r ..
~PLA14SARV
S1 0 ...... ................... .. ... ... ...
> .. ! oi.. ...... ............. ......... ........................ ..............
- ,,e-
1 3 0 5 0 0 -o ~ f o 1 5 6 0 z0i lo 2 i O 0 60:::Power 'k-HP)
145
1i 4 0 .......................... ............ ........... ............ ....................... .
13 5 .......................... :................... • ............ .......... ............
0 Stainless Steel Housing
0 Magnesium Housing
130 ,ooo
500 t060 15,00 2000 2500 3000
Power (SHP)
Figure 43. Vibration Levels at 2X Planetary Mesh
(Comparing Housings ).
50
7 -7%'U° "-" °°° "°""" t"''".' " "-*'" .%" "o' " ' .' o ' "". o" ° %." " ." % % Q" " °13 ' -"° 5" "- ' . "'-."* "U''° " .:' ' " : ' . : '". t .: " - . '> - . ::' " .' : " ' ":' .' "-" .".':';'€ 'b " .-- ":..".:,,",.'""; .', _. - ,, '.".,U.
NARROW BAND LEVELS
The last set of vibration plots are narrow band plots of thepower spectral density (PSD) from the ring gear accelero-meter. Figures 44 and 45 show the acceleration levels forthe narrow band range of 800 to 1200 Hz for the first fourtest configurations. The relative repeatability of gearboxvibration is shown in Figure 46, where the baseline data(from Figure 44) is compared to data from a production gear-box; vibration levels are comparable, with variations asexpected from gearbox to gearbox. In this frequency rangethe planetary mesh frequency is clearly dominant. Associatedwith the mesh frequency are its sidebands, which occur atmultiples of various forcing frequencies. Sideband fre-quencies are calculated as follows (the theory is discussedin subsection entitled Explanation of Sidebands).
fsb f ± n (ff) (8)
where fsb = sideband frequency
f = planetary mesh frequencypm
±n = upper or lower sideband multiple integers(n = 1,2,3...)
ff = forcing frequency of modulation source
Table 7 lists the significant sidebands for the planetarymesh frequency.
51
oO . ..
Table 7. PLANETARY MESH SIDEBAND FREQUENCIES
Sideband Frequencies (Hz)
Output Shaft/ Planet Pass Sun Gearn Planet Carrier (5x Carrier)
-10 937.0 765.0 779.0-5 958.5 872.5 879.5-2 971.4 937.0 939.8-1 975.7 958.5 959.90 980.0 980.0 980.01 984.3 1001.5 1000.12 988.6 1023.0 1020.25 1001.5 1087.5 1080.5
10 1023.0 1195.0 1181.0
The predominant sidebands are caused by multiples of five(number of planet gears) times the planet carrier frequency,which is the planet pass frequency; this is the rate at whichthe planet gears pass the fixed accelerometer location on thering gear (sidebands developed at 980 ±n (21.5) Hz). Whenthe mesh is directly under the accelerometer, the noise isloudest. Since the accelerometer is nearest the planet-ringgear mesh, the highest sideband is expected there. What issurprising is that the sun gear rotational modulation effectsare also present (sidebands developed at 980 ±n (20.1) Hz).Planet pass modulation cannot be eliminated; however, with anextremely accurate sun gear and no eccentricity of rotation,the sun rotational effects on sidebanding can be minimized.There appears also to be modulation caused by the outputshaft/planet carrier rotation (sidebands at 980 ±n (4.3) Hz).The PSD reference for Figures 44 thru 46 is 10"6 g2/Hz.
52
-...
.. . 4 . ... .. , .
BASELINE TRANSMISSION140
S21.5 Hz = 5X4.3=LWER SIDEBAND
Fr PLANET PASS
PSD
0
98 1Hz
Soo90 1000 1100 1200
FREQUENCY (Hz)
BASELINE WITH HCR PLANETARY140-
120-
100
800 900 1000 1100 1200
FREQUENCY (Hz)
Figure 44. Narrow Band Acceleration Levels (Magnesium Housing).
53
ISO0BASELINE WITH STAINLESS STEEL HOUSING
140-
130-
120-
PD 110-
100-
so-
701Boo 900 1000 1100 1200
FREQUENCY (Hz)
150.
140-
130-
120-
M) 110
100
BASELINE WITH STAINLESSso- STEEL HOUSING AND
HCR PLANETARY70, - - , - V
8So9o 1000 1100 1200
FREQUENCY (Hz)
Figure 45. Narrow Band Acceleration Levels (Steel Housing).
54
150BASELINE TRANSMISSION
140-
130-
P80 120-(din)
110-
100.
90
70180900 1000 1100 1200
FREQUENCY (Hz)
150-PRODUCTION GEARBOX (2nd BASELINE)
140-
130-
120-
PSD(d8n) 110-
100-
90-
so-
70.B00 900 1000 1100 1200
FREQUENCY (Hz)
Figure 46. Narrow Band Acceleration Level Repeatability.
55
EXPLANATION OF SIDEBANDS
For geared systems, there are often strong vibration compo-nents at frequencies surrounding the gear mesh frequency andits harmonics. These sideband frequencies result fromamplitude modulation and/or frequency modulation of the basicmesh frequency (Reference 3).
Amplitude modulation occurs when the excitation varies inamplitude with time even though the frequency is constant.In its simplest form, a once-per-revolution gear eccentricitywould cause amplitude modulation with the following results:
A(t) = A ( + e sin w t) sin w t (9)0 s m
where w is the basic mesh frequency, ws is the sideband
frequency, and the factor in parentheses represents theeccentric modulation at shaft frequency superimposed on thebasic mesh frequency. This can be expanded in the form
A(t) = A sin wmt + A e [cos (w m-w s)t - cos (w M+w )t] (10)
Notice that even this simple case produces three frequencies:wm, Wm-Ws , and wm+ws The first, w., is the fundamental mesh
frequency, while the second and third are the lower and uppersideband frequencies. In general, the modulation is not asimple, once-per-revolution sinusoid but has a complexwaveform which can be decomposed into a Fourier seriesrelated to shaft revolution and its higher harmonics (smallershaft angle rotations representing shorter spatial dis-tances):
A(t) = A [I + a k sin (kw t + Yk)A sin w to k~ 1~:s~ S~f Wt(11)
The expansion of this Fourier series takes the form
A(t) = A siw t + 3A Y { k(cos[(wk)t -o m 0 k= 1
(12)-cos [(wM+kIws)t + Yk )
This shows that amplitude modulation produces sidebands atall multiples of shaft speed about the mesh frequency on boththe lower (wm-kws) and the upper (wm+kws) sides.
3. Smith, J.D., Gears And Their Vibration, The MacmillanPress Limited, 1983.
56
. . . . . . . . . ..... . -. ... .....- •... ...-...-.. •.°. -. .... . . .. .. .... ....- °-..... '..-.,"o"- ".% ,.,
Frequency modulation occurs when the mesh frequency changeswith time. Even under constant shaft speed conditions, thiswill occur because of the influence of parameters such asgear tooth variation, torsional vibration of the entire geartrain, drive motor speed fluctuations, and rotor load fluctu-ations. The simplest case can be formulated as
A(t) =A sin [w t + -W sin (wt + P)I (13)0 In W S
s
which will produce an infinite number of sideband frequenciesat wm ± kws (where k = 0,1,2,3 .... ). This has the potential
of producing sideband levels which are higher than the funda-mental mesh frequency level.
57
............o. . . . . .." . . . . . . . ..". . .
PLANETARY GEARSET VARIATION
To help understand the effects of gear tooth manufacturingerrors on acoustical vibration, the HCR gears were reinspect-ed after testing; these gears showed no signs of wear, so anywear which may have occurred during testing was negligible.
The following gear tooth variations (Reference 4) weremeasured:
Pitch Variation Distance of tooth from its theoreti-cal position.
Spacing Variation Difference in the pitch variation oftwo adjacent teeth.
Index Variation Accumulation of pitch variation.
Profile Error Deviation of the tooth profile fromtrue involute form.
Lead Error Deviation along the tooth face.
]Ihe difference between pitch and spacing variation is illus-trated in Figure 47.
SPACING VARIATION -= (X2 ) - (-X 1 )
-X 1 NEGATIVE PITCH
VARIATION X2POSITIVE PITCH VARIATION
PERFECT TOOTH.* (SOLID LINE)
TOOTH 2TOOTH 1
Figure 47. Tooth Pitch and Spacing Variations.
4. AGMA Gear Handbook, Volume 1, March 1980, (P390.03)Gear Classification, Materials and Measuring Methods forUnassembled Gears.
58
Figures 48 through 59 are the gear manufacturing charts forthe HCR sun gear, ring gear, and a planet gear chosen atrandom. The manufacturing charts shown are for lead, pro-file, pitch, spacing, and index variations. Both pitchvariation and spacing variations are important parameters forhigh contact ratio gear teeth because they relate to loadsharing. Charts for the baseline (production) planetary werenot developed; however, inspection sheets were examined andare summarized in Table 8.
DRIVE SIDE 1 COAST S IDE
. -.. . . . . . 4
FACE
,~ ~ ~~OT #OT I%2TOH#2
TOOTH #3 TOOTH #3
TOOTH #4 TOOTH #4
Figure 48. HCR Sun Gear Lead.
59
" .... .. . . . . . . . . . . ..- %." -.. " . °- o. ° -'.° "- .. - -°. ° , .. .-..-. .. °, °,.. ... ...... . . . . . . . . . . . . . . .... . . .... . . . . . -... ., .. . .- . ..- - . o °
. . . . . ....................
.... .. . .... .. ..... .. RO O TOF
TOOTH
TOOOF
-TOTOOTH
FigureH 49 HC u Ga roie
... .........
-~~~s L; 1,-. -
VARIATION40 VARATINO VRIAIO
..... .... .... ....
... ... ... .. .-- * - . . . . . . . .
t.............
.~~~~~~ ... .. . . .. . .. .. .. .. . .....
.. I ..t ... ...... ..
i' rr
.001
PITCH SPACING INDEX VARIATION-VARIATION VARIATION
Figure 51. HCR Sun Gear Pitch, Spacing and Index(Coast Side).
62
_ ,. .. + + *, . .
10
, DRIVE SIDE COAST SIDE
FAC
Figure 52. HCR Ring Gear Lead.
163
F
DRIVE SIDE .001 COAST $1lDE
._....... .O . -: . . -.
_ Figure 53. Ring Gear Profile.
:" 63
%
I. , - .-- *-~~---w-r-.------'------r-..0008
(20 MICRONS.
.MEA8URED._
VARIATIONPITCHVARIATION
Figure 54. HCR Ring Gear Pitch, Spacing'andIndex (Drive Side).
64
.0008(20 MICRONS)
VARIATION INDEXVARIATION
PITCHVARIATION
Figure 55. HCR Ring Gear Pitch, Spacing and Index(Coast Side).
65
.. 30
FACEWI DTH
DRIVE SIDE COAST SIDE
PLANETS HAVE CROWNED TEETH
Figure 56. HCR Planet Gear Lead.
66
-'e-.
DRIVE SIDE on,.001 COAST SIDE
.4 .4 .1 . 3. .a
STOOTH #1 *4
I. HHH
Figure 57. HCR Planet Gear Profile.
67
PITCH SPACINGINEVARIATION VARIATIO VARIATION
.. . . .. . .
-. A ~t~- - * .~~. ' . ..... ..- . ~ ..... P % % ~ a . % ~ t J C C % ~ ' '
PITCH SPACING AINDEA!,
,.. "i"'.,... ......... A n
. . .
. .
°o
.. 0 ( MICRONS)
Fgr 59. HCR Pae Gea Pth Sai and
Figur Inde (CoH Pat SiSnGear Mesh).acngan
* 69
ON 0)
.- 44-) - 000000000000 000000000000 0 J4000 000000000000 000000000000 -id)(1 -- 4-H 000000000000 000000000000 4-) r-4") 5..j... . . . . * * C,.) 0
0 NWWMOOO 0"H N H 0 H N 0 N r-4 Mr-4 HO 4
.04-)--"000000000000 0000.*4 000000000000 d)-H4Jr H r. 000000000000 > wr-H 4 . .N .* .*. .* . . . .* .
E4-)4-)
V) 4) 0 _r4 O -4 0 -0,-N0y-4 00004 4) -- ri000000000000 44)
E4 4-. i_____P4 000000000000 4- 4
0 $
44.
8 - E-4 4-6
E-44~ (S
0)r4 K 000000000000 4)0E- 4Cl- 04 000000000000 u 9
'N~~4 00 0 00 00
4-O
E4 ' -4
OCH' 44 000 000 000
E10W P4 00 0 0 00 0 -
4~~~~ ... .*.. .. . . . . . .. . . . . . . . . . .. 14
SUMMARY
Based on the ring gear accelerometer, the primary planet meshfrequency vibration levels are higher for the NCR gearsetthan for the baseline gearset. At twice planetary mesh fre-quency, HCR levels are comparable to or slightly lower. Thechange in vibratory level with horsepower appears to be moreon the order of 3dB per doubling of horsepower rather thanthe 6dB expected value quoted in Reference 5. This 3dB trendis consistent in both the magnesium and stainless steelhousings. The trends with horsepower and speed are similarand much smoother than described in Reference 6.
The difference in vibratory power levels between the baselineand NCR gearsets is probably caused by a combination ofseveral factors. The most important of these is that the HCRgearset was initially designed and built to fully use thebenefits of HCR from a gear design, stress, and weight stand-point. Thus, for similar stress levels, the gear weightcould be substantially reduced. However, vibration ampli-tudes are related to the volume of stressed material; theHCR gears had longer teeth and apparently larger deflections.
Another factor to be considered is the effect of toothvariations on the HCR gearset. Figure 54 shows that two ringgear teeth are out of tolerance by a factor of 2 to 3 and oneplanet gear tooth had an out-of-tolerance condition of abouttwice that of the blueprint value (Table 3). This spacingvariation would increase all sidebands around the meshfrequency (References 7 and 8). This effect is reflected inFigure 44. The tolerances used for the HCR gearset were thesame as those used for the baseline gearset. Closer toler-ances may be required for HCR gears to achieve lower vibra-tion levels. It should be noted that if these sidebands werereduced, the overall power content in the bandwidth aroundthe gear mesh frequency of the HCR planetary would be lowerthan the baseline planetary, since the planetary meshharmonics are lower.
5. Mitchell, L.D.; Gear Noise: The Purchaser's and theManufacturer's View. Proceedings of Purdue NoiseControl Engineering, pp 95-106, 1971.
6. Marze, H.J., and d'Ambra, F.; Helicopter Internal NoiseReduction Research and Development: Application to theSA360 and SA365 Dauphin. Proceedings on InternationalSpecialists Symposium, NASA-Langley Research Center,Hampton VA, May 22-24, 1978.
71
*4 "o " - . .°o o * * , *. 0 -. . . . . . • . ° • . , • ,
A variety of reasons can be given for the presence of vibra-tory energy at gear mesh frequency, its harmonics, and side-bands at planet carrier speed around these harmonics. Adja-cent gear tooth pitch variation causes multiple harmonics ofonce-per-revolution except for tooth mesh frequency. Invo-lute profile variation increases gear mesh excitation and itsharmonics. Eccentricity or gear pitch line runout producesonce-per-rev gear mesh excitation and its harmonics modulatedat plus or minus all harmonics of carrier rotation (Refer-ences 7 and 8).
While high contact ratios are theoretically better for noiseand vibration, it may be that variations in contact ratio areeven more important than the actual contact ratio. For bothHCR and standard designs, special attention to profilemodification (tip relief) is necessary to account for toothdeflections. Additional factors which improve vibrationlevels are lower pressure angles and finer pitch. Lowerspeeds and lower tooth loads are also beneficial from avibration and noise viewpoint. The vibration levels aregenerally accepted (Reference 5) to be related by
Noise a 20 log V (14)%V 0
Noise a 20 log L (15)L0B
PNoise a 20 log p (16)
0
where V is speed, L is tooth load, P is power, and the suL-scripts indicate reference level. These relationshipsreflect that doubling the speed, load or power increasesvibration and noise level by about 6dB.
The stainless steel housing had higher vibratory levels thanthe baseline magnesium housing (Figures 31 through 36), whichwas an expected result. The lighter stainless steel housinghas more resonances as calculated with NASTRAN and shown inFigure 60. Higher vibratory response levels for the sameenergy flow result because of the lower mass of the structureas well as the lower damping level inherent in stainlesssteel.
7. Welbourn, D.B.; Fundamental Knowledge of Gear Noise -A Survey. The Institute of Mechanical Engineers,London, Ci17/79, July 1979.
8. Welbourn, D.B.; Gear Noise Spectra - A RationalExplanation. ASME 77-DET-38, 1977.
-" 72
4
" j~. - - . . ... .-. -
The change in vibratory level with speed is approximately 5dBover the speed range tested. The expected value would be onthe order of 1-2dB since the variation is 20 log (V/Vo).'Some variation may be caused by variations in contact ratioand load distribution with speed. Future analysis of thisdata using techniques contained in References 9 and 10 mayclarify the explanations for these differences.
MAGNESIUM HOUSING
o500 600 700 800 900 1000
FREQUENCY (Hz)
STAINLESS STEEL HOUSING
500 600 700 800 900 1000
FREQUENCY (Hz)
Figure 60. NASTRAN Calculated Natural Frequencies.
9. Mark, W.D.; Analysis of the Vibratory Excitation ofGear Systems: Basic Theory, JASA 63(5), May 1978, pp.1409-1430.
10. Mark, W.D.; Analysis of the Vibratory Excitation of GearSystems: Tooth Error Representatives, Approximations,and Application, JASA 66(6), December 1979,pp. 1758-1787.
73
CONCLUSIONS
Tests conducted under this program were limited in scope, inthat only one high contact ratio gearset and one experimentalhousing were tested; results may have been peculiar to thetest hardware. Based on the results of this effort, it isconcluded that:
1 The high contact ratio (HCR) buttress planetary hadslightly higher acoustic/vibration levels than thebaseline (standard contact ratio) planetary gearset.
2. The higher vibration levels probably resulted becausethe HCR planetary face widths were approximately 15%less than the baseline planetary, producing approxi-mately the same stress levels in each design.
3. The vibration levels of the HCR planetary were compar-able to or lower than the baseline planetary at harmon-ics above the planetary mesh frequncy.
4. The vibration at the planetary mesh frequency was higherfor the HCR planetary than the baseline planetary; thiswas true with both the magnesium and the stainless steelhousing at all accelerometer locations for all power andspeed conditions.
5. The HCR planetary had higher levels of sideband vibra-tion than the baseline planetary.
6. Vibration levels at the planetary mesh frequency for thestainless steel housing with the HCR planetary were notdirectly proportional to applied load and generallyleveled off after reaching approximately half of ratedpower.
7. The stainless steel housing had significantly highervibration levels than the magnesium housing for the sameloading conditions and with both planetary gearsets.
8. The increased vibration with the stainless steel housingis probably associated with the thin housing wallsresulting in a greater modal density and larger vibra-tion levels (because of lower mass and lower damping).
9. There continues to be a critical need for demonstratingthe effects of transmission component concepts whichattempt to simultaneously reduce system weight (gearboxand cabin noise treatment weight), increase reliability,and reduce noise.
74
RECOMMENDATIONS
1i. Additional design and testing to evaluate helicoptertransmission experimental high contact rati6' planetarygearsets is recommended to:
a. Positively identify the impact of changes in toothspacing and profile variation and in contact ratio(the proper range for quieter gears).
b. Identify the sensitivity of vibration to gear toothstress, load sharing, and general mesh smoothness.
c. Determine and correlate with design procedures theacceptable limits of sensitive parameters such asgear tooth manufacturing variations, proper contactratio range, required gear rim backup material, andpreferred pressure angles.
2. Additional design and testing to evaluate helicoptertransmission experimental housings is recommended to:
a. Investigate stainless steel housing designs whichprovide reinforcement in the form of corrugatedsheet (or equivalent method) instead of externalstructural ribs to provide increased stiffness anddamping for the housing walls.
b. Evaluate fabricated housing designs for potentialacoustic impact by testing simple shapes (such as aplate or shell) to identify wall configurationswith minimum vibration.
3. A test facility evaluation of a series of productiongearboxes is recommended, to more accurately determinethe effects of gearbox acoustic vibration on helicoptercabin noise levels, to be followed by an evaluation ofthese gearboxes installed in helicopters.
75 3716-5
FILMED
11-85
DTIC
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