NASA Technical Memorandum 89912

AVSCOM Technical Report 87-C- 10

I Helicopter Transmission Testing at NASA Lewis Research Center

David G. Lewicki and John J. Coy Propulsion Directorate U. S. Army Aviation Research and Technology Activity-AVSCOM Lewis Research Center Cleveland, Ohio

N87-225 78

CSCL 131 Unclas SI37 0074252

Prepared for the Testing of Aerospace Transmissions Conference sponsored by the Institute of Mechanical Engineers Derby, England, June 10, 1987

L

https://ntrs.nasa.gov/search.jsp?R=19870013545 2020-02-05T10:24:46+00:00Z

HELICOPTER TRANSMISSION TESTING AT NASA LEWIS RESEARCH CENTER

David 6. Lewlcki and John J. Coy Propulsion D i r e c t o r a t e

u.S. Army A v i a t i o n Research and Technology A c t i v i t y - AVSCOM Lewi s Research Center Cleveland , Ohio 441 35

SUMMARY

The h e l i c o p t e r has evolved i n t o a h i g h l y va luable a i r mobi le v e h i c l e f o r bo th m i l i t a r y and c i v i l i a n needs. The h e l i c o p t e r t ransmission, j u s t as w e l l as engines and ro to rs , requ i res advanced s tud ies t o develop a technology base f o r f u t u r e r o t o r c r a f t advances. A j o i n t h e l i c o p t e r t ransmiss ion research pro- gram between the NASA Lewis Research Center and t h e U.S. Army A v i a t i o n Systems Comnand has ex i s ted s ince 1970. Program goals a r e t o reduce weight and no ise and t o Increase l i f e and r e l i a b i l i t y . The c u r r e n t exper imental a c t i v i t i e s a t Lewis c o n s i s t of f u l l - s c a l e h e l i c o p t e r t ransmiss ion t e s t i n g , a base e f f o r t I n gear ing technology, and a f u t u r e e f f o r t i n no i se reduc t i on technology. paper reviews the experimental f a c i l i t i e s a t Lewis f o r h e l i c o p t e r t ransmiss ion t e s t i n g . A d e s c r i p t i o n o f each o f the r i g s i s presented a long w i t h some s i g - n i f i c a n t r e s u l t s and near-term plans.

pr)

I

0 pr)

w This

INTRODUCTION

NASA Lewis has had a s t rong research program f o r a i r c r a f t mechanical com- ponents s ince the e a r l y 1940's. The h e l i c o p t e r came i n t o wide use as a m i l l - t a r y and comnercial a i r mobi le vehic le d u r i n g t h e l a t e 1940's t o t h e l a t e 1960's. By then t h e U.S. Army had a wide spectrum o f h e l i c o p t e r s i n i t s inven- t o r y a long w i t h t h e requirement t o increase t h e i r performance. Also, NASA Lewis had es tab l i shed a c a p a b i l i t y i n mechanical component research t h a t could be a p p l i e d t o h e l i c o p t e r transmissions.

A j o i n t t ransmiss ion research program was s t a r t e d I n 1970 wi th NASA Lewis and t h e Army, and cont inues t o t h e present ( r e f s . 1 t o 6) . t h e program were t o increase t h e l i f e , r e l i a b i l i t y , and m a i n t a i n a b i l i t y , reduce t h e weight, noise, and v i b r a t i o n , and ma in ta in t h e r e l a t i v e l y h i g h mechanical e f f i c l e n c y o f t h e gear t r a i n I n h e l i c o p t e r t ransmissions. i d e n t i f y advanced m a t e r i a l s and l u b r l c a t i o n schemes, as w e l l as advanced des ign concepts f o r both t ransmiss ion components and t o t a l t ransmiss ion systems. Also, in-house and u n i v e r s i t y g ran t e f f o r t s developed a n a l y t i c a l codes f o r a n a l y s i s and design. Unique experimental t e s t i n g f a c i l i t i e s were es tab l i shed a t NASA Lewis f o r t e s t i n g mechanical components, ma te r ia l s , and l u b r i c a t i o n techniques, as w e l l as demonstrat ing advanced design concepts and v e r i f y i n g a n a l y t i c a l codes.

The major goals o f

The approach was t o

The purpose o f t h i s paper i s t o review t h e c u r r e n t exper imental a c t i v i t y a t NASA Lewis on h e l i c o p t e r t ransmission t e s t i n g . A d e s c r i p t i o n o f t h e r i g s i s g i v e n along w i t h some s i g n i f i c a n t r e s u l t s . NASA Lewls c o n s i s t o f f u l l - s c a l e h e l i c o p t e r t ransmiss ion t e s t i n g , a base e f f o r t i n gea r ing technology, and a f u t u r e e f f o r t i n no i se r e d u c t i o n technology.

The present major e f f o r t s a t

NASA LEWIS TEST STANDS

The helicopter transmission program at NASA Lewis aims at conducting research on drive trains and supporting technologies for present and advanced concept rotorcraft. strength, increase life, and reduce noise. and on contracts and grants. Analytical efforts include the development of computer aided codes. optimization of transmission components and total systems. As an important part of the research program, experimental efforts are required for verifica- tion of analytical predictions. Experimental research also provides a demon- stration of advanced technology concepts and materials.

Research program goals are to decrease weight and increase The programs are performed in-house

The codes are used in design, performance analysis, and

NASA Lewis currently has six active experimental test stands associated with helicopter transmission testing. mission test stand, the 3000-hp helicopter transmission test stand, the plane- tary gear test stand, the spur gear fatigue test apparatus, the bevel gear apparatus, and the high speed gear test stand. NASA Lewis is also developing a gear noise test stand due to a current emphasis on transmission noise reduc- tion. The rigs provide analytical code verification and a baseline from which to assess the promised advantages of future design and concepts.

They are the 500-hp helicopter trans-

500-hp Helicopter Transmission Test Stand

NASA Lewis has two full-scale helicopter transmission test stands. The first, the 500-hp helicopter transmission test stand (fig. 1), was designed at the start of October 1977 and became operational in October 1979. The test stand operates on a "four square'' or torque-regenerative principle. Mechanical power is recirculated through a closed loop of gears and shafting, one of which is the test transmission. A 149-kW (200-hp) variable speed motor powers the test stand and controls the speed. Only losses due to friction are replenished by the motor since power Is recirculated around the loop. An 11-kW (15-hp) motor provides the torque i n the closed loop. This motor drives a magnetic particle clutch; the clutch output exerts a torque through a speed reducer gearbox and chain drive to a large sprocket on the differential gearbox. The magnitude of torque i n the loop is adjusted by changing the electric field strength of the magnetic particle clutch. The facility is equipped wlth torque, speed, temperature, oil flow, and oil pressure sensors to monitor operating conditions and health states.

The baseline testing was performed on the Bell 236-kW (317-hp) OH-58A heli- copter main rotor transmission (fig. 2). The OH-58A is a single-engine, land- based, light observation helicopter, serving both military (OH-58A Kiowa) and commercial (Bell Model 206 Jet Ranger) needs. The main rotor transmission is a two-stage reduction gearbox with a single spiral bevel mesh as the first stage and a three-planet, fixed-ring gear planetary mesh as the second. The overall reduction ratio of the transmission is 17.44:l. The transmission input 1s rated for use for an engine output of 210 kW (270 hp) continuous power at 6180 rpm and 236 kW (317 hp) for 5 min at takeoff. Data were collected for bevel pinion gear tooth strain measurements, bevel gear deflections, component temperatures (bearings, gears, seals, oil), vibrations, and transmission mechanical efficiencies. The testing consisted of a matrix of speed and load conditions.

2

For efficiency tests the test transmission and an oil-to-water heat exchanger were thermally insulated to provide an adiabatic enclosure. A heat balance was then performed on the water which cooled the transmission oil. The mechanical efficiency was determined by measuring the heat generation due to mechanical losses. Overall transmission efficiency for the OH-58A varied from about 98.3 to 98.8 percent at f u l l speed and load conditions and was a function of lubricant and lubricant temperature (fig. 3, ref. 7). A reasonable correlation of efficiency with lubricant viscosity was made when the vlscos- ities were corrected for temperature and pressure effects in the lubrlcated contact (ref. 8).

Vibration signals from accelerometers mounted at various locations on the OH-58A transmission housing were analyzed by using Fourier spectra, power spectral density functions, and averaging techniques (ref. 9). The Fourier spectra showed vibration amplitude peaks occurring at the spiral bevel gear mesh harmonics and planetary gear mesh harmonics (fig. 4). The highest magni- tude of vibration was at the spiral bevel gear meshing frequency. In addition, the highest measured overall broadband acceleration was about 10 g's rms (occurring at full speed and load and measured on the housing near the ring gear). The measurement location and transmission speed had a significant effect on measured vibration. Current work is being performed in analyzing the remaining OH-58A transmission data. Also, a four-planet OH-58A transmis- sion was tested and the results are being compared to the baseline three- planet.

At present the rig is used to evaluate two advanced design concept trans- missions in the 223 to 373 kW (300 to 500 hp) range. The first is the NASA/Bell Helicopter Textron (BHT) 500-hp advanced technology transmission (fig. 5). The design goal was to upgrade the OH-58C 236-kW (317-hp) version to 372 kW (500 hp) while retaining long life with a minimum increase in cost, weight, and size. during the last decade and improvements dictated by field experience (ref. 10). The major changes were to incorporate: high contact ratio planetary gears, improved bearing and gear materials, an improved planet carrier design, a cantilever-mounted planetary ring gear, an improved sun gear spline design, and a straddle mounted bevel gear. The final design had a weight to power ratio of 1.55 N/kW (0.26 lb/hp) compared to 2.21 N/kW (0.37 lb/hp) for the OH-58C transmission.

This was accomplished by implementing advanced technology developed

The 500-hp advanced technology transmission was recently tested at NASA Lewis. Similar data as that for the OH-58A were collected (strains, deflec- tions, temperatures, vibrations, and efficiencles) and the results are being analyzed. Preliminary results show the mechanical efficiency measured 98.5 percent at 82 OC (180 OF) oil inlet temperature and 98.6 percent at 99 O C

(210 OF), comparable to the OH-58A.

The second advanced design concept transmission in the 223 to 373 kW (300 to 500 hp) class is the self-aligning bearingless planetary (SABP) transmission (fig. 6). In this transmission conventional planet gears are replaced by planet spindles. The spindles each have three gears on them; one gear meshes with a sun gear, one with a fixed ring gear, and one with a rotating output ring gear. The gears on the spindle are spaced such that tan- gential gear forces are balanced and the spindles are in equilibrium. Tooth separating and centrifical forces are reacted by cylindrical rings concentric with the sun

3

gear ax i s . reducing the transmission weight. P lanet bear ing f a i l u r e s and power losses commonly associated w i t h convent ional p lanetary t ransmiss ions a re e l im- Ina ted . Also, t ransmiss ion v u l n e r a b i l i t y due t o loss o f l u b r i c a t i o n i s decreased. The design study p ro jec ted a weight savings o f 1 7 t o 30 percent and a r e l i a b i l i t y improvement f a c t o r o f 2:l over standard t ransmiss ions ( r e f . 11) . A 336-kW (450-hp) SABP t ransmiss ion r e t r o f i t t i n g t h e OH-58A was f a b r i c a t e d and i s c u r r e n t l y be ing tes ted a t NASA Lewis.

Thus, the p lanet bear ings and p lane t c a r r i e r a re e l im ina ted ,

Future plans o f t h e 500-hp t ransmiss ion t e s t stand inc lude f u l l - s c a l e t e s t i n g o f advanced l u b r i c a n t s under the U.S. Navy He l i cop te r L u b r i c a t i o n Pro- gram. Present ly, a common engine and t ransmiss ion o i l i s used i n m i l i t a r y h e l i c o p t e r s . ca t ion , and provides s a t i s f a c t o r y l u b r i c a t i o n f o r t u r b i n e engines bu t marg ina l performance f o r t ransmiss ions. He l i cop te r t ransmiss ion overhauls show an inc reas ing r a t e of bear ing and gear r e j e c t i o n s due t o sur face d i s t r e s s , cor ro - s ion, and wear. Due t o t h i s the Navy has i n i t i a t e d the U.S. Navy He l i cop te r L u b r i c a t i o n Program t o develop a separate t ransmiss ion l u b r i c a n t w i t h improved load-car ry ing capaci ty and co r ros ion i n h i b i t i o n ( r e f . 12) . The 500-hp t rans - miss ion t e s t stand a t NASA Lewis w i l l be used f o r t he f u l l - s c a l e gearbox t e s t i n g o f t he advanced l u b r i c a n t s . The 500-hp r i g w i l l be mod i f i ed t o i n c l u d e l i f t and bending loads on t h e t ransmiss ion ou tpu t s h a f t t o c l o s e r model t rans - miss ion load ing seen i n t h e f i e l d .

The o i l conforms t o e i t h e r a MIL-L-23699 o r a MIL-L-7808 s p e c i f i -

3000-hp He l i cop te r Transmission Test Stand

The second f u l l - s c a l e h e l i c o p t e r t ransmiss ion t e s t stand a t NASA Lewis i s t h e 3000-hp r i g ( f i g . 7 ) . The 3000-hp t e s t stand was designed and b u i l t by t h e Boeing Ver to l Company, re fu rb i shed by NASA, and pu t on l i n e a t NASA Lewis i n March 1981. The t e s t stand operates on a to rque- regenera t ive p r i n c i p l e . Power t o t h e t e s t t ransmiss ion f lows through two inpu ts ( s i m u l a t i n g two engines) and t w o outputs (main r o t o r and t a i l d r i v e ) . Power i s prov ided by a constant speed 600-kW (800-hp) i n d u c t i o n motor and speed i s c o n t r o l l e d by an eddy c u r r e n t c lu tch . Torque i s induced independent ly i n each loop by p lane ta ry torque u n i t s . The stand i s a l s o capable o f app ly ing l i f t loads, moment loads, and drag loads on t h e t ransmiss ion ou tpu t sha f t .

The t e s t stand was designed f o r t e s t i n g t h e U.S. Army's 3000-hp U t i l i t y T a c t i c a l Transport A i r c r a f t System (UTTAS) h e l i c o p t e r main r o t o r t ransmiss ion . Dur ing t h e UTTAS development, two p ro to type vers ions were considered by t h e Army. One was the YUH-61A h e l i c o p t e r , designed and manufactured by t h e Boeing Ver to l Company. The o ther was t h e UH-60A h e l i c o p t e r by S ikorsky A i r c r a f t . The Army eventua l l y chose t h e UH-60A (Black Hawk) f o r p roduc t ion . Both t h e YUH-61A and the UH-60A t ransmiss ions were tes ted a t NASA Lewis.

The YUH-61A h e l i c o p t e r t ransmiss ion has a r a t e d power l e v e l o f 2080 kW (2792 hp) a t an output r o t o r s h a f t speed o f 286 rpm. The t ransmiss ion has two t w i n i npu ts . Input s p i r a l bevel gears mesh w i t h a combining s p i r a l bevel gear f o r t he f i r s t reduct ion stage. The second reduc t i on stage cons is t s o f a f o u r - p lanet , f i x e d - r i n g gear p lane ta ry . The o v e r a l l t ransmiss ion r e d u c t i o n r a t i o i s 25.096:l. E f f i c i e n c y and v i b r a t i o n data were taken i n t h e 3000-hp stand ( r e f . 13). The mechanical e f f i c i e n c y measured 98.7 percent a t f u l l power.

4

The 3000-hp stand was modified to test the UH-60A (Black Hawk) helicopter transmission. speed of 258 rpm. The transmission overall reduction ratio is 81.042:l. Note that the UH-60A transmission has one more spiral bevel reduction stage in comparison to the YUH-61A transmlsslon. to accept input directly from the engines where the YUH-61A has a pair of external gearboxes between the engines and main transmission couplings. UH-60A efficiency, vibration, and gear tooth strain data were taken (refs. 14 and 15). The transmisslon's mechanical efficiency at full power was 97.3 and 97.5 percent at inlet 011 temperatures of 82 and 99 O C (180 and 210 O F ) ,

respectively. The highest vibration reading was 72 g's rms at the upper housing side wall. The largest stress found was 760 MPa (110 ksi) on the com- bining pinion fillet. Temperature and deflection data were also taken and are presently being analyzed.

The transmission is rated at 2110 kW (2828 hp) at an output

The UH-60A transmission is designed

The 3000-hp test stand Is currently inactive and no additional transmission testing is planned at this time.

Planetary Gear Test Stand

The NASA Lewis planetary gear test stand studies performance characteris- tics of planetary gear assemblies. The facility uses a regenerating torque loop where two OH-58 planetaries are mounted back-to-back with a drive motor on one end and a rotating torque actuator on the other end (fig. 8). torque actuator loads the test planetary section with respect to the slave planetary section. The drive motor provides the speed and also supplies the power to overcome friction losses. (500 hp) at 1620 rpm sun gear speed.

The

The rig is capable of delivering 373 kW

The test and slave planetaries have separate lubrication systems. Each system is comprised of 14 oil jets for lubrication of different areas of the planetary. This makes possible an extensive study of the effect of lubrication on plane- tary performance.

The oil flow through each jet can be individually controlled.

The rig became operational in March 1986 and efficiency studies of a 313-kW (420-hp) OH-58 four-planet assembly were performed (ref. 16). The planetary has a reduction ratio of 4.67:l. Parametric studies of speed, load, and lubri- cant type, temperature, and flow were run. All parameters affected efficiency and experimental results were compared to analytical predictions. Future rig plans include the study of the sun gear dynamics (strains and stresses) and comparison with analytical codes. Also, various planetary configurations such as three- or four-planet, cylindrical or spherical planet bearings, or low or high contact ratio gears are planned.

Spur Gear Fatigue Apparatus

Gear research began at NASA Lewis late in the 1960's. The work concen- trated on materials and lubrication and established a unique data base in aviation applications. The NASA Lewis gear fatigue test apparatus became operational in 1972, supplying valuable data on gear materials, lubrication,

5

and l i f e analysis. Lewi s . There are c u r r e n t l y f o u r running gear f a t i g u e r i g s a t NASA

The spur gear f a t i g u e t e s t apparatus ( f i g . 9) operates on a four-square p r i n c i p l e . One s lave gear i s equipped w i t h l oad ing vanes and o i l pressure on t h e vanes produces a torque on t h e s lave gear s h a f t . The torque i s t r a n s m i t t e d through t h e t e s t gears and back t o t h e s lave gears. The torque on t h e t e s t gears, which depends on t h e h y d r a u l i c pressure app l i ed t o the load vanes, loads t h e gear t e e t h t o the des i red s t ress l e v e l . A constant-speed motor i s con- nected by a b e l t t o t h e d r i v e s h a f t and var ious r i g speeds a re a v a i l a b l e by changing pul leys. mal ope ra t i ng speed of 10 000 rpm. 8-diametral p i t c h spur gear w i t h a p i t c h diameter o f 8.89 cm (3.50 i n . ) and to lerances per American Gear Manufacturers Associat ion (AGMA) c lass 12.

The r i g i s capable o f d e l i v e r i n g 7 5 kW (100 hp) a t t h e nor- The standard t e s t gear i s a 28-tooth.

The standard gear m a t e r i a l used i n the a i r c r a f t i n d u s t r y today i s A I S I 9310, a h igh-a l loy s tee l . With t h e ever- increas ing t rends o f h igher loads and h ighe r temperatures, however, improved m a t e r i a l s a re des i red t o enhance a i r - c r a f t t ransmission opera t i ona l l e v e l s . The sur face f a t i g u e l i f e f o r a v a r i e t y o f proposed mater ia ls have been evaluated us ing t h e NASA Lewis f a t i g u e r i g over t h e pas t two decades ( f i g . 10). Some o f t h e m a t e r i a l s tes ted were: Super N i t r a l l o y ( r e f . 1 7 ) , A I S I H-50 ( r e f s . 1 7 and l a ) , Vasco X-2 ( r e f . 19), CBS 600 ( r e f . 19), CBS l O O O M ( r e f . 20), EX-53 ( r e f . 20), and ho t forged powder metal A I S I 4620 and 4640 ( r e f . 21). Gear sur face f a t i g u e s t r e n g t h and bending s t r e n g t h improvements by shop peening were a l s o s tud ied ( r e f . 22) . I n addi - t i o n , l u b r i c a n t and l u b r i c a n t a d d i t i v e s were found t o s i g n i f i c a n t l y a f f e c t gear sur face fa t i gue l i f e ( r e f s . 23 and 24).

I n t h e l u b r i c a t i o n and c o o l i n g o f gears, t h e gear b u l k temperature I s a c o n t r o l l i n g f a c t o r i n the gear sco r ing o r s c u f f i n g mode o f f a i l u r e . o f p e n e t r a t i o n o f t h e o i l j e t i n t o t h e gear blank p lays an impor tant r o l e i n t h e gear blank temperature. Lub r i can t o i l j e t t e s t s were performed i n t h e spur gear f a t i g u e t e s t apparatus ( f i g . 11). A s p e c i a l l y designed t e s t gear cover was made f o r v iewing t h e t e s t gears and photographing t h e l u b r i c a t i o n phenomenon. A high-speed movie camera was used t o photograph t h e o i l j e t . A high-speed a i r -cooled stroboscopic system was used t o p rov ide f l a s h tube l i g h t - i n g t h a t was synchronized w i t h t h e high-speed camera. The camera speed was s e t t o g i v e a frame f o r each t o o t h space movement. A w h i t e pigment was added t o t h e gear l u b r i c a n t and a 1000-W xenon lamp was used t o i l l u m i n a t e t h e l u b r i - cant. The exper imenta l ly measured o i l impingement depths were used t o v e r i f y a n a l y t i c a l p r e d i c t i o n s ( r e f . 25).

The depth

For f u r t h e r knowledge i n t h e l u b r i c a t i o n and c o o l i n g o f gears, gear t o o t h temperature measurements were made us ing t h e spur gear f a t i g u e t e s t apparatus. The gear surface temperatures were measured w i t h a f a s t response i n f r a r e d rad iomet r i c microscope t h a t used a l i q u i d n i t r o g e n cooled de tec to r ( f i g . 12). The microscope was capable o f measuring t r a n s i e n t temperatures up t o 20 000 Hz. Experimental measurements o f gear t o o t h average sur face temper- a tu res as a f u n c t i o n o f speed, load, and l u b r i c a n t o i l pressure were made and compared t o a n a l y t i c a l f i n i t e element methods ( r e f . 26).

The spur gear f a t i g u e t e s t apparatus i s c u r r e n t l y be ing used i n support o f t h e Navy's Hel icopter L u b r i c a t i o n Program ( r e f . 1 2 ) . Improved load -ca r ry ing capac i t y l u b r i c a n t s a r e supp l i ed by #e Navy and t h e e f f e c t o f t h e l u b r i c a n t

6

on gear fatigue life is being studied. The spur gear rig is also continuing t o test advanced gear materials (currently AIS1 M-50 Nil), advanced manufac- turing processes (currently C8N grinding), and modified tooth profiles and determining their effects on life.

Bevel Gear Apparatus

Spiral bevel gears are used extensively in helicopter transmissions to transfer power between nonparallel, intersecting shafts. gear apparatus 1s similar to the spur gear fatigue test apparatus but applied to spiral bevel gears. A torque-regenerative principle is used and torque is applied by a hydraulic loading device. The rig was designed for capabilities up to 559 kW (750 hp) at a pinion gear speed of 15 000 rpm. apparatus test gears (fig. 13) have a 35' spiral angle, a 1 In. face width, a 90' shaft angle, and a 22.5' pressure angle. The pinion has 12 teeth and the gear has 36 teeth. The rig is intended for fatigue testing, noise and vibra- tion testing, and lubrication studies. on performance is also under study.

The NASA Lewis bevel

The bevel gear

The effect of various tooth profiles

\

High Speed Gear Test Stand

For low gear speed operation, gear lubrication is often accomplished by immersion, splash, drips, or impingement techniques. At high speed operation the primary role of the lubricant is changed from preventing metal-to-metal contact to system cooling. lubrication techniques. Gear failures caused by micro-pitting or fatigue spalls could occur due to loss of oil film between teeth or inadequate oil flow. Therefore, high speed gear operation requires extended studies.

This requirement usually cannot be met by standard

The high speed gear test stand is the latest gear research rig installed at NASA Lewis (fig. 14); the test section was designed and built by Allison Gas Turbine. The objective of the rig is the study of lubrication techniques, noise, and vibration at very high spur gear pitch line velocities. The rig is basically a scaled-up version of the spur gear rig with capabilities of 2234 kW (3000 hp) at shaft speeds of 10 000 rpm, and pitch line velocities to 152.4 m/sec (30 000 ft/min). The pinion test gear has an 11-in. pitch diam- eter, a 4 diametral pitch, and a 25' pressure angle and meshes with a 13-in. pitch diameter gear. The rig has just currently been made operational and lubrication studies and gear temperature measurements are being performed.

Gear Noise Test Stand

Helicopter interior noise and vibration are of concern because of passenger

Host experts agree that the major source of cabin noise originates

comfort and the effect on pilot and crew efficiency. The standard approach in quieting the helicopter is to add cabin acoustic material which, in turn, adds weight. from the gearing in the main transmission. transmission program is emphasizing noise reduction technology (ref. 27).

Presently, the NASA helicopter

At the start of 1987, NASA Lewis initiated a transmission noise reduction program. One aspect of the program entails the fabrication of a gear noise

7

test stand. The test stand objective 1s to provide experimental verification of a noise propagation analytical code presently being developed. ical code will model a set of spur gears in contact and determine the dynamic loads and excitation forces originating from the mesh. The code will then predict the noise propagation to the surroundings using the gear excitation forces and the support structure transfer functions.

The analyt-

The conceptual design of the rig consists of a drive motor, a pair of test The drive motor and dynamometer have gears, and a dynamometer loading device.

a capability of about 130 kW (175 hp) at 6000 rpm. tested will be from the spur gear fatigue apparatus (28 teeth, 8 diametral pitch, 8.89 cm pitch diam). The test gears supporting structure and shafting is presently in the design stage. Capabilities of variable gear ratios? vari- able support stiffness and damping, and shaft misalignment are being consid- ered. It is anticipated that the rig will be operational around the beginning of 1988. The projected data to be extracted from the rig are: sound pressure levels and acoustic intensities from microphones, vibration spectra from housing-mounted accelerometers, displacements and forces at support structure mounts, and dynamic strains on gear teeth. The analytical and experimental noise data from this program will be fundamental to understanding gear noise and can be used in the future reduction of helicopter interior noise.

The initial gears to be

CONCLUDING REMARKS

This report reviewed the current experimental activities on helicopter transmission testing at NASA Lewis. The major efforts of the test stands can be classified as follows:

1. Full-scale transmission testing. Production-ready and prototype heli- copter transmissions are tested to provide analytical code verification, base- line testing from which to assess the promised advantages of future designs and concepts, and to demonstrate advanced technology.

2. Advancing sear technology. Advanced materials, lubrication schemes, and gear geometries are being studied for a variety of applicatjons t o provide analytical verification and increase present gear operational capabilities.

3. Reducing sear noise. A current emphasis on gear noise entails con- struction of a gear noise rig to provide analytical verification and increase the understanding of gear noise for a future reduction of helicopter interior no1 se.

NASA Lewis has some unique and useful facilities which are available to the rotorcraft industry for research and testing of new and advanced concepts in rotary wing flight propulsion systems. Joint programs are being conducted by NASA, the U.S. Army, and the U.S. Navy to reduce the weight and noise and increase the strength and life of helicopter transmissions and develop the drive train technology needed for the next generation rotorcraft.

REFERENCES

1. Zaretsky, E.V., Townsend, D.P. and Coy, J.J. NASA Gear Research and its Probable Effect on Rotorcraft Transmission Design. NASA TM-79292, 1979.

8

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

Zaretsky, E.V. and Its Probab TM-83389, 1983

Fischer, G.K., 1983.

Weden, 6.3. an

Coy, J.J. and Townsend, D.P. NASA Transmission Research e Effects on Helicopter Transmission Design. NASA

ed., Advanced Power Transmission Technoloqy. NASA CP-2210,

Coy, J.J. Sumnary of Drive-Train Component Technology in Helicopters. Gears and Power Transmission Systems for Hellcopters and Turboprops, AGARD CP-369, AGARD, Paris, France, 1984, pp. 2-1 to 2-17. (NASA TM-83726).

Coy, J.J., Townsend, D.P. and Zaretsky, E.V. Gearing, NASA RP-1152, 1985 (Chapter 38 in Mechanical Design and Systems Handbook, 2nd ed., H. Rothbart, ed., McGraw-Hi 11, 1985).

Coy, J.J., Townsend, D.P. and Coe, H.H. Results of NASA/Army Transmission Research. USAAVSCOM-TR-87-C-3, 1987 (to appear in a NASA CP: 1987 NASA/ARMY Rotorcraft Technology Conference).

Mitchell, A.M. and Coy, J.J. Lubricant Effects on Efficiency of a Hellcopter Transmission. Problems in Bearings and Lubrication, AGARD CP-323, AGARD, Paris, France, 1982, pp. 20-1 to 20-16. (NASA TM-82857).

Coy, J.J., Mitchell, A.M. and Hamrock, B.J. Transmission Efficiency Measurements and Correlations wlth Physical Characteristics of the Lubricant. Gears and Power Transmission Systems for Helicopters and Turboprops, AGARD CP-369, AGARD, Paris, France, 1984, pp. 20-1 to 20-15. (NASA TM 83740).

Lewicki, D.G. and Coy, 3.5. Vibration Characteristics of the OH-58A Helicopter Main Rotor Transmission. NASA TP-2705, 1987.

Braddock, C.E. and Battles, R.A. Design of an Advanced 500 HP Helicopter Transmission. Advanced Power Transmission Technology, Fischer, G.K., ed., NASA CP-2210, 1983, pp. 123-139.

Folenta, D.J. Design Study of Self-Aligning Bearingless Planetary (SABP). NASA CR-159808, 1980.

Shimski, J.T. and Paskow, L.A. Future Trends for U.S. Naval Aviation Propulsion System Lubricants. Aviation Gas Turbine Lubricants, SAE, Warrendale, PA, 1985, pp. 95-102. (SAE Paper 851835).

Mitchell, A.M., Oswald, F.B. and Schuller, F.T. Testing of YUH-61A Helicopter Transmission in NASA Lewis 2240-kW (3000 hp) Facility. NASA TP-2538, 1986.

Mitchell, A.M., Oswald, F.B. and Coe, H.H. Testing of UH-60A Helicopter Transmission in NASA Lewis 2240-kW (3000 hp) Facility. NASA TP-2626, 1986.

Oswald, F.B. Transmission. NASA TP-2698, 1987.

Gear Tooth Stress Measurements on the UH-60A Helicopter

9

16. Handschuh, R.F. and Rohn, D.A. Performance Tes t ing o f a He l i cop te r Transmission Planetary Reduction Stage. NASA TP- , 1987 ( t o be publ ished).

17. Townsend. D.P. and Zaretsky. E.V. A L i f e Study o f A I S I M-50 and Super e f . J . Lubr. Technol., N i t r a l l o y Spur Gears With and Without T i p Re1

18. Townsend, D.P., Bamberger, E.N. and Zaretsky, Ausforged, Standard Forged, and Standard Mach J . Lubr. Technol., 1976, 98, 418-425.

1974, 96, 583-590.

E.V. A L l f e Study o f ned A I S I M-50 Spur Gears.

19. Townsend, D.P. and Zaretsky, E.V. Endurance and F a i l u r e Charac te r i s t i cs o f Modi f ied VASCO X-2, CBS-600 and A I S I 9310 Spur Gears. J. Mech. Des., 1981, 103, 506-51 5.

20. Townsend, D.P. Surface Fat igue L i f e and F a i l u r e c h a r a c t e r i s t i c s o f EX-53, CBS lOOOM, and AISI 9310 Gear Mater ia ls . NASA TP-2513, 1985.

21. Townsend, D.P. Surface Fat igue L i f e and F a i l u r e Charac te r i s t i cs o f Hot Forged Powder Metal A I S I 4620, A I S I 4640, and Machined A I S I 4340 S tee l Spur Gears. NASA TM-87330, 1986.

22. Townsend, D.P. and Zaretsky, E.V. E f f e c t o f Shot Peening on Surface Fat igue L l f e o f Carburized and Hardened A I S I 9310 Spur Gears. NASA TP-2047, 1982.

23. Townsend, D.P. and Zaretsky, E.V. E f f e c t o f F i ve Lubr ican ts on L i f e o f A I S I 9310 Spur Gears. NASA TP-2419, 1985.

24. Scibbe, H.W., Townsend, D.P. and Aron, P.R. E f f e c t o f Lubr ican t Extreme-Pressure Add l t i ves on Surface Fat igue L l f e o f A I S I 9310 Spur Gears. NASA TP-2408, 1984.

25. Townsend, D.P. and Akin, L.S. Study o f Lubr ican t J e t Flow Phenomena i n Spur Gears - Out o f Mesh Condit ion. J . Mech. Des., 1978, 100, 61-68.

26. Townsend, D.P. and Akin. L.S. A n a l y t i c a l and ExDerimental SDur Gear Tooth Temperature as Af fected-by Operat ing Var iab les. . 3 . Mech. Des., 1981, 103, 21 9-226.

27. Coy, J . J . , Handschuh, R.F., Lewicki , D.G., Hu f f , R.G., Krejsa, E.A. and Karchmer, A.M. I d e n t i f i c a t i o n and Proposed Contro l o f H e l i c o p t e r Transmission Nolse a t t he Source. USAAVSCOM-TR-87-C-2, 1987 ( t o appear i n a NASA CP: 1987 NASA/ARMY Ro to rc ra f t Technology Conference).

10

,- DIFFERENTIAL

OUTPUT A

F C

9 8 . 7

>: 9 8 . 6 U

w

LL

9 8 . 5 -

9 8 . 4 -

B 9 8 . 3

350 355 360 365 370 375 CD-82- 12990 O I L INLET TEMPERATURE. K

FIGURE 2 . - OH-58A HELICOPTER MAIN ROTOR TRANSMISSION. FIGURE 3 . - OH-58A TRANSMISSION EFFICIENCY FOR VARIOUS LUBRICANTS (FROM REF. 7 ) .

11

'c 3 2

2

0 SPIRAL BEVEL MESH HARMONICS

v PLANETARY MESH HARMONICS

0 2 4 6 8 10 FREQUENCY, KHZ

FIGURE 4. - OH-58A TRANSMISSION VIBRATION SPECTRUM OF AN ACCELEROPZTER NOUNTED ON THE RING GEAR HOUSING (FROM REF. 9) .

CD-83-13657

FIGURE 5 . - 500-HP ADVANCED TECHNOLOGY TRANSMISSION.

FIGURE 6 . - 450-HP SELF-ALIGNING BEARINGLESS-PLANETARY TRANSMISSION.

12

P53GE IS QUALITY

(A) ISOMETRIC VIEW.

800-W PRIME MOVER

POWER DISTRIBUTION GEARBOX

ROTOR LOADER

TORQUER

T A I L OUTPUT SHAFT TEST TRANSMISSION

RIGHT INPUT COUPLING

LEFT F A C I L I T Y GEARBOX

CD-85-17841 RIGHT F A C I L I T Y GEARBOX

( B ) SCHEMATIC VIEW.

FIGURE 7. - NASA LEWIS 3000-HP HELICOPTER TRANSMISSION TEST STAND.

13

r SLAVE-SYSTEM

I A' O I L INLET

01 L-SEAL GAS FLOW 7

CD-85-17838

FIGURE 8. - NASA LEWIS PLANETARY GEAR TEST STAND.

PRESSURE

CD-11124-15

FIGURE 9. - NASA LEWIS GEAR FATIGUE TEST APPARATUS.

14

VAR A I S I 9310 (SHOT PEENED)

P/H A I S I 4640

P R I A I S I 4620

VAR CARPENTER EX-53

VAR CBS lo00

CVH CBS 600

CVH VASCO x-2 VIM-VAR AIS1 H-M (AUSFORGED)

VIH-VAR A I S I M-50 (FORGED)

CVM SUPER NITRALLOY

I-

VAR A I S I 9310 I I I I

0 1 2 3 4 RELATIVE L IFE (AT A 90-PERCENT

PROBABILITY OF SURVIVAL)

FIGURE 10. - RELATIVE PITTING FATIGUE LIVES OF VARIOUS AIRCRAFT QUALITY GEAR STEELS.

, rL IGHT BEAH XENON LAM-.

7‘ 22 CONDENSER LENS -,

CYLINDRICAL LENS-

-LIGHT WINDOW

I . . -. .. . - LMOVIE M R A

CD-11624-15

FIGURE 11. - THE NASA LEWIS GEAR FATIGUE TEST APPARATUS MODIFIED FOR O I L JET PENETRATION STUDIES.

, - IN SB MICROSCOPE // DETECTOR UNIT /’ AND SYNCHRONOUS

COOLING DOMODULATOR SYSTEM CIRCUITRY 7

r OPERATOR ,-PREAMP ELECTRONIC CONTROL UNIT,’

T’ \ \ \ I

TO OUTPUT \ RECORDER

OPTICAL ELEMENT

FIGURE 12. - SCHEMATIC OF INFRATRED RADIOMETRIC MICROSCOPE

FIGURE 13. - NASA LEWIS BEVEL GEAR APPARATUS TEST GEARS.

FIGURE 14. -

1 v

. NASA LEWIS HIGH SPEED GEAR TEST STAND.

16

2. Government Accession No. NASA TM-89912 AVSCOM TR-87-C-10

1. Report No.

4. Title and Subtitle

Helicopter Transmission Testing at NASA Lewis Research Center

7. Author@)

David 6. Lewicki and John 3. Coy

3. Recipient's Catalog No.

5. Report Date

6. Performing Organization Code

505-63-51 8. Performing Organization Report No.

E-3603

9. Performing Organization Name and Address

National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio 44135

2. Sponsoring Agency Name and Address

National Aeronautics and Space Administration Washington, D.C. 20546

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Memorandum 14. Sponsoring Agency Code

6. Abstract

Since 1970 the NASA Lewis Research Center and the U.S. Army Aviation Systems Command have shared an interest i n advancing the technology for helicopter pro- pulsion systems. The current experimental activities at NASA Lewis on helicopter transmission testing is reviewed. The major goals are to reduce weight and noise and to increase life and reliability. The current rigs at NASA Lewis consist o f full-scale helicopter transmisslon testing, a base effort in gearing technology, and a future effort in noise reduction technology.

r. Key Words (Suggested by Author@)) 18. Distribution Statement

Helicopters; Transmissions; Transmission testing; Gears; Lubrication; Materials

Unclassified - unlimited STAR Category 37

1. Security Classif. (of this report)

Unclassified 20. Security Ciassif. (of this page) 21. No. of pages 22. Price'

Unclas s i f i ed 17 A02