NASA/TM--1999-209188

U,S, ARMY

RESEARCH LABORATORY

Evaluation of Carburized and

Ground Face Gears

ARL-TR-1998

David G. Lewicki and Robert E Handschuh

U.S. Army Research Laboratory, Glenn Research Center, Cleveland, Ohio

Gregory F. Heath and Vijay Sheth

The Boeing Company, Mesa, Arizona

Prepared for the

55th Annual Forum

sponsored by the American Helicopter Society

Montreal, Quebec, Canada, May 25-27, 1999

National Aeronautics and

Space Administration

Glenn Research Center

May 1999
Acknowledgments

The authors wish to thank Dr. William J. Scheuren of the Defense Advanced Research Projects Agency for his valuable

contribution to the Technology Reinvestment Program "Development of Face Gear Technology

for Industrial and Aerospace Power Transmission".

NASA Center for Aerospace Information

7121 Standard Drive

Hanover, MD 21076

Price Code: A03

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National Technical Information Service

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Price Code: A03
Evaluation of Carburized and Ground Face Gears

David G. Lewicki and Robert F. Handschuh

U.S. Army Research Laboratory

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Obio

Gregory F. Heath and Vijay Sheth

The Boeing Company

Mesa, Arizona

Abstract

Experimental durability tests were performed on

carburized and ground AIS1 9310 steel face gears. The

tests were in support of a Defi_nse Advanced Research

Projects Agency (DARPA) Technology Reinvestment

Program (TRP) to enhance face-gear technology. The

tests were conducted in the NASA Glenn spiral-bevelgear/lace-gear test facility. Tests were run at 2300 rpm

lace gear speed and at loads of 64, 76, 88, 100, and

l l2-percent of the design torque of 377 N-m

(3340 in-lb). The carburized and ground face gears

demonstrated the required durability when run for tenmillion cycles at each of the applied loads. Proper

installation was critical for the successful operation of

the spur pinions and face gears. A large amount of

backlash produced tooth contact patterns that

approached the inner-diameter edge of the face-gear

tooth. Low backlash produced tooth contact patterns

that approached the outer-diameter edge of the facegear tooth. Measured backlashes in the range of

0.178 to 0.254 mm (0.007 to 0.010 in) produced

acceptable tooth contact patterns.

Introduction

Designers are constantly searching for ways to reduce

rotorcraft drive system weight. Reduced weight can

increase payload, performance, or power density of

current and future systems. One example of helicopter

transmission weight reduction was initiated as part of

the United States Army Advanced Rotorcrafl

Transmission program. This example used a splittorque, face-gear configuration concept [ I ]. Compared

to a conventional design with spiral-bevel gears, the

split-torque, [hce-gear design showed substantial

weight savings benefits. Also, the use of face gears

allows a wide range of possible configurations with

technical and economic benefits 12].

Historically, face gears have been used to transfer

light loads or angular motion between intersecting

shafts (usually at right angles) such as in positioning

mechanisms. Standards [31 as well as examples of

research contributions [4] exist for this type of

application. There is, however, a lack of experience

with respect to design guidelines, stress allowables,

and manufacturing capabilities for face-gear use in

high-speed, high-load, applications such as helicopter

rotor drive systems. Recent studies have been

performed to advance the analytical capabilities

relating to face-gear design [5-8]. These studies

considered face-gear geometry, size limitation

factors, tooth contact analysis, kinematics, and

transmission error analysis. Experimental testing has

also been performed to demonstrate feasibility and

investigate failure modes of shaper-cut face gears

[9-10]. These studies identified the need for face

gears made from high-strength, carburized steels in

order to obtain the required durability when subjected

to a high-speed, high-load environment. When using

carburized steels, there is a requirement to grind the

gears to compensate for heat treatment distortion in

order to obtain high-accuracy tooth geometry.

However, there is currently no machine available that

will grind face gears.

A new initiative has begun in Europe to investigate

and advance the use of face gears in aerospace

transmissions [1 I]. In the United States, a Defense

Advanced Research Projects Agency (DARPA)

Technology Reinvestment Program (TRP) was

established to further enhance face-gear technology.

The objective of the DARPA program is to develop a

grinding procedure for thce gears as well as design

and demonstrate the proof-of-concept of a

concentrically-arranged split-torque, face-gear

transmission configuration [121. A grinding

Copyright © 1999 by the American Helicopter Society, Inc. All rights reserved.

NASA/TM-- 1999-209188 I
procedurewasdevelopedbasedon a continuous

grindingmethodusinga wormgrindingwheel.

PrototypecarburizedandgroundAISI9310steelface

gearswerefabricatedaspartofthisprogram.

The objectiveof this work is to describethe

preliminaryresultsof the experimentaltests

perlbrmedonthecarburizedandgroundAISI9310

steelfacegears.FacegearsweretestedintheNASA

Glennspiral-bevel-gear/face-gear facility.Basicfacegeardesign,testfacility,setupprocedures, testing

procedures, andtestresultsaredescribed.

Face Gear Applications in Helicopter

Transmissions

Figure I shows the split-torque, face-gear

transmission developed during the U.S. Army

Advanced Rotorcraft Transmission (ART)

program [1]. For this configuration, an involute spur

Face gears

Figure 1. Split-torque, face-gear transmission from ART

program [1].

gear drives both an upper face gear and lower face

gear. These face gears are connected to spur gears

which drive a large bull gear. By splitting the power

flow in these two paths, smaller components can be

utilized which leads to reduced weight. Compared to

spiral-bevel gears, face gears allow the use of a

simpler, less expensive, involute spur pinion. In

addition, the pinions do not produce axial tbrces and

have less axial misalignment restrictions than spiralbevel gears. It was estimated that a 40-percent

weight reduction resulted from the split-torque, facegear design compared to a conventional design. The

conventional design weight used for comparison

above was based on a parametric upscale of

transmission design technology existing at that time.

A design configuration which can be installed in

existing aircraft much more readily than the

preceding ART design is shown in Figure 2. This is

Idler spur gear i

V

Input spur gear

(quantity 2)

(quantity 2) Face gears (upper & lower)

Figure 2. Split-torque, face-gear transmission from TRP

program [12].

a concentric, split-torque, face-gear design developed

during the DARPA Technology Reinvestment

Program [t2]. This reduced-scale test gearbox will

be used in proof-of-concept test evaluations. For this

concept, an involute spur gear also drives a pair of

face gears and the power flow is split in two. For the

upper lace gear, the power flow is direct from the

input spur gear to the face gear. For the lower face

gear, however, the power flow is from the input spur

gear through the lower face gear, to an idler spur

gear, and then the upper face gear. This configuration

allows a large power capacity in a relatively small

package. Assuming a full size production design,

this concept has an estimated weight savings of

25-percent compared to a modern technology

conventional design. These two examples show the

potential benefits for the use of face gears in

helicopter transmissions.

Test Facility

The experiments reported in this report were tested in

the NASA Glenn spiral-bevel-gear/face-gear test

facility. An overview sketch of the facility is shown

in Figure 3a and a schematic of the power loop in

shown in Figure 3b. The facility operates in a closedloop arrangement. A spur pinion drives a face gear in

the test (left) section. The face gear drives a set of

helical gears, which in turn, drive a face gear and

spur pinion in the slave (right) section. The pinions

NASAJTM-- 1999-209188 2
a) Overview of facility.

Helical

Drive

motor

pulley

piston

Torquemete

Face gear Face gear

test section slave section

b) Schematic view.

Figure 3. NASA Glenn spiral-bevel-gear / face-gear

test facility.

of the slave and test sections are connected by a cross

shaft, thereby closing the loop. Torque is supplied in

the loop by a thrust piston which exerts an axial three

on one of the helical gears. A 75-kW (100-hp) DC

drive motor, connected to the loop by V-belts and

pulleys, controls the speed as well as provides power

to overcome friction. The facility has the capability

to operate at 560 kW (750 hp) and 20,000 rpm pinion

speed. A torquemeter in the loop measures torque

and speed. The facility is also equipped with

thermocouples, oil flow meters, pressure transducers,

and accelerometers.

The gears and bearings of the facility are lubricated

and cooled by a pressurized oil system. The

lubricating fluid used was a synthetic base helicopter

transmission oil conforming to the DOD-L-85734

specification. The test pinions and face gears were

lubricated by jets which radially directed oil into the

roots of the teeth on both the into-mesh and out-ofmesh sides. The nominal oil supply pressure was

552 KPa (80 psi) and the nominal flow rate was

2.6 I/rain (0.7 gpm) for both the test section and slave

section. Oil inlet temperature was se{ at 74 °C

(165 °F). In addition, the oil system was equipped

with a chip detector as well as a three-micron filter.

Face Gear Grinding Setup

The face gears used in the current tests were

precision ground using a true generating method.

The goal was to produce face gears having a quality

of American Gear Manufacturers Association

(AGMA) Class 12 or better. The method used

employed a worm thread grinding wheel to generate

, Dressing. .

Pinion,,;/';" jtool _i' _'/

Figure 4. Face-gear gdnding setup.

the face gear teeth in a setup similar to that shown in

Figure 4. The worm wheel rotational axis was

located perpendicular to the lace gear axis at an offset

distance. During grinding, the worm rotated about its

axis as it translated across the face gear teeth along a

nearly radial line. The translation was at a small

angle to the true radial line and related to the lead

angle of the worm. The face gear work piece also

rotated slowly during grinding so that all teeth were

generated synchronously after multiple turns of the

face gear as the grinding worm slowly translated

inward. An effective method of redressing the

grinding wheel (without tooth undercutting) during

the above process was also developed.

The lace gears were ground on a four-axis machine

incorporating the basic setup described above. The

first development gears experienced grinding burns as

process parameters were being adjusted. Other

difficulties included tooth facets and rough surface

finishes. Eventually, face gears of AGMA Class I1

quality were made tbr the tests. The experience with

the setup used validated the process but indicated that

a better machine is required to obtain the gear quality

needed. Deficiencies encountered included limited

machine grinding speed, excessive machine

deflections, and control-loop errors inherent in older

vintage machines. The machine capability for making

larger lace gears (desired for aerospace use) was

limited as well. Current work is underway to develop

a full CNC five-axis grinding machine for lace gears.

NAS A/TM-- 1999-209188 3
Test Gears

The design parameters for the pinions and face gears

used in the tests are given in Table I. A photograph

of the test specimens is shown in Figure 5. This set

was a hybrid between the ART program design and

the TRP design. The set had a module of 2.54 mm

(diametral pitch of 10 teeth/in) and a reduction ratio

of 4.059:1. The face width of the face gears was

15.7 mm (0.620 in). The face width of the spur

pinions was 32.6 mm (1.285 in). The shaft angle was

90 deg to accommodate the facility. The pinions

were made from carburized and ground AISI 9310

steel using standard aerospace practices. The face

gears were made from the same material and

manufactured using the grinding procedure

previously mentioned.

Table 1. Test Gear Design Data

AGMA quality; desired, achieved ................. 12, 11

Number of teeth; pinion, face gear ............... 17, 69

Module (mm) ................................................ 2.54

Pressure angle (deg) ................................... 27.5

Shaft angle (deg) ......................................... 90

Face width (mm); pinion, face gear .............. 32.6, 15.7

Hardness (Re); pinion and face gear ............ 58-62

RMS surface finish (lam) .............................. 0.4

AGMA pinion bending stress (MPa); index,

allowable ...................................................... 210, 450

AGMA contact stress (MPa); index,

allowable ...................................................... 1170, 1380

Material ................ Carburized and _round AlSl 9310 steel

Figure 5. Test spur pinion and face gear.

Hertz theory. The calculated pinion bending stress at

377 N-m torque was 210 MPa (30 ksi) based on

standard AGMA calculations and using an effective

lace-gear face width. The allowables stated in the

table are those commonly accepted for AISI 9310

carburized and ground spur gears.

Due to the manufacturing problems previously

mentioned, the face gears actually produced by the

grinding procedure described abovc were not up to

aerospace quality standards. The teeth had a

Poor surface finish

Facets

Figure 6. Development problems with initial ground

face gear.

relatively poor surface finish as well as faceted areas

(Figure 6). In order to improve the surface finish, the

teeth were subjected to a super-finish process [13].

In this process, the gears were immersed in a

container of small zinc chips, water, and aluminum

oxide powder. The container was vibrated for a

number of hours and the grade of oxide powder was

increased in fineness in several stages. Figure 7

shows a face gear after such a process. Although

The 100-percent design torque for the face gears was

defined as 377 N-m (3340 in-lb). This produced the

same magnitude of contact stress as the face gears of

the TRP concentric, split-torque transmission

configuration at it's 100-percent design load [12].

For the test gears, the calculated contact stress at

377 N-m torque was 1170 MPa (170 ksi) based on

Figure 7. Super-finished face gear.

actual surface roughness measurements for the face

gears tested were not available at the time, it was

reported in [13] that a Ibur to six-times improvement

in surface finish was achieved on those specific gears

studied.

NASA/TM-- 1999-209188 4
Test Gear Installation Procedures

Although not as stringent as for spiral-bevel gears,

proper pinion and face gear installation is crucial for

successful operation. The installation procedure for

the gears tested was as follows. First, the test-side

pinion and lace gear were installed in the facility

(with no cross shaft connected to the pinion). The

pinion was locked to ground and backlash

measurements were taken for the mesh. A dial

indicator was installed at the center of the face gear

tooth, the lace gear was manually rotated back and

forth, and the backlash was recorded. After

completion, marking compound was applied to the

pinion and face gear teeth. No-load contact pattern

checks were performed by manually rotating the

pinion/face-gear assembly. If necessary, the shim

located behind the face gear, which moves the face

gear in the axial direction, was adjusted to achieve

the proper backlash and contact pattern. This process

was then repeated for the slave-side pinion/face-gear

mesh. After proper shimming was achieved, the

cross shaft was installed. Marking compound was

then re-applied to all the pinions and gears and a

loaded static roll test was performed. This was done

by applying a moderate torque in the loop, manually

rotating the complete assembly, and photographing

the contact patterns. Figure 8 shows a typical

example of a tooth contact pattern check for a loaded

static roll test. Again, the objective of this procedure

a) Pinion.

b) Face gear.

Figure 8. Typical tooth contact pattern checks from

loaded static roll tests during installation.

was to ensure the proper shimming to produce a tooth

contact pattern that was centered on the pinion and

face-gear teeth in order to avoid edge loading.

At the start of the project, it was unclear as to the

proper value of shim that would produce the required

backlash and contact pattern. To gain experience, a

study was conducted to determine the effect of

shimming on backlash and contact pattern. Herc,

various shims were installed while backlash and

pattern checks were measured for the test and slave

sections using the procedure described above.

Figure9 documents the effect of shimming on

backlash. It should be noted that there was some

0.25

0.20

E

E. 0.15

-_ 0.10

o

0.05

0.00

2.5

0.25

0.20

E

E. 0.15

t'-

t_

"_ 0.10

o

t_

0.05

0

0 0

a) Test side

I I

2.6 2.7 2.8

Face gear shim, mm

b) Slave _ide mesh. I q

0.00

2.5 2.6 2.7 2.8

Face gear shim, mm

Figure 9. Effect of face-gear shimming on tooth

backlash.

I

2.9

I

2.9

variability in the backlash measurement. Overall,

there appeared to be a linear relationship between

shimming and backlash for the selected range

presented. Figure 10 shows the effect of backlash on

tooth contact pattern. The results depicted are for the

test side, but a similar trend resulted for the slave side

also. Note that the figure contains hand-drawn

sketches of the contact pattern. The purpose is not to

quantitatively define the required magnitude of

backlash, but to show an important trend in the

installation process. If the backlash is too loose

(higher number), the tooth contact approaches the

inner-diameter edge of the face gear, possibly leading

to edge contact. If the backlash is too tight (lower

NASA/TM-- 1999-209188 5
Face-gear Face-gear

Test No. speed (rpm) torque (N-m)

1 2300 242 (64%)

2 2300 287 (76%)

3 2300 332 (88%)

4 2300 377(100%)

s 2300 424(t12%I

Table 2. Test operating conditions.

Test section Slave section

Pinion, Face-gear, Pinion Face-gear Pinion Face-gear

million cycs million cycs S/N S/N S/N S/N

40.6 10.0 L5-12 2-2 L5-5 2-4

40.6 10.0 L5-12 2-2 L5-5 2-4

40.6 10.0 L5-12 2-2 L5-5 2-4

40.6 10.0 L5-11 2-2 L5-9 2-4

40.6 10.0 1 2-2 2 2-4

number), the tooth contact approaches the outerdiameter edge of the face gear, again possibly leading

to edge contact. In addition, the clearance between

the pinion and lace gear could be critically reduced

when the gears reach operating temperature if the

backlash is too tight. This could result in jamming,

coast-side contact, or scoring failure. From the

experience of the tests performed, backlash in the

range of 0.178 to 0.254 mm (0.007 to 0.010 in)

produced acceptable tooth contact patterns.

O.076-mm

backlash _

toe---_ _ heel

-- "_""" tip

O.140-ram _

backlash

Contact

_-pattem

0.196-mm __--_

backlash

Figure 10. Effect of face-gear shimming and backlash

on tooth contact pattern (test side face gear).

Test Procedure

A total of five endurance tests are reported in this

work. The test operating conditions are listed in

Table 2. The objective of the tests was to

demonstrate that carburized and ground face gears

would achieve the required durability when subjected

to high-load helicopter transmission conditions. At

the start of the project, extensive modal surveys of

the test facility were conducted as well as speed

sweeps with the test hardware installed. From these

studies, a lace gear speed of 2300 rpm was selected

as the test condition to avoid any speeds that could

contain facility-resonant dynamic loads. Test gear

loads of 64, 76, 88, 100. and l l2-percent design

torque were run Ibr ten-million lace-gear cycles each.

The same test-side face gear was used for all of the

runs (serial number (S/N) 2-2). Similarly, the same

slave-side face gear was used (S/N 2-4). These were

carburized, ground, and super-finished face gears.

Since the pinions accumulated over four times the

number of cycles as the face gears, the pinions were

replaced after each higher load condition to minimize

the chance of a pinion failure causing face-gear tooth

distress. Based on this, the pinions for both the test

and slave sides were replaced after the 88 and

100-percent load tests. The original pinions

(S/N's L5-12 and L5-5) were carburized, ground, and

super-finished, while the subsequent ones used were

only carburized and ground.

At the start of each test, the gears were installed as

discussed in the previous section. They were then

run for a break-in period which consisted of a gradual

increase in speed and torque. After the break-in, the

gears were visually inspected then run per the

specified test condition. Facility parameters such as

speed, torque, oil flow, oil pressure, temperatures,

and vibration were monitored throughout the test.

After completion of ten-million face-gear cycles, the

gears were removed from the rig, inspected (visual

and magnetic particle), and photographed.

Results and Discussion

Figure 11 shows typical vibration spectrums from the

tests. The spectrums were produced from highfrequency piezoelectric accelerometers mounted on top

of the pinion housings near the pinion/face-gear meshes.

One was mounted on the test side and one on the slave

side. The accelerometers had integral electronics, a

typical sensitivity of 10 mV/g, and a resonancc

frequency of 90 kHz. From the spectrum, the major

sources of vibration were fi'om the pinion/face-gear

fundamental meshing and harmonic frequencies.

Figure 12 gives the maximum vibration as a function

of run time for all the tests. The maximum vibration

is defined as the maximum value of the spectrum,

and usually occurred at the pinion/face-gear

fundamental meshing frequency. Note that the

vibration was rather sporadic during the tests. This is

NASA/TM-- 1999-209188 6
5 - a) Test side mesh.

o_ 4 -

E

3 -

El0

c" •

o 2 - I •

1 -

0 _ _ • t

5 b) Slavesidemesh.

4 •

E

-_ 3

Cb

c"

o 2

> I •

0 5 10 15 20

Frequency, kHz

Figure 11. Vibration spectrum at 10-million face-gear

cycles at 424 N-m torque and 2300 rpm (triangles

denote pinion/face-gear meshing and harmonic

frequencies).

not uncommon for vibration of high-speed

machinery. Also, there appeared to be no definite

trend of vibration with torque. This is consistent with

previous studies performed on helicopter

transmissions I14, 151. From Figure 12b, a

significant reduction in vibration for the slave side

occurred at 20 million cycles. This was probably due

to the replacement of a failed pinion shaft support

bearing at the end of test 2. Also, significant changes

in vibration occurred at 30 and 40 million cycles for

both the test and slave sides (Figures 12a and 12b).

This was probably due to installation of replacement

pinions tbr tests 4 and 5.

At the end of tests 1 and 2 (242 N-m, 64-percent

design torque, and 287 N-m, 76-percent design

torque, respectively), there was no noticeable wear on

any of the spur pinions or face gears. At the end of

test 3 (332 N-m, 88-percent), the pinions had very

light wear but the face gears exhibited no noticeable

wear. The pinion teeth on the slave side had wear

lines where the pinion meshed with the face-gear

outer-diameter region. This was possibly caused by

debris from the pinion shaft support bearing failure.

At the end of test 4 (377 N-m, 100-percent), the

replacement pinions had a slight increase in the

amount of wear compared to the pinions from test 3.

Concentrated wear on the pinion teeth was noticed as

diagonal lines on the teeth corresponding to the

location of the pitch line. The face gears, however,

10

8

-_ 6

CO

o 4

t_

2

>

0

10

_= 8

-_ 6

C_

=-

._o 4

..Q

N 2

0

450

400 E

35o

300

0

_- 250

2O0

0

a) Test side mesh.

v Lh,-

I I I I I

I I I I ,!

c) Face-gear torque. _I_

I I I I I

10 20 30 40 50

Run time, face-gear million cycles

Figure 12. Maximum vibration of spectrum as a

function of run time.

had less noticeable wear than the pinions. Slight wear

lines were noticed that appeared to correspond with

the edges of the facets on the teeth.

At the end of test 5 (424 N-m, l l2-percent), the

replacement pinions had again, a slight increase in

the amount of wear compared to the pinions from

test 4. This was expected due to the increased

applied load. Slight wear lines were apparent near

the pitch line as well as edge lines where the pinion

meshed with the face-gear inner-diameter and outerdiameter regions. The marks corresponding to the

face gear outer-diameter region were attributed to a

few burrs on the face-gear outer-diameter edge,

probably caused during hardware assembly, Slighl

scratching appeared at the tooth tips. Overall,

however, relatively little wear was noticed. The face

gears had even less noticeable wear than the pinions.

As stated before, slight wear lines were noticed that

appeared to correspond with the edge of the facets on

the teeth. At this time, the effect of the facets on

durability and performance are not known. Also.

minor scratching was exhibited on the face gears near

the outer-diameter tip region. Figure 13 depicts the

wear after test 5. Aside f'rom minor wear line

situations, the pinions and, especially the lace gears.

had no significant wear problems or failure modes.

(Note that the wear of the pinions in Figure 13 is just

the removal of the black-oxide.) Thus, from the tests,

NASA/TM-- 1999-209188 7
the carburized and ground face gears demonstrated

the required durability when subjected up to

112-pcrcent design torque. Further tests are planned

to increase the applied torque and determine the load

capacity of the face gears.

a) Pinion, test side.

b) Face gear, test side.

c) Pinion, slave side.

d) Face gear, slave side.

Figure 1:3. Pinion and face gear teeth after test 5

(424 N-m, 112-percent design torque).

Conclusions

Experimental durability tests were performed on

carburized and ground AISI 9310 steel lace gears.

The tests were conducted in the NASA Glenn spiralbevel-gear/face-gear test facility. Tests were run at

2300 rpm face gear speed and at loads of 64, 76, 88,

100, and l l2-percent of the design torque of

377 N-m (3340 in-lb) at ten-million face-gear cycles

each. The following conclusions were made:

I) Carburized and ground face gears demonstrated

the required durability when run for ten-million

cycles at loads of 64, 76, 88, 100, and

112-percent of the design torque. Other than

wear lines caused by isolated situations, the spur

pinions and face gears had no significant wear

problems or failure modes.

2) Proper installation was critical for the successful

operation of the spur pinions and face gears.

Backlash too high produced tooth contact

patterns that approached the inner-diameter edge

of the face-gear tooth. Backlash that was too

low produced tooth contact patterns that

approached the outer-diameter edge of the facegear tooth. Measured backlashes in the range of

0.178 to 0.254 mm (0.007 to 0.010 in) produced

acceptable tooth contact patterns.

3) From spectrum readings taken during the tests,

the major source of vibration was from the

pinion/face-gear fundamental meshing frequency

and harmonics. Also, there was no definite trend

of vibration with torque.

References

Heath, G.F., and Bossler, R.B., "Advanced

Rotorcrafl Transmission (ART) Program - Final

Report", NASA CR-191057, Army Research

Laboratory ARL-CR- 14, January 1993.

. Grendal, H.F., "Cylkro Gears: An Alternative in

Mechanical Power Transmission", Gear

Technology, Vol. 13, (3), May-June 1996,

pp. 26-31.

. AGMA, "Fine-Pitch On-Center Face Gears for

20-Degree Involute Spur Pinions", AGMA

203.03, April 1973.

NASA/TM-- 1999-209188 8
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May 1999

4. TITLE AND SUBTITLE

Evaluation of Carburized and Ground Face Gears

6. AUTHOR(S)

Technical Memorandum

5. FUNDING NUMBERS

WU-581-30--13-00

ILI62211A47A

David G. Lewicki, Robert F. Handschuh, Gregory F. Heath, and Vijay Sheth

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Glenn Research Center

Cleveland, Ohio 44135-3191

and

U.S. Army Research Laboratory

Cleveland. Ohio 44135-3191

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

and

U.S. Army Research Laboratory

Adelphi. Maryland 20783-1145

8. PERFORMING ORGANIZATION

REPORT NUMBER

E- I 1700

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TM-- 1999-209188

ARL-TR- 1998

11. SUPPLEMENTARY NOTES

Prepared for the 55th Annual Forum sponsored by the American Helicopter Society, Montreal, Quebec, Canada,

May 25-27, 1999. David G. Lewicki and Robert F. Handschuh, U.S. Army Research Laboratory, NASA Glenn Research

Center; Gregory F. Heath and Vijay Sheth, The Boeing Company, Mesa, Arizona. Responsible person, David G. Lewicki,

organization code 5950, (216) 433-3970.

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category: 37 Distribution: Nonstandard

This publication is available from the NASA Center for AeroSpace Information, (301) 621-0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

Experimental durability tests were performed on carburized and ground AISI 9310 steel face gears. The tests were in

support of a Defense Advanced Research Projects Agency (DARPA) Technology Reinvestment Program (TRP) to

enhance lace-gear technology. The tests were conducted in the NASA Glenn spiral-bevel-gear/face-gear test facility.

Tests were run at 2300 rpm face gear speed and at loads of 64, 76, 88, 100, and ! 12-percent of the design torque of 377

N-m (3340 in-lb). The carburized and ground lace gears demonstrated the required durability when run for ten-million

cycles at each of the applied loads. Proper installation was critical for the successful operation of the spur pinions and

face gears. A large amount of backlash produced tooth contact patterns that approached the inner-diameter edge of the

face-gear tooth. Low backlash produced tooth contact patterns that approached the outer-diameter edge of the lace-gear

tooth. Measured backlashes in the range of 0.178 to 0.254 mm (0.007 to 0.010 in) produced acceptable tooth contact

patterns.

14. SUBJECT TERMS

Gears; Transmissions (machine elements); Durability; Face-gears

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

NSN 7540-01-280-5500

18. SECURITY CLASSIFICATION

OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION

OF ABSTRACT

Unclassified

15. NUMBER OF PAGES

15

16. PRICE CODE

A03

20. LIMITATION OF ABSTRACT

Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std, Z39-18

298-102
4. Chakraborty, J., and Bhadoria, B.S., "Surface

Durability Ratings for On-Center and Off-Center

Spur Face Gears", ASME 75-PTG-4, Joint

ASLE-ASME Lubrication Conference, Miami

Beach, FL, October 1975.

5. Litvin, F.L., et al., "Design and Geometry of

Face-Gear Drives", ASME Journal of

Mechanical Design, Vol. 114, (4), December

1992, pp. 642-647.

. Litvin, F.L., et al., "Application of Face-Gear

Drives in Helicopter Transmissions", ASME

Journal of Mechanical Design, Vol. 116, (3),

September 1994, pp. 672-676.

7. Toma, C., and Play, D., "Design of Face Gears:

Manufacturing Simulation and Mechanical

Behaviour", 7th International Power

Transmission and Gearing Conference,

San Diego, CA, October 1996, pp. 687-692.

8. Zhang, Y., and Wu, Z., "Offset Face Gear

Drives: Tooth Geometry and Contact Analysis",

ASME Journal of Mechanical Design, Vol. 119,

( I ), September 1997, pp. 114-119.

9. Handschuh, R.F., Lewicki, D.G., and Bossier,

R., "Experimental Testing of Prototype Face

Gears for Helicopter Transmissions", Journal of

Aerospace Engineering, Proceedings of the

Institute of Mechanical Engineers, Vol. 208,

(G2), October 1994, pp. 129-135.

10. Handschuh, R.F., Lewicki. D.G., Heath, G.F.,

and Bossler, R.B., "Experimental Evaluation of

Face Gears for Aerospace Drive System

Applications", 7th International Power

Transmission and Gearing Conference,

San Diego, CA, October 1996, pp. 581-588.

11.

12.

13.

14.

15.

Caruso, A., et al., "The Brite-Euram FACET

Programme on Face Gears in Aerospace

Transmissions", Aerospace Transmission

Technology Into the 21 st Century,

Cascina Costa, Italy, October 1998.

Chen, D., and Bossier, R.B., "Design, Analysis,

and Testing Methods tbr a Split-Torque FaceGear Transmission", 31st AIAA/SAE/ASME

Joint Propulsion Conference, San Diego, CA,

July 1995.

Snidle, R.W.. Evans, H.P., and Alanou, M.P.,

"The Effect of Superfinishing on Gear Tooth

Profile lFinal Reportl", Army Research

Development and Standardization Group Report

AD-A327916, June 1997.

Lewicki, D.G., and Coy, J.J., "Vibration

Characteristics of OH-58A Helicopter Main

Rotor Transmission", NASA TP-2705,

AVSCOM TR-86-C-42, April 1987.

Lewicki, D.G., Handschuh, R.F., Henry, Z.S.,

and Litvin, F.L., "Low-Noise, High-Strength,

Spiral-Bevel Gears for Helicopter

Transmissions", AIAA Journal of Propulsion and

Power, Vol. 10, (3), May-June 1994,

pp. 356-36 I.

NASA/TM--1999-209188 9