Robert F. Handschuh

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

Testing of Face-Milled Spiral Bevel

Gears at High-Speed and Load

NASA/TM—2001-210743

March 2001

ARL–TR–2381

U.S. ARMY

RESEARCH LABORATORY
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NASA/TM—2001-210743

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National Aeronautics and

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Prepared for the

International Conference on Mechanical Transmissions

sponsored by the Chinese Mechanical Engineering Society

Chongqing, China, April 5–8, 2001

ARL–TR–2381

U.S. ARMY

RESEARCH LABORATORY

Robert F. Handschuh

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

Testing of Face-Milled Spiral Bevel

Gears at High-Speed and Load
Available from

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Hanover, MD 21076

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Available electronically at http://gltrs.grc.nasa.gov/GLTRS
NASA/TM—2001-210743 1

Testing of Face-Milled Spiral Bevel Gears at High-Speed and Load

Robert F. Handschuh

U.S. Army Research Laboratory

Vehicle Technology Directorate

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Abstract: Spiral bevel gears are an important drive system components of rotorcraft (helicopters) currently in use. In this

application the spiral bevel gears are required to transmit very high torque at high rotational speed. Available experimental data

on the operational characteristics for thermal and structural behavior is relatively small in comparison to that found for parallel

axis gears. An ongoing test program has been in place at NASA Glenn Research Center over the last ten years to investigate

their operational behavior at operating conditions found in aerospace applications. This paper will summarize the results of the

tests conducted on face-milled spiral bevel gears. The data from the pinion member (temperature and stress) were taken at

conditions from slow-roll to 14400 rpm and up to 537 kW (720 hp). The results have shown that operating temperature is

affected by the location of the lubricating jet with respect to the point it is injected and the operating conditions that are

imposed. Also the stress measured from slow-roll to very high rotational speed, at various torque levels, indicated little dynamic

affect over the rotational speeds tested.

Keywords: Gears, Transmissions

1 IN TRO DU C TI ON 

S piral b ev el gear s are im po rtan t com p on en ts in all cu rr ent

r otor cr aft d r iv e sy s tems . Their us e in th is ap plication is 

ess en tial sin ce they are us ed to chan ge r otation al direction 

b etween th e h or izon tal en gines and v ertical ro to r s. U sin g

them in th is ap plication ty pically r esu lts in th e g ear m es h

o peratin g at very h igh r o tation al sp eed and at h igh tor q ue

lev els. An ex am ple o f a h elicop ter m ain r oto r tr ans miss ion 

u sing s p ir al bevel g ears is s ho w n in Fig. 1 . I n this

app licatio n s piral b ev el gear s are u s ed f or tw o p ur po ses [ 1] .

The f ir s t pu r po se is to p ro vide flex ibility in en gine

p lacemen t within th e r oto rcraft. The seco nd pu rp o se is to

com bine th e two eng ine in pu ts in to a co mm on ou tp u t gear 

that in tu rn dr iv es a planetary gear mesh an d dr ives th e

m ain ro tor . This ver y flexible asp ect o f sp iral b ev el g ear s

m ak es th eir u se v er y attr active to d r iv e sy s tem d es ig ner s.

S in ce d r iv e s ys tem d es ig n er s ar e n ot restricted w ith cer tain 

s haft o r ientation s, high redu ction r atios w ith a minimu m o f

availab le vo lum e can b e accom plish ed .

The o per atio n o f dr ive s y stem s as us ed in aero sp ace

app licatio ns is q uite dif ferent fr om lo w sp eed o r 

autom otive ty pe app lication s. Th e gearing s y stem is 

p ress ur e lub r icated us in g m ultip le jets at m an y locatio n s

w ithin the g ear bo x. Th e lub rican t is remo ved f ro m the

g earb ox us in g s caven ge p u mp s to a res er vo ir . This is do n e

to minim ize g ear- lu b rican t ch ur n in g and p ro v id e the d riv e

s ys tem w ith the h ig h es t eff icien cy p o ss ib le. This imp or tan t

asp ect o f th e d rive sy stem, f or av iatio n ap p licatio ns , w ill

m in im ize the weig ht of th e lu br icant co oler s and 

ass ociated co mp on en ts.

F or aer o sp ace app licatio n s, s tr u ctur ally, th e

com po nen ts m u st b e lig ht- weig ht, h av e h ig h load cap acity ,

and b e v er y r eliable. Th e g ears ar e m ad e fr o m th e h ig hes t

q uality allo y s th at ex hib it h ig h s ur f ace har dn es s to en d ur e

the extr em e con tact lo ad s y et h ave a to ug h cor e s tr en gth 

that can tolerate th e teeth d ef lectin g du e to th e h ig h

b en ding lo ad s . Gear s in this ap p licatio n ar e car bu rized an d

f in is h g ro un d to hav e co m po nents m an u factur ed to very 

h ig h to ler an ces . All asp ects of th e g ear des ig n p ro cess ar e

imp or tan t becau se g ear s o peratin g in an aer o sp ace

env ir on m en t are p us h ed to the limits of o per atio n .

The w or k o f o th er s in ex p er im en tally meas ur ing th e

therm al perf o rm an ce an d s tr uctu r al b ehavior of g ear s has 

b een rather lim ited . This is du e to s pecial eq uip ment

n eces sar y to make th es e d if ficu lt measu remen ts . The

amo un t o f ex p er im en tal ef fo rt in thes e ar eas is d ep leted 

f ur th er wh en co ns id ering sp ir al bevel g ears . The ro ots o f

m ak in g g ear m easu rem en ts , h ow ev er, d ates back to th e

1 93 0’ s and th e wo rk co nd u cted b y Blo k [ 2, 3] . I n mo r e recen t

y ears o ther r es earch er s h av e co m pleted stud ies o n p ar allel

axis an d b ev el gear ing in vestig ating th e in f lu en ce of 

o peratio n an d o th er param eter s o n th e therm al

p er fo rm ance[ 4– 1 5] . The m eas ur ement o f the stru ctu ral

p er fo rm ance o f sp ir al bev el g ear s has m ainly b een 

inv es tig ated us in g h elico pter tr an sm iss io ns or s imu latio ns 

o f th e aer os p ace req uirem en ts . A d es criptio n o f s om e of 

the w or k available in th e o pen liter atu re is con tained in

Ref s. 1 6 -1 9.

The o bjectiv e o f th is wo r k co ntain ed in this p ap er is to 

s um marize th e exp er imental resu lts attain ed in th e NA SA 

G lenn Resear ch Center Sp iral Bev el G ear Tes t F acility .

The com p on en ts us ed in th is f acility ar e rep resen tative of 

aer os pace qu ality g ear s and lev els o f s peed an d load ar e

als o rep resen tative of th e high sp eed and lo ad co nd itio n s

that th ese co mp on en ts ar e r eq uir ed to o perate un d er . Th e

tes ting has b een do n e fo r therm al an d s tr uctur al behavio r.

Tes ts w ere r u n with an in stru men ted p in io n m em ber .

Con ditio ns o f the tests w er e ru n f ro m low to h ig h s peed 

( up to 1 44 00 rp m) an d up to 5 37 kW ( 7 20 h p) .

2 TEST FACILITY

The test facility used in the testing to be presented is

the Spiral Bevel Gear Test Facility at NASA Glenn

Research Center[13–15,19]. A sketch of the facility is
NASA/TM—2001-210743 2

shown in Fig. 2. An explanation of the operation of the

facility is better described in the cross-sectional view

showing key features in Fig. 3. The facility operates in a

closed-loop arrangement where the load is locked into

the loop via a split shaft and a thrust piston that forces a

floating helical gear into mesh. The drive motor supplies

the facility with rotation and loop losses via v-belts to the

axially stationary helical gear. The spiral bevel gears on

the test side (left side) operates where the pinion drives

the gear in the normal speed reducer mode and the slave

side (right side) of the facility acts as a speed increaser,

however the concave side of the pinion is always in

contact with the convex side of the gear on either side

Table 1 Facility operational capabilities

Maximum pinion shaft speed, RPM

Pitch line velocity, m/s (ft/min)

Pinion shaft power, kW (hp)

Test section flow rate maximum, cm3

/s (gal/min)

Oil inlet temperature (variable), o

C (oF)

Oil pressure maximum, MPa (psi)

14400

44.7 (8803)

536 (720)

51 (0.8)

38 to 189 (100 to 300)

1.38 (200)

Table 2 Basic test component design

parameters

Number of teeth pinion / gear

Module, mm (diametral pitch, 1/in.)

Mean spiral angle, deg.

Mean cone distance, mm (in.)

Face width, mm (in.)

Shaft angle, deg.

12 / 36

4.94 (5.141)

35

81.1 (3.191)

25.4 (1.0)

90.0

Table 3 Properties of lubricant used in the

test program

Kinematic viscosity, cm2/sec (cS) at:

 244 K (–20 ∞F)

 311 K (100 ∞F)

 372 K (210 ∞F)

 477 K (400 ∞F)

Flash point, K (∞F)

Fire point, K (∞F)

Pour point, K (∞F)

Specific gravity

Vapor pressure at 311 K (100 ∞F), torr

Specific heat at 311 K (100 ∞F),

 J/Kg•K, (Btu/lb•∞F)

2500¥10–2 (2500)

31.6¥10–2 (31.6)

5.5¥10–2 (5.5)

2.0¥10–2 (2.0)

508 (455)

533 (500)

219 (–65)

0.8285

0.1

2190 (0.523)

of the test facility. The load and speed of the test side

gear output shaft are monitored by an in-the-loop torque

and speed sensors. The facility was operated up to

14400 rpm and 354 N•m (3130 in.•lb) pinion speed and

torque. The facility operational capabilities and basic

gear specific-ations are shown in Tables 1 and 2,

respectively.

As mentioned earlier the test gear meshes and facility

gear systems are jet feed lubricant and gravity drained

back to the reservoir. A single jet lubricated the test and

slave side spiral bevel gears. The lubricant supply

pressure (flow) and temperature of the lubricant to the

jets was controlled during all tests. A turbine engine

lubricant was used in all tests. The properties of the

lubricant used in this study are shown in Table 3. A

Figure 1.—Main rotor transmission cross-section of the 

 U.S. Army Blackhawk helicopter.

Figure 2.—Spiral bevel test facility sketch.

Figure 3.—Cross-sectional view of facility.

Torquemeter

Drive motor

V-belt drive

pulley Thrust

piston

Helical

gears

Axial thrust

Preload

coupling Axial

motion

coupling

Spiral bevel

test section

Spiral bevel

slave section
NASA/TM—2001-210743 3

vacuum is applied the gear boxes in the facility to aid in

the draining of the lubricant out of the test and facility

gear boxes and bearing compartments.

3 TEST HARDWARE INSTRUMENTATION

The testing that will be described in this paper had the

pinion, left side (test side), instrumented for the thermal

and structural tests. In both tests, data was transferred

from the rotating instrumentation via slip rings to either a

laboratory computer or tape recorder.

3.1 Thermal Testing

The thermal testing had thermocouples imbedded in

the pinion teeth such that the meshing action did not have

direct contact with the instrumentation. In studies using

this facility[14] different approaches to trying to extract

transient temperature data from thin film sensors or

thermocouples imbedded in the meshing gear profiles of

the gear teeth were not successful. However, important

information can be extracted from the bulk temperatures

to be described in this report and show the general trends

of how the different parts of the pinion teeth thermally

operated. The general layout of the gage location is

shown in Fig. 4. The thermocouples were located at the

half-face w id th f o r th e too th to p and r oo t g ag e. Fo r the to e

and h eel ther mo cou ples th e therm oco up les w er e located at

the m id po in t b etween th e con cav e an d con vex s id es of th e

teeth an d at th e mid -too th heig h t lo catio n. A ph o to gr ap h o f

the tes t h ar d ware u s ed is s ho wn in F ig. 5 .

3.2 Structural Testing

The structural testing that was conducted in the test to

be described used strain gages in the fillet region[19]. The

locations of the strain gages as mounted on the test

Figure 4.—Thermocouple locations on test pinion. pinion are shown in Fig. 6 and a photograph of the test

Heel

Top land

Toe

Root Thermocouple

location

Figure 5.—Photograph of test pinion for thermal tests.

Figure 6.—Strain gage location on the three successive teeth along the pinion fillet.

 1

 2

 3

 4

 5

Toe

Heel

- Strain gage numbering 

3.8 mm (.15 in.)

0.38 mm (.015 in.)

Gage 

location Tooth C

Tooth B

Tooth A

18.3 mm (.72 in.)

11.2 mm (.44 in.)
NASA/TM—2001-210743 4

hardware is shown in Fig. 7. Testing using these gages

was from near static (slow roll) to high speed. Data taken

above the slow-roll conditions were time synchronous

averaged to reduce the noise from slip rings without

using low-pass filtering.

4 THERMAL TESTING RESULTS

The s pir al b evel gear mes hes in th e tes t an d s lav e side of 

the tes t r ig were lu br icated with a s in gle jet w ith a f an

s pr ay . The f an sp ray w as or iented at a distance f ro m th e

too th tip su ch th at th e w id th o f the fan was app r ox im ately 

equ al to the face w idth o f th e g ear m em bers . Tes t d ata w as 

tak en af ter s tead y s tate had been reach ed . A typ ical tim e

h is to ry of a test is s ho w n in F ig. 8 . A fter ab ou t 1 0 min o f

o peratio n, s teady s tate con ditio ns w ere r eached. Also f r om 

this data, a general tren d as s een in all d ata th at w as taken .

The too th to p w as always th e hig hest temp er atu re. This

w as f ollow ed by the to e and r oo t r eg ion s th at pr o du ced

s im ilar resu lts at a s ig n if ican tly lo wer tem peratur e

f ollo wed b y the h eel location at the gear teeth.

Thermal effects of several variables as measured will

now be presented and discussed. The first effect to be

investigated is that of applied load. As shown in

Fig. 9, the increase in load had a linear effect on the

temperature increase on all four thermocouple locations.

The next effect to be investigated was the effect of

lubricant jet pressure (or flow rate) of the lubricant to the

gear mesh. The effect of flow rate on the steady state

temperature is shown in Fig. 10. The flow rate was

varied from 24 to 49 cm3

/sec (0.38 to 0.78 gpm) with a

slight linear reduction in operating temperature over the

range of tests. This flow rate variation was achieved by

varying the lubricating jet pressure from ~0.35 to

1.42 MPa (50 to 205 psi). The last effect and a very

important aspect to be investigated was the effect of

Figure 7.—Strain gaged pinion used in experiments.

Strain 

gages

100

50

500

Elapsed time, sec

Temperature measured, °F

Figure 8.—Typical time history of a test from initiation

 of a test to steady state conditions.

0

Temperature measured, °C

50

0

150

200

250

300

350

100

150

1000 1500 2000 2500

Top

Root

Toe

Heel

Temperature measured, °F

Temperature measured, °C

325

300

275

250

225

200

175

150

150

125

100

75

350 450 550 650 750

300 400 500

Transmitted power, hp

Transmitted power, kW

Top

Root

Toe

Heel

Figure 9.—Effect of load on pinion tooth temperatures 

 at three power levels. All data taken at 38 °C (100 °F)

 oil inlet temperature and 14 400 rpm pinion shaft 

 speed.

Temperature measured, °F

Temperature measured, °C

400

350

250

300

200

200

175

150

100

.3 .4 .5 .6 .8

Lube flow rate, gpm

Lube flow rate, cm3/sec

.7

125

25 30 35 40 45 50

Tooth top

Tooth root

Tooth toe

Tooth heel

Figure 10.—Effect of lubricant flow rate on 

 temperature.

20
NASA/TM—2001-210743 5

lub rican t jet p lacem en t o n th e therm al behav io r o f th e

s piral b ev el gear m esh . The f ull load and s p eed con ditio ns 

u sed fo r this g ear m es h w er e kep t nearly co n stan t. Tw o

d if feren t lu b ricatin g jet p ress u res w er e us ed. Th e jet w as 

p laced at fiv e diff erent lo catio ns . The jet lo catio ns an d

r es ults th at were attain ed ar e s ho wn in F ig . 1 1. Lu br icating 

away fr o m th e into- m es h o r ou t- o f- mes h lo catio ns cr eated 

the h ig h es t g ear to o th temp er atu res. Fo r th e into -m es h o r

o ut-o f- m es h locatio n s th e tem per atur e r es ults wer e near ly

the s am e. Th erefo re to m ake the gear mesh as eff icien t as

p os sible, th e o ut o f m es h jet p lacem ent w ou ld be th e bes t

p os sible location to o rient the jet.

5 STRUCTURAL TESTING RESULTS

The spiral bevel gears used for structural testing had

strain gages mounted in the fillet region of the teeth. The

locations of the gages, with respect to each other, are

shown in Fig. 6. A photograph of the test hardware is

shown in Fig. 7. The data from the rotating instrumented

pinion was transferred to signal conditioners (the rest of

the bridge circuit) via a slip ring. The signals were then

output to a tape recorder for post processing. No lowpass filtering of the signals was made. The data for the

strain gage tests were taken from static (slow-roll) to

14400 rpm and from light to high load. A summary of

the test results will now be presented.

First an example of the slow-roll data is shown in

Fig. 12. As can be seen from the data, the three midface

fillet gages produced the highest positive bending stress,

however between the gages had slightly different

amplitudes (a trend seen in all data taken). The gages

across the one tooth with a heel and toe gage, had the

midface being the highest stress with the heel the next

highest and the toe position producing the lowest.

The dynamic data taken will be now discussed. The

recorded dynamic data was downloaded to a personal

computer via an analog to digital converter board and

then time synchronous averaged for 100 rotations

(typical for higher shaft speeds) of the gear shaft. An

example of the dynamic data from the three midface

fillet gages is shown in Fig. 13. As can be seen the data

taken by the three gages were fairly consistent with

Temperature measured, °F

Temperature measured, °C

175

125

123

Lubricant jet location

4

Figure 11.—Effect of lubricant jet placement on pinion 

 temperature for two different flow rates with the load 

 approximately 532 kW (714 hp). Upper symbol is for 

 24 cm3/sec (0.38 gpm) and lower symbol is for 

 49 cm3/sec (0.77 gpm).

5

225

275

325

375

75

100

125

150

175 Top

Root

Toe

Heel

2 1

5

4

3

g

Jet location

p

Figure 12.—Example of slow-roll bending stress at 885.8 N•m (7840 in.•lb) gear shaft torque.

Static roll thru time (sec)

40.3 40.4 40.5 40.6 40.7

Stress, psi –40 000

–20 000

0

20 000

40 000

60 000

80 000

100 000

120 000

Strain gage #1

Strain gage #2

Strain gage #3

Strain gage #4

Strain gage #5

0.000

0.275

0.552

0.827

Stress, GPa

–0.275
NASA/TM—2001-210743 6

respect to the relative stress differential between the

gages even though they were all located at the same midface position. The reason that this occurs is due to the

gage placement in the fillet region. Even though the

gages were only 0.38 mm (0.015 in.) active gage length,

the fillet radius of the pinion is not much larger than the

gage active length. Also, based on prior finite element

analysis of gears, the strain field varies substantially

around the fillet. Therefore the gage averages the strain

field over the gage length and the placement location.

Gage location too high on the fillet or too low will result

in a slightly different strain (stress) result. As can be seen

in Fig. 13, the three fillet gage results indicate that gage

#1 was located more toward the root than either of the

other two midface fillet gages as this gage had the largest

compressive stress (an effect that is seen by further

locating the gages in the root region), and gage #5 had

the lowest compressive strain (stress) that meant the gage

was mounted slightly higher up the fillet thus resulting in

a lower compressive and tensile components.

The last comparison to be made is the midface strain

gage output as a function of speed and applied load. The

results are shown in Fig. 14. The maximum stress value

was found from the dynamic data by scanning the time

synchronous averaged data at each of the conditions

shown. The gear shaft torque was varied approximately

from 452 N•m (4000 in.•lb) to 1186 N•m (10500 in.•lb)

at three different levels of rotational speed. As can be

seen from the data, the rotational speed of the pinion had

little effect on the bending stress that was measured.

This meant that there were minimal dynamic effects at

the conditions measured.

6 CONCLUSIONS

Based on the results attained in this study the

following basic conclusions can be made:

(1) All parameters that were varied in the thermal

studies had an effect on the steady state tooth

temperatures. Tooth temperature was the highest at

the tooth top (midface position) with the highest

temperature in excess of 188 °C (370 °F). The

temperature measured at the root and toe were similar

over all the test conditions measured and the

temperature was the lowest at the heel position.

(2) Both into-mesh and out-of-mesh lubricant jet

placement produced the lowest tooth temperatures.

However the out-of-mesh position would be the better

choice for the optimum position as the lubricant

would not need to be pumped out of the meshing zone

in that position.

(3) The stress measurements indicated that the pinion

rotational speed had a minimal effect on the

maximum stress from slow-roll to 14400 rpm.

Therefore no dynamic effect was evident over the

rotational speeds tested.

(4) The midface position produced the highest fillet

stress followed by the heel then the toe locations.

Figure 13.—Dynamic data for one rotation of the gear shaft at 1073 N•m (9500 in.•lb) torque and 

 14 400 rpm pinion shaft speed.

Time, sec

Stress, psi –40 000

–20 000

0

20 000

40 000

60 000

80 000

100 000

120 000

0.000

0.275

0.552

0.827

Stress, GPa

–0.275

0.000 0.002 0.004 0.006 0.008 0.010 0.012

Strain gage #1

Strain gage #3

Strain gage #5
NASA/TM—2001-210743 7

REFERENCES

1 Oswald, F.: Gear Tooth Stress Measurements on the UH60A Helicopter Transmission. NASA TP–2698, 1987.

2 Blok, H.: Theoretical Study of Temperature Rise at

Surface of Actual Contact Under Oiliness Lubricating

Conditions, I. Mech. E., London, Proc. Gen. Disc.

Lubrication, Vol. 2, 1937.

3 Blok, H.: Measurement of Temperature Flashes on Gear

Teeth Under Extreme Pressure Conditions, I. Mech. E.,

London, Proc. Vol. 1–2, 1937.

4 Borsoff, V.: Predicting the Scoring of Gears, Machine

Design, Vol. 37, Jan. 1965.

5 Neiman, G. and Lechner, G.: The Measurement of

Surface Temperatures on Gear Teeth, Journal of Basic

Engineering, Vol. 87, No. 3, pp. 641–654, 1965.

6 Turchina, V., Sanborn, D., and Winer, W.: Temperature

Measurements in Sliding Elastohydrodynamic Point

Contacts, Journal of Lubrication Technology, Vol. 96,

No. 3, pp. 464–471, 1974.

7 Townsend, D. and Akin, L.: Analytical and Experimental

Spur Gear Tooth Temperature as Affected by Operating

Variables, Journal of Mechanical Design, Vol. 103,

No. 1, pp. 219–226, 1981.

8 Akin, L., Mro ss, J., and Tow nsend, D.: S tudy o f Lubricant

Jet Flow Phenom ena in Spur Gears, Journ al of Lubrication

Technolog y, Vol. 97, No. 2, pp. 2 83–291 , 1975 .

9 Doi, Y. et al.: On Bulk Temperature in High-Speed and

Heavy-Duty Gears, Proceedings of the International

Symposium on Gearing and Power Transmission, JSME,

Tokyo, Japan, pp. 247–252, 1981.

10 Scoring Resistance of Bevel Gear Teeth, The Gleason

Works, Rochester, New York, 1966.

11 Coleman, W.: A Scoring Formula for Bevel and Hypoid

Gear Teeth, Journal of Lubrication Technology, Trans. of

the ASME, April 1967.

12 Ku, P., Staph, H., and Carper, H.: Gear T ooth S coring 

Inv estigation R eport USA AMRDEL –TR– 75–33, South west

Research Institute, S an Antonio, TX, Ju ly 197 5.

13 Handschuh, R.: Effect of Lubricant Jet Location on Spiral

Bevel Gear Operating Temperatures, NASA TM–105656,

AVSCOM TR–91–C–033, 1992.

14 Handschuh, R.: Thermal Behavior of Spiral Bevel Gears,

Ph.D. Dissertation, Case Western Reserve University,

August 1993.

15 Han dschuh , R. and Kicher, T .: A M ethod for Th ermal

Analysis of Spiral Bevel Gears, N ASA TM –10661 2,

ARL –TR– 457, S eptemb er 199 4.

16 Lewicki, D., Handschuh, R., Henry, Z., and Litvin, F.:

Low-Noise, High-Strength, Spiral Bevel Gears for

helicopter Transmission, Journal of Prolusion and Power,

Vol. 10, no. 3, 1994.

17 Henry, Z.: Advanced Rotorcraft Transmission Program,

1995.

18 Höh n, B.-R., Winter, H., Michaelis, K., Volhuter, F.: P itting 

Resistance and Bendin g Strength o f Bevel and Hyp oid Gear

Teeth, Proceedings of the 1 992 ASM E Internatio nal Po wer

Transmission an d Gearing Co nferen ce.

19 Handschuh, R. and Bibel, G: Comparison of

Experimental and Analytical Tooth Bending Stress of

Aerospace Spiral Bevel Gears, NASA/

TM—1999–208903, ARL-TR–1891, February 1999.

Torque, in.•lb

3000 4000 5000 6000 7000 8000 9000 10 000 11 000

40 000

50 000

60 000

70 000

80 000

90 000

100 000

110 000

120 000

Slow-roll results

Pinion speed 14400 rpm

Pinion speed 11400 rpm

452 678 904 1130

Torque (N•m)

0 .275

0 .414

0 .552

0 .690

0 .827

Figure 14.—Comparison of slow roll data to that taken at two pinion shaft speeds. Applied torque 

 was measured at the gear shaft.

Maximum stress, psi

Maximum stress, GPa
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Robert F. Handschuh

Testing of Face-Milled Spiral Bevel Gears at High-Speed and Load

Spiral bevel gears are an important drive system components of rotorcraft (helicopters) currently in use. In this application the spiral bevel gears are required to transmit very high torque at high rotational speed. Available experimental data

on the operational characteristics for thermal and structural behavior is relatively small in comparison to that found for

parallel axis gears. An ongoing test program has been in place at NASA Glenn Research Center over the last ten years to

investigate their operational behavior at operating conditions found in aerospace applications. This paper will summarize

the results of the tests conducted on face-milled spiral bevel gears. The data from the pinion member (temperature and

stress) were taken at conditions from slow-roll to 14400 rpm and up to 537 kW (720 hp). The results have shown that

operating temperature is affected by the location of the lubricating jet with respect to the point it is injected and the

operating conditions that are imposed. Also the stress measured from slow-roll to very high rotational speed, at various

torque levels, indicated little dynamic affect over the rotational speeds tested.