Me146 (Chap12)

Front 1

The teeth are cut in the form of a helix about the axis of rotation.

Back 1

Helical gears

Front 2

Operate on parallel axes and have teeth of opposite hand.

Back 2

Parallel helical gears

Front 3

Operates on crossed axes and may have teeth of the same or of opposite hand.

Used to transmit power between shafts which are not parallel and do not intersect.

Used to drive feed mechanism on machine tools, camshafts, oil pump on small internal combustion engines, and similar inits that require only small amounts of power.

Back 3

Crossed-helical gears

Front 4

Has straight teeth which are oblique to the direction of motion.

Back 4

Helical rack

Front 5

The contact theoreticaly extends across the entire tooth on a line parallel to the axis of rotation.

Back 5

When spur gears begin to engage

Front 6

Contact occurs only at the point of the leading edge of the tooth, gradually extending along a diagonal line across the tooth as the gears rotate.

Back 6

When helical gears begin to mesh

Front 7

Pitch line speeds of ______ to ______ are common with automobile and turbine gears and speeds of ______ have been successfully used.

Back 7

4000fpm to 7000fpm

12000fpm

Front 8

pn (circular pitch in the plane normal to the teeth)

Back 8

Normal circular pitch

Front 9

p (circular pitch in the plane of rotation or the plane perpendicular to the gear axis and reffered to as the circular pitch)

Back 9

Transverse circular pitch

Front 10

P is the transverse diametral pitch, commonly called ______.

Back 10

The pitch

Front 11

The end thrust of two helical gears having opposite helices is counterbalanced if they are mounted on the same shaft, and if both sets of teeth are cut on single gear blank.

Back 11

Double helical or herringbone gear.

Front 12

A 20deg 2/P working depth, with a whole depth varying from 2.25/P to 2.35/P is used.

Back 12

Fine pitch system.

Front 13

Helix angle of _____and_____deg are preferred for single-helical gears.

Back 13

15 and 23deg.

Front 14

Helix angle of _____and_____deg are preferred for double-helical gears.

Back 14

30 and 45deg

Front 15

Recommends two sets of basic proportions and suggest that the proportions may usually be modified so as to use the available tools.

Back 15

Dudley

Front 16

Based on the normal diametral pitch, gives helix angles from 0 to 30deg, a working depth of 2/P and whole depth of 2.25/P.

Back 16

Firtst set or One set.

Front 17

Based on the transverse diametral pitch and is recommended where quietness at high speed is important.

Back 17

Other set

Front 18

Four different helix angles for other sets.

Back 18

15deg with a woking depth of 2/P and whole depth 2.35/P.

23deg with a woking depth of 1.84/P and whole depth 2.2/P.

30deg with a woking depth of 1.74/P and whole depth 2.05/P.

45deg with a woking depth of 1.42/P and whole depth 1.7/P.

Front 19

Commonly designed to carry pitch-line loads of 100lb per inch of face per inch of diameter, and loads as high as 320lb have been successfully carried.

Back 19

High speed reduction gears for turbines.

Front 20

Designed for wear.

Back 20

Ordinary industrial gears

Front 21

Presented a very complete analysis with recommended equation for use in gear design.

Back 21

W.P Schmitter

Front 22

Used to provide for the increasing errors as the gear size increases.

Back 22

Inbuilt factor

Front 23

The maximum gear ratio advisable with helical gearing.

Back 23

10:1

Front 24

May be used for larger ratios.

Back 24

Gear train or double reduction, or a worm and worm gear.

Front 25

Ratios from 10:1 up to 100:1 are regularly employed,and ratios as high as 500:1 have been used.

Back 25

Worm and Gear sets

Front 26

A special case of helical gearing with nonparallel axes, the axes usually being at right angles.

May be cut with single or multiple thread.

Back 26

Worm and Worm gear

Front 27

Does not depend on the diameter but is found by dividing the number of teeth on the gear by the number of threads on the worm.

Back 27

Velocity ratio

Front 28

A 40 tooth gear and double thread worm havong velocity ratio of ______.

Back 28

20

Front 29

Distance from any point on one thread to the corresponding point on the next turn of the same thread, measure parallel to the axis.

The distance that a thread advances for one complete revolution of the worm.

Back 29

Lead of the worm

Front 30

The angle between the tangent to the pitch helix and the plane of rotation.

Back 30

Lead angle

Front 31

Equal to the circular pitch of the corresponding point on the adjacent thread,measured parallel to the worm axis.

Back 31

Lineal pitch

Front 32

The lineal pitch is the same as the lead.

Back 32

Single thread worm

Front 33

The picth is one-half the lead, etc.

Back 33

Double thread worm

Front 34

The _________ of the worm gear is the diameter measured on the central plane.

Back 34

Pitch diameter

Front 35

The outside diameter of the worm gear measured on the central plane.

Back 35

Throat diameter

Front 36

Pressure angle of ______deg for single and double threads, and ______deg for triple and quadruple threaded worms, tha angle in all cases being measured perpendicular to the pitch helix.

Back 36

14 1/2 deg and 20deg

Front 37

Whose diameter is not less than the outside diameter of the worm or greater than ______times the outside diameter.

Back 37

1 1/4 times

Front 38

Standard linear pitches are

Back 38

1/4 , 5/16 , 3/8 , 1/2 , 5/8 , 3/4 , 1 , 1 1/4 , 1 1/2 , 1 3/4 , 2 in.

Front 39

Worm gears ratio

Back 39

100:1

Front 40

For worms mating with gears having 24 teeth or more, the _____deg pressure angle is recommended.

Back 40

20deg

Front 41

Worms are universally made of __________, and gear is generally made of _________.

Back 41

Hardened steel and bronze.

Front 42

The number of teeth on this imaginary spur gear is called

Back 42

Virtual or equivalent number of teeth.

Front 43

These gears are approximation of hyperboloidal gears.

Back 43

Hypoid gears

Front 44

These gears are spiral bevel gears with a zero spiral angle.

Back 44

Zero Bevel gears.