Design of gearbox. Design of transmission elements(DoTE)

1. Design of Multi-speed Gearbox
Dr P.NALLASAMY
MECH-PSGTECH

3. Types of Gearbox
(1) Sliding mesh gear box:
• When we talk about types of gearbox, this is one of the
oldest type. It this, gears on the main shaft are moved
right or left for meshing them with appropriate gears on
the counter shaft for obtaining different speed.
• This type of gear box derives its name from the fact that
the gears are meshed by sliding. One disadvantage of it
is that, special skill is required to operate this gear box
and there are high chances of wear and tear of gearbox.

4. Run Video

5. Lathe Gearbox

6. Machine
Tool
Gearbox

7. (2) Constant mesh gear box:
• This is one of the famous type used in twenty century. It this
gearbox, all the gears are in constant mesh with each other all the
time. The gears on the main shaft rotates freely without rotating
the main shaft.
• Constant mesh gear box consists two dog clutches. These clutches
are provided on the main shaft, one between the clutch gear and
the second gear and the other between the first gear and reverse
gear. When the left side dog clutch is made to slide left by means
of gearshift lever, it meshes with the clutch gear and the vehicle
runs on top speed.
• If this clutch slide right and mesh with second gear, then the
vehicle runs on second gear speed. So in constant mesh gear box
we can change the gear ratio by shifting the dog clutch. This type
of gear box is more popular than sliding mesh because it creates
low noise and less wear of gears.

8. Run Video

11. (3) Synchromesh gear box:
• One big problem occur in constant mesh gear
box is that when the driver engage the dog
clutch, the main shaft and gear to be meshed
running at different speed.
• So when engage this gear cause wear and tear
of dog clutch. This problem is solved by a
synchromesh gear box. This gear box is same
as the constant mesh gear box except dog
clutch is replaced by synchromesh devices.

12. • Synchromesh gear devices works on the
principle that two gears to be engaged are
first brought into frictional contact which
equalizes their speed after which they are
engaged readily and smoothly.
• The synchromesh looks like as the cone clutch
where the outer surface of cone consist the
frictional surface. This type of gear box is
widely used in automobile.

13. Run Video

14. Synchromesh Gearbox

25. Selection of Speeds
• A typical multispeed gear box is shown in figure.
• No.of speeds available at the spindle
Z = 3 x 2 x 2 = 18

26. Geometric Progression
• Progression or Step ratio = Φ is constant
• Φ – ratio between two successive speeds
• Φ = N2/N1 = N6/N5 = Nz/Nz-1, z –no.of speeds
• Φ=[Nmax/Nmin](1/z-1)

27. Advantages of Geometric Progression
• No of gears to be used is minimum
• More range of spindle speeds
• Layout is compact
• Speed loss is minimum
(Desired optimum speed –available speed)
• Speeds can be easily selected from preferred
numbers, because preferred numbers on G.P

28. Selection of Speeds from preferred numbers
• Basic series (R10 or R20, etc)
• Derived series (R20/3, R10/2)
• Non-standard speeds
• N1 = Nmin
• N2 = Nmin x Φ
• N3 = Nmin x Φ2

31. Basic series - Example
Find the progression ratio for a 12 speed gear box having
speeds between 100 and 355 rpm. Also find the spindle
speeds.

32. Derived series - Example
Select spindle speeds, for a 9 speed gear box, between
80 and 1285 rpm

33. Non-standard speeds - Example
Select spindle speeds, for a 12 speed gear box, between
50 and 800 rpm

34. Kinematic Arrangement/Layout

42. Problem-1

46. Calculation of number of teeth
Stage-3
Consider the ray that gives maximum reduction

48. Stage-2
Consider the ray that gives maximum reduction

49. Stage-1
Consider the ray that gives maximum reduction

70. Extra