Download - Design of Gearbox
DESIGN OF GEARBOX (SPEED REDUCERS)
Motor Machine Tools & Engine Road wheels
To get different speeds – Gear Box
What would happen if accidentally shift into reverse gear? Would
the entire transmission explode?
What is moving inside the
transmission when move the shifter?
When hearing that horrible grinding
sound, what is actually grinding?
Components of Speed Reducers
Shafts for mounting gears
Bearings to support shafts and gears
Gearbox housing to support bearings, to hold lubricants and to protect
from dirt and dust
Provisions to prevent axial movement of the shafts relative to bearings
and to prevent axial movement of bearing
Space for oil reservoir
Oil level indicator, drain plug and inspection hole
Cooling fins
Provision for easy assembly and disassembly
Single Reduction
Double Reduction
Multi Speed changing
Since, Centre distance of the shafts A and B is fixed, it is essential that the
sum of the teeth of engaging pairs should be equal for same module
Z1 + Z2 = Z3 + Z4 = Z5 + Z6
Neutral condition First Gear engaged
5 speed Gearbox
Reverse Gear operation
PROGRESSION RATIO []
The ratio of adjacent speeds will be a constant called
progression ratio. The spindle speeds (output speeds) are
arranged in geometric progression.
If Nmax is the maximum speed, Nmin is the minimum speed, then
=
Progression ratio Ø =
Ø4 =
Ø4 =
Ø5-1 =
Ø r -1 = Ø =
Consider a five speed gear box, where N5 is the maximum
speed, N1 is the min speed and r is the number of speeds.
6 Speed Gearbox (2×3) or (3×2)
9 Speed Gearbox (3×3)
12 Speed Gearbox (3×2×2) or (2×3×2) or (3×2×2)
STRUCTURAL RAY DIAGRAM
Follow for all stages,
≤ 2 and ≥
If it is not possible,
≤
Structural formula: Z = P1 (X1). P2 (X2). P3 (X3)
Where P1, P2, P3 are speeds available in each stage
X1 = 1, X2 = P1, X3 = P1.P2
Principles to be followed to obtain optimum design:
Number of gears on the last shaft (spindle) should be
minimum.
Number of gears on the shafts should not be more than 3.
It is preferable to have nmax ≥ ninput > nmin in all the stages
except in the first stage.
The velocity ratio between the spindle and the shaft preceding
it should be the max possible.