# Formulas for Piston effort & thrust in connecting rod - Theory of Machines - 1

Q.  Match the following Group 1 items with Group 2 items

1. Piston effort (FP) ----------------------------------- A. FQ sin (θ + Φ)
2. Thrust in connecting rod (FQ)  ------------------- B. FQ cos (θ + Φ)
3. Tangential force on crank shaft (FT) ------------ C. Fg – F1 + FF + WR
4. Radial force along crank shaft (FR) ------------- D. FP / cos Φ

- Published on 06 Aug 15

a. 1 – A, 2 – C, 3 – D, 4 – B
b. 1 – B, 2 – D, 3 – C, 4 – A
c. 1 – C, 2 – D, 3 – A, 4 – B
d. 1 – B, 2 – A, 3 – D, 4 – C

ANSWER: 1 – C, 2 – D, 3 – A, 4 – B

#### Discussion

• Sravanthi   -Posted on 19 Oct 15
- Static and dynamic force analysis are considered during the study of force analysis in IC engines.

1) The net force acting on the piston along the line of stroke is called as piston effort.

- It is given as Fg – F1 + FF + WR

here,

Fg = net gas force, FI = Inertia force, FF = Frictional force, WR = Weight of reciprocating parts.

The net gas force acting on the piston is opposed by the inertia forces caused due to acceleration of reciprocating parts. These inertia forces caused due to retardation of reciprocating parts act in same direction as that of net gas force.

2) Thrust acting on connecting rod is given as FP / cos Φ

here,

FP = Piston effort

3) Tangential force on crank shaft is given as FT = FQ sin (θ + Φ)

here, FQ = Thrust acting on connecting rod

4) Force acting on radial in direction is given as (FR) = FQ cos (θ + Φ)

here, FQ = Thrust acting on connecting rod

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