Calculation example

Given:

To design a roll table drive for heavy conveying duties. Under start-up conditions the 2.5 times the running torque is exerted on the timing belt.

The application conditions are:
Power P = 10 kW
Nominal speed n = 800 rpm
Start-up torque M = 300 Nm
Ratio, number of teeth i = 1, z = 25
Centre distance a = 625 mm

Required:

The timing belt pitch is to be determined and the belt width is to be designed.

Belt length:

Preselection profile: AT10. Calculation of the belt length with formula:

L = 2 * a + z * t = 2 * 625 + 25 * 10 = 1500 mm

Calculation of belt width:

1. Tooth shear strength

In the calculation it will be used  z_e = 12 (see basis of calculation).
Calculation of the belt width with the nominal speed of the power equations.

\begin{align}
b&={1000 \cdot P \over z_1 \cdot z_e \cdot P_{spez}}\\
&={1000 \cdot 10 \over 25 \cdot 12 \cdot 6,96}\\
&={4,79 cm}={47,9 mm}
\end{align}

Calculation of the belt width under start-up torque when rotational speed n = 0.

\begin{align}
b&={100 \cdot M \over z_1 \cdot z_e \cdot M_{spez}}\\
&={100 \cdot 300 \over 25 \cdot 12 \cdot 11,70}\\
&={8,54 cm}={85,4 mm}
\end{align}

The belt width is to be determined from the least favourable load conditions.
Selected: next larger standard belt width b = 100 mm.

2. Tension cord strength

The corresponding circumferencial force can be calculated from the general data supplied:

\begin{align}
F_U&={2 \cdot 10^3 \cdot M \over d_0}\\
F_U&={2 \cdot 10^3 \cdot M \over 79,58}={7539 N}<{16000N}
\end{align}

The tabular value F_zul for AT 10 with 100 mm belt width is 16000 N. Thus, there is a sufficient tension member safety factor.

3. Flexibility

The design is a drive "without contraflexure". The minimum number of teeth shown in the table are observed.

Result:

The drive is designed correctly with a belt width of 100 mm. A maintenance-free operation can be expected.

Order reference: CONTI^® SYNCHROFLEX timing belt 100 AT 10 / 1500