# Pulseroller Products /Motor Rollers / Selecting Motor Roller Speed Code

You can always contact Pulseroller for assistance in properly selecting the right motor roller for your application, but here are some basic guidelines and calculations you can make to get good idea of what roller speed code to select.

• Conveyor Speed
• Number of idler rollers in your conveyor zone
• Interlocking method between motor roller and idlers

## Required Tangential Force

We will use the Required Tangential Force method to calculate the force needed based upon your data. The total force is equal to the sum of the force required to move the load plus the force required to drive the idler rollers

The basic equation is: FTotal = FLoad + FIdlers

## Calculate Force Required for the Load

To calculate the force (in N) for the load: FLoad = m x g x μr

Where:
m = Mass of Load in kg
g = Gravitational Constant = 9.8 m/s2
μr = Coefficient of Rolling Resistance of Load Material

Coefficient of Rolling Resistance (μr) for materials are typically ranges of values that vary depending on the particular quality of the material. The greater the value, the more force required, so using the higher value in the range is “worst case” scenario and should be used. Common materials and their values are:

Wood Steel Cardboard Plastic Rubber
0.02 ~ 0.05 0.01 ~ 0.02 0.05 ~ 0.1 0.02 ~ 0.04 0.1

## Calculate Force Required for the Idlers

To get FIdlers in N, we will use a formula that takes idler roller quantity multiplied by a force required per idler constant based upon the interlocking method:

Interlocking Method Formula
Two Groove with standard O-Bands1 FIdlers = Qty of Idlers x 0.85
Micro-V with 2-Rib Belts2 FIdlers = Qty of Idlers x 1.2
Micro-V with 3-Rib Belts2 FIdlers = Qty of Idlers x 1.8

## Calculate an Example

For an example, let’s use the following application data:

Load Weight 35 kg Cardboard 0.67 m/sec 7 Two Groove with standard O-Bands

Let’s assume the worst case for μr for cardboard = 0.1

FLoad = 35 × 9.8 × 0.1 ≅ 34N

FIdlers = 7 × 0.85 ≅ 6N

FTotal = 34 + 6 ≅ 40N

To select the speed code, we need to first find the speed code whose maximum speed matches closest to our desired speed and
then examine its Rated Tangential Force value to see if it meets our requirement.

We need 0.67 m/sec, so from the Performance Data Chart; a 35 Speed Code has a maximum speed of 0.81 m/sec.
The Rated Tangential Force for a 35 Speed Code is 49.7N. A 35 Speed Code motor roller should work for this application3.

1 O-Bands lose their transmission ability as the quantity increases. You should limit the number of O-Band idlers to 10 or less.
2 Various factors including load weight determine whether you need to use a 2-Rib or 3-Rib Micro-V belt. Contact Pulseroller details of your application if you are not sure.
3 Factors other than required force and speed can affect the proper speed code selection. Contact Pulseroller with details of your application.