Hollow Roller Design (braked dynos)

Despite theis higher complexity and cost, typically braked dynos use Hollow Rollers because the capacity of having longer axles, which are necessary for connecting the rollers between them (car dynos) and with the brake. Car dynamometers can also use hollow rollers for inertial dynos because it is necessary to connect them in pairs.

Advantages of hollow rollers:

• they don’t need dynamic balancing in most cases
• they are easier to build (despite the amount of job to machine de axles)
• they are easy to calculate. Using our spreadsheet you can get the inertia (MOI) using only the diameter and width (without axles)

Disadvantages of solid rollers:

Advantages of hollow rollers:

• They have long axles, which is necessary for braked dynamometers
• They are more efficient with respect their weight, typically 85% to 90% of the mass work as inertia

Disadvantages of hollow rollers:

• They are more complex to build and need to be perfectly dynamically balanced
• They are normally more costly
• They are difficult to calculate if you don’t have the exact sizes

Spreadsheet for calculations:

http://www.sportdevices.com/download/rollerssheet.xls