Roller Designer


This wizard will help you design a chassis inertial dyno, also known as a roller dyno.

Introduction

There is no single model of chassis dynamometer. They can be built in different ways, each with its advantages and disadvantages. Many times the conditioning factor is the cost, other times the availability of material, other times the size of the lathe, etc.

Here you can try different designs. You will be given a dimensional result, but also a simulation of the acceleration time of the vehicle in this dyno.

Roller Design

Select the dyno model. Each design has advantages and disadvantages, such as slippage, the final weight of material, which affects the cost, ease of manufacturing or obtaining materials.

Roller for bikes/kart with thick walls and large diameter.
The roller drum walls is what provides inertial mass.
One simple roller: for motorbikes or for karts resting only one wheel on the roller
One long roller: both wheels of the kart rest on the roller
Two rollers attached: in karts or ATV, each wheel rests on each roller.

Advantages: less losses, better traction.
Disadvantages: higher cost (larger weight).

Roller for bikes/kart with thin walls, low diameter, with inertial flywheel.
The flywheel is what provides the main inertial mass.
Usually a short roller for one wheel or it can be made with two rollers joined inline.

Advantages: lower cost (lower weight). Ease of getting material.
Disadvanages: possible slippage, high losses,
higher ground clearance, high RPM

Car roller with thick walls and large diameter.
The roller drum walls is what provides inertial mass.
The wheel has only one point of contact.
These are two rollers joined by their axle.

Advantages: less losses, better traction.
Disadvantages: higher cost (larger weight).

Car roller with thin walls, low diameter with inertial flywheel.
The flywheels is what provides the main inertial mass, not so much the rollers.
Because they are small, the wheel always rests between two rollers. It has two points of contact.
It can have two or 4 flywheels.

Advantages: lower cost (lower weight). Ease of getting material.
Disadvanages: possible slippage, high losses,
higher ground clearance, high RPM

Vehicle Power and Speed

The goal of the roller dyno is to simulate the load received by the vehicle and consequently the engine. This load affects the acceleration time, the more load the acceleration time will be longer, the less load it will accelerate faster.

We recommend that you use the power and data of the most common vehicle you will be working on. This way the dyno will be optimally sized and loaded for that range of vehicles, and will still perform well at nearby powers, both above and below.

Roller Dimensions

Lightweight roller with inertial flywheel
Heavy roller with thick walls, without inertial flywheel

Results

Understanding these results:

The most important thing is to compare the acceleration times indicated by this simulation with the times obtained on the track, for the initial and final RPM range entered, on a straigh track at full throttle.

If the indicated time is less than the time the vehicle actually has on the track, then it is convenient to increase the inertial mass to give it more inertia and consequently more time.

If the time indicated in the simulation is significantly greater than the time the vehicle makes on the track, then the simulated dyno is heavy. You have the option to build the lighter roller, or it will also be possible to use it if you roll in a lower gear. To simulate the roll in a lower gear, enter the cutoff speed that you would have in a lower gear. For example, if the cutoff speed in km/h was loaded for 5th, try entering the cutoff speed for 4th or 3rd gear.

Results are approximate. There are several data that have been estimated, such as power losses or the shape of the power curve. For this reason, the results should be taken with caution.

In any case, the tolerance is very wide. In other words, even though the acceleration time in reality is very different from the time in this simulation, it is very likely that the performance of the test bench is very good. Take special care when the acceleration time is less than 2 seconds, since we are in an area where the motors can have erroneous behavior. The same happens if the acceleration time is very long compared to the acceleration time that the vehicle has on the track.