Pros and cons of buying an used dyno
As new, modern modular rolling roads may be expensive, especially at the beginning of a new business, used dynos for sale are listed on various internet pages. There are better and worse developed dynamometers, but in most cases, the whole idea of chassis dyno is expected – a steel crate with rollers, sometimes twin-rollers. 4Wd (4x4) dynos may have a front axle connected to the rear with the belt or driveshaft, but most older dynos have no front-to-rear connection and are intended to stabilize and equalize roller speeds with electromagnetic brakes.
There is nothing wrong with buying such old machinery, especially if the price is reasonable. But some important things must be considered for future use:
- What is the surface of rollers? The flat steel surface will be slippy. Knurled (corrugated) rolls are better.
- What are the possibilities to install new sensors to enable the usage of new, modern dyno software?
- When we consider one axle dyno – will this be expandable to a 4wd dyno? Old dynos are not modular. Usually, to convert it to 4wd, you need to consider the enormous work and material costs.
- If 4wd used dyno is taken into consideration – it is essential to have a front-to-rear connection within or to be able to add it. Modern cars, even one-axle driven, need all four wheels to rotate to avoid traction control failures, power reduction etc.
- What is the weight of rollers? Heavier ones are better. Also, thin-wall rollers cannot be curled (corrugated) in the future.
- Does the dyno have a pneumatic ramp to lock rollers and lift the car?
- If the dyno is equipped with electromagnetic brakes, what voltage and current are needed to control them? As there are many different types of eddy current brakes, not all modern dyno controllers will be attached to them.
- What type and accuracy is the force sensor (extensometer) at the electromagnetic brake? Again, it is crucial to have an extensometer compatible with the new control system – or a separate controller will be needed. It increases the project's total cost.