To start with, my brother built most of it, with some ideas and help from me. It's all 'home brew'!
The main ingredients are:
-Old BMW alternator as brake
-FS clutch bell
-FG-style spur-gear coupling between clutch bell and alternator
-Chineese load cell
-Old PC power supply for power
-LabJack I/O card
Alternator is feeding some resistor wire submerged in a bucket of water.
Exitation of alternator is PWM controlled from I/O card (IGBT)
Load cell measures the torque at the alternator
RPM is measured using a hall sensor, one pulse per rpm (I/O card measuring time between pulses)
Inertia of the assembly has been calculated using different weights on a string to accelerate it.
We are only running it as an inertia dyno at the moment, the inertia of the alternator is enough to load the engine doing sweeps. We thought this would not be enough when we started.
If you want to make your own I would recommend building an inertia dyno. It's easier mechanically and electrically, and it does the job.
If you want to buy the SW and I/O as a professional package, this could be of interest:
www.dynomec.com/If you want to do a cheap and maybe a bit complicated solution, this could be an alterative:
www.pelicanparts.com/techarticles/streetdyno/street_dyno.htmFor the mechanical part, you can use your imagination!
The inertia needs to be enough to make it take significantly longer to accelerate the engine to top revs compared to revving with no load. I would say minimum ten times longer.
The inertia of the rotating parts in the engine can also be taken into account when calculating total inertia of the rotating parts.
One Idea I have for making my own inertia dyno is using a small flywheel for a car, and drive it using a timing belt and gears from a car engine too, making the flywheel spin at ½ rpm's compared to the engine. Or you could have a special weight machined and run it at the same speed as the engine.
Running it with clutch or directly from the crank is also a matter of taste I suppose. If you have a clutch engaging at low rpm, you can still figure out at what rpm's the clutch should engage when used in the car.
Ready to run dyno:
www.trik-dyno.com/
