Of course you can use as many belts you want (or have 😉 to tighten the car to the dynamometer.
China Brake Drum Series Factory39;s see most common mistakes:
1. If sensor is located at the # rear drum, measured power may be lower than real.
One of most common sources of troubles while measuring cars & vans with rolling road dynamometer is to position a car properly at the dyno. Then, while un-clutching to neutral gear, car “simmers” into rolls and static rear roll is empowered now with energy delivered by tire. Moving vehicle axle to the front of symmetry point of dyno roll/rolls may cause more spectacular problems.
Jack “Dyno” Simmard, VtechDyno Chassis Dynamometers
Jack “Dyno” Simmard, VtechDyno Chassis Dynamometers.
What may happen when we set the vehicle in opposition to the situation described above – another day. But they have their own elasticity and even very thick belts intended for heavy forces may be longer a bit while being tensioned. This is result of tires loosing contact with drums, thus causing some inertia of drums not be considered in whole result or being added improperly (for instance added as losses fully, and as load – in part). In that case while pulling, traction forces will move vehicle to the front of the rolling road. Two problems may happen: first is that car will have higher power measured than real (if sensor of rotation is at front roll – this is usual with chassis dynamometer with eddy-current brake). In two drums per axle dynos we may observe climbing of wheel onto front drum, along with releasing traction force from rear one. User of dynamometer should focus on proper set up of driven axle. Empowered axle is moved (located) to the front against symmetry point of the rolling road drums (if dynamometer has a pair of drums like that one pictured below) or middle of the roll (in single chassis dynamometer). In one drum per axle dyno, tire of the car may touch covers of dyno, causing burning or damaging tires but also jumping the car out of the dynamometer. Improper or not precise set up and alignment will effect in not only wear of tires or cuts in rubber, but even real accident. Dynamic friction will burn tire in seconds. I know this from autopsy. In two drums per axle chassis dynamometers such risk is minimized, but while releasing gear to neutral at top speed, car may burn tires because of friction against rear drum (imagine critical situation, when rear drum was not spinning at all because the car was able to “climb” enough onto front roll to cause fully loosing friction between tire and rear roll