Expert: Paul Soderman - 11/29/2009

Question
Why are most all commercial flywheel power systems mounted in the horizontal plane as opposed to the vertical plane?

Answer
Mike
Neglecting design specific issues such as footprint and power takeoff direction, etc., the only difference between a horizontal and vertical flywheel is the gravity direction.  A vertical flywheel mass would be working against gravity on the rising side of the wheel and would be working with gravity on the descending side.  That is equivalent to an oscillating force driving the flywheel and might cause vibration or long term degradation to the bearings.  I assume that in many applications the effect is negligible.  For example, the flywheel in most cars is vertical because of the engine geometry, but the car only lasts 200,000 miles or so.  If a designer was concerned about precision and long life, I imagine he would prefer a horizontally mounted flywheel.
Paul