An oscillating axle is where one of the axles on an aerial lift pivots. There’s a lot of confusion regarding the purpose of this oscillation though. Many people see the axle and assume it’s used as a way to level off the lift for using it on uneven ground but this is not the case. The true purpose is traction. Manlifts used to be made with 2 solid axles. When an operator drove over a low spot it was very easy to have one or even 2 wheels off the ground. That’s not an ideal situation particularly if the lift is only 2 wheel drive. By allowing one axle to pivot the lift can maintain much better traction. It’s ironic that it’s now rare to find 2 wheel drive lifts because if properly equipped with an oscillating axle 2 wheel drive units perform reasonably well off road.
As I mentioned earlier what many customers want an oscillating axle to do is to level off the machine when they want to go up in the air. Because of safety reasons this isn’t allowed and lifts actually have systems where the axle locks and won’t pivot while the lift is in the air over a certain height.