Suspension Tuning & Optimization: Suspended Mass Elastic Load Transfer
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Suspended Mass Elastic Load Transfer
02.24
| 00:00 | - Now that we've covered unsprung mass load transfer in the previous module, it's time to move onto the second contribution we'll discuss, the suspended mass elastic lateral load transfer. |
| 00:10 | For everyone's sake, from here on our, I'll just be referring to this as elastic load transfer. |
| 00:16 | Elastic load transfer refers to the contribution of the springs, anti roll bars and bump stops to load transfer. |
| 00:23 | These are all the elastic elements of our suspension because they all produce a force in response to being displaced. |
| 00:30 | Clearly, the bump stops are only part of the contribution, provided the suspension becomes compressed enough for them to be engaged. |
| 00:37 | In general terms, as we corner with the car, the sprung mass will take a roll angle. |
| 00:42 | The outside suspension compresses and the inside extends. |
| 00:47 | For a given lateral acceleration, the roll angle the sprung mass takes, will be partially determined by the total roll stiffness of the sprung mass. |
| 00:56 | This roll stiffness is made up of the combined stiffness of our elastic components. |
| 01:01 | The amount of force each of the elastic elements is subject to is a function of the roll moment. |
| 01:07 | Which as we touched on in the last section, is another way of saying torque. |
| 01:11 | The roll moment is the resultant torque from the lateral force that's applied to the sprung mass centre of gravity and the vertical distance between the roll centre and the sprung mass centre of gravity. |
| 01:23 | Some of you might have realised at this point that if we were to place the roll centre at the same location as the centre of mass, we'd have no roll moment. |
| 01:32 | No roll moment means none of the lateral tyre forces are reacted by the elastic elements. |
| 01:37 | In fact, if we were to place the roll centre above the centre of gravity, the car would actually roll in the opposite direction. |
| 01:44 | The inside suspension would compress and the outside extend. |
| 01:48 | This means that the car would be rolling into the corner instead. |
| 01:52 | This is true and at first glance, it may seem like a good idea to raise the roll centre to either coincide with the centre of gravity or even above it. |
| 02:01 | But we'll see why that's not a good approach in the next module. |
| 02:05 | In summary, the component of sprung mass lateral load transfer that comes from our elastic elements, is made up of the reaction forces of the springs, anti roll bars and bump stops. |
| 02:16 | The amount of reaction force they're subject to depends on the roll centre height. |
