Category Technical Talk

Automobile Suspension Design 101 (Part II)

In Part I of this article, I provide a general review and some background knowledge of the automobile suspension system. There are four types of suspension geometry. In this article we will briefly analyze the first type: trailing arm.

A trailing arm system is using a solid arm, which connect one end to two locations of the car chassis (so it can only “swing” in a 2-dimensional plane); and the other end is connected to the wheel hub, with the wheel hub fully fixed to the arm.

Because the arm connected to 2...

To most people, the meaning of suspension systems are: something that can absorb unevenness of the road surface, which makes it comfortable to ride in the car. Although this description is correct to an extent, it is a quite shallow understanding though. There are much more interesting facts that we can explore.

First let’s go to the root of the topic, we look at the car’s wheel hub: assume there is no restriction/connection to the wheel hub, which means it is a totally independent object to the car body, what property will it have?

Six Degrees Of Freedom

The answer is: the wheel hub will have 6 types of movement, we call it 6 degrees of freedom...

For most non-luxury car engines, each of its cylinder bores needs a cast iron liner to resist the heat and friction generated by the moving piston rings; on some luxury car and sports car, composite material spray (a.k.a thermal spray) techniques are used. For example Nissan GT-R’s engine, the inside the aluminum bore surface is treated with a layer of spraying molten iron, therefore no liner is required, which saves weight and provides better heat conduction.

Because the sprayed metal layer is extremely smooth, it raises energy efficiency by reducing the friction inside the engine. However, the benefit comes with cost...

In a nutshell, a linear generator (full name: Free Piston Engine Linear Generator, FPEG) is an internal combustion engine that generates electric power directly.

Recently R&D engineers in Toyota has made breakthrough in this area, and presented the concept at the most recent SAE meeting in Detroit.

Below are three illustrations from Toyota R&D, that explained the idea briefly.

Last week I have discussed the GM 8AT and the ZF 9AT, today let’s take a look at the Aisin AA80E, which is used in the Lexus IS350, GS350, LS460, IS-F and the upcoming RC-F.

Unlike other longitude mounted 8AT such as the ZF 8HP and GM 8L90, the Aisin transmission uses compound planetary gear sets. A compound planetary gear set is a planetary gear set that has multiple sun gears or multiple ring gears. There are different types of them, the one we are interested in is called the Ravingeaux gear set, which has two sun gears, two planet carriers and they share one common ring gear.

One Ravingeaux gear set can provide 4 forward gear ratios and also the neutral and reverse.

T...