大学生方程式赛车悬架资料

Error No. 1

This picture shows a classic design error that all Judges hate, and is considered a "Mortal Sin". Every year several cars are presented like this as teams ignore the advice or directions they are given.

The outer spherical bearings are threaded rod ends loaded in bending! The entire mass of the car, plus bump loads, weight transfer and brake torque are reacted to the chassis by bending the threaded shank of the lower joint. This is going to break! GTB! Do not do this!

The upper rod end is being asked to react brake torque in bending. It is also being carried in single shear on top of the upright. These errors are not so serious, but still examples of poor design.

The judges understand why teams do this. It makes camber adjustment easy, but there are better solutions. Teams will argue they have selected a rod end with sufficient bending capacity, but this argument will not hold with the judges. A Rod end with a sufficiently strong shank will be far too big and heavy, and as the thread roots are good stress raisers, the joint will probably crack and break anyway. In any case, we are talking about the Design Competition, and incorrect use of fasteners is not good design.

Some teams may build a set of adjustable suspension arms like this for testing. It enables them to determine optimum camber (and/or caster) angles, but when their testing is complete, they build a more appropriate set of components for the competition.

The inevitable consequence of bending rod end shanks is this!

Design Error Two

Okay, time for this months Design Error. I want you to look at these pictures and see how many design errors you can see. The assembly looks quite good on first view, but a closer look shows many errors.

Okay, where do I start?

1. The rod ends are loaded in bending. (See last months column)

2. They are in single shear.

3. The upper outer hex bolts are threaded into the upright with no positive locking.

4. There is no washer under the hex bolt head to stop the rod end body coming over the

bolt head in the event of a failure.

5. The steering arm is mounted with hex head bolts threaded into the upright with no

positive locking.

6. The caliper mounting plate is sandwiched between the upright and the steering arm.

7. It appears that the brake torque is fed to the upright by having the upright recessed

into the caliper mount

8. The caliper is also retained by the front steering arm bolt.

9. The brake rotor is attached to the hub by use of countersunk hex head bolts with no

positive locking.

10. The assembly restricts access to these bolts so they cannot be checked for tightness.

11. The very short stub axle shows that the distance between the hub bearings is

insufficient.

There may be more (Stress raisers on the edge of the caliper plate recess?) Feel free to find more for me please.

So, what looked okay at first glance was actually a disaster looking for a place to happen. I can promise you that if I see anything like this in Hockenheim next year, I will personally kick the butt of whoever is responsible (Or delegate someone else to do it if the designer is bigger

than me)

Remember, I am still available to answer design questions from teams on or