Backlashes

I'm concerned about the backlash on steering linkage in VW 1302 Super Beetle that's under restoring since last October. One or two ticking sounds are discerned when reciprocal movements on tie rod were forced by steering actions. This origin of the ticking must be sought at any rate in some hinge position of the linkage after removing the fuel tank out. Suspicious 4 ball joints were already replaced last time.

After the step of checking linkages this time almost of restoring procedure would over on this automobile except the correction on head light ill wiring and exhaust gas emission test.

Sampling method

When taken correctly furnished under such an environment there is no difference in daily rate nor practitioners with stable experiments,the universal datum can be taken in the experiments.

And the sampling method must follow the adequate ways suitable for statistical datum analysis being performed after that.

Additionally we may see some tendency or a slight possibility by a single experiments, so we must not make any haste to invite concrete conclusion.

Setting error

Determinations of the actual site must be unified in the same uniform ways to obtain repeatable and reproducible datum.

On horizontal scaler, to keep the continuous pressure to the hub circular surface from the device, 1,500gr weight was applied vertically to exert 400gr obliquely from the vertical side wall of the device. This is one of the most important arrangement to obtain stable and monotonous datum with adequate repeatability.

The error on the stage of device setting to the object is the matter to be eliminated as less as possible, in short the excluding any uncertain factors.

Impression on Volvo S40 T5

Driving Volvo S40 from Kyoto to Ikeda Kawanishi through Kameoka, I could understand the policy of the design and the actual dynamic performances. T5 means turbo and 5 cylinder model, the accel reaction had slight stepping feeling because of light effecting turbo actions, but the setting by the Volvo factory was almost perfect.

And what I wanna describe here this morning about S40 Volvo is that all the dynamic reactions are very similar with BC7 SUBARU Legacy LSi US model, but all the axle components had been transplanted from GC8 SUBARU Impreza GDB model with new genuine parts including Eg mount and arm bushes.

And natural aspiration motor function with flat4 layout brought no stepping accel reactions with exhilarating comfort.

What's measured?

What must be measured for wheel alignment and constructive geometry corrections?

Setback(Front Axle)

The anteroposterior shift of the position on one side of the front wheel hub. As the tolerance of the platform is narrow enough to be set for the reliable scaling point, we may do that on the posterior wheel house point.

Front wheel lateral offset

Front axle constructive errors are checked horizontally, perimeter flame, lower arms, upper arms and strut upper mounts comparing with the scaling points set on somewhere in the wheel house.

Included angle

The inclination value formed with KPI(King Pin Inclination) or SAI(Steering Axis Inclination) plus camber value. As a simple way, the R/L camber values are compared when steering turns 180 degree clockwise and counterclockwise.

Front cambers

The front camber value should be set evenly on R/L, because the front hub positions R/L are the only reliable scaling points for rear thrust angle that follows after front stage and is the most extraordinary important procedure.

On these steps the steering centric position and precise front toe value may be ignored because they would vary according to rear axle adjustments and they would be fixed as a final steps after the all of adjusting procedures are carried out .

TOOT(Toe Out On Turn)

The front inner wheel must be turned 2-3 degree less than outer frontal wheel that's 20 degree turned. These setting has deeply something to do with the total toe value and the latter is decided after actual driving tests because this angle is affected by dynamic reactions from another wheels.

Measuring devices

The device for measuring vertical wheel inclination was created by self-invention and innovation utilizing some adequate light wood material inviting the technology in Radio control model aeroplane construction with physical property of preventing distortion.

Hard disk drive plate is used as the absolute datum plane of the device.

Vertical continuation of this plane with 1719,75 mm distance is the center of the pendulum.

Horizontal continuation of the plane with 150mm distance fits on hub outer circular surface.

Though some popular coffee can is utilized as the horizontal adapter, the height with parallelism is calibrated by measuring with micrometer device at 10/1000 mm level.

On the other hand, horizontal scaler to measure toe values was prepared utilizing horizontal level meter with bubble position display glass tubes in two dimensions in addition to LASER pointer.

The level meter was recalibrated by disassembling glass tubes and by resetting firmly with accuracy in relations with own datum plane in two dimensions promptly.

Also the calibration was performed with LASER direction in relations with own datum plane by extending the scaling point to 10,000 mm.

The adapting point is not circular but two lines on 3 and 9 o'clock position with cylindrical shape, because of the convenience for keeping the device in parallel to the ground.

Measuring point

Setting measuring points on wheel alignments and constructive geometries is the most important thing on earth, because no floating nor drifting of zero points is allowed in order to obtain accurate numerical datum.

Very expensive wheel alignment tester system like the machinery equipped in the factory technical center has been adopted the circular points on wheel rim, but wait please here, alminum wheel has a permission to allow 1mm deformation as a tolerance on outer circle points?　Suppose 15" wheel, how much error were permissive prior to the measurements on wheel measuring points?

360*60*1/(2πr)=360*60*1/(2*3,14*15*25,4)=9,028(min.)

Judging from my experiences these 10 years, this value produces unacceptable strange steering reactions, easily leads to steering habits, right or left.

So, as for my experiments much more reliable measuring zero points were invited, they are hub outer circular surfaces, as conventional camber scalers uses this surface with magnetic contacts.

These surfaces were utilized on both measurement procedures, vertical and horizontal directions.