rack ratio and c factor !!

[Stefanos m]

hi people...
i was wondering what is the connection of rack ratio for a example 12:1 and the c factor (mm per 360 deg)...i am a bit confused

regards..

[JDS]

Rack ratio is steering wheel rotation divided by wheel angle rotation. So deg/deg or rad/rad. I've not heard of the c factor, however I think you simply referring to another way of specifying the relationship between rack movement and steering wheel rotation. In other-wards it is specifying how much tie rods are moving in millimeters per 360 deg of steering wheel rotation.

[Stefanos m]

Originally posted by JDS:
Rack ratio is steering wheel rotation divided by wheel angle rotation.

i think that you mean steering ratio(overall) which is steering wheel revolution /wheel steer angle for example 180 deg / 23 deg.

rack ratio is a gear ratio but i dont know what exactly...


take a look here..http://secure.chassisshop.com/partdetail/C42-334/

how we can calculate this 6.4:1 Ratio,
although our gears are not both circular(n1 teeth / n2 teeth)

[Crispy]

The c-factor is linear rack travel per full revolution, such as 50mm/360 deg or 2.0in/360 deg (I'm guessing the c stands for circumference). Steering ratio is degrees of steering wheel angle divided by the steered wheel angle. C-factor is a characteristic of the rack and pinion which contributes to steering ratio, but more information (steering linkage geometry) is required to define the steering ratio.

Some time spent reading RCVD chapter 19 should clear things up.

[BillCobb]

In the vernacular of the industry, the C-Factor (mm/rev) divided by 2pi is the effective pinion radius of the gear. To produce an overall steering ratio for the vehicle, you would design an effective steer arm length that is equal to the pinion radius times this overall ratio. Given the speed range you expect to operate in, the steering gain you need for maneuverability, the understeer that the vehicle has in the range of operation, the maximum road wheel angles that you need, the wheelhouse package that you have, the brake design, the Ackernmann fraction and the durability of the rack and pinion teeth, you design an appropriate C-Factor and steer arm length to meet all requirements of each sub-system. The C-Factor can be a nonlinear function, too, in order to produce gain increasing or gain decreasing action. Methods are in use in the industry to produce speed dependent C-Factors (as in the BMW/Bosch differentiator mechanism).

[Stefanos m]

Originally posted by Crispy:
The c-factor is linear rack travel per full revolution, such as 50mm/360 deg or 2.0in/360 deg

yes you ere right my friend but my question is the c-factor and rack ratio connection.

take a look here http://secure.chassisshop.com/partdetail/C42-334/

how we can calculate this 6.4:1 Ratio and what does it mean.

[Stefanos m]

Originally posted by BillCobb:
In the vernacular of the industry, the C-Factor (mm/rev) divided by 2pi is the effective pinion radius of the gear. .

thnx man,but i want to know how we can calculate rack ratio as i said to Crispy not overall ratio (but you are right)!

[BillCobb]

Now I understand. The website you reference didn't have a clue on what they have when I called them.

Best I can tell, 7/8 of a rev of the pinion produces 4.5 inches of rack travel. On my crude abacus made up of jelly beans, that all works out to a C-Factor of 130.62 Nicht var?

[Stefanos m]

Originally posted by BillCobb:
that all works out to a C-Factor of 130.62 Nicht var?

yes !!we have 114,3mm @ 315 deg so 130mm @ 360!!...i found this value too but, i think that is to big!! and then i said (what is the rack ratio?)..nevermind..thnx again man

[Crispy]

I get you now. That ratio number does not make any sense to me either...

A c-factor of 130mm seems like it could be reasonable. I believe ours is about 100mm. Total travel seems a bit long.