steering ratios .....

[vivy]

hi , i was figuring out steering ratio for our car 2008 .. as our tyre aspect ratio is around 70 , are using 13inch rim hoosier tyres . as our aspect ratio is high,, the response time that is slope of cornering force v/s shear angle will be less steeper hence need to have fast steering .. smeone had said teams are using b/w 3 to 8:1 (from our competion xperience). so want some help from suspension xperts and other teams , wat steering ratio they are using. and wat factors they have undertook for their ratios. and specially with this specification of tyres

[vivy]

hi , i was figuring out steering ratio for our car 2008 .. as our tyre aspect ratio is around 70 , are using 13inch rim hoosier tyres . as our aspect ratio is high,, the response time that is slope of cornering force v/s shear angle will be less steeper hence need to have fast steering .. smeone had said teams are using b/w 3 to 8:1 (from our competion xperience). so want some help from suspension xperts and other teams , wat steering ratio they are using. and wat factors they have undertook for their ratios. and specially with this specification of tyres

[Christopher Catto]

some practical tips

1) i would say how much lock your driver can take in the cockpit before starting to get really annoyed

2) how quick the steering can be before the drivers arms get really tyred after 30mins of running.

consider your KPI and offset. if you have your suspension points very deep in the wheel then your steering "should" be lighter and hence you can run a quicker rack. this depends on the effect of a tyre rotaing around an axis. As described in Milliken, points deep in the wheel do not mean 100% that the steering will be lighter. if your wheels have low offset then the driver may get too tyred in the last 10-15 mins of the endurance.

sorry this gives no numbers but this explains why so many teams have different ratios. it is really down to what your driver prefers and what makes your car faster on the endurance. sure, the sprint is important but you will lose a lot of enduro points if your driver makes mistakes or simply ploughs into cones because he cannot steer fast enough.

i would say make the steering so you can turn all corners (except hairpins) of the track with for example 270deg total of handwheel movement. check with some previous cars of yours or ask some teams close to you, they are unlikely to keep this a secret.
so if 135deg of handwheel rotates your tyre 30deg, that is a ratio of 3.85 as an example. I cannot confirm this with any car, this is just my own example.

another thing. train your driver to push the steering wheel with the hand that moves up. this is a typical go karting technique. the hand moving downwards should never pull otherwise your arms will get tyred. also getting ready for the turns is important, so placing your hand in position so that after the handwheel movement the hand is at the top of the wheel, rather than having your arms crossed (which again requires more physical effort and can mean you have less control/strength)

last thing. document your research. for every project on the car you should have SHORT A4 sheet with

- tech details (the numbers!)
- 1 pic of the system, 1 pic of its installation in the car
- the reasoning for your choice (why?, why not? pros, cons)
- details of modelling or experimental testing or testing on the car
- some results and driver feedback
- why the system benefits your car (performancewise, moneywise, in terms of saving you time or effort)
- ideas for future development.