Steering angle in front suspension [Archive]

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yofa

09-30-2003, 10:21 PM

I'm just wondering how much steering angle other teams have built into their front suspension.

With the crazy scrub radiuses and kingpins I've seen thrown around, I'm curious if any team has actually built a car that could not navigate around the smallest radius turn specified in the rules.

Bob Mai
Suspension team
University of Manitoba

yofa

09-30-2003, 10:21 PM

PatClarke

09-30-2003, 11:44 PM

Try about 1.5" scrub radius, about zero KPI, about 6 or 7 degrees of caster, lots of Ackermann, and as much camber as your tyre needs to work. You will need a degree and a bit camber gain per inch of travel, and don't build in any more travel than you need.
You will not be far wrong.
Pardon the lack of specifics...that is your job.
PDR

Rudeness is a weak mans imitation of strength

dancin stu

10-01-2003, 02:11 AM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by Yofa:
I'm just wondering how much steering angle other teams have built into their front suspension.

<HR></BLOCKQUOTE>

im reckoning on about 20 degree total steering, otherwise you will have difficulty maneouvering the car round in the paddock.

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>I'm curious if any team has actually built a car that could not navigate around the smallest radius turn specified in the rules.

<HR></BLOCKQUOTE>

i believe Chalmers had trouble getting round the tightest corner ont he Formula Student track this year, they were having to powerslide round the corner!

dancin stu

10-01-2003, 02:18 AM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by Suddenlee:
Try about 1.5" scrub radius<HR></BLOCKQUOTE>

seems a bit excessive with no KPI, i feel your drivers would be very tired after a small amount of time in the car.
Try 1" as a max

ben

10-01-2003, 03:51 AM

Zero KPI is good from a kinematic point of view, and to acheive it you will always end up with a large-ish scrub radius.

Get your drivers down the gym and they'll be fine :-)

Ben

University of Birmingham
www.ubracing.co.uk (http://www.ubracing.co.uk)

PatClarke

10-01-2003, 04:03 AM

haha Stu, your drivers have to do some work, otherwise there is no feedback. In a car that should have no more than 50 kilo wheel weights, the amount of offset is not too much. As Ben says, get your drivers fit.
PDR

Rudeness is a weak mans imitation of strength

ben

10-01-2003, 08:44 AM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by Suddenlee:
In a car that should have no more than 50 kilo wheel weights, the amount of offset is not too much. <HR></BLOCKQUOTE>

Quite. Offset is obviously important when you're doing high speeds with high downforce.

If you read the recent Racecar Engineering article by Andrew Thorby he explained how he used very little offset on the Lister LMP. He has an order of magnitude greater loads though.

Ben

University of Birmingham
www.ubracing.co.uk (http://www.ubracing.co.uk)

MercerFSAE C. Burch

10-01-2003, 11:47 AM

Don't forget that the dynamic scrub radius, the one that actually matters in a corner, will be less than the static scrub radius due to tire deflection. So if you start with 1.5" it might get down to 1" or .5" with tire deflection.

-Chris

Frank

10-01-2003, 04:19 PM

26deg / 37.2deg (app 100% ack @60" WB)

regards

Frank

Schumi_Jr

10-02-2003, 11:53 AM

I would recommend that you design in more steering than necessary. If you go off course you want to be able to turn yourself around quickly. It is also nice when driving/testing the car outside the competition to have an extra tight turn radius.

Aaron Johnston
University of Waterloo FSAE

www.eng.uwaterloo.ca/~fsae (http://www.eng.uwaterloo.ca/~fsae)