Front suspension roll centre height

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dynatune
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Joined: 28 Aug 2013, 11:03

Front suspension roll centre height

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I would like to follow up on the comment/observation from thisisatest "looking at the Ferrari front end, the upper wishbone slopes to a greater degree than the lower wishbone" which in my opinion is fundamental observation to understand current F1 front suspensions. In the video there is the generic "assumption" that the wishbones are parallel which correctly leads to a very high Roll Center on the front. Given the fact that a high roll center is not favorable for jacking forces which would make the front end of the car rise during cornering (and thus loosing downforce) such a high number for a roll center in such a low CoG car would certainly not create happy faces, neither for performance, neither for tire wear.
I have quickly modeled a generic F1 front suspension in my suspension tool and with perfectly parallel wishbones (inclined, but parallel) one can expect a Roll Center Height of somewhere around 220 mm. By "just" moving the inner pivots from the lower link down by 20mm and upper link pivots up by 20mm the Roll Center Height comes down considerably to somewhere around 60mm. These modifications are "visually" hard to detect since the "corresponding angle changes" are minimal for the human eye. For those who are interested I have printed a small Pdf document on the results for your review. It can be found here: http://www.dynatune-xl.com/documents.html
Along with the change in roll center height the change in lateral contact patch movement is evident. Although F1 front suspension do not move more that 20 to 30mm the range of the graphs give a pretty good "feel" for the changes.

Cheers,
dynatune

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Tim.Wright
330
Joined: 13 Feb 2009, 06:29

Re: To Push or Pull in 2014

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In your experience, do you know/think teams might be doing this regardless of it giving camber loss in bump?

It actually seems like a resonable apprach to me since front ride height control is probably more importantant than a few hundredths of a degree of camber. Especially so given the short stroke of modern suspensions and the possibility of just dialing more static or caster induced camber to compensate...
Not the engineer at Force India

dynatune
13
Joined: 28 Aug 2013, 11:03

Re: To Push or Pull in 2014

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Tim.Wright wrote:In your experience, do you know/think teams might be doing this regardless of it giving camber loss in bump?

It actually seems like a resonable apprach to me since front ride height control is probably more importantant than a few hundredths of a degree of camber. Especially so given the short stroke of modern suspensions and the possibility of just dialing more static or caster induced camber to compensate...

I would suspect every team on the grid to try to get the Front Roll Center Height as low as possible. When I was designing F1 suspensions the front kinematic rollcenter was below ground level (using the same "trick") but due to the lateral camber compliance (which will always move the "force based" roll center up, and that's the one that counts) we were between 0 and 50 mm. But lately a lot of teams have worked a lot on upright compliance reduction, one can see why :-). All other negative effects can more or less be compensated by static camber setting or caster induced camber with steering.

Cheers,
Dynatune, http://www.dynatune-xl.com
Last edited by dynatune on 17 Feb 2014, 15:31, edited 1 time in total.

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