Chippy
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| posted on 21/4/06 at 10:33 PM |
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Very strange.
Reading my Haynes Sierra manual I note that the caster is stated as one point five two degrees, which doesn't seem a lot. On the book for my
Citreon Xara it states one point three degrees, but then goes on to say Kingpin angle ten point five degrees. Surely the kingpin angle is the caster
angle, or am I missing something here. What do the expert say?. Regards Ray.
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alister667
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| posted on 21/4/06 at 11:35 PM |
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OK I'm no guru, but as I understand it the kingpin and castor angles are different. The castor is the angle the line of steering rotation (ie
between top and bottom ball joints) makes with the vertical as viewed from the side.
The Kingpin angle is the angle the line of steering rotation (ie between top and bottom ball joints) makes with the vertical as viewed from the
front.
The castor is the angle front to back, the kingpin is the angle leaning in towards the centre of the car.
I think.
Hope that makes sense.
http://members.lycos.co.uk/alister667/
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greggors84
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| posted on 22/4/06 at 01:54 AM |
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Kingpin has more to do with Camber than castor, that may be where you have got mixed up.
Chris
The Magnificent 7!
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nitram38
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| posted on 22/4/06 at 03:26 AM |
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Kingpin inclination, tilts your front wheels into the turn so that the camber change means there is more contact patch of your tyres in contact with
the road.
Castor is the angle that forces you wheels to self center. It is abit like the castors on a shopping trolley in that the wheels will always point in
straight ahead if you take your hands off the wheel.
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Syd Bridge
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| posted on 22/4/06 at 11:07 AM |
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quote:
Originally posted by greggors84
Kingpin has more to do with Camber than castor, that may be where you have got mixed up.
KPI is more a function of fitting everything in and clearances, then aiming for centrepoint steering and accepting what can be done in the confines
given.
Castor is there to give self centering, and to overcome the effects of kpi only in some very particular circumstances.
Purpose designed racecars have very little kpi, and caster to suit the drivers need for how he wants the car to feel.
Cheers,
Syd.
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Chippy
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| posted on 22/4/06 at 10:58 PM |
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Syd Bridge
Hi Syd, I made a bit of a mistake when I said that the Xara had one point three deg's of caster, it has in fact only got zero point three
deg's. I actualy got under today and could see exactly what you mean, about the KPI. Maybe you can say why we need 5+ deg's on a locost to
get any self centreing, while cars like the Xara don't. Regards Ray
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greggors84
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| posted on 23/4/06 at 05:00 PM |
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Less weight on the front end of a locost? Usually the reason why BECs have a harder time than CECs. You need some weight to push the wheels back
straight.
Chris
The Magnificent 7!
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Liam
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| posted on 23/4/06 at 06:02 PM |
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Caster angle sets up trail - i.e. the tyre contact patch is behind the line where the steering axis would intersect the road, viewed from the side.
It's the trail that gives self centering. However you dont necessary need caster angle to create trail - you can just move the axle line
backwards behind the steering axis. A shopping trolley is the best example of this - the caster angle is actually 0 but there is considerable trail
giving the self centering. Maybe the citroen upright/strut geometry incorporates some trail without caster??
Liam
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