clockwork
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| posted on 3/9/07 at 03:03 PM |
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centre of the car?
Trying to create a simple program a bit like this myself (and without the funky graphics).
 
suspProgram
To work out the roll center I need to know the center of the car, however this position changes when the car rolls/hits bump/droop. So for the
purposes of my program where should I locate it? Between the tyres?
"Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." Benjamin Franklin.
"Well if you have nothing to hide, you have nothing to fear" Morons the world over.
Locost/Kit builders info and FAQ website:- www.carbuilders.info
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Bob C
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| posted on 3/9/07 at 05:55 PM |
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you'd use the centre at the height of the centre of mass of the sprung components.
Guess at about a foot up from the bottom of the chassis (or the middle of the top of the chassis)
Bob
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clockwork
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| posted on 3/9/07 at 06:46 PM |
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I understand, that makes sense.
"Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." Benjamin Franklin.
"Well if you have nothing to hide, you have nothing to fear" Morons the world over.
Locost/Kit builders info and FAQ website:- www.carbuilders.info
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Bob C
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| posted on 3/9/07 at 09:30 PM |
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Actually centre of gravity height won't enter into geometric roll centre calculations, needed to determine roll couple....
Sorry typed without thinking
Bob
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procomp
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| posted on 4/9/07 at 07:22 AM |
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Hi without getting technical.
I wouldent worry to much about your roll center. There are more important things to take care off and chasing roll centers can mean you somtimes over
look more important areas of the desighn.
cheers matt
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clockwork
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| posted on 4/9/07 at 10:42 AM |
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Hmm, confused now as to where to place it. COG made sense as that is where the car is trying to roll around, however, tyre grip will try and resist
the roll...
With regard to whether I should worry about roll center, I know it is a contentious subject  but I can't believe it does nothing. As far as I
can see, long A arm lengths should limit camber change beyond small amounts (except at extremes), and I cannot see anything good about having roll
centers at the front and back moving all over the place. I doubt it would feel good at the drivers seat.
Anyway thankyou both for your opinions, I do appreciate them, even if I seem to be blindly ignoring them.
[Edited on 4/9/07 by clockwork]
"Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." Benjamin Franklin.
"Well if you have nothing to hide, you have nothing to fear" Morons the world over.
Locost/Kit builders info and FAQ website:- www.carbuilders.info
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clockwork
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| posted on 4/9/07 at 07:48 PM |
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Bu99er.
Just read this http://www.neohio-scca.org/comp_clinic/hand_out_reprints/Vehicle%20Dynamics2007.pdf
Now it could be complete nonsense, and it does go against most of the theory in my books... but it does make sense. Also it means there is no point
whatsoever in continuing my program. What was going to be a bit of trigonometry has turned into working out force application points.
Any thoughts?
"Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." Benjamin Franklin.
"Well if you have nothing to hide, you have nothing to fear" Morons the world over.
Locost/Kit builders info and FAQ website:- www.carbuilders.info
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Uphill Racer
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| posted on 4/9/07 at 10:27 PM |
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Hi clockwork, the graphics do help to understand whats hapening. Your pic shows the roll effect on the suspension, but the chassis rolling into the
corner....
Bill dont talk nonsense, sometimes on a different level to most though.
[Edited on 4/9/07 by Uphill Racer]
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clockwork
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| posted on 5/9/07 at 07:20 AM |
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Who's bill?
Also I note the .pdf shows a car with shorter lower arms than upper...
This is somewhat confusing.
"Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." Benjamin Franklin.
"Well if you have nothing to hide, you have nothing to fear" Morons the world over.
Locost/Kit builders info and FAQ website:- www.carbuilders.info
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Uphill Racer
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| posted on 5/9/07 at 10:15 PM |
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quote:
Originally posted by clockwork
Who's bill?
Also I note the .pdf shows a car with shorter lower arms than upper...
This is somewhat confusing.
Sorry, Bill Mitchell the guy that did the paper on roll centre that you linked to.
Yes the SLA is upside down as we would use it but the C o G lever arm would roll the chassis opposite to the view shown.
[Edited on 5/9/07 by Uphill Racer]
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