speedyxjs
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| posted on 6/11/08 at 11:17 AM |
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Castor - Negative or Positive?
Looking at Dave Andrews page i saw this:
Do i want Negative or Positive castor?
How long can i resist the temptation to drop a V8 in?
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mookaloid
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| posted on 6/11/08 at 11:21 AM |
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Negative for self centering 
quote:
Originally posted by britishtrident
quote:
Originally posted by mookaloid
Negative for self centering
No positive --- the drawing is wrongly labled
Edit: Ok it should be as in the one labelled negative even if it is labelled incorrectly 
[Edited on 8/11/08 by mookaloid]
"That thing you're thinking - it wont be that."
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mikeb
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| posted on 6/11/08 at 11:23 AM |
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assuming the king pin line is the front wheel, negative castor angle.|
The more king pin inclination hence castor angle the more mechanical trail which gives you self centering hence steering stability.
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speedyxjs
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| posted on 6/11/08 at 11:33 AM |
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Ok. How much do i need and how will i measure it when fitting brackets?
How long can i resist the temptation to drop a V8 in?
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britishtrident
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| posted on 6/11/08 at 11:47 AM |
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The drawing is wrongly labeled
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britishtrident
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| posted on 6/11/08 at 11:49 AM |
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quote:
Originally posted by mookaloid
Negative for self centering
No positive --- the drawing is wrongly labled
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 6/11/08 at 11:57 AM |
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Not often Dave Andrews gets it wrong but this how it should be.
Negative caster is used on some front wheel drives -- Mainly BL Minis to give stability while accelerating.
Positive caster for RWD car -- light cars need more than large cars.
 
Rescued attachment fronta.gif
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 6/11/08 at 12:04 PM |
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http://crcc.org.uk/rc-technical.php
http://en.wikipedia.org/wiki/Caster_angle
 
Rescued attachment positive-caster.jpg
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Alan B
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| posted on 6/11/08 at 12:17 PM |
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quote:
Originally posted by mikeb
assuming the king pin line is the front wheel, negative castor angle.|
The more king pin inclination hence castor angle the more mechanical trail which gives you self centering hence steering stability.
Actually isn't king pin inclination the angle when viewed from the front?
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Hellfire
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| posted on 6/11/08 at 12:35 PM |
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quote:
Originally posted by speedyxjs
Ok. How much do i need and how will i measure it when fitting brackets?
That depends on what type of driving you intend doing. Anywhere between 0 to 7 degrees. Most aim for about 5 degrees. It's the shape of the top
wishbone and not the wishbone brackets you need to be overly concerned about. Obviously the brackets need to be to the same dimensions either side
(within tolerance).
Phil
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iti_uk
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| posted on 6/11/08 at 01:09 PM |
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quote:
Actually isn't king pin inclination the angle when viewed from the front?
You're thinking of camber. Castor is, as above described, the angle between the kingpin and the vertical plane, +ve if "tilted
backwards", -ve if "tilted forwards".
You want +ve castor and -ve camber.
Chris
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g.gilo
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| posted on 6/11/08 at 03:06 PM |
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caster kpi
hi
i get a bit woried when you read a post like this one, some of the guys giving advice and i assume building a car seem to be a little short of the
correct terms / skills ?
looking at the car from the front, draw a line through the centre of the top and bottom ball joint and that is your king pin inclanation, castor is
when you look at the same line from the side of the car. simple. graham.
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matt_claydon
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| posted on 6/11/08 at 06:09 PM |
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quote:
Originally posted by g.gilo
hi
i get a bit woried when you read a post like this one, some of the guys giving advice and i assume building a car seem to be a little short of the
correct terms / skills ?
looking at the car from the front, draw a line through the centre of the top and bottom ball joint and that is your king pin inclanation, castor is
when you look at the same line from the side of the car. simple. graham.
This is correct. KPI is not necessarily the same as camber though as that depends on the geometry of the hub/upright. This diagram show zero camber
but considerable KPI:
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Alan B
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| posted on 7/11/08 at 08:51 PM |
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quote:
Originally posted by iti_uk
quote:
Actually isn't king pin inclination the angle when viewed from the front?
You're thinking of camber. Castor is, as above described, the angle between the kingpin and the vertical plane, +ve if "tilted
backwards", -ve if "tilted forwards".
You want +ve castor and -ve camber.
Chris
Nope...I'm not.....definitely thinking of KPI..which is definitely measured in the front view (as is camber also)...I don't disagree with
your definition of castor.....just being clear about KPI that's all
[Edited on 7/11/08 by Alan B]
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britishtrident
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| posted on 8/11/08 at 09:09 AM |
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(1) Drawing on Dave Andrew's site is WRONG with regard to caster .
(2) In positve caster the virtual kinpin line tillts backwards when viewed from the side as in the drawing below
(3) RWD drive cars normally need positive caster
(4) With ball joint suspension to get positive caster the upper ball joint centre should be aft of the lower ball joint's centre.
If in doubt check the above in any authoritative automotive text book.
positive-caster.jpg
[Edited on 8/11/08 by britishtrident]
 
Rescued attachment positive-caster.jpg
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 8/11/08 at 09:25 AM |
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quote:
Originally posted by matt_claydon
This is correct. KPI is not necessarily the same as camber though as that depends on the geometry of the hub/upright. This diagram show zero camber
but considerable KPI:
Nice illustration 100% clear
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Syd Bridge
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| posted on 8/11/08 at 11:05 AM |
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I've kept out of this so far, but,
quote:
Originally posted by g.gilo
i get a bit woried when you read a post like this one, some of the guys giving advice and i assume building a car seem to be a little short of the
correct terms / skills ?
Amen to that brother!!!! Some of the noisiest on this forum have the least proper knowledge. And worst of all, rely on that cursed Wikipedia for
their misinformation, or what they read on other similarly misinformed forums.
Castor...is ALWAYS POSITIVE. ie. Kingpin or effective kingpin angle leans back at the top when viewed from the side. Negative castor is
suicidal. Does the opposite of self centering.
KPI...Is always positive. But can be zero on occasions. ie. Viewed from the front, the effective kingpin angle leans in at the top. Never negative,
for the same reasons above.
Cheers, Syd.
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Rod Ends
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 posted on 8/11/08 at 02:51 PM |
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Positive camber!
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