GaryMeades
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| posted on 16/11/04 at 03:43 PM |
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Castor Angle - Sanity Check
I'm just about to mount my suspension brackets to the chassis. I've designed a jig inspired from some fine examples in the photo archive
(thanks lads).
However, in calculating the relative horizontal (when viewed from the side of the car) positions of the top and bottom wishbones to achieve a castor
angle in the region of 5.5 degrees I need to be sure that I'm using the correct vertical distance between the top and bottom wishbones at the
upright ends.
(I'm using book chassis and bones dimensions and intend to gusset the brackets if they end up too far off the frame rails)
I've seen some drawings that show the 5.5 degree angle measured with the bones laying parallel to each other (when viewed from the front of the
car) which equates to a distance between bone ends of about 182mm.
But when using cortina uprights it would appear that the bones don't end up parallel but instead converge towards the chassis centreline
implying a longer distance than 182mm?
Anyone got a (book) completed front suspension setup with 5.5 castor, who could measure the distance between two fixed points at the ends of the top
and bottom wishbones for me please?
Does that make sense?
Cheers
Gary
[Edited on 16/11/04 by GaryMeades]
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dave69isit
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| posted on 16/11/04 at 03:49 PM |
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would this help
 
Rescued attachment FRONT JIG.jpg
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Mark Allanson
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| posted on 16/11/04 at 07:30 PM |
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Dougies jig plan will give abou 2°30' castor unless you modify the top wishbones. I fell into this trap, so redsigned the top bones. It worked
out OK because I was unhappy about moving the brackets to a precarious perch hanging on for grim life off the edges of the uprights - no amount of
gusseting will remove the angled leverage that this would give.
I have posted this before, but it does give the 22mm setback to give the castor, and now my car is driveable I can now say, hand on heart, that it
does self centre nicely
 
Rescued attachment Wisbone Modification.JPG
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Mix
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| posted on 18/11/04 at 05:22 PM |
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The distance between the upper and lower ball joint centres is aprox 225mm. At this distance a 22mm offset will give you 5.5 degrees of castor as Mark
says.
Mick
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MikeRJ
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| posted on 18/11/04 at 05:48 PM |
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quote:
Originally posted by Mark Allanson
I was unhappy about moving the brackets to a precarious perch hanging on for grim life off the edges of the uprights - no amount of gusseting will
remove the angled leverage that this would give.
The way I got around this was to weld an extra horizontal tube between the two upright tubes (FU and the front sloped one), and also moved the FU tube
backwards slightly. The top of the coilover gets a little close, but no closer than about 10mm.
Hang on, just knocked up a quick paint drawing:
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GaryMeades
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| posted on 18/11/04 at 10:37 PM |
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Thanks guys, for your help.
Gary
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Mix
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| posted on 19/11/04 at 04:29 PM |
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If you are going to make your own wishbones then you can adjust the dimensions to fit the 'L' and 'FU' members.
Mick
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