Just to add to the complication.........
Yes the rear axle housing moves in 2 very different arcs thayt are described by the length of the top locating arms and the bottom locating arms. This has the effect of causing a rotation of the pinion angle in the DOWNWARD direction under bump (compression) conditions. Torque of the driveshaft versus the friction of the tyres and the weight of the vehicle as the axles twist will attempt to force the pinion in an UPWARD direction.
NOW..... depending on where your rear suspensions instant centre is located(imaginary pivot point about which the whole rear axle swings) Will determine whether the vehicle has a tendancy to squat(compress) at the rear on launch. OR seperate(rise upwards) on launch. A lot of that is dependant on rear ride heigh in a Torana, as the pivot points are not easily adjusted.
When dealing with the theory of suspension movements.... NOTHING IS STATIC.
Cardboard cut outs and a few pins and you will see what I mean....
OH.... and those Edelbrock arms look trick..... Greasable Johnny joints are very cool......
Adustable Rear Arms
Started by
_rorym_
, Oct 05 2008 01:47 PM
58 replies to this topic
#52
enderwigginau
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Posted 06 November 2008 - 01:28 PM
Exactly Greg.
And the pinion "trying" to twist up causes the suspension to compress as it can't (fingers crossed) bend the trailing arms...........
Grant..
And the pinion "trying" to twist up causes the suspension to compress as it can't (fingers crossed) bend the trailing arms...........
Grant..
#53
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Posted 06 November 2008 - 08:21 PM
If the pinion rises and the arms can't deflect then I would be thinking that the resultant force would be lifting the body up and pushing the rear axle down.
I believe this is the basis of the slapper bar geometry and the later caltracs...
I believe this is the basis of the slapper bar geometry and the later caltracs...
#54
enderwigginau
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Posted 07 November 2008 - 12:33 PM
Only in equal arm geometry Greg.
The unequal arms in the torana, put force on the rear of the lower control which transfers to pull on the upper arms, which drives the diff up as the rear mounts are rearward of the upper.
AFAIK, LC/J is the same geom........
Does anyone have an engineering program to dummy it up on?
Grant..
The unequal arms in the torana, put force on the rear of the lower control which transfers to pull on the upper arms, which drives the diff up as the rear mounts are rearward of the upper.
AFAIK, LC/J is the same geom........
Does anyone have an engineering program to dummy it up on?
Grant..
#55
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Posted 07 November 2008 - 09:41 PM
Grant,
In theory, you are correct. But the offset in the arms and longitudinal forces are accomodated by deflection of the bushings in the fore/aft direction.
Just one of the reasons why solid mounts don't work in an unequal/non-parallel/ diverging 4 bar suspension linkage.
In theory, you are correct. But the offset in the arms and longitudinal forces are accomodated by deflection of the bushings in the fore/aft direction.
Just one of the reasons why solid mounts don't work in an unequal/non-parallel/ diverging 4 bar suspension linkage.
#56
_the gts_
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Posted 07 November 2008 - 11:26 PM
I am gonna run this past the guru engineer at work tomorrow cos you are all confusing the F*ck out of me, plus I will be sober at work!
anyone have measurements of how long the upper and lower trailing arms are and at what angles they are at if looking from top view e.g from the top down.
anyone have measurements of how long the upper and lower trailing arms are and at what angles they are at if looking from top view e.g from the top down.
Edited by the gts, 07 November 2008 - 11:29 PM.
#57
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Posted 08 November 2008 - 08:54 AM
Top arms diverge at around 30 degrees.
Top arms are around 40% of the length of the lower arms.
Lower arms should be close to parallel to the ground at ride height.
Top mounts on the diff end are perpendicular to the centreline of the axle tubes.
Lower mounts are rear set by around 1.5"
Front mounting points are around 2" further apart in the vertical plane than the rear mounting points. This will give an Instant centre that is non-converging and intersects at infinity.
PLEASE report back with your findings....
Cheers Greg..
Top arms are around 40% of the length of the lower arms.
Lower arms should be close to parallel to the ground at ride height.
Top mounts on the diff end are perpendicular to the centreline of the axle tubes.
Lower mounts are rear set by around 1.5"
Front mounting points are around 2" further apart in the vertical plane than the rear mounting points. This will give an Instant centre that is non-converging and intersects at infinity.
PLEASE report back with your findings....
Cheers Greg..
#58
Litre8
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Posted 08 November 2008 - 02:08 PM
So all very good but what did the Bathurst winning L34's and A9X's run as a rear end setup? They seemed to get around bends ok....
I did hear that on the early HDT Commodores they ran with only 1 of the upper arms connected (heard this from a ex-HDT mechanic)
I did hear that on the early HDT Commodores they ran with only 1 of the upper arms connected (heard this from a ex-HDT mechanic)
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Posted 08 November 2008 - 04:52 PM
Howard,
It is more likely that the one top arm (3 link) set-up was used on the Torana than the Commodore. The Commodores rear is a parallel 4 bar, and aside from the fact that the top arms are still shorter than the lowers it is a vastly superior set up to that of the Torana's upper diverging arms.
I beleve that this(3 bar,with panhard bar) is probably the set up that the faster L34 and A9X's would have used. Although with all design compromises there are many different "work arounds" So different teams could have employed variations of the same idea.
It is more likely that the one top arm (3 link) set-up was used on the Torana than the Commodore. The Commodores rear is a parallel 4 bar, and aside from the fact that the top arms are still shorter than the lowers it is a vastly superior set up to that of the Torana's upper diverging arms.
I beleve that this(3 bar,with panhard bar) is probably the set up that the faster L34 and A9X's would have used. Although with all design compromises there are many different "work arounds" So different teams could have employed variations of the same idea.
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