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PostPosted: Sun Jun 17, 2012 3:29 pm 
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The tire size is another "guesstimation". I measured the tires that are on the ranger now at about 24.5".
I'm looking for 5 inch ride height with LCA parallel to ground and the roll center just above the frame bottom.


Attachments:
File comment: Maybe not so bad?
Below frame roll center.jpg
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1984,2.8,5sp.jpg
1984,2.8,5sp.jpg [ 217.13 KiB | Viewed 682 times ]
Side001.jpg
Side001.jpg [ 64.72 KiB | Viewed 682 times ]
Front001.jpg
Front001.jpg [ 107.75 KiB | Viewed 682 times ]

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Last edited by STranger 7 on Sun Jun 17, 2012 4:18 pm, edited 1 time in total.
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PostPosted: Sun Jun 17, 2012 4:02 pm 
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One of the hurdles to overcome when the hole for the bottom ball joint is re-reamed might be finding a ball joint large enough to fit.

These measurements aren't real , just for reference.


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re-reamed.jpg
re-reamed.jpg [ 35.65 KiB | Viewed 679 times ]

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PostPosted: Sun Jun 17, 2012 7:07 pm 
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For a 25" od, if you flip the lbj, there won't much if any room for a spherical at 6.5" o.c., to allow for an inner pivot on the frame at 6.5" o.c., for 5 inches of ground clearance.

I don't see an issue on the steering geometry. Just look at the prescribed arc of the arm with the wheels parallel/straight. Is it an ackermann issue that cannot be resolved sufficiently with moving the rack forward or aft from o.c?

Why don't you use the vic spindles and brakes with your vic wheels?

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PostPosted: Mon Jun 18, 2012 1:38 am 
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STranger 7 wrote:
One of the hurdles to overcome when the hole for the bottom ball joint is re-reamed might be finding a ball joint large enough to fit.

That issues has come up in my mind, though there are a few potential ways it could be solved. One thing I had considered is reaming it out and then adding a tapered (hollow conical) spacer to reduce the size of the hole back down.

STranger 7 wrote:
Two problems with the "out rigger" approach ( the top 2). The holes for the ball joints, Size and Alignment, and the steering arm not in line with the ball joints by a good bit. The good news is I may not have to shorten the rack!

Is there any reason you couldn't make the "out rigger" with a different ball joint, which is easier to attach? You don't have to mimic the end of the I-beam exactly, only the ball joint mounting locations. If that doesn't make sense, let me know, and I'll try to post a pic of what I mean.


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PostPosted: Mon Jun 18, 2012 7:05 am 
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Miatav8,MstrASE,A&P,F,

The steering geometry issue concerns bump steer. With the spindle steering arm inches further O.B.
the pivot points on the rack will need to be adj. O.B. as well. I'll work up a drawing to illustrate.

I don't have a Crown Victoria ( yet but that's another story). I saw a set of CV wheels on Craigs List that Looked like they might work.



Posthumane,

Even with a spacer I would not be comfortable removing that much mass from the spindle. The extension might work. The upper ball joint mount looks like it should handle a 3" to 4" lever without failing.

I think I understand what you are are saying about a different joint. It would be worth trying to find alternates with the same , or close, tapered shaft dimensions.

I see I need to learn how to use the quotes feature.

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Last edited by STranger 7 on Mon Jun 18, 2012 9:56 am, edited 1 time in total.

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PostPosted: Mon Jun 18, 2012 7:50 am 
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Where is your 5 inch roll centre: front or rear? If the front it's pretty easy to get there even with big wheels. If the rear, then you're looking for about 3 inches at the front and I really struggled to get that with my bigger tires and had to go with LCAs that ran upwards from the chassis to the upright, which made getting camber gain in roll a lttle more difficult than if the LCAs had 'drooped'.

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PostPosted: Mon Jun 18, 2012 9:50 am 
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Here's an image of the bump steer concern. Not to scale. no exact measurements taken. Just a close enough for discussion sketch.
Attachment:
Arm offset03.jpg
Arm offset03.jpg [ 95.46 KiB | Viewed 647 times ]


OBTW does any one know the pivot to pivot measurement for a fox mustang rack?
I've read that a MII measures 24.5 and a MG 24.9 .
Warren Nethercote wrote:
Where is your 5 inch roll centre: front or rear? If the front it's pretty easy to get there even with big wheels. If the rear, then you're looking for about 3 inches at the front and I really struggled to get that with my bigger tires and had to go with LCAs that ran upwards from the chassis to the upright, which made getting camber gain in roll a lttle more difficult than if the LCAs had 'drooped'.




5" ground clearance, aprox front RC marked in red.
Attachment:
roll center marked in red.jpg
roll center marked in red.jpg [ 197.77 KiB | Viewed 647 times ]



I think that if a way can be found to use the ranger spindles, with an available rack, I can work out the rest.

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PostPosted: Mon Jun 18, 2012 11:58 am 
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Quote:
pivot to pivot measurement for a fox mustang rack?


I think it comes to 24.5"... There may be some variation in the aftermarket parts though, it seems I sometimes see 24". Early Pinto is 24.25"

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PostPosted: Mon Jun 18, 2012 5:35 pm 
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STRanger7

I know what bumpsteer is.

We aim for minimum bumpsteer with the wheels on parallel paths. The offset is not a factor. Look at the arc the tie rod attachment point follows throught eh range of suspension travel, then locate the pivot point for a fixed length tie rod. This provides the correct rack width, pivot to pivot and will ultimately determine which rack to use. With fabbed adjusters, you can use any rack so don't limit yourself to what will bolt together.

If you wish to address what may be happening with so many degrees of steering input, that's higher hanging fruit and more to do with ackermann than what we describe as bumpsteer.

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PostPosted: Tue Jun 19, 2012 8:42 am 
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Miatav8,MstrASE,A&P,F wrote:
STRanger7

I know what bumpsteer is.

We aim for minimum bumpsteer with the wheels on parallel paths. The offset is not a factor. Look at the arc the tie rod attachment point follows throught eh range of suspension travel, then locate the pivot point for a fixed length tie rod. This provides the correct rack width, pivot to pivot and will ultimately determine which rack to use. With fabbed adjusters, you can use any rack so don't limit yourself to what will bolt together.

If you wish to address what may be happening with so many degrees of steering input, that's higher hanging fruit and more to do with ackermann than what we describe as bumpsteer.


I think I need help checking my understanding on the two terms.

I've been thinking that Ackermann involves the kingpin axis, the mid point of the rear axle and the point where the steering arm attaches to the tie rod end.
Attachment:
Aprox Ackermann .jpg
Aprox Ackermann .jpg [ 60.41 KiB | Viewed 599 times ]


Attachment:
Kingpin Axis.jpg
Kingpin Axis.jpg [ 45.54 KiB | Viewed 599 times ]


Now if I understand what I've read about Bumpsteer, what is desired for min. BS is
to have the control arms and the the tie rod point to their I.C.
with the"ideal "tie rod length being measured from where a line connecting the steering arm end to the control arms I.C. intersects lines between top and bottom control arm brackets ,and the top and bottom points where the control arms attach to , in this case the "out-rigger assembly.

Attachment:
More BS.jpg
More BS.jpg [ 55.76 KiB | Viewed 599 times ]


I hope that I just failed to explain my concerns clearly, Because I really thought I had a handle on this at least. Having shared all that , I would not have posted in the first plac if I didn't want to learn.I am grateful for any help.


Ron

PS that is supposed to read "close enough for Jazz" :?, and 4 15/64"

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PostPosted: Tue Jun 19, 2012 11:32 am 
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STranger, as you know the instant centre for the control arms moves as the suspension moves through its vertical range, so while your steering rack virtual extension might point towards the IC at the nominal ride height, it may not once the suspension moves. Trace out the arc traveled by your "actual steering arm end" and then find the centre point of that arc. That is your ideal rack pivot point for zero bump steer with the wheels not turned.


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PostPosted: Tue Jun 19, 2012 12:02 pm 
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Posthumane wrote:
STranger, as you know the instant centre for the control arms moves as the suspension moves through its vertical range, so while your steering rack virtual extension might point towards the IC at the nominal ride height, it may not once the suspension moves. Trace out the arc traveled by your "actual steering arm end" and then find the centre point of that arc. That is your ideal rack pivot point for zero bump steer with the wheels not turned.


Okay, what i think I know is if you take a measurement from the ideal pivot point , to the Ideal rod end location, then go to the steering arm end and measure back toward the I.C that distance , you should have located where the actual pivot point needs to be located so that the tie rod will track with the control arms?

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PostPosted: Tue Jun 19, 2012 12:14 pm 
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Posthumane,

About, taking the ball joint up from the bottom... What if the taper coming up was run half way and a smaller cone shaped filler piece was used up top. then use an extension top with something like this.
Attachment:
IMG_0594.jpg
IMG_0594.jpg [ 101.44 KiB | Viewed 585 times ]

Found in this build log
http://locostusa.com/forums/viewtopic.php?f=35&t=13126

You can see were I stole the idea for the UCA. :wink:

Place the horz front or back then use the right wheel for desired scrub?

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PostPosted: Tue Jun 19, 2012 12:25 pm 
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STranger 7 wrote:
Posthumane,

About, taking the ball joint up from the bottom... What if the taper coming up was run half way and a smaller cone shaped filler piece was used up top. then use an extension top with something like this.


That's exactly what I was thinking, actually. That way you remove a much smaller amount of material from the LBJ attachment ear on the spindle. Another issue with having the LBJ come up from the bottom is clearance between the ball joint and the wheel, depending on your offset. I haven't measured yet how big of a wheel you would need.


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PostPosted: Tue Jun 19, 2012 12:28 pm 
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Why can't/don't you just do this ??


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