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Re: Front Steer Rack Conversion - Part Deux
[Re: Stanton]
#1579489
03/03/14 08:57 AM
03/03/14 08:57 AM
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Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
STEFF
OP
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OP
master
Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
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Quote:
Been asked before but not answered ... What lower ball joints will you be using to solve the ackerman issue? I had the opportunity to look closely at an assembled front end over the weekend and I don't think you can get the outer tierod end anywhere close to where it needs to be with stock spindles and rotors.
I've got a lower steering arm designed and in process. I've got a 3D model of it I can post later today.
67DartGT, your front end looks really good! 
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Re: Front Steer Rack Conversion - Part Deux
[Re: HardcoreB]
#1579495
03/04/14 08:26 AM
03/04/14 08:26 AM
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Joined: Jan 2003
Posts: 6,148
Melbourne , Australia
LA360
master
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master
Joined: Jan 2003
Posts: 6,148
Melbourne , Australia
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I'd like to know about the lower ball joints, a few people have used different types. I have seen some with bolt in units, but most have been screw in units (which I believe are B Body units???)
Alan Jones
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Re: Front Steer Rack Conversion - Part Deux
[Re: LA360]
#1579496
03/04/14 09:08 AM
03/04/14 09:08 AM
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Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
STEFF
OP
master
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OP
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Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
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Quote:
I'd like to know about the lower ball joints, a few people have used different types. I have seen some with bolt in units, but most have been screw in units (which I believe are B Body units???)
Screw in ball joint #K772......same as upper. It had the same stud dimensions as the stock b-body lower ball joint.
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Re: Front Steer Rack Conversion - Part Deux
[Re: STEFF]
#1579498
03/04/14 01:03 PM
03/04/14 01:03 PM
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Joined: Dec 2003
Posts: 22,697
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,697
Bitopia
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Since you seem to be open to varying opinions: 1. So whatever forces the balljoint inputs upward, they are resisted first by the flat section surrounding the balljoint, which will flex, to what degree I don't know, and the bending forces will be also resisted by the two 5/8"? attaching bolts in single shear that mount to the spindle, correct? Seems Like thickening/adding a web/etc around the balljoint would stiffen this area, reducing the bending load. 2. Is this billet or welded? 3. The steering arm web is IMO way over kill, the way I see it the arm mainly needs to transfer steering inputs, which I also think most grossly over estimate, and resist the twisting induced by the bump steer standoff correction. Your large/long web is not the ideal solution for those two scenarios. 4. It looks nice. 
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Front Steer Rack Conversion - Part Deux
[Re: Stanton]
#1579499
03/04/14 03:03 PM
03/04/14 03:03 PM
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Joined: Jan 2003
Posts: 10,013
Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,013
Frostbitefalls MN (Rocky&Bullw...
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Quote:
For proper ackerman, the tie rod end should fall on a line drawn from the center of the rear axle through the front lower ball joint. Looking at a front end with stock spindles and discs, this just isn't possible.
Also (correct me if I'm wrong here) the idler arm pivots and center link pivots should also fall on a line drawn from the center of the rear axle through the LCA pivot point.
If you have to compromise bump steer, toe out at top and bottom is prefered, bacause it doesn't over steer the car in a hard turn with body roll. That dictates at least the proper length tie rods, or slightly longer.
So with the front-mount rack, it would have to be wider at the inner tie rod ends than the LCA pivots - the actual width depending also on how far forward it is. Correct ?
I'm wondering if its possible to overcome the ackerman issue by moving the rack further forward.
Does anyone know of a book that has good info on front end design?
The lower control arm arc at the ball joint sets the length of the tie rods, which in turn set the width of the rack. Moving it forward or back will not help, only mess up the angle of the tie rods. Bump steer is more important than Ackerman, provided Ackereman doesn't get too far out of whack for what you want to do with the car. I have zero in my race car, would never go less than half needed for the street.
If you have to compromise bump steer at all, it is better to toe out at top and bottom of travel. that way the car won't over steer in a hard turn with body roll.
That would be a situation where the tie rods need to be longer than perfect, and the rack would have to be shorter than is best. It doesn't take much to screw the whole deal up. I spent many hours on my street dart, getting down to as little as 1/8 inch change in tie rod length and up/down location before it looked good to me.
Last edited by gregsdart; 03/04/14 03:12 PM.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Front Steer Rack Conversion - Part Deux
[Re: gregsdart]
#1579500
03/04/14 03:30 PM
03/04/14 03:30 PM
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Joined: Oct 2005
Posts: 8,902
Ontario, Canada
Stanton
Don't question me!
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Don't question me!
Joined: Oct 2005
Posts: 8,902
Ontario, Canada
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Quote:
The steering arm web is IMO way over kill
Good god, what are we talking, a couple ounces ?!?!? Hell, skip the fries at lunch !!!
As for the ackerman, zero is fine for straight line racing but the OP's application (as far as I know) and mine would be a street car and you do want some ackerman or you end up with significant scrub.
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Re: Front Steer Rack Conversion - Part Deux
[Re: Stanton]
#1579501
03/04/14 04:10 PM
03/04/14 04:10 PM
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Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
STEFF
OP
master
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OP
master
Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
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Quote:
Quote:
The steering arm web is IMO way over kill
Good god, what are we talking, a couple ounces ?!?!? Hell, skip the fries at lunch !!!
As for the ackerman, zero is fine for straight line racing but the OP's application (as far as I know) and mine would be a street car and you do want some ackerman or you end up with significant scrub.
As far as the ackerman discussion, from everything I read, if you get the outer tie rod intersect outside the balljoint, you will have ackerman. Maybe not the exact optimimum position, because of space limitations ie: the wheel, but you do the best you can. On a side note, My rack is out 8 1/2" in front of the wheel. The outer tie rod connection is 7" in front. My mind escapes me how far out the tie rod connect point is outside of the ball joint. I'll have to look at my notes. Also, using my test arms, I played around with the outer connect location, in and out, up and down and settled on a position that got bumpsteer to within .030" over 6" travel.
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Re: Front Steer Rack Conversion - Part Deux
[Re: STEFF]
#1579502
03/04/14 04:26 PM
03/04/14 04:26 PM
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Joined: Oct 2010
Posts: 28
Pennsylvania
TShell
member
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member
Joined: Oct 2010
Posts: 28
Pennsylvania
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Quote:
Quote:
Quote:
The steering arm web is IMO way over kill
Good god, what are we talking, a couple ounces ?!?!? Hell, skip the fries at lunch !!!
As for the ackerman, zero is fine for straight line racing but the OP's application (as far as I know) and mine would be a street car and you do want some ackerman or you end up with significant scrub.
As far as the ackerman discussion, from everything I read, if you get the outer tie rod intersect outside the balljoint, you will have ackerman. Maybe not the exact optimimum position, because of space limitations ie: the wheel, but you do the best you can. On a side note, My rack is out 8 1/2" in front of the wheel. The outer tie rod connection is 7" in front. My mind escapes me how far out the tie rod connect point is outside of the ball joint. I'll have to look at my notes. Also, using my test arms, I played around with the outer connect location, in and out, up and down and settled on a position that got bumpsteer to within .030" over 6" travel.
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Re: Front Steer Rack Conversion - Part Deux
[Re: Stanton]
#1579503
03/05/14 12:48 PM
03/05/14 12:48 PM
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Joined: Dec 2003
Posts: 22,697
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,697
Bitopia
|
Quote:
Quote:
The steering arm web is IMO way over kill
Good god, what are we talking, a couple ounces ?!?!? Hell, skip the fries at lunch !!!
As for the ackerman, zero is fine for straight line racing but the OP's application (as far as I know) and mine would be a street car and you do want some ackerman or you end up with significant scrub.
As much as I agree with the above on ackerman, defining the problem as "scrub" could be misleading, as scrub is more usually thought to be related to SAI type issues, although your point about lack of ackerman is still understood to be clearly negative.
And it doesn't take many fries to soon add up to a 1/4 pounder. 
http://en.wikipedia.org/wiki/Scrub_radius
Last edited by jcc; 03/05/14 12:50 PM.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Front Steer Rack Conversion - Part Deux
[Re: TShell]
#1579504
03/05/14 12:54 PM
03/05/14 12:54 PM
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Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
STEFF
OP
master
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OP
master
Joined: Jan 2003
Posts: 3,874
Smyrna, South Carolina
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Quote:
Quote:
Quote:
Quote:
The steering arm web is IMO way over kill
Good god, what are we talking, a couple ounces ?!?!? Hell, skip the fries at lunch !!!
As for the ackerman, zero is fine for straight line racing but the OP's application (as far as I know) and mine would be a street car and you do want some ackerman or you end up with significant scrub.
As far as the ackerman discussion, from everything I read, if you get the outer tie rod intersect outside the balljoint, you will have ackerman. Maybe not the exact optimimum position, because of space limitations ie: the wheel, but you do the best you can. On a side note, My rack is out 8 1/2" in front of the wheel. The outer tie rod connection is 7" in front. My mind escapes me how far out the tie rod connect point is outside of the ball joint. I'll have to look at my notes. Also, using my test arms, I played around with the outer connect location, in and out, up and down and settled on a position that got bumpsteer to within .030" over 6" travel.
Tshell, Tried to PM you back, but you have that feature set to not accept PM's.
But, Thanx for kind words!
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Re: Front Steer Rack Conversion - Part Deux
[Re: STEFF]
#1579505
03/05/14 01:07 PM
03/05/14 01:07 PM
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Joined: Oct 2007
Posts: 3,978
Hilltown Pa
1967dartgt
master
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master
Joined: Oct 2007
Posts: 3,978
Hilltown Pa
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Quote:
Quote:
Quote:
Quote:
Quote:
The steering arm web is IMO way over kill
Good god, what are we talking, a couple ounces ?!?!? Hell, skip the fries at lunch !!!
As for the ackerman, zero is fine for straight line racing but the OP's application (as far as I know) and mine would be a street car and you do want some ackerman or you end up with significant scrub.
As far as the ackerman discussion, from everything I read, if you get the outer tie rod intersect outside the balljoint, you will have ackerman. Maybe not the exact optimimum position, because of space limitations ie: the wheel, but you do the best you can. On a side note, My rack is out 8 1/2" in front of the wheel. The outer tie rod connection is 7" in front. My mind escapes me how far out the tie rod connect point is outside of the ball joint. I'll have to look at my notes. Also, using my test arms, I played around with the outer connect location, in and out, up and down and settled on a position that got bumpsteer to within .030" over 6" travel.
Tshell, Tried to PM you back, but you have that feature set to not accept PM's.
But, Thanx for kind words!
You can get him here toryshellehamer@yahoo.com
Brett Miller W9 cnc'd heads
STR Chassis fabraction
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