Measuring up per Ron Sutton. Check me on this Ron!!

[sccacuda]

Started measuring the front up and wanted to see if this is an okay way to go about it.

Ran the strings in front of and behind the tires and came up with the same distance between side to side. That will be the axle CL. Measuring the control arm pivots to the CL, I just loosened the bolts and backed them up a 1/16". My bolt to hole clearance is zero! Nothing moves when I tapped the bolt back. I just slipped a string around the bolt and tied a weight to each one so I can now measure to the centerline. I used the level, and marked it at the pivot string and one of the centerline strings and just added half the centerline distance. Good so far, or start again?!!


https://static1.pt-content.com/images/pt/2014/06/file_zps1f02eb62-1.jpg (http://s1060.photobucket.com/user/340cuda/media/file_zps1f02eb62.jpg.html)
https://static1.pt-content.com/images/pt/2014/06/file_zps658fa878-1.jpg (http://s1060.photobucket.com/user/340cuda/media/file_zps658fa878.jpg.html)
https://static1.pt-content.com/images/pt/2014/06/file_zps23c1ccc7-1.jpg (http://s1060.photobucket.com/user/340cuda/media/file_zps23c1ccc7.jpg.html)

[SSLance]

Craig, I'm not Ron...but having been there done that, I don't think that will get you your proper axle centerline. The amount of caster dialed in will move your mark forward. I believe I dropped a laser line straight from my spindle down for the axle centerline reference. I actually marked it on the ramp, rolled the car back, taped the string down to the ramp and rolled the car over the string again.

Also this goes without saying but be sure that you haven't jacked the front tires off the ground and lowered them again so they are in bind without slip plates under them.

Good start though. Do you have enough weight in the engine compartment to mimic the weight of the engine itself?

[Ron Sutton]

Started measuring the front up and wanted to see if this is an okay way to go about it.

Ran the strings in front of and behind the tires and came up with the same distance between side to side. That will be the axle CL. Measuring the control arm pivots to the CL, I just loosened the bolts and backed them up a 1/16". My bolt to hole clearance is zero! Nothing moves when I tapped the bolt back. I just slipped a string around the bolt and tied a weight to each one so I can now measure to the centerline. I used the level, and marked it at the pivot string and one of the centerline strings and just added half the centerline distance. Good so far, or start again?!!



It all looks good. Party on.

:cheers:

[Ron Sutton]

Craig, I'm not Ron...but having been there done that, I don't think that will get you your proper axle centerline. The amount of caster dialed in will move your mark forward. I believe I dropped a laser line straight from my spindle down for the axle centerline reference. I actually marked it on the ramp, rolled the car back, taped the string down to the ramp and rolled the car over the string again.

Also this goes without saying but be sure that you haven't jacked the front tires off the ground and lowered them again so they are in bind without slip plates under them.

Good start though. Do you have enough weight in the engine compartment to mimic the weight of the engine itself?

Hi Lance,

Craig's method will work fine. The center of the tire is in line with the center of the front spindle. Caster doesn't show up in the contact patch statically ... only dynamically when loaded.


Craig ... Lance asked about weight in the engine compartment. Since there is none, just want to make sure you're mocking all four corners of the car up at the desired ride height. I think we discussed this ... but I'm old & forgetful. :)

[sccacuda]

Craig, I'm not Ron...but having been there done that, I don't think that will get you your proper axle centerline. The amount of caster dialed in will move your mark forward. I believe I dropped a laser line straight from my spindle down for the axle centerline reference. I actually marked it on the ramp, rolled the car back, taped the string down to the ramp and rolled the car over the string again

Thanks Lance. My understanding is that if I have the other dimensions, pivots, ball joint, etc. That when modeled will show the caster side to side. This can be subtracted in the program to find the true CL. Your way is probably better for dialing in an existing suspension, but Ron is serving me the Taco Grande and designing new uppers, lowers, and spindles.



also this goes without saying but be sure that you haven't jacked the front tires off the ground and lowered them again so they are in bind without slip plates under them.

Good start though. Do you have enough weight in the engine compartment to mimic the weight of the engine itself?

I have the car at its ride height. That won't change. The height is adjustable, so once everything is together, i'll dial that height back in.
My numbers will be all over the place do to the upper adjustable arms not being adjusted or any sort of alignment. Ron really just needs the attaching points and track/tread width to do his magic. Everything else will be his design. I'm just hoping that I can keep the K frame without having to build a new one. Only the calcs will tell.

[SSLance]

Sweet, that sounds good. I like your string over the bolt technique, I'll certainly put that trick to use the next time.

[sccacuda]

Sweet, that sounds good. I like your string over the bolt technique, I'll certainly put that trick to use the next time.

I just set a level on a T stand about 1/16" off the strings where they intersect. That way I know i'm measuring in a straight line.


https://static1.pt-content.com/images/pt/2014/06/file_zpsb3d55620-1.jpg (http://s1060.photobucket.com/user/340cuda/media/file_zpsb3d55620.jpg.html)

https://static1.pt-content.com/images/pt/2014/06/file_zpseb3137a9-1.jpg (http://s1060.photobucket.com/user/340cuda/media/file_zpseb3137a9.jpg.html)

[SSLance]

Optical Illusion or is the trans tunnel that far to the pass side from the K-frame centerline?

https://static1.pt-content.com/images/pt/2014/06/file_zps23c1ccc7-1.jpg

[sccacuda]

Optical Illusion or is the trans tunnel that far to the pass side from the K-frame centerline?

Yep, Ma Mopar biased the entire driveline to the passenger side to accommodate a steering box. I have it centered in the car which is why it looks off. Just means more room on my side of the car!

[j-c-c]

Craig, I believe I read awhile back you designed/moved your suspension point based on some inputs from the Performance trends software. Since that is done, what is the objective of this measurement task, to verify?

How accurate does one need to be here? The reason I ask, is for instance in the fourth pic you posted, the string on the front left lower point is looped around the bolt, and it looks in the pic to be hanging slightly off center (easily corrected off course), but does this level of accuracy matter?

My thinking on a future similar job, was to use a self leveling laser pointer, and just grid it out on the floor.

Was using the tires as a reference for CL mainly for convenience and met the desired level of accuracy, because I would have thought a datum point on the chassis front and rear would be more repeatable for future measurements, etc?

Nice concrete motor BTW.

This I have said before, this is an awesome build.

[sccacuda]

Craig, I believe I read awhile back you designed/moved your suspension point based on some inputs from the Performance trends software. Since that is done, what is the objective of this measurement task, to verify?

That was using stock Corvette suspension pieces and just dialing in a bit more static camber, caster, and helping the camber curve. This is for a complete scratch build suspension: A-arms, spindles, and hubs. A suspension designed for this car.


how accurate does one need to be here? The reason I ask, is for instance in the fourth pic you posted, the string on the front left lower point is looped around the bolt, and it looks in the pic to be hanging slightly off center (easily corrected off course), but does this level of accuracy matter?

Very accurate. I just snapped a pic after I measured and bumped all the strings. Measured 3 times, pulling the weight each time to make sure it would repeat.


My thinking on a future similar job, was to use a self leveling laser pointer, and just grid it out on the floor.

Ron recommends that method as well.


Was using the tires as a reference for CL mainly for convenience and met the desired level of accuracy, because I would have thought a datum point on the chassis front and rear would be more repeatable for future measurements, etc?

Going to refer that question to Ron.

[Ron Sutton]

How accurate does one need to be here?
I want the numbers to be accurate to the 1/16" of an inch. Tighter if I can get it.

My thinking on a future similar job, was to use a self leveling laser pointer, and just grid it out on the floor.
This is a good way too. You just want to prevent from hitting the lasers, or you have to reset them up.

Was using the tires as a reference for CL mainly for convenience and met the desired level of accuracy, because I would have thought a datum point on the chassis front and rear would be more repeatable for future measurements, etc?

So many ways to skin the cat. Craig did it this way & asked if it is ok. it sure is, as long as the wheels are dead straight. Of course there are 5-6 other good ways too.