#851
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I cut some plates from 1/8" plate and drilled a few holes for plug welds and installed them on both outer faces of the frame rails tying all the parts together. I always do this when I modify a front end like this. It SHOULDN'T need the additional plates if the welds are full penetration welds but it keeps me feeling safe at 75MPH. I am not installing the plates on the inner faces yet because engine mounts look like they are going to be a very tight fit. I might have to scalp a "cove" in the sides of the frame rails. When I get to that point I'll do what I need to do then plate it up.
After a hell of a lot of measuring, checking dimensions, considering different options, etc. it is clear that I will need to narrow the CTS front suspension about 3 1/2". This is way too much to do by altering the control arms only. It would severely restrict driveability, and turn radius. No can do. So, what I'll do is take 1" from each control arms and 1 1/2" from the center. The first thing I need to do is send the arms out to my best guy. This is far beyond my welding capability. What I'm doing is welding up the bore that the ball joint is pressed into, then rebore 1" inboard and reinstall the ball joint. If you look closely at this picture you can see the center punch and a circle scribed around it. This will be the new location of the ball joints. Doing this will get me 2" overall. I still need another 1 1/2". If I went any further with the control arms I would lose turn radius. On a car with a long wheelbase like this one, you need every degree of turn that you can get. This is why I moved the new frame rails inboard 1" each compared to the CTS width. The only other sacrifice in doing this is that since I am changing the leverage of the control arm and suspension, I will get a slightly rougher ride but I am changing over to air bag suspension so that should offset the rougher ride. I cut the left side strut tower out of the CTS. I might be able to use it but I still haven't decided yet. I will need to make an upper frame rail from 1 5/8" round tube for stability and I might incorporate the CTS strut tower but it might be a cleaner installation if I just make a 1/8" plate that hits all the mounting bolt locations then use sheet metal to close it off. I'll decide on the fly. After sleeping on it, I have decided to delete the rest of this post covering alterations to the steering rack. I do not want to encourage anyone to do what I'm doing with this rack and pinion steering. Suffice it to say that I am narrowing my original unit and using it for reasons that are important to me. If this isn't done right, it can become a serious risk and I just don't want to make it sound like anyone can or should do what I'm doing.
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Jack Set a Goal So Big That You Can't Achieve It Until You Grow Into The Person That Can. Last edited by Jack 1957; 01-21-2021 at 01:36 AM. |
#852
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I started placing the rack housing to check for adjustments needed to eliminate bump steer. Bump steer is a condition that is a result of not having the swivel point of the inner tie rod on the same plane as the pivot points of the upper and lower control arms. What happens is as the suspension travels through its range, the toe will change. At rest the toe is adjusted with the tires aimed straight ahead. If you jack the car up, moving the suspension to its fully extended position, the toe will change. Not good.
On a typical unequal length control arm suspension this plane is defined by the front and rear upper control arm bushings and the front and rear lower control arm bushings. If you could attach the corners of a piece of paper to each of these 4 points, then install the steering rack, with the tie rods poking through the paper, the point at which the tie rod touches the piece of paper is where your inner tie rod swivel should be. If you have this right, all components are pivoting on the same plane and there will be no change in toe throughout its range of travel. There is a lot more to the geometry of a front suspension and steering system but the one thing that could really ruin your day is a bump steer problem. It's a BIG job to correct it once everything is welded up. This suspension is unusual. I don't think I've ever modified one like this. The height of the rack shaft is the same as the height of the control arm pivot points. In the picture below, you can see the bolts for the lower control arm. They are at the same height as the rack shaft. Usually the rack is above the control arm. This makes the job a little easier. This picture was taken from below looking upward. I set the rack in place and set up the laser facing upward in line with the pivot points of the control arms. You can see that the laser goes across the bolts and the center of the swivel on the inner tie rod. I'm very close. Not ready for welding yet but very close. I salvaged the top surfaces of the CTS shock towers because they are thick plate and rigid with a few strengthening bends added. I made some temporary tubes with screw adjusters to help position them and tacked them to the frame rails.
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Jack Set a Goal So Big That You Can't Achieve It Until You Grow Into The Person That Can. Last edited by Jack 1957; 02-26-2018 at 09:16 PM. |
#853
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Jack, I don't post in this thread much because I don't want to gush but dang Dude, this is a master class in how to build a street rod!
Well done! Everything is just well done!
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Kerry Pinkerton |
#854
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Thanks, Kerry. I'm doing this thread as a sort of repayment. When I was much younger, I was fortunate enough to have worked with a couple of masters. They showed me what to do, how to do it, and why. They didn't have to, they wanted to. I'll never forget their generosity and I hope I can at least light the fire for someone else.
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Jack Set a Goal So Big That You Can't Achieve It Until You Grow Into The Person That Can. |
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Quote:
I don't think anyone would blame you for gushing. Jack's and Marcus' threads are gush worthy. Thank you gentlemen J
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Insanity is defined as continuing the same activities while expecting different results |
#856
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Quote:
And also; once again you show a brilliant use of the laser, Cheers Charlie
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Why does dust stick to everything, but nothing sticks to dust? |
#857
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Jack
you are way over my head with much of what you do. But I enjoy reading and following your posts. master class work. Thanks for posting.
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Dave Bradbury |
#858
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The last alteration to complete the narrowing process is to take 1 1/2" out of the center. When I set the temporary upper shock towers, I brought each side inboard 1 3/4" for a total of 3 1/2". That covers the 1" per side taken from the control arms and 1 1/2" in the center. Rather than narrow the aluminum cradle I had enough room and material to extent the slots inboard where the lower control arms mount This will allow the lower control arms to move inboard 3/4" each to match the uppers. On the CTS, the castor and camber are set by moving the lower control arms in slotted holes. On a true strut car using a McPhearson style strut, these adjustments are made up at the top. The CTS has an upper control arm and a long coil over shock and a knuckle. The upper control arms are not adjustable.
I needed to make a rigid and more accurate fixture for the upper control arm mounting plates and get set up for welding them in. The first set of tubes was just to double check my numbers. Good enough for that but not for final location. I am going to use an upper strut bar going from the firewall forward just past the strut tower and down to the frame rail. The bar will tie the tower to the frame and body. I needed to hang the fender on the car again to see where the bar will go. I want it to run right along the inner lip of the fender.
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Jack Set a Goal So Big That You Can't Achieve It Until You Grow Into The Person That Can. Last edited by Jack 1957; 03-18-2018 at 10:26 PM. |
#859
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I got some 1 1/2" tube for the upper strut bars and had a friend put some 60 degree bends in for me. Typically, these would be 1 5/8" x .125 wall on a race car or a true strut car where the weight of the car is on the strut but I'll be using air bags on this car and the mount will be on the lower frame rail. This upper mount will only carry the upper control arm. I fabricated some brackets that will bolt to the firewall and cowl. The front of the bar will be welded to the frame and the strut plate. I still haven't gotten my lower control arms back from the machine shop yet. I'll be needing them soon.
The brake rotors were pretty badly rusted from setting in the impound lot for who knows how long. White vinegar and water mixed 2:1. Soak them 2 or 3 hours. (No scrubbing needed) Rust is gone, don't need to cut them. I sprayed them with WD40 since it will be a long time till they are going to be used. I'll clean the oil off with brake cleaner when the time comes.
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Jack Set a Goal So Big That You Can't Achieve It Until You Grow Into The Person That Can. Last edited by Jack 1957; 03-14-2018 at 12:12 AM. |
#860
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Jack, are you going to solidly mount the body to the chassis and make a unibody setup? Just wondering due to the strut going from the chassis to a plate on the firewall making the body a stressed member. Or are you rubber mounting one end of it?
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Marcus aka. Gojeep Victoria, Australia http://willyshotrod.com Invention is a combination of brains and materials. The more brains you use, the less materials you need. |
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