1969 Dart Street/Strip (Re)Build
Update for the day, got the center chunk out of the car to take in to the shop and get those whining gears taken care of. Hopefully they get it right this time.
Since I seemed to be having launching issues at the track, I was really curious to know what was going on with the suspension. What I had observed from the videos is that the front tires started to lift about an inch off the ground, but as soon as they did, the rear tires started spinning, the front dropped, and the 60' was killed. I didn't know if the tires were getting unloaded, if I had too much squat or anti-squat built in, too stiff of springs, etc. So I took some measurements last night, tried to get as best of a guess as to where the camshaft was located vertically to get the anti-squat line and here's what I came up with. I modeled it in CATIA to get a better visual to show what's going on.
This is how the car is currently set up. I thought that I had the top bars angled downward when I first set this up, but they aren't now. They are horizontal with the ground whereas the bottom bars are angled upward. Opposite of what I had intended. I wanted the bottom bars horizontal and the top bars angled downward. So anyhow, the current setup yields less than optimal results with the instance center about 220 inches forward from the rear, twice the wheelbase length! It's way out there, way off the anti-squat line.
Now if I raise the bottom bars to the next position up in the relocation boxes, I can get close to the anti-squat line (somewhere around 2 inches above the line) and the instance center is toward the front of the car. This could possibly be a good setup and will be the easiest change to make, but may tend to make the car want to wheelie more than if I had the instance center back further.
This is the more optimal setup. With the lower bars in the current position, I can get right on the anti-squat line IF I angle the top bars down 5 degrees from where they are now. This will get the instance center back a little further as well. The bad part about this is that the top bars are NOT adjustable. I will have to cut the mount for the top bars completely out, relocate, and weld it back into place. This is where a fully adjustable 4 link would come in handy.
So for now, I'm kinda hosed on getting an optimal instance center. I'm going to try moving the lower bars up and see how that goes. If that doesn't get it, it may be tear down time again.
Update for the day, got the center chunk out of the car to take in to the shop and get those whining gears taken care of. Hopefully they get it right this time.
Since I seemed to be having launching issues at the track, I was really curious to know what was going on with the suspension. What I had observed from the videos is that the front tires started to lift about an inch off the ground, but as soon as they did, the rear tires started spinning, the front dropped, and the 60' was killed. I didn't know if the tires were getting unloaded, if I had too much squat or anti-squat built in, too stiff of springs, etc. So I took some measurements last night, tried to get as best of a guess as to where the camshaft was located vertically to get the anti-squat line and here's what I came up with. I modeled it in CATIA to get a better visual to show what's going on.
This is how the car is currently set up. I thought that I had the top bars angled downward when I first set this up, but they aren't now. They are horizontal with the ground whereas the bottom bars are angled upward. Opposite of what I had intended. I wanted the bottom bars horizontal and the top bars angled downward. So anyhow, the current setup yields less than optimal results with the instance center about 220 inches forward from the rear, twice the wheelbase length! It's way out there, way off the anti-squat line.
Now if I raise the bottom bars to the next position up in the relocation boxes, I can get close to the anti-squat line (somewhere around 2 inches above the line) and the instance center is toward the front of the car. This could possibly be a good setup and will be the easiest change to make, but may tend to make the car want to wheelie more than if I had the instance center back further.
This is the more optimal setup. With the lower bars in the current position, I can get right on the anti-squat line IF I angle the top bars down 5 degrees from where they are now. This will get the instance center back a little further as well. The bad part about this is that the top bars are NOT adjustable. I will have to cut the mount for the top bars completely out, relocate, and weld it back into place. This is where a fully adjustable 4 link would come in handy.
So for now, I'm kinda hosed on getting an optimal instance center. I'm going to try moving the lower bars up and see how that goes. If that doesn't get it, it may be tear down time again.