rack n pinion front steer ackerman issues...explain...
My race car is a good example of the benefits(yep!) of zero ackerman as well as some problems.
I first tried to put a rack in a 65 Dart stock Kmember back in 1980. I had stock front suspension, and with a stock width rack from a pinto It turned out the inner to inner distance of the Pinto rack was WAY to wide for the early A front. I had a friend at work help narrow the rack seven inches, which is what it would take to make it work with the length of tie rod required to eliminate bump steer and still fit inside the drum brakes drums. I heated and bent the steering arms, had to notch the backing plates for the drums, got the bump steer out of it but the ackerman was zero and the turning radius was poor due to the stock arms being too long. So I cut and welded them, tested them for strength(they passed) and now I had more turning radius, but zero ackerman.
The car is a bear to push, and impossible to push in a turn without at least three or four helpers between the spool and the wrong ackerman. But for strictly drag strip use, it is tolerable and with the narrow front tires it doesn't have issues like you might think.
Now for the advantage of zero ackerman. In 1985 I got seriously out of shape at 135 mph, with the car about 30 degrees sideways or more. When I counter steered the car snapped back straight very quickly.
The reason is, in a slide at speed you WANT zero ackerman so the front end doesn't toe out when counter steering, and push the front end around , put the car into a spinout, and wreck your car in the process.
The same thing happened again at a bracket race where the car got sideways at half track ( lots more horsepower now!) to the point one guy said he could read the numbers on my side windows from the starting line. Again, it snapped right back like it was on rails when I counter steered. Third time, lost an oil filter gasket in the lights at 150 mph, same deal. Seriously sideways, got it back going straight easily, although my arse bit a chunk out of the seat!
I am slowly working on another rack conversion for a street car, and have found that a front steer rack that is narrowed five inches will work with stock steering upper and lower arms, but you will need disc brakes so the outer tie rod ends can be out where they need to be for proper ackerman. The narrow rack can be had from a drag chassis builder for about $217, I think it was Quartermax RJ race cars. If you go to the Early A section, I have a thread going about this conversion, just search my user name . The other issue I found is that with the rack narrowed five inches, it puts the steering shaft two and a half inches further in towards the center, and it has been a hassle trying to get a steering shaft snaked around the exhaust on the motor I plan on putting in my street dart. Check out the photos in that thread.
Here are a couple of photos of the race front end I built.
My race car is a good example of the benefits(yep!) of zero ackerman as well as some problems.
I first tried to put a rack in a 65 Dart stock Kmember back in 1980. I had stock front suspension, and with a stock width rack from a pinto It turned out the inner to inner distance of the Pinto rack was WAY to wide for the early A front. I had a friend at work help narrow the rack seven inches, which is what it would take to make it work with the length of tie rod required to eliminate bump steer and still fit inside the drum brakes drums. I heated and bent the steering arms, had to notch the backing plates for the drums, got the bump steer out of it but the ackerman was zero and the turning radius was poor due to the stock arms being too long. So I cut and welded them, tested them for strength(they passed) and now I had more turning radius, but zero ackerman.
The car is a bear to push, and impossible to push in a turn without at least three or four helpers between the spool and the wrong ackerman. But for strictly drag strip use, it is tolerable and with the narrow front tires it doesn't have issues like you might think.
Now for the advantage of zero ackerman. In 1985 I got seriously out of shape at 135 mph, with the car about 30 degrees sideways or more. When I counter steered the car snapped back straight very quickly.
The reason is, in a slide at speed you WANT zero ackerman so the front end doesn't toe out when counter steering, and push the front end around , put the car into a spinout, and wreck your car in the process.
The same thing happened again at a bracket race where the car got sideways at half track ( lots more horsepower now!) to the point one guy said he could read the numbers on my side windows from the starting line. Again, it snapped right back like it was on rails when I counter steered. Third time, lost an oil filter gasket in the lights at 150 mph, same deal. Seriously sideways, got it back going straight easily, although my arse bit a chunk out of the seat!
I am slowly working on another rack conversion for a street car, and have found that a front steer rack that is narrowed five inches will work with stock steering upper and lower arms, but you will need disc brakes so the outer tie rod ends can be out where they need to be for proper ackerman. The narrow rack can be had from a drag chassis builder for about $217, I think it was Quartermax RJ race cars. If you go to the Early A section, I have a thread going about this conversion, just search my user name . The other issue I found is that with the rack narrowed five inches, it puts the steering shaft two and a half inches further in towards the center, and it has been a hassle trying to get a steering shaft snaked around the exhaust on the motor I plan on putting in my street dart. Check out the photos in that thread.
Here are a couple of photos of the race front end I built.