FrontEngineDragsters.Org Forum
Drag Racing Discussions => Front Engine Dragsters => Topic started by: AF/434 on January 26, 2015, 03:30:35 PM
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Hello folks I'm looking for someone who can help me figuring the correct ackerman for my first car with forward facing steering arms with a 2 inch leading king pin boss. I know how to do it with the arms facing rearward just not totaly sure facing the opposite way. Any help out there from you chassis builders???
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It works the same way no matter where the steering arms or king pins are. A straight line from the tie rod hole in the arm, through the center of the king pin should intersect with the centerline of the of the rear axle.
Roo
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I do it on my CAD program
I need the wheelbase each side, the front axle width @ kingpin centerline,and length of the arms. With that I can give you the offset for the hole the heim bolts thru
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I do it with a string line. As we are not turning corners at high speed that is more than close enough to get the wheels pointed right while steering around the pits. If you are steering a lot at high speed you have more problems than ackerman geometry. ;D
Roo
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It's more of a concern on street driven vehicles. You'll get some tire wear if you make a lot of tight turn offs, but your drag car will drive and handle just fine without it. Like Roo said, if you're steering the car that far at speed on the track you have bigger problems.
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It has a lot to do about tire wear and scrubbing at already soft compound. Is it aboulutly nessasary--NO, but if the guy wants to and is willing to do it correctly, then he should. Again, give me the parameters, and it takes me all of 5 minutes to get the offsets, Tell me what spindles, and I can also CNC machine them them
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Thanks guys for the input and Rooman that is how I was going to do it untill I started over thinking it.[LOL] dreracecar the car will be 250 inch wheelbase on the long side / 248 inches on the right looking forward sitting in the cockpit. The front kingpin width is 39 inches and at present I'm using 5 inch arms with the rack and pinion steering I plan to use and will probaly have you make me a pair once I get a little farther along.
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@ 5" its .390 offset, the 2" spindle offset was only a couple thou diff-- not that critical
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Thank you sir, will save me some time.
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Make the short side, on the side of the tracks you turn off to the most.
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99% of the cars built, the right side is short for engine torque, unless you race in Australia or New Zeland
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In all honesty and i will not name names.. is there any ill effects of shortening the left side and leaving the right side long?
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In all honesty and i will not name names.. is there any ill effects of shortening the left side and leaving the right side long?
If you were to get drive the same car on back to back runs with the offset swapped from side to side, I'm betting you'd never know if someone didn't tell you. If it was 2 feet instead of 2 inches, it might be a different story.
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With 1000's of cars being/have been built with the right side short, why would you feel the need to do it different?
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I know a car that was..and it was the first car that I saw that was built with the right side long. Car was plagued with aborted passes due to handling.
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We run our right side long.
Our track (LVMS) turns off to the left. So the car turns left much easier with the right side long.
It was that way with her (Kayla) Jr dragster. First thing we did when we got the Jr. was take advantage of the 0-2" of roll-out. Making the right side long. After the end of the year made a lot of changes to the car. One was making the left side long. She didn't like the way the car was harder to turn left. So I went back to having the right side long and she liked it much better.
So when we put her front engine car together we made the right side the side I could make long and all has been good.
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As Bruce noted earlier the reason for having the left side long is that torque will tend to lift the left wheel at the hit and thus having the right wheel trailing will blank the beam for a longer period of time. If you are running something like a J/D that does not carry the front end leaving then the difference is academic but for all others having the left lead is beneficial. As for the car turning left better with the right wheel leading, that sounds more like an ackerman issue as the location of the contact patch should not have any affect at slow turnout speeds. A lot of juniors have funky scrub radius geometry too and that will accentuate the problem.
Roo