Hot Rods Help: Forward steering Ackerman issue.

With my current build (29 Model A Pickup), I had to go with forward steering. The steering arms were swap meet find and at some point, someone dropped them.
After flipping them, I had to heat and bend them closer to the rotors. But the issue I'm having now is, at full lock, left or right, the outside wheel has a greater turn than the inside.
This is the first time I'm used forward steering, so I wanted to ask if this is common?
New spindles, K-Pins, bearings, spacers, tie rod ends, axle is straight, etc.
Thanks for any input! Will post photos later tonight.
Watto

 

sounds like you need to adjust the drag link

 

The outside turning radius should be greater than the inside .

 

If the steering link is in in front of the axle the ball joints need to be further outboard than kingpin. You need a line from the ball joint through the kingpin to the centre of the rear axle

 

no pictures? how will we ever figure out what you have, without pictures?

Anyways...

 

Replace the words "tie rod end" everywhere he said "ball joint". Then look at Squirrel's diagram and you will see what needs to be done.

 

Whats already been said, plus, as a rough guide, to make this work the tie rod ends typically need to be perilously close to the brake disc. Need pics.

Chris

 

I could'n get a full photo from above, so spliced together.

 

Photos with out wheels and tires would be nice so we could see the steering arms also.

 

Overhead pic with no wheel and heading straight is whats required.

Chris

 

You will never get the correct "ackerman" with your setup.
You will just have to live with what you have.
When cornering one wheel will "push".
For the "ackerman" to be correct, the tie rod end would have to be on the other side of the rotor!

 

I came here to say this, too.

This can only be fixed one way. The right way.

 

Common? Yes. Common, and wrong.

This cannot be fixed the way you are going. You need deeper drop steering arms, and to put the tie rod behind the axle, where it belongs.

 

from the spindle face of a 37-40 spindle , where the indent is to receive the brake back plate bolt
the measurements are nice round numbers
the steering arm length is 5'' and it comes over 2''

its about that, so as to give you angle of 15 and 75 degrees
if the hypotensqueeze is about 7.3
so you can almost correct your own homework by
halving the king pin to king pin distance of 48
=24
and the wheel base being 112
its close enough at 12 and 78 degrees
BUT I bet they shot for nice round numbers originally
I would wager that IF you did the same for a 30 model spindle at
50.5 in half 25 and 104
its like 14 and 76

something like that

BUT when you then fit a 46'' king pin to king pin axle
and fit it to a 104 inch wheel base
its 12.5 and 77.5
i bet its supposed to be 78

 

Wattos 65…They way I read what I think your saying is it’s doing just as it’s supposed to. . . . . If your Ackerman is close…

When you turn to the left… the left tire/wheel will make a tighter circle than your right tire/wheel.

If you turn right…the right tire/wheel will make a tighter circle than your left tire/wheel.

I have needed to have the tie rod in front before and bent out the arms as close as I could to the rotors or backing plates. A stated above … a line drawn from each side should cross over the third member whether the tie rod is in front or behind the axle….

 

It's been identified that you need to move the tie rod ends out further. Study the diagram that Squirrel posted, and make your car to be as close to that as you can.

 

If you can't bend the steering arms outward for increased ackermann, then bend them upwards.
This increases ackermann due to kingpin inclination
This is also one of the reasons why "front steer" 4x4's have raised tie-rods.

 

This PFD uses The algebra formulas that I never got a grasp on back in school. On the other hand it actually explains Ackerman principle or "Davis" principle as it applies to rigs with the tie rod in front of the axle. IRJET-V6I4302.pdf

The gist of it from the drawing in this screen shot of the pfd is that your theorietic tringle is flipped and the center will be the distance of the wheel base out in front of the car.

Done correctly the wheels are not going to be turning at the same angle on a turn. they will carry an angle so that the outer wheel follows a perfect but larger circle that is centered on the circle the inner wheel takes that in turn is centered on the extended line from the rear axle where both lines from the front wheels intersect that line at the same spot.
If the Ackerman is off one of the front tires is going to try to push or drag the other one out of it's circle. If you have ever watched a front engine digger with an Angla front axle or Angela spindles and steering arms try to turn one tire is always dragging the other on turns and that is a true demonstration of Ackerman principle not being applied.

 

I also have front pointed steering arms on my Henry J (flat plate ones from Speedway). They are made with rear steer Ackerman built in so they were terrible as is. I left black marks on my driveway from tire scrub when backing out on my street. It drove fine in a straight line. I did what you did and it really helped. No more noticeable scrub in tight turns. I know it's not perfect, but it isn't going to affect how it drives in 95% of your driving.

Gary

 

I built this T back in 78, we got it as close as we could, and it drove great. You could notice a little scrub, on a tight turn in a parking lot. It was a Touring with a 104" WB.

 

Old British Fords have the tie-rods in front (Anglias and Prefects)

 

I have a couple. I don't think so.

Mike

 

Looks to me that your total ch***is is hand built. So you built it for the Tie Rod to be out front. Couple options, live with it the way it is or make some changes. Some choices just aren't as good as others. We learn by making mistakes much better than just being told it's not a good idea. Been there done that!

 

I’ve been through this before. It has to look like this or it won’t work at all.

I personally like the look but the arms need to be very close to the rotors. It has to hit these 3 points in a straight line.

center rear axle
Kingpin center
Tie rod

 

In my case, the tie rod ends interfered with my calipers when I went to bigger rotors. I've since made new caliper brackets that rotate the caliper up so they might clear now, but I don't see a reason to try it. Also, more ground clearance in the front.

Gary

 

This is the way it MUST be done!!!!

 

Rudolph Akerman discovered his principle in the 1700s on wagons. In order to turn either direction, the wheels need to move in 4 separate arcs. Because the rear axle wheels are not connected to each other they will find their own arcs and speeds. Modern differentials allow the same thing. Up front, the wheels are tied together through a tie rod, or in the case of an independent front end, a center link (drag link) and equal length tie rods joined to steering arms. Several posts have shown the angles needed for proper "toe-out" on turns. Steering arms MUST follow a line drawn from the centerline of the rear axle, projected the steering axis or king pin fulcrum. If the arms are behind the axle they must point in towards the rear axle centerline on the projected line drawn. If they are pointing forward, they must point out on the same projected line. If not, the outer tire and the inner tire cannot turn on the proper radius. I remember an argument with another front end man that Akerman didn't matter. We had access to a 65 Impala that had the arms facing forward but inward. I made a couple of tight circles and you could see the rubber that peeled off because the outer tire had a tighter turning radius that the inner tire. Foolish engineers trying to get the engine lower in the ch***is and and not extent the tread width outward to compensate for proper clearance for arms bent outward along that line, have caused unnecessary tire wear in the name of styling. Principles are fact not suggestions, or nice things to do if easy. Years ago, when I raced sprint cars, our steering arms were designed to have no Ackerman built in, but to point straight back instead. Years earlier, racers found out that if Ackerman was left in p***enger car steering arms adapted to race cars, that when the cars would corner and bounce around through the ruts, that is one front tire came off the ground that the car would dart in the direction of the wheel and tire still on the ground and just as soon as the other wheel and tire bounced off the ground, the car would dart in the direction of the tire on the ground. That created quite a handful on a rough track! I am sorry for the long winded explanation. So many people feel that if they set the toe to factory specs, Ackerman will be okay. Fact is that Ackerman is designed in an can't be adjusted. Only by bending the steering arms to comply with the Ackerman projected line can it be corrected, if there is room.