Turning angle for steering, how much?

I agree, I think the issue is cleared up. But now, I am curious. F&J makes a good point about wheelbase being a factor. My question centers around true or pure ackerman. Is a model a ford, or any stock car steering setup geometricly ackerman pure? Has anyone ever checked a 100% stock vehicle? I'm just curious, because ofcourse my car is not "perfect" in regards to ackerman angle. Obviously the Speedway kit is designed generically, but what about stock vehicles? Sorry, just trying to educate myself. I love this stuff. Conversation with true gear heads. I wish you guys were my neighbors! Crminal, you get that car done yet?.......

 

I have never read on where you can "run a line" to test the ackerman.

We know it goes through the tie rod ball centerline and to the center of the rear axle, but what part of the kingpin line?

The king pin is inclined, so would it be a line drawn through the contact patch under the tire at the exact center of the imaginary king pin line?

 

A line drawn from the center of the king pin, through the center of the tie rod (on the same side), if extended, should intersect the center of the rear end, where the axles would meet in the center (this being the center of a line drawn through the center of the wheels, 90 degrees to the center line of the vehicle). This is a hands on method to check the Ackerman angle. If not copacetic, get out the hot wrench, the super size Crescent wrench, and rectify.

 

Jeez, I wish ;~) I need to find another pitman arm since the decision to move the tie rod end to the inside rendered mine useless. It is a Chevy arm which I had machined with the taper to the outside. It fit the Ford splines perfectly.
Since this thread lives on, I have another question:
I centered the travel of the sector shaft, when I install the arm, it sits at about 7 O'clock, not straight down at 6 O'clock. At full right lock (arm forward) it does not quite hit 9 O'clock. Is this okay?

Thanks


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This is correct, but there is one more thing to remember. Both spindles must point to the same place on a line extended out from the rear axle. Obviously if you are traveling straight down the road this can't be true, but as you turn away from straight ahead, it should become true. Yes this might be splitting hairs, but this is truly what Ackerman effect is. I always try to double check by using 2 drywall squares and some chalkline. Turn the wheels just enough so that the spindle on the outside points just behind the inside tire

 

Well, strictly speaking the pitman arm should be at 90 degrees to the drag link. That would be ideal. But in reality, if the drag link is near horizontal, having it at the 6 o'clock position would be good. I sawed and filed the dead splines out of one recently to re-index it. It was actually easier than I expected.

You should be able to get the pitman arm taper redrilled half and half from both sides. half a taper is good enough if the nut is correctly tightened.

Mart.

 

Understand completely! Looks like I'm back on it. Appreciated


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This is a great thread! Question; to get more lefty turning radius, can he simply heat and bend his steering link? Any adverse affect other than the hockey stick aesthetic?

 

With a side steer car... The drag link actually has to move more to hit the stops turning full left, compared to link travel to hit the stop for full right.

That is caused by the Ackerman, and that the stops are on both wheels. We talked about one wheel turning into a turn tighter than the other, and that helps understand why the drag link has to move more (from dead straight) to hit the stop for a left turn.

It's due to the steering hoop arm attached to the spindle on that side. That left wheel with good Ackerman, turns sharper to the left, that it can when turing to the right.

This may cause one to wonder how can the right wheel can turn tigher into a full lock right turn? That wheel does get turned tighter than the left wheel, by the angle of the steering arms....which is related to "proper Ackerman" again.


So, back to the pitman arm angles, yes the arm should be 90 degrees at dead center, to the link. But, it will have a slightly different angle when at full left, compared to full right. Rarely happens, but if you have a box with very limited gear travel, and have the box gears centered at dead straight, you might end up with not being able to hit the full left turn stop, as left lock needs more link movement.

 

Looking right to me


(Until the next law of steering comes and bites me in the ass) ;~)

 

Great info being shared here. Not to highjack the thread but still a steering question. How many turns lock to lock of the steering wheel should you have? The car I'm building looks like it will have 4.5 turns. Is this okay or excessive?

 

looking at your photo,the tire rim in/offset looks like a lot /too much to even fit around a drum or disk and that will give you a screwed up reading of what hits what,maybe most of your prob.

 

I think I'm good with drum fitment :-/

Track width is 64" at the rear and 62" wide at the front. I'll set it up this way and if needed add 1/2 spacers at the front to increase turning radius if needed.
All opinions are good! Thanks

 

maybe 165 or even 145 tires?

You should weld Model A axle connections onto those 40 wishbones. especially if you're gonna put shock mount off the bottom.

 

From the last series of photos it it looking pretty good.

Mart.

 

What you talkin' bout Willis?
Model A axle connections?

 

Sorry, On a different note: When using 40 bones use the tube only weld Model A axle yokes off the Model A wishbone.

 

I would try it, as it is still a bit less that mid 50s stock pickups I believe.

But, I would think you will be busy at the wheel on parking lot/ driveway type tighter turns.....and one other thing is with that ratio, it should feel very light, like P/S. A huge steering wheel will make is even lighter with even less road feel.

Also a wider ratio like that will magnify any micro slop in the steering system parts.

You can mess with arm lengths to get a quicker ratio, but any change, seems to affect something else, like being able to clear the bones or whatever...or wrong angle on the link. Trial and error at this point.

 

Great info and pics.
I went out and took a few to get comments. I changed angle of the pitman arm to get 90* to the drag link which gave me full turn to turn.. I haven't checked what the ackerman angle is. I have stock '38Ply. steering link behind axle. Thank you,Dave

 

Saw this thread when I was looking for an answer to the same issues I was having, and switching the bones rear mount to the inside helped considerably , but another issue has me scratching my head,
My wheels/tires turn exactly the same amount in relationship to the frame, but the steering wheel turns 7/8ths of a turn to right stop from center, and 1-1/4 turns from center to left stop.
Same basic setup, 32 axle, 37 bones, 56 truck box/pitman arm.
Pitman arm is very close to 90 degrees to drag link at straight ahead position.
Is this normal?

 

Ralph, unhook the drag link and count total turns of the gear box then split it in half. You now know the true center of the gear box. If your drag link will not fit back on with the tires straight ahead and the gear box centered, you simply have a drag link length issue. If it does go back together with out turning either the tires or gear box, you have a linkage or steering stop problem.

 

Thanks, I'll give that a try

 

Another thing I learned after this thread concerning ackerman angles on stock vehicles as pointed out by someone else........the steering components on a regular cab short box truck are the same as on a extended cab long box. Manufacturers don't produce 100% pure ackerman angle vehicles.

 

Pete & Jake covered this in a lengthy article in the late '70s. Their RX was when you got the front and rear axles set, run a straight line (laser or string) from the king pin center past the spindle arm directly to the CENTER of the rear axle.
The reason I capitalized 'center' is that so many cars are built with 8" and 9" Ford rears, and pumpkin center is not axle center.

My experience has been that '37-'48 spindles have been VERY close, (1/4"+/-) with wheelbases ranging from 96" to 109".
My preference for doing it ONCE forces me to adjust this to 'zero', (dead nuts)
It is the final adjustment, after the tie rod clearance to wishbone is ascertained...in case that had to be tweaked. (rosebud tip and large adjustable {'crescent'} wrench.)

I enjoyed the thoroughness of this thread...intelligent questions and logical answers.
Over the years in my shop, I must have provided hundreds of hours illustrating fixes for these ills!
Mart was spot on with solutions. As were others. Kudos!

 

Ralph, I think post 39 answers your question.
It is normal.

 

I see said the blind man to his deaf mute friend.
My drag link was a little short, and after adjustments, they are closer to each other, but the left is still slightly more. Which seems to be the norm for this setup.
Next question, how much movement will I expect at the anchor point of the wish bone?
I know there are a dozen variables that affect this, but right now I have about 3/8 inch at the tightest point, but the upward slope of the 32 frame makes it an issue only in about one inch of frame rail. But for every inch of axle travel how much can I expect at the end of the bone?

 

Read up on AKERMAN ! You will need to maintain a straight line from your king pin center, thru your tie rod end to the center of your rear diff pinion center. when your wheels are straight ahead. if not it wont turn for beans cuz each wheel needs to follow a different radias. if they are the same it will scrub and push. Hope some of this mumbo jumbo makes sence. have fun !

 

Atwater said it right ...to the center of rear axle..pinion may not be on center.

 

Ralph, the movement at the centre of the wishbone ball will be a theoretical zero. If there are 36 inches between the ball and the axle, and the axle moves 3", then at 12" back from the axle the bone will move 2". At 24" back the bone will move 1". at 36" back (at the ball) the movement will be 0", or no vertical movement, just rotational.

This explains the principle, you will have to substitute the true dimensions and work it out for your own setup.

Mart.

 

No ball, noes are split, so tie rod ends, when I moved the mounting to the inside of the drop to clear tires it made my up down clearance a little tighter,
If it interferes the I will have to cut those off and put new longer drops on, of course if I do that I will move bones even further in and have no drag link or tire rub issues to speak of.