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Ackerman angle and steering questions

Jonesn

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Joined
Jun 20, 2012
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72
Location
Piner, KY
I'm messing around with building automotive style steering for a radio flyer wagon. Read up on Ackerman angle some and tried to incorporate it into my design. I'm still having issues of the inside knuckle wanting to go over center at full lock. I've messed with the offset distance from the kingpin and it didn't seem to make much difference.

I know this steering won't make much difference if it is off some, but I mainly want to learn how to fix it if I had to when scaled up.

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joho75287

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Joined
Aug 24, 2012
Messages
1,414
Location
Denison, TX
Maybe I'm being overly simplistic, but wouldn't steering stops on the "inside" wheel so you are limited how far that wheel will turn, solve your problem? I know I have them on my KP 60...
 

muddinmetal

Guntersville, AL
Joined
Jan 9, 2012
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6,395
Location
Guntersville, AL
It's a ****in' little red wagon... they all do it. the only way to avoid it would be a major redesign, but at some point it is still going to happen. Any time two parallel tires are tied together by a straight rod it will always happen to some degree
 

1993toy

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Joined
Aug 6, 2009
Messages
156
Try the locations in the pic.
 

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TBItoy

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Jul 2, 2010
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10,737
Location
Dodson Branch, TN
Re: Re: Ackerman angle and steering questions

1993toy said:
If you look at most, if not all vehicle steering; the tie rod points are offset outside of the pivot points.

Try the locations in the pic.
Most vehicles have the tie rod on the front....

You're missing the point of Ackerman
 

1993toy

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Joined
Aug 6, 2009
Messages
156
Re: Re: Ackerman angle and steering questions

TBItoy said:
Most vehicles have the tie rod on the front....

You're missing the point of Ackerman

Nope, I'm not...just trying to help him "improve" on his current setup.
 

TBItoy

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Dodson Branch, TN
Re: Re: Re: Ackerman angle and steering questions

1993toy said:
Nope, I'm not...just trying to help him "improve" on his current setup.
Putting the tie rod connections out where you drew them would make it have negative Ackerman and would make the tires scrub real bad when turning instead of tracking properly.
 

1993toy

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Aug 6, 2009
Messages
156
Re: Re: Re: Ackerman angle and steering questions

TBItoy said:
Putting the tie rod connections out where you drew them would make it have negative Ackerman and would make the tires scrub real bad when turning instead of tracking properly.

I agree, my suggestion will change the Ackerman angle. By the way, my suggestion is slightly exaggerated to how far they should move.

Changing the tie rod points will not affect the scrub, his steering axis is straight up, not angled.
 

TBItoy

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Joined
Jul 2, 2010
Messages
10,737
Location
Dodson Branch, TN
Re: Re: Re: Re: Ackerman angle and steering questions

1993toy said:
I agree, my suggestion will change the Ackerman angle. By the way, my suggestion is slightly exaggerated to how far they should move.

Changing the tie rod points will not affect the scrub, his steering axis is straight up, not angled.
Not scrub radius...

The whole point of Ackerman is that the left and right tires follow different arcs when turning. With positive (correct) Ackerman the tires will naturally turn/track better than no Ackerman or negative Ackerman.

If your outside tire turns tighter than your inside tire (negative Ackerman) then they are fighting each other and will scrub around the turn, rather than rolling smoothly
 

Beerj

Sonzabitches!
Joined
Dec 7, 2014
Messages
3,770
Location
Amish Country
He's definitely got positive Ackerman, maybe just too much. I do think moving the tie rod ends a little further outboard would help. Still has a way to go before hitting negative or even neutral.
 

TBItoy

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Jul 2, 2010
Messages
10,737
Location
Dodson Branch, TN
Re:

I don't understand what what he's saying about the knuckle going over center at full lock.

Even in the pics where the inside tire is turned to the frame, the steering isn't over center.
 

gottagofast

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Joined
Dec 11, 2015
Messages
1,064
His Ackerman angle is perfect in his drawing... Changing it at all would be a mistake... His entire problem is that his wheels are allowed to turn too far.... Hence steering stops.
 

mac5005

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Joined
Jun 25, 2012
Messages
340
Location
Rocky Mount, NC
Re: Re: Ackerman angle and steering questions

gottagofast said:
His Ackerman angle is perfect in his drawing... Changing it at all would be a mistake... His entire problem is that his wheels are allowed to turn too far.... Hence steering stops.
This x2
 

tallnate

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Joined
Oct 14, 2011
Messages
494
Location
Nashville TN
The geometry doesn't line up so it's definitely not perfect. The turn center should match a constant point throughout the turn. I think he needs to shorten his steering arms by roughly 20% and then lengthen his tie rod to match the new arm mounting position. Currently, it looks like his steering arms are close to 25% of the tie rod length. They need to be more around 18% of the tie rod length. Hypothetically if his tie rod is 25 inches, his steering arms should be 4.5 inches.
 

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