Ackerman angle and steering questions

Toddy · Mar 30, 2016

Have no clue about the math but from the picture looks like at full lock all 3 points are in a line. This is causing the inside wheel to want to lock up. Not sure how to fix it but tie rod end on inside need to be out of the line towards the back.

John Galbreath Jr. · Mar 30, 2016

I was hoping the OP would continue to update his modeling with the suggestions. Kind of dissapointing!

Beerj · Mar 30, 2016

JohnG said:
I was hoping the OP would continue to update his modeling with the suggestions. Kind of dissapointing!

Lol, kidding

gottagofast · Mar 31, 2016

Toddy said:
Have no clue about the math but from the picture looks like at full lock all 3 points are in a line. This is causing the inside wheel to want to lock up. Not sure how to fix it but tie rod end on inside need to be out of the line towards the back.

Again, steering stops

Beerj · Mar 31, 2016

1tonyj said:
Paging patoyee!

Seriously, where is he? I thought his name was J.J. Ackerman. He's gonna be pissed that he missed out on this.

84mallcrawl · Mar 31, 2016

now this is some steering angle
http://s-media-cache-ak0.pinimg.com/736x/00/cb/11/00cb112cdf280c5533aefae7e061ba3a.jpg]http://s-media-cache-ak0.pinimg.com/736x/00/cb/11/00cb112cdf280c5533aefae7e061ba3a.jpg]http://s-media-cache-ak0.pinimg.com/736x/00/cb/11/00cb112cdf280c5533aefae7e061ba3a.jpg

gottagofast · Mar 31, 2016

With no Ackerman at all.......

FlatlandFSJ · Mar 31, 2016

Doesn't matter when you're that sideways all the time.. The drifters figured out HUGE steering angles for what they do and it works.

gottagofast · Mar 31, 2016

Yup correct Ackerman assumes the rear is tracking not just grinding tires into powder lol.

Jonesn · Mar 31, 2016

Sorry for the delay in replying. Actually had to do some work instead of designing the wagon.

Couple different design changes shown below. Seems that Ackerman is only good up to a point then the pivot point goes over center.

Moved tie rod closer to pivot point

Moved tie rod away from the pivot point. This is the only one that looks like it might help.

Moved the tie rod points closer together.

Moved the tie rod further apart.

TBItoy · Mar 31, 2016

Re:

On your original, first drawing, with theoretically correct Ackerman, why do you think the pivot is going "over center"?

Jonesn · Mar 31, 2016

Re: Re:

TBItoy said:
On your original, first drawing, with theoretically correct Ackerman, why do you think the pivot is going "over center"?

This is actually wagon #2 I've already built one of a similar design and at nearly full lock the tie rods hit a dead spot and makes it hard to turn it back to center. It isn't going fully over center but close enough that I lose all the leverage built into the arm.

With the original design the inside wheel is sitting at about 60 degrees and the outside wheel is about 45 degrees. My original wagon had two separate tie rods, that looking back now, are set up wrong. So I want to explore if there is any advantage to splitting the tie rods or not. I'm on vacation all next week so it will be a little bit before I can play around with it some more.

Mainly was wanting to use this as a learning experience for myself and thought others here may be interested as well.

The steering on the original wagon, that doesn't work well at all, and what spurred me on to look into the Ackerman stuff.

Eddyj · Apr 1, 2016

I would just like to say the fact that we are debating steering ackerman angles on a wagon is what makes this website awesome. Carry on.

tallnate · Apr 1, 2016

Re:

TBItoy said:
On your original, first drawing, with theoretically correct Ackerman, why do you think the pivot is going "over center"?

This is what I'd like to understand as well. The only thing that seems to make logical sense to me is that there's something wrong with the arc the steering arms follow throughout the turn. Maybe it's the narrow width and long wheelbase that's throwing it off.. don't know.

84mallcrawl · Apr 1, 2016

Eddyj said:
I would just like to say the fact that we are debating steering ackerman angles on a wagon is what makes this website awesome. Carry on.

skunk works for the next barbie jeep race

gottagofast · Apr 1, 2016

For the life of me I can't see why this is so hard to understand.... The track width and wheelbase are irrelevant because they are already factored into the VERY VERY VERY simple geometry... Kingpins to center of rear axle accounts for both automatically....

Once again the ONLY issue with the layout in the first pic is the lack of steering stops....

ANY normal tie rod steering system will fail to work correctly if turned that far...

Put stops in to push the inside wheel back out 5-10 degrees and ur done.

TBItoy · Apr 1, 2016

Re: Re: Ackerman angle and steering questions

gottagofast said:
For the life of me I can't see why this is so hard to understand.... The track width and wheelbase are irrelevant because they are already factored into the VERY VERY VERY simple geometry... Kingpins to center of rear axle accounts for both automatically....

Once again the ONLY issue with the layout in the first pic is the lack of steering stops....

ANY normal tie rod steering system will fail to work correctly if turned that far...

Put stops in to push the inside wheel back out 5-10 degrees and ur done.

Yep.