Acherman with forward facing arms

[raposak]

I know how to measure and achieve it with rear facing arms, but where do you measure from if the arms are facing forward?

 

[r_chez_08]

You get a piece of string tied to the centre of the rear axle, and extend it through the kingpin and beyond. Basically, the centre of the tie rod bolt should lye somewhere along this line, whether forward or rear facing arms.
I did this on my kart and the steering is great!

 

[raposak]

hmm. I think that will be impossible since the rim would be in the way.

 

[r_chez_08]

Then have rear facing arms? The rim is very close on mine, so I made the arms really short.
edit:

If your arms face forward, do the string trick, but extend forwards. What you will end up with is steering arms that point slightly outward and forward instead of the "normal" inward and back that you're used to seeing.

 

[the-cyborg]

I use a drag link style setup on forward facing arms, works extremely well.

 

[raposak]

Well I guess I lucked out, I checked with the line to the center of the rear axle and they seem pretty good. Now I just have to figure out why it steers like crap.

 

[jamyers]

Have you looked at the caster? I found that moving the top of the kingpin to the rear of the bottom of the kingpin made a HUGE difference on my kart, even though I've got forward-facing arms (and the rims are way in the way).

 

[r97]

What exactly is the problem with your steering?

 

[raposak]

It's pretty much non existent. I'll have to jack it up and take a short video to better describe it.

 

[raposak]

Well i just jacked it up and went lock to lock. It appears that i have reverse ackerman. The outside wheel in the turn cuts a lot more than the inside wheel. Here is my Picasso lol

 

[jamyers]

That's pretty common with steering arms that point frontwards (sigh). From what I've gathered, the only way to get them turning correctly is to change the way the tie rods hook to the pitman arm (at the end of the steering column shaft). You'll want the rods to cross over / past each other and then connect to the pitman arm, usually the only way to do this is to have one bolt in top of the arm and the other on the bottom, with a wider pitman arm. The net effect you want (ackermann) is: More toe-out between the two front tires as you get to full steering lock. Here's a diagram of the crossed-rods (the vehicle front is downwards):

 

[raposak]

The only problem is that i'm running a steering rack and not a pitman arm.

 

[jamyers]

Oh. That would complicate things a bit...only thing I can think of is that maybe moving the rack forward or backward might help, but I'm only guessing.