How do I find out the proper location for the tie-rods?

[hemi43]

I'm trying to design my front end with little to no bump steer, but I'm confused about where my tie rod ends must line up. At the rack end it's fairly straight forward, the end must be inline with the upper and lower pivot points.
On the wheel end, It's impossible to lign them up, because the location will be determined by the ackermann.
I must be missing something !!

I don't know how to post a pic, but here's what I'm talking about
http://www.flickr.com/photos/dantechfab/3880063660/

[Engineer]

We had intensive discussion about this a while back.  It all depends on if you have access to CAD. 

Because the Ackerman has the outer joint "outside" the upper and lower mount locations, the inner joint should be "outside" the inner pivot points by roughly the same amount.

Are you drawing it up or just building as you go?

I will try to look up some old threads that address this.

[Engineer]

This thread talks about it some.


http://dtsfab.com/index/index.php?topic=161.75


Here is an illustration of finding the correct Inner mount point based on the Acherman adjusted outer tie rod location.

[hemi43]

Ok thanks !! I will read that thread so that we don't go into it again.

The only CAD I have access to is to draw parts for my CNC machine. It doesn't animate.
I plan on copying the geometry from the Barracuda, but all I have to go by is pictures. I have no dimensions.
My buggy will only be about 65-70% the size of the Barracuda.
I was going to draw the basic geometry first, and then try to fine tune the bump steer out of it while all the joints were just tacked.
Thanks for the advice. Dan

[fabr]

We don't mind answering ANY and ALL questions you may (will) have when reading through the stuff. Don't hesitata to ask!

[hemi43]

http://dtsfab.com/index/index.php?topic=161.75  was good reading, but it left me begging for more !! :-\
Dan

[fabr]

What/where specifically do you want to start? You ask the specific question and we'll come up with the answers. Give us a target to shoot for.

[Engineer]

Ok thanks !! I will read that thread so that we don't go into it again.

The only CAD I have access to is to draw parts for my CNC machine. It doesn't animate.
I plan on copying the geometry from the Barracuda, but all I have to go by is pictures. I have no dimensions.
My buggy will only be about 65-70% the size of the Barracuda.
I was going to draw the basic geometry first, and then try to fine tune the bump steer out of it while all the joints were just tacked.
Thanks for the advice. Dan

There are a few more good threads on the subject of front suspension on page 3 and 4.

By all means ask any questions that you come up with.  I just threw the thread out as a starting point.

I have never used any software that animates the parts, but by drawing them in an up, down and ride height position, you can get a good feeling for what the suspension will do as far as camber change through the travel, etc.

The Cuda is a sweet looking machine.  The plans are not that expensive, and may be worth the money just to get a starting point on the sizes needed for drivers compartment, engine compartment etc.

Tell us what your planning and I am sure you will get lots of ideas tossed at you to think about.

[hemi43]

Thanks guys;
This is my first buggy (go-kart) that will have any kind of real suspension, so therefore I'm very "green" to the geometry.
I thought about mocking up the front steering arms, then worry about the tie rod location at a layer date. I really like the pic Engineer posted with the 3 measuring points. It makes a lot of sense.

Is there a ratio as to how much shorter the top arm should be from the bottom?
I know there's probably a whole book written somewhere just on this, but I'm just looking for a rule of thumb.
I could make them parallel, and it wouldn't make any difference because this buggy might see 30 mph tops.
This is mostly a learning experience for me.
Thanks for the help. Dan

[BDKW1]

I have never used any software that animates the parts, but by drawing them in an up, down and ride height position, you can get a good feeling for what the suspension will do as far as camber change through the travel, etc.

Thats about the way I do it. Draw up the relevant points at full droop, ride height and full bump. I then draw radius's from the outer tie rod in all positions changing the length till I get a good intersection point for the inner pivot.

[fabr]

Unequal length a arms will induce camber change whereas equal AND parallel will not. For a buggy topping out at 30 I'd say keep it simple. Equal length and parallel unless you are racing it and need max quality of handling.

[hemi43]

Well I'm building this for my son, and he's 13. The 30MPH part is not what I'm concerned with !! I'm more concerned about this kart landing after he decides to jump over something. He assures me that he won't jump over stuff, but I know better.
 I built him a small "Jeep" go-kart when he was only 3, and was powered by a 5hp Briggs&Straton engine. He managed to get this thing airborne even though it had no suspension and weighed almost 300 LBS. There pics of it here >  www.dantechfabricating.com under the "mini jeep" link.
Dan

[Engineer]

When you do something you do it right!  I can't wait to see what you build. 

[hemi43]

Off subject, but you can see my car and my ugly mug on "Car Crazy" with Barry Meguier.
I just found out that they will be airing it monday night ( sept 7), as well as next Monday (sept 14)on Speed. The interview was taped this summer at a car show I attended, and I've eagerly waiting for it to come on. 
Dan

[fabr]

cool!