rack placement issues

[Marvel]

Hello!
Initially we decided on having a rear steer.This worked nicely on paper.Even the ackerman progression seemed to be fine.
The issue came during packaging.This made us to think of a front steer(tierod outer pivot point in the front of upright).
Since We don't have tire data,I understand that we cannot exactly determine the type of ackerman to be suited.But due to many factors we decided on going with 100%(or a little more) geometry.
The geometry goes well with rear steer.But doing some CAD programs i failed to make my inner wheel steer more than the outer wheel with front steer.
So,
How to get this with front steer?

[Marvel]

Hello!
Initially we decided on having a rear steer.This worked nicely on paper.Even the ackerman progression seemed to be fine.
The issue came during packaging.This made us to think of a front steer(tierod outer pivot point in the front of upright).
Since We don't have tire data,I understand that we cannot exactly determine the type of ackerman to be suited.But due to many factors we decided on going with 100%(or a little more) geometry.
The geometry goes well with rear steer.But doing some CAD programs i failed to make my inner wheel steer more than the outer wheel with front steer.
So,
How to get this with front steer?

[Claude Rouelle]

"Since We don't have tire data"

How do you want to solve an engineering problem without engineering input?

Guessing? That is not what FSAE design competition is about.

If I was a FSAE / FS competitor I would make it a priority to be part of the TTC. Getting tire data and using it properly is the best investment you can do to understand the "how", the "why" and the "how much" of any car suspension design and tuning.

[Z]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Marvel:
... doing some CAD programs i failed to make my inner wheel steer more than the outer wheel with front steer.
So,
How to get this with front steer? </div></BLOCKQUOTE>
Marvel,

1. Move the R&P backwards.

2. Tyre data is all but irrelevant here. It is a mouse, and you have an elephant in the room.

Anyone care to explain what that elephant is?

(Hint: Written above the entrance to Plato's Academy is... ?)

Z

[BMEP]

I'm going to guess you need to move your steering arm point farther out horizontally from vehicle centerline.
Make yo shit work first before you go about designing your desired/perfect geometry.

[Tallboy]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Z:


(Hint: Written above the entrance to Plato's Academy is... ?)

Z </div></BLOCKQUOTE>

That, good sir, is true gold. I appreciate your sense of humour.

[PatClarke]

And for those, who I am sure, have no idea what is being spoken about, the message Plato wrote was...

"Let no one ignorant of geometry enter here"

That might not be a bad rule for those who wish yo post on this forum? http://fsae.com/groupee_common/emoticons/icon_wink.gif

Pat

[Marvel]

Thanks all!
I have few questions(kick me if its silly)
1.Confused with the term "steering arm".
If I am not wrong,steering arm is just an extension of the upright(may be a bracket sort of..)for the tie-rod attachment.Is this true?
If yes,when we draw a geometry for 100% Ackerman, (the imaginary line that meets the center of rear axle); is this imaginary line an "extension of steering arm?" i.e. if the steering arm and upright bracket are same; this bracket has to be angled to get the line meet at rear axle center?
or "a line from the wheel center* to the center of rear axle passing through tie rod attachment on the upright?"
2.*is it wheel center or kingpin axis?