Side View Instant Centre

[kevin17]

Around what length and height would be the ideal side view instant centre?

[hughm]

http://lmgtfy.com/?q=how+to+use+search+function+in+a+forum

[Pat Clarke]

Kevin17,

What we have here is not a 'service on demand' website, but a self aid community.
It is considered very bad form to barge in here without introducing yourself and your team, and demanding information.
Information that others have worked hard on determining.

So, why don't you try again? And while you are at it, let us know what research you have done and what you have come up with?

Pat Clarke

[onemaniac]

If you believe someone else can tell you what YOUR IDEAL should be, it could be one of the following:
You're underestimating the complexity of automotive system or just so naive to imagine there is such thing as a perfect car for everyone for everything.

Why don't you specify what you want to achieve first AND what piece of information you're missing in order to come up with your own answer?
Everyone on this forum is often very helpful but you have to be a little more specific on your question to get a good answer back.

[Claude Rouelle]

Kevin17.

Pat reacted quicker than me but I will say it anyway. Who are you? Don't you think it would be courteous and simply polite to introduce yourself?

That being said, Onemaniac reply was also spot on.

[Kareem]

ideal!! .. there is no ideal.

If you think you can get a number and dig it into your design, then you are doing it wrong.

Try to post your thoughts and what you are missing and you 'll get help.

[MCoach]

Are we talking about the front or the rear suspension?

[Tim.Wright]

Use side view centres are short as possible (ideally zero) and ratchet bearings in the upright to convert otherwise wasted vertical energy into tractive force!

I can't believe no-one have thought of this before - educational system going down the S-bend blah blah...

[Kevin Hayward]

Tim,

In all fairness the ECU guys paid a fair bit of attention to the posts you are lambasting. A few crucial changes to suspension saw the accel time drop quite a bit between the UK and Oz comps last year. I don't believe the effect is as big as what was indicated is possible, merely because it happens too fast, but it is noticeable both visibly and by the stopwatch.

Kevin17,

It might be handy to make sure you can validate whatever decision you make once the car is running. Designing in some adjustment here might end up being a good idea.

Kev

[Claude Rouelle]

MCaoch question is important.

Maybe the side instant center of the front wheel should be at the infinite, but the infinite BEHIND the front wheel while the side instant center of the rear wheel should be at the infinite, but the infinite AHEAD of the rear wheel....

[Claude Rouelle]

Kevin,

You wrote "A few crucial changes to suspension saw the accel time drop quite a bit" My question is: a few changes in the suspension kinematics or in other suspension parameters such as spring and/or damper? I do not need to know what exact changes your team made but as this thread is about side instant center I presume you mean kinematics changes more than other changes but I want to be sure that is what you meant.

If it is the case I would not be surprised, even more for acceleration. My experience is that the kinematic design has a serious influence on car performance even more in transient than in steady state.

[Kevin Hayward]

Claude,

The original threat Tim is referencing included discussion about improving acceleration, some of the comments were on kinematics and spring/dampers. ECU ended up changing a few things, introducing a fair bit more anti-squat (for the acceleration event only) had a marked effect. The car already had some anti, but a lot more helped. The team also altered dampers, springs and a few other things. The guys learnt a lot by looking into drag racing and trying to replicate a lot of the techniques. Excuse me if I don't go into a lot of detail, it is not my work to share. But the trail starts with trying to keep as much load on the rear tyres for as long as possible in the launch phase. The right approach can see higher load than what is accounted for by static weight distribution and steady state longitudinal weight transfer. Kinematics is a key part of that.

Time in the UK was around 4.1 with a engine not near 100%. This was around the better combustion cars. Around 3.8 in Australia against a fairly nasty headwind. This was quite a bit ahead of the other combustion cars there. The goal for the team was to drop 0.2s from the UK event, largely spurred on by a lively discussion on this forum.

The main thrust of the conversation was that the competition had come to expect that 4.0s was about what a combustion car was going to achieve in acceleration. Hence teams were not banking on getting any meaningful points in the event. Despite the approach of the main antagonist alienating a few forum posters the main points were valid.

Interestingly the team was penalised in design for not having a enough adjustability in the suspension system. Won accel by around 0.2s, and with a completely different skidpad setup finish second in that event by a few thousandths. Went out of skidpad and acceleration with a 26 point lead in dynamics due mainly to being able to make the right adjustments in the event.

Kev

[Claude Rouelle]

Kevin

"...higher load than what is accounted for by static weight distribution and steady state longitudinal weight transfer. Kinematics is a key part of that"

Thank you Kevin. I do not need to know more about what exactly your team changed on their car.

This is just one more example of what I have experienced for many years about the importance of kinematics on transient performance and that I emphasize on in the OptimumG seminar, both for car longitudinal and lateral transient performances.