-
Hey Guys,
First things first I trust everyone had a great Christmas and a good new year's celebration.
Now that we are getting back into it I just wanted to kick of 2014 by posting this tutorial on our online simulation,
http://www.chassissim.com/blog/chass...ssissim-online
When I was in Europe and the U.S I was getting a lot of questions about this and this is your best way of getting going with ChassisSim. If you want to get going follow the instructions in the video and drop me a line at info@chassissim.com and I'll set you up with some free simulations so you can take it for a spin.
Looking forward to a great 2014 and good luck for all your competitions this year.
All the Best
Danny Nowlan
Director
ChassisSim Technologies
-
Hey Guys,
Just following up from last week's video I've just posted this video about how to get a model going in ChassisSim Online,
http://www.chassissim.com/blog/chass...ssissim-online
I've posted it here because a really important principal in simulation is to start simple and get complicated later. Even though ChassisSim can go into fine detail you can start simple which is what I show you in this tutorial.
Anyway some good food for thought.
All the Best
Danny Nowlan
Director
ChassisSim Technologies
-
Hey Guys,
I've got a few things for you this week. Firstly I have a video of one of my customers in action in the Daytona 24 hour. It's a little showy but it's good fun anyway,
http://www.chassissim.com/blog/chass...ion-at-daytona
However on a more serious note I was informed this week of the passing of Bill Mitchell, the man behind the suspension geometry software WinGeo. One of the things that we don't do particularly well in motorsports is to acknowledge when distinguished engineering figures pass away. Bill was a giant. He has left many legacies but to me his biggest legacies was his work on Force Based Roll centres which I will always be in his debt for. It is definitely worth your while chasing down his SAE Paper on the subject. Here is the link -
http://papers.sae.org/2006-01-3617/
It's really good food for thought.
Enjoy
Danny Nowlan
Director
ChassisSim Technologies
-
Hey Guys,
I have a real treat for you this week. ChassisSim customer Maranello Motorsport won the Bathurst 12 hour on the 9th of February 2014. Here is the link with more details,
http://www.chassissim.com/blog/chass...thurst-12-hour
There is a link to a video for the last 12 minutes of the race. Enjoy it will have you on the edge of your seat.
On a more serious note though the race engineer of that car is my Australian Dealer. We had a really good debrief about what happened at the event and how ChassisSim was used. Stand by for some really good tutorials that will spin off from this. I'll get to these when I can I'm just hammered on a few projects right now.
Enjoy
Danny Nowlan
Director
ChassisSim Technologies
-
Hey Guys,
I just posted the latest episode of Dan's Vehicle Dynamics corner,
http://www.chassissim.com/blog/chass...ometers-part-2
It's a follow on from a tutorial I did on evaluating racecar stability using accelerometers. It has a correction to the first tutorial I did. However more importantly it contains a much improved technique that you'll get a lot out of. I also did a Racecar Engineering article about this as well.
Enjoy and have fun trying things out.
All the Best
Danny Nowlan
Director
ChassisSim Technologies
-
Hey Guys,
We have just released ChassisSim v3.24. The details can be found here,
http://www.chassissim.com/blog/chass...issim-tutorial
One of the things that we have done with this release is that we have enclosed a tool called the ChassisSim Tutorial. What it does is it takes you step by step through everything you need to do to get going with ChassisSim. It's designed to get you through the beginner hump.
Enjoy
Danny Nowlan
Director
ChassisSim Technologies
-
Hey Guys,
I've got a real treat for you today. Remember a couple of weeks a go I mentioned one of my customers, Maranello motorsport won the Bathurst 12 hour. Here is one of the tools they used,
http://www.chassissim.com/blog/chass...d-temperatures
This is a tutorial about determining hot tire pressures from a cold start condition using the ChassisSim track replay feature. You'll get a lot out of this.
Enjoy!
Danny Nowlan
Director
ChassisSim Technologies
-
Hey Guys,
I'm bringing up a link to an older post that I put up over 18 months ago. It's about how to create a tyre model from nothing using ChassisSim,
http://www.chassissim.com/blog/chass...-in-the-blanks
Over the last couple of weeks I've had a lot of questions about tyre modelling so this post is particular relevant. What you have in this post is a complete battle plan to how to do tyre modelling from race data so you have a tyre model you can use in anger.
Enjoy
Danny Nowlan
Director
ChassisSim Technologies
-
Danny,
I have been planning to buy your book - it's the next on my list now that I recently got Seger's 2nd Edition Data Aq book.
Jorge quotes you on a tire modeling technique and I have a question about the equation he lists. You may explain this better in your book (I couldn't find it in the first chapter preview) but I can't make sense of it as given.
~~~
To find a first approximation Fy vs Fz relationship from tire data, we use a 2nd order relationship (linear decrease in friction coefficient) that can be written as
Fy_max = a1*Fz^2+a2*Fz (called 'D' c.f. Pacejka '89 etc.) (1)
or you give it as
Fy_max = ka(1-kb*Fz)*Fz = (-ka*kb)*Fz^2+ka*Fz (2)
this form being convenient since
Lp = 1/(2*kb) -> kb = 1/(2*Lp) where Lp is the 'load at which the tire peaks' (3)
I follow this so far - does it seem correct?
~~~
In the book, it seems that the approximation is that Lp is approximately the maximum normal load on a tire after sufficient track data has been gathered. We can then directly solve for kb.
This is fair for some tires I think. Do I understand this correctly?
~~~
Here is where I am confused: the next section reads (pp 414-415):
"Equations 15.20 and 15.21 estimate the total lateral tire forces ... by applying a force equilibrium around the ... axles." [Italics mine]
The equation listed is:
Fn_LF + Fn_RF = ka * ( (1-kb*Fn_LF)*Fn_LF + (1-kb*Fn_RF)*Fn_RF ) (4)
First, this sentence (Seger's wording I suppose?) is odd because to my knowledge only moments are in equilibrium around anything - and I suppose this implies Static equilibrium too though not stated.
Anyway, I cannot come up with the above equation from a FBD or any train of thought thus far. I think it could be modified to include the relevant distances to the CG as follows (assuming a right-hand turn):
(Fn_LF - Fn_RF)*(t/2) = ka * ( (1-kb*Fn_LF)*Fn_LF + (1-kb*Fn_RF)*Fn_RF )*(h) (5)
Does this new formulation seem correct or was the original right? If so, what am I missing?
Sorry if this is not your concept - though you are quoted as being the source for the idea maybe you know what I miss?
notes:
a2 = initial coefficient of friction (1/1)
ka = 'initial coefficient of friction' (1/1)
a1 = load saturation parameter (<0) (1/N)
kb = 'drop off of coefficient with load' (>0) (1/N)
Fz = load on the tire (N)
Fn_LF = load on the left front (outside) tire (N)
Fn_RF = load on the right front (inside) tire (N)
t = trackwidth (m)
h = CG height above the ground (m)
Thank you!
-
Goost,
My friend this is an excellent question and my apologies for the late reply. I have been hammered on a lot of projects.
The key that you are missing here is when you do this force balance you do it based on the weight distribution of each axle. Consequently it should read something like this,
wdf*mt*ay = ka * ( (1-kb*Fn_LF)*Fn_LF + (1-kb*Fn_RF)*Fn_RF )
Where,
wdf = weight distribution at the front
mt = total mass of the vehicle in kg
ay = lateral acceleration in m/s^2
To fill in the blanks a bit the following will help,
http://www.chassissim.com/blog/chass...s-from-nothing
This takes up where Jorge left of. Also when you are ready to buy the dynamics of the race car shot me an email to info@chassissim.com
Also one other thing I'll say to you and anyone reading this. Jorge Segers is a good friend of mine and one of the most switched on data and race engineers I know. Pay very close attention to his data logging book. You would be crazy not to have it.
All the Best
Danny Nowlan
Director
ChassisSim Technologies
