Hi Ryan,

I'll do my best to answer your question.

The Total Lateral Load Transfer (TLLT) from the Inside wheels to the Outside wheels is actually a very simple relationship = Car Mass x Lateral Acceleration x CG height above ground all divided by the Track width of the Car. Note that there is no dependence on springs, ARB's or Roll Centre height in this calculation. These factors come into play in determining how the TLLT is distributed between the front and rear axles.

Two factors determine how the TLLT is distributed, mechanical roll stiffness (springs and Anti Roll bars) and roll moment (height difference between sprung mass CG and roll centre). The roll moment is what is causes the chassis to roll and the mechanical roll stiffness resists it.

Looking at just mechanical roll stiffness the stiffer end of the car will get a greater percentage of the TLLT. The same principal applies to the roll centres. Raising the roll centre at one end of the car will stiffen that end of the car (roll moment is reduced) and that end of the car will receive an increased portion of weight transfer.

If we look at just weight transfer and ignore things like tire contact patch (very important) the stiffer end of the car will lose grip first. This is because the outside tire on that end of the car will be carrying the highest load of all the tires and will reach it's grip limit and begin to slide before the other three tires.

I find the best way to think about roll centres is to treat their effect similar to Anti-roll bars. The lower the roll centre the softer the chassis will be in roll, similar to using a softer ARB.

I'm not sure why the dynamic tab is displaying results opposite to what I have stated above. The same equations are used for both the handling tab and dynamic tab. The difference between them is the handling tab values are predicted using static values and on the dynamic tab the values are continually updated as the chassis rolls. On that basis I would expect to see the same weight transfer relationship but your observations don't support that.

The new version I am working on will have some improvements incorporated into the dynamic model which may resolve this difference. Either way I will be looking into it to find out why it is happening.

Hope that helps.

thanks Bob on your prompt reply

I am going to have to read that at least 10 times to understand it fully though

thanks again on a great program

The New Update has finally reached Beta Testing stage. My two week project at Christmas morphed into a 4 month major update. Will be available to all registered users for free download in a few weeks if all goes according to plan.

Short video highlighting new features
http://youtu.be/lYbNcBGHlu8?hd=1

bob did i miss how to add a a body somewhere along the line? gt8 stuff is not represented

In the Beta version Aero Calculator you just select the body style from the drop down list that is the closest match. In your case that would be a 190 or 200 Touring body shape. Next select the drag and lift levels and then enter the overall length, width and height of the body shape. Default values for the percentage of the rectangular area (LxW or WxH) is provided. You can use these values provided or change them to suit your needs.

The drag and lift coefficients can also be changed to whatever you like.

Just uploaded two new models to the website. Capricorn ARC R-10 2013 and TLR 22T.

Beta testing of the new version is almost complete. Expecting it to be released later this week. Registered users will receive the update by automatic download.

Any news on when the update will be ready?

I ran into a snag with the installer. It's a long complicated storey that I won't bore you with. Took me 4 days to solve but it is fixed now. That's why I am behind.

I just have to finish updating the Help files and then it should be good to go. Planning for this weekend. Fingers crossed.

Thanks for the answer. Love the software. Keep up the good work

I really love this software. Have got the demo and will be getting any day. Good videos too.

I have an unusual problem though. I am testing some ideas in weight distribution in an xray t4. Central motor possition and the whole car is 70mm wide.

I have found it make a huge difference to how the car handles.

Is there anyway to take this into account on rc crewchief?

I assume you mean the chassis width is 70mm and you have managed to fit all the components (motor, batteries ...) in that width. As long as the CG height has not increased as a result then this will definitely be a good thing. That will make the chassis respond faster to inputs as you should have reduced a property called mass moment of inertia. The easiest way to think of this property is spinning a rock on a string. Long string much more effort, short string easier. The centre of rotation being the CG of the car. So the closer you can place the components to the CG the less force is required to change their position. Placing heavier components close to the CG will have the most effect so mid motor will definitely help here.

To do a full dynamic simulation this property is needed in three directions, Pitch, Roll and Yaw. Now you are really talking now about a design tool not a setup tool. So while this could be done in RC Crew Chief it is not likely to happen due to the enormous effort required. The best tool for this job would be a 3D solid modeling tool like Pro Engineer or Autodesk Inventor. They are already set up to do this kind of work. Very expensive though.

That's what I thought unfortunately.

The car is 70mm wide inc components. Much narower wieght. Slightly longer though. I think the main difference is the torque of the motor as it accelerates acts much further forward and give much more drive to the front end.

I have already designed it, (mostly in solidworks) made it and have been running it for a few months.

My problem is that these changes in motor position and decreasing the width have had such a large effect that using rc crew chief will work but I have lost all comparisons to a normal setup.

I think the best thing is to get my base setup on the software then compare it to the numbers you would expect to see from a normal lay out.

This might help me to understand what effects the changes are having.

How would you upload or build a model for a particular car. Say a VBC Ghost. I see they have a VBC now, and the Ghost is similar. I would like to get this software, but not without knowing the car I have is on there.

Thanks

There is a video on the website that goes through how to measure and build a model. Takes a few hours with a pair of digital calipers. Good opportunity to go through you car and make sure nothing is bent, broken or impaled. I am available via email to help you through the process if you decide to give it a try.

Now for some exciting news. The update has finally been released.

The second time you open the program with an active internet connection you will be notified of the update.