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# Ways to prevent a car from flipping over

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My car is nearly complete. I just have one last obstacle to go through: keeping it from flipping over while turning at high speeds. The physics engine is ODE and I've attached four cylinders to a box via Hinge-2 joint and added a little CFM to them. Here's a little illustration of my car flipping over. CFM isn't keeping my car from flipping over. Offsetting the car's center of gravity isn't keeping it from flipping over. Decreasing the speed of the car isn't keeping it from flipping over. I'm out of idea's. Please help. [Edited by - Drunken_Monkey on August 13, 2007 1:45:03 PM]

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Does your vehicle have enough mass (roughly 1200kg)?
Is your gravity set appropriately (default to 9.8 m/s/s)?
Is your vehicle traveling at a realistic speed (0-120 kph)?
Are your forces appropriate relative to the real world?
If you have all four wheels acting as bodies, are they turning at different rates?

Also, see ODE FAQ 12.9 and the Wiki.

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Well, this is something that ACTUALLY happens to cars. In real life, sports cars minimize this with a low profile, relatively wide wheel base, and surfaces that turn wind-resistance into downward force.

It would be easier to help if we knew specifics. What is the car's speed and what is the turn radius? What are the actual specs of the car? How are you accounting for gravity and wind-resistance?

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I've never used ODE, but the real-world physics behind it is dependent on the position of the center of mass with relation to the axis'[wheels of either side] around which it is flipping [and thus I'd assume the ODE-model will reflect this as well]. A tall car with a dozen bags of cement on top will flip over very easily[because the height and the cement bring the center of mass very high, which means a larger amount of the force involved in redirecting the car will be spent twisting the car around it's edge. As soon as the upward component of the force the wheels put back on the car's body exceeds gravity, the car flips, and the center of mass moves to an even more flip-prone position, accelerating the flip]. A short car with a low center of mass, by say a dozen of bags of cement set on the floor of the car will flip less easily.

Try attaching a single, very heavy particle on the bottom of your car, thus lowering the center of gravity significantly.

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Quote:
 Original post by DrigovasI've never used ODE, but the real-world physics behind it is dependent on the position of the center of mass with relation to the axis'[wheels of either side] around which it is flipping [and thus I'd assume the ODE-model will reflect this as well]. A tall car with a dozen bags of cement on top will flip over very easily[because the height and the cement bring the center of mass very high, which means a larger amount of the force involved in redirecting the car will be spent twisting the car around it's edge. As soon as the upward component of the force the wheels put back on the car's body exceeds gravity, the car flips, and the center of mass moves to an even more flip-prone position, accelerating the flip]. A short car with a low center of mass, by say a dozen of bags of cement set on the floor of the car will flip less easily.Try attaching a single, very heavy particle on the bottom of your car, thus lowering the center of gravity significantly.

If I do that, the car will move slower, so I'll have to increase the tire speed. If I increase the tire speed I'll be back at the square that got me into this mess.

Before I resort to adding more equipment to offset the center of gravity of the car, I want to try simply offsetting its center of gravity. If the car starts turning right when it's at a high enough speed, it will flip onto its left side and then onto its back. So to prevent that from happening, I'll set it's center of gravity to the side it's turning.

However, I'm going to need some trigonometry. If the car starts turning, I'll find the position of the car, find the current direction it's facing, add or subtract 45 degrees depending on the direction it's turning. Then I'll need some trig to find the edge of the car from the information I gathered. Can someone help me with that last step?

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If you have control over the center of gravity in ODE, then you can just drop *that* down, down to the bottom of the car, and your problem should be solved [adjusting the center of mass manually instead of implying a different center of mass by adding additional mass at a specific spot, which was the original suggestion]. I could likely help you with the math you're referring to, except I don't fully understand what you're asking [shifting the center of mass to the left or right depending on which direction the car is turning?]

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Quote:
 Original post by DrigovasIf you have control over the center of gravity in ODE, then you can just drop *that* down, down to the bottom of the car, and your problem should be solved [adjusting the center of mass manually instead of implying a different center of mass by adding additional mass at a specific spot, which was the original suggestion]. I could likely help you with the math you're referring to, except I don't fully understand what you're asking [shifting the center of mass to the left or right depending on which direction the car is turning?]

I already tried dropping the center of gravity, it doesn't help much.

If the car is turning right, I have to shift the center of gravity to the right to keep it from flipping. I need some trigonometric functions in order to do this.

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where did you place the center of mass when you adjusted it?

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Kind of like an anti roll bar does on a real car then?

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