Center of Gravity/Mass
Community Forums/General Help/Center of Gravity/Mass
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| Let's say you have a regular truck. Can you show me where the center of gravity would be on it? I've tried searching google to figure out where the average center of gravity would be on a regular vehicle but I never get any answers. Basically I just want to know whether it would be closer to the front or the back and how far down it should be. I need to know so I can actually set the Center of Mass setting in PhysX to something more appropriate. |
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| whether it would be closer to the front or the back and how far down it should be. Look at the weight distribution over each of the wheels, and them average them out to get the horizontal center. Where it ends up greatly depends on whether or not the truck is loaded. In an unloaded truck, the weight of the engine up front means that the center is much closer to the front axis than the rear. Obviously (?) the center of mass is *in between* the two axles, otherwise it would flip either forward or backwards. So unloaded: in between the axles, closest to the front. loaded: Depending on the weight, it gets closer and closer to the rear axle, but still in between both wheels. (Once you start getting above/beyond the rear axle, the front wheels of the truck would start to lift off the ground) Vertical center of gravity greatly depends on the truck. Some are much lower than others, and the higher the cargo weight capacity is rated for, the lower it is typically going to be to off-set the instability of the cargo. My *guess* is that the vertical center of gravity should be less than half the height of the truck, or it could get unstable when cornering or on uneven terrain... |
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| Towards the front. For height, around the driver's chest or lower (depending on the truck). |
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| the weight of the engine up front means that the center is much closer to the front axis Thanks, that makes it more clear to me. Everytime I tried looking on google for an answer all I pretty much got was.. Look at the weight distribution over each of the wheels, and them average them out to get the horizontal center. which gives me no idea of what it is supposed to look like because I am unable to get the "weight distribution". In PhysX though, the wheels don't have any settable mass and for some odd reason, when making a vehicle you have to set the center of gravity/mass yourself of the car. I don't understand why that isn't automatic. But thanks for the answer, it helps a lot. |
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| which gives me no idea of what it is supposed to look like because I am unable to get the "weight distribution". Average is probably right in between the two axles, or they wouldn't have spaced them the way they did. :-? |
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| It's not so easy to give a simple answer, since there's so myuch to consider. 1) Does it have a container/load? 2) If so, how does the weight of the container + load compare to the chassis & cab of the vehicle? 3)The Centre of mass is always going to be (assuming engineering accuracy and sensible loading) along the centre according to the X axis (X = left to right side) (Y = bottom to top) (Z = rear to front) The Y Axis will hopefulyl be as low as possible, this prevents the vehicle from flipping/tipping. (Fire trucks can tilt to more than 45degrees to one X-axis side, before tipping over duere to low centre of gravity!) The Z Axis, as xlsior mentions, ideally would be between the axels, to ensure fair distribution between the wheels. In the case of articulated lorries and vehicles with more than 2 sets of wheels, the wheel sets ought to be positioned according to the proportion of weight distribution between the chassis and the cargo. This is why you get the typical answer. []_[=======] O..O......O Neat drawing, huh? :) The front wheels are 1/4 the total length of the truck apart from the next set of wheels. There is a further 3 times this distamnce between the middle wheels and the rear wheels. This way, the wheels should support equal mass in case of full load. Therefore the centre of mass will be proportional distance from the middle. I don't use PhysX, so I can't comment on how it works, but without knowing the mass of the chassis and the cargo and 'combine' them with the wheels to make a single unit, there's no means to automatically calculate the centre of mass. In most cases, the centre of mass for Z axis is likely to be further towards the rear, but only slightly. If the front wheels and rear wheels are not equally spaced from the front and rear of the vehicle, you will have more slight variation, though unless this is a ridiculously large difference, this variation can pretty much be considered negligible. Hope that helps :) |
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| As stated before, it would depend on the truck and the cargo it's carrying. You could probably make a good generic guess though, and experiment a little. |
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