vehicle center of gravity

[mechengdude]

Hope this is the correct forum.

The question is specifically in regards to large trucks(class 8) and or large military vehicles.

assuming the generic wisdom is "high center of gravity bad" and "low center of gravity good", the following question is asked.

Are there any SAE specifications (or other) or rules of thumb? Such as CG of Vehicle Type XX shall be less than 1/2 the height" or does one need to determine what applicable specifications the vehicle is to meet in terms of grade and slope and do a free body diagram of when the vehicle will tip?

Thanks

 

[Tads3]

The UK MoD has mobility classes for various vehicle types which includes a minimum tilt angle for vehicle overturn. The info is publicly accessible via the Def Stan website here:

http://www.dstan.mod.uk/

(you need to register)

The Def Stan of interest is 23-06.

 

[IceStationZebra]

I think that you are talking two different animals with regards to the class 8 trucks and military vehicles. I know that Oshkosh Truck and the US military do test their large trucks on a tip table so there must be a target. With regards to the USA military it probably varies by the contract which will depend on which service it is for and the intended use.

With regards to class 8 trucks the trailer CG will generally be higher than the truck CG thus being the limiting factor. And if you are trailer-less the tractor's CG has got to be fairly low with that big 15L diesel, 18 speed transmission and heavy axles.

A little off topic, but I do know that off-road forklifts for the military have to be able to do a 360° turn on a 30% slope and go up & down a 40% slope. For civilian use the highest we did was up & down a 30% slope to simulate driving on a trailer.

ISZ

 

[patprimmer]

Even if you find a standard, it will be based on the compromise of increased ground clearance vs critical slope angle re roll over. One typically works against the other and the position of the compromise depends on the intended use.

Positioning of all heavy bits near the lowest point in the chassis obviously helps both, as does the use of lightweight materials higher in the chassis

Regards

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