Friday, Mar 12, 2004 at 15:04
Hi Goran, I think you hit it on the head when you say the bags are overinflated to compensate for the load. Either a heavy duty steel spring or an airbag will cause failure if a vehicle is so overloaded. Any vehicle that is overloaded, be it with heavy steel springs or airbags, will have potential chassis failure problems.
I must disagree with you though on 1 point. A
suspension upgrade (ie. steel spring) is not the only solution. I actually happen to be an engineer and there is no substantial difference between a heavy duty steel spring (say 300lb) and a standard duty steel spring (typical 150 lb) plus an airbag pumped up to an equivalent 150lb. This combines to a total of 300lb, the same as the heavy steel spring. As the load is still transferred to the same point, the vehicle does not know whether its an airbag or heavy spring.
Note there are differences in damping characteristics between an airbag and a steel spring, but that does not effect the example here, the spring compression rate is still the same.
Also a steel spring length can be altered to improve ground clearance for the same spring rate, thus there is more flexability to
tailor height/load characteristics (but no ability to change that height/load characteristic, unlike changing the pressure in an airbag)
If an airbag is used on a leaf sprung vehicle, it now transferres the load to a different point on the chassis and is a totally different case to coil springs (a leaf spring air bag is located approximately in the middle of the leaf, with the load transferred onto the chassis directly above). Thus the chassis design will come into play and there are potential problems.
As for airbags not suited for off-road, apart from the potential for puntures or snagged air lines, there is no substantial performance difference. In fact, an airbag has one advantage, as the "spring rate" can be fine tuned for the load at the time, or to maximise ground clearance (at the expense of articulation).
Cheers
Mark
PS apologies to Salmon for the thread divergence.
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