Here are a few things out of a couple hours of reading I did lately
Dependent
On dependent systems with large displacements the camber angle becomes so severe on both tires and the tire contact patch on both tires so small that the benefit of claimed “more articulation” is greatly reduced or worthless. (see the picture of that cartoonish white Jeep thing with the front axle vertical and the tire sitting on its sidewall.) Also you have the front axle between the wheels so you really only have less than the radius of the wheel assembly as ground clearance.
Front dependent systems have high unsprung weight and they are susceptible to shimmy and steering vibrations.
“Shimmy of the front axle had become a serious problem by the 1920s. General Motors (GM) engineer Maurice Olley’s description of the problem
“On a smooth road with front wheels carefully balanced, the car might be traveling at 60 or 70 mph. Suddenly, for no apparent reason (perhaps a small dip or pothole passing under one front wheel), the steering wheel would be wrenched out of the driver’s hands, and would start oscillating violently, while each front wheel would leap along the road in giant ten foot jumps. The front axle would be tramping at 550–600 cpm [cycles per minute], each front wheel jumping three inches into the air.” (1)
“Olley and his colleagues at GM determined that a solution to the shimmy problem was the switch to the independent front suspension (IFS), which “suppresses shimmy by connecting the mountings of the two wheels through the entire sprung mass of the front of the car”. The IFS also had the advantage of allowing for softer front spring rates, which decreased how much the car would pitch over bumps — this flat ride proved pleasant.” (4)
I have personally seen this and had it happen to me in a solid front axle F-series.
Car and Driver refers to this as “…Ox-cart technology….” (5)
Independent
With an independent front or rear you can have zero camber angle change throughout the travel range, what ever range you choose to design to, and maintain full tire contact patch or you can design in the camber angle required for the job the vehicle has to do. You can also design in zero bump-steer as well.
Here are some of the benefits of the TAK-4 and TAK-4i independent suspensions used on our military vehicles.
“Equipping the TAK-4 suspension on HMMWVs provides numerous benefits, including:
–A 70 percent off-road profile capability and 14 inches of independent wheel travel to overcome obstacles and navigate rugged, mountainous environments
–Ground clearance increased to 17 inches to improve mobility and occupant visibility while also helping to counter underbody blasts, such as IEDs, by enabling more stand-off distance
–A 40 percent increase in the vehicle’s maximum speed and a 46 percent improvement in braking
–Restoring a 2,500-pound vehicle payload capacity when the crew is embarked with all current add-on armor installed, which allows for consideration of an under-vehicle armor vee-shaped panel solution to further improve survivability
–Improved ride quality, with a reduction in suspension vibration and harshness for less crew fatigue” (3)
“The new Oshkosh TAK-4i intelligent independent suspension system suspension provides 20-inches of wheel travel ..
TAK-4i intelligent independent suspension system suspension is an ‘intelligent’ independent suspension, providing variable ride height through gas springs.
“In all cases the operating profile of the system is 70% off-road, 30% on-road.” (2)
If the 4Runner had an independent rear suspension it would be a much better vehicle imho. Actually a BOF with 4 wheel independent from a major automotive manufacturer like Toyota would be pretty ‘effn awesome. SRS is not going to stop me from buying a 4Runnner.
The Sport of Rock Crawling amounts to micro percents of the 4 wheel drive vehicles used in the world. I doubt I will ever do it again. It was fun in a rented Jeep in Hawaii for a day. Here are some purpose built vehicles that have interesting articulation
Spider excavator
All Mountain Inc.- All Mountain Construction Spider Excavator Services
YouTube
Turbo diesel Hexapod Walking Machine
YouTube
Conclusion: I haven't seen anything in my reading to convince me that Solid Front Axle systems on a 4 wheel drive vehicle are anything I would want to have (again). This was almost a stupid waste of time since I knew this all ready however since I did get to read a 200+ page paper on vehicle suspension design it was probably worth my while. Thanks to everyone who replied.
1) W. Milliken and D. Milliken. Chassis Design: Principles and Analysis. Society of Automotive Engineers, Inc., 2002.
2)
Oshkosh TAK-4 Independent Suspension System - Wikipedia
3)
Oshkosh TAK-4 Independent Suspension System Enhances HMMWV Capabilities | DefenceTalk
4) Geometric Design of Independent Suspension Linkages D.E Kline
5)
https://www.caranddriver.com/news/a1...e-suspensions/