Re: RE: Part Time 4wd

From: fawcett@uism.bu.edu
Date: Thu Sep 24 1998 - 07:51:16 EDT


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     <<Okay, so I screwed up that last thing i wrote. I don't profess to
     be a master of 4wd vehicles, jsut what I thought was right.>>
     
     No problem Brian... That's the great thing about the DML, you learn
     something new every day... even things you didn't want to know:-)
     
     <<I wil disagree on the Mercedes part. I would rather have anything
     but the ABS system to be used as traction control. Do you really want
     to be on the brakes while going through mud, or any other off road
     terrain?>>
     
     I should have been more clear... The reason most 4x4 come with open
     differentials is because they are cheaper, easier to
     manufacture/assemble, better mannered on the highway, more durable and
     will get you through most off-road situations... The problem with open
     diffs is power going to the wheels takes the path of least resistance.
     So if you have one wheel up in the air or in some soft mud and the
     other one on solid ground -- the wheel up in the air or in the mud
     spins freely... The wheel that's on solid ground gets the same amount
     of power that it takes to spin the tire up in the air and, therefore,
     you be stuck!
     
     To counter this problem you can do a couple of things... You can get
     a LSD which uses clutches in the differential to distribute power more
     evenly or you can get some sort of locking device that that
     effectively binds the two wheels together so they get exactly the same
     amount of power... Both have there pros and cons and my point about
     the ABS system is that it is yet another technique that's been
     developed... From what I understand, the brake is applied
     (automatically) only to the wheel that is slipping which forces more
     power to be applied which in turn will provide more power to the wheel
     that's on solid ground and hopefully keep you going or get you moving
     again.
     
     What I like about the ABS technique is that most vehicles manufactured
     today come with ABS and it should therefore be cost effective to
     incorporate this system in production vehicles. Moreover, it seems
     like an easier system to maintain. I mean when the clutches in your
     limited slip wear out you got to rip the diff apart... With the ABS
     system what would you have to do? -- maybe turn the rotors and replace
     the pads? Anyway, I just thought it was a pretty trick solution to the
     problem.
     
     <<Momentum is the key here.>>
     
     Not necessarily... Unless you got ALOT of spare parts and perhaps a
     new body waiting at home you want to crawl through some areas I've
     been... Out west where these crazy dudes climb rocks and boulders
     with their rigs, I would think 1 MPH is too fast! In the mud or goo,
     yeah, keep it moving or you'll sink! -- Just make sure you checked
     for rocks and stumps first!! DOH!!!
     
     <<I don't like the independant rear suspension, either. It seems like
     they could have come up with a better idea...Such as the new Jeep
     Cherokee has - Quadra Track II.>>
     
     No doubt about it, Jeeps are great off-road vehicles but if the Quadra
     Track II uses open diffs your still back to square one.
     
     T.



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