Single & Dual Driven Axle Tandem Question

Discussion in 'Trucks [ Eighteen Wheelers ]' started by DBrass, Oct 1, 2014.

  1. magoo68

    magoo68 Road Train Member

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    The first anteaters and early volvos ran6x2 before air ride came out.. They were so bad in the mountains bc banned them because they kept spinning out unless you overloaded the live axle they had a way to transfer weight .. On flat ground with a dump valve on dead axle I suppose they would be better
     
  2. Richter

    Richter Road Train Member

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    on dry ground a 6x2 can pull a hill just as well as a 6x4 without any dumping of dead axle. In slippery surface, more surface area obviosly means less slipping. A 6x4 can be as little as 1 wheel drive in a slipery area and thus has no advantage over the 6x2. With power driver locked a 6x4 can be as little as 2 wheel drive. Rarely do you see a 6x4 wit locking diffs making it a true 4 wheel drive. That would be the best set up for off roading. Since almost all single axle trucks have a locking dif, they have similar hill climbing performance since a 6x4 with power divider locks has as little as 2 wheels driving (and you cant control which 2) With a 6x2 you have 2 wheels locked (with dif locks) so performance is ruffly the same or better. With the 6x4 you could have 2 wheel on the same side gripping which is likely to cause losee of control. Withe a 6x2 you have 2 wheeles on oposite sides gripping.

    Now like i said before, the 6x4 with PD Lock AND Dif lock is the best off road config, BUT the more common config is 6x4 with just a PD lock.
     
  3. Oscar the KW

    Oscar the KW Going Tarpless

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    What maintenance does a power divider require?
     
  4. OLDSKOOLERnWV

    OLDSKOOLERnWV Captain Redbeard

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    Years ago there was a system and I can't remember the name to save my life... Where a wide V-belt was used to link the dead axle to the live axle which gave benefits of a power divider, but also less weight. Anyone remember the name for it?? Got in early this morning from Syracuse and I'm brain dead for some reason.
     
  5. 12 ga

    12 ga THE VIEW FROM MY OFFICE

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    Call them tags, pushers or what ever you want they have been around since the 60's that I know of and they are a worthless piece of crap. That is personal experience with them speaking, not second had opinion.
     
    Aussie Tom Thanks this.
  6. Cat sdp

    Cat sdp . .

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    6x2 with super singles teaming on flatbed.....priceless .
     
    leftlanetruckin and MJ1657 Thank this.
  7. 25(2)+2

    25(2)+2 Trucker Forum STAFF Staff Member

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    Power dividers are more common to fail than the differentials, from long experience in a fleet of high milers.

    The best way to keep them working, other than specifying a higher ratio, (i.e. lower speed)is to be very careful to keep the tire assemblies on the different axles very close to the same circumference, by occasionally rotating wheels and tires like on a 4 wheeler. And replacing all 8 tires at once on a tandem drive axle with duals.

    I have just about 200k on a set of drives, and the front axle is slightly less worn than the rear axle, by actual tread measurement. I don't know if they(leasing company) are going to rotate them, I think they figure the trucks will be gone long before any trouble mechanically.


    The 6x2 is cheaper to purchase new, which should help sell them to the thrifty, but they aren't buying any of those, and they did have some full lockers that were sprung on steel. Obviously, no dump valve, so some things that are relatively easy, like sliding the 5th wheel, were more difficult. Those trucks were purchased to rent to outfits pulling lowboy trailers, and they are long since gone from here.


    In Pablo's defense, he was talking about tractors specified for use in Europe, and those are different, comparable to those closed car haulers you see with the long truck in the front pulling a trailer about equal size, comparable, but not the same.
     
    Exiled Thanks this.
  8. Trucki

    Trucki Light Load Member

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    I do have to say, on my International 9200, I only have Diff lock on one axle, my rear.

    So if I lock in both my Power Divider and my Diff Lock then I really only have 6x3
     
  9. Hammer166

    Hammer166 Crusty Information Officer

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    While you're right that both configurations give roughly equal absolute traction, rolling down the road there are still advantages to 6x4. Say it's taking 300 hp to go down the road in marginal conditions, each corner of the 6x4 needs to carry an 75 hp average load, whereas the 6x2 will load each side at 150 hp. Which one of those is closer the edge of the traction curve?

    Even if you completely dump the tag, you've only brought the 6x2 to equal footing (traction is roughly proportional to load,) but in the process have severely overloaded the drive tires, which have a load rating in the 22K# range. IIRC, from when Freightliner first pushed the 6x2 lightweight concept, the tag wasn't dumped when the diff lock was engaged, but only dropped it's pressure about 40% to avoid overloading the drive tires.

    There are advantages to the 6x2, but performance in marginal conditions isn't one of them.
     
  10. Richter

    Richter Road Train Member

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    except , you would never get 75 hp to each wheel if traction was an issue. You would end up with 300hp to one wheel in 6x2 or 6 x 4 if unlocked.