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slowmover · 12-14-2011, 08:20 AM

The TV Drive Axle is the Steer Axle of the trailer. The tendency of the trailer to want to move about on its own -- to pass the TV -- is greatly reduced when the proper hitch rigging is installed correctly. Side-to-side motion of the trailer can increase to trailer sway due to all sorts of concerns: trailer design, trailer load, winds, road surface, etc. To keep this at a minimum is the purpose of trailer anti-sway. The better the anti-sway, the less wasted motion in moving forward (less drag, cleaner aero).

The function of a WDH is to spread the 12-15% of TW across the TV, thus keeping handling/braking closer to the solo norm. The addition of anti-sway devices to the WDH keeps the trailer closer to center. Some hitches are designed around a particular concept to achieve this, some have add-ons. The first is a type, a VPP hitch, Virtual Pivot Projection where design linkages simulate a fifth wheel or gooseneck hitch, each of which mounts at or barely ahead of the TV Rear Axle:

GN

Fifth Wheel

(A high mpg example is Kamper Bob's rig: short OAL, lightweight & and decently aero. Another is Skyking's proposed aero conversion of an Avion 5'er TT to take advantage of close vehicle coupling. The trade-off of a 5'er is the loss of the truck bed & enclosure while towing beyond high wind load and COG concerns).

For trailers starting at about 8k, and especially above 12k, a GN or 5'er is pretty well required due to TW requirements.

A VPP Hitch replicates this advantageous arrangement of keeping the pivot point of the rig at the Drive Axle. The farther back from the RA is the pivot point, the potentially worse the handling problems that arise.

The TV Drive Axle is the Steer Axle of the trailer. The tendency of the trailer to want to move about on its own -- to pass the TV -- is greatly reduced. Side-to-side motion of the trailer can increase to trailer sway due to all sorts of concerns: trailer design, trailer load, winds, road surface, etc. To keep this at a minimum is the purpose of trailer anti-sway. The better the anti-sway, the less wasted motion in moving forward (less drag, cleaner aero).

In order of performance, thus preference, the best hitches are those which we might refer to as sway-eliminating:

1] Pullrite This mounts under the truck, and that center bar pivots from a mount point to have the trailer track true in all instances.

2] Pro Pride The improved, new patent Jim Hensley design. Allows a greater range of WD adjustment.

3] Hensley Arrow The original Jim Hensley design patent.

The second tier, again in order of performance, may be called sway-resisting:

4] Reese Strait-Line / Dual Cam

5] E-Qual-Izer (and similar designs by others; preferred for surge brake applications)

And finally, the doorstop known as a "friction device" anti-sway; to be avoided overall as one must disconnect in wet weather, etc, when most needed). This is what maybe 80-90% of folks think of when referring to a WDH (and their "understanding" that a 5'er is more stable) and the "poor performance" of a conventional "bumper pull" travel trailer.

In short, the less movement by the trailer under any circumstance, the less power needed by the TV to maintain headway being lane-centered in all conditions.

Towing is a risky business, and the likelihood of an accident per mile of travel is greater than with a solo vehicle. Thus the best hitch & rigging is neither expensive nor onerous to set up.

Next post: Incidental Concerns.

.

12-14-2011, 08:20 AM	#28 (permalink)
slowmover Banned Join Date: Oct 2009 Location: Fort Worth, Texas Posts: 2,442 2004 CTD - '04 DODGE RAM 2500 SLT Team Cummins 90 day: 19.36 mpg (US) Thanks: 1,422 Thanked 737 Times in 557 Posts	VPP Hitches The TV Drive Axle is the Steer Axle of the trailer. The tendency of the trailer to want to move about on its own -- to pass the TV -- is greatly reduced when the proper hitch rigging is installed correctly. Side-to-side motion of the trailer can increase to trailer sway due to all sorts of concerns: trailer design, trailer load, winds, road surface, etc. To keep this at a minimum is the purpose of trailer anti-sway. The better the anti-sway, the less wasted motion in moving forward (less drag, cleaner aero). The function of a WDH is to spread the 12-15% of TW across the TV, thus keeping handling/braking closer to the solo norm. The addition of anti-sway devices to the WDH keeps the trailer closer to center. Some hitches are designed around a particular concept to achieve this, some have add-ons. The first is a type, a VPP hitch, Virtual Pivot Projection where design linkages simulate a fifth wheel or gooseneck hitch, each of which mounts at or barely ahead of the TV Rear Axle: GN Fifth Wheel (A high mpg example is Kamper Bob's rig: short OAL, lightweight & and decently aero. Another is Skyking's proposed aero conversion of an Avion 5'er TT to take advantage of close vehicle coupling. The trade-off of a 5'er is the loss of the truck bed & enclosure while towing beyond high wind load and COG concerns). For trailers starting at about 8k, and especially above 12k, a GN or 5'er is pretty well required due to TW requirements. A VPP Hitch replicates this advantageous arrangement of keeping the pivot point of the rig at the Drive Axle. The farther back from the RA is the pivot point, the potentially worse the handling problems that arise. The TV Drive Axle is the Steer Axle of the trailer. The tendency of the trailer to want to move about on its own -- to pass the TV -- is greatly reduced. Side-to-side motion of the trailer can increase to trailer sway due to all sorts of concerns: trailer design, trailer load, winds, road surface, etc. To keep this at a minimum is the purpose of trailer anti-sway. The better the anti-sway, the less wasted motion in moving forward (less drag, cleaner aero). In order of performance, thus preference, the best hitches are those which we might refer to as sway-eliminating: 1] Pullrite This mounts under the truck, and that center bar pivots from a mount point to have the trailer track true in all instances. 2] Pro Pride The improved, new patent Jim Hensley design. Allows a greater range of WD adjustment. 3] Hensley Arrow The original Jim Hensley design patent. The second tier, again in order of performance, may be called sway-resisting: 4] Reese Strait-Line / Dual Cam 5] E-Qual-Izer (and similar designs by others; preferred for surge brake applications) And finally, the doorstop known as a "friction device" anti-sway; to be avoided overall as one must disconnect in wet weather, etc, when most needed). This is what maybe 80-90% of folks think of when referring to a WDH (and their "understanding" that a 5'er is more stable) and the "poor performance" of a conventional "bumper pull" travel trailer. In short, the less movement by the trailer under any circumstance, the less power needed by the TV to maintain headway being lane-centered in all conditions. Towing is a risky business, and the likelihood of an accident per mile of travel is greater than with a solo vehicle. Thus the best hitch & rigging is neither expensive nor onerous to set up. Next post: Incidental Concerns. .