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Open Roads Forum  >  Travel Trailers

 > Hensley Arrow: How does it REALLY work?

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bettered

UpCountry SC

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Posted: 02/05/06 08:19pm Link  |  Print  |  Notify Moderator

Ron, you're too much. Logic trumps feel good opportunism once again.

I'm not going to take out my shear bolts to find out what happens, but then I remember cranking on those u-bolts. It would take an awful lot to make them slip. Like a TT in a 90 degree turn. Fortunately I've never owned a TV with a wheelbase short enough to get to the limit.

I'm still skeptical that SFDon actually got them that tight.


BetterEd

DW + 2 grandkids + Mini Schnauzer
2005 Chev 3500 Crew D/A 6.6L LLY, 6 x 6 DRW, 3.73
Tru-Flow + Banks, 2005 Flagstaff 831FKSS
Hensley + Prodigy

"Genius may have its limitations...." E. Hubbard 1856 - 1915

Ron Gratz

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Posted: 02/05/06 09:24pm Link  |  Print  |  Notify Moderator

Ed,

Don's post refers to a, "moderate slope with a 90 degree turn at the end". I do not take this to mean that he made a turn which resulted in the TT being at an angle of 90 degrees to the TV. I think it is likely that the maximum articulation during the "90 degree turn" was closer to 45 degrees than the 83 degrees which would be required to make the HA's linkage reach its limit of rotation.

Ron

Ron Gratz

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Posted: 03/03/06 08:55pm Link  |  Print  |  Notify Moderator

The following quotes come from the "Snow and TT" thread. Since Ed's comments pertain to how the HA works, I am responding here rather than hijack the other thread.

bettered wrote:

Ron Gratz wrote:

When a large truck passes a TT, the first interaction comes from the truck's bow wave. This results in a force which tends to pushes the rear of the TT away from the truck.

If a sway control "stiffens" the connection between TV and TT at the ball, the TV's rear tires and the TT's tires can work together to resist the push on the TT. If there is no "stiffening" of the connection, the TT's tires must provide all of the lateral resistance to the bow wave.

Ron

Interesting observation. With my hitch, I don't get that "initial" wave at all. Zip. The only push I feel is when the bow wave hits the front of my TV as the big guy passes me. Even then it's less of a blip when I'm towing than when I'm not. The whole rig seems more stable towing with the Hensley than not towing at all. Go figure.

Ed,

When a bow wave exerts a right-directed force on the rear of your TT, the TT responds by exerting a left-directed force on the TV. With a conventional hitch, the force is applied at the ball. The force will push the rear of the TV to the left and the relatively large resulting steering moment will cause the TV to yaw CW. It is primarily the yaw which is sensed by the driver.

With the HA, the lateral force from the TT is applied to the TV at a point closer to the TV's rear axle. The steering moment is considerably reduced and the yaw of the TV also is considerably reduced. The yaw might be reduced enough that the driver does not notice it.

As for the TV seeming to be more stable when towing, this could be due to the TT acting as a "yaw damper" for the TV. In order for the rear of the TV to be pushed to the right, the TT must undergo a CW yaw. The TT's yaw moment of inertia will resist the lateral push from the TV. This resistance will counter some of the bow wave force on the TV. Therefore, the response of the TV should be less when towing. At least, that's how I figure it.

Ron

Stressor

Whitefish Bay, Wisconsin

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Posted: 03/04/06 07:49am Link  |  Print  |  Notify Moderator

The lateral force is applied to the whole rig under those conditions, because the Hensley linkage is locked up tight, and with the exception of whatever play there is in the components, the rig is as stiff as a two inch steel bar can be stiff.

If you actually own a Hensley Arrow, you can demonstrate this to yourself on your next outing. Drive along and watch the rear end of your trailer for a while. Stop for a break, and while you are there, loosen the struts on the Hensley by a turn. Drive on, and watch the rear end of your trailer. You will see movement that was not there before.

In a locked linkage, there is no virtual pivot point. Steering input from the tow vehicle unlocks it, and as soon as things straighten out, it is locked again. The trailer cannot exert a yaw force in a Hensley equipped rig.

Check out the Hensley web site, they explain how the hitch "actually works" very clearly.




Milton Findley (and Kerene)

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sfdon

Novato CA 94947

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Posted: 03/04/06 09:40am Link  |  Print  |  Notify Moderator

We just finished our first road test of our new HA with trip from SF to Scottsdale AZ over the Grapevine and LA's 12 lane freeways. Early on the trip I had to brake hard and I felt a slight side thrust cause by a reaction of the TT. I tightened one of the struts a quarter turn and upped the setting on the brake controller slightly (6.2 to 7.2) and took the rig out for a test on a wide stretch of road. I accelerated up to 45 MPH and hit the brakes hard....no side thrust.

Trucks cause NO side sway, but I can feel the slightest reaction as large flat faced RV's pass by.

Based on this experience, I'm going ahead and list my dual cam setup on Craigslist.

Don


Don and Gail
2005 Forest River Surveyor SV-230
2003 Yukon with Autoride, Honda EU1000i
Hensley Arrow

bettered

UpCountry SC

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Posted: 03/05/06 05:32am Link  |  Print  |  Notify Moderator

bettered wrote:


Interesting observation. With my hitch, I don't get that "initial" wave at all. Zip. The only push I feel is when the bow wave hits the front of my TV as the big guy passes me. Even then it's less of a blip when I'm towing than when I'm not. The whole rig seems more stable towing with the Hensley than not towing at all. Go figure.

RonGratz wrote:

Ed,

When a bow wave exerts a right-directed force on the rear of your TT, the TT responds by exerting a left-directed force on the TV. With a conventional hitch, the force is applied at the ball. The force will push the rear of the TV to the left and the relatively large resulting steering moment will cause the TV to yaw CW. It is primarily the yaw which is sensed by the driver.

With the HA, the lateral force from the TT is applied to the TV at a point closer to the TV's rear axle. The steering moment is considerably reduced and the yaw of the TV also is considerably reduced. The yaw might be reduced enough that the driver does not notice it.

As for the TV seeming to be more stable when towing, this could be due to the TT acting as a "yaw damper" for the TV. In order for the rear of the TV to be pushed to the right, the TT must undergo a CW yaw. The TT's yaw moment of inertia will resist the lateral push from the TV. This resistance will counter some of the bow wave force on the TV. Therefore, the response of the TV should be less when towing. At least, that's how I figure it.

Ron


I completely agree.

bettered

UpCountry SC

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Posted: 03/05/06 05:39am Link  |  Print  |  Notify Moderator

Stressor wrote:

The lateral force is applied to the whole rig under those conditions, because the Hensley linkage is locked up tight, and with the exception of whatever play there is in the components, the rig is as stiff as a two inch steel bar can be stiff.

If you actually own a Hensley Arrow, you can demonstrate this to yourself on your next outing. Drive along and watch the rear end of your trailer for a while. Stop for a break, and while you are there, loosen the struts on the Hensley by a turn. Drive on, and watch the rear end of your trailer. You will see movement that was not there before.

In a locked linkage, there is no virtual pivot point. Steering input from the tow vehicle unlocks it, and as soon as things straighten out, it is locked again. The trailer cannot exert a yaw force in a Hensley equipped rig.

Check out the Hensley web site, they explain how the hitch "actually works" very clearly.



The links between the upper and lower components of the hitch are fixed in place about their axis of rotation by double tapered roller bearings (both top and bottom) in the hitch, entirely similar to the way wheels are mounted on axles.

If this system operates as you've suggested, why don't we have cars driving down the road suddenly "locking up" and skidding out of control to a panic stop. With millions of cars on the road, surely one of them would have experienced lockup by now.

markc4

Magnolia,Texas, USA

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Posted: 03/05/06 03:43pm Link  |  Print  |  Notify Moderator

Willald WHAT have you done???

I think the forum is gonna blow!!


94' E350 Chateau ClubWagon, 460 EFI, 4EOD, 4.10 Gears, aka "BIG RED"
05' Cardinal 31RKT, (36' OAL, 2 Slides, 10,300lb X 1560lb TW "Cat Scale")
20K Pullrite, Prodigy, 5K AirLift bags, Auto-Meter Pillar Pod (Tranny Temp & Tach)


Ron Gratz

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Posted: 03/20/06 06:25pm Link  |  Print  |  Notify Moderator

In another thread, Bryanl posted:

Bryanl wrote:

AFAIK there is no evidence of any sort that a Hensley is actually safer than any other properly installed and used trailer hitch.

Yes, I know. This one riles people something fierce. That's an interesting phenomena, too.

But the HA as inherently safer is sales hyperbole. Yes a bit better handling can enhance safety a bit. But an HA isn't going to help you make your rig stop on a dime or avoid rollover on evasive maneauver or prevent unexpected circumstance from happening.

It the safe and aware driver who properly handles his rig and maintains awareness of conditions that makes the difference.

Bryan,

The Hensley Arrow and the PullRite reduce the TT's ability to "steer" the TV by virtue of moving the point of application of lateral force closer to the TV's rear axle. Because there is less "steering moment" imposed on the TV, the driver does not have to make as large or as precise a steering correction to maintain yaw stability.

This means it is less likely that the driver will overcompensate with steering actions which will increase the yawing of the TV and TT. The overcompensation can lead to an unsafe condition. Therefore, if the HA and PR can reduce the potential for overcompensation, then the HA and PR can provide potential for increased safety.

Ron

robsouth

Metro-Atlanta, GA

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Posted: 03/20/06 07:01pm Link  |  Print  |  Notify Moderator

Seems to me that if I thought I needed a HA, I would be inclined to switch to a 5th wheel and be done with it. I cannot imagine paying the price of an HA. I have never needed one and don't expect to. JMHO.


"Sometimes I just sit and think. Sometimes I just sit." "Great minds like a think."

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