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Old 08-22-2014, 04:49 PM   #1
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Hensley and ProGlide Questions

https://flic.kr/s/aHsk26K5nZ

I am considering one of these hitches for my next trailer. If one was to be hit, either being struck on the side of the trailer or TV, could the vehicles be flipped more easily since these hitches basically make the two vehicles one solid unit? Instead of just the trailer as in the attached pictures.
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Old 08-22-2014, 04:57 PM   #2
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The 2 hitches you are questioning a sufficiently alike that the hitch along would not make a difference.

Now will could the TV and trailer ever both be flipped in an accident? That question can not be answered with a simple yes or no. The dynamics of the accident would govern that and there is no way to predict those conditions.
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Old 08-22-2014, 05:10 PM   #3
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I probably didn't ask the question correctly. Certainly the dynamics of the accident will govern the end result. However, its apparent from my recent accident that even though my TV was broadsided the configuration of the Blue Ox hitch actually kept my Yukon from flipping. I wonder if the use of either of these hitches would have actually resulted in both vehicles being flipped.
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Old 08-22-2014, 05:17 PM   #4
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I do not know how you trust any answer you receive. But both of those hitches will not allow sway. As I recall you were hit in the trailer first so perhaps that hit or your quick correction would not have resulted in the trailer flaying out to the side. I doubt that you will ever know.
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Old 08-22-2014, 05:43 PM   #5
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Larry, you are correct. I am just trying to understand more of the physics involved with the Hemsley and the ProGlide. It would seem to me that since the if these hitches make the TV and TT perform as if they were one solid unit, an impact such as the one I received would be more likely to flip both vehicles. However, I would also think that there would be a tremendous peace of mid knowing that a sway situation was impossible.
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Old 08-22-2014, 05:51 PM   #6
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Pat..
Here is an offer...

If you want to tow with a ProPride, come on up to Round Rock and I will hook up our AS to my truck and let you try it..
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Old 08-22-2014, 06:08 PM   #7
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When I was towing the 2013 25FB International Serenity home from Los Angles to Phoenix with the 2007 Mercedes ML 320 CDI diesel with a Hensley hitch and car receiver modified by Can-Am in London, Ontario, I drove 55 mph. When I hit the Arizona border, the semi-trucks sped up from 65 to 80 mph. I could sense the bow wave as they came up, but the trailer did not move sideways. Note that the tires were the OEM GoodYear Marathon ST model inflated to 65 psi.

When we discovered the Mercedes numbers did not work out right when the trailer was loaded for camping, we acquired the 2012 Dodge 2500HD Cummins diesel. I never sensed any sway with the 25FB and the Hensley or the new 31' Classic with the ProPride when the big trucks blow by on the intrastate.

Immediately after both the 25FB and the Classic were in the storage unit from the selling dealership, the tires were converted to Michelin LTX (P) 235/75R15 XL tires on the 25FB using the factory aluminum wheels and Michelin LT225/75R16/E LTX M/S2 tires mounted on Aluminum SenDel T03-66655T wheels on the Classic. All the new tires were inflated to maximum side wall pressure.

Would the entire rig turn over in a similar incident to the OP, I am not sure. The 2" steel bar connecting the two vehicles will not function as a swivel hitch. However, both hitched do have some rotational movement as they each have a ball that goes into the trailer socket.
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Old 08-23-2014, 01:21 PM   #8
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Originally Posted by Pat Cassity View Post
[URL]--If one was to be hit, either being struck on the side of the trailer or TV, could the vehicles be flipped more easily since these hitches basically make the two vehicles one solid unit?--
Pat, I see no reason to think your TV could have been flipped more easily if you had been using a HA/PP hitch.
The HA/PP hitch does not make the two vehicles one solid unit -- basically or otherwise.
Just as a fifth-wheel trailer can pitch, roll, and yaw independently of its TV, a HA/PP-equipped trailer also can pitch, roll, and yaw independently of its TV.

The difference between a HA/PP and a conventional hitch is that, when the TV and TT are aligned straight ahead, the HA/PP's 4-bar linkage effectively "projects" the yaw-axis pivot point approximately 50" forward of the ball location.
The linkage only affects yaw-axis connectivity. The roll-axis and pitch-axis connectivity essentially remain the same as for a conventional hitch.

Furthermore, the forward projection of the yaw-axis pivot point changes rapidly as the yaw-axis articulation changes from zero (TV and TT aligned straight ahead).
At an articulation of about 5 degrees the forward projection of the "pivot point" is reduced to about 25", and as the articulation increases beyond 5 degrees, the "pivot point" quickly returns approximately to the location of the ball -- i.e. the HA/PP hitch then functions basically the same as a conventional hitch.

IMO, if you had been using a HA/PP hitch, the likelihood of your TV remaining upright would not have been decreased.

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Old 08-23-2014, 02:12 PM   #9
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Either way, I am of the opinion that your specific accident was a relatively rare type of accident among the relatively rare RV major accidents.

Can lightning strike twice? It can , but probably wont.

The odds say this will never happen to you ever again. Would your TV have rolled in the same accident with a PP/HA? Maybe, maybe not, but in all reality statistically it pretty much matters not for the future.

My take....
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Old 08-23-2014, 02:33 PM   #10
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Furthermore, the forward projection of the yaw-axis pivot point changes rapidly as the yaw-axis articulation changes from zero (TV and TT aligned straight ahead). At an articulation of about 5 degrees the forward projection of the "pivot point" is reduced to about 25", and as the articulation increases beyond 5 degrees, the "pivot point" quickly returns approximately to the location of the ball -- i.e. the HA/PP hitch then functions basically the same as a conventional hitch.
Ron...

I'm not trying to start anything - that statement made me curious. Is it possible/common to exceed that 5 degrees on a curve?

Thanks,
John
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Old 08-23-2014, 02:44 PM   #11
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I would say when driving at highway speed a curve that demanded more than a 5 degree differential between the truck and trailer would never happen in normal driving,,, no way.

I say not even close.
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Old 08-23-2014, 03:20 PM   #12
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One other quick question... Given that the main gain in preventing swaying with the HA/PP is by moving the pivot point forward, does it make sense to have the stinger as short as possible on a ball riding hitch? It has to be better, but is an inch or two enough to make a meaningful difference?
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Old 08-23-2014, 04:16 PM   #13
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I'm not trying to start anything - that statement made me curious. Is it possible/common to exceed that 5 degrees on a curve?
It depends on the speed. For a typical TV/TT combination, the circular path corresponding to a 5 degree articulation might have a radius of curvature on the order of 300'. That would tend to limit the speed to about 35 mph.

However, I was addressing the OP's question:
" If one was to be hit, either being struck on the side of the trailer or TV, could the vehicles be flipped more easily since these hitches basically make the two vehicles one solid unit? "

A side impact, either on the TV or TT, probably would result in a nearly instantaneous articulation of considerably more than 5 degrees.

Ron
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Old 08-23-2014, 04:32 PM   #14
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One other quick question... Given that the main gain in preventing swaying with the HA/PP is by moving the pivot point forward, does it make sense to have the stinger as short as possible on a ball riding hitch? It has to be better, but is an inch or two enough to make a meaningful difference?
On a typical TV with a HA/PP hitch, the ball might be about 75" behind the TV's rear axle.
With TV/TT aligned straight ahead, the virtual pivot point might be about 25" behind the rear axle. That means the lateral force transmitted to TV is converted to a "steering torque" (referenced to the rear axle) via a moment arm of about 25".

If the HA/PP's stinger is shortened by 1-2", the moment arm is reduced from about 25" to 23-24" -- giving about a 4-8% reduction in "steering torque".

Ron
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