Sway Control Hitch Not Needed

[Sean Woodruff]

Originally Posted by Adventure.AS

I think the OP was describing a situation when he was coasting up to a stop sign etc. without using the brakes or when going downhill and the transmission suddenly downshifted for engine braking and the tow vehicle would slow with using the trailer brakes, causing the pivot point trapezoid to become 'unlocked' from its normal configuration when under tension.

From what I have researched on this PPP type of hitch this hitch action would be similar to reversing into a campsite where the pivot point moves quite some distance to either side of the center line. I can see how this would be a lot different than a similar deceleration or coasting situation on a ball hitch where the force would remain on the center line of the rig (except of course on a curve.)

I stand to be corrected and would like to see an answer as to how this won't happen (and be dangerous) on a PPP hitch under the described deceleration conditions.

Let's be more clear here... there is no LOCK in the hitch. The hitch does not become "UNLOCKED."

There are forces applied TO the hitch.

The exact same forces are present regardless of hitch design.

Forces can be dangerous.

I know of no one who has ever been injured from the dangerous forces when using a Hensley designed hitch. Not one.

I do know of many who have been injured by the dangerous forces using a number of other hitches.

These are facts. You can choose to ignore them or hallucinate any number of scenarios in your head. I'm only stating the actual reality of 20+ years and talking to tens of thousands of customers and travel trailer owners.

That's about as bottom line as it gets. It really doesn't take more discussion.




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[Boxite]

Originally Posted by guskmg

Friction sway control is useless in rain, snow , or ice. The friction must be released in these conditions just when you need it for stability. Even fifth wheels and simi-trucks are unable to cope with these conditions safely.
guskmg

Would someone care to expand on that?

[Adventure.AS]

Originally Posted by Sean Woodruff

Let's be more clear here... there is no LOCK in the hitch. The hitch does not become "UNLOCKED."

Let's not quibble about semantics.

There are forces applied TO the hitch.

The exact same forces are present regardless of hitch design.

Forces can be dangerous.

I know of no one who has ever been injured from the dangerous forces when using a Hensley designed hitch. Not one.

I do know of many who have been injured by the dangerous forces using a number of other hitches.

These are facts. You can choose to ignore them or hallucinate any number of scenarios in your head. I'm only stating the actual reality of 20+ years and talking to tens of thousands of customers and travel trailer owners.

That's about as bottom line as it gets. It really doesn't take more discussion.

I will ignore your attempted deflection of my question by using sarcasm for now, but Sean, please clarify (as you keep avoiding the question) - will the PPP style of hitch pivot to an off center-line position (similar geometry to the diagram below) if the tow vehicle transmission suddenly downshifts or if coasting to a stop when the PPP hitch will loose its pivot point project when the hitch is NOT under tension - Yes or No?



Is it also correct that in the above scenario the pivot point will now be at the hitch head which is much further behind a normal ball hitch position and no longer projected to the tow vehicle rear axle - Yes or No?

[Sean Woodruff]

Originally Posted by Adventure.AS

I will ignore your attempted deflection of my question by using sarcasm for now, but Sean, please clarify (as you keep avoiding the question) - will the PPP style of hitch pivot to an off center-line position (similar geometry to the diagram below) if the tow vehicle transmission suddenly downshifts or if coasting to a stop when the PPP hitch will loose its pivot point project when the hitch is NOT under tension - Yes or No?

Attachment 282621

Is it also correct that in the above scenario the pivot point will now be at the hitch head which is much further behind a normal ball hitch position and no longer projected to the tow vehicle rear axle - Yes or No?

There is no attempt at sarcasm. There is also no deflection.

I explained exactly what happens when the forces are applied to the hitch.

If the force from the tow vehicle, pushing back toward the trailer, is applied to the hitch, the links will pivot AT THE HITCH. That's how the combination turns corners.

The deceleration of the tow vehicle has to be MUCH greater than the deceleration of the trailer to apply that force while moving down the road. A "sudden downshift" (your words) has never caused enough difference in deceleration to be dangerous in any instance in the history of the design.

You want to attribute it to a dangerous situation. If you are going to use words like dangerous, please point to examples of the "danger" causing any injury. I know of none and I'm pretty dialed into the history of the design.

If you want to deflect the fact that the forces are present with every hitch, and can be dangerous like I said in my previous post, then you must have an ax to grind.



P.S. - also not quibbling about semantics. Words have meanings, especially when written, and the proper words should be used. If you sat on my end of the phone answering questions about the imprecise words, which confuse people reading these posts in the future, you would understand my point. There is no lock in the hitch which can be unlocked in any scenario.

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[SailorSam205]

Originally Posted by Adventure.AS

I will ignore your attempted deflection of my question by using sarcasm for now, but Sean, please clarify (as you keep avoiding the question) - will the PPP style of hitch pivot to an off center-line position (similar geometry to the diagram below) if the tow vehicle transmission suddenly downshifts or if coasting to a stop when the PPP hitch will loose its pivot point project when the hitch is NOT under tension - Yes or No?

Attachment 282621

Is it also correct that in the above scenario the pivot point will now be at the hitch head which is much further behind a normal ball hitch position and no longer projected to the tow vehicle rear axle - Yes or No?

Your diagram shows the TV to be at a significantly different angle than the TT. My experience is, yes the parallelogram setup shifts a bit, I'm guessing less than 2 inches. The center line of the TT and the TV remain parallel, not turned. At the minimal offset of the two center-lines. IF the TT was to in fact be "pushing" the TV with excessive force (please explain how this could happen) it would be pushing straight ahead. My bet is the ONLY way this situation occurs is when the TT brakes fail completely and you are making an emergency stop.

As stated, the "bump" may occur if the TT brakes are applied with significantly lower pressure than the TV brakes - causing the TV to do most of the stopping. This may startle someone new, but is not a significantly larger issue than a conventional trailer with the same mal-adjusted brakes. And the conventional hitch has the additional risk of the TT pivoting on the ball and spinning the whole rig.

Also, please explain why you thing that in this deceleration scenario, the pivot point projection is not occurring. The trailer is still rigidly controlled by the hitch. Where did the pivot point move to?

To the OP, the answer to your question "what was the cause, and what were the circumstances and data (loading, speed, weights, etc)." Two main factors cause sway - speed and tongue weight. Recommendations for tongue weight are generally 10-15% of TT actual weight. At the bottom end of the range and below - you are starting to ask for trouble. The faster you go, the more energy any sway issue that occurs grows. The air pressure push from a passing semi or cross winds can initiate the sway. Recognize that sway is a pivot of the TT on the TT axles. The best "unbiased" discussion of the issue I've found was written by an engineering grad student at the University of Bath in the UK. His dissertation on " Trailer Snaking" is published on the web.

[Adventure.AS]

Originally Posted by SailorSam205

Also, please explain why you thing that in this deceleration scenario, the pivot point projection is not occurring. The trailer is still rigidly controlled by the hitch. Where did the pivot point move to?

Please refer to the post from Sean, above, in which he agrees that the pivot point moves from the TV axle to the hitch head which is well behind the bumper, when the tension is taken away from the system.

[xrvr]

Originally Posted by Boxite

Would someone care to expand on that?

Sway control can keep the trailer from returning to directly behind the tv when in very slippery conditions. This can occur with separate sway devices or WD hitches with sc built in. Not mentioned much anymore, but on some WD,sc hitches the manuals used to mentioning loosening up the sc in the rain. Friction sc works by not allowing the trailer to move side to side as much as it might. If the trailer is not directly behind the tv or at an angle the sc may hinder it from returning to verticle causing a problem with stability.

[SailorSam205]

Originally Posted by Sean Woodruff

If the force from the tow vehicle, pushing back toward the trailer, is applied to the hitch, the links will pivot AT THE HITCH. That's how the combination turns corners.
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Originally Posted by Adventure.AS

Please refer to the post from Sean, above, in which he agrees that the pivot point moves from the TV axle to the hitch head which is well behind the bumper, when the tension is taken away from the system.

No, His post says, the LINKS pivot at the hitch. Not the pivot point. Pivot point remains at the apex of the triangle formed by the shape of the parallelogram - well forward of the hitch itself.

[SailorSam205]

Originally Posted by avionstream

Sway control can keep the trailer from returning to directly behind the tv when in very slippery conditions. This can occur with separate sway devices or WD hitches with sc built in. Not mentioned much anymore, but on some WD,sc hitches the manuals used to mentioning loosening up the sc in the rain.

That and on friction based sway control, water is a lubricant. Never put lubricants on the friction surfaces of this kind of hitch.

[ATownTX]

Water is not that good of a lubricant, it won't prevent the metal on metal friction. I suppose it could lessen it some. Anyway, if you get into an accident that wasn't an act of god or the result of someone else's negligence then you are failing to maintain a safe speed.

[Boxite]

I too once worried (incorrectly) about a friction anti-sway control being as reluctant to allow a trailer to return to trail as it would resist departure from trail. I've since experienced the device and realize that is not a factor.

I'm not worried about water on the friction-pads of the anti-sway bar any more than I'd be on the discs of the wheel brakes (which receive far more water during rain conditions.)

It seems to me that the friction sway-bar behaves like a secondary attach-point of TT to TV. A friction SB does not act independent of the hitch. Any inclination of the TT to depart from straight-line with the TV is resisted by the SB. In fact, IF the TT departs, say sways left,... the SB will act in tension as a lever using the hitch as a fulcrum...to straighten both vehicles to each other, even applying pressure against the hitch to keep the vehicles in alignment.
This action will be incrementally much greater than any resistance-of-return to trailing because the return-to-trail is a shorter distance and the TV is still pulling.
The only problem would be if when decelerating, the TT brakes were not acting more aggressively than the TV brakes or if decelerating without braking while turning at speed. (I won't be doing that because I know better. And, this points again to the benefits to be derived from requiring training/certification before allowing motorists to tow.)

[gypsydad]

This is becoming an interesting discussion; I love it when engineering types start to argue about physics and math problems! We used the "anti-sway" device on our smaller Casita for 2 years towing and I found that when set up properly, it worked as intended. My concern was, how do you "really" know it is set up properly, since it was a manual friction type device? I like the safety of the WDH's with sway control built in. After using 3 different manufacturers devices on our 25' AS's, the last 2 being Blue-Ox, my experience has been they work well if set up properly, with no real friction settings needed. I have had 1 instance last summer, while going 60 where I had to abruptly swerve hard left to avoid a "speeder" in a sports car who came up behind me and switched lanes to pass me on the right. I had looked to switch lanes to also get into the right lane prior, and it was clear. When he accelerated, I had already started my lane change when the wife screamed! I swerved back left into the fast lane, but the momentum took me over the lane into the center dirt strip as the TT whipped behind me one time. The WDH straightened me right out; we were able safely merge back onto the highway. I pulled over at next exit so I could catch up with my heart! A scare the wife and I did not need, but surely a wake up call. Bottom line, I would not trust pulling a 4,000lb + TT without using a WDH with built in sway. You don't have to be an engineer to understand their value; just read the forum!

[USAtraveler]

Originally Posted by Adventure.AS

I will ignore your attempted deflection of my question by using sarcasm for now, but Sean, please clarify (as you keep avoiding the question) - will the PPP style of hitch pivot to an off center-line position (similar geometry to the diagram below) if the tow vehicle transmission suddenly downshifts or if coasting to a stop when the PPP hitch will loose its pivot point project when the hitch is NOT under tension - Yes or No?

Attachment 282621

Is it also correct that in the above scenario the pivot point will now be at the hitch head which is much further behind a normal ball hitch position and no longer projected to the tow vehicle rear axle - Yes or No?

Sorry...I didn't see an answer to your questions. Would have been nice to get a clear response. Would have been better yet to get another drawing showing how force vectors are dealt with if different from your dwg.

[dkottum]

We have towed extensively throughout the country (especially the western mountainous states) many, many times with the Hensley/ProPride hitch and NEVER experienced a "bump". I have heard that it would indicate poorly adjusted angle of the receiver/hitch head or poorly adjusted weight distribution (not enough).

Get your Hensley/Propride set up right and don't worry about "bumps" and push and side winds and semi bow wave pushing you around and trailer following at an angle to the truck and trailer sway and all the other crap you otherwise encounter with bumper-pull trailers.

[Boxite]

Thanks for the Alternate Facts.

[USAtraveler]

It must be difficult after one has spent $2500 plus tax and installation on a fancy WD hitch to concede it is anything less than the highly-positive/no-negative claims of the mfg.

[xrvr]

Originally Posted by USAtraveler

It must be difficult after one has spent $2500 plus tax and installation on a fancy WD hitch to concede it is anything less than the highly-positive/no-negative claims of the mfg.

Easy now.

[HowieE]

This is one of many products to suppress the BUMP resulting from acceleration or deceleration that is common while towing a trailer.

Oh and by the way they do not work on heaver trailers. The BUMPING just hammers them into submission.

[HowieE]

Sorry I forgot the picture.