Best Anti-Sway Tow Hitch

[J. Morgan]

Having no new sway events to talk about on AirForums is kinda priceless too.

[rmkrum]

Originally Posted by J. Morgan

Having no new sway events to talk about on AirForums is kinda priceless too.

I've seen far too many pictures rollovers from sway events and sloppy driving. If installing a ProPride is overkill, so be it. I don't need the white-knuckle experiences or the catastrophic results. As I have said many times before, a smooth ride while family and pets are aboard is priceless. The percentage of cost of the hitch just against the cost of the AS and TV is tiny. What are lives worth?

Been doing engineering all my life. Don't like "just good enough' solutions when I'm driving, or flying. I worked for Boeing. "Snap Landings" are not good ones. The very best ones are ones you walk away from, and can immediately reuse the vehicle...with out inducing a 'laundry problem'...IMHO.

[SailorSam205]

Originally Posted by Mollysdad

Best?
If I own a used Equalizer hitch that I paid $150 for on CL, and someone pays $3000 for a high end hitch, and neither of us has any sway, then isn't mine best?

From Equalizer's web page describing how their hitch works:
"Friction Sway Control
Friction is enhanced by downward pressure from the trailer tongue and upward pressure on the spring arms. These opposing pressures come together to create an unequaled sway control system. This pressure combats trailer sway more effectively than any other sway control hitch on the market"

From the only engineering study I've been able to find on this subject. Done at the University of Bath in England. The Brits name for sway is snaking :
"As mentioned in 2.2.7.1, anti-snaking devices incorporating a friction damper at the tow ball provide a fixed level of coulomb friction. This means that there is a constant level of energy dissipation per oscillation cycle, which implies that the equivalent linear damping decreases as the amplitude increases. There is a clear danger here, that the friction level will be sufficient for low amplitude stability but insufficient for high amplitude stability. The possibility arises that the coupled combination will become unstable as an immediate consequence of a particular disturbance. It can be expected that the driver’s control behaviour will be based on experience of small-amplitude oscillations, so sudden larger-amplitude oscillations following a chance disturbance will be hazardous, there being no guarantee of the driver’s behaviour being sympathetic to the situation."

Hitches based on the Hensley patents do not use friction. The Hensley Arrow has a sway elimination guarantee. Copied from the Hensly web site: "Though more expensive than friction style hitches, it is the only hitch that guarantees the elimination of trailer sway".

So is a hitch using a design that an independent engineering study states has the potential for uncontrollable sway or one that guarantees sway elimination better?
YMMV

[PKI]

Originally Posted by SailorSam205

-- snip -- friction damper at the tow ball provide a fixed level of coulomb friction. This means that there is a constant level of energy dissipation per oscillation cycle, which implies that the equivalent linear damping decreases as the amplitude increases. "
-- sip --

On an EQ hitch, I have always assumed that the head tilt would increase pressure and the associated friction with oscillation amplitude. A brake pad friction device might not increase friction with ocillation, but the friction would be constant throughout the amplitude. This analysis appears suspect. Pat

[Profxd]

Originally Posted by SailorSam205

From Equalizer's web page describing how their hitch works:
"Friction Sway Control
Friction is enhanced by downward pressure from the trailer tongue and upward pressure on the spring arms. These opposing pressures come together to create an unequaled sway control system. This pressure combats trailer sway more effectively than any other sway control hitch on the market"

From the only engineering study I've been able to find on this subject. Done at the University of Bath in England. The Brits name for sway is snaking :
"As mentioned in 2.2.7.1, anti-snaking devices incorporating a friction damper at the tow ball provide a fixed level of coulomb friction. This means that there is a constant level of energy dissipation per oscillation cycle, which implies that the equivalent linear damping decreases as the amplitude increases. There is a clear danger here, that the friction level will be sufficient for low amplitude stability but insufficient for high amplitude stability. The possibility arises that the coupled combination will become unstable as an immediate consequence of a particular disturbance. It can be expected that the driver’s control behaviour will be based on experience of small-amplitude oscillations, so sudden larger-amplitude oscillations following a chance disturbance will be hazardous, there being no guarantee of the driver’s behaviour being sympathetic to the situation."

Hitches based on the Hensley patents do not use friction. The Hensley Arrow has a sway elimination guarantee. Copied from the Hensly web site: "Though more expensive than friction style hitches, it is the only hitch that guarantees the elimination of trailer sway".

So is a hitch using a design that an independent engineering study states has the potential for uncontrollable sway or one that guarantees sway elimination better?
YMMV

The study you reference is referring to the extra bolt on friction devices but principles are the same for hitches with built in sway control. This is why proper trailer loading and TV selection so important to keep the combo well below it’s critical speed during normal highway operation. You can look the VPP as a fix or a band-aid to resolve the deficiency.

[ROBERT CROSS]

It's a fix....how long have you used your 'VPP'?

Bob


"Im not an enginear, I just play one on the interweb".

[J. Morgan]

Originally Posted by ROBERT CROSS

It's a fix....how long have you used your 'VPP'?

Bob


"Im not an enginear, I just play one on the interweb".

I think you and I agree that bolting on a devise that totally eliminates sway, wiggles, semi-pushes, downgrade anxiety, and crosswind white knuckles is more of a cure than just a band aid.

[J. Morgan]

Originally Posted by Profxd

The study you reference is referring to the extra bolt on friction devices but principles are the same for hitches with built in sway control. This is why proper trailer loading and TV selection so important to keep the combo well below it’s critical speed during normal highway operation. You can look the VPP as a fix or a band-aid to resolve the deficiency.

I take it that you avoid “band aids” by towing on the ball?

[gypsydad]

3rd Blue Ox hitch, after I broke the Equalizer that came with 2nd 25' AS. Happy with the BlueOx. Did not like the Reese on my first AS; was dirty to deal with. My first Blue Ox was messy also, but the new design from few years ago works fine, not too expensive ($500~). With over 20K miles, towing the 25' AS FB and now the new 28' AS, I am happy. Pay what you want to for the hitch you think is best, and lets move on.

This thread is getting way too opinionated and the bias of "some opinionated" folks sure is overtaking the value of sharing actual experience offered from some of the seasoned travelers...kind of like the F150 thread got out of hand...not helping to argue, in my "opinion".

[SailorSam205]

Originally Posted by PKI

On an EQ hitch, I have always assumed that the head tilt would increase pressure and the associated friction with oscillation amplitude. A brake pad friction device might not increase friction with ocillation, but the friction would be constant throughout the amplitude. This analysis appears suspect. Pat

A study is published (which I suspect you have NOT read) based on multiple actual tests, with appropriate sensors generating measurable results, and contains an analysis which you disagree with. Then based on your ASSUMPTION of how a product works, you declare the analysis suspect?

Even if an EQ hitch does dynamically increase the associated friction level when sway occurs there is still a maximum amount of friction that can be generated. Lateral force applied that exceeds the level needed for maximum friction will result in bent metal.

I doubt there is a dynamic increase because the same lateral force is created when turning - a driver induced turn would increase friction and make turning harder. I suspect this would cause wear on the friction surfaces, lowering the effectiveness of the hitch to combat sway.

Note that the EQ web site states that the forces creating friction come from the trailer weight applied on the ball (top down) and from the force exerted by the weight distribution bars (bottom up) squeezing the friction surfaces. No mention is made of friction being cause by any type of lateral force. So how a lateral force would impact the amount of force creating friction doesn't make sense to me.

Yes, the study is based on a bolt on friction device. I really wish someone would do a similar study using a Blue Ox or Equalizer. I suspect that the manufacturers have done this type of testing but are not publishing the results. That Hensley states they guarantee sway elimination leads me to believe that they have the statistical evidence to back up the guarantee.

In the end, friction is friction. It is reasonable to extend statistically based findings to other types of friction based devices.

I'm happy to have my opinion changed if you can provide statistical evidence to support you assumption. However, I am not swayed by anecdotal evidence. Personal observations can serve as wonderful examples to introduce a topic and build it up – without statistical evidence it is just opinion. One contrary example destroys the opinion. That person X has Y miles towing without issue only proves that they haven't hit a bad enough situation. The vast majority of trailers use ball mount, anti-sway hitches. Therefore, it is reasonable to assume that some percentage of the catastrophic sway accidents are using them. Due to the nature of this argument, I would expect wide spread posting if one of the accidents had involved a PPP hitch.

It is interesting to me that I have read many posts from people trying to "tune" their rigs with ball mount hitches due to sway issues. How may posts of this type exist for PPP hitches? Lots of posts from people who have problems learning how to hitch up, sway issues - I've seen 1. How many people load their trailers exactly the same way for every trip - in order to keep the weight balance exactly right to keep the trailer from swaying? How much of a difference is needed to have problems? 10lbs?

[Mollysdad]

Originally Posted by PKI

On an EQ hitch, I have always assumed that the head tilt would increase pressure and the associated friction with oscillation amplitude.

Me too.

A brake pad friction device might not increase friction with ocillation, but the friction would be constant throughout the amplitude. This analysis appears suspect. Pat

Really? Why?

Originally Posted by gypsydad

This thread is getting way too opinionated and the bias of "some opinionated" folks sure is overtaking the value of sharing actual experience offered from some of the seasoned travelers...kind of like the F150 thread got out of hand...not helping to argue, in my "opinion".

Yep.

[wolf146]

Originally Posted by uncle_bob

Hi

So have we made it through that yet again? Can we all go back to sleep for another three days when the exact question is asked and all the same emotion froths to the surface?

Bob

I concur, so I'll keep it simple. The one I use is the best!! Wolf146

[ROBERT CROSS]

>>>>>No sway here.

https://www.youtube.com/watch?v=4b4wpQcFrt0

Bob

[PKI]

SS - the following quote does not follow my understanding of friction. "This means that there is a constant level of energy dissipation per oscillation cycle, which implies that the equivalent linear damping decreases as the amplitude increases."

My understanding is that a friction mechanism continues to provide resistance accross the range of motion as long as the pressure and coefficient of friction remain the same.

I do distrust friction as a sway control method. However, I keep trying to understand the advantages/disadvantages to help with design analysis.

Slow down and drive conservatively. Pat

[uncle_bob]

Originally Posted by PKI

SS - the following quote does not follow my understanding of friction. "This means that there is a constant level of energy dissipation per oscillation cycle, which implies that the equivalent linear damping decreases as the amplitude increases."

My understanding is that a friction mechanism continues to provide resistance accross the range of motion as long as the pressure and coefficient of friction remain the same.

I do distrust friction as a sway control method. However, I keep trying to understand the advantages/disadvantages to help with design analysis.

Slow down and drive conservatively. Pat

Hi

You have damping on a resonant system. One technical way to look at this is Q. That would be the energy stored in the system / energy dissipated in the system on a per cycle basis. Work out how many kilojoules are bound up in the swinging trailer and compare it to how many kilowatts of heat come off the friction bars.

In a sway to destruction situation where the amplitude is increasing, *more* energy is going into the system (per cycle) than is lost. In this case, whatever you are doing to dump energy is being overcome by an energy source.

In a real system, it is never either / or. You have a range of cases. Put in more energy and things get more exciting. Put in less energy and they calm down.

Bob

[PKI]

Originally Posted by uncle_bob

-- snip -- In a real system, it is never either / or. You have a range of cases. -- snip --

Bob - got it - explains why it is so important to prevent sway from starting. Pat

[Mollysdad]

Originally Posted by ROBERT CROSS

>>>>>No sway here.

The wind loading alone makes me cringe!

[J. Morgan]

A well set and adjusted friction devise will likely dampen oscillation enough to maintain control especially for those who drive 60 MPH, but the Hensley designed devices lock sway out. It can’t happen.

There are many devises that are suited to many people, but for me, It will always be ProPride or Hensley.

The brilliant sway solution that is engineered into these devices makes them superior to all others. The fact that they are actual machines in their own right makes them expensive.

[SailorSam205]

Originally Posted by PKI

SS - the following quote does not follow my understanding of friction. "This means that there is a constant level of energy dissipation per oscillation cycle, which implies that the equivalent linear damping decreases as the amplitude increases."

My understanding is that a friction mechanism continues to provide resistance accross the range of motion as long as the pressure and coefficient of friction remain the same. Pat

Originally Posted by uncle_bob

Hi

You have damping on a resonant system. One technical way to look at this is Q. That would be the energy stored in the system / energy dissipated in the system on a per cycle basis. Work out how many kilojoules are bound up in the swinging trailer and compare it to how many kilowatts of heat come off the friction bars.

In a sway to destruction situation where the amplitude is increasing, *more* energy is going into the system (per cycle) than is lost. In this case, whatever you are doing to dump energy is being overcome by an energy source.

In a real system, it is never either / or. You have a range of cases. Put in more energy and things get more exciting. Put in less energy and they calm down. hi

Bob

Yup, what Bob said.... I'm not sure, but the energy not absorbed by the hitch on one side of the sway cycle may be added as the trailer
reverses making the total energy input even higher on the subsequent oscilation....

One other thing I got from the study (my interpretation, not stated by the author). It is impossible to load a trailer so that it will never sway if the trailer can pivot on a ball hitch. There will always be a speed above which the trailer will sway. So the admonition to slow down is well stated.

[PKI]

The anti-snaking study referenced appears to be this one.

http://webby.natcoa.net/Caravan.pdf

Has some interesting info, including their use of a specific ball mounted friction device.

https://www.google.com/search?q=Al-k...iw=640&bih=307

Odd device, but the european application is odd as well. The principles may be transferable, but the EQ design is supposed to have the equavalent of multiple friction devices (reference product video), so maybe not.

This would not be the study I would have used to discount US type friction Weight Distribution sway control devices. But - no I have not read it all, yet. Pat