Payload math / weight distribution hitch

[dznf0g]

Originally Posted by BayouBiker

You may have misunderstood. Profxd was speaking of weight scale tickets not speeding tickets....

Most here will agree, knowingly or not, when one makes a choice to tow with the hitch behind the bumper rather than over the rear axle, they have made a choice that is sub optimal regardless of tow vehicle choice. Where the disagreement arises is whether and how to address it.

Rational people understand that within the boundaries or givens of their firm choices, maximizing stability, cornering and suspension performance is ideal, even if they don't intend to test the boundaries with higher speeds, poor weather or rough roads.

A few will suggest the owner do noting to improve the situation, just accept it and happily motor down the road even knowing you could do better. They may agree holding speeds down is wise. Rational people reject this approach.

Many will advise choosing a more capable tow vehicle so the performance and stability degradation are within acceptable limits and this is sound advice, but even these vehicles suffer losses that are readily recoverable.

Most here will advocate so long as the vehicle choice is fundamentally sound and capable, for any vehicle, simple steps taken at the hitch point to address fundamental deficiencies of the hitch point design are both reasonable and wise. Some will accept the principle expressed in this approach but will argue against optimizing the setup perhaps due to concern some will not do it properly. But the result, when set up correctly will improve stability, cornering, handling and comfort for all fundamentally capable towing combinations.

I find those who for whatever reason suggest sub optimal set ups are not able to justify their rationale in a way reasonable people can accept. They either need to demonstrate that WD and sway control when set up properly and is optimized creates a problem worse than those it solves. Then they need to offer real solutions that perform better by all measures than the passive hitch solutions WD and sway control provides.

Time and time again people complain about the risk of not applying WD and Sway Control correctly but never seem to offer something both less risky and better performing. It seems to always fall back to "live with it and drive slowly" never addressing the real risk of having a little Sion smash into your back end or worse.

Yeah, as usual, you're not on the same page. Over and out.

[BayouBiker]

Originally Posted by ROBERT CROSS

Solve no, prove.

You are not using our rig, so please don't apply your 'opinions' to it.🤓

I have 17 safe towing Seasons with all but 100lb being returned to the front axle.
50+k confirms how safe we are. (18yrs with our Safari)

Perfect example of someone claiming a particular WD tension is too much without any objective evidence to apply to the specific case and in contradiction to the reality that optimal WD tension is specific to particular setup. Its like a broken clock, it will be right twice a day. A one size fits all approach to FALR will be right for a handful of setups but wrong for the vast majority. It's just common sense.

[Gene]

Originally Posted by Collyn

General Motors went through a bad period in the 1980s. This was largely due a buyer demand for soft suspension at a time when not enough was known about it.

Collyn

And many years before and after. That Olds I inherited had a lot more wrong with it than suspension. The 1960's Buick did have a terrible suspension. I have had vehicles from the US, Britain, Germany and Japan. Only the Japanese ones were reliable, handled well and they had better gas mileage too. The German ones were VW's, including a 1959 bug, and they were cheap vehicles not meant to last, but easy to fix.

I towed a 25' Airstream for more than 60,000 miles with an Equalizer and a half ton Japanese truck (though made in the US with lots of US components) and had no towing issues. Now we have a big (off-)white box that is higher off the road and tow with a Blue Ox. It is harder to tow and we drive slower. I could adjust the Equalizer three different ways and I saw a noticeable improvement after I adjusted it (never trust a dealer to adjust a hitch). The BO has little to adjust. The dealer set it at the 7th link, I increased it to the 8th. That improved things and got the truck close to level. I took it back to the dealer and they tried moving the head up, but that didn't work. If I had a direct comparison, I would certainly have a better idea of the relative pluses and minuses of the BO vs. the Equalizer, but still prefer the Equalizer. I could try the 9th link, but I think I would need an elephant to help me because there would be too much effort necessary to get it to that link. That thought leads to me wondering whether the binding is connected to having the chains too tight, or perhaps that is a contributing factor.

I cannot understand the statement that friction devices (like the Equalizer) have no effect on sway when you are driving straight down the road. Presumably when you are driving straight down the road there should be no sway and no friction needed. You only get friction to matter when the trailer decides to track differently.

At times my wife has followed me and when I think there is some sway, she says there is none. I have read of people contending a trailer can sway and you won't notice it, but it seems I imagine it when it is not happening.

[ROBERT CROSS]

Originally Posted by BayouBiker

Perfect example of someone claiming a particular WD tension is too much without any objective evidence to apply to the specific case and in contradiction to the reality that optimal WD tension is specific to particular setup. Its like a broken clock, it will be right twice a day. A one size fits all approach to FALR will be right for a handful of setups but wrong for the vast majority. It's just common sense.

.... Test your set-up.

On our way home from CA last Season, very light traffic on a 4 lane non interstate. Nice steady 20mph 60* cross wind.
I have my Hensley jacks marked.
I drove several miles at the marks above and below my 100lb light FAW mark
I was not surprised that although the one mark above the ideal was doable it did not feel as secure/comfortable.👍

Real world conformation of the MacGyver School of engineering.
“Education is what people do to you,
Learning is what you do to yourself”
Joichi Ito

Bob
🇺🇸

[Collyn]

Originally Posted by ROBERT CROSS

.... Test your set-up.

On our way home from CA last Season, very light traffic on a 4 lane non interstate. Nice steady 20mph 60* cross wind.
I have my Hensley jacks marked.
I drove several miles at the marks above and below my 100lb light FAW mark
I was not surprised that although the one mark above the ideal was doable it did not feel as secure/comfortable.👍

Real world conformation of the MacGyver School of engineering.
“Education is what people do to you,
Learning is what you do to yourself”
Joichi Ito

Bob
🇺🇸

I have a feeling that the 'MacGyver School of Engineering' is mainly the ability to recognise a mistake when you have made that mistake for the fourth or fifth time. Not necessarily how to solve it.

Collyn

[Collyn]

Originally Posted by Gene

And many years before and after. That Olds I inherited had a lot more wrong with it than suspension. The 1960's Buick did have a terrible suspension. I have had vehicles from the US, Britain, Germany and Japan. Only the Japanese ones were reliable, handled well and they had better gas mileage too. The German ones were VW's, including a 1959 bug, and they were cheap vehicles not meant to last, but easy to fix.

I towed a 25' Airstream for more than 60,000 miles with an Equalizer and a half ton Japanese truck (though made in the US with lots of US components) and had no towing issues. Now we have a big (off-)white box that is higher off the road and tow with a Blue Ox. It is harder to tow and we drive slower. I could adjust the Equalizer three different ways and I saw a noticeable improvement after I adjusted it (never trust a dealer to adjust a hitch). The BO has little to adjust. The dealer set it at the 7th link, I increased it to the 8th. That improved things and got the truck close to level. I took it back to the dealer and they tried moving the head up, but that didn't work. If I had a direct comparison, I would certainly have a better idea of the relative pluses and minuses of the BO vs. the Equalizer, but still prefer the Equalizer. I could try the 9th link, but I think I would need an elephant to help me because there would be too much effort necessary to get it to that link. That thought leads to me wondering whether the binding is connected to having the chains too tight, or perhaps that is a contributing factor.

I cannot understand the statement that friction devices (like the Equalizer) have no effect on sway when you are driving straight down the road. Presumably when you are driving straight down the road there should be no sway and no friction needed. You only get friction to matter when the trailer decides to track differently.

At times my wife has followed me and when I think there is some sway, she says there is none. I have read of people contending a trailer can sway and you won't notice it, but it seems I imagine it when it is not happening.

Gene
The issue with friction damping is that any given frictional force is a constant force. The forces involved with trailer sway, however, increase with the square of the rig's speed.

This is not just theory. Tests have shown that the effect of a typical friction damper is as low as 1% at 60 mph.

The laws relating to Coulomb friction have been known since the 1780's - when formated by Charles-Augustin de Coulomb.

As with other basic physical laws, 'opinon' is not relevant.
Collyn

[BayouBiker]

Does a "typical friction damper" have the same hitch angle damping as a properly tensioned Equalizer hitch? Isn't it misleading to cite the lowest number when many of the simple adjustable friction dampers are capable of generating significantly more angular resistance than the paper cited and when the authors themselves generated numbers larger than 1%?

Nothing worse than a contrarian citing studies that are not analogous and then not offering anything more effective.

[ROBERT CROSS]

Originally Posted by Collyn

I have a feeling that the 'MacGyver School of Engineering' is mainly the ability to recognise a mistake when you have made that mistake for the fourth or fifth time. Not necessarily how to solve it.

Collyn

...another of your opinions, and of course engineers NEVER make faulty executions do they?

MacGyver...correcting an engineering failure under the shade of the Paw Paw Tree with items at hand.

Tell 'ya what you 'solve' the way you want and I'll do the same.

Why not go back to arguing with your peers instead of wasting your intellect on this poor uninformed dolt?.

Bob
🇺🇸

[Profxd]

Originally Posted by BayouBiker

Does a "typical friction damper" have the same hitch angle damping as a properly tensioned Equalizer hitch? Isn't it misleading to cite the lowest number when many of the simple adjustable friction dampers are capable of generating significantly more angular resistance than the paper cited and when the authors themselves generated numbers larger than 1%?

Nothing worse than a contrarian citing studies that are not analogous and then not offering anything more effective.

The friction of a Equalizer hitch is indeed constant and doesn’t change with speed. The simple dual friction type bars are probably close to the Equalizer. So yes he’s correct and the active sway control of the vehicle ESC system is much better then passive friction control. These are facts so I don’t expect either one of you to understand.

[BayouBiker]

You failed to address the question asked which was the degree of damping provided by an Equalizer verses the style used in the study. Nowhere did I discuss the resistance profile of an Equalizer or suggest it was anything other than constant with respect to vehicle velocity. They are categorized passive for a reason.

It is not correct for either of you to directly state or even suggest hitches like Equalizer provides just 1% of required resistance to dampen sway at 55 mph for capable vehicle and trailer combinations when properly set up. Don't get me wrong, I am not suggesting the Equalizer design is the most effective sway control, it is not, but it is competent and effective.

Active sway control is also effective and useful but it has its limits and issues. A search of the web for papers on the topic will confirm that. Passive and Active measures compliment each other.

So you see, I am not questioning or misunderstanding the facts. It's just they are not responsive to the question asked.

[Al and Missy]

I will never forget that GM engineers gave us the 350ci gasoline engine that they "converted " to diesel. I bought one. I had the cracked heads replaced at 20,000 miles under warranty and at 40,000 when the "improved" replacement heads cracked I swapped the engine out for a 5.7L gasoline engine with a 4bbl electronically controlled carb. I installed all the sensors, computer, and cables and got a remarkable 12-14 mpg. That cost me $1200 and about 40 hours of my labor. GM compensated me with about $350 as I recall.

That was my last GM product - purchased in 1980.

[Gene]

Originally Posted by Collyn

Gene
The issue with friction damping is that any given frictional force is a constant force. The forces involved with trailer sway, however, increase with the square of the rig's speed.

This is not just theory. Tests have shown that the effect of a typical friction damper is as low as 1% at 60 mph.

The laws relating to Coulomb friction have been known since the 1780's - when formated by Charles-Augustin de Coulomb.

As with other basic physical laws, 'opinon' is not relevant.
Collyn

This does not appear to be a responsive answer. I do not know about Coulomb, but I do know that when towing in 40 mph crosswinds on snow, the Equalizer equipped hitch system worked perfectly, no sway at all. But I am glad you found a job at GM, a company where you fit in well. I don't recall GM made weight distributing hitches or trailers however, and barely made cars.

[Bruce B]

Originally Posted by Al and Missy

I will never forget that GM engineers gave us the 350ci gasoline engine that they "converted " to diesel. I bought one. I had the cracked heads replaced at 20,000 miles under warranty and at 40,000 when the "improved" replacement heads cracked I swapped the engine out for a 5.7L gasoline engine with a 4bbl electronically controlled carb. I installed all the sensors, computer, and cables and got a remarkable 12-14 mpg. That cost me $1200 and about 40 hours of my labor. GM compensated me with about $350 as I recall.

That was my last GM product - purchased in 1980.

Wow!
Remind me not to make you unhappy 😆
In my automotive career I know of no company that hasn’t produced a lemon or two going back some 40 years...
I do understand the feeling, I just don’t act on it anymore.
cars and trucks are simply so different these days that I find my old brand favorites mean little. I am far more brand agnostic than I ever was...

[BayouBiker]

While we are on the topic of vehicle velocity and yaw damping perhaps Colin and profxd, who both seem to be advocates of large understeer gradients, might comment on the the effect raising the understeer gradient has on yaw damping and dynamic stability (sway critical speed). With that in mind, I note again that their suggestion for the ideal understeer gradient continues to be elusive.

[Profxd]

Originally Posted by BayouBiker

You failed to address the question asked which was the degree of damping provided by an Equalizer verses the style used in the study. Nowhere did I discuss the resistance profile of an Equalizer or suggest it was anything other than constant with respect to vehicle velocity. They are categorized passive for a reason.

It is not correct for either of you to directly state or even suggest hitches like Equalizer provides just 1% of required resistance to dampen sway at 55 mph for capable vehicle and trailer combinations when properly set up. Don't get me wrong, I am not suggesting the Equalizer design is the most effective sway control, it is not, but it is competent and effective.

Active sway control is also effective and useful but it has its limits and issues. A search of the web for papers on the topic will confirm that. Passive and Active measures compliment each other.

So you see, I am not questioning or misunderstanding the facts. It's just they are not responsive to the question asked.

Why don’t you just fire up your crystal ball (“The model”) and let everyone know what the answer is? The automotive industry doesn’t put much consideration into hitch friction sway control for good reason. Why do vehicle manufacturers say a WDH is a requirement yet don’t make hitch sway control a requirement? Lets see it loses its effectiveness the faster you go and it is worse at controlling sway then active sway control so it’s limitations are much higher then active sway control.

Sway should be reduced/controlled at its source, the trailer not the hitch!

There is no consistency in the amount of WDH tension consumers use based on trailer tongue weight and tow vehicle variations as tension controls the amount of friction and sway damping it can produce. Reliance on hitch friction sway control is a crap shoot so do yourself a favor and don’t rely on it. Establish stability by properly loading the trailer and selecting a adequate tow vehicle that keeps the dynamic critical speed above highway speeds. Adding some friction at the hitch should be just an extra margin of safety.

[Collyn]

Originally Posted by Profxd

Why don’t you just fire up your crystal ball (“The model”) and let everyone know what the answer is? The automotive industry doesn’t put much consideration into hitch friction sway control for good reason. Why do vehicle manufacturers say a WDH is a requirement yet don’t make hitch sway control a requirement? Lets see it loses its effectiveness the faster you go and it is worse at controlling sway then active sway control so it’s limitations are much higher then active sway control.

Sway should be reduced/controlled at its source, the trailer not the hitch!

There is no consistency in the amount of WDH tension consumers use based on trailer tongue weight and tow vehicle variations as tension controls the amount of friction and sway damping it can produce. Reliance on hitch friction sway control is a crap shoot so do yourself a favor and don’t rely on it. Establish stability by properly loading the trailer and selecting a adequate tow vehicle that keeps the dynamic critical speed above highway speeds. Adding some friction at the hitch should be just an extra margin of safety.

Originally Posted by Profxd

Why don’t you just fire up your crystal ball (“The model”) and let everyone know what the answer is? The automotive industry doesn’t put much consideration into hitch friction sway control for good reason. Why do vehicle manufacturers say a WDH is a requirement yet don’t make hitch sway control a requirement? Lets see it loses its effectiveness the faster you go and it is worse at controlling sway then active sway control so it’s limitations are much higher then active sway control.

Sway should be reduced/controlled at its source, the trailer not the hitch!

There is no consistency in the amount of WDH tension consumers use based on trailer tongue weight and tow vehicle variations as tension controls the amount of friction and sway damping it can produce. Reliance on hitch friction sway control is a crap shoot so do yourself a favor and don’t rely on it. Establish stability by properly loading the trailer and selecting a adequate tow vehicle that keeps the dynamic critical speed above highway speeds. Adding some friction at the hitch should be just an extra margin of safety.

Re 'Sway should be reduced/controlled at its source, the trailer not the hitch!'

While in some cases, such as excess trailer length or poor load distribution, there are many causes of trailer sway. These include:

Towing by a vehicle that is too light or too short.
Excess hitch overhang
Too low rear tyre pressure
Too high front tyre pressure
Inadequate tow ball mass
Overally stiff rear suspension
Excess WDH (FALR needs restricting to 50%)

There appears to be a misunderstanding re friction stablizers. It is that the friction remains constant - but the force (momentum) sthat it must constrain increase with the square of the road speed. Thus a stabilizer that is fine at 20 mph cannot possibly be at 60 mph. This simply a basic law of physics. I do not doubt the experience of someone who finds his/her rig stable at all speeds - it indicates that rig is very stable anyway - and does not need that device.

Re a 'desirable' degree of understeer'. Essentially one that does not need the driver to make ongoing corrections as road camber changes. This is less of an issue when not towing. It is, however, vital that tow does not oversteer whilst towing. If it does, jacknifing is virtually inevitable.

Re ongoing remarks re my time with GM. If you care to check my bio you will that I have done many other things in my life.
Collyn

[BayouBiker]

I'm quite happy Collyn addressed one of Profxd's many errors. Didn't note any else worthy of responding to in profxd's screed.

It also seems we have landed on the reluctant lower understeer gradient is good so long as one does not cross into oversteer, though I hope he would accept even then it is recoverable so long as the combination critical speed is not exceeded. Here longer wheelbase vehicles can have an advantage, and of course excess WD has little to do with a rather arbitrary 50% FALR as it is "excess" generally only if it results in oversteer.

With respect to yaw damping of course the square of road speed is but one factor in the complex matrix equations governing sway critical speed so that when all are included the increase in damping required to remain stable is closer to linear. But in practice its much less than even that because its not necessary to maintain damping coefficient constant at all speeds. It's actually allowable to let it to drop even rapidly with velocity as it's only necessary to maintain it above 0.1 for speeds no faster than one actually travels.

It's a nice trick to call out a hitch because it can't do the impossible when all that is required is it do the minimum to maintain stability at speeds you actually drive. Collyn seems to have backed into that same conclusion in his remarks.

Well designed travel trailers when loaded for 15% tongue weight regardless of the size generally settle out with a sway critical speed of around 70mph when connected to a typical tow vehicle with a weight limit near the trailer weight. This combination needs just modest sway support to get the speed over 75-80 and provide a margin of safely to tow at US highway speeds. If we were to accept Collyn's initial implied guidance we'd be targeting a critical speed near 150 or more!

[Collyn]

Originally Posted by BayouBiker

I'm quite happy Collyn addressed one of Profxd's many errors. Didn't note any else worthy of responding to in profxd's screed.

It also seems we have landed on the reluctant lower understeer gradient is good so long as one does not cross into oversteer, though I hope he would accept even then it is recoverable so long as the combination critical speed is not exceeded. Here longer wheelbase vehicles can have an advantage, and of course excess WD has little to do with a rather arbitrary 50% FALR as it is "excess" generally only if it results in oversteer.

With respect to yaw damping of course the square of road speed is but one factor in the complex matrix equations governing sway critical speed so that when all are included the increase in damping required to remain stable is closer to linear. But in practice its much less than even that because its not necessary to maintain damping coefficient constant at all speeds. It's actually allowable to let it to drop even rapidly with velocity as it's only necessary to maintain it above 0.1 for speeds no faster than one actually travels.

It's a nice trick to call out a hitch because it can't do the impossible when all that is required is it do the minimum to maintain stability at speeds you actually drive. Collyn seems to have backed into that same conclusion in his remarks.

Well designed travel trailers when loaded for 15% tongue weight regardless of the size generally settle out with a sway critical speed of around 70mph when connected to a typical tow vehicle with a weight limit near the trailer weight. This combination needs just modest sway support to get the speed over 75-80 and provide a margin of safely to tow at US highway speeds. If we were to accept Collyn's initial implied guidance we'd be targeting a critical speed near 150 or more!

I have never suggested (nor would) that understeer be more than required to keep a vehicle steady on a cambered road and critically to cause the vehicle to automatically take up a marginally larger radius - thus reducing centrifual (centripetal) force. It is really intended for less experienced drivers - who may otherwise spin out of control. Understeer does cause the steering to seem less responsive.

Re recovering from excess oversteer, this is easy and natural for experienced drivers.

Do be aware, however, that is literally impossible to correct tow vehicle oversteer if that happens while you are towing. This is because the opposite lock required to do so will cause that rig instantly to jacknife.

Re speed. There is critical speed for every rig at which it is liable to sway out of control. The longer the trailer, the higher (within reason) the tow ball mass, and the heavier and longer the tow vehicle, the higher that speed.

May I just comment that, to be irrelevant about my few early years at GM (UK) research, a few members of this forum do not necessarily need to be offensive. My job there was largely to design the equipment to remedy the vehicles' suspension known issues.

One question please - do many of this forum's members understand the concept and implications of tyre slip angles?

Re spelling - there innumerable minor differences between English and US spelling, and also punctuation. I only know the English as used (and often misused!) in Australia. Mea culpa.

Collyn

[Profxd]

“I'm quite happy Collyn addressed one of Profxd's many errors. Didn't note any else worthy of responding to in profxd's screed.“

Wishful thinking there Brian. He didn’t say that you can load a trailer in what ever manner you choose or tow a poorly designed trailer without issue. Did he say sway control on the hitch fixes everything? No he didn’t. There’s many contributions to sway but solving trailer loading issue first should be priority 1. There’s no doubt that most here don’t understand the principles of tire cornering stiffness and slip angles.

[BayouBiker]

Collyn and I agree on the basic principles, I'm glad you noticed. We may diverge on the solution, but not so much there either. I find it a bit disingenuous to call out an issue and turn a molehill into a mountain but other than that not so bad. Collyn doesn't say directly but he strongly implies the best solution is to get a larger and more capable vehicle and don't worry about optimizing it. Me, I generally think better is always better, but I get that some people have givens that prevent them from changing vehicles. I also get some people are so wedded to their vehicle they think it can't possibly go wrong and they are bound and determined to make it work.