Tongue weight - Page 4 - Fiberglass RV


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Old 03-03-2011, 06:58 PM   #43
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Originally Posted by honda03842 View Post
Thank you Jim,

Not much on the why. I understand that side forces on the trailer, natural or created wind, can overcome the side friction of the trailer's tires causing the body of the trailer to slide sideways. Reaction by the driver can cause this to become an oscillation and a rollover.

I still don't understand what tongue weight does for the tow vehicle or the trailer, other than further load the rear tires. I do not see how this significantly counteracts the sway potential of the trailer.

In a small measure, extra weight on the rear wheels does help the rear wheels resist side forces from the trailer when the trailer gives an off access push on the rear of the tow vehicle.

Obviously the heavier the tow vehicle the lower the ability of the trailer to push the rear of the tow vehicle sideways due to higher friction between the tire and road.

An equally important factor is the distance of the ball from the rear axle. The strength of fifth wheels is that all weight is over the axle.

I know someone has the answer to the right amount of tongue weight and 10 to 15% may be a good value; I just don't know why.

Norm
If you tongue weight is low, the center of gravity of the trailer is further to the rear. Picture holding a 2x4 at the end and trying to swing it and then trying to stop the swing. You can not because you have no leverage. Now move the center of gravity to midpoint and you have control over both ends.
Your trailer weighs 2000 lbs and you are shifting some of that onto the tow vehicle. The more you shift the further forward the cog becomes between your car and trailer. Thus better control.
With -0- tongue weight the rear of the trailer will have a tendency to steer the car and you will feel it in the steering. It becomes worst, the faster you drive.
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Old 03-03-2011, 09:52 PM   #44
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Not being an engineer, I don't have any idea why manufacturers come up with the tongue weight limits they do. I do know that my Dodge and Subaru have different recommendations, so that's what I go by. Just make sure your trailer is level when you measure the tongue weight, being tilted back will lower the tongue weight and being tilted forward will increase the tongue weight on most trailers as the center of gravity shifts. Perhaps that's why they all specify "some" tongue weight, otherwise towing uphill would result in a negative tongue weight.
There have been some reports of cracked frames on trailers, a "too high" tongue weight might be a contributing factor.
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Old 03-04-2011, 12:14 PM   #45
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John as I mentioned earlier I think the difference **may** be that your Dodge is a rear wheel drive (or 4 x 4?) and the Subaru is a All Wheel Drive so they are built with different components and weight distribution in an unloaded state. Obviously in a 2 wheel drive when you put your foot on the gas the weight transfer is to the rear wheels only and on an All Wheel Drive weight is transferred to all 4 wheels. As I understand it a rear wheel drive vehicle is built with a lot more weight at the front in an unloaded condition than an All Wheel Drive vehicle. Its also my understanding that a vehicle that is built as an All Wheel Drive will be a heavier vehicle than the same vehicle if it where built only as a 2 wheel drive due to all the extra parts needed to make it an All Wheel Drive.

To complicate things it appears there are big differences in how the All Wheel Drive vehicles are designed as well. Subaru's system is different from that of Honda and other manufactures or at least it appears to be. How and why is a bit beyond my understanding of cars. ;-) But a while back I found this interesting video which does not actually explain the differences in how the various All Wheel Drives are designed to work but it does show that there is a differences in how they responded to different situations which would suggest they are not all built/designed the same either.

I'm not an engineer but I have a hunch that how we load up an All Wheel Drive may have a bigger impact in regards to traction and its safe drive, than it does on a rear wheel drive. I tend to think that the manufactures know how they are designed, so I’m probable better to go with what they say in regards to weight loading than to go with a general rule of thumb.

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Old 03-04-2011, 08:21 PM   #46
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It is a little ironic that I'm concerned about exceeding the factory tongue weight by 150-200 lbs here and on another post in the forum someone is pulling a 7500 lb airstream trailer with tongue weight of 800 lbs. His tow vehicle, a Ford Edge is rated 3500 lbs and tongue weight 350 lbs. Go figure.....
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Old 03-04-2011, 08:34 PM   #47
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It is a little ironic that I'm concerned about exceeding the factory tongue weight by 150-200 lbs here and on another post in the forum someone is pulling a 7500 lb airstream trailer with tongue weight of 800 lbs. His tow vehicle, a Ford Edge is rated 3500 lbs and tongue weight 350 lbs. Go figure.....
Yeah Jim, we have already had some discussions about that one too.
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Old 03-04-2011, 08:44 PM   #48
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Yup saw that! May seem to tow well now but you have to wonder how long before the rear end falls out of the Edge. ;-) Whats intreasting is that the Edge is a Front Wheel drive so it would seem possible that if one really over loaded the back end at some point you would loose traction at the front end which could put you into a not so great steering situation. Wonder what the number is? or under what road conditions or move could make it happen.
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Old 03-05-2011, 01:22 AM   #49
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Hmm. My tongue weight at the Quartzsite NOG was 240#. My OB is rated for 200#. When I measured it at home when I first got it, I measured 190#. Of course I have added another tongue jack.

The tongue weight stated on the Egg Camper site is 250#.

My Subaru pulls just fine. I get about 19.5 MPG. I have to check this last trip.
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Old 03-05-2011, 02:23 PM   #50
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I keep reading about the magic 10 to 15% tongue weight but no where have I found a justification. European tongue weights are usually less than 10%.
Tongue weight percentage is spoken of as the only factor that matters in sway prevention and there is plenty of evidence that this isn't so.

To study the effect, try this British 'caravan' (trailer) stability game - it may be called a game but it's based on real science:
Bailey of Bristol - Caravan Stability Studies

You will see that inertia is at least as important as tongue weight (called nose weight in Britain) but I suspect because it's so difficult to measure inertia, everyone just ignores it and concentrates on tongue weight only.

One important difference when looking at lower European tongue weights is lower European towing speeds - 60mph is considered fast. As well as speed making sway more likely, it also produces aerodynamic lift on the front end of most trailers, making sway happen even sooner. If you look at all modern European trailers you will see a sloping front and that is there to stop the aerodynamic lift and so make the trailer more stable.
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Old 03-05-2011, 02:46 PM   #51
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Originally Posted by Andrew Gibbens View Post
Tongue weight percentage is spoken of as the only factor that matters in sway prevention and there is plenty of evidence that this isn't so.

To study the effect, try this British 'caravan' (trailer) stability game - it may be called a game but it's based on real science:
Bailey of Bristol - Caravan Stability Studies

You will see that inertia is at least as important as tongue weight (called nose weight in Britain) but I suspect because it's so difficult to measure inertia, everyone just ignores it and concentrates on tongue weight only.

One important difference when looking at lower European tongue weights is lower European towing speeds - 60mph is considered fast. As well as speed making sway more likely, it also produces aerodynamic lift on the front end of most trailers, making sway happen even sooner. If you look at all modern European trailers you will see a sloping front and that is there to stop the aerodynamic lift and so make the trailer more stable.
How about adding that link to "Resources" on the home page?
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Old 03-05-2011, 07:14 PM   #52
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I tried the stability game and found that raising tongue weight to about 10% enabled faster travel, but the system commented that such a weight was quite high and my tow vehicle might not be designed for so much tongue weight. It's a different mindset across the pond, for sure.
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Old 03-06-2011, 05:26 AM   #53
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...but the system commented that such a weight was quite high and my tow vehicle might not be designed for so much tongue weight. It's a different mindset across the pond, for sure.
Indeed. As we are generally using smaller tow vehicles, too much tongue weight is considered a risk to the stability of the tow vehicle itself. Certainly front wheel drive tow vehicles work better when their front wheels are on the ground....

One thing is apparent - things that are impossible or wildly dangerous on one continent happen every day without problem on the other one (high speed, low tongue weight, etc). Contrary to most peoples' belief, there is more than one way to skin a cat.
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Old 03-06-2011, 12:06 PM   #54
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Fifth wheel has weight over tongue stronger suspension will help air bags helper springs to a limit.

Our hitches are at rear, we are working with a lever; the distance from ball to axle creating lift on front wheels.

The closer the ball is to the rear axle the less the effect, also wheel base length (longer reduces effect).

I have seen a case that had the front wheels unable to steer properly due to rear load. Excessive ball extension also increases stress on the hitch.

"We can balance the load though packing to set amount on the tongue"

Place a standard tow bar into the hitch receiver and you can move it up down and sideways this movement is over come when weight is placed on it. The amount needs to over come the effects of driving in relation too the trailer that is why we use the % amount.

Tongue weight requirement is also effected by the clearance height and wheel base of the TV and trailer 'roll over proponent-ency' and many other factors.

Balanced tires can rotate faster then unbalance with out shimmy axle alignment, load distribution (balance) and aerodynamics are just some factors.

Weight distribution (WD) system transfer a portion of the load forward.
Problems is some do not set them up correctly the car, SUV, or truck should drop in height the same front and back when setup is correct. Single bar units do not twist load but are limited in capacity. Some dual bar units use friction working like sway bars.

WD systems double the tongue capacity of the tv by sharing the load front and back, but we have to reduce that by the weight of the unit. Trailer brakes take baking load of tv and Transaxle coolers reduce heat and help as well. Some vehicles come with two ratings one with trailer brakes, WD, and added coolers and one without.

Tongue weight, Tow bar or WD system unit are added weight as are all items in trunk or hatch area behind axle.

30 plus years ago was taught to measure front and back with TV trunk empty then after loaded tork the bars so drop is equal front and back on TV.

Single bar WD systems do not apply twist but do move load forward. They have are limited in amount they can do. Dual bar units create some limited twist. Balance and friction designs provide anti sway like friction sway bars equalizer (this one works with surge brakes) is one such unit. The style I use requires a separate friction sway bar.

Most 400/4000 units have a tongue working weight range of 100 lbs to 400 lbs and 600/10000 units 200 lbs to 600 lbs and and work fine. They need to be match to the total expected tongue load to work right was told.
hitch tongue weight + draw bar (WD) + load in TV behind axle.

This is all a simplified view and does not cover all factors but is an attempt to explain our needs as taught to me. I am not an expert but this has worked for me.
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Old 03-06-2011, 12:59 PM   #55
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Quote:
Originally Posted by Andrew Gibbens View Post
Indeed. As we are generally using smaller tow vehicles, too much tongue weight is considered a risk to the stability of the tow vehicle itself. Certainly front wheel drive tow vehicles work better when their front wheels are on the ground....

One thing is apparent - things that are impossible or wildly dangerous on one continent happen every day without problem on the other one (high speed, low tongue weight, etc). Contrary to most peoples' belief, there is more than one way to skin a cat.
It's a lot more dangerous on this continent than many of us want to believe.

Here's an excerpt from a recent article, the whole of which can be found at

Drivers pulling trailers are responsible for thousands of accidents in Utah - ABC 4.com - Salt Lake City, Utah News

This particular wreck involves a boat trailer, but the physics are much the same. Be sure to check out the link included to "Dangerous trailers.org"

(BEGIN QUOTE)
Print Story Published: 12/13/2010 2:27 pm ShareThis Updated: 12/16/2010 7:45 am
SALT LAKE CITY (ABC 4 News) Utah Highway Patrol has finished its investigation and submitted its findings surrounding an injury accident on I-15 in Spanish Fork. It's now up to prosecutors to decide what to do about the owner of a boat and trailer that came unhitched on the interstate and slammed into two cars. Sadly, six people were injured. Fortunately no one was killed.

However, that isn't always the case when it comes to trailer accidents. "Since 1975 15,523 people have been killed by passenger cars that tow trailers." Ron Melancon should know, he is an expert on trailer accidents. His incredibly indepth website - Dangerous Trailers.org is filled with pictures, stories and data. Over the past eight years - since his own run in with a trailer without tail lights he has been studying the issue and fighting for and passing legislation in his home state of Virginia. "Since 1988 - 490 thousand (injuries to) people, including the six who were just injured in Utah, have been caused by people towing a trailer."
(END QUOTE)

Be afraid- and CAREFUL- out there!
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Old 03-06-2011, 05:27 PM   #56
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I've been to dangeroustrailers.org and it doesn't seem to summarize the findings which would be particularly valuable for understanding what causes trailer accidents. To try to understand, I took one state and tried to understand each accident he lists. As well I looked at the Utah accident link

The founder of the site divides the accidents by states. I took a look at all Alabama accidents and found that most accidents are utility trailers (3) and commercial trailers (6) with trailer acidents accounting for (5). The articles always seem to call out utility or commercial trailers but never RV trailers, just trailers. I assume 5 for RV trailers.

It seemed that the most common reason for an accident was disconnection of the trailer from the tow vehicle. (A safety survey, I think on the Casita site, listed "unintentionally becoming unhitched" as a shockingly high percentage of problems, I believe 15%.)

For perspective on trailer accidents in Utah, 112 people died in 35 years in trailer accidents while approximately 8000 died in motor vehicle accidents in the same period, a 1000 from DUIs and 3000 from excessive speed.

My view is that the typical RV Trailer tow is careful. I never check my car's tail lights, but I check the trailer's lights and my tow vehicle's lights every time I tow. (It turns out the founder of dangerous trailers drove into the back of a trailer that had no tail lights.) If more regulation was the solution, we would not have DUIs or speeders.

Safety is important, and so is perspective.

Norm



Quote:
Originally Posted by Francesca Knowles View Post
It's a lot more dangerous on this continent than many of us want to believe.

Here's an excerpt from a recent article, the whole of which can be found at

Drivers pulling trailers are responsible for thousands of accidents in Utah - ABC 4.com - Salt Lake City, Utah News

This particular wreck involves a boat trailer, but the physics are much the same. Be sure to check out the link included to "Dangerous trailers.org"

(BEGIN QUOTE)
Print Story Published: 12/13/2010 2:27 pm ShareThis Updated: 12/16/2010 7:45 am
SALT LAKE CITY (ABC 4 News) Utah Highway Patrol has finished its investigation and submitted its findings surrounding an injury accident on I-15 in Spanish Fork. It's now up to prosecutors to decide what to do about the owner of a boat and trailer that came unhitched on the interstate and slammed into two cars. Sadly, six people were injured. Fortunately no one was killed.

However, that isn't always the case when it comes to trailer accidents. "Since 1975 15,523 people have been killed by passenger cars that tow trailers." Ron Melancon should know, he is an expert on trailer accidents. His incredibly indepth website - Dangerous Trailers.org is filled with pictures, stories and data. Over the past eight years - since his own run in with a trailer without tail lights he has been studying the issue and fighting for and passing legislation in his home state of Virginia. "Since 1988 - 490 thousand (injuries to) people, including the six who were just injured in Utah, have been caused by people towing a trailer."
(END QUOTE)

Be afraid- and CAREFUL- out there!
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