On-trailer anti sway
10-09-2016, 02:07 AM
#1
On-trailer anti sway
Not that I own a travel trailer yet, but some time ago on one of the automotive shows on TV I had seen a trailer anti sway device that mounted to the trailer itself. It used a G sensor to detect sway in the trailer and then applied the trailer brakes individually (left/right) to eliminate the sway. It seemed like a very effective way to do it, but I can't seem to find information on it any more. Does anyone have info or experience with this?
In addition, thinking about the above device, I'm surprised that no one has come out with antilock brakes on the trailer itself. Of course it would require a computer and wheel sensors and tone rings, but I would think the added safety factor would be a huge attraction for buyers. I know I would pay a premium for safety like this.
In addition, thinking about the above device, I'm surprised that no one has come out with antilock brakes on the trailer itself. Of course it would require a computer and wheel sensors and tone rings, but I would think the added safety factor would be a huge attraction for buyers. I know I would pay a premium for safety like this.
10-10-2016, 02:11 AM
#3
Senior Member
Trailer sway control built into the trailer makes no sense. The technology would have to be smart enough to know when the times that the trailer is not in a straight line behind the tow vehicle was sway or intentional, such as lane changes, turns, and curves. Since we have seen adaptive cruise control put on brakes at inappropriate times, lane control warnings to freak out when there is snow on the road, how trustworthy would the technology be that would decide when to apply corrections? If changing lanes on the interstate or driving down a curvy mountain road, I don't want my trailer to be fighting me incorrectly thinking there is sway.
Far better than sway-correcting technology is to prevent the sway in the first place rather than try to correct it.
That is done by:
1. Having a truck that will pull the trailer within all specs (GVWR, GCVWR, payload, axle ratings, frontal area limits, and tongue weight limits) in stock configuration. If the truck will only handle the trailer with add-on remedies like overload springs, airbags, timbrens, etc., it is too much trailer for the truck.
2. Having a truck with longer wheelbase. An F150 with a 163.1 or 156.5 inch wheelbase will have far more leverage in both handling the weight from the front to rear tires, but also far more leverage in the truck not being affected by lateral forces from passing semi-trucks, side-winds, and trailer movement. 125.9" and 133.3" wheelbase trucks are not as capable towing without sway.
3. A quality weight-distributing trunnion-bar hitch what has sway prevention devices, such as the Equilizer or others discussed on these forums, properly adjusted.
4. Shorter trailers have less leverage to pass along lateral movement upon the truck and it's hitch. Don't buy more trailer than is absolutely necessary (for camping, the idea is to get away from it all; not to take it all with you).
5. Driving. The tow vehicle and trailer should be driven conservatively, not 70 mph plus, swerving between lanes and cars. Slower speeds result in less likelihood of sway, and if sway occurs, it will be more manageable. Avoid towing altogether on extremely high wind or snow and ice conditions.
6. Packing. Don't pack a trailer unevenly from side-to side or front-to-back, as the uneven weight will make the trailer list to one side or the other (sway), or cause too much or too little weight on the hitch. The worst case scenario is to try to make a trailer that is too big and heavy for the truck lighter on the hitch by loading weight behind the trailer axles. This unloading of weight from the hitch is a recipe for sway.
7. A well-maintained trailer and tow vehicle with minimum suspension mods. Under-inflated tires, loose suspension bolts, oversized tires, aftermarket lifts and levels, can either cause erratic vehicle handling, decrease payload, and increase vehicle sagging when loaded.
Also, anti-lock brakes on a trailer makes no sense whatsoever. The purpose of anti-lock brakes is to momentarily stop the braking so you can steer the vehicle and prevent it from hitting something. You have no steering on a trailer. The only thing that you want to do with a trailer is to stop it when desired, and at times, as soon as possible. Anti-lock brakes would increase the stopping time by pulsing the brakes, and do nothing to prevent sway or enable better handling of the tow vehicle steering in a panic stop on slick conditions.
Far better than sway-correcting technology is to prevent the sway in the first place rather than try to correct it.
That is done by:
1. Having a truck that will pull the trailer within all specs (GVWR, GCVWR, payload, axle ratings, frontal area limits, and tongue weight limits) in stock configuration. If the truck will only handle the trailer with add-on remedies like overload springs, airbags, timbrens, etc., it is too much trailer for the truck.
2. Having a truck with longer wheelbase. An F150 with a 163.1 or 156.5 inch wheelbase will have far more leverage in both handling the weight from the front to rear tires, but also far more leverage in the truck not being affected by lateral forces from passing semi-trucks, side-winds, and trailer movement. 125.9" and 133.3" wheelbase trucks are not as capable towing without sway.
3. A quality weight-distributing trunnion-bar hitch what has sway prevention devices, such as the Equilizer or others discussed on these forums, properly adjusted.
4. Shorter trailers have less leverage to pass along lateral movement upon the truck and it's hitch. Don't buy more trailer than is absolutely necessary (for camping, the idea is to get away from it all; not to take it all with you).
5. Driving. The tow vehicle and trailer should be driven conservatively, not 70 mph plus, swerving between lanes and cars. Slower speeds result in less likelihood of sway, and if sway occurs, it will be more manageable. Avoid towing altogether on extremely high wind or snow and ice conditions.
6. Packing. Don't pack a trailer unevenly from side-to side or front-to-back, as the uneven weight will make the trailer list to one side or the other (sway), or cause too much or too little weight on the hitch. The worst case scenario is to try to make a trailer that is too big and heavy for the truck lighter on the hitch by loading weight behind the trailer axles. This unloading of weight from the hitch is a recipe for sway.
7. A well-maintained trailer and tow vehicle with minimum suspension mods. Under-inflated tires, loose suspension bolts, oversized tires, aftermarket lifts and levels, can either cause erratic vehicle handling, decrease payload, and increase vehicle sagging when loaded.
Also, anti-lock brakes on a trailer makes no sense whatsoever. The purpose of anti-lock brakes is to momentarily stop the braking so you can steer the vehicle and prevent it from hitting something. You have no steering on a trailer. The only thing that you want to do with a trailer is to stop it when desired, and at times, as soon as possible. Anti-lock brakes would increase the stopping time by pulsing the brakes, and do nothing to prevent sway or enable better handling of the tow vehicle steering in a panic stop on slick conditions.
Last edited by Velosprout; 10-10-2016 at 02:23 AM.
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SarcasmSpasm (10-18-2016)
10-10-2016, 02:27 AM
#4
I beg to differ. The system I saw used a G load sensor to detect movement consistent with sway. The G forces applied when the trailer reverses direction during sway would likely be easy to differentiate from lane change or corner turning maneuvers. The ability to control the left and right trailer brakes independently would be much more effective at damping any sway that does happen vs a single channel system. The review I watched said the system complemented the OEM anti sway on the truck very well, though I do not recall which brand of truck it was. IIRC, the system also used a GPS sensor to determine vehicle speed so that it was not active during low speed turning where sway simply cannot occur.
I will agree that preventing sway from happening by proper weight distribution and WDH / anti sway hitch is preferable. However, even with a proper setup, sway can happen under unpredictable roadway conditions. These systems are simply another layer that gives the owner a greater margin of safety. Is it worth the cost to you? Well, that would be something each owner has to answer for themselves, but that was not the focus of this thread.
As far as antilock, it is simply not true that it is ONLY for assisting in steering during emergency braking. Antilock systems also dramatically reduce straight line emergency braking distances, especially under adverse road conditions such wet, icy, or unimproved roadways, by preventing wheel lockup. You cannot predict every road surface condition you will face when setting the trailer brake gain. You simply do not understand how antilock systems work. A locked brake and sliding tire takes MUCH longer to stop than antilock systems that keep the tire rolling but at maximum braking power by pulsing the system at the point of lockup.
I will agree that preventing sway from happening by proper weight distribution and WDH / anti sway hitch is preferable. However, even with a proper setup, sway can happen under unpredictable roadway conditions. These systems are simply another layer that gives the owner a greater margin of safety. Is it worth the cost to you? Well, that would be something each owner has to answer for themselves, but that was not the focus of this thread.
As far as antilock, it is simply not true that it is ONLY for assisting in steering during emergency braking. Antilock systems also dramatically reduce straight line emergency braking distances, especially under adverse road conditions such wet, icy, or unimproved roadways, by preventing wheel lockup. You cannot predict every road surface condition you will face when setting the trailer brake gain. You simply do not understand how antilock systems work. A locked brake and sliding tire takes MUCH longer to stop than antilock systems that keep the tire rolling but at maximum braking power by pulsing the system at the point of lockup.
Last edited by VTX1800N1; 10-10-2016 at 02:31 AM.
10-10-2016, 02:48 AM
#5
Senior Member
I do understand how antilock brakes work, and on wet, icy, snow, and gravel road conditions, anti-lock brakes can substantially increase braking distance. According to the NHTSA as much as 27.2% longer stopping distance. https://en.wikipedia.org/wiki/Anti-lock_braking_system
10-10-2016, 03:38 AM
#6
Physics disagrees with Wikipedia. Brakes work by converting kinetic energy into thermal energy. In order for this conversion to happen, the wheel and brake must be turning. If the wheel is locked, no more kinetic energy can be converted into thermal at the brake pads. Some kinetic energy will be converted to thermal at the tire where it slides along the road surface, but not at anywhere near the rate that the brake pads and a large cast iron disc or drum can. Dumping that much thermal energy into tire would likely light it on fire. In addition, on ice, the heat that is created can form a thin film of water between the tires and underlying ice and reduce friction (traction) even further. This is exactly how ice skates work. What you are talking about is an isolated case where the tires are on a medium for which lockup would produce a plowing effect. It's one possibility among many others. Considering that a TT or 5th wheel often outweighs the tow vehicle, I'd rather have the antilock to keep the trailer inline during emergency braking in adverse road conditions than have trailer wheel lockup and have it come sliding around you. Ever have a matchbox car with a locked up rear wheel when you were a kid? If you pushed it rapidly on a smooth surface and let it go, it will flip around and continue on backwards every time.
The NHTSA website describes the plowing effect you are talking about, and although it does say ABS is not designed to reduce stopping distances, it also says may in fact do just that, particularly on wet or icy roads surfaces, just as I said. Physics says it's much better to keep the wheel turning rather than lock it up.
http://www.nhtsa.gov/cars/problems/e...absbrakes.html
The NHTSA website describes the plowing effect you are talking about, and although it does say ABS is not designed to reduce stopping distances, it also says may in fact do just that, particularly on wet or icy roads surfaces, just as I said. Physics says it's much better to keep the wheel turning rather than lock it up.
http://www.nhtsa.gov/cars/problems/e...absbrakes.html
Last edited by VTX1800N1; 10-10-2016 at 03:52 AM.
10-10-2016, 07:43 AM
#7
It seems Jayco/HighRdige and other lines are making this standard equipment on their Travel Trailers starting in 2017.
http://www.lci1.com/sway
Travel Trailer Sway
Advanced patent-pending microprocessor technology electronically detects trailer sway and applies the trailer brakes to suppress unwanted sway, utilizes both an accelerometer (measures lateral force) and gyro sensor (measures angular velocity) to quickly and accurately differentiate between side-to-side and up-and-down movement to prevent false activation.
Light pod mounts to the front of the trailer and signals to the driver when the system is functioning properly
Rigorously tested in sway-inducing towing conditions, including emergency maneuvers.
http://www.lci1.com/sway
Travel Trailer Sway
Advanced patent-pending microprocessor technology electronically detects trailer sway and applies the trailer brakes to suppress unwanted sway, utilizes both an accelerometer (measures lateral force) and gyro sensor (measures angular velocity) to quickly and accurately differentiate between side-to-side and up-and-down movement to prevent false activation.
Light pod mounts to the front of the trailer and signals to the driver when the system is functioning properly
Rigorously tested in sway-inducing towing conditions, including emergency maneuvers.
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10-11-2016, 01:47 AM
#8
Senior Member
In a panic stop, I want the trailer to remain behind the tow vehicle. While the tow vehicle needs the control of ABS to allow it to steer, I want the trailer wheels to act as a boat anchor or pulling-tractor sled, causing maximum friction between the road surface and the trailer tires. Since the fully locked-up non-ABS trailer tires would be rotating at a slower speed than the still-rotating (due to ABS) wheels and tires of the tow vehicle, it would naturally be snapped back to a location lagging or behind the tow vehicle, which is where we want it. If instead a trailer-mounted ABS system was pulsing the trailer brakes to keep the wheels rolling, independently of the truck's ABS system, the trailer wheel speed could exceed the speed of the tow vehicle's wheels; not a good thing.
It seems to me that much greater improvement in braking would be replacement of electric brakes with electric controlled hydraulic disc brakes. The higher response time of voltage triggering the magnets to activate electric drum brakes would be a barrier to effective ABS or sway control on a trailer.
If sway starts, a tap of the brake controller manually slows the trailer down slower than the tow vehicle and "slaps" the trailer back into place.
I still argue that preventing sway is more important than controlling sway. A real technological improvement would be Ford providing a factory installed weight-sensing truck receiver hitch which provides an on-dash digital readout on the hitch weights, and compatible with all types of hitches, including weight distributing hitches. The tech exists, (https://www.weigh-safe.com/) but is should be built into the receiver instead of a non-weight distributing hitch.
Feel free to buy a automatic trailer-based sway control if you feel you need it. I would currently avoid it. Like the trailer backing assist, this system may be especially useful for inexperienced drivers. If you have enough sway to trigger this system, you are not set up properly, using an undersized truck, an oversized trailer, or driving to fast for conditions in weather not suited for towing.
If you read the owner's manual on the sway controlling device whose link posted above in an earlier post, the trailer mounted sway control device is not compatible with several years of factory installed brake controllers, which would potentially reduce the trailer resale value and create liability issues .
It seems to me that much greater improvement in braking would be replacement of electric brakes with electric controlled hydraulic disc brakes. The higher response time of voltage triggering the magnets to activate electric drum brakes would be a barrier to effective ABS or sway control on a trailer.
If sway starts, a tap of the brake controller manually slows the trailer down slower than the tow vehicle and "slaps" the trailer back into place.
I still argue that preventing sway is more important than controlling sway. A real technological improvement would be Ford providing a factory installed weight-sensing truck receiver hitch which provides an on-dash digital readout on the hitch weights, and compatible with all types of hitches, including weight distributing hitches. The tech exists, (https://www.weigh-safe.com/) but is should be built into the receiver instead of a non-weight distributing hitch.
Feel free to buy a automatic trailer-based sway control if you feel you need it. I would currently avoid it. Like the trailer backing assist, this system may be especially useful for inexperienced drivers. If you have enough sway to trigger this system, you are not set up properly, using an undersized truck, an oversized trailer, or driving to fast for conditions in weather not suited for towing.
If you read the owner's manual on the sway controlling device whose link posted above in an earlier post, the trailer mounted sway control device is not compatible with several years of factory installed brake controllers, which would potentially reduce the trailer resale value and create liability issues .
Last edited by Velosprout; 10-11-2016 at 01:49 AM.
10-12-2016, 04:27 PM
#9
I think this is what the OP is looking for.
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VTX1800N1 (10-16-2016)
10-16-2016, 03:24 AM
#10
It seems that Ford agrees that antilock brakes on a trailer would be a good thing. From my owners manual, Version 3, page 263:
"The gain setting sets the trailer brake controller for the specific towing condition. You should change the setting as towing conditions change. Changes to towing conditions include trailer load, vehicle load, road conditions and weather.
The gain should be set to provide the maximum braking assistance while making sure the trailer wheels do not lock when using the brakes. Locked trailer wheels may lead to trailer instability."
On page 264:
"Avoid towing in adverse weather conditions. The trailer brake controller does not provide antilock control of the trailer wheels. Trailer wheels can lock up on slippery surfaces, resulting in reduced stability of the trailer and tow vehicle."
"The gain setting sets the trailer brake controller for the specific towing condition. You should change the setting as towing conditions change. Changes to towing conditions include trailer load, vehicle load, road conditions and weather.
The gain should be set to provide the maximum braking assistance while making sure the trailer wheels do not lock when using the brakes. Locked trailer wheels may lead to trailer instability."
On page 264:
"Avoid towing in adverse weather conditions. The trailer brake controller does not provide antilock control of the trailer wheels. Trailer wheels can lock up on slippery surfaces, resulting in reduced stability of the trailer and tow vehicle."