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#51
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COBRA Anti-Sway Coupler
On Monday, September 7, 2020 at 4:36:06 PM UTC-7, Eric Greenwell wrote:
wrote on 9/7/2020 2:51 PM: On Monday, September 7, 2020 at 11:30:06 AM UTC-6, Nick Hoare wrote: To get back to the original posters question the only thing I would say is that really they are for make a good combination better not a bad combination good. If it is not safe without an anti-sway hitch it probably won't be safe with one, you will just be going a bit faster when it all goes wrong. Nick is entirely correct. You can't fix an unstable trailer with an antisway device, but you can make up for a (slightly) unsatisfactory tow vehicle. Once again, MASS + longer wheelbase = better stability. And adding weight to the tow vehicle does NOTHING to increase the stability of the trailer, and the higher loading on the vehicle's rear wheels is likely to make a sway problem worse. (Think: Moment of Inertia.) That being said, some weight on a lightly loaded rear axle will help with traction, but not stability. Generally, it's the characteristics of the tow vehicle and trailer that determines the stability of the combination. We all know a trailer might tow better with one vehicle but not the other one. My motorhome and mini-van illustrate this principle well: the motorhome can tow the trailer much faster for the same wiggle than the van can. So, by adding weight to the tow vehicle (usually between the axles but favoring the rear axle), then raising the tire pressures to match the new weight, can yield a more stable combination. Using a friction damping device like the Cobra clamp coupler can also increase the stability of the combination. There are other devices to increase the damping that are frequently used on travel trailers, but the Cobra unit is easy to use. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 Adding weight to the tow vehicle won't much difference except to slow down its rate of acceleration. This is because the suspension and tires aren't designed to handle this extra weight. A trailer-vehicle combination is a very complex spring-mass mechanical system. Such systems will have a natural resonant frequency. This paper gives an idea of just how complex these systems a https://tinyurl.com/yylt9uj3 The bottom line is that the critical speed, above which the car-trailer combination becomes unstable, is determined by: 1. mass of the car. 2. mass of the trailer. 3. distance of the hitch from the CG of the car. 4. damping provided by the car and trailer suspension. The car's manufacturer has already taken all of this into account to come up with (2) the maximum mass of the trailer (they will have to estimate the trailer's suspension damping). Eric's suggestion was to add weight to the car to move the CG rearward. This is a self-limiting trick because you are always dealing with the maximum combined vehicle weight, which you will be pushing with these smaller cars. There are suspension mods you can make to increase the stiffness (damping) of the suspension. Of course, increasing tire pressure increases their stiffness, which is important. Personally, I have added airbags to my F250 pickup for towing a travel trailer that can weigh upwards of 10,000 lb fully loaded. Ultimately, there is a speed above which the car-trailer combination becomes unstable. Driving at this speed means you have no stability margin and a disturbance (wind gust, sudden steering movement, passing truck) will make you unstable. You can't recover from this - it happens too fast and steering/braking inputs just make it worse (see the videos). So you need to drive at a slower speed to give yourself some margin, probably at least 10 mph slower. Tom |
#52
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COBRA Anti-Sway Coupler
One adisional factor is the distance of the hitch from the rear axle. Less is more. In a perfect world you would put the pivot point between the rear wheels of the tow vehicle. There are two hitches for travel trailers that atempt to achive/simulate this. The Hensley does it with some fancy linkages, but eliminates the tow ball as a result. But in any event, some tow vehicle mass can be replaced with tow geometry. Not that I am recommending this, but I have seen a duo towed with a VW bottle. I towed a 304cz with a bottle, and the safe speed iwas about 10mph slower than my ukonxl. The upon was 2 x the mass, but much farther from the axle to the hitch
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#53
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COBRA Anti-Sway Coupler
You REALLY need to get glasses. Or a bigger keyboard. Some parts of this post looks like a Google Translation from Klingon.
VW bottle? |
#55
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COBRA Anti-Sway Coupler
I wonder if this would sway... https://www.youtube.com/watch?v=o6HOXghLG94
On 9/8/2020 5:08 AM, RR wrote: One adisional factor is the distance of the hitch from the rear axle. Less is more. In a perfect world you would put the pivot point between the rear wheels of the tow vehicle. There are two hitches for travel trailers that atempt to achive/simulate this. The Hensley does it with some fancy linkages, but eliminates the tow ball as a result. But in any event, some tow vehicle mass can be replaced with tow geometry. Not that I am recommending this, but I have seen a duo towed with a VW bottle. I towed a 304cz with a bottle, and the safe speed iwas about 10mph slower than my ukonxl. The upon was 2 x the mass, but much farther from the axle to the hitch -- Dan, 5J |
#56
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COBRA Anti-Sway Coupler
On Tuesday, September 8, 2020 at 9:02:37 AM UTC-7, Eric Greenwell wrote:
2G wrote on 9/7/2020 9:31 PM: On Monday, September 7, 2020 at 4:36:06 PM UTC-7, Eric Greenwell wrote: wrote on 9/7/2020 2:51 PM: On Monday, September 7, 2020 at 11:30:06 AM UTC-6, Nick Hoare wrote: To get back to the original posters question the only thing I would say is that really they are for make a good combination better not a bad combination good. If it is not safe without an anti-sway hitch it probably won't be safe with one, you will just be going a bit faster when it all goes wrong. Nick is entirely correct. You can't fix an unstable trailer with an antisway device, but you can make up for a (slightly) unsatisfactory tow vehicle. Once again, MASS + longer wheelbase = better stability. And adding weight to the tow vehicle does NOTHING to increase the stability of the trailer, and the higher loading on the vehicle's rear wheels is likely to make a sway problem worse. (Think: Moment of Inertia.) That being said, some weight on a lightly loaded rear axle will help with traction, but not stability. Generally, it's the characteristics of the tow vehicle and trailer that determines the stability of the combination. We all know a trailer might tow better with one vehicle but not the other one. My motorhome and mini-van illustrate this principle well: the motorhome can tow the trailer much faster for the same wiggle than the van can. So, by adding weight to the tow vehicle (usually between the axles but favoring the rear axle), then raising the tire pressures to match the new weight, can yield a more stable combination. Using a friction damping device like the Cobra clamp coupler can also increase the stability of the combination. There are other devices to increase the damping that are frequently used on travel trailers, but the Cobra unit is easy to use. https://sites.google.com/site/motorg...ad-the-guide-1 Adding weight to the tow vehicle won't much difference except to slow down its rate of acceleration. This is because the suspension and tires aren't designed to handle this extra weight. A trailer-vehicle combination is a very complex spring-mass mechanical system. Such systems will have a natural ... Eric's suggestion was to add weight to the car to move the CG rearward. This is a self-limiting trick because you are always dealing with the maximum combined vehicle weight, which you will be pushing with these smaller cars. My suggestion was in the context of towing with a pickup or a minivan, both of which can have a wide range of weight from empty to fully laden; for my minivan, that is over 1000 pounds, and the pickups I've owned it can be as much as 3000 lbs. So, it is possible to add significant weight to these vehicles, which can aid in increasing the stability of the vehicle/trailer combination, and still obey the vehicle weight ratings. Please note I'm not saying this is the best way to achieve higher-speed stability, but only that it is a workable method. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 It is important to actually weigh the loaded tow vehicle and trailer to ensure that you are within the GCVW - most people don't. This rating is NOT arbitrary. I actually had one manager of an RV trailer dealership tell me I could exceed the rated tow capacity by a large amount! Tom |
#57
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COBRA Anti-Sway Coupler
On Tuesday, September 8, 2020 at 10:26:49 AM UTC-7, Dan Marotta wrote:
I wonder if this would sway... https://www.youtube.com/watch?v=o6HOXghLG94 On 9/8/2020 5:08 AM, RR wrote: One adisional factor is the distance of the hitch from the rear axle. Less is more. In a perfect world you would put the pivot point between the rear wheels of the tow vehicle. There are two hitches for travel trailers that atempt to achive/simulate this. The Hensley does it with some fancy linkages, but eliminates the tow ball as a result. But in any event, some tow vehicle mass can be replaced with tow geometry. Not that I am recommending this, but I have seen a duo towed with a VW bottle. I towed a 304cz with a bottle, and the safe speed iwas about 10mph slower than my ukonxl. The upon was 2 x the mass, but much farther from the axle to the hitch -- Dan, 5J At only 50 hp I wouldn't be taking it in the mountains (or hills, for that matter). Tom |
#58
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COBRA Anti-Sway Coupler
Gotta admit, it's a pretty cute idea. (Horsepower deficiency aside.)
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