HOW TO HANDLE

[Bruce H]

We all know that the flight of a golf ball is more stable because of the dimples. Perhaps if an egg had dimples it would be less inclined to sway at high speeds.

[Dan Meyer]

HOW TO HANDLE TRAILER SWAY

[>snip<

[b]If your trailer doesn't have brakes, then your alternative is to slightly speed up the tow vehicle to try to get the trailer to start behaving. Be careful when doing this and it may not be the best idea if you are already going faster than you should. If the cause of the sway was your speed, this might just make matters worse.

No no no no no. NO!

Don't speed up and try to drive out of trailer sway! Ever!

Go to http://towingstabilitystudies.co.uk/stabil...tudies_game.htm and work the simulator. It will help you to understand what part speed has in trailer sway.

How you load the trailer also has an large effect. Be sure at least 10 percent of the trailer's weight is on the tongue. This is one of those cases where more is better. 15 or 20 percent of the trailer's weight on the tongue would be even better from a stability standpoint.

Also, make sure your tires are properly inflated - both on your tow vehicle and trailer. Don't use passenger car tires on your trailer if it is prone to sway. Tires built for trailer towing service will help prevent sway due to their stiffer sidewalls.

If you tow enough, you will someday experience trailer sway. If you are lucky it will not be a severe problem.

Again, if your trailer begins to sway the best way out is to SLOW DOWN!

-- Dan Meyer

[Andrew Gibbens]

...that tue Euro manufacturers tend to put the axel a bit further back. might it be a "center of gravity" thing?

Actually, it's the other way around - Euro manufacturers put the axle further forward so that tongue weight is reduced. This is because we generally use lighter tow vehicles that cannot accept high tongue weights.

In Europe a tongue weight of 4-7% is considered 'safe' and if you look at big tow vehicles and you divide the max permitted tongue weight by the max permitted trailer weight, you often get a figure nearer 4%.

With lower tongue weights, sway will happen at lower speeds - which is one big reason why all European countries have lower speed limits for trailers. This makes it surprising that until very recently, sway control was unusual on European trailers - now a friction-damping coupler tends to be found on upmarket trailers.

One reason there is a critical speed above which sway will start is that on most trailers the airflow over the front/top edge produces aerodynamic lift, so the faster you go, the greater the lift and so the less the tongue weight. You will see that almost all European trailers have the front of the trailer angled back fairly sharply - this reduces the aerodynamic lift and so increases the critical speed for sway - European trailers are towed near enough to their critical speed that this design feature is needed.

Andrew

[Pete Dumbleton]

A longer tongue can mean lower tongue weight (longer lever requires less vertical force on end to have more torque around axle) but it also depends on where the Center of Gravity is -- If the longer tongue moves the COG forward, then tongue weight will increase.

Suffice it to say that Euro trailers are designed to a dissimilar model that produces a lower tongue weight in a properly balanced rig.

[Andrew Gibbens]

Anyone who wants to experiment with tongue weights can use this trailer balance spreadsheet - it was written for teardrop builders to use, but if you mentally change the illustration to a travel trailer, the physics is just the same!
Trailer Balance Spreadsheet

Lengthening a tongue doesn't make much difference to tongue weight, unless very heavy things are put on the lengthened tongue - it might change a 10% tongue weight to 9% or, at the extreme, to 8%.

Andrew

[Pete Dumbleton]

It's proportional -- If one were to double the tongue length, one would halve the tongue weight... (and also halve the effects of trailer sway on the rear of the tow vehicle; that's why gravel trailers on the US West Coast use tongues that are almost as long as the trailer itself -- I need to find a picture of one).

[ddayton]

It's proportional -- If one were to double the tongue length, one would halve the tongue weight... (and also halve the effects of trailer sway on the rear of the tow vehicle; that's why gravel trailers on the US West Coast use tongues that are almost as long as the trailer itself -- I need to find a picture of one).

Pete - here is a picture - does not do justice to the full length of the tongue but gives the idea.



Don

[Roger C H]

It's proportional -- If one were to double the tongue length, one would halve the tongue weight... (and also halve the effects of trailer sway on the rear of the tow vehicle; that's why gravel trailers on the US West Coast use tongues that are almost as long as the trailer itself -- I need to find a picture of one).

And here I always thought that gravel trailers have long tongues because of pavement loading.

But what are the aerodynamic effects of an unladen gravel trailer?

[Pete Dumbleton]

Pavement loading is also a factor -- I noticed that some are adjustable in length -- Notice that because the trailer has more than one axle and the load is pretty much balanced on those axles, there is actually very little tongue weight (except the weight of the tongue).

BTW, that proportional leverage effect can be powerful -- After a near-serious sway incident with my Dodge truck and Scamp, one thing I did was shorten the overhang on the truck (moved the receiver hitch two inches forward and moved the ball mount two inches forward by drilling a new set of pin holes in the bar -- Those four inches made a lot of difference, both in less sway (when I tried to induce it with steering) and improved backing.

Of course, folks who put on a longer ball mount for clearance purposes are going in the wrong direction...

I'd be careful about trying to get too much tongue weight because that could also lead to instability problems -- There's an upper limit in that 10-15%!

[Jim Bennett]

And here I always thought that gravel trailers have long tongues because of pavement loading.

But what are the aerodynamic effects of an unladen gravel trailer?

I know with some dumptruck/trailer combos the reason that the tongue is so long on the pup (which gets pulled behind a gravel truck) is so that the driver can jackknife the trailer 90 degrees or a bit more, then they can dump the contents of the truck without unhooking. At least this is what I saw lots when I did roadwork many years ago.

Is that the European or African gravel trailer.

[Weinel, Alan]

I'm sure that dumping a gravel truck will cause more than just a flesh wound.

I know with some dumptruck/trailer combos the reason that the tongue is so long on the pup (which gets pulled behind a gravel truck) is so that the driver can jackknife the trailer 90 degrees or a bit more, then they can dump the contents of the truck without unhooking. At least this is what I saw lots when I did roadwork many years ago.

Is that the European or African gravel trailer.

[Pete Dumbleton]

There are a lot of advantages to a long tongue in terms of handling (forward and backwards) and sway -- The disadvantages come in overall length problems, parking, site fit, city driving, etc.

I often wonder why they are so common in states like Calif, WA, OR and ID and not often seen Back East -- I have no idea of the Canadian distribution.

BTW, as pointed out to me in a PM, we have been talking about tongue length without defining it -- I personally view it as the coupler to axle length, but it's also correct to view it as coupler to Center of Mass (usually somewhat forward of the axle) -- Some may view it as coupler to trailer body, but that's not good for much, IMHO, in terms of handling, proportions, etc.

Overhang is the ball to TV rear axle, which is very short on 5W/goose-neck hitches and why they function so well.

PS I remember from my days in a former life living in Florida (Tampa area) that one did NOT mess around with gravel trucks on the road -- They were always in a hurry, trying to get in one more payload during the workday and carried a lot of mass, even when empty -- People would pull out in front of them and get seriously hurt! Doubly true when pulling a trailer, of course!

The Northern reaches of Dale Mabry highway, where there was a lot of traffic on the then two-lane parts was esp dangerous in late afternoon, with tired truck drivers trying get one more load down from further North and Moms picking up the kids after school.