Tongue weight in Europe is around 7%

[rvtrailerpuller]

I know I am going to get some super experienced folks in the U.S. criticizing tongue/hitch weights being less than 10%, but let's discuss this.
It seems the approach in the U.K. and Europe is to attempt to design and load a trailer such that the majority of the weight is just forward of the axle. Far less concern on the Eastern side of the Atlantic is given to a tongue weight over 7%. In the U.K. a tongue weight of 4% is the legal minimum and the goal is to be in the range of 5% to 7% of loaded trailer weight. Trailer speed limits over there are 60mph maximum and there is less emphasis on weight distribution hitches. The main concern is to not load up a trailer with a concentration of weight in the far front and the far back just to accomplish some goal of a specific target tongue weight. They are more concerned with "yaw inertia" that a trailer with both a heavy front and rear would have and relatively low weight in the center over the axle. The goal, again, is to concentrate the load just as close to the axle as possible and just forward of it such that the tongue weight ends up in the 5% to 7% range.
I tow a really big trailer with a really big diesel truck with a Hensley hitch.
Perhaps this European and English style of trailer weight balancing design accounts for the mysteriously fantastically stable trailer and the mysteriously horrible towing trailer surprises that occur in the experience of some of us who have towed a large variety of trailers here in the U.S. It may be more than just a huge tongue weight that keeps a trailer stable and free from sway.
The conceptual difference is that of holding heavy and equal objects in each hand at arms length and swing your body around, and then try to stop it. Then do the same holding the weights to the chest. You can easily stop yourself from the inertia of the spin when the weights are not concentrated toward the ends of your trailer, but rather toward the center near your chest (trailer axle).

[rvtrailerpuller]

Check out this as an example of how trailer (caravan) manufacturers design trailers in the U.K. The propane tank is not in front - it's in the middle. The spare tire is not in back - it's low slung under the trailer just in front of the axle. Common GVWR is close to 2,700 lbs. Very liveable trailers/caravans. Just one example of manufacturer, among others: http://www.baileyofbristol.co.uk/caravans/http://www.baileyofbristol.co.uk/caravans/

Moderator edit to re-size pictures to forum limit of 640px maximum width.

[RobertRyan]

Nomad -1 wrote:
The fact that in Europe the distances travelled by road are far less than here is not mentioned in these opinions. Very rarely would you see travels of over 500 miles.

Really does not have much to do with it. We get people here doing a 1000 miles in one. In Europe you get people doing about 1500 miles going from Northern Europe to Spain or Greece. Rough dirt roads are not the forte of European Caravans, still this family took this Adria Altea 16,700 miles around Australia.They can be unstable on very rough ground not just graded dirt.

A common concern about European-built caravans is their ability to stand up to harsh Aussie conditions, but an Adria caravan that has just completed a gruelling 27,000km(16,700miles) road trip proves they can be as tough and reliable as their locally-built counterparts.

[Nomad-1]

The fact that in Europe the distances travelled by road are far less than here is not mentioned in these opinions. Very rarely would you see travels of over 500 miles. If you were to travel the distance in Europe between like Washington and Miami, in Europe you would go through several countries/borders. Our needs are very different. That is why our needs are vastly different. The short distances travelled in Europe is directly related to all the higher costs of motoring. Small cars= small trailers+narrow roads= different needs.

[BarneyS]

Marinermark wrote:
To add to the confusion, the Coast Guard recommends 5-7% tongue weight for trailered boats. When I started RVing, after boating and teaching the CG Auxiliary Trailering class for many years, I wondered about the difference vs. our RV %. I guessed it had something to do with the different shape-dynamics or inherent weight distribution. I never really turned up an explanation, so it's interesting to see that Europe has a similar number for RVs.

Boats tow better because the wheels are placed more to the rear of the trailer. TT have the wheels more towards the middle in most cases.

To see the effects of tongue weight easily, take a fully or partially loaded (makes no difference) wheeled garbage can. Try pulling it with the handle just barely or slightly more off of vertical. You will not get far before it starts to wobble out of control. Then lower your hand so the handle is lower to the ground. The lower you get, the less tendency for the can to wobble. I don't know the physics behind it but this shows what the lack of tongue weight will do.
Barney

[RobertRyan]

rvtrailerpuller wrote:
American trailers are loaded as if they are dumbbells, or barbells. European trailers are loaded with the heaviest objects toward the center, albeit still ahead of the axle. I think this is more like the average boat on a trailer.

Same as in Australia but have a WDH or sophisticated suspension to offset that.

[rvtrailerpuller]

There are differences in how trailers are loaded. In North America it is very common, for example, to hang a spare tire and possibly a few lawn chairs and an extra ladder all off the rear of the trailer. Then, to compensate and get the desired tongue weight, the trailer is loaded heavily in front. In Europe according to what I've read, it is quite uncommon to add weight to both the rear bumper and the front of the trailer. Spare tires are commonly carried directly underneath the trailer not too far from the axle to centralize the load. American trailers are loaded as if they are dumbbells, or barbells. European trailers are loaded with the heaviest objects toward the center, albeit still ahead of the axle. I think this is more like the average boat on a trailer.

[Marinermark]

To add to the confusion, the Coast Guard recommends 5-7% tongue weight for trailered boats. When I started RVing, after boating and teaching the CG Auxiliary Trailering class for many years, I wondered about the difference vs. our RV %. I guessed it had something to do with the different shape-dynamics or inherent weight distribution. I never really turned up an explanation, so it's interesting to see that Europe has a similar number for RVs.

[RobertRyan]

There are much more to it than what the eyeball can see...even a trained eyeball....

So much is taken out of context...as stated...are their trailers like ours over here?

Are their TV's like our over here and note that even though they look the same,
sometimes, many times they are not.

I've always wondered how a North American setup would tow over there? I

In Australia we have Australian, US, South African and European Caravans. Generally the RV's are built for the use they are intended for. US and European caravans for relatively smooth roads. European ones are very light but can copw with some rough roads( South African "European Caravans" do not have a problem) US Caravans much heavier but need WDH Hitches. Australian caravans have either WDH hitches or suspensions that eliminate the need for them.

[rvtrailerpuller]

Ron Gratz wrote:


My first TT was an ABI Award made in Canada and based on a British design. It was 27' long, had a loaded weight of 5000#, a loaded tongue weight of 500#, and towed very nicely with a 1994 Ford Explorer using a Drawtite WDH and a single friction sway bar.

Ron

This was a well designed and balanced trailer, obviously. The Ford Explorer of the era weighed less than the 5000 lb and 27 foot long trailer, and being towed and handled well with a single friction sway bar, this must give credit to good trailer design and weight balancing. Well done, Ron!

[rvtrailerpuller]

OK, so why does a figure skater spin faster if he/she pulls the arms in toward the body?
http://www.youtube.com/watch?v=EbHwwQ7vksA
I still like to think, in my pea sized brain, that a hypothetical trailer with absolutely no mass anywhere other than split in two equal points, one in front of the axle right up at the coupler, and in the other part on the trailer bumper, but yet would have a theoretical 10% greater load on the coupler/hitch, this trailer would be inherently unstable because of the effect of the opposing pendulums on either side of the center of gravity just forward of the axle.
Consider the opposite theoretical trailer with absolutely no mass forward of the center of gravity, and absolutely no mass to the rear of the center of gravity, yet this center of gravity is just forward of the axle sufficient to yield a 10% load on the hitch. I know this is stupid and impossible in the real world, but wouldn't this hypothetical trailer be more stable than the one that would tic-toc wildly as a metronome out of control?
OK, now, I'll just sit back and try to recall my days in college physics class in 1970 and 1971. Those around me were spacing out on weed, and I was spacing out on physics.
So, back to spinning as a figure skater.

[rvtrailerpuller]

rvtrailerpuller wrote:

Ron Gratz wrote:


If you want to dig deeper into how tongue weight percentage is related to lateral force imposed on the ball, an attempt to explain the process is given in this post.


Ron

I just read the link you provided. To say my mind is blown would be an understatement. I wish I could understand it, but you definitely gave some science to the discussion.

Ok, I'm quoting myself, but I think that if a person were to actually read the entire thread mentioned in the above link, either or both of 2 things could happen. One could fully understand trailer design, and/or one could seriously have a flashback of all the great "trips" one may have had.
Seriously, though I think you could build me a great custom trailer.

[rvtrailerpuller]

Ron Gratz wrote:


If you want to dig deeper into how tongue weight percentage is related to lateral force imposed on the ball, an attempt to explain the process is given in this post.


Ron

I just read the link you provided. To say my mind is blown would be an understatement. I wish I could understand it, but you definitely gave some science to the discussion.

[mileshuff]

Another issue I've heard about RV'ing in the UK is that in-cab brake controllers are not allowed. Have to be independent of the TV. That leaves surge brakes the main option. Can anyone confirm if this is true? Surge brakes are common on boat trailers but rarely on TT's or 5'ers in the US.

[rvtrailerpuller]

This is great stuff. Thanks for the input.

[Ron_Gratz]

rvtrailerpuller wrote:
---The goal, again, is to concentrate the load just as close to the axle as possible and just forward of it such that the tongue weight ends up in the 5% to 7% range.---

I would suggest just one change to your statement -- the load should be concentrated as close as possible to the trailer's CG, rather than the axle.

The optimum distance from the CG to the axle is determined by:
1) the distance from the ball coupler to the trailer's axle(s),
2) the trailer's polar (yaw) moment of inertia, and
3) the trailer's mass

Tongue weight percentage is a measure of the ratio of distance from TT's axles to TT's center of gravity divided by the distance from TT's axles to the ball coupler.

The ratio is important because it is one of the factors which determine how much lateral force the TT might exert on the ball.
For given TT mass, polar moment of inertia, dimensions, and application of lateral force on the TT, there is an optimum value of tongue weight percentage which will minimize the lateral force which the TT imposes on the ball coupler.

When a right-directed lateral force is applied to a TT at a point behind the CG, two things happen:
1) the TT's CG begins to accelerate toward the right, and
2) the TT begins a counter-clockwise (when viewed from above) yaw acceleration about the CG.

The right-directed acceleration of the CG causes the ball coupler to tend to move to the right.
The CCW yaw acceleration of the TT about the CG causes the ball coupler to tend to move to the left.
With the optimum TW%, the right-directed acceleration of the coupler will be equal to the left-directed acceleration, and there will be little or no lateral force imposed on the ball.

If you want to dig deeper into how tongue weight percentage is related to lateral force imposed on the ball, an attempt to explain the process is given in this post.

My first TT was an ABI Award made in Canada and based on a British design. It was 27' long, had a loaded weight of 5000#, a loaded tongue weight of 500#, and towed very nicely with a 1994 Ford Explorer using a Drawtite WDH and a single friction sway bar.

Ron