Why are dual axle TTs made with the wheels in the middle?

[Damdifino]

Why don't you see trailers with tires at the four corners and a steer axle being in front, like an old toy Radio Flyer or even older Conestoga wagon?

[totaldla]

There's no technical reason why manufacturers can't - its just cheaper to do it the same old way.

It would be much more stable, and much easier on the tow vehicle to have a 4 wheel wagon suspension. Add rear steering and you'd eliminate outcast.

The technology is available, (rear steering common in Italian busses), but it costs more.

[Hannibal]

Like our 28RLS Jayco, 2/3 of your trailer is in front of your trailer's axles. This makes for a very stable rig. Too many travel trailers have axles too far forward in an attempt to keep tongue weight down so unsuspecting buyers believe their lightweight tow vehicle can safely tow it within the TV's weight ratings. Then the quest for sway control begins. Your rig has one pivot point. A wagon type rig would alleviate the tongue weight issue but it would add another pivot point making backing the rig a challenge.

[Hannibal]

Towing a car on a dolly or on all four behind a motorhome is doing exactly what you describe. Here's about as close to the little red wagon concept as you'll likely get with an RV. Backing these things into a spot on the right would be cause for divorce.

http://fifthwheelst.com/automated-safety-hitch-system.html

[3oaks]

And backing up, forget about it

? Apparently there're aren't any farmers replying to this thread.

How do you think we got the hay wagons into the barn all these years? :R

Definitely good for highway use though. 😉

[nickthehunter]

skipro3 wrote:
Because you can not back up a trailer like that...

You can back up a trailer like that. It's called a "dolly lock". It's done every day of the week on double bottom gravel trains.
You may also be amazed to know they also go around corners just fine.
A dolly lock would let you to back up and RV the same way. I'm not saying it's practical, just possible.

[Terryallan]

DanNJanice wrote:
Good question.

I am less sure about the stability argument, as I see double and triple semi trailers all the time, they seem to work fine.

I'm thinkin they have lack of stability as well. That is why they are called WIGGLE WAGONS

[rbpru]

The reason the axle are where the are is because it is the best placement for a travel trailer; at the lowest cost.

Semi-trailers and boat trailers work best near the rear because that is what is best for them.

Four wheels wagons have been used on the farm for years but they are more expensive and do not seem to offer any significant advantage in the TT industry.

[myredracer]

Problem is a large difference in turning radius and tracking for the front (steerable) axle and the rear axle. Best example is semi-trucks and trailers as the two diagrams below show. In a tight right-hand turn a semi-truck and trailer typically swing as far left as they can just before a turn and take up 2 lanes getting thru the corner. It would be very difficult for a TT owner - expect a lot of accidents. Commercial truck drivers are trained and RV owners aren't.

[hedge]

the larger gravel truck pups are built just like this and the drivers manage to back them up. Quite often they back them up so that the trailer is beside the truck so they can then dump the truck, it's pretty cool to see.

ps, back in my younger days I worked as a gravel checker.

[prichardson]

As others have said - handling. A wagon configuration does not track well going forward (the higher the speed the worse it is) and it is nearly impossible to back.

[JIMNLIN]

Hard to imagine a rv trailer with wheels at the corners on a 35' long trailer. It would take the whole intersection to get around a corner....making it impossible to pull it around campgrounds and forget backing any where but in my 22 acre hay meadow.

Lots of old hay trailers still around but the ag industry modernized and gave us hay trailers with the wheels towards the the center. Much much easier to maneuver (forward and backing) and can be pulled down the road at highway speeds.

[mleekamp]

I would add that axles in "middle" of a TT allow it to PIVOT when turning...allowing easier backing up as well.

The farm trailer discussed here is correct as well...unhitch and its stable. Not intended for "major" highway travel.

Lastly, as I'm sure many here are, you get "really good" at backing a TT after doing it so many times. It's amazing how you can literally pinpoint exactly where you want to be, and put 'er there by knowing you pivot points.

[Mortimer_Brewst]

mike-s wrote:
Why not just mount an axle on the roof, where the brakes/bearings/tires would never wear out?

You might be on to something here. Would this make the trailer usable in Australia as well?

[mike-s]

theoldwizard1 wrote:
Eliminates porpoising on rough road. That is why farm trailers have axles set apart.

"Porpoising" has nothing to do with it, there's no suspension on a tractor for that to be an issue. On farm trailers because you can simply unhitch them while loaded without needing to do anything to keep them stable.