Jerry Martes wrote:

"SteveB" wrote in message
...
Yesterday, while in Cedar City, Utah, I saw a modern Basque shepherd
shelter. For those who don't know what that is, it is a trailer for
staying in the mountains and caring for sheep. They are about 16' long or
so, boxy, except for a half circle roof. Door always in the rear.
Traditionally, they are green. This one was modern, and clad with the
aluminum sheeting just like a modern travel trailer.

My questions come from the suspension. On every one of these, I have seen
four wheels, two on each axle. Just like a toy wagon, or an old west
wagon. The front wheels are attached to a tongue, and have a tie rod
turning system, or in the old ones, just a pivot point. I'm sure there's
a simple explanation for this choice of wheels.

I have also noticed that this is about the only rig I have seen set up
this way. All the over the road trailers, except semis have wheels in the
middle. It probably has a lot to do with tracking and stability.
Probably stability at highway speeds, too. I have seen the four wheel
front yoke setup on low speed farm haulers, too, particularly hay wagons.

Anyone care to enlighten me?

Steve

Hi Steve

Are you are asking about trailer design because you are thinking about
building a trailer with the axels separated by an appreciable percentage of
their width? If so, research "ackerman".
The front wheels of a two axel trailer need to *toe out* while turning to
avoid scraping or scrubbing. That can get complicated and is a good
reason to use only 1 axel on a trailer.

Jerry

No, he's referring to a "full trailer" with axles located front and rear
and typically steerable, same geometry as a car, but without any drive
source.