A trailer for towing by a power vehicle is provided and generally includes a frame and a tandem wheel assembly. The frame forms an undercarriage chassis which the tandem wheel assembly is positioned there under. The undercarriage chassis includes a steerable rear wheel assembly, a steerable front wheel assembly, and an extension assembly moving the front wheel assembly between trailing position and a self-propelled position where the rear wheel assembly and the front wheel assembly are positioned to equally support the undercarriage chassis.

A trailer for towing by a power vehicle is provided and generally includes a frame and a tandem wheel assembly. The frame forms an undercarriage chassis which the tandem wheel assembly is positioned there under. The undercarriage chassis includes a rear wheel assembly, a front wheel assembly, and an extension assembly moving the front wheel assembly between trailing position and a self-propelled position. At least one of the wheel assemblies is powered by a selectively engageable drive assembly including a motor, transmission, driveshaft, selectively engageable clutch and hub, to drive the rotation of at least one of the wheels.

It is disclosed a system for leveling of load between front and rear wheels on a trailer, consisting of a rubber-torsion axle FIG. D with longitudinal members 4 which center is pivotally mounted to the torsion axles pivot arms 7. With a wheel in each end of the longitudinal members, the system is working as a complete bogie unit which has vertical spring motion effect, as shown in FIG. B. For trailers with no need of such spring motion effect, the longitudinal members can be mounted direct to the inner tube 9 in the rubber-torsion element.

A trailer for towing by a power vehicle is provided and generally includes a frame and a tandem wheel assembly. The frame forms an undercarriage chassis which the tandem wheel assembly is positioned there under. The undercarriage chassis includes a rear wheel assembly, a front wheel assembly, and an extension assembly moving the front wheel assembly between trailing position and a self-propelled position. At least one of the wheel assemblies is powered by a selectively engageable drive assembly including a motor, transmission, driveshaft, selectively engageable clutch and hub, to drive the rotation of at least one of the wheels.

A trailer for towing by a power vehicle is provided and generally includes a frame and a tandem wheel assembly. The frame forms an undercarriage chassis which the tandem wheel assembly is positioned there under. The undercarriage chassis includes a steerable rear wheel assembly, a steerable front wheel assembly, and an extension assembly moving the front wheel assembly between trailing position and a self-propelled position where the rear wheel assembly and the front wheel assembly are positioned to equally support the undercarriage chassis.

A trailer for towing by a power vehicle is provided and generally includes a frame and a tandem wheel assembly. The frame forms an undercarriage chassis and the tandem wheel assembly positioned under the undercarriage chassis. The tandem wheel assembly includes a rear wheel assembly and a front wheel assembly. An extension assembly is provided and moves the front wheel assembly between trailing position and a self-propelled position where the rear wheel assembly and the front wheel assembly are positioned to equally support the undercarriage chassis.

A trailer for towing by a power vehicle is provided and generally includes a frame and a tandem wheel assembly. The frame forms an undercarriage chassis and the tandem wheel assembly positioned under the undercarriage chassis. The tandem wheel assembly includes a rear wheel assembly and a front wheel assembly. An extension assembly is provided and moves the front wheel assembly between trailing position and a self-propelled position where the rear wheel assembly and the front wheel assembly are positioned to equally support the undercarriage chassis.

A trailer for towing by a power vehicle is provided and generally includes a frame and a tandem wheel assembly. The frame forms an undercarriage chassis and the tandem wheel assembly positioned under the undercarriage chassis. The tandem wheel assembly includes a rear wheel assembly and a front wheel assembly. An extension assembly is provided and moves the front wheel assembly between trailing position and a self-propelled position where the rear wheel assembly and the front wheel assembly are positioned to equally support the undercarriage chassis.