Device+

As we found the unstable problem, we added two supporting bars to the device, the idea was similar to the child bicycle with two supporting bars at the rear wheel. One horizontal bar was welded at the bottom of the device with two supporting bars at both sides. Both supporting bars got wheel at the bottom, so they can stop the device falling, and wheels can make dog easily carry the device. After I welded two supporting bars to the horizontal bar, I found I could easily break the junction, so I decided to add two additional bars at the corners, to make a triangle at both corners, and that made the device strong enough. To make the device have a nice looking, we painted it in black.