Tham khảo tài liệu 'mcgraw-hill - robot mechanisms and mechanical devices illustrated - 2003 part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | The Romans extensively used two wheeled carts pulled by horses. Pull on the right rein and the horse pulls the cart to the right and vise versa. The two wheels on the cart were mounted on the same axle but were attached in a way that each wheel could rotate at whatever speed was needed depending on whether the cart was going straight or around a corner. Carts got bigger and eventually had four wheels two in front and two in back. It became apparent though it is unclear if it was the Romans who figured this out that this caused problems when trying to turn. One or the other set of wheels would skid. The simplest method for fixing this problem was to mount the front set of wheels on each end of an axle that could swivel in the middle Figure 6-1 . A tongue was attached to the axle and stuck out from the front of the vehicle which in turn was attached to a horse. Pulling on the tongue aligned the front wheels with the turn. The back wheels followed. This method worked well and indeed still does for four wheeled horse drawn buggies and carriages. Figure 6-1 Pivot mounted front wheels 189 190 Chapter 6 Steering History In the early 1800s with the advent of steam engines and later electric motors gas engines and diesel engines this steering method began to show its problems. Vehicles were hard to control at speeds much faster than a few meters per second. The axle and tongue took up a lot of room swinging back and forth under the front of the vehicle. An attempt around this problem was to make the axle long enough so that the front wheels didn t hit the cart s sides when turning but it was not very convenient having the front wheels wider than the rest of the vehicle. The first effective fix was to mount the two front wheels on a mechanism that allowed each wheel to swivel closer to its own center. This saved space and was easier to control and it appeared to work well. In 1816 George Lankensperger realized that when turning a corner with the wheels mounted using that .
