Co-ordinated cylinders lower the load

By feeding four hydraulic rams in series, with a difference in diameter between alternate pairs, it is possible to evenly lower a vehicle load tray to the ground and then lift it again, without use of electronics or flow dividers. The idea greatly eases the task of van delivery drivers, as well as designers of lifting equipment of all kinds. Razorback vehicles were originally invented in Australia some seven years ago, but are now being made in Solihull. The basic idea is to take a suitable front wheel van or pickup truck, and convert it so that the load tray can be fully lowered to the ground and raised again. The four hydraulic cylinders are of two types: 2.25 ins (57 mm) in diameter and 2 ins (51mm) in diameter. The load tray is attached to the ends of the piston rods, emerging downwards from the cylinders. Each cylinder is fed in series. When lowering, oil first goes to the full cylinder diameter end of a 2.25 in diameter cylinder at the rear of the load tray, and the oil pushed out on the piston end of this goes to the full diameter end of a 2 inch diameter cylinder on the other side of the load tray. Since a smaller volume of oil is pushed out of the piston end of a cylinder per unit displacement than the full diameter end, it is necessary for the second cylinder to be of smaller diameter than the first, in order that their piston rods move out at the same rate. The oil from the piston rod end of the second cylinder then feeds the full diameter end of another 2.25 in diameter cylinder at the front end of the load tray. The load tray thus lowers faster at the rear end than the front. The oil from the piston rod end of the third cylinder then feeds the full diameter end of another 2 in diameter cylinder at the front, so that the rods from these two cylinders also move together. Lifting is by reversing the flow, starting with oil being fed into the piston rod end of the fourth cylinder. If the four cylinders were each of decreasing diameter, it would be possible to make all four move at exactly the same rate. There are currently 130 Razorback equipped vans on the road in the UK. The pickup version is being launched in the UK about now. Many more can be expected to be seen on the road in the near future. Razorback Vehicles Corporation Pointers * By feeding four hydraulic cylinders of different diameters in series, it is possible to evenly lower a load tray to the ground and raise it again. * By use a large, small, large, small, combination, it is possible to co-ordinate rams on all four corners, so that the rear is lowered evenly, but more quickly than the front. * If the four cylinders were each of successively decreasing size, it would be possible to make all four move at the same rate.