This technique is implemented for many years in all lifters European, providing a positive and negative aspects. Positive: The positive part of this, is security, usually, very difficult is that in any part of the route, moving parts can fail causing a collapse of the vehicle thanks to which this guidance by both columns and at the same time situated anywhere on the entire route over your screw without end. Possibilities that one day fails and splitting a worm are very low, being over others as a break in the parties that support the weight of the vehicle. Negative:-large current consumption: the entire movement of ascent and descent, occurs through movements fractionated by bolts, sprockets and chains. This makes requiring large peaks of correine both in ascent or descent. This is one of the reasons of because these elevators were marketed with three-phase Motors 380v / 400v and still weren’t able to develop great efforts. When they tried to transform to 220v single-phase motors, did not work in all their duties, mainly if the vehicle was something heavy, and stopped the rise in any part of the race, then I had no strength for reanudad a new ascent, forcing down the vehicle to the ground and starting a new ascension. -Reduced maximum load capacity: normally these elevators were traded in order to uses with vehicles not exceeding 1,500 Kg the Basic or 2,500 Kg special ones. This has created for many decades, that the workshops be limiting in terms of vehicles or loads of these, especially industrialists. We remember having served elevators our new calling us alerted by need for urgency, because they had experienced cases with elevators with well-known brands in Europe and Spain sold by the same brands and manufacturers with cases as having a vehicle of type tourism with the boot over charged and elevator didn’t have enough force to elevate this.