It doesn’t take an engineer to see that from a structural stand point the four poster is a much more stable base for a multi ton load 20ft long and 6ft wide. The thing that always bothered me about the two-post lift was the base. I haven’t gotten to the stage where I’ve really looked into the mounting of the two-posters but from the questions I have asked it appears that the base is just mounted to the concrete floor with anchors. Loading a standard four-inch concrete floor with that much weight concentrated in such a small area seems risky at first glance. The leverage that the cantilevered load can impose on the anchors looks like it would tear the anchors right out of the floor if one got hold of the bumper and started rockin’ it a bit.
Now if you were to bust up the floor and pour a footing a few feet deep and a few feet square with threaded rods imbedded in the footing then I might feel safe with that.
I first noticed the two-post adjustable arm floor mounted lift roughly a couple of decades ago when they began to populate the commercial garages and the stables of the leisure class do-it yourselfer. I believe the four-post lift predated them by a few years and was popular with the working class do-it-yourselfer cuz they were relatively inexpensive to manufacture.
The hydraulic adjustable arm type of lift was making the scene around the time I first started driving, i.e., mid to late 50’s. Pryor to that almost all of the lifts that I remember seeing were the twin rail hydraulic lifts which were buried deep in the ground. Can’t forget the grand daddy of them all, the grease pit.
So has any one ever heard of an instance of the two post lift pulling the anchors out of the floor???
Denny Graham
Sandwich, IL
