Well, that is how a lift should operate, I think. There may have been some "creative editing", just sayin'.... But the design should work, in theory. Couple ideas to add, definitely would look at load rating of whatever motor is being used, a gear reduction wench seems ideal. Strong but slow. Like Me... I would want to go to floor with wench. If you could contain those cables to prevent anything from getting caught up or damaging cables, probably a good idea. Also in the unlikely event that a cable should fail while under load, this could be a life saver. I would want some type of limit switches for top and bottom to prevent torqueing the entire rig into oblivion in case of operator or control switch failure, or causing a tangled rats nest by over un-winding. An amp sensing cutout or circuit breaker could prevent catastrophic failure in case of a bind or obstruction, similar to garage door opener. A lock bar with a switch to secure it at top and not allow motor to operate until lock bar is manually unlocked, forces you to pay attention and focus on operation. Getting the cables and pulleys and winch all synced up may be a little touchy, and may require some adjustments as things break in and stretch and settle and expand or contract. Keeping the tension even at all four cables will be important to lifting without binding, or unwinding into a tangle if binding while lowering. Obviously, trailer level and plumb will be critical at build/install as well as when using.
This is where the happyjack style has the advantage. All four screws are synced up via chains and sprockets and have positive lift and lower, gravity isn't relied on to provide tension and each screw should be able to overcome any drag before a bind occurs. Also, there is not the "loaded spring" danger, and getting your shirt tail caught in the works is less likely. Trailer level is less important. You also have infinite lift and lower within the limits. You can lift an inch or fifty inches or anywhere between. A lot less moving parts and the slop that each brings to the party. If a person could copy this system economically, then you'd be doin' your business in high cotton.
Sorry, didn't mean to ramble. Again.
McDave
I may have just had a minor epiphany...or a stroke, but if a human being were to use chain and sprockets instead of cable and pulleys, getting and keeping synchronization should be a lot more achievable... gas struts to provide positive down force at all four corners might keep tension even enough to prevent binding....
Hmmmm....
