52, Serj has made Danmar's stance pretty clear. That's why I really like dealing with them..they take responsibility, and have a vested interest in owner safety.
On the stress side of things (and by no means definitive), if you were setting up a finite analysis model (we do almost all our product design this way) you would want to model a loaded Maxjax lift at say 3000 and 6000 lbs, model the range of play in the sliding assembly, and column deflection under these loads, and the tolerance of the flow divider. Then you would introduce the constraint of a locking bar. You would need to model the difference in distance between the column bottom and top under the various loads. When you lock the columns together only on the moving assembly, you would find that vertical lift forces were being transferred to horizontal forces between the columns. Under certain conditions, I'm sure these forces could exceed the mechanical anchor spec set in 4" concrete. That's a lot of variables introduced under install conditions, and as a manufacturer, I wouldn't touch it.
I'm interested to see your ideas on the ladder locks..something I'd love to see protecting both lift and lower. Even with ladder locks, I'd still use my short rise stands.
The title of your thread is peace of mind under the Maxjax. I worked back in my student days under contract with Bell, and did oil and chassis lube on all their cars, vans and line trucks in the local shop. This involved a lot of lifts, often alone in the evenings. After installing and using the Maxjax and learning about its hydraulic system, the only concern I have is hose failure and how to react to it.
My process for lifting (call it peace of mind) goes as follows.
1. Center the vehicle at the lift points. I don't have weigh scales so honestly don't attempt mass calculations. The pillar behind the driver is a good bet. There are a ton of good reads out there on proper vehicle centering.
2. Locate frame lift points. This always is the most time consuming process for me as I have 3 and 6" extensions, and truck pads, so always try to find the best (safest) combination. The truck rail pads are always nice when you can use them as the pad cannot slip off the lift point.
3. Lift a few inches and check to see that the pads are where they are supposed to be.
4. Lift until tires are clear, go to the front or rear bumper and try to introduce as much push and twist as I can to check lift points.. Check to make sure the arm locks are engaged and locked. Do a quick scan for leaks.
5. Making sure no one is standing at the front or rear, I crouch down and watch carefully as the lift is done. I do the same during lowering..watch the underside to make sure lowering is level, lock bars are out, etc.
6. Depending on the job, throw two, or four short rise stands under and tension them with light loading.
I'm sure others will comment, but proper anchor installation and those 6 steps make lifting about as safe as it can be without any need for mods. Making sure that you fully focus during lift and lower is critical. If you're tired, leave a lock bar in and start lowering, a vehicle accident can happen in a matter of seconds. Stopping to focus, and watching carefully is so important.
If a hose fails, you need to mentally rehearse the correct action. In most cases this would be to immediately hit the lower lever so the good side will drop as well. If a column velocity fuse engages, the "bad" side will stop lowering, so should you.
One of the fellows who spray foamed my attic ceiling is now dead after a vehicle he was working under fell on him. It slipped off a jack. Safety under a vehicle is something we all need to remind and rehearse, every time we work under a vehicle.
Whatever, I could give a rat's ***. In my career I dealt with my share of engineers who worked for me and the first words out of their mouth to an old operator or maintenance hand was to the tune of "I'm an engineer and I know everything and you are an idiot." He came across the same way. If you're going to lay down some small arms fire don't be surprised when someone responds with a 115mm.
OK, internet tough guy.
