Took a while to think through the best mounting option for the crane. There are three things that needed to be considered.
1. Vertical load down. This is by far the easiest force to resist, as the structure supporting the mezzanine is already in place, transferring the load down the vertical beams to the slab.
2. Rotation. A single mounting point with an arm extending out creates a significant bending moment. Trying to resist this force is tricky- a C section beam is not good to resist this. However, I am going to ignore this force, and assume that rotation is unrestricted. This then means point 3 is very important.
3. Vertical load up. If the front of the crane (mount) is pushing down, and that cannot go anywhere (it is a solid beam), then the back end of the mounting point is trying to lift. This was the force I was most concerned about, and the solution was a second beam that distributed that load over a number of bearers.
How much load? See if I can work it out with rusty mechanics. The arm is 1000mm long (close enough), and at that length has a maximum loading of 230kg. The base plate is 250mm, so therefore the vertical load will be 920kg. This already has the flooring on top, so the weight of that can be subtracted. Let’s estimate it is the weight of a single sheet of redtongue (it’d be more, but as there are joints that will decrease the overall effect). A sheet weighs 50kg (I knew the damned things were heavy), so that drops the overall load to 870kg. This is spread over 4 joists. So each one is being lifted with a 220kg load (rounded up). More than I am comfortable with, so it would be worth reinforcing the floor with a couple of beams to the ceiling – given that directly above is one of the main ceiling frames. In the meantime, this is the maximum permissible crane load. If I restrict the crane to lift a maximum of 112kg, this means each floor joist carries a vertical load of 100kg. That sounds pretty good as a safety factor. Any weight added to the floor above increases the permissible load, and instead of factoring that in, that just adds to the safety factor, rather than used to permit a greater load.
To start, I took a jigsaw and cut a hole in the flooring to the size of the plate. I wanted to mount the crane directly to the beams, not the floor. There was another reason for this – the crane has a 2200mm range of movement, and as there isn’t that much head room, dropping down 120mm or so to the beam gained some operating range as a bonus.
After marking the position of the first set of holes, these were drilled, and the plate bolted in position.
Then, from underneath, I added a second beam that spanned 4 joists. This was screwed into position, and bolted to the mounting plate. Screws are fine in this case as the load is upwards. For that reason, the crane can only operate when it is on the side of the hole. Best restricted to 45 degrees either side of the hole when carrying a load to ensure the rear beam is only loaded upwards.
Once the base was secured, it was time to assemble the crane itself.
The vertical beam is bolted to the base flange. The base flange is mounted on a short post that has an angled thrust bearing at the end to carry load. Curiously, the grease nipple on the lower section is nowhere near the bearing it is meant to grease. Makes me suspicious the Chinese stuffed up reading the plans, as where the nipple is located just under the flange would be just about the perfect distance in, if only from the other end. Either that, or you are expected to fill the entire void with grease. Possibly, but as there is a hole at the bottom (underneath), I would expect over time (or on really hot days) for the grease to find its way down and out, dripping all over the ground floor. Might have to plug a cork in the hole, then get greasing. But seriously, even if left dry, this will not be getting enough use rotating around the base for grease to be needed.
The horizontal arm is bolted to the top, then the ram bolted between the two. It is a mechanical, hydraulic (oil) 3 tonne ram, with a really good operating range.
Finally, the extension arm with the hook is added, and secured at the 230kg point (extended over the hole). A chain hoist hooked on (temporarily, until the electric winch arrives)
It looks the business, and the first tests worked well. So then I lifted some serious loads up (around the 60-70kg range). Yup. Works.
So then I moved onto lifting a bunch of crates I had waiting up to start clearing some of the ground floor space.
Lifting one of my original entertainment cabinet side units (and a bit of a selfie at the same time). After the entertainment unit was decommissioned (marking the end of CRT TVs), it became a tool cabinet in the previous shed, with the centre section being a tool sharpening station. This time around, the cabinets don’t fit the look and feel of the ground floor, so they are heading up to the relaxing section of the upper floor (the what?!!) Hmm – giving the game away a bit……. more on that in time
The two outside cabinets look good up there, so will be used to store woodworking books, some display items etc. But what will happen to the centre section? No longer required for a TV, no longer needed as a sharpening station. It might be time for my carefully made entertainment section to meet Mr saw, and separate the top section that is no longer very useful, from the two cupboards that could still be utilised – perhaps under the new sink. Just thought of that – interesting.
Filed under: Shed, Shed Build | Tagged: Chain Hoist, Crane, Jack, Load, TV Cabinet | Leave a comment »