Not to hijack, but saw this Higgins and thought you might find it interesting:
https://www.calguns.net/calgunforum/showthread.php?t=1417715

The 737 only weighs 45 tons (dry). For some reason, I thought it would be much more. You learn something new every day.

In terms of lifting cranes why aren't there:
*Steel-pole-lattice-support-system vehicles,to drive up on demand to help mitigate the final loading of that long frail wisp structure?
*A simple extension pole to support the last 1/2 to 1/4 section of the stalk where the majority gravity+load is located.

I tried to send Mr Higgins a private message.
But private communication seems no longer available with the new owners of this Pelican Parts dot com website.

Cranes are well outside my area of expertise. So are airplane structures. We all play our bit parts - someone gives me a crane with what they say is enough capacity, and I do not question that. Someone tells me where we can apply what loads to lift the aircraft, and I do not question that. I provide the equipment that connects the two - the spreader bars and slings seen in the video. Lots of guys doing their one little part and, viola, the aircraft is recovered and moved to where it can be inspected and, hopefully, repaired. That's where I really get busy.

Private messages seem to be no longer allowed on Pelican Parts Dot Com..

So perhaps some random engineer located in red China could steal this idea better.
Flying my personal privacy buttress.
http://forums.pelicanparts.com/uploa...1516340097.jpg

That pic didn't show on my last post.

You'd have to have an engineer work on that, John. As Dr. Higgins reports, cranes have known structural and mechanical capacities. We trust them. A triangulation is a new crane. They don't really do that. They using existing ones.

Pretty amazing what you can do with aluminum. A single M1 Abrams tanks weighs between 60 and 70 tons depending on the model.

The problem with your argument is this: if there's a suitable place where they could put the support crane that you have in your drawing, they'll just move the main crane there. You always want to have a crane closest possible to where the load is, the only reason that is sometimes problematic is due to unsuitable locations or other things being in the way. Cranes have immense capacities when the boom is raised high, it's when I have to reach out a greater distance horizontally that the capacity comes way down.

Heavy lifting cranes have always been interesting to me. It doesn't surprise me that there exists cranes that large but I always wonder what they are used for regularly; IOW, when a large jet doesn't need to be plucked out of a hole.

When I think of what a boom crane like that must cost, it would have to be used pretty regularly to even come close to amortizing for someone. As I was typing this, it occurred to me that it's probably borrowed from their nearest large port or harbor. I've never noticed a boom crane that large on a construction site. :cool:

The answer is that it is seldom something truly heavy that gets lifted, it's generally that the crane has to lift something a considerable distance from where it sets up. A 300 ton crane may only be rated to lift something as light as 8 tons, at the limits of it's reach.

Crane capacities are based on the lift distance from the center pin, the amount of boom extension, the amount of counterweights fitted, the direction of the lift, etc. There are charts for every crane that show the limits and they also have the ability to know what the load is and have computers that calculate the limits and prevent the operator from exceeding them. These limits can be overridden in some cases...

Mobile hydraulic cranes like the ones used the other day exist up to something like 1300 tons. They require a train of supporting vehicles, as they won't be fully assembled until they get to the site. The block may be carried separately, the majority of the counterweights will be carried separately, the pads for the outriggers, the rigging (spreader beams, etc.) and other stuff. A second crane will be needed to install these things on site.

The reason for that is simply the weight. A big crane weighs too much for the load limits on the highways. They typically have to get special permits to travel and this limits when and where they can go. When they get to the job site, they often are too heavy for the soil conditions encountered, both when they drive to where they need to make the lift and when the lift occurs, as the soil under the outriggers may not support the load. It's always a balancing act and you want to use the smallest crane that can get the lift done.

These cranes are rented out by the hour. A crane company will buy one if they feel that they can rent it often enough to make a profit on it. Around here, the last time I was involved in that arena, 300 tons was what we had available. Beyond that, you were forced to use a crawler crane, which ups the cost considerably. Maybe there are bigger ones available locally now, I don't know. The alternative is to get one from a larger market.

I don't know what size they used for the 737 lift but they were pretty big.

JR

You see cranes that large quite a bit in the oilfield, windfarm construction, etc. as JR mentioned cranes are arong straight up but when you have to reach out they get weaker. Thus to be able to reach some places they have built some crazy strong cranes out of necessity. When you get to talking about booms in the hundreds of feet long, things get big, and spendy. My dad regularly rents 90T rates cranes just because that’s what the local crane service has. They are like $400/hour though. That same company has a few that are rated up to 550t!


Go check out Grove Cranes. They make some crazy stuff!

Ha! That came in at the same time!


Check out a crane like the Grove GMK 7550. 550t rated

Thanks. Interesting stuff and very mechanical.

The problem with supporting a truss, like on these cranes, in that manner is that you are introducing one hell of a point load at that point on the truss. That's right where it will bend, or break. You have actually weakened that truss by not allowing the entire structure to "work" and properly distribute the load down its length.

Thanks, javadog, for the great explanation of these kinds of cranes. It sounds like you have worked with them a good deal. Like I alluded to earlier, us airplane guys are far from being crane guys. We rely entirely on guys like you, with your expertise, to supply the cranes and set them up. We trust whatever you give us.