I am currently working on a new video and wanted to include some specs on what is seen in the video. I was going to narrate the video stating what is seen and what is going on . I have a few questions that I am having trouble finding the answers to on the net. Anyone that can give me the right answers i will include in the credits as my technical advisor. Thanks. It is a new video on the Link Belt Crane that I have posted photos about on.
Well...what are the questions?
diameter of the cable, tensile strength of the cable, how is the cable constructed? using what kind of wire? what is the weight of the machine, weight of the counter weights? what is the liftingcapacity of the machine? Why is the cable wheel changed up top when balling versus lifting? how is the main spool released to allow the ball to drop? Approximate amount of force applied when ball is dropped. Approximate amount of force applied from a swinging blow. I know the weight of the ball is 5000 pounds and the formula for applied force is mass x acceleration. what wold be the acceleration of the ball from hanging statically to impact from a 30 foot height once the spool brake is released (to determine force of impact) who makes and sell the wrecking balls? what is the optimal angle of the boom?
Wow, that's a lot of technical info your looking for! As far as the cable specs, the manufacturer usually specs what cable goes on a drum. I have seen a webpage that has a very large number of Link Belt brochures and specs, but darn it...I don't remember or have a link to the website. Why is the cable wheel changed up top when balling versus lifting? I'm not sure of the question. how is the main spool released to allow the ball to drop? All conventional cranes have clutch and brake drums, and that machine is torque convertor drive. When you hoist, all you have to do is engage the hoist clutch with brake on. The torque convertor allows slipage so the engine doesn't stall. Then you simply release the hoist brake, and hoist goes up. Once load is raised, you apply brake, and disengage hoist clutch. To drop a ball, you simply do what is known as "free fall", which is to simply release the brake and hoist line will pay out. Maybe others will jump in here with other info.
Wanted to see what you guys thought. The video is about them changing the shock absorbing tires and cabling in between the ball and the end of the static line. A 30 minute job with the potential of uneleashing a lot of information about how and why.
Well I certainly hope others jump in here beside just me as I have been away from these machines and methods for some years. The tires are just what you described...for absorbing shock loads. One example is; you drop the ball and break some material. Each time you drop the ball and hit material, you step on the brake to keep hoist line from paying out. You hoist the ball, drop it, hit the brake, but then the material breaks out and the ball drops while the hoist line is held by brake. In this situation, without the tires to absorb shock load, the crane would take a heck of a jolt. The shock absorbing tire is a very important part of using a drop ball by protecting the crane and boom from excessive shock loads.
Was reading this thread and envisioned the backlash that could happen when a controlled free fall comes to the end. Is there an automatic device or is it all operator on the brake? I was helping untangle the hoist cable on a small carrydeck which had made a lift before they noticed the backlash and after much prying, hammering, unbolting and so on we had to get out the grinder and start cutting cable. That was experience earned as opposed to learned.
There may be other reasons for changing the cable that connects ball to tire and changing the tire, but the most common reason is deterioration of the cable and the tire. During the cycles of impact and lifting the ball for another drop, the cable and tire take a beating, not to mention getting snagged by reinforcing steel and concrete chunks, as well as occasionally the ball gets lodged and you have to do a little tugging to free it. All this destuction takes it's toll on cable and tire. So frequent inspection and replacement of cable and tire is prudent, neglecting to do so could easily lead to losing the ball. Hello shipman. There is no automatic device controlling the winch hoist on the crane that ERH is referring to. It's a free turning drum. When you drop a demolition ball by releasing hoist brake, the weight of the ball will pay out cable. When the ball impacts structure, the operator has to be on the brake immediately or cable will continue to pay out. Which is part of the reason for the tire at the end of the line. When you step on brake to hold hoist, and at that moment the ball either rolls off a floor, or crashes through a floor; without the tire to absorb shock the crane would do some rockin' and rollin'.
Yes I am aware of the reason for changing out the tires and the cabling. Both were pretty well worn and beginning to fray after 8 days of heavy use. The structure had a lot of rebar which caused snags when lifting out a freshly balled floor slab. In fact this set up had 3 heavy duty truck tires lashed together with 7/8 cable and crosby clips. I have a recent calculation of the force of impact based on mass times acceleration. Based on the 5000 pound mass of the ball falling at a rate of 16 feet per second from a height of 30 feet per strike yielded a 27,000 pound blow.
Though not completely sure, I have been led to believe that the pulley, or sheave, at the top of the boom needs to have a deeper groove in it for things like balling, because of the side loads, and to keep the cable in the groove when the ball strikes and a little cable pays out. It is no fun when your cable jumps the sheave. The deeper grooved sheave tends to wear out faster though, and that may be why it is changed for normal hoisting jobs. Good question to ask the operator about. With some time and study, you could calculate the force of the swinging blow. You need the speed it is traveling when it strikes. You could measure the radius, and find out the rpm the crane swings at to get the tip speed. It would take a bit more math than the falling calculation though. Here is a selection of wire rope specs: http://www.wireropeworks.com/products.htm Hope that helped some. By the way, you have some great videos.
As far as technical questions about capacities, line pull, boom and counterweight configurations, the operator's manual and/or the load chart inside the cab should have the answers for that specific crane. Or here's a link to the archives Atcoequipment referred to, there are specifications for several different models there. http://www.linkbelt.com/lit/archive/archive_home_lbp.htm