Saturday, March 11, 2017

Telescoping cranes can bend, but they should not break

When the boom of a telescoping crane is extended to its full reach, there is very little metal overlapping at the joints. I have always wondered how they avoid bending. The answer is that they are evidently designed to safely handle some bend. (I'm being vague about where I got some of these on Facebook pictures because there were some comments that were not "family friendly.")

From Facebook

From Facebook

From Facebook
[Actually, I don't see much bend in this one.]
From Facebook
From Facebook
From Facebook
Philippe Dumas posted two photos with the comment: "GMK 6300L lifting Air compressor to the lake ground from the dam 74m main boom + 21m jib was necessary to reach radius."

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My reaction was that the air compressor better be rather light with a radius that long.
Larry Winchester Jibs are for height, not radius.
Keith Havard Hope the pic of boom flexed is with load on hook.
Mike Newcomb lot of cable. [I wonder how much weight the cable itself adds to the load at the end of the boom.]
Mark Walker I'm thinking he maybe close to the end of the chart in that second pic looking from the rear

But the operator needs to know the chart and avoid bending too much. It looks like they should have lifted the tower crane boom as two pieces. Note that as soon as the boom broke, the base lost its load, and it straightened right up.

Screenshot 2
Screenshot 1
Update:
Terex Cranes posted
Here's a great example of collaboration - Cropac Equipment Inc., C&C Crane, Total Crane Rental, and MTN Forming brought their expertise together on this Ontario waterfront project with Terex SK 315 and SK 415 tower cranes http://info.terex.com/OntarioTowers
[It looks like there is a bend in that boom to me. It also looks like the inner segments are only partially extended. I assume they are overlapping more steel at the base of the boom to try to reduce the bend.]
Balaji Mani posted
[Each segment is extended the same amount, but only about 2/3 of its length. I think there is a little bend in the boom.]
Frank Pintaro posted
Just a little boom deflection Gmk 5275
J.P. Duffy posted
Might be short rigging a couple pics tomorrow
[Building a Potain tower crane: "It will be a MDT219 10t 65m jib." There is a long discussion about "line pull." I don't know what they are talking about, and evidently the operator also does not understand either.]
J.P. Duffy posted three photos with the comment: "Just another day under the sun."

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This one is interesting because I do not notice a bend in the boom even though it was operating with a rather long radius.
Screenshot
Bay Crane posted
[It looks like there is a little bend in this one.]
Patrick M Harrison posted
Fish on!!
Brandon Leichinger commented on the above posting

John M. Childers commented on the above posting
I can relate!!!!
Devin Parsons posted
Fish on!!! 🎣🎣🎣🎣
Brandon L Grace commented on the above posting
Why yes.
Thomas Dearmond on the above posting
Brandon Owens commented on the above posting
Yes sir.
Jacob Gibson posted four photos with the comment: "Testing the limits of our brand new LTM 1250-5.1."

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A group added two photos. I'm surpised the boom broke in the middle of a segment rather than the near the end of the segment where the next segment's insertion ends.

1, cropped

2, cropped
Posted, cropped
Craig Harry Cameron Derek Manns seen one of these before ?Derek Manns No never broken like that.Garrett Larkin Brian Boudreau I'm not even sure how.Brian Boudreau KATO's new series of knuckle picker.

[It looks like Kato needs to go back to the drawing board 
(actually, the computer screen) and add some steel to the main boom. The problem with computer aided design is that it allows the engineers to build with less steel than they did in the pencil and paper days. That improves the cost of building, but lowers the margin of safety.]
Posted
Jeff Funk Looks like rotec failure ouch
[This is the first time I have seen a photo of the attachment of the house to the truck failing. Normally the truck tips over if the load is off the chart.]

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