doubt interpretation swivel arm crane (machine construction examination)

[criauz]

Hello everyone, in two weeks I have the machine construction exam and in doing the exercises on the book I came across the sizing of a swivel arm crane. I have calculated all the various binding reactions on the column plate flanged to the ground and on the arm loaded by a p. weight so far no problem. the text asks me among other things to dimensional the column by speculating circular (so a tube) with half length a hole d=30mm for the passage of the electric cables. I have assumed as a model that of a perforated plate whose width is equal to the diameter of the column tube (I hypotize it and then do safety checks) and x thickness (ipotized also this from me). This slab I thought and seen that it is subject to flender moment. Here comes the doubt: I'm gonna hire him on the plate plane or agent outside the floor? I tried to do some sketches and the plan on which the normal force acts depends on the view you choose to represent the crane. So I don't really know how to behave.
Thank you.

 

[MBT]

Sorry, but...
I'm not an engineer, but I don't understand. . .
If you have a column made with a round tube, why do you want to calculate it as a perforated sheet? ? ?

 

[MBT]

However, try first to give a last to this discussion. . .
http://www.cad3d.it/forum1/showthread.php?15368-dimensionamento-gru-a-bandiera&p=127848#post127848Perhaps you already find the answer to your question

 

[criauz]

I don't have the formulas to calculate a perforated tube. I have to use a model among those I have on the book and there are: perforated slabs, shafts with diameter variation, carved trees (with tabs or key)
- - - updated - - - -Sorry, I found the pipe with a hole. I answered myself. - I'm a beota. I'm closing the conversation. next.

 

[MBT]

I got it.
but between a pipe and a plate there is a huge difference
rather, if the diameter of the hole is resible compared to the diameter of the pipe, better use that of the pipe "whole" and make debit corrections!

 

[criauz]

I got it.
but between a pipe and a plate there is a huge difference
rather, if the diameter of the hole is resible compared to the diameter of the pipe, better use that of the pipe "whole" and make debit corrections!

I didn't see a bookmark I had on the manual. I found the tube paragraph with cross hole and calculated everything.
I have to climb only a little bit the odds because I get a safety coefficient too high, that maybe I can reduce a little so you save material however leaving a range of lifting loads quite good.
thanks anyway for the answers. :

 

[MBT]

Be careful. . .
for lifting organs, safety coefficients are quite high
I don't know what the legislation in force says about it, but once it was considered (for wagons) that the maximum full load arrow should not exceed the value of 1/1000 of the span
I think a similar rule was followed for flags.

 

[criauz]

mmm, then I leave so, even because if I try to reduce the quotas even with the interpolation of the data, I struggle to find the corrective coefficients of the tensions. However I would say that there are as sizing, I used for the structure of the tie rods, column plate and arm a steel from rectification since the structure is subject to bending and traction with rather high loads and from what I remember of metallurgy, the rectification steels are suitable for the constructions of this type. At this point the choice seems to me to be clear given the rather high safety coefficients. thanks for the answers, they are all small things that I will need seen my unexperience

 

[MBT]

rather than letting them "for good measure", do a little research
see what regulations say about lifting organs and adopt appropriate coefficients

You're an engineer. You're ingenious!

 

[Enigma]

mmm, then I leave so, even because if I try to reduce the quotas even with the interpolation of the data, I struggle to find the corrective coefficients of the tensions. however I would say that there are as sizing, I used for the structure of the tie rods, column and arm a reclaim steel Since the structure is subject to bending and traction with rather high loads and from what I remember of metallurgy, the reclaiming steels are suitable for constructions of this type. At this point the choice seems to me to be clear given the rather high safety coefficients. thanks for the answers, they are all small things that I will need seen my unexperience

Hello criauz, I have a curiosity... What do you mean when you write that "I used for the structure of the tie rods, column plate and arm a reclaim steel"? ... I'll explain better, didn't you use pipes, tubulars, upn, ipe, heb in "remediate steel"? I've never seen it.

enigma

 

[MBT]

Hello criauz, I have a curiosity... What do you mean when you write that "I used for the structure of the tie rods, column plate and arm a reclaim steel"? ... I'll explain better, didn't you use pipes, tubulars, upn, ipe, heb in "remediate steel"? I've never seen it.

enigma

I didn't notice the sentence!
great consideration I share fully !!!

 

[criauz]

Good morning, everyone. Unfortunately I had used a 38nicrmo4 but I saw it is suitable for biella, trees etc but not for metal structures. So I did a research and saw that a construction steel could be fe420 (s420), the only problem is that of this steel I did not find any critical value to fatigue, neither bending nor twisting. I only have tensile yield voltage for static loads. I went to see if there were goodman diagrams for this steel or similar but I didn't find them anywhere. So I don't really know how to remake the exercise without these parameters. do you know where I can find the critical tensions to the fatigue of this steel? goodman diagrams present on the book are all steels suitable for the construction of mechanical components like biellas, trees etc. but no construction steel.
Thank you.

 

[MassiVonWeizen]

what you are looking for is the correspondent of the s275 by clearing the norm en10025
I have no idea what data you need, but try these tables

 

[MassiVonWeizen]

Sorry, there's no link to the tables.http://www.tecnocentro.it/ita/tabelle_acciai.htm

 

[calacc]

The only problem is that of this steel I have not found any critical value to fatigue, nor torsion bending. I only have tensile yield voltage for static loads. I went to see if there were goodman diagrams for this steel or similar but I didn't find them anywhere. So I don't really know how to remake the exercise without these parameters.

There are specific regulations for fatigue design in cranes, it is a subject that is treated differently than fatigue design in trees.
I'm sorry, but why do you have to run fatigue testing? Did they give you the operating conditions of the appliance and you have to classify it according to the regulations? I don't think... since it's a machine construction project!

Anyway, if you're interested, I can get you something... Since I've been working for the thesis, I can give you a collection of rules to apply for in the library, you have everything you're looking for.

 

[Enigma]

There are specific regulations for fatigue design in cranes, it is a subject that is treated differently than fatigue design in trees.
I'm sorry, but why do you have to run fatigue testing? Did they give you the operating conditions of the appliance and you have to classify it according to the regulations? I don't think... since it's a machine construction project!

Anyway, if you're interested, I can get you something... Since I've been working for the thesis, I can give you a collection of rules to apply for in the library, you have everything you're looking for.

hello calacc, as well I would be interested in knowing the norms you used, I for "bilancini" used the uni en 13155.

enigma

 

[calacc]

Okay, okay, I'll publish the list.

uni iso 4306 – 1: 1990 lifting appliances, vocabulary, generalities.
uni 7670: 1988 mechanisms for lifting devices, instructions for calculation (retreated norm without replacement from one on 22/01/2009, now included in the euronormativa)
uni en 13001-1: 2009 lifting equipment - general criteria for the project - part 1: general principles and requirements

 

[Enigma]

Okay, okay, I'll publish the list.

uni iso 4306 – 1: 1990 lifting appliances, vocabulary, generalities.
uni 7670: 1988 mechanisms for lifting devices, instructions for calculation (retreated norm without replacement from one on 22/01/2009, now included in the euronormativa)
uni en 13001-1: 2009 lifting equipment - general criteria for the project - part 1: general principles and requirements

Thank you very much

enigma

 

[meccanicamg]

I would say that first you need to study mechanical technology and understand the steels as you catalog and why:

- s275jr or similar are construction steels and are used to be welded, processed easily. all carpentry and frame structures are realized in general (fe360 fe430 fe510 according to old indication)
- special steels linked as 38nicrmo4 by reclaiming are used to build mechanical components (not frames) such as trees, gears, parallel bars, anchor bars etc.

other consideration is that on books there are so many cabbages and you also have to understand what is written because:
- on a tree you go static verification, fatigue verification with carvings, point load verification, vibration analysis etc.
- on a structure you go static verification, verification to welds perhaps fatigued as well as static, verification of static bolts and possibly dynamic on the rods or screws that undergo alternating loads in exercise (as for the action of the wind)

reading the first post that is the explanation of the text is to indicate in my opinion that the vertical column is derived from tube and in half height has 1 ø30 hole to the outside to pass with the cables, so I can imagine that this can lead to create a model of "cable shaft" containing the "hole defect", then make a fatigue check of the structure with carving effect (but you have to look on the peterson's stress concentration factors).
more or less looks like this belowwhere there will be rotating bending conditions according to where the turret is rotating and possibly an alternating twist if with the continuous load to rotate by means of a turn in a direction and half turn in the opposite direction with remarkable accelerations.

if there are regulations I would say that they should be respected, then if by scruple or discourse of academic calculation you want to implement something more refined than 2 formulas from regulations, well come, however with criterion and in a reasoned way why not everything applies as theory you want.