How To Calculate Crane Boom Thickness

I appreciate your reply. the previous pic you see has been taken by myself at the firm. with no offense and without being rude, i know its an aerial platform.i mentioned crane because it does the lifting too. another thing is that my father is not an engineer but he is the one who manufactured this platform. he has an experience of 40 years. and he designs and manufactures these things by reverse engineering. he made this platform by just watching the picture of it. then made his autocad drawing and by his experience, sets the thickness too. i ,on the other hand, want to go through a proper channel. first design the platform with engineering rules and then go for fabrication . please help in that manner. here is the pic of crane my father manufactured too.( recovery crane). pic also taken by me

With Reverse Engineering, one is always some distance behind the market curve, and one runs the risk of patent and copyright infringements. What is needed is an Unique Selling Proposition for which a bit of market analysis is needed. Once that has been completed, then is the time to carry out Engineering design, and it is far easier to modify existing designs rather than start from scratch.

How would one obtain insurance cover on the equipment without a suite of "as built" drawings <rhetorical question - NNTR>?

How would the organisation protect itself without a suite of "as built" drawings and Factory Acceptance Test records for any particular piece of equipment <rhetorical question - NNTR>?

The forum cannot see the shape of the operation and #1↑ still applies.

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Reverse engineering is a common practice, but, in this case it could be dangerous - as there may be a life(lives) on the line as it were as your first pic shows a personell basket. Unless you do a true reverse - ie., you must do a complete disection of the existing, and would include complete dismantle and measure of all components and then you still have the problem of materials selection.

You can goggle "crane standards" and "crane standards ANSI" and you will get quite a list of resources available. They likely will not tell you how to design, but will give you what the requirements are, and remember, it is better to err on the side of safety(that is, overbuild-increase your FOS- if you are not sure).

i am sooooooo very thankful to you for letting me know about crane standards ANSI about which i had no idea. Thank you very much :)

i will go through them for sure .

First of all, I must commend your father on his entrepreneurial spirit, as well as his persistence for working diligently at growing a personal business for 40-some years.

I am particularly impressed that he apparently taught himself AutoCAD to what ever extent..

I also comment you for your persistence in completing a mechanical engineering degree program, and further, for wanting to apply it towards the (family) business.

I certainly understand the inclination to want to expand the company product line. However...

Further examination of your photo prompts the issue of whether or not the entire vehicle is, in reality, a former tow truck with an improvised telescoping boom crane replacing a standard tow ''hook''...

It seems the better course of action would be to first apply your engineering education towards analyzing exactly how safe your (composite) vehicle is, and is not, before it tips over and hurts somebody.

It looks like it could use more and/or better ''outriggers'' at the very least...

Maybe, you should also look at becoming a vehicle dealer for a domestic (or foreign ?) company that already manufactures such (specialty) vehicles, rather than starting from ''scratch''...

thank you very much for your reply .my father is my role model because of his efforts and all.

you pointed out a very important aspect i.e vehicle on which i works. it is mounted on the frame of vehicle. for that a bed is fabricated first. the superstructure is fabricated/mounted on it then. the current picture has a fire brigade and fire fighting aerial platform on the back, both fabricated on the vehicle frame. That is why it is confusing. the aerial platform is allowed to work at an offset of 3m .i think firstly i should go for the COG of the vehicle? shouldn't i?..

Focus on the formulas for cantilevered beams and moment of inertia for the shapes involved.

i get that.but in case of aerial telescopic platforms, there are multiple booms. all i can think of is to calculate loads at the end of one boom. what to do when there are booms inside booms. stress= force/unit area can be used to find the thickness, but for one boom.

To avoid a too heavy boom in general, you can reduce the wall thickness by using collars (ring frames) at the ends. This also will stop the booms from sliding through when retracted. You might use the endpoint of the thicker boom as a support point and the endpoint of the smaller boom into this a your second support point. The thickness will depend on how far you will let the booms retract and the provisions you have in place to let the booms slide on.

Thanks allot for replying . :)

by ring frames do you mean this?

i see a support at the end of boom too..bolted on .

this is what i understood of your comment.

Those bolted metal sheets are there to keep in place the boom sliding bearings. In big cranes the segments do not slide steel on steel but on bronze or or other alloys bearings. The form is such as you see in order to center the segment during sliding and avoid side loads due to eccentricity. In some cranes (Liebherr) the lower side is full half of a cylinder and not only curved on 2 sides. those bearings have a double goal:

- avoid galling

- due to a lower Young modulus the pressure distribution is over a bigger area thus decreasing peaks in the case of steel on steel pressure is limited almost on the edge which leads to high wear.

Nick Name gave you the explanation for this type of boom. The ring or frame at the end helps very little in this design. Here the strength is about the same over the whole boom section.

Lol....(first day in the real world)

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Ooooh, look! An Engineering Dog!

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Kick it up the butt/jacksy/ar$e and it makes a bolt for the door....

Okay that is epic. LOL!

Should be Lyn's new profile pic cause it pretty much covers just about every response coming from him.

Okay, I have to ask; what make the drawing seem characteristic of a very long poem?

Is there a beam analyst tool with the CAD your using? If not get one. It will help in analysing the forces on the arm you design. Will aid in giving you information on the bending of the arm under load. And how changing the tube thickest will change how it bends.

hahah..yeah .thats harsh and should be :D

but the thing is being in school we study so many subject ..starting with statics..leading to mechanics of materials with different concepts..then goes to machine design to vibrations..how can i keep them all in mind unless i imply them in professional life :/..still i know that's lame..but i wasn't even ready to imply that all .as i was afraid that i would not be able to do any..but i decided to go for it with some advise from some seniors in the field..so a little appreciation for the effort would be nice :P..and thanks for replying too :)

It is not lame.

Whatever you do, do not get discouraged.

You are absolutely correct in the method you have chosen and if you stay focused you can attain your goals.

Seek opinion and knowledge from competent, knowledgeable, experienced engineers.

The most difficult part of becoming competent in any engineering discipline is remembering all of the theory, weeding out the misconceptions, and learnig how to apply the knowledge gained.

Be prepared to accept an occasional failure but make sure you do everything possible to prevent injury or death by thoroughly testing the design in a controlled "real world" environment.

Most people take 4-6 years after schooling to become reasonably competent and 8-10 years to become an expert in whatever field they choose.

Good luck and keep up the good work!

Good perspectives to offer SHOCKHISCAN,

Many times we apply the law to others and extend grace to ourselves, as is seen in a couple of Posts, rather than extending grace to others and applying the law to ourselves.

We all have faults in which we could use some guidance. When we are arrogant, we have a tendancy to be impatient with others, critical of others, etc.

John Maxwell writes a lot of leadership, teamwork and self-directed education type of books and he says, "if you want the right information you have to ask the right questions." Mughal88 may not have this all down yet but the most effective place to learn is from other successful people.

You do have an admirable attitude which will likely serve you well.

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I have one small pointer, but it is not specific to crane engineering:

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Your command of English seems very good for a second language, just make sure you know the correct definitions and spelling of the words you use frequently. You have applied the word 'imply' in several comments, but the context implies you should have used the word 'apply'.

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'Imply' means to suggest or hint without saying it directly.

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'Apply' can mean to make use of, practice, and administer. 'Apply' can actually have several other meanings, but I think this is the near-homonym you probably had in mind.

oops..:P

thanks for the correction there :)

If you are a newly graduate engineer recommend to your father to hire a professional engineering consultant to design your crane structures. Work closely with the consultant and ask him to be your mentor.

Otherwise, good luck and lots of it! That is your only insurance.

Vince

Mughal, I have worked in EOT crane industry for 33 years. It is not so simple to mfr. such truck mounted cranes. You will need technical know how to produce such cranes. Any one giving such know how will charge you millions of $. If you are considering to mfr. only one or two capacities then you may be able to copy from any imported crane, but still it will be risky business. I apritiate your will to take up such projects at such young age and just coming out of college.

Mughal,

A Mechanical Engineer myself, I would advise you to retain the services of a professional Structural Engineer. We know that online guides won't make a MechE out of a layman. Equally they won't make a StructE out of a MechE. It's a specialised field. You may find the formulae; you won't find specialist professional judgement in a webpage.

If you are a graduate engineer, you should already know how to apply those skills. But Lyn already let you have it! Does your country have engineer registration to assure others that you are competent?

What codes are you using? When I was doing such things (on tubular transmission poles), I liked the ASCE method of applying the safety factor to the loads, but most seem to use AISC with the safety factor applied to the material being used. More in the past than today, it was called a "factor of ignorance." If it is holding people, the safety factors could very well be different; probably higher.

Probably your hardest job will be coming up with the various load cases, and there will certainly be several critical at different areas of the boom and in different positions--horizontal, raised, etc. What about impact--that is, will they jerk when the cables tighten? What about the wind forces? Does the customer want you to consider Charpy Impact? Will they ever have to pull sideways? What about abuse--it's rated at 10 tons, so it should take 15 by using up the safety factor.

Is reverse engineering adequate? How do you know that the guy who designed that one did it right?

Don't forget about the chassis it is mounted on, the outriggers, etc.

I would think that this is the type of knowledge that would be tought in how to be a engeneer skool

Have you purchased, installed and started playing around with any of the software tools suggested here yet?

i have solidworks and ANSYS. i will surely proceed to them after my calculations on paper . Thanks for replying..

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I think we need to give him a break.

For example, I've worked in engineering for nearly 15 years now and had to come on here only a few weeks ago asking about shock absorbers. It was due to having never worked on them in my engineering career to date....and also due to my family not owning a car when I was growing up so I never became interested in them or had a chance to work on them (the shock problem was not about cars but everyone refers to a car shock absorber design when you mention one).

If I were you I would start with the existing crane, model it, do calculations on it and if possible put it through stress analysis on the computer. This way you can verify that the calculations you are producing 'work'. You know the crane 'works' and has not failed so therefore your materials should not be overstressed.

You will need to get a material analysis done by a 3rd party if you do not know what it is manufactured from.

Make sure you have a full set of calculations for the current crane. This includes static and operating conditions. Start off with compiling a list of 'load conditions' and 'safety factors' you need to work to. A lot of these can be found in international standard. Calculate section stresses, pin deformation, pin stresses, clevis stresses etc etc.

From there, you could then look at improving on the current crane. Where you could change a pin size, material grade, section size etc to optimise the design. Remember though, a change you make to one area could have a knock on effect to other calculations. Cost is a factor too. You might optimise a section but could ramp the cost up due to using a non-standard section size.

In short, start with what you have now so that you get a good understanding of how it all works. Get a 3rd party to verify your calculations - THIS IS VERY IMPORTANT, DO NOT ASK YOUR FATHER TO DO THIS FOR THE OBVIOUS REASONS.

Do not go straight in to calculating and designing a new crane as you do not know that what you are calculating will be representative of the real thing.

Hope that helps

Kev

This is called "reverse engineering" see also # 20.