design of a telescopic vertical lifting air platform

[IlConte94]

Hello everyone, I am new to the forum and although I am still a student of the mechanical engineering master I preferred to post in this section since my (or rather my) questions concern a teaching project assigned to us for an exam but that is to all effects a complete project. as from title we must design in group (but we are only 2 of which I address "design", the other person is "energetic") a vertical telescopic lifting platform like the following:I also link the site of this machine to show you the technical specifications: https://www.topcarsrl.com/dettaglio-prodotto.php?id=14the first problem is that the professor has told us to do the technical specifications, however, by imposing some very unlikely stakes: the machine must be for interior (like the one in figure), to be closed to be able to pass in the doors of the industrial warehouses (then max 2m height) but to be extended to at least (underline!) 10 meters of working height against the 3.5 of this! This already poses an obvious problem of achievement and I wanted to know if it is technically feasible.
the design must be complete, in the structural kinematic sense, cad drawings of every detail and fem analysis of the individual parts and the complex with particular emphasis on the extendable column. In addition I almost forgot dynamic analysis (example tipping problem etc.). now having knowledge notionistic from the triennial (as I think happens a little in all of Italy) both of science of the buildings and of applied mechanics that of construction of machines, are not able for example to "see the machine as a beam" with constraints, loads, to predict to eye how they exchange the forces (for example to dispose of skates between the swives), so I do not know practically from where to begin. I think that you should start from a rudimentary lifting scheme (there must be a hydraulic piston in the bottom that pushes the slender and then others should parade to follow through a system of carrucoles and already preview the position inside the swires or between them seems to me a problematic not of little account at the level of encumbrance.. . )
I mean, the situation is pretty messed up. probably the fault is also mine that I did not study well the basic subjects (my priority was to graduate immediately to the three) but the very antiquated teaching certainly does not help... In addition I am learning cad and fem (ansys) software practically alone since the exam previews its use also pushed but there are no dedicated courses except perhaps that of assisted design (where however the emphasis is on mathematical theory as usual... )

if someone is able to help me even with some point I thank him in advance and maybe after I also make him a small monument! Thank you!

p.s: a detail that I have forgotten is that the threads can be as in figure from the smallest in the bottom to the largest in the top or vice versa from the largest in the bottom to the smallest in the top: the professor left us free choice but he said that in case we do it with the smallest down he wants a justification to the choice and it was not good to hear: "We have seen that they are generally made like this! " but we have also tried without success to think it was due to any advantages for the hydraulic system. . .




p.p:s: the exam did not write it but it is "construction of machines say 2" since the three-year period was "constructive elements"

 

[meccanicamg]

I see that every time these professors come up with good things. but are they free professionals or just teach? However I imagine that in the hollow tubes there is a multi-stage cylinder and sincerely arrive at those lengths and maintain the strength is utopia provided that everything is closed is high enough. with science of construction should be enough for you, load of tip. bronze platters take the side load and are bound to sleeve. the first down and the last under the air platform are incarcerated. in the end it is so much more beautiful theory and practice and sizing are a little necessary. the multistage cylinder will be hinged at the bottom and at the top not to load the seals of the stages. I think it's so... maybe looking at the built project there can be different solutions.

 

[meccanicamg]

It is essential to make a scheme first of all gross and then refine it. for the 10 meter means that they will be about 5 2 meters swives since it must be as height but there will be a part always driving in the swires. for the tipping speech you have to put on the omino and see the centerpiece when all the lift is paraded and curved more shift of the games of the lards. If the center of gravity lies in the base, it does not turn.

 

[IlConte94]

Hello and thank you for the answers! the prof also has a mechanical engineering company as you had guessed!
for the multi-stage cylinder question we have proposed it but excluded it if I remember correctly because you hypothesized of maintenance of force! there is a hybrid system consisting of a normal cylinder at the base that moves the second vent (from the bottom); then the other parades thanks to a system of pulleys and ropes (I don't know how best to define it!).thanks for the suggestion on the constraints! Do you have any ideas about the wider issue at the bottom or at the top?

 

[IlConte94]

on a site I found this project that should make the idea of how the system is without the use of a multistage cylinder, but unfortunately there is no detailed information on the operation of the carbides and ropes, in fact I do not understand some. . .

 

[meccanicamg]

is a pulley system to command each branch. is what you do to get the multistads out even with chain controls. practically you have 2 m scarce to accommodate the closed cylinder and leaving it will do little less than 2m hydraulically and then it will expand on 5 branches externsible the 2 meters of each stage....mah.....it seems so much a fetecchia. However, I think it is also done with the multi-stage cylinders, so much to lift there are few kg and however there are 5 diameters of tube to scale. the smallest defines the strength of the cylinder. for the speech that the sphiles are from the smallest to the greatest to climb, sincerely there is nothing intelligent cyst that we should learn from nature....the trunks are big on base and tight on. since it has to react to bending it would be better big down. But maybe the basket above is a little big and to keep it better rigid and to be able to react both to the man weight and to the load weight you prefer to have a greater width to react better.

 

[IlConte94]

Hello, thank you again for the answers! leaving the lifting system in itself, regarding the structural part I tried to throw down something very preliminary:This should be the static scheme with the "foam" constraints you told me (that I knew by name but we never applied to construction science...) the upper one is probably an abomination that I was thinking first with skates as constraints but has nothing to do with... one of my doubts is because I want to study the arm I placed under a frame since for now the base doesn't interest me... the same goes for the upper basket, but since the loads enter from them I should find a way to get the forces (and the moments) entering the arm that I put them for simplicity as only 2... here I have a doubt: apart from that there are more in reality (weight operator, tools, various pushes on the railing that are regulated as point of application etc) it is correct to report them here somehow or it is better to consider the basket as a piece of the beam (as in the photo after): is probably the same because the approximation and simplifications I am doing in two dimensions (at least almost 1) are enormous, but perhaps there is an optimal way to proceed?

 

[meccanicamg]

If the load on the basket is decentralized you find it cone you indicated: a force multiplied an eccentric arm. This load moves to the first vent. do not confuse internal constraints with external ones. the wheels on the ground will be a zipper and a skate fixed on the ground. the sleeves you have them as internal bond to the system and the hydraulic cylinder is an internal force that keeps the height and discharge action and reaction.

 

[IlConte94]

. the sleeves you have them as internal bond to the system and the hydraulic cylinder is an internal force that keeps the height and discharge action and reaction.

Hi, I didn't understand this phrase well: as I drew them in the first photo I mean inside the sleeves, between one spherical and the other! I wanted to know if it was right to consider the arm like this but I think so.

for the hydraulic cylinder I did not understand how it is an internal force... and in any case should be considered among the loads of the static scheme? I thought not...

p.s: (in relation to not confuse external and internal constraints) at the base I put an ink as if it was an external bond because I want to exclude the base for the moment, I know that in reality there is no external bond!

Thanks again for everything!

 

[meccanicamg]

the pipes of the swire are of the matrioske to a decreasing extent and the bronzes with constraint of sleeve react with horizontal force and moment. However, in order to consider that the whole system is a long beam of 10m, an internal force is necessary which is the force of the piston that applies strength and reaction to the total, preventing the swire from becoming a labile structure....in which with calculations more nothing. then when you have determined the reactions on the ground you break the beam into real elements and go to study how much the reactions are worth to the bronzes (manicotti).

 

[IlConte94]

the pipes of the swire are of the matrioske to a decreasing extent and the bronzes with constraint of sleeve react with horizontal force and moment. However, in order to consider that the whole system is a long beam of 10m, an internal force is necessary which is the force of the piston that applies strength and reaction to the total, preventing the swire from becoming a labile structure....in which with calculations more nothing. then when you have determined the reactions on the ground you break the beam into real elements and go to study how much the reactions are worth to the bronzes (manicotti).

ok, yes perfect, in fact I was recovering to reason today and I realized that the structure would be labile! but then would it be the same thing to consider in the extended position the constraints between the tubes as "internal registers" (so banally unique body to different section)? or should you consider them sleeves and add the vertical force to the other of the cylinder? probably having the help of the fem it is advisable to be closer to the possible reality and then put the sleeves and the strength.. .

 

[meccanicamg]

with the fem you have to do for tight bond because you have to study the ass. in the simplified calculation could be a recess but at this point the single variable section beam could be studied, at least in the first approximation equal to the weakest section for the whole tube.

 

[IlConte94]

with the fem you have to do for tight bond because you have to study the ass. in the simplified calculation could be a recess but at this point the single variable section beam could be studied, at least in the first approximation equal to the weakest section for the whole tube.

Okay, thank you so much for the various ideas, I think I'll be very helpful! then maybe going ahead after we have done the first simulations I am taking the topic and maybe discuss the correctness of the various models and the various assumptions.

 

[meccanicamg]

just to throw it there.... why the smaller tube is down and the bigger tube up?
the answer is the same also for the bovolo springs that protect the screws of maneuver.the answer is very simple. depending on the application, especially for vertical use, it is mounted in one way or in the opposite way depending on the prevalence of the dirt deposit by gravity or for projection of particles.
in your case the dirt falls from heaven and goes to the ground. If the largest of the tubes were below it would create a series of steps that offer useful surface to get dirt into the lard that drives the pipe.

 

[meccanicamg]

other thing, before you realize the real structure, you should realize a small fem and two calculations to verify the behavior of the beam in both ways.
for example I made a square beam full of two sections like this:I did the analysis by applying plausible random loads in the greater section condition stuck down and applied force at the top:and I did the analysis also for the overturned beam, that is with the small section below framed and the forces put on top:As you can see, the best mechanical solution of effort is the first, but taking into account the cleaning speech is to be preferred the second. so make your assessments and take the path by motivating choices and what you want to highlight in all this. Keep in mind that you can put scrapers that however have a cost and wear, keep in mind that all in all the iron does not cost so much and it is long-lasting....insomma make yourself a list of pros and cons and make the choice also according to the estimate of the costs you feel to compare for the two solutions.

 

[meccanicamg]

If you want to evaluate the stage fine cylinders there is a beautiful discussion qui

 

[meccanicamg]

the curvature of the structure will look a lot like this:

 

[IlConte94]

Thank you so much for the interest, really! We will evaluate with prof which of the two solutions to choose by giving motivation the various things you have suggested to me! already that we have seen that I recognize the workbench of ansys: for the final fem (the one with the geometry drawn to the cad, 3d tetrahedral elements of mesh etc.) I intend to use the workbench since the mechanical (the old one to black background) from problems in importing complex geometries... for models with beam/plate 1d/2d preliminary I recommend always using workbench or maybe I could use mechanical? I would go of workbench but the prof is particularly fond of mechanical and perhaps prefer to see that we know how to use them both... in both programs however the famous constraints to sleeve how do they happen? (using beam for beam)

 

[meccanicamg]

actually I used freecad 0.18 with the workbench fem using calculix which is a code based on abacus. In my case, I didn't do a joint analysis, but on the one hand. I don't know how to help you. Surely you will go to put some planar reaction constraints.