Hydraulic Scissor Lift Design

Go to www.globalindustrial.com, they have lifts for sale $ 250 & upwards to $2500 depending on the lift/weight requirement & model. Get their detailed broucher and do what you want.

www.engineersedge.com/mechanics_machines/scissor-lift.htm - 11k -

Try these guys which includes a diagram

thanks for the link, i got the force exerted by the hydraulic cylinder, now how do i calculate the stresses in each member of the scissor arm

If you have to design one, the place to start is by looking at and examining scissor lifts that are currently made. You want to avoid reinventing the wheel. Many new engineers when handed a project assume that originality is expected, when it is really something that works and can be made within budget that is wanted. Your creativity will find avenues for expression in the process of executing your "copy". Otherwise, you are turning a relatively straghforward project into a development program, re-tracing the many steps that have already worn a path.

"Copying", reverse engineering, and modifying existing designs is big part of everyday engineering in practice, as it should be. Its not like you are stealing their prints to "copy" something.

If you look carefully at exising designs you will also find areas that you might want to "improve" upon in some way. Just don't start from scratch.

i understand your point. but getting hold of an existing design to study is virtually impossible. i have searched the internet quite a bit in this regard but found nothing. perhaps you could suggest some source.

If as in your case you can't get to one to examine it (have you tried local equipment dealers and/or companies or contractors that use them?) then the next best thing would be by ordering sales literature and working from that. That is what I meant by "copying" existing designs. I assume that when ordering such literature you wouldn't say "because I want to copy your design".

Many companies when designing a product for an existing market will order (and pay for) existing equipment for the sole purpose of testing and reverse engineering it, and also as a means of comparison for their design. Often for obvious reasons, it wil be ordered through a third party, but not always. You gave no indication as to the size and capacity, and whether it was to elevate people or just objects.

However if you have to ask "How do I calculate the stresses on the scissor arms?", then in all honesty, you shouldn't be designing one in the first place. You might well injure or kill someone! Even lifts that only raise objects do so in the immediate proximity of personnel.

Yes immitation is the sincerest form of flattery, but get the to a hydraulic manufacturer/distributor such as Sperry Vickers for deceleration valves, velocity fuses-for failsafe drop speed in the unfortunate event of a hose failure, for cylinders there are many manufacturers-but you need to follow these rules:

four wheel hydraulic drive wheel motors

operator safety is first and foremost

machine balance is also foremost. especially if one desires to design a scizzor lift with a rotating power platform integral with the design.

dual operating stations is a must-one on the base and one on the work platform.

Foam filled tires etc.

Double acting hydraulic cylinders will require velocity fuses in line with the hoses. The cylinders will need to be oversized in length to allow for stop tubes in the cylinder gland side of the hydraulic piston-this allows for a stronger cylinder and near zero wear and strain on the cylinders packing gland

The hydraulic cylinders have to have pistons with multiple single piston packings for both directions of travel rather than compression packings for the cylinder packing gland and cylinder piston

all hoses need to be loom clamped to the frame rails.

If a large platform is desired a sytem of self leveling outriggers is a must.

many more things especially with regard to insurance and their requirements as well

treating it-the scizzors lift like a crane. so they are good place to start first.

One more additional commit,

In the USA, the man-lifts (at lease the newly make one) are required by law to have a "tether point" so that a person go into a lift must be tied off with a lanyard. Those tether point must be certificate to withhold X amount of force. something to keep in mind.

MidniteFighter

Why not go to an equipment rental yard; take all the time you need to look over the lifts; take photos and make notes; Get as much detail as needed. Yard employees and others might even give suggestions for improvements and problems to be solved.... Then take off (your project) from there.

Either go out and buy one for $1000-$1500 or keep up with your experiment of trial & errors. With my knowledge of bicycles I cannot dream of taking out Mercedes.

Is this an Engineering class project? It sounds that way seeing as your best bet otherwise would be to buy an existing one (why re-invent the wheel and do all the research into pneumatics, safety catches and the like for a one-time project).

How do you determine stress in the members? Your textbook has equations for that. Scissor-lifts are basically a movable truss. You need first to determine what your maximum load is going to be and then how fast your lift will accelerate up (acceleration adds to your stress at max. load). Always use a safety factor in your design to account for unknowns, errors inherent in classic calculations, minor defects in materials, and the fact that the end-user will more-than-likely exceed maximum designed forces once or twice.

Use the already-mentioned advice - measure arm lengths, thicknesses, angles, and whatever you can get your hands on from pictures or actual lifts you find in a junkyard. Pictures can be measured and the relative lengths used to give you a starting point. Good luck!

I would suggest you to study some related standard and rules for scisor lift if you want to start any design calculation. You may start asking around or search internet for something called Elevating Work Platform. I forgot what is the code for the standard but it definitely have. Anyway I attached a link for your reference

http://capsnet.usc.edu/LabSafety/ElevatingWorkPlatforms.cfm

You may want to refer to some standard and rules for crane or Mobile Work Platform also. You can fine lots of rules and method of calculation regarding this. If you really want to design one, you should be able to figure out the load on each link on your own. If not, please don't try to do it. You might killed someone with that. Cheers

We've had a swarm of hydraulic lift design questions in the last few days -- several of them apparently from the same source, or at least the same school. My view is that student problems like this are best handled at the school, using the school's teachers and other resources. My personal opinion is that a valid use of this site by a student is to get additional info or to clear up misunderstandings. For example, a student might come here to say that his teacher described a phenomena in a particular way that seems confusing. He or she might ask, "is there another way of looking at it". When we answer such a question, we help the student, and the student has clearly made a valid effort.

But when the assignment is to design a scissors lift, and the student does not know where to start, I think that is a problem that needs to be solved at the school/student level. Did the student not pay attention in class at all? If we simply supply answers, then we are doing some of the design for him, shortchanging his own educational process.

Just my opinion.

mr Blink SIR,

dont mind if i'm rude. i dont know if you completed ur degree in afganistan or some other place but i dont think u realize, theoretical knowledge given out in engineering classes does not give u the practical know how to perform an actual task in the industry. it rather provides fundamentals concepts. projects are given to students to help them for this very reason. now who are the best people to guide you with the industrial approach to tackle a problem but the people in the industry. definately not the theoretically minded professors.

i did not ask anybody to design the lift and give me, i specifically asked for guidelines.

Just my goddamn opinion

P.S.for ur convinience and to avoid subjecting you from more such irrational queries..this is going to be my last post.

thank you others you hav been helpful

Sorry, George2Paul, my intent was no to offend you. I'd assumed you were a student because you gave so few details initially regarding the project. Such a project is an excellent student project, because it integrates an understanding of hydraulics, leverages, (especially leverages that change with lift extension) allowable stresses, etc. And if the student fails in the project, no one is likely to be harmed.

On the other, some scissors lifts (obviously man lifts, but many others) can have many liability issues associated with them, so their design is not to be taken lightly. Ordinarily, at least in the companies with which I have worked, the overall design of a man lift would be given to a team, and the junior members would work on areas well within their competence and experience level. The more senior members would have directly relevant experience. So, at least in my experience, someone in industry would not be given an assignment in an area in which they do not know where to start. The fact that you said you did not know where to start, reinforced my hunch that you were a student.

A third factor leading me to think you were a student is that in a typical company that manufactures scissors lifts, nothing is designed from scratch, so the question had the theoretical aspect of a student assignment.

So, you can probably see how I might have concluded this was a student project. I can see how you might be offended if you are have a mechanical engineering degree. But in any case, my apologies, and good luck in your endeavors.

Before you go...

Perhaps what might hang a person up is getting too deeply, too quickly, into the "engineering minutiae." Like any other project, design or otherwise, a good approach is to simply see or envision what a final product might look like. Look at existing versions if they are available. Then try to break the result down into constituents--which might be subsystems (the engineers approach--sometimes called reverse engineering) but need not be (the inventor's or creator's) approach. Work out the analytic/engineering details on these smaller parts of the whole. Finally, integrate the smaller results, stepwise or all at once (as the complexity of the final design dictates) into the greater whole--often the integration process will reveal things missed earlier as well. (Don't be disappointed to find that design can be a lurching to and fro process.) Finally, test and revise, and test again. You will find there are many ways to "skin at CAT"; only with experience, and occasional frustration, does one eventually come to most often know the Best ways.

Ken:

WOW!

Judging from the OP's last post you hit the nail squarely on the head!

The OP made a point, but he should have stated where he was coming from up front ...

BTW It great to meet another alumni of Afghan U.! Those were the days .... and the great times we had blowing up those Buddhas during spring break... and our beloved school anthem, sung to the tune of "The Banana Boat Song": "Hey Mr. Taliiiiiii-bannnnnnn tally my buzzzzzooooooka ........"

Well gotta run now ... I hear choppers in the distance ....

(To any Afghan members, no offense intended .. I wish your country the very best, but not so the Taliban)

hello ,,

i have to do the same project and i have no idea what to do could you please give me the steps you used :)