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Scissor Lift Design Calculations

09/15/2009 1:35 PM

Hello,

I am designing a single hydraulic scissor lift and require information in order to verify my calculations can anyone guide me in the right direction or assist me in verify my calculations, below are my information.

-calculate the stress and deflection on the scissor arms (what formula and procedure)

-stress and deflection on the platform (what formula and procedure)

-stress on the center pin of scissor lift (what formula and procedure)

-stress on the ram angle (lower where cylinder is attached to - what formula and procedure)

-stress on the lifting arm (upper where cylinder is attached to - what formula and procedure)

Thanks

Richard Fairbarn

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#1

Re: Scissor Lift Design calculations

09/15/2009 2:32 PM

I can't help you with these sorts of calculations, and really those on the forum that can, ought to get paid for that sort of work.

I will say that I have worked with and from scissor lifts, manlifts, lulls, and forklifts, and many workers are prone to take big risks using them, and working from them.

The most common risks taken are workers will drive them when they are at height, instead of dropping down to relocate, so if you want to make a superior scissorlift I'd suggest making one that is safe to move at height if you want yours to be more desirable than the others.

Another risk workers are prone to take is pushing up against weight limits. Many of the scissorlifts I worked from really did not have much weight carrying capacity. My work from them was mostly in Convention centers for Trade Shows where I would be called to tie in feeder cables to Electric boxes in the Ceiling trusses so right there I am called to load sometimes 50 foot hanks of 4 ought up, and three hots and a ground and neutral right there are over the typical weight limits of the typical scissors lift.

I don't mind at all telling you in general terms what might make your new design more desirable than others that I have had the frights from working with in the past.

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#2

Re: Scissor Lift Design calculations

09/15/2009 2:38 PM

Well, unfortunately it sounds like your most likely not qualified to be designing this scissor lift. Someone could be injured or killed if you don't run the calculations correctly.

My advice is consult a local engineer to help you through the process. This forum cannot provide the level consultation you need, as many things will go overlooked, which can prove to be critical design failures.

If you are not sure about those (relatively simple) calculation, then its very likely you are going to overlook some other critical design functions. Hydraulics are dangerous, scissor lifts are dangerous, combining the two in a ill-designed system can be VERY dangerous.

If you do go on without proper consultation, you may look at taking a course on Statics, and strength of materials, machine design, among others, or better yet, leave the design process to someone who has been through the proper Engineering courses.

(sorry If I come off as grumpy, or rude, This is just a potential deadly disaster waiting to happen)

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#3
In reply to #2

Re: Scissor Lift Design calculations

09/15/2009 3:09 PM

RVZ717,

No need to apologize. You very politely resused to answer and explained why you refused to answer. You get a GA from me. I was originally going to go into a homework alert rant but your non-answer is much more approprate. I intend to use your answer as a template in the future.

Again, nicely done.

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#4
In reply to #2

Re: Scissor Lift Design calculations

09/15/2009 3:15 PM

I don't agree RV that no one on the Forum can help this new guy. I just think he ought to put the request for help in Commercial Space as an Advert for Engineering help.

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#7
In reply to #4

Re: Scissor Lift Design calculations

09/15/2009 5:28 PM

I Absolutely agree that there are MANY people on this Forum who CAN, and most likely WOULD gladly help with the design and calculations, in person. I simply said this forum cannot provide the level of help needed, (not any of the people on it).

I simply don't think that a Public Internet forum is the most appropriate place to obtain the amount of Engineering Consultation that the OP appears to need. If it were a single beam deflection problem, or something which can be answered simply, and effectively, that's great, and will definitely get done. However the OP clearly does not have the Technical expertise to take on the task he is attempting, and should seek real help. CR4 is really an Awesome place to get help(and loiter), The people are great, knowledgeable, and sometimes even quite entertaining. I just don't think the Forum can reliably offer every aspect of the design help he needs. Perhaps someone with some extra time can "Telecommute" and spend that time helping to design the lift from the bottom up. I'm sure this is a great place to find that out of work engineer, who would be more than happy looking over the drawings/schematics/calculations and providing the proper guidance.

I wish the best of luck!

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#8
In reply to #7

Re: Scissor Lift Design calculations

09/15/2009 5:57 PM

I agree RV. I thought I explained what might be proper on the Forum by opening my first post by saying if they want work done many here are trained properly and practiced at, put it in the commercial space as if it was a help wanted ad.

I said I didn't mind shooting the sh*t and sharing some of what I know about these machines with them while waiting for a call, and what not.

It had crossed my mind that whomever the OP is, they ought to send somebody a plane ticket, but when checking I found no profile info, and no location.

Awhile back I did suggest to the Administrators that it was my thought that the Commercial Space ought rightly be put in the CR4 section list inbetween Civil Engineering and Communications & Electronics so some new members at least get a prompt.

I mean I myself would think that a guy would know that asking someone to do all the calculations required to properly design something like a scissor lift for nothing, was a bit much.

Again, I agree with you RV, much much more than disagree.

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#6
In reply to #2

Re: Scissor Lift Design calculations

09/15/2009 5:15 PM

GA from me.

This type of request only fortifies by belief that people who do engineering must be a PE or must work under the supervision of one.

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#5

Re: Scissor Lift Design calculations

09/15/2009 3:28 PM

Is it a single or a series product? If single it is too expensive to design it better try to buy, if it is a series product then you should accept to pay for the work.

If you want some body to do it you should indicate where you are since economically speaking it is better to use from the start products available near to the place where it will be build.

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#9

Re: Scissor Lift Design Calculations

09/15/2009 7:33 PM

My request was simply to verify my calculations or anyone who has a set of calculations already done for a scissor lift device. I am quite familiar with statics, strength of material as well as dynamics. The lift has been modeled in solid works and analyzed using Cosmos FEA software, all results were satisfactory. Hand calculations and FBD analysis also seems satisfactory but I am a mechanical person and to me a scissor lift seems more like a structural device but follows all principles of a truss in bending etc. My questions was mainly to anyone in the forum who is familiar with scissor lift.

The lift is a single stage lift, 60" X 80" with a swl of 500lbs uniformly distributed, vertical height is 48"

I just wanted to see how help full this forum would be to me as I know I would of gotten the response I got. Taught I would post my question anyways.

Thanks,

Richard

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#10
In reply to #9

Re: Scissor Lift Design Calculations

09/16/2009 12:28 AM

"My request was simply to verify my calculations"

Let's see 'um.

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#12
In reply to #10

Re: Scissor Lift Design Calculations

09/16/2009 2:42 AM

You made me laugh Lyn.

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#13
In reply to #12

Re: Scissor Lift Design Calculations

09/16/2009 2:56 AM
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#11

Re: Scissor Lift Design Calculations

09/16/2009 2:36 AM

In addition to the geometric calculations (can you provide a sketch and your calcs to date?) there will need to be some additional lifting capacity to overcome various friction loads, as well as to accelerate the main load and and the parts of the lift. There was someone else a while back who asked a similar question. The posts in that exchange showed some example calculations along with an elegantly designed large lift.

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#14
In reply to #11

Re: Scissor Lift Design Calculations

09/16/2009 9:47 AM

thanks tornado, i'll post some sketchs etc. Do you know what post showed the example calculations?

Richard

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#15

Re: Scissor Lift Design Calculations

09/16/2009 11:13 AM

Charlotte asked this in her post "calculations for a scissor lift" back in July of this year. Are you in her class? You might want to search her post and see what advice was offered.

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#16
In reply to #15

Re: Scissor Lift Design Calculations

09/16/2009 2:32 PM

Any other school work you need done???????? Tell the enngineers wat their grade is after! LOL

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