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Calculations for a Strong Mechanism

11/13/2016 9:18 AM

Hi, We're two students trying to design a mechanism for lifting the head of a vacuum cleaner. But we don't know much about the calculations and mechanical issue to consider. Could you please give us some advice or solutions on that? Any formulas or tips are appreciated. Please consider that we don't have the same knowledge as you; so if possible, please don't skip the basics :p . Many thanks in advance =)

The 1st picture shows a rough look of the final product. Overall dimensions are rough and parts are made just to check if the idea works. We have to do some calculations for all details and then make a new model based on the result. But we aren't sure about the type of formulas we need to use.

Image 1

The 2nd picture gives some info about the joints and the function of the parts in the mechanism. Maybe the video Here can make it a bit more clear. In the video, the curved sloth is suppressed because we still don't have the right curve for it. The movement is close to what we need though. The shape of the head in the video is not correct. The correct form would be something like the green part in the 1st image.

Image 2

We're guessing that the head should stay vertical the entire time, so there be no pressure on point B in the 2nd image.

Extra info: the weight of the head is about 8kg; there will be a gasket on the edge of the tank/drum; the tank should be perfectly sealed when the head sits on it.

These are what we need to find out and could use your knowledge and advice on:

How to calculate the thickness and the dimensions of the parts to make sure that the mechanism works in real life?

How can we calculate the dimensions and the curve of the sloth in a way that the head doesn't rotate and there be zero pressure applied to that sloth?

How can we calculate the pressure that will be applied to the base of the trolley and how to test the design of the base to see if that pressure is not going to break the base?

Here the tricky thing is that we don't know how much force different users will apply to the handle of the lever. But we have to make the system strong.

Again, any advice, solution, source, or formula is much appreciated!

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#1

Re: Calculations for a strong mechanism

11/13/2016 9:45 AM

Take some mechanical engineering courses.

You can't be tutored and instructed about the material properties and mathmatics required for mechanical design.

The knowledge you desire cannot be simply injected into your brains. It must be assimilated by reading, learning and comprehending the material.

In short, do your own homework, or get a fellow materials student to help you.

How to Apply Design Thinking in Class, Step By Step | MindShift ...

Problems of Product Design and Development - Christopher Hearn ...

Find some information be searching the web.

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#2
In reply to #1

Re: Calculations for a strong mechanism

11/13/2016 10:45 AM

Thanks for your advice and the links you shared. My group mate and I wish getting a fellow materials or engineering student was an option. But sadly there is no chance in that happening anytime soon. We'll definitely start looking deeper into documents related to mechanical engineering and continue searching on google as you suggested. So, thanks again.

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#3

Re: Calculations for a strong mechanism

11/13/2016 11:13 AM

There is so very much background and task specific knowledge one needs to know to do a proper kinematic analysis and design. Then again this design does not require a full analysis like a deep space probe might require.

I would start with figuring out the magnitude and center of mass of this upper section. Next I would identify the path this part must take for removal. Only once these details are estimated or known can a kinematic analysis be attempted to find out the torques and forces that must be applied for the desired trajectory.

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#5
In reply to #3

Re: Calculations for a strong mechanism

11/13/2016 11:41 AM

Thanks a lot. So we'll start by finalizing the design and the material of the upper part to be able to indicate the magnitude and the center of mass. Or can we assign a rough number for the weight? e.g. We know that the interior components weigh roughly 8.5kg. Can we say for instance, in the end, the upper part isn't gonna weigh more that 10 and then use this number in the calculations? Or even a few grams extra is gonna make the situation problematic? I understand that it would be a problem if the part is heavier than what we put into calculations as the lifting mechanism may break sooner than expected. But would it be the same if the part is a couple of hundred grams lighter than what we use in our calculations?

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#20
In reply to #5

Re: Calculations for a strong mechanism

11/14/2016 8:30 AM

If you want to be an engineer I suggest you stop using "gonna", as it's not a word!

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#4

Re: Calculations for a strong mechanism

11/13/2016 11:25 AM

Force x distance = work. You know the force (weight) of the vacuum cleaner head you are lifting. What is the component of the force in the direction that that end moves?

So that force x the distance it moves is the same as the force on the handle x the distance it moves. It's just the principle of the lever.

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#6
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Re: Calculations for a strong mechanism

11/13/2016 11:55 AM

These students are simply not equipped to perform this type of design work.

They have no knowledge of materials and have made no suggestions of what they may use in construction. Steel, carbon fiber, wood and even styrofoam are all choices.

"How to calculate the thickness and the dimensions of the parts"

"How can we calculate the dimensions and the curve of the sloth"

"How can we calculate the pressure that will be applied "

"we don't know how much force different users will apply"

all indicate a lack of preparation for this project.

No knowledge of materials, mechanics, applied forces and no background in math all spell doom.

This member has been at this for two months and has nothing to show but some sketches.

They are not prepared!

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#11
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Re: Calculations for a strong mechanism

11/13/2016 2:08 PM

I suspect it's a school project or exercise and not a real product.

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#23
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Re: Calculations for a strong mechanism

11/14/2016 1:38 PM

They are students. The entire idea, at least back in our day, was to learn. Surely they must have a text book(printed or on-line) that has the information required to complete the project, and if all else fails, ask the instructor for some help. The least the teacher can do is point them in the right direction.

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#25
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Re: Calculations for a strong mechanism

11/14/2016 1:44 PM

there was nothing more satisfying than to take information out a reference books, data and cut sheets from venders and suppliers, apply it to your project wondering if you did it correctly.

and then receive a passing grade confirming you did. It builds confidence in college that will be required when you get out in the work force.

btw, I had an incompetent instructor, but I learn from him also, and that was, 'its up to you to figure it out'

After college, that serve me well, wasn't no different that some managers.

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#19
In reply to #6

Re: Calculations for a strong mechanism

11/14/2016 2:11 AM

Few are prepared to '...calculate... the curve of the sloth"...'

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#24
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Re: Calculations for a strong mechanism

11/14/2016 1:40 PM

I'm picturing med school students asking a surgery discussion board to tell them how to fix an aortic aneurysm. I wonder if that happens?

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#31
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Re: Calculations for a strong mechanism

11/14/2016 5:06 PM

CR5, just down the hall.

I suppose if you can talk somebody through landing a plane or delivering a baby, you could talk them through an operation.

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#33
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Re: Calculations for a strong mechanism

11/14/2016 5:56 PM

Sounds good as long as it's not my aorta about to blow.

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#32
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Re: Calculations for a strong mechanism

11/14/2016 5:52 PM

This is urgent, please respond immedi.... ah never mind.

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#7

Re: Calculations for a strong mechanism

11/13/2016 12:06 PM
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#8
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Re: Calculations for a strong mechanism

11/13/2016 1:07 PM

Thanks! And can we do the same simulation in SolidWorks? Or is Autodesk Inventor more advanced on that?

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#12
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Re: Calculations for a strong mechanism

11/13/2016 2:57 PM

The matter of preference I think would be which you had more experience on....lacking any, then you might try both....

http://www.solidworks.com/sw/products/solidworks-conceptual-design.htm

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#28
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Re: Calculations for a strong mechanism

11/14/2016 2:32 PM

Thank you :)

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#9

Re: Calculations for a strong mechanism

11/13/2016 1:07 PM

:p and =) ? Are those some new form of scientific notation?

Before you spend a lot time and effort on this, you should do a patent search. Then you'll need to start with the basic understanding of what you want to design. Then you need to apply that knowledge with your construction skills and build a proto type for your R&D research.

Now, if nobody has a patent design on your invention, then you should keep your idea a secret, this is an anonymous world wide fourm and somebody who has the knowledge and understanding of what you want to do, will file a patent on your idea and make you pay for it in $$$!

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#10
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Re: Calculations for a strong mechanism

11/13/2016 1:31 PM

Good points! Thanks =D

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#21
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Re: Calculations for a strong mechanism

11/14/2016 12:12 PM

I shoud have added a footnote to my comment. The definition of R&D is; Reconstruct and Destroy .... reconstruct and destroy ......

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#22
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Re: Calculations for a strong mechanism

11/14/2016 12:21 PM

That's Really Dumb.

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#26
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Re: Calculations for a strong mechanism

11/14/2016 2:09 PM

I know, but that's all that department does, in the name of research

As an inspector I would have sign off on their destruction success, then listen to the production manager going ballistic because they destroyed "his" new machines

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#13

Re: Calculations for a strong mechanism

11/13/2016 3:37 PM

As students, your first mistake is that you did not start with kinematics, but design the part first and then kinematics

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#14
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Re: Calculations for a strong mechanism

11/13/2016 5:06 PM
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#17
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Re: Calculations for a strong mechanism

11/13/2016 7:19 PM

Yes, Would have been a good start and it's not too late to start over with kinematics.

hey, I've found out that it's quicker the second time around.

The work isn't wasted, the OP's are in school, that's where you can trip up without a reprimand.

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#15

Re: Calculations for a strong mechanism

11/13/2016 5:52 PM

There are two routes no 3 in designing. There is a hard way. There is an easy way. There is the easiest way, though not all the time the cheapest.

1) Hard way - do some machine design (static and or dynamic analysis)- wherein the weakest link is critically the strongest in an assembly. This is pure math, practical consideration, and common sense.

2) Easy way- You have drawn this product pretty neat, run some simulation, FEA perhaps. Couple of opensource software is available in the web (ex. Salome, Paraview, OpenFOAM), needs common sense also.

3) Easiest way - Build by trial and error then conduct a test (reliability test perhaps)

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#29
In reply to #15

Re: Calculations for a strong mechanism

11/14/2016 2:35 PM

Thanks! Will start from the 2nd way.

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#16

Re: Calculations for a strong mechanism

11/13/2016 6:26 PM

Put a handle on each side and just lift manually.

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#18
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Re: Calculations for a strong mechanism

11/13/2016 9:36 PM

...or a door on the front to remove the filter....or a front door and a back door....

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#34
In reply to #18

Re: Calculations for a strong mechanism

11/15/2016 11:54 AM

OK one more , what about a side mounted filter...a filter mounted on the side of the canister with an opening container that would make the filter easily accessible....the filter housing need not be protruding, it could in fact be incorporated into the cylindrical shape...but easily removable...

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#27
In reply to #16

Re: Calculations for a strong mechanism

11/14/2016 2:16 PM

Put a fork in it and call it done.

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#30
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Re: Calculations for a strong mechanism

11/14/2016 3:39 PM

I gotta' go walk Porky anyway....Heel! heel!

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