Can a Pulley System Replace Hydraulic Rams for Mechanical Lifting Without Power?

[jrmichler]

Before sizing parts, you need to calculate the loads on those parts. The next step is a free body diagram (FBD)(search the term). This will take some time because there is a lot to learn. Expect that you will need at least three FBD's, one each with the door closed, one with the door fully open, and one with the door half open.

 

[Lnewqban]

I see that the location of the door and of the hinge have changed some respect to the original idea.
I am not sure that such set up will allow the angle of opening previously discussed.
Working on scale drawings will help us to help you.

You will need to calculate the resistance to bending of the structural member running sideways, as well as the rigidity of the area supporting the tripods guiding the cables.
Therefore, you will need the vertical component of force exerted by the cables on the tripods when the doors are in horizontal position.

Besides taking the steps properly advised by @jrmichler above, I would again suggest a wind load calculation prior proceeding to final phase of the project.
It seems that you have many details to solve before stepping into it, making changes latter can be expensive.

Since in your other thread you have mentioned weight of piece of sheetmetal to be handled by two persons, I would like to know what that part is and why the need for on-site manipulation.
You will need to calculate the weight of the tripods as well, reducing it as much as possible.

Regarding your question about the pipe-round bar hinge: that greatly depends on the kind of welding you can achieve against the sheet metal of the original box, as well as on the best possible alignment of the several hinges.
That was one of the reasons for which I have asked you previously about the fabrication capabilities that are available to you, on-site and in shop.

 

[Tom.G]

Oh, I just realized that wind loading on the open overhead should also be checked with the wind coming from the front, open part, of the device. If the wind blows the overhead to vertical and then stops, the vertical will fall down towards the closed position, putting a peak load on the cables, etc.

Cheers,
Tom

 

[Yashi234]

Oh, I just realized that wind loading on the open overhead should also be checked with the wind coming from the front, open part, of the device. If the wind blows the overhead to vertical and then stops, the vertical will fall down towards the closed position, putting a peak load on the cables, etc.

Cheers,
Tom

Hi Tom, Michler and Lnewqban,

Thank you very much. Here is the link of video i found to determine torque which fits my situation.
As far as wind loading is concerned, its 80kmph which comes to 62N. Another piece of info is, when its in upright position, it will be held by 2 pivot points on end of each extension so its 3 way hold. So there is 25mm thick lug on either side of winch path n same on the overhang plate. Once in upright position, they will be tied by cables n chain to secure it.

To all 3 legends, i hv final few queries.
1. Can you tell me what is SWL lifting lugs will be required to lift it ? 2 T rud lug shud be gud enough to weld on overhang plate to lift it ?
2. Can you tell me what info does Torque calculation reveal ? I mean if i use above video n calculate torque how do i use it ?
3. Can any of you show me rough calculation of pulleys based on 140 deg of lift and 350 kg using 2 pulleys. Weight of tripod to mount pulley is just 50 kg. Most pulleys calculation is vertical loaded. This is different n i cudnt find any equation to show if this system will work.
4. What is difference between rated lifting capacity n pulling capacity ?

Thank you in advance.

Regards,
Yashi

 

[Lnewqban]

Hi Tom, Michler and Lnewqban,

Thank you very much.
...
2. Can you tell me what info does Torque calculation reveal ? I mean if i use above video n calculate torque how do i use it ?
3. Can any of you show me rough calculation of pulleys based on 140 deg of lift and 350 kg using 2 pulleys. Weight of tripod to mount pulley is just 50 kg.
...

You are welcome, Yashi

Answer to question #2:
Your metal box has no anchoring to ground or concrete base. High velocity wings could overturn the box, especially while the door is open and weight is not balanced, hurting people standing close to it.
Please, take a look at this article:
http://edge.rit.edu/content/P14414/public/Reference Documents/windtestofharborcontainers.pdf

Answer to question #3: Based on dimensions of box and positions of door, knowing weight of each, you should produce a free body diagram.
That will give you an idea of the forces that the wire-rope, winch, hinges, support of pulley, roof of box and bolts will “feel” for different positions of the heavy door, while opening and closing it.
Please, see:
https://courses.lumenlearning.com/s.../chapter/12-2-examples-of-static-equilibrium/

Until you complete those steps, you are can’t know how to dimension hinges, anchors, structural re-inforcement, etc.
You need to have some values of forces for many critical points, even if they are not too exact.

Even the amount of wire-rope that should be admited in the drum of the winch depends on its capability (how many turns before becomes full) and the location of anchors to the door and the geometry of the mechanism.

For all those reasons, nobody could properly answer your questions without seeing scaled drawing and calculated forces.

It seems that you have already designed and dimensioned the tripod.
The weight of the tripod (50 Kg) is excessive for two workers to carry it from ground to roof using only ladders.

 

[Yashi234]

Thank you all,

Will send you updated drawing with dim to get you an idea. I have to use rud lug to lift overhang plate. I calculated torque to 2.2 kNm each so will the rud lug of 3T on each be sufficient ? How to determine what size rud lug to use ? It will be weld on.

Second question come to my mind is pulley has to tight fit (bearings and sheave and screws) or need to have movement for load carrying ?

Do we get readymade mounted pulleys like d one attached with bolt holes on ground or have to build around sheaves ? For 8mm rope you need 100mm dia or 4in dia sheave.

Regards,
Yashi