2 post lift with lead screw and rope drive

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Discussion Overview

The discussion revolves around the challenges faced in a mechanical system utilizing a lead screw drive combined with a rope drive for lifting two carriages. Participants explore the issue of a significant level difference between the power carriage and the follower carriage during operation, particularly focusing on the behavior of the rope under load and slack conditions.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes the operation of their system, noting that the follower carriage lags behind the power carriage due to slack in the rope, resulting in a 50-60mm difference when under load.
  • Another suggests using a take-up device, such as a spring, to maintain tension in the rope.
  • A different participant proposes preloading the wire rope or adding a second screw jack connected via sprockets or gearboxes, while also mentioning the option of using commercially available screw jacks.
  • One participant points out that adding a spring is not feasible due to the clamping connector on the wire rope and the need for the rope to move over a pulley.
  • Another participant reiterates the issue of slack in the rope even after preloading, emphasizing that the rope only tightens under load.
  • Further discussion includes the need for a preload of at least 1000 lbf to minimize slack, and questions about the relative weights of the carriage and load.
  • One participant mentions consulting with the rope manufacturer about preloading and pre-stretching, but indicates that these solutions have not resolved the issue.
  • Concerns are raised about the feasibility and cost of implementing a winch mechanism with a worm wheel arrangement if the screw side carriage is connected with rope and pulleys.

Areas of Agreement / Disagreement

Participants express various approaches to address the slack issue, but there is no consensus on a definitive solution. Multiple competing views and suggestions remain, indicating that the discussion is unresolved.

Contextual Notes

Participants have not provided specific details regarding load or safety concerns, and there are limitations related to the assumptions about the system's design and operational constraints.

mithleshkj
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Actually i am using lead screw drive by motor along with rope drive. If you will see the attachment, yuo can clearly understand the working principle.
In this working priniciple, when we used to start the motor, carriage power use to go up through lead screw drive.Rope is connected to this power carriage which through pulley is got connected to follower carriage.
once the power carriage is going up,it pulls the rope and follower carriage and thus both the carriage is taking the load.
problem what i am facing is that power carriage start going up immediately as i switch on the motor but follower carriage is getting lifted once the rope get tensed and overcome the slackness.
Due to this i am getting 50-60mm level difference between the two carriage.
can someone suggest is there some way to avoid this problem or some other rope which can be used.
I am using steel wire rope 10mm dia for this
 

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Some sort of take-up device (spring, maybe?) to keep the chain taut.
 
Either preload the wire rope as suggested (loop all the way around and pre-tension), or add a 2nd screw jack and tie them together with sprockets and chain (or gearboxes and shaft). Might be simpler to change to purchased screw jacks (Duff Norton, Joyce Dayton, Nook) and tie their inputs together.
Nothing has been indicated regarding load or safety concerns...
 
it is not possible to adda spring as end of wire rope got clamping connector thread rod type to tighten it.also this wire rope will be keep on moving on pulley.
any other way?
 
even after using pre loading wire rope, i am facing the same issue.
rope is getting tightened once load is acting on it. without load, it is slacking
 
mithleshkj said:
even after using pre loading wire rope, i am facing the same issue.
rope is getting tightened once load is acting on it. without load, it is slacking

Preloading eliminates/minimizes slack; ideally the rope will always be under tension. I just noticed that the load mass is 2000 kg. The preload on the wire should likely be at least 1000 lbf (per above you need a full loop of rope) in order to eliminate the slack. Preload doesn't significantly increase drive force required (some due to additional rope mass, pulley inertia and friction), only belt tension and bearing loads (as well as structural loads).

Can you maybe keep the weight of the carriage on the rope at all times? How much does the carriage weigh relative to the load?

How about disconnecting the screw side carriage from the load and adding a rope and pulleys to that side so that both sides react the same way to the load?
 
I have discussed with rope manufacturer and asked them regarding pre loading and pre stretching,but that also is not working out.
#weight can't be kept on carriage all the time as weight has to bring down.when load is not in the carriage,difference of 10mm is cmoing which is going to 50-60mm with load
#if i am connecting the screw side carriage with rope and pulley,than for lifting the carriage up, i have to used some winch type mechanism with worm wheel arrangement to have speed reduction ratio as motor RPM is 1440.the whole set up will be costly.
 

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