Lever Arm Question
Lever Arm Question
(OP)
I have attached a picture outlining a setup that I have a question about.
In this setup, there is a load that is being tilted around a pivot point. It's center of mass is located a bit off body, shown by a dot in the picture labeled CM.
Space being an issue a proposed solution was to extend a tab from the pivot point and pull from it using a linear actuator.
I would like to extend this problem such that if anyone can see any major downsides & issues with this setup that they might share them.
If anyone would like more information, it can be provided as requested.
In this setup, there is a load that is being tilted around a pivot point. It's center of mass is located a bit off body, shown by a dot in the picture labeled CM.
Space being an issue a proposed solution was to extend a tab from the pivot point and pull from it using a linear actuator.
I would like to extend this problem such that if anyone can see any major downsides & issues with this setup that they might share them.
If anyone would like more information, it can be provided as requested.





RE: Lever Arm Question
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RE: Lever Arm Question
RE: Lever Arm Question
your 110deg arc is one limitation on the travel of the linear actuator, the radial distance from the pivot is another.
another day in paradise, or is paradise one day closer ?
RE: Lever Arm Question
I see no big issues with the set up however the linear actuator arm is smaller in the length from the pivot when compared to the length of the arm marked with cm, this means you have no mechanical advantage, if the actuator arm was longer than the latter then you could use a smaller actuator possibly.
RE: Lever Arm Question
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RE: Lever Arm Question
be extra strain on the actuator.
@chicopee - The tab off the main pivot is 4.8". So the 110° sweep it makes as well has an arc length of ~ 9.25". The stroke of the actuator is 8-10". So the radial movements are pretty straight still.
@desertfox - We are pretty pressed for space. I can see either pulling on the tab as shown in the picture or pushing the load up from the bottom as a simple solution. Could you elaborate further. To me having a larger actuator arm and having a smaller actuator are contradictory. Unless you mean the tab length.
@IRstuff - I would like to keep it a [Linear Motion] -> [Rotary motion] mechanism. Getting an extra rotatory motor in the current setup could be an issue.
RE: Lever Arm Question
http://www.wordy.photos/index.php?keyword=dwell%20...
Or having an extra member between the end of the linear actuator rod and the tab?
Is there an advantage to either of those setups compared to allowing the linear actuator to pivot?
RE: Lever Arm Question
another day in paradise, or is paradise one day closer ?
RE: Lever Arm Question
The linear actuator starts extended with the tab at 215° (270 -55) and finishes pulling back at 325° (270 + 55)
RE: Lever Arm Question
another day in paradise, or is paradise one day closer ?
RE: Lever Arm Question
RE: Lever Arm Question
From pivot A to the end of the "dumper" is ~ 21"
RE: Lever Arm Question
RE: Lever Arm Question
fine.
RE: Lever Arm Question
RE: Lever Arm Question
je suis charlie
RE: Lever Arm Question
As shown below.
Such that we get the CM as close to Pivot A as possible to make the motion easy to control.
RE: Lever Arm Question
RE: Lever Arm Question
Depending on how fast you want the mechanism to move and how much mass the linkages have compared to the forces the mechanism is seeing, you could keep a slight positive pressure on the annular side of he cylinder to act as a counter balance when the CM point goes over centre which would remove the requirement for adding physical masses to the system.
RE: Lever Arm Question
As for the product. It has negligible weight compared to the container that is moved holding it, and the arm holding the container. I really didn't like the forces I saw with the original system. However. there is more inertia with the Counter Weight and doubling the mass of the system to get the CM at the pivot might not be worth it. I am informed that we had air cushions helping before as the CM went over the 90°, so we had back pressure helping before.
So next question: If instead of using a large counter weight to pull the CM back to the pivot, I used a smaller CW facing down to pull the CM at 90° to the pivot, would that solve issues with the CM going over the pivot in the last 20° of the 110° arc? Such that at the top of the front cycle the CM would be directly vertical to the Pivot.
RE: Lever Arm Question
If the answer is a lot of times then look at a rotary indexer with rigid couplings - you are going to bang the heck out of that contraption slamming into cushions on cylinders.
http://www.camcoindex.com/ID_PARA.HTM
RE: Lever Arm Question
I really do like the idea of a rotary indexer, there simply isn't the room for one. In addition cost becomes an issue too. The cylinder might cost us 80$ and be over designed by x8-12.
Rotary motion means gearbox, servo, wires.
I think if the project allowed to flip the product and have a next indexed set of arms ready for another, it would be great.
Still, this exercise has shown that a counter balance reduces the overall force on the cylinder and would be a good option for certain future projects.
It also allowed us to redesign the arm such that the Center of Mass did not move past the vertical.