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# using multiple levers coupled to a single shaft5

## using multiple levers coupled to a single shaft

(OP)
Hi,

The attached illustration is my attempt to show a 2D view of a round shaft that passes through ball bearings mounted in two steel frames. To the left of Frame #1, there is an Input Lever that is tightly coupled to the shaft. I am able to apply rotational force to the input lever using an an air cylinder that is not shown in my illustration. Applying rotational force to the Input Lever in turn applies rotational force to two Output Levers that are also tightly coupled to the shaft in between the two frames. The only difference between Output Lever #1 and Output Lever #2 is that Output Lever #2 is farther away from the Input Lever.

I am wondering if anyone here can tell me, in theory and in practice, for a given rotational force applied to the Input Lever, should I expect the rotational force applied to Output Levers #1 to be less than, equal to, or greater than the rotational force applied to Output Lever #2.

Paul

### RE: using multiple levers coupled to a single shaft

If the levers are all the same length then the force will be the same at each.
However you need to check how much torque you are applying to see how much you will twisting the shaft.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: using multiple levers coupled to a single shaft

I'd say it's indeterminate depending on the relative stiffnesses of the shaft and the levers and what they are connected to.

### RE: using multiple levers coupled to a single shaft

force on output levers will react applied torque (about the axis of the lever)

### RE: using multiple levers coupled to a single shaft

Depends on the relative stiffness of the shaft and levers to the forces. If this is the typical text book question with frictionless pivots and infinitely stiff and massless beams then you will get the same output at both levers. However, in reality you have some additional compliance between output 1 and output 2 then output 2 will always have a little less travel and force.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

### RE: using multiple levers coupled to a single shaft

The sum of the two output forces will equal the input force. The output forces will be determined by the load or the input depending on how the forces are applied.

### RE: using multiple levers coupled to a single shaft

(OP)
Hi CompositePro, dgallup, rb1957, BrianE22, and EdStainless,

Thank you all for your responses. You have all been very helpful to me. The two output levers in my simplified sketch are used to move front and rear swingarms that press a non-driven/free-spinning rubber covered roller against a driven roller in a web handling application. My customer has been having some web steering issues that I suspected might be related to the force applied to the front and rear swing-arms not being the same and also possibly the travel not being the same. As most of you seem to agree that while in theory the force should be the same, in reality, neither the shaft nor the couplings can be infinitely stiff, so most likely, some degree of twisting occurs. I am going to suggest replacing the single actuator (air cylinder) that moves both swingarms using a common shaft with a dedicated air cylinder and mechanical stop for each swingarm (front and rear). This will provide them the ability adjust both the travel and the force on both swingarms independently. I think this will give them much better ability to adjust the gap and the force between the two rollers at both the front and the rear, and I think this has a good chance of solving their web steering issue.

I really appreciate all of your help. Thank you again!

Paul

### RE: using multiple levers coupled to a single shaft

umm, I don't think anyone's said at the force on the two levers is the same. It could be.

The two levers should rotate the same, almost certainly do, but don't Have to.

The load in the two levers depends on the resistance the levers experience.

### RE: using multiple levers coupled to a single shaft

Providing more things to twiddle with means more things will be twiddled with.

And every twiddler will have their own idea of what the right twiddle settings are.

Meaning the steering will never be right.

Crown the roller.

### RE: using multiple levers coupled to a single shaft

Crowning is not likely to be a suitable solution here. This sounds like a mechanical alignment problem with the rollers. We can't help you there without many more detailed drawings.

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