# Questions about using an Inertia Wheel to apply a compressive linear force

• Thesla
In summary, the dimensions of an inertia wheel are unknown, but it is supposed to provide a very strong pushing force when coupled to a linear actuator.
Thesla
TL;DR Summary
How to define dimensions of an inertia wheel
Summary: How to define dimensions of an inertia wheel

Firstly, I have been working in aviation industry, making me to involve in the Physics a lot. For the last few weeks, There have been a problem to solve since the manfacturer had not wanted to help us by not sharing information. We have asked them for information about dimension, weight and material that the inertia wheel is made of but nothing has been received back. All we know is that we are supposed to apply a load of 36000 lbf to the part circuled with red in direction of extend then retract in turn. Well.. What is the purpose of inertia wheel here, and how can we decide the dimension, weight and the material to produce it?

Sincerely.

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Welcome to the PF.

Could you provide the make and model number of that test machine? Which standard is it meant to test to? What is the nature of the unit under test? It looks like some sort of impact stand for testing mechanical assemblies, but I'm not familiar with that kind of test. Thanks.

Thanks for the welcoming me here.

Well, in fact there is no specific model for the set up, at least, manifacturer of the unit that is to be tested is not willing to share it with us due to commercial reasons.

Unit being tested is an actuator that provides rotational moves for flight control surface of the aircraft known as Rudder.

I just wondered if it is possible calculate dimensions of the wheel, and its purpose to be attached to the set up.

Thanks.

So is the energy stored in the wheel in order to provide a very strong pushing force when coupled to the linear actuator mechanism? Or am I reading the diagram incorrectly?

If so, then you could get an approximate idea by figuring out the energy dumped into the linear actuator (via the rated pushing force and the length of the stroke), and equating that to the energy stored in various size spinning wheels (via the MOI and angular velocity). That will get you close to understanding what the wheel dimensions, mass and spin rate could be. Does the wheel dump all of its energy in a rotation or two?

Prehaps the load unit mimics the aerodynamic forces and the inertia wheel dynamically models the mass of the stabilizer? Just a guess...

Source of the mentioned load is another actuator, and between these two actuators there is the inertia wheel converting the linear force to angular one. When the UUT is kept retract position with hydraulic pressure of 3000 psi, we are supposed to apply a load of 35000 lbf in direction of extend with a load actuator coupled with the inertia wheel. Other than this, we unfortunetely have no any more information. I have not had the chance to observe the test yet. That is why, I am not able to tell you more.

hutchphd said:
Prehaps the load unit mimics the aerodynamic forces and the inertia wheel dynamically models the mass of the stabilizer? Just a guess...
It must be as you guess but how it helps us to design the wheel?

You are not (or cannot?) provide us with enough information to design the inertia wheel. In order to help you design an inertia wheel, we need a diagram showing the force (torque?) of the load unit, the force (torque?) of the rudder servo control, where and how those forces/torques are applied to the inertia wheel, the acceleration of the inertia wheel in radians per second squared, the torque of the inertia wheel, and any constraints on the dimensions of the inertia wheel. If it is for testing a rudder servo control, then the maximum speed of the inertia wheel is probably not important, but you should find that anyway.

Be aware that when an actuator is connected to an inertia, you need to design for end of travel. If the actuator is moving at speed when it reaches end of travel, things can break. I know of case where the engineer did not take that into account. His machine reached end of travel, sheared a dozen 3/4" bolts, and dropped slightly over a ton of machine with a large BOOM. Unfortunately, it happened in the customer's plant.

berkeman
There seems to be a bit of a cross issue here; in that, you either have the manufacturer's machine in question, in which case you have no need to "design the wheel", or, you are attempting to copy the manufacturer's machine without fully understanding the complete science and application parameters for the elements of the existing machine.

berkeman
JBA said:
There seems to be a bit of a cross issue here; in that, you either have the manufacturer's machine in question, in which case you have no need to "design the wheel", or, you are attempting to copy the manufacturer's machine without fully understanding the complete science and application parameters for the elements of the existing machine.
We have to copy the test set up about which the manifacturer provides no information at all with us. They express it is a industrial property cannot share any information regarding it without a contractual agreement. Even though we requested training on the UUT to observe the whole test and the set up, they rejected without any reasons.

It sounds like you are being asked to supply the hydraulics and measurement devices for them to use in their plant.

If that is true, you would need to know the TRAVEL of the hydraulic LOAD UNIT and of the RUDDER SERVO CONTROL.

If you are to supply an assembled unit, you need the distance they require to mount their item(s).

You will also need the SIDE LOAD and any BENDING MOMENT applied to any of the mechanical or hydraulic parts you supply, both static and dynamic.

There are probably more things that I have missed. The mechanical experts here can likely say what was missed.

Cheers,
Tom

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You also need to determine how the inertia wheel shaft is coupled to the longitudinal shaft between the servo control and the load unit.
Who manufactures the aircraft? What model?

## 1. How does an inertia wheel work to apply a compressive linear force?

An inertia wheel works by utilizing the principle of inertia, which states that an object in motion will remain in motion unless acted upon by an external force. In this case, the inertia wheel is attached to a system that applies a compressive force, causing the wheel to spin. This spinning motion creates a centrifugal force that can be harnessed to apply a compressive linear force.

## 2. What are the advantages of using an inertia wheel for compressive force?

One advantage of using an inertia wheel is that it can generate a significant amount of force without the need for external power sources. This makes it a cost-effective and efficient option for applications that require a continuous and consistent compressive force. Additionally, inertia wheels are compact and lightweight, making them suitable for use in various settings.

## 3. Are there any limitations to using an inertia wheel for compressive force?

While inertia wheels have many benefits, they also have some limitations. For instance, the force generated by an inertia wheel is dependent on the speed at which it spins, so the force may fluctuate if the speed is not constant. Additionally, the force may decrease over time as the wheel's energy is gradually dissipated.

## 4. What are some common applications of inertia wheels for compressive force?

Inertia wheels are commonly used in various industrial and mechanical systems, such as presses, clamps, and lifts. They are also used in machinery that requires constant and consistent force, such as conveyor belts and roller coasters. Inertia wheels are also utilized in space missions to provide thrust and control for spacecraft.

## 5. How can the force generated by an inertia wheel be controlled?

The force generated by an inertia wheel can be controlled by adjusting the speed at which the wheel spins. This can be achieved by changing the size, weight, or shape of the wheel, as well as by altering the power source that drives the wheel. Additionally, external mechanisms such as brakes or clutches can be used to regulate the speed and force of the inertia wheel.

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