Vertical Movement: Alternatives to Using a Cam

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Discussion Overview

The discussion revolves around alternative methods for achieving sinusoidal vertical movement of a thin box, specifically in the context of a school physics competition. Participants explore various mechanical solutions beyond the use of a cam, considering factors such as frequency, amplitude, and budget constraints.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant suggests using a jigsaw or reciprocating saw as an alternative method.
  • Another proposes a linear actuator for precise control over frequency and amplitude, noting it may be expensive.
  • A participant questions the budget and specific requirements, indicating that a linear actuator could meet the needs but at a higher cost.
  • Concerns are raised about the feasibility of achieving 5cm amplitude at 10Hz, with a participant calculating that this would result in high acceleration, potentially damaging the box.
  • A clarification is made regarding the box's material and weight, which is a thin perspex box weighing about 500g.
  • One participant calculates the maximum acceleration for the proposed parameters and discusses the limitations of using a cam to keep acceleration below 1G.
  • A suggestion is made to consider using a bicycle crank as a mechanical solution.

Areas of Agreement / Disagreement

Participants express varying opinions on the best method to achieve the desired movement, with no consensus on a single solution. Concerns about the structural integrity of the box at higher frequencies and amplitudes are shared, indicating a general agreement on the need for careful consideration of these factors.

Contextual Notes

Participants discuss the limitations of different methods based on the physical properties of the box and the mechanical solutions proposed. There are unresolved considerations regarding the maximum allowable acceleration and the implications for the box's design.

Who May Find This Useful

Individuals interested in mechanical design, physics competitions, or those exploring alternative methods for creating controlled motion in experimental setups may find this discussion relevant.

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Hi

I have a thin box (e.g. like an A4 book) I would like to shake up and down sinusoidally. At the moment I have a flywheel connected to a beefy motor. I have tried using a cam to do it but it has proven not so ideal. What other methods can I use?

Thanks
 
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Buy a jigsaw or a reciprocating saw.
 
What's your budget? What period do you need? What amplitude do you need?

You could buy an linear actuator and have complete control over all those parameters. A little bit expensive that's all. :-)
 
Yea its for a school physics competition - so I am keeping things as simple as possible - 1 to 10 Hz and about 5cm max of amplitude?
 
5cm and 1-2Hz seems possible with an actuator. But will be expensive.

Depending on the mass, you could also use a spring?

5cm and 10Hz is quite fast... are you sure your thin cardboard box won't fly apart?
 
Oh just to clarify, its a thin perspex box which weighs about 500g?
 
At 0.05m peak to peak and 10 Hz, the maximum acceleration is
(2 * pi * 10)^2 * 0.05/2 = 98 m/s^2 = about 10G.
You will need a rigid connection that can pull the box down as well as push it up, and the force on the box will be 10 times the weight of the box.

For a simple cam you need to keep the acceleration below 1G, otherwise the box will lift off the cam when it is moving down. That will limit you to about 3 Hz with an peak to peak amplitude of 0.05m.
 
Why not use something like the crank off a bicycle?
 

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