Simple continuous back-and-forth linear movement

[bimusicmaker]

I need to purchase a device that will push something forward and backward continuously, in order to make wings flap like a bird. Linear actuators seem to be the right thing to buy, except these require pressing buttons to go forward and then back. What can I buy/what can I do that will allow a linear actuator (or something similar) to continuously move back-and-forth?

I much rather buy something that already does this than to build a machine or program anything. I would love to buy some sort of slider-crank mechanism with a motor at a reasonable speed already set up. Any advice is appreciated.

 

[israelkk]

Reversing screw,

http://www.abssac.co.uk/p/Self+reversing+screws/8/

http://www.youtube.com/watch?v=zv7cXR1UkWQ

 

[KENAT]

Maybe this will give some ideas, how about looking at windscreen wiper mechanisms?

http://en.wikipedia.org/wiki/Reciprocating_motion

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[IRstuff]

You can actually get a Lego set that does that, but here's a Wiki page for a Scotch yoke:

http://en.wikipedia.org/wiki/Scotch_yoke

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[IRstuff]

If you're too lazy to click on the link, here's the GIF from the article

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[bimusicmaker]

Something like that would be great. The problem is I have no idea where to purchase something like this to put into practical use. Any advice?

 

[IRstuff]

There's a Lego set that does that.

Have you even done a websearch?

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[mcgyvr]

maybe the OP wants to attempt some actual specifications/requirements/physical size stipulations,etc..

But as variety of these types of devices would be huge and volumes low I'm not surprised at all that these aren't off the shelf items anywhere.

 

[bimusicmaker]

The stroke would ideally be around a foot long, frequency would ideally be around 16 rev/min. Force no more than 30 lbs.

Another option I was considering would be to use a linear actuator connected to some sort of device that will reverse polarity every 4 seconds or so in order to achieve this reciprocating motion. I am pretty unexperienced with this sort of thing so any advice would be appreciated.

 

[Compositepro]

It is apparent that you are inexperienced. This is not the place for such basic education. You need to have sinusoidal motion (scotch yoke or similar) for what you are doing; not bang-bang reversals.

 

[BrianPetersen]

Gearmotor-driven crankshaft and connecting rod. You can buy a gearmotor with the right motor, gear ratio, and torque rating, and you can buy the various bearings and such. It is up to you to select the components and design your apparatus around it.

 

[KENAT]

bimusicmaker, not sure if it's quite the size you want but like I said take a look at windscreen/wind shield wiper mechanism.

https://www.google.com/search?q=win...-windshield-wiper-driving-mechanism;1376;1104

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[tbuelna]

There are many types of commercial linear actuators that are capable of producing 30lbf over a 12" stroke at a frequency of 0.53Hz. There are hydraulic, pneumatic or electromechanical devices. But you need to consider the added weight and complexity of the systems needed to power these devices.

 

[LittleInch]

bimusic,

First you need to define your requirement (i.e. think about it a bit more).

Questions that need to be answered are:

do you need the linear motion to be a steady velocity or can you handle sinusoidal motion (scotch yoke, crankshaft etc)?
Is the force constant or variable?
If the force is variable does the velocity still need to be constant ?(pneumatic actuators will vary for instance)
how fast do you need the end of the stroke to convert to the opposite direction?
How fast do you want this actuator to travel at?
Do you need a variable speed or constant?

other than trial and error, this is the way to make sure you get something the right size that works...



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