Author Topic: Linear Actuator construction  (Read 4299 times)

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Offline vamsilakshyaTopic starter

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Linear Actuator construction
« on: April 05, 2010, 02:48:01 AM »
Hi

I am looking to construct a linear actuator. My basic requirement is to use 2 linear actuators to raise and lower the panel along one single axis. So if any can guide me to the right resources where i can design the required components for the linear actuator. I am medium lvl user of CATIA.

if it helps the panel size 1490 * 655 * 35 mm.... and 12 kg weight.

if any further details needed please let me know.

Offline nottoooily

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Re: Linear Actuator construction
« Reply #1 on: April 05, 2010, 04:51:54 AM »
Half the problem is restraining it from movement in the wrong directions. If you do that right you only need one actuator.

I'd tend to lean towards wires and pulleys, tho you need rails to slide along.

Threaded rods can be helpful if you don't want it to fall down without power. Or use a gearbox with a worm gear in it.




Offline Soeren

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Re: Linear Actuator construction
« Reply #2 on: April 05, 2010, 08:21:17 AM »
Hi,

Just to add...
If the panel are hinged in one side, it should be easy to do - just use a counterweight. Properly balanced, you can make do with very little power, whether it's coming from rope and pulleys, a linear actuator or whatever.

Linear actuators are quite expensive, compared with other means, so if a regular (geared down) motor could be mounted on aforementioned counterweight, you'll save money and trouble.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline nottoooily

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Re: Linear Actuator construction
« Reply #3 on: April 06, 2010, 02:05:44 AM »
Good point. Why waste all that power. Also applies to wires and pulleys. Like the old draughtsman's easels with cylindrical weights threaded on the wires.

Another concern, if it's aesthetic (A TV???), is resonance. I've seen somebody's fancy hot-rod with an electric bootlid, but it bounced around as it opened, really weak and ugly looking.


Offline vamsilakshyaTopic starter

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Re: Linear Actuator construction
« Reply #4 on: April 06, 2010, 11:11:14 PM »
Thanks for the suggestions. I am very new to this . I am from India and from a city where i don't have much options to choose from.

I am trying to make a solar tracker which should be inclined at 14˚ and still be able to rotate it on a single axis (around 140˚ of total rotation of panel). what kind of hinge or joint or support I can use for panel rotation. I have very less knowledge about the mechanical stuff. So Any suggestions will help me a lot.

If I just use 1 linear actuator...how can i decide the thread thickness and pitch for the linear actuator shaft. what should be used to hold it different angles. As mentioned before the panel weight is 12-13kg.

I will be grateful to any kind of help that can guide me to my objective.

Thanks.

Offline nottoooily

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Re: Linear Actuator construction
« Reply #5 on: April 07, 2010, 03:37:00 AM »
For the hinge I'd just drill some nylon bushings. Or even steel on steel might be fine with a bit of grease. Or steel shaft in wooden holes. Anything really!

You should really use a counterweight. Then the weight of the panel won't matter for the actuator. Friction in the bearing, friction in the threaded rod and error in the counterweight are probably the biggest factors influencing the force requirements. Calculate using tangential force = torque / radius. Do the force calculation for extreme points in the travel because it might get pretty tight with that wide range of motion.

You also need to make sure it doesn't break in the wind. You can do some really rough drag coefficient calcs (see Wikipedia) to estimate the force based on the maximum expected wind speed.

Or you can just get any old threaded rod you find. I don't know if you can be bothered calculating things, intuition can be enough.


Offline Soeren

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Re: Linear Actuator construction
« Reply #6 on: April 07, 2010, 08:31:10 AM »
Hi,

I am trying to make a solar tracker which should be inclined at 14˚ and still be able to rotate it on a single axis (around 140˚ of total rotation of panel). what kind of hinge or joint or support I can use for panel rotation. I have very less knowledge about the mechanical stuff. So Any suggestions will help me a lot.

If I understand you right, that the solar panel is to be rotated with a steady inclination, you don't need a linear actuator.

This can be made from whatever you have (Water resistant plywood would be great):

Better resolution
A large cogwheel and a heavily geared down motor (DC or whatever) can be used, as you want 0.0007 RPM (1 revolution in 24 hours) to follow the sun.
You will need some circuitry to control it of course and you will want to close the open side of the panel support to make it wind resistant.
The board shown should run on a similar board where the center axle keeps it in place.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline waltr

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Re: Linear Actuator construction
« Reply #7 on: April 07, 2010, 10:30:16 AM »
Quote
I am trying to make a solar tracker which should be inclined at 14˚ and still be able to rotate it on a single axis (around 140˚ of total rotation of panel).

Ah...a solar tracker. The design proposals are very close to what is called a 'barn door tracker' used for wide angle astrophotography with an SLR camera. Do a search on that term for some designs.

Offline Soeren

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Re: Linear Actuator construction
« Reply #8 on: April 07, 2010, 01:32:43 PM »
Hi,

It seems all the Barn Doors are of the gull wing type (like on a Lamborghini ;)), as they're only controlled vertically.
The solar tracker is controlled horizontally instead (and will only work well in a "narrow" belt around equator, due to the fixed vertical - or it should have both axis controllable to maximize output).

If you have seen photos of stars from a steady mounted cam, they are circle segments (at least when closer to the poles) and it seems that the Barn Door contraptions are only good for 10 min. max. for that reason.
A better approach would be to control both axis (entering the position of the object in question) as it would allow much longer exposures. It would take a really steady foundation though.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline waltr

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Re: Linear Actuator construction
« Reply #9 on: April 07, 2010, 02:55:10 PM »
Correct on all counts Søren. There are other factors to consider in astrophotography but are beyond the scope of this tread.

The one relevant point is that the astrophotography barn door trackers have the hinge aligned parallel to the Earth's axis therefore only a single motion is required to track the Stars (actually countering the Earth's rotation). This is also know as a Polar aligned mount.

Offline vamsilakshyaTopic starter

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Re: Linear Actuator construction
« Reply #10 on: April 07, 2010, 11:05:03 PM »
@soren.

I am not planning to make dual axis tracker for this experiment.. The reason I was asking for some design that involves linear actuator is, I got a friend who can make a linear actuator if i can guide him well enough with exact process & specifications. And right now I only want to try single axis tracker. I already have another panel fixed at 14˚ inclination which is good for my place around the year.

I now want to make another panel at same inclination and track the sun from morning to evening from east to west. This is what I want to do so I can compare the efficiency increase between fixed and single axis tracker.

I have to use linear actuator as it is part of the project My prof wants. I know we can use other options, but any help that i can get in making this possible will be appreciated.

Thank you to all for your suggestions.

Offline nottoooily

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Re: Linear Actuator construction
« Reply #11 on: April 08, 2010, 02:41:10 AM »
You can still use a linear actuator because it's rotating less than 180 degrees.

Offline vamsilakshyaTopic starter

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Re: Linear Actuator construction
« Reply #12 on: April 08, 2010, 05:30:16 AM »
yeah @notoooily thanks for the options about the hinges.



 


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