Author Topic: Heliostat Design(s) [Work in Progress]  (Read 19928 times)

Gabriel

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Heliostat Design(s) [Work in Progress]
« on: October 08, 2012, 11:56:00 AM »
Hi All,

Well, the Sun Tracking / Heliostat Program is mostly finished and fully functional, and the Sun Tracking / Heliostat Electronics are also pretty much done, so the next thing on the agenda is to come up with some machine designs.

There is, of course, this heliostat design http://www.cerebralmeltdown.com/heliostatprojects/Heliostat%20plans%20V2/default.
Since you only really need a saw and a drill to build the thing, it is accessible to most everyone who has basic construction skills.

There are some downsides though such as:
the lead screws would freeze in the winter
the lead screws tended to get bent easily which resulted in wobbly movement
the machine is very slow
the range of motion for the azimuth motion is restricted

Of course, many of these downsides could be overcome just by making some relatively minor changes to the design, which is something that I hope we will discuss here.


Another thing that I hope to discuss is an entirely new design.

What I'm planning on building for myself (and also possibly some other people since I keep getting asked if I sell them) is basically a long life, accurate movement, and minimal set up time heliostat.

This one will be based on wormgears, and I am going to try to make it capable of 360 degree motion along both the altitude and azimuth directions. I have attached a few screenshots to show what I am planning.

I wouldn't be surprised if it will end up taking me upwards of six months before this thing is really finished the way I want it to be. There are a lot of little things that I'm going to have to figure out. I am also going to have to invest in some small machine shop tools, so it will take some time for me to save up for them and also to figure out how to operate them.

Of course, the two designs I've mentioned so far certainly aren't the only ones.

There are a few others on this forum have shared.
http://cerebralmeltdown.com/forum/index.php?topic=293.0

http://cerebralmeltdown.com/forum/index.php?topic=321.0

http://www.heliostats.org/



If anybody has any input, I would be glad to hear it!



Paul L

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Re: Heliostat Design(s) [Work in Progress]
« Reply #1 on: October 22, 2012, 06:29:26 PM »
You've probably already seen this - http://stevenbrace.co.uk/2012/06/diy-arduino-motorised-time-lapse-head/
but I was just drooling and thought I'd share...


Paul L

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Re: Heliostat Design(s) [Work in Progress]
« Reply #2 on: October 22, 2012, 08:15:24 PM »
Also, here's a neat article from a 1960 edition of Popular Science detailing a simple wayto make wooden worm gears.  When I get some spare time, I hope to try out this method using a cheap HDPE cutting board from the dollar store instead of  hardwood. 


http://books.google.ca/books?id=VyYDAAAAMBAJ&pg=PA178&lpg=PA178&dq=make+wooden+worm+gear&source=bl&ots=GAU8mJN1yz&sig=hOoTijlG03A5JDqVeKfh0_Wx-WY&hl=en&sa=X&ei=wAqGUM6bLsXxigLfxoDACw&ved=0CCsQ6AEwAg#v=onepage&q=make%20wooden%20worm%20gear&f=false

Gabriel

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Re: Heliostat Design(s) [Work in Progress]
« Reply #3 on: October 23, 2012, 09:00:48 AM »
I actually hadn't seen either of those links before. Very cool!

On a side note, I'm currently trying to put back together the heliostats I made using lead screws as linear actuators, but with some modifications. I really want to hurry up and get something set up outside before the winter.

Paul L

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Re: Heliostat Design(s) [Work in Progress]
« Reply #4 on: October 23, 2012, 08:46:51 PM »
     Yeah, I think wormgears would be great, but they do cost more (and I imaging a little tricky to make) than the lead screws you've used in previous designs.  It's nice to use stuff off the shelf since it makes the design more accessible.  I'm not quite sure how you're going to get the degree of rotation that you want with lead screws...looking forward to seeing your new design.

     I've been brainstorming/daydreaming on how to modify common household items that use gear reductions for a heliostat design.  So far I've come up with a salad spinner, which would be suitable since you could fit all the boards in the spinner itself to protect everything.  The other idea was using an eggbeater, which is nice because the one I have is pretty skookum. 
Ahhhh, brainstorming..... :P       


Gabriel

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Re: Heliostat Design(s) [Work in Progress]
« Reply #5 on: October 24, 2012, 06:40:11 AM »
I'm not quite sure how you're going to get the degree of rotation that you want with lead screws...looking forward to seeing your new design.

I won't actually be able to get any better of a range of motion for the leadscrew based design. At my latitude, and for the target angles I want to use, it isn't as crucial to have a large range of motion, but I still want to see if I can figure out something to increase the azimuth range though.

iamtawon

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Re: Heliostat Design(s) [Work in Progress]
« Reply #6 on: October 29, 2012, 12:45:25 AM »
I personally think that Jim's design is the most simple and straightforward way to do it on a big scale ( 1-2m mirror)
May the sun be with you

Paul L

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Worm Gears Anyone?
« Reply #7 on: November 28, 2012, 04:03:50 PM »
Hey everyone,

     I've had a few disappointing/frustrating days trying to figure out how to throw together a worm gear system with off the shelf parts.  No luck here.  I was thinking that maybe I could use something similar to this for the worm

http://www.reidsupply.com/sku/EZ-21/

How to make the corresponding wheel is the problem for me...

Anyone with any other creative solutions out there?  My current design isn't working - it uses gears for the az, but I'm finding that when the driver board powers down, the stepper slips back down the tooth that it had partially climbed.  *sigh* and it looked so pretty....:( 

Gabriel

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Re: Heliostat Design(s) [Work in Progress]
« Reply #8 on: November 29, 2012, 01:53:41 PM »
Hi everyone,

Here is an assortment of pictures of a linear actuator based heliostat that I put together. I am thoroughly convinced that a linear actuator based machine isn't really the best way to go since they are more complicated and have a rather limited range of motion, but I wanted to have at least one machine around to help with testing the Sun Tracking / Heliostat Program's linear actuator settings. I'm glad I did too because I did find one bug. I will update the fixed version of the program soon (already done), but in the meantime I figure that I can at least show what I have been up to.

Overall, the machine does seem to track well, but it is painfully slow (Nevermind, I tried it out at a higher speed, and it looks like the stepper motors can move the machine at a much higher speed without losing steps), which seems to be typical with the linear actuator based machines.

Here is a picture of the front of the heliostat. I haven't even bothered to clean the mirror yet since this is just a quick test.


Here is the back of the heliostat. I don't know if you can see it very easily, but instead of using door hinges for the alt rotation, I instead used galvanized lag screws as a pivot. I figured that they would hold up a lot better in the weather and are probably cheaper too.


It is a lot easier to align a machine to the correct azimuth direction if you are able to rotate the entire thing to point at the sun in sun tracking mode and then lock it into place to keep it there. Forget about that nonsense I have suggested in the past about using a compass for alignment, this is waaay easier. I have decreed it, all heliostats and sun trackers shall hence forth be designed with this ability built in. :)
It's probably hard to see this in the below picture, but the 2x4 sitting on top of the 4x4 post is screwed down so that it can't move. The 2x4 on top of it is clamped to the pipe, and the pipe is able to turn inside of a hole drilled into the 2x4 on the post. So the entire machine, leadscrews and all, rotates around the azimuth pivot point.


Here is a view from the side. Perhaps you can see the lagscrew better here.


Here is a view looking down on the leadscrews. None of the electronics are really protected from the rain since the machine is just temporarily set up for now.



If you want to get a closer look at how everything has been put together, here is the link to the Sketchup model. It's not exact, but it is close. I believe there are some errors, in particular where the mirror interferes with the 2x4s that are on top of the post.
www.cerebralmeltdown.com/forumpics/LinHelio/LinearActuatorHelioV11.skp


Anyway, enough of that machine and on to bigger and better (well at least better) things. Like I said, worm gear based heliostats are a lot easier to understand. When using linear actuators, there are at least 6 more variables that have to be taken into consideration, and if you make a mistake on any one of them, your machine isn't going to work and you'll inevitable spend hours of your life trying to figure out why.


I don't have a lot to show yet as I've spent most of my effort experimenting with the design in Sketchup. It is still basically a variation of the design of the machine that I posted at the top of this thread. You can download the model at the below link if you want to see what I have so far.
www.cerebralmeltdown.com/forumpics/LinHelio/HeliostatV51.skp


Here is one picture of a mock model. This will never actually be completed as I just wanted to get a rough idea of the scale and the machine's rigidity.


The worm gears actually weren't very difficult to make. I think the method I used might have been similar to the one Jim used for his machine. http://cerebralmeltdown.com/forum/index.php?topic=293.0

For the worm part of the worm gear, I used 7/16-14 threaded rod. For the actual worm gear, I cut a circle out of some scrap plastic with a hole saw and then mounted it in a jig that it was able to rotate on. I then cut a groove around the perimeter of the circle by drilling "holes" with the drill press. Basically, I would drill a "hole", rotate the gear, drill another "hole", etc until I went all the way around. I then put a 7/16-14 tap from a tap and die set on the drill press set on its lowest RPM setting and used it to cut the threads in the worm gear.

It seems to work fine, although I haven't checked it for accuracy.

I don't think that it would be too hard to do it with just a normal power drill if you don't have a drill press, but you would probably have to make some kind of jig to make it work.

I made a worm gear in the past that worked pretty well. It's at this link. http://www.cerebralmeltdown.com/cncstuff/page3/wormgear/default.htm
I will add that cutting the threads with a tap was much easier than the method used there.

That's what I have so far. More to come.

Gabriel
« Last Edit: December 06, 2012, 03:13:02 PM by Gabriel »

Bob101

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Re: Heliostat Design(s) [Work in Progress]
« Reply #9 on: November 29, 2012, 04:03:03 PM »
Hey Gabriel,

It's very impressive how you can make this stuff. I wouldn't even have a clue where to start. It makes interesting reading and things are looking good.

I notice that the wormdrive arrangement you have in your final image is VERY similar to the arrangement in the Oyster unit I am using for my solar tracker. Probably jumping the gun here but are you aware that with a worm drive arrangement the horizontal and vertical movements are not totally independent? Specifically, as you rotate your cog around the worm drive shaft it will rotate altering the vertical pitch.

Like so:
Worm Drive 8: Wheel rotating around worm locus


In the Oyster's case this was pronounced enough to make a significant difference to the angle (and mess up the function of the limit switch). We had to add code to correct for this, it's all in my thread.

Gabriel

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Re: Heliostat Design(s) [Work in Progress]
« Reply #10 on: November 29, 2012, 04:13:20 PM »
Yeah I know I'm going to have to compensate for that at some point. I don't think it will be too hard to do it though.

Interesting that the Oyster is similar in design. I guess there are no new ideas are there. :)

Paul L

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Re: Heliostat Design(s) [Work in Progress]
« Reply #11 on: November 29, 2012, 09:09:29 PM »
Just a quick question - I noticed the threaded rod you're using is quite larger than the 1/4" stuff that I'm using.  Are you still using the method you described here:

http://www.cerebralmeltdown.com/heliostatprojects/Heliostat%20plans%20V2/page5/default.html

or do you have a new method.  I'd like to use thicker rod,just to beef things up, but I'm using helical couplers that have a 6mm openings on either end, so I'm stuck using 1/4" rod for now.  It seems like I may have to invest in a tap and die set, which would be something new for me just so I can take a stab at making a worm gear and trying out your coupler solution.  Also found another diy coupler similar to yours here:

http://buildyourcnc.com/diycoupling.aspx

Paul

Gabriel

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Re: Heliostat Design(s) [Work in Progress]
« Reply #12 on: November 30, 2012, 06:40:49 AM »
Hi Paul,

No I actually just drilled a hole in the end of the leadscrew that was the same diameter of the stepper motor shaft. That's one reason I switched to a larger diameter leadscrew because it would be able to fit the shaft inside. Honestly though, it was really hard to get the hole straight enough and centered even on the drill press. It's time consuming enough that I don't think that I will try to do it again. Maybe if I had a lathe it wouldn't be so bad.

I think the method used at the link you gave would be better.

If you are only cutting plastic, then you can probably get by with the cheapest tap and die set you can find. However, if you think that you'd use it for metal at some point, definitely shop around for something better. My own cheap tap and die set has caused me so much aggravation.

Paul L

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Re: Heliostat Design(s) [Work in Progress]
« Reply #13 on: December 08, 2012, 10:08:57 PM »
I love to see clever uses for everyday objects - these guys use a car jack hack for their altitude adjustments!  It looks like they're also using a gps and compass as Bob is currently doing to orient the tracker.  Cool stuff!  It's funny how people who have absolutely no contact with us are working on something so similar....I wonder how many others there are out there....

http://heliowatcher.com/

kudos to these guys!

Paul
« Last Edit: December 08, 2012, 10:19:36 PM by Paul L »

Gabriel

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Re: Heliostat Design(s) [Work in Progress]
« Reply #14 on: December 09, 2012, 07:18:25 AM »
Yep, it does sound similar. I've also wondered what would be the best way to have a solar tracker seek out the optimum direction to point on cloudy days. I've been thinking about experimenting with webcams pointed at the sky to see if I can somehow determine how much solar radiation my location is receiving at any given time and then logging it for future reference. I wonder if I could also use the same camera to guide the solar panel to point in the best direction during cloudy days. That's certainly not a weekend project though. :)

I'm happy to see that those small stepper motors are able to turn the leadscrew on that car jack. I ordered a couple of those (still waiting for them to arrive), but was uncertain if they would be powerful enough to do much. I also bought a couple of those EasyDriver Boards to try out. I'm planning on finally setting up two electronics systems so that I can leave one running continuously while they other is used for testing.