Author Topic: DIY Worm Gear Based Heliostat Design  (Read 12652 times)

Gabriel

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DIY Worm Gear Based Heliostat Design
« on: June 25, 2013, 09:28:00 AM »
Hey everybody,

As I've mentioned before, it is one of my goals to put together a worm gear based heliostat design that can be assembled with basic off the shelf components found at your typical hardware store. Aside from the stepper motors, limit switches, and Stepper Power Control Board (not strictly required), I was able to get everything needed to build this machine at my local Lowe's store.


Those who follow this forum closely will notice that this is a variation of Jim's heliostat design. http://cerebralmeltdown.com/forum/index.php?topic=293.0

Experience has showed me that worm gear based machines are much easier to set up than the linear actuator based machines I have put together in the past. It probably only took me 15 minutes to mount and align this one, and that includes the time it took to get all of the various tools and things together.

I actually cheated a bit on this one and ended up cutting out all of the various parts on my CNC Machine. Once I work through a few bugs I plan on trying to make a PDF file that you can print out and use as a template for cutting everything out. That way it can be built using more basic tools.

These pictures are just a teaser for now. I'm going to try and build another one and make some modifications / improvments as I go. If you want to have a closer look at how everything goes together, you can check out the Sketchup model. http://www.cerebralmeltdown.com/forumpics/worm%20gear%20heliostat/PVC%20Heliostat.skp
The model is very close to the real life version since the gcode was using it.

I hope to put a bigger mirror on it later. You'll also notice that the PCV Pipe end caps for protecting the motors from the rain haven't been put on it yet. Once I'm sure I won't need to take it apart again, I will seal everything up with silicone. Although you can't see it from the pictures, I have a Stepper Power Control Board mounted inside the machine. Hopefully I will be able to seal everything up well enough to protect it from moisture.



















Materials List
Here is a quick materials list and price breakdown. It's not complete yet, but you will at least get a fairly accurate idea of what is needed.

Gatehouse Arborley 4-in x 4-in x 72-in White Vinyl Fence Post: $15.97
http://www.lowes.com/pd_24992-73428-73002277_0__?Ntt=24992&UserSearch=24992&productId=3159989&rpp=32

EverTrue 0.75-in x 5.5-in x 8-ft Interior/Exterior Paint Grade PVC: $20.56
http://www.lowes.com/pd_209621-1487-07311_0__?productId=3339718&Ntt=209621&pl=1&currentURL=%3FNtt%3D209621&facetInfo=

2-Count 1/4-in- 20 Zinc-Plated Standard (SAE) Regular Nut: $2.73
http://www.lowes.com/pd_142056-37672-881650_0__?Ntt=142056&UserSearch=142056&productId=3013468&rpp=32

1/4" x 3/8" Bronze Standard (Sae) Flat Washer: $2.92
http://www.lowes.com/pd_215870-37672-882991_0__?Ntt=215870&UserSearch=215870&productId=3024780&rpp=32

Mueller Proline 3/8-in Black Steel Nipple Fitting: $4.60
http://www.lowes.com/pd_28021-29760-20316_0__?Ntt=28021&UserSearch=28021&productId=3460386&rpp=32

PVC Endcaps: I don't have the receipt, but I think this would come up to about $6.00 each.

Limit switches (about $4.00)

Stepper Motors, about $30

The total comes up to about $100 dollars in materials for this heliostat, however, notice that the vinyl fence post and piece of exterior trim are long enough to build multiple heliostats. Compensating for that, it comes to about $70.00 for this heliostat. Most of these items I'm sure can be found for cheaper online, so you might even be able to get the price below $50.00. Like I said though, this is just a rough estimate.


Gabriel

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Re: DIY Worm Gear Based Heliostat Design
« Reply #1 on: June 27, 2013, 05:46:51 PM »
Hey everybody,

Just a quick update on this machine. I had it up and running for a day, and the tracking seemed to be fine except for the fact that the PVC plastic I used for the worm gears was too soft. The weight of the mirror was enough to cause it to "fall" some in the altitude direction. I sort of expected this though. I think remaking the gears out of  much tougher Delrin plastic would probably be the best bet, but I still want to see if I can find something that can be bought at your typical hardware store.

I might try and move the location of the limit switches just so that the wires to them don't interfere with the gearing.

I'm also looking into some cheaper stepper motors which should knock about $17 off of the cost of the heliostat. We'll see how they do though.


Paul L

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Re: DIY Worm Gear Based Heliostat Design
« Reply #2 on: June 27, 2013, 07:47:16 PM »
I have to admit that after seeing this post, I feel like a parent who suddenly realizes their child, who I once thought was amazing, is really ugly and stupid - your heliostat looks like it was designed by Apple, and mine is so....broken-assed wooden!!!  Great job, looks amazing, nice and compact.  Hopefully you can find a stronger substitute worm gear off the shelf, and I can try to copy it!  I'm looking forward to more documentation on this one!  Not related at all, I came across a heliostat kickstarter project today looking for 200000.00 British Lbs in funding, so $100 a machine doesn't seem so bad after all   - http://www.kickstarter.com/projects/divatommei/sunnybot-send-sunshine-wherever-you-want

dave-in-NJ

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Re: DIY Worm Gear Based Heliostat Design
« Reply #3 on: June 28, 2013, 04:35:13 AM »
The telescope folks have been cutting their own worm gears for a long time.  one of the ideas that I thought was interesting is to take your wooden wheel, cut in a channel, then mix and fill it with epoxy.
then using cooking oil spray, once the epoxy is setting up, coat your worm and run it into the epoxy. it should deform and push in the threads.   the challenge is to not allow your worm to adhere to the epoxy.

also, since you do not need a full revolution, you can be off on your diameter a bit.

dave-in-NJ

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Re: DIY Worm Gear Based Heliostat Design
« Reply #4 on: June 28, 2013, 04:39:11 AM »
a comment about your worm gear.  if your weight is balanced, the pressure on the worm will be much less.
my idea is to mount the main axis and hang a mirror on each side with the drive in the center.   I have seen many single mirror units, but for some reason, the elephant ear approach appeals to me.


Gabriel

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Re: DIY Worm Gear Based Heliostat Design
« Reply #5 on: June 29, 2013, 06:47:29 AM »
Ha ha Paul. Maybe an Apple computer from the 80s. :)
Someone actually sent me that Kickstarter link earlier. I'm not sure if it was anybody affiliated with the project, but the timing of it coincided closely. They have since changed the page a lot from when I first read it. Some of the claims they made earlier made it sound like the person who wrote the Kickstarter didn't quite understand the realistic capabilities of the machine. In one place it was mentioned that you could use it to heat your swimming pool, which is technically true but the mirror is so small that you would never really make a dent in the temperature.

@Dave
In this case it's really just the soft plastic that's causing the issue. The stuff is so soft that I can push a nail a quarter inch into it without much trouble at all. I found a couple of pieces of round, solid-ish PVC pipe in the plumbing section that I'm going to try and replace them with.
I tend to prefer the "elephant ear" approach myself too. Mostly I just think it looks cooler.

Brendan

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Re: DIY Worm Gear Based Heliostat Design
« Reply #6 on: June 29, 2013, 08:04:37 AM »
Looks great!  Congratulations!

My two cents: don't waste time -- use delrin for gears.  I spent a lot of time trying to make things purely from hardware store parts with the idea that they would be easier for others to replicate.  But now I think the best way to advance the cause is to improve the design, assembly, materials, etc to get something that works well.  The community of people building these is still small and we can help each other source materials.  If the designs improve enough for many people to want to build them (thinking of the 3D printing community as an example), then people will sell kits in which case slightly odd parts are not a big deal.

My MendelMax kit has delrin parts, fancy lead screws, fancy sliding rails -- lots of exotic parts you can't buy at a hardware store but there are hundreds or maybe thousands of people building them because you can buy kits.  It's not an exact comparison because heliostats will take off (maybe) only when they are fairly easy and CHEAP enough to be compelling.  So the parts can't be so exotic that they are expensive. 

Anyway, keep up the fantastic work!

Brendan

(PS: off topic, I'm tempted by the new Beaglebone.  Cheaper than an arudino + ethernet shield, this would ultimately enable an network-connected system.  Imagine internet software updates, iphone apps to set targets (eliminate on-board joysticks), ethernet or X-10 light switches to "turn on lights" (repoint heliostats) in rooms, and so on.  http://www.adafruit.com/products/1278)

dlaing

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Re: DIY Worm Gear Based Heliostat Design
« Reply #7 on: June 30, 2013, 08:42:14 AM »
How are you dealing with the axial load on the worm gear? Are you relying on the stepper motors bearings to take this?

Gabriel

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Re: DIY Worm Gear Based Heliostat Design
« Reply #8 on: June 30, 2013, 08:58:02 AM »
@Brendan: In the end I probably will end up just getting the Delrin. Although it's annoying that I was able to find most everything locally except for this one thing.  Of course, most people would have to order the stepper motors online anyway, so there isn't really such a thing as a 100% "hardware store heliostat". :)

I will probably finish off this one heliostat, and then maybe build one more and document it along the way. After that I'm not going to concern myself about using tools and materials that are found in your typical home. At that point I'm going to focus more on getting something put together that will withstand the test of time with very little maintenance.

@dlaing: Yeah for now. That's actually something that I would like to change because I'm not sure I trust them to hold up if a large force was applied to the end of the mirror. I don't think it would be as big of a deal if the mirror was counterbalanced, but if someone were to just lean against it it seems like it would mess up the stepper motor. I just need to add a second set of bronze bearing.


Gabriel

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Re: DIY Worm Gear Based Heliostat Design
« Reply #9 on: July 17, 2013, 09:30:54 AM »
Just a quick update to show what I've been up to. I actually haven't been able to do a lot since I've been waiting for some tools and parts to come in the mail.

The biggest item is the Taig Lathe I got off of EBay. I have had one of these on my list of things to buy for a long time now. I just kept running into situations where having even a small metal lathe would be really useful (i.e. this heliostat build). I'm still waiting for some various cutting tools and things to arrive in the mail, but I have at least been able to experiment with making a few parts.


One weakness with this heliostat is that the threaded rods are just too small to "bite" into the plastic. I think this was actually my main problem earlier when the machine "fell" in the altitude direction.


I'm going to replace it with a threaded rod with a larger diameter. I'm still waiting to receive a set of metric bits so that I can bore the necessary 5mm hole for the stepper motor shaft, but this is what I have so far.


Finally, here is a random picture of my CNC machine. This is what I have been using to cut out the parts for this heliostat. It probably took me upwards of 100 hours to design and build it. There are still a few parts that I need to remake too. I've never actually had so much fun building something. It actually went together really well, and I only made maybe two dumb mistakes during the whole process. Finally! I have a CNC that cuts circles that actually look like circles!

BobMirror

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Re: DIY Worm Gear Based Heliostat Design
« Reply #10 on: July 21, 2013, 11:24:44 AM »
I have been working on a simple hardware store solar tracking system using EMT pipe and a worm gear. Using a ground pipe with a worm gear attached to it , then a torque tube pipe with a opening for the worm screw drive to attach to, so you get 360-degreese of rotation.  I can send / post the sketchup files if anyone is interested.


Gabriel

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Re: DIY Worm Gear Based Heliostat Design
« Reply #11 on: July 22, 2013, 06:02:51 PM »
Hello Bob, and welcome to the forums!

Sure, you can send along the Sketchup Model if you want. The more ideas the better!

Gabriel

Paul L

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Re: DIY Worm Gear Based Heliostat Design
« Reply #12 on: February 06, 2014, 06:22:18 PM »
Hi All!

   I may have found a good source for worm gearboxes and thought I'd share - I recently learned that they're used in electric wheelchairs.  I contacted a local store (luckily for me, there is a huge number of seniors in Victoria, BC, and hence quite a number of mobility stores!) to see if they kept broken motor/gearboxes, and if they were willing to give me a couple for a solar tracker I was building.  The good folks at Medichair in Victoria generously donated two to the cause.  They told me that it's rarely the gearboxes that are at fault in the gearbox/motor combinations that are taken out of "broken" electric wheelchairs.  The person I contacted my brought me to the back room where they had a few ten foot long shelves filled will "broken" gearbox/motor combos.  He said that it wouldn't be a problem if I wanted more, since he'd rather see them used instead of thrown away.
Anyway, I now have two of them (pics below) - for free!!  I can't find a data sheet for them yet, but the gearing ratio is roughly 20.625:1, and the power shaft is slotted, so it should be fairly easy to attach the stepper shaft.  Now I just need some free time to build another machine....:(  Hope this helps others searching for a cheap source for worm gearboxes! 

Cheers,

Paul       
« Last Edit: February 06, 2014, 06:31:49 PM by Paul L »

Gabriel

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Re: DIY Worm Gear Based Heliostat Design
« Reply #13 on: February 08, 2014, 08:46:35 PM »
Hey Paul,
That looks like a really good find. It seems like people should be able to find these on EBay even if they can't get it local, assuming people bother to sell the broken ones.

If anyone is curious, I have actually given up on this heliostat. These DIY worm gears have just been too headache inducing. I'm working on something more robust now. It's really not very DIYable since I'm using tools that most people don't have to build it, but at least I'll finally have something that can be set up permanently.

You can actually buy just worm gears and worms from this site. https://sdp-si.com/eStore/CoverPg/Gears.htm
If you look at the nylon ones, you'll see that they are reasonably priced. Shipping and handling however, is painful, at least to my location.

cheese

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Re: DIY Worm Gear Based Heliostat Design
« Reply #14 on: October 28, 2014, 05:19:00 AM »
All hi, an inexpensive thingummy for your hand-made articles
http://www.ebay.com/itm/231370333338?ssPageName=STRK%3AMEBIDX%3AIT&fromMakeTrack=true