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Unread 01/19/2013, 06:02 PM   #51
Crit21
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Search ebay or amazon for 1 rpm pellet motor. They're as cheap as $60 with a 1 year warranty.

If you want a 2.5-3 RPM motor you can get a microwave turntable motor for under $20. They're very compact, but I don't know how durable. I imagine they're fine for turning a pipe with not a lot of friction. At that price they're replaceable every 6 months and are still cost effective.



Last edited by Crit21; 01/19/2013 at 06:28 PM.
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Unread 01/19/2013, 10:33 PM   #52
karimwassef
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The microwave motors are 21V AC? The pellet motors look great though.


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Unread 01/19/2013, 11:46 PM   #53
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Given the forces on the rotating internal tube from pressure and water flow, can you eliminate the seals entirely by coupling the rotating tube to a disc on the motor through a PVC end cap wall using coated/sealed rare earth magnets?


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Unread 01/20/2013, 08:13 AM   #54
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I fear that the seals on your rotating shaft are going to live a rather short life and their failure at that diameter poses the potential for some serious flooding very quickly.

5 out of 6 of those repair couplings never seal to begin with, they are garbage. I am somewhat amazed that the one you are using is not leaking already!

Canoe... the mag drive option will work, but choosing the proper magnets is tough. They need to be strong enough to prevent the drum from skipping but weak enough to prevent significant friction. Sealing them has proved to be very hard and even the machined drums from Oceans Motions tend to wear through after a year or two and need replaced.


The Oceans Motions device is fully evolved and has used both the sealed shaft and mag drive variants. They devices are not cheap, but they are reliable and backed by the absolute best customer service anybody could ever ask for.


Even though the mechanics are simple, these types of flow diverters are tough to make reliable.

A 4 or 6 way hayward or jandy pool valve and actuator can be had on eBay for $150 or so and be much more reliable.

Not knocking the DIY effort, but simply pointing out the very real potential for disaster based on the physics at work....


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Unread 01/20/2013, 08:40 AM   #55
Canoe
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Quote:
Originally Posted by BeanAnimal View Post
... Canoe... the mag drive option will work, but choosing the proper magnets is tough. They need to be strong enough to prevent the drum from skipping but weak enough to prevent significant friction. Sealing them has proved to be very hard and even the machined drums from Oceans Motions tend to wear through after a year or two and need replaced...
Thank you! Missed that: magnet attraction causing friction.

Well, the solution will also minimize the wearing out of the internal drum.
  • First Step: internal drum should be out of a harder material than PVC, like ABS.
  • 2nd Step: internal bushings for the drum to slide on, made out of a dis-similar plastic, like HDPE. Can be a loose fit, provided the bushing is prevented by some means from moving into the area of the openings for water flow.
  • 3rd Step: sealed/coated magnets are placed on the internal drum, but evenly spaced around it's circumference.
  • 4th Step: magnetically coupled drive is achieved by a larger diameter outer tube, that has coupling magnets spaced around it to match the spacing of those on the internal drum. Motor drives the outer drum.

Unit is entirely sealed.
Threaded plugs at appropriate places for maintenance.
Harder plastic internal drum against HDPE will have less friction, while wearing less.
Forces from magnets are balanced around the diameter, minimizing "induced" (can't think of the right word) friction.


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Unread 01/20/2013, 09:40 AM   #56
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Bean. This is my second DIY using the 1" extender. The last one used the same motor but was a lot more complicated. It lasted 3 years without failure and I took it down for maintenance once a year. I still have it and will will clean it up and take it apart to take pictures. Service life was 2004 to 2006.

I only have these 2 data points so far but statistically, you may be right.


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Unread 01/20/2013, 09:58 AM   #57
karimwassef
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Here's my first DIY
Photobucket Pictures, Images and Photos
Photobucket Pictures, Images and Photos
Photobucket Pictures, Images and Photos

Here are the o rings from different angles

Photobucket Pictures, Images and Photos

Photobucket Pictures, Images and Photos
Photobucket Pictures, Images and Photos

I found some wear and tear, so here are the close ups:

Photobucket Pictures, Images and Photos

Photobucket Pictures, Images and Photos

Here is the internal shaft for completeness

Photobucket Pictures, Images and Photos


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Unread 01/20/2013, 10:02 AM   #58
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I wanted to see what a brand new seal looks like for comparison. I took a new extender apart. I took the pictures from a different angle so I wouldn't confuse them.

Photobucket Pictures, Images and Photos

Photobucket Pictures, Images and Photos


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Unread 01/20/2013, 10:02 AM   #59
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Canoe, I think your idea would work. The use of different types of plastic discs (Teflon, etc...) and hard magnets would make the design much more compact but may put it out if the competency range of many DIYs and add cost. If you'd like to give it a go and post here, that would be ok... Just help less skilled people like me follow along with your sources of materials, etc...

Bean, the very very slow rotation of the seal may be a contributing factor to its longevity.



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Unread 01/20/2013, 10:35 AM   #60
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Quote:
Originally Posted by Canoe View Post
Thank you! Missed that: magnet attraction causing friction.


Well, the solution will also minimize the wearing out of the internal drum.
  • First Step: internal drum should be out of a harder material than PVC, like ABS.
  • 2nd Step: internal bushings for the drum to slide on, made out of a dis-similar plastic, like HDPE. Can be a loose fit, provided the bushing is prevented by some means from moving into the area of the openings for water flow.
  • 3rd Step: sealed/coated magnets are placed on the internal drum, but evenly spaced around it's circumference.
  • 4th Step: magnetically coupled drive is achieved by a larger diameter outer tube, that has coupling magnets spaced around it to match the spacing of those on the internal drum. Motor drives the outer drum.
Unit is entirely sealed.
Threaded plugs at appropriate places for maintenance.
Harder plastic internal drum against HDPE will have less friction, while wearing less.
Forces from magnets are balanced around the diameter, minimizing "induced" (can't think of the right word) friction.
You may not be familiar with the Oceans Motions devices, but as I said, this has already been done. Paul (the owner) is a master machinest and inventor. He went through numerous (likely countless) itterations of the mag drive. Even he was somewhat shocked at how complicated it was to get things in proper balance with regard to friction, coupling force, durability, etc.



That is, the simple concepts you described above are not so simple in implementation. The physics here are not kind or forgiving. I am not saying it can't be done as it already has been... I am saying a reliable and durable mag drive is not nearly as easy as it sounds, even if you have the proper tooling and skill set


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Unread 01/20/2013, 11:32 AM   #61
Canoe
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Quote:
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You may not be familiar with the Oceans Motions devices...

That is, the simple concepts you described above are not so simple in implementation...
Only somewhat familiar with the OM. Not on the details.

But I've been messing with using such magnets as DIY bearings and thrust bearings for DIY vertical axis wind turbines, so a magnetic coupler seems easier. I wouldn't want to be trying it for the moment angles and sizes of the OM stuff, but for a narrower tube like used here, and for what appears to be the original inspiration that I found on the internet some years ago, it doesn't seem like it could be that hard. But, that's exactly what you're saying. I can lay it all out reliably in my head, but then I add the force from the water flow and all the questions open up again. Have to build it to know.

Well, this was on the list to do a few years ago. I'll have to see if I have the basic parts handy to work with. I've certainly got the magnets.


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Unread 01/20/2013, 11:45 AM   #62
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If I'm going to do this, what would be the most useful flow-through diameter for the most people?


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Unread 01/20/2013, 12:39 PM   #63
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I don't know who would have that statistic but I would say 1" would've general use. I selfishly would like to see a 2" implementation since I'm working on a 560 gal (380+180 sump). Also, I find that larger pipes make the machining and assembly of a DIY easier.

I already have this working. I do need help on a simple actuated valve (leaky ok). This may even be more amenable to a magnetic approach with a DC solenoid and a hard magnet inside!


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Unread 01/20/2013, 07:03 PM   #64
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For the magnet drive, i assume you are thinking of a disc inside and a disc outside like a VorTech, but as pointed out that leads to loads compressing the two things together...

But, there is another option here, you can make a cup and rotor setup instead. That way the loads magnetic loads can pull in every direction, essentially centering the shaft inside the tube... Sure if they are strong enough even that will wear into the sides, but pipes are pretty good at not expanding (hence their pressure ratings). Also, using what is already available (water pressure) as a bearing is not a bad idea either.


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Unread 01/21/2013, 12:52 AM   #65
Canoe
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...you can make a cup and rotor setup instead. That way the loads magnetic loads can pull in every direction, essentially centering the shaft inside the tube... Sure if they are strong enough even that will wear into the sides, ...
Yup!
cup/drum
Quote:
Originally Posted by Canoe View Post
  • 3rd Step: sealed/coated magnets are placed on the internal drum, but evenly spaced around it's circumference.
  • 4th Step: magnetically coupled drive is achieved by a larger diameter outer tube, that has coupling magnets spaced around it to match the spacing of those on the internal drum. Motor drives the outer drum.
In practice, from my magnet bearing work, if loose, it will end up pulling to one magnet over the others. If held centered by a bushing, the loads will be nearly equal.


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Unread 01/21/2013, 09:25 AM   #66
Crit21
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The microwave motors are 21V AC? The pellet motors look great though.
Not all of them. Here's a 115V model. http://www.amazon.com/Sharp-Microwav...icrowave+motor

With the auger motors you still have to ask the seller if they're made for a restricted duty period. I found one that's listed at 5 minutes max.


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Unread 01/21/2013, 09:31 AM   #67
Crit21
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Quote:
Originally Posted by Canoe View Post
Given the forces on the rotating internal tube from pressure and water flow, can you eliminate the seals entirely by coupling the rotating tube to a disc on the motor through a PVC end cap wall using coated/sealed rare earth magnets?
That's what I managed to overcome by using a PVC tube in side a PVC tube instead of the PVC extension. I have extremely low friction and almost nonexistent leakage under pressure. I drilled a hole in a 4" end cap to use as a splash shield just in case. It took some drilling with a hole saw and sanding with a sanding drum on a drill to get the fit just right so the pipe would rotate easily.


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Unread 01/21/2013, 09:42 AM   #68
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This shows the low friction in my prototype. You may need to hit Replay once or twice before it plays smoothly.





Last edited by Crit21; 01/21/2013 at 10:27 AM.
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Unread 04/21/2018, 01:48 PM   #69
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Is this still in service? I'd like to make something similar

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