Anybody ever DIY a cleaning magnet for 3/4" glass?

[AcroSteve]

Rather than pay the $130+ for a Great White or $200 for a Magnavore, I know I can build one for less.

The question is, without some trial and error(which means buying more magnets than I need), how can figure out which magnets to get?

My tank is 3/4" glass.

I think I would go with an overall size of about 3x4. The Magnavore uses two magnets. I think that probably would be the most stable setup, but would it be better than 4 magnets - one on each corner, or better than one large one?


And what strength to get?
I am looking at http://www.magnet4less.com/

With a couple of 2x1x1/2 coated magnets, the combined strength is 140lbs through 1/2" thickness. Think that would be extreme? On the surface, it seems that way to me, but part of me thinks the ratings might be a little optimistic.

[AcroSteve]

I wonder if round magnets would be better. It wold definitely be easier to mount them in whatever I choose to use for the blocks. Just drill a hole with a Forster bit and drop the magnets in.


Any disadvantages to the round ones?

[Mikeeal]

I've only made a couple of really small ones for picos, but I used the round ones. They were about the size of a nickle and worked great. Something to consider though when talking about the thickness is if your glass is 3/4" then the magnets will really be more like an inch apart, or more, from the pads you use and also however thick the magnet housing will be.

Speaking of that, what are you plannin on for the housing?

I think your almost stuck buying several different ones and testing their strength unless there's a magnet expert in the house, or someone that's already done it.

[AcroSteve]

Yea, you are right. They will be about 1" apart when on the glass.

The outer housing will be a block of wood(mahogany) finished to match the tank. The one on the inside will likely be the same thing, but encased in epoxy. I am thinking if I use wood for the inside 1/2, I will end up with enough flotation to keep it off of the sand if they become separated.


I will install felt on the outer 1/2 and just use some fine scotch bright on the inner one.

I am fine with getting a couple of different strength magnets, but I am hoping to get some info to see if I am even in the ball park.

If a magnet is rated at 120lbs, is that doubled when you use two of them, rather than just one with a piece of steel?

[AcroSteve]

Found some info.

http://www.magnetnerd.com/
The rule of thumb is that a NIB is attracted to another NIB with a force 1 1/2 times the attraction to steel.

So, if I use two pairs of 66lb magnets(1-1/2"dia x 1/2"thick), I would have a total of 198lbs(99x2)

The 2"x1/2 ones are 110lbs. So two pairs of them would be 330lbs. Probably way too much, but I am not sure.

[AcroSteve]

Well, I ordered some 1" and some 1-1/2" ones

Hope I don't pinch too many fingers. :eek:

[redfishsc]

What kind of epoxy are you using? I would personally be more likely to encase this in fiberglass resin or polyester resin. Basically the same thing, fiberglass resin is more exterior grade.

If you really want epoxy though, West System 105 with slow hardener would be a good choice. A bit spendy maybe, but the toughest commonly available epoxy I've ever used.

[AcroSteve]

Yes, I will be using a commercial fiberglass epoxy system.

I already have some of the West system products from other projects. Good suggestion.

[BeanAnimal]

When dealing with raw magnets this size, pinched fingers are the least of your worries. You will need to keep the magnets WELL isolated from each other, as their attraction can cuase them to fly together. They will not pinch fingers, they will crush them or remove them. The magnets are brittle, so an uncrontrolled attraction can cuase them to smash togeher and shatter.

You mention (2) magnets in each half. You will need to find a way to fully secure the first magnet before placing the second magnet. As you means of securing is likely permanent, you will need to ensure that you have the poles marked and situated properly.

[AcroSteve]

For prototyping, I figure I will drill some cavities in a block of scrap wood to house the magnets and then screw a fiberglass cover over them. I have some 1/8" thick fiberglass panels that will work for this. This will allow for some flexibility before I finalize the design and pour the epoxy.


The magnetnerd website has some rather graphic examples of damage done by out of control magnets. So I think I have been warned. If I get hurt, it's my own fault. :lol:


So Bean, you think I am even in the ballpark with the ones i have picked for my 1st go around?

[redfishsc]

Man, I gotta get some of these magnets!

<a href=showthread.php?s=&postid=15735288#post15735288 target=_blank>Originally posted</a> by AcroSteve
Yes, I will be using a commercial fiberglass epoxy system.

I already have some of the West system products from other projects. Good suggestion.

Sounds great.

The main reason I ask is b/c the common "bob smith" epoxy (clear and yellow 2-part) that you can get at Lowe's is often labeled "waterproof" but it does not hold up in marine situations very long before it gets soft. There is a grey marine grade out there that seems to be quite tough (it's black and white), I've used it a few times and it's never softened on me yet, might be good for someone making a small magnet.

[nsamouroux]

I've been thinking something along the lines of your project, but using cast acrylic instead of wood / epoxy... There is a Tap Plastics store near me in Seattle that has some sample pieces of clear or colored cell-cast acrylic in thicknesses up to 2"; I was thinking of buying two rectangular sections of this material (say 3" x 5" each and 1.5" thick?) and then a short length of cylinder material sized to match (or slightly larger than) the diameter of the neodymium magnet. My idea was to use a forstner bit to bore a hole for the magnets in each half of the unit, then place the magnets, fill the holes with weld-on (perhaps weld-on 16? Maybe the thinner stuff would be better), and finally insert a cylinder-shaped acrylic "plug" into the hole. This should end up being bonded and effectively permanent and would hold in the magnets while keeping them away from any contact with water. No worries of epoxy / wood / etc breaking down or decaying, and I think it would look VERY nice to have a clear acrylic cleaning tool where you could see the magnets inside. My tank is 5/8" thick acrylic, so I'd probably put two magnets in each half with perhaps a 60lb pull force per magnet as you were intending to use. I was going to pick up the magnets with the 1/4" hole in the center to give more area for the weld-on / acrylic to bond. Think it would work?

[horkn]

Polyester resin is hydrophilic , if a marine use epoxy is used, you will eliminate the issues that polyester resin will cause.

West systems is good, but IMO way overpriced compared to say UScomposites that is widely used by boat builders and in boat repair.

I made my 193g plywood tank out of the US composites stuff.

I am trying to figure a way to get magnets that will hold through my 3/4" plywood with a good 1/8" of epoxy sided tank as well.

I will follow this thread to see what you come up with.

[nsamouroux]

Also, something else just occurrred to me... I can use my table saw to cut a 45* angle into one side of the acrylic block and insert a sheet of acrylic to act as an acrylic scraper, similar to the credit-card type scrapers I use now to clean the really tough coralline and whatnot... This could be a fun project!

[AcroSteve]

Well, sorry we lost a few posts due to the upgrade, but I finished the prototype and made some small changes.

Here is what I have so far.


I decided not to glue the magnets in. I just glued on a wood cover to match the rest of the block. This is about 2x4 and 1-1/2" thick.
I routed a profile to increase the ergonomics.
http://i11.photobucket.com/albums/a159/sbowman01d/Hardware/DSCN0007.jpg

http://i11.photobucket.com/albums/a159/sbowman01d/Hardware/DSCN0005.jpg



I changed my mind on the inside magnet. After nsamouroux or redfishsc mentioned the acrylic block(one of the missing posts), I got to thinking...


Rather than fool around with wood and epoxy, I wanted to go with the acrylic too. Bad thing is, I do not have any that thick. So I made some.
http://i11.photobucket.com/albums/a159/sbowman01d/Hardware/DSCN0008.jpg


After a little trimming, I ended up with a cleaning surface of about 4x6.
http://i11.photobucket.com/albums/a159/sbowman01d/Hardware/DSCN0013.jpg

http://i11.photobucket.com/albums/a159/sbowman01d/Hardware/DSCN0011.jpg

http://i11.photobucket.com/albums/a159/sbowman01d/Hardware/DSCN0012.jpg

I should have cleaned the ink off the magnets, but oh well.

I am going to do this the same as the outer piece. I have some 1/8" black acrylic that I will glue to the large surface of the block. This will fully encapsulate the magnets.

[BeanAnimal]

looks good so far :)

[kcress]

Indeed.

What are you going to use on the two surfaces?

[nsamouroux]

Looks good, I was just going to run a router around the edges of my 1.25" acrylic blocks to round them down, but maybe I'll do something a bit more decorative like you did...

[AcroSteve]

I suppose it does look a little better than just a block, but I wanted to thin down the edges to help reach spots when the coral gets a little close to the glass.

Down side to the acrylic, is a loss of flotation.



I have some thick adhesive backed felt that I am going to stick to the outside. And for the inside, I think I will try some of the hook side of some adhesive backed velcro. That should hold the scotch bright pad secure.

[Mikeeal]

EDIT: Dang Steve beat me to it ^^^

He talked about felt on the outer portion and a fine scotch brite on the inside. I wonder what the roughest type of material is that can be used without actually scratching the tank? All I have now is the large size mag-floats and it seems like a rougher pad inside would be ok. When I think of the finer scotch brite pads, like the white ones, those seem like they'd be too soft?

Very nice work so far Steve, they both look great. So maybe I missed this part, but are you going to weld the magnets into the larger piece still or do you think the outer panel will be enough to hold/seal the magnets in?

[AcroSteve]

Not really digging the thought of polishing this acrylic.

Either leave it this way, or flame polish.

Thoughts?

[AcroSteve]

I was thinking of the white scotch bright too, but maybe the gray.

Looked at Wally word, but could not find any scotch bright at all.

Next time I am by the hardware store, I will check them out.

[redfishsc]

Not really digging the thought of polishing this acrylic.

Either leave it this way, or flame polish.

Thoughts?


Yes. I buff acrylic all the time on acrylic/resin fountain pens. Not as hard as you might think.

First, you'll probably be just as happy as anything by sanding the whole thing up to around 400 grit (or higher if you want) and leaving it. If you sand it with a random orbit sander and some 400/600/800, it will have more of a matte finish to it, but when you put it in the water, it will "clear up" a bit. Not a lot, but it will look fine IME.

If it's going to sit inside the tank, it's gonna get algae covered anyhow and wouldn't be worth the trouble. That's what I'd do.

You can use a couple dots of superglue and glue cheap hand paper to a used random orbit pad rather than buying expensive high-grit pads.



For the higher gloss look, I sand my pens up to 800 or 1,000 grit wet/dry sandpaper (I sand dry) and then follow with two buffing wheels (1,200 RPM on 8" wheels)--- first is Tripoli compound and the second is White Diamond compound. This should give you a pretty nutty glossy finish.


Or, alternatively, you can try the heat method. Maybe even putting it in a hot oven for a brief period? I don't know what the melting temp of acrylic is.

[nsamouroux]

I was just going to flame polish my edges. I'll be using Mr. Clean brand Magic Eraser pads on my acrylic tank, it's the best thing by far I've found for cleaning even coralline algae off the panels without scratching them.

[kcress]

I'm stuck with an acrylic tank at this time. Magic Eraser pads? Tell me more.. You use them on both sides?


Steve; Did you set up the magnets so their poles are opposite in each block?

[nsamouroux]

Magic eraser on the inside, just a thin layer cut off the main block (there's a few threads on RC about these, work extremely well for acrylic!). On the outside, I normally use either soft felt, microfiber, or some sort of acrylic cleaning wipe from the Novus kit (or other acrylic cleaning kits).

[AcroSteve]

Steve; Did you set up the magnets so their poles are opposite in each block?

Yes.

[AcroSteve]

Well, I have a little problem that I NEVER expected.

I used Weldon 16 to glue the acrylic because I had plenty of it on hand. When I glued the "cover" on the block containing the magnets, the excess must have squeezed into the center of the magnet with the hole in it. Now the excess weldon is eating away at the acrylic.

There are two soft spots in the acrylic where the holes are - underneath.

I am hoping these firm up over time. Sure am glad i had not put the velcro on yes, as I might not have noticed and water could have gotten in to the magnets.

http://i11.photobucket.com/albums/a159/sbowman01d/Hardware/DSCN0001.jpg

One is worse than the other, but it is doing this above both magnets.
http://i11.photobucket.com/albums/a159/sbowman01d/Hardware/DSCN0002-1.jpg

[nsamouroux]

Huh, interesting... I used a forstner bit to drill my blocks and pressed the magnet into them, then put a layer of the weld-on 16 around the edges and then inserted a plug that I cut from a cast acrylic rod with a diameter matching the drilled hole... It came out fine and works perfectly on my tank (holds well up to a 3/4" acrylic tank, as you said it's likely not strong enough to really scrub the heck out of a glass panel that thick). After seeing your update I'll keep an eye on it though...

I haven't taken the router to mine yet (will flame polish after using the router) but here's the workable first draft :)

http://i99.photobucket.com/albums/l285/nsamouroux/Equipment/PICT0605.jpg

http://i99.photobucket.com/albums/l285/nsamouroux/Equipment/PICT0606.jpg

Chair back is 3/4" and curved, so the equivalent of a 1" panel by my guesstimation:
http://i99.photobucket.com/albums/l285/nsamouroux/Equipment/PICT0604.jpg

http://i99.photobucket.com/albums/l285/nsamouroux/Equipment/PICT0608.jpg

http://i99.photobucket.com/albums/l285/nsamouroux/Equipment/PICT0609.jpg

[nsamouroux]

I just went over my blocks to look for soft spots and didn't find any warping / deflection / degradation of the thin plugs I made to cap and seal the magnets... Out of curiorisy, did you use cast acrylic for yours? I noticed in one of your posts you were using thinner material layered into a larger block, but did you use extruded acrylic or something for the faceplate? The cast acrylic disc plugs I made were about 3/16" thick and I put a good amount of weld-on 16 under them and they show no sign of softening. I can't think of why yours would be doing that unless there's a massive puddle of it under there :)