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Yada Testing

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Mon Jun 16, 2008 6:48 pm PostPost subject:
Yadaraf
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DAY 27 (god, where has the time gone)

Time to start getting caught up on documenting the testing (in this thread). Let's begin by making an important comment about the instrumentation layout -- why it won't work. Twisted Evil

One reflective sensor at the recommended sensing distance of 4 mm didn't appear to produce a significant drag on the stator, but when in pairs, two sensors most definitley interact with the 834DIA. I will have to relocate the sensors to below the bearing (i.e. a new "hole" in the base), where there is virtually zero interaction -- and use a disc encoder. Darn it! Well ... I wanted to do this eventually

Note that the reflective sensors are Fairchild QRB1133, which have metal elements in the IR LED and phototransistor -- not to mention the PCB pins.

EDIT: For Whipmag II, which has radially adjustable stators, I'll probably have to use a smaller sensor -- the QRD1113.




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Yada ...
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Mon Jun 16, 2008 7:38 pm PostPost subject:
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For now try repositioning them 120 apart and 120 from the rotor. This way you are not doubling up the flux interactions but only dealing with one major interaction at a time and two quazi-cancelling interactions. For ease of mount I would suggest double back tape (the type for carpet, not the foam type), a flat head screw with the head stuck to the tape as a post for the sensor. That way you can get to some data without all the re-machining. Wink

Edit: This arrangement would also give you a relatively easy way to measure precession and nutation of the stator. By taking the measurements at the top of the post and then at the bottom, the difference in signal width for a given RPM will be proportional to the amount of radial bearing wobble. By charting the rise and fall times against time for both measurements and aligning the min/max signal widths (you will be using the edge detection) you will be able to map the angular differential. Smile

New thought: You could even mount one high and one low thus getting both terms in real time.

Note: You'll need a marker pulse to indicate zero.


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Mon Jun 16, 2008 8:24 pm PostPost subject:
Yadaraf
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Quote:
For now try repositioning them 120 apart and 120 from the rotor. This way you are not doubling up the flux interactions but only dealing with one major interaction at a time and two quazi-cancelling interactions. For ease of mount I would suggest double back tape (the type for carpet, not the foam type), a flat head screw with the head stuck to the tape as a post for the sensor. That way you can get to some data without all the re-machining. Wink


I set them at 180 degrees so that they wouldn't get in the way of finger-flipping the AGW stator. Also, the stators are raised approximately 1/4" from the base, which you can't tell from the pic. The current sensors should work while I develop the firmware and UI. Note that you saw these last Friday, and they worked reasonably well then. I'll video the interaction so that you can see what I'm talking about. It's not noticeable when the rotor is in place -- only when the rotor is removed -- but I know it's still there. Shocked

I'd compare it to Al's small screwdriver effect, which I now appreciate. E.G. Remove the rotor and place a small screw driver or 1/16" drill bit or even a large sewing needle on the base next to a stator -- about 3/4 " away. Observe the interaction with the stator. With the rotor installed, the interaction is very much subdued if at all observable. This is where I am with the current sensor.

I like the smaller sensors, which also have a smaller sensing area (much less than a 0.200" spot). The sensing range on the small sensor is 1.27 mm, which is close to the thickness of the small washer beneath the stator, and that means that the sensor can be flush-mounted to top of the base.


.. Small Sensor ($1.16 from Mouser): http://www.fairchildsemi.com/ds/QR/QRD1114.pdf


Quote:
Edit: This arrangement would also give you a relatively easy way to measure precession and nutation of the stator. By taking the measurements at the top of the post and then at the bottom, the difference in signal width for a given RPM will be proportional to the amount of radial bearing wobble. By charting the rise and fall times against time for both measurements and aligning the min/max signal widths (you will be using the edge detection) you will be able to map the angular differential. Smile


Twisted Evil I like the idea of using the rise/fall times to measure the precession. Cool This might actually work out better for sensors that target a disc on the underside of the stator bearing -- something on the order of a time-of-flight measurement along the periphery of the disc. Good idea. Wink The smaller sensor is sounding imminent ...

Cheers Smile
Yada ...
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Wed Jun 18, 2008 6:38 am PostPost subject:
Yadaraf
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DAY 28

Fish Test

I bought an 8 lbs, pocket fish scale at Sports Authority for $2.97 in an attempt to measure the pull force of two different magnets: surplus ZD49 N35 and Bob's Nxx. Bob's have already been repel tested and appear to be weaker than N42.

For the fish test I used a hammer as the attractive material, although it was hard to find a really smooth surface and I would have preferred to use polished steel. Both Bob's magnet and the surplus magnet measured a nearly identical pull of 0.95 kg (2.1 lbs) (5 samples each). The only N42 magnets I have are the R834DIA, and I tested these as well -- to demonstrate the range of the fish scale.

Pull force: K&J BLACK, Yada RED

ZD49, N35, 1/4" x 9/16": 2.4 lbs (2.1 lbs) -- Note 0

Bob's, Nxx, 1/4" x 1/2": ?.? lbs (2.1 lbs) -- Note 0

D48, N42, 1/4" x 1/2": 3.99 lbs (N/A -- don't have, and presented for N42 reference only)

R834DIA, N42, (1/4" x 3/16" x 1/2"): 4.73 lbs (3.3 lbs) -- Note 2


Note 0. Bob's and the surplus magnet have nearly identical pull force, but the surplus magnets are 12% longer than Bob's, which begs the question: Does an N35 magnet that is 12% longer than an N38 magnet (Bob's?) have similar same pull force?

Note 1. On the fish scale is a zero adjustment, which I tweaked.

Note 2. The hammer surface is rather rough, and polished steel would probably produce better results.

Note 3. The kg scale is easier to read than the lb scale.

Note 4. If anyone can fish test a D48, that would be nice. Cool

Note 5. Packing tape wraps the circumference of the magnet and also a small washer, which keeps the tape from tearing during the test. The tape is doubled over the washer for additional strength.

EDIT:Note 6. I believe the test can be improved by using two steel plates instead of one. As well, the test will be easier to perform, because the scale scan be epoxied to the second steel plate and, thus, no packing tape or washers or assembly will be required. This is also how K&J performs the test. .. off to find some thick, smooth steel plates -- perhaps I can cut a large angle bracket in half. I doubt that these small magnets would saturate a 1/8" thick piece of steel. Cool



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Wed Jun 18, 2008 6:32 pm PostPost subject:
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@Yada,

The R834DIA tests will be apples to oranges. If you test using a single pole, you will have a much smaller contact area. If you test one of the flat sides, you will have an increased contact area and will be shorting the poles. Neither of these approaches will provide anything similar to the cylinder results.

Just my 2 cents,
OC
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Wed Jun 18, 2008 6:45 pm PostPost subject:
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I agree with OC, you will have to place it in a 1/2 arc contact point with 180 of contact area to be accurate for that magnet. Sad

However, if you were looking for comparisons with other replicators you could use two R834dia's and split the reading. Anchor one and attach the other to your fish scale. Wink As long as the same test was performed by each replicator and the scales were accurate enough to each other the comparisons would be valid.
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Wed Jun 18, 2008 7:06 pm PostPost subject:
Yadaraf
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overconfident wrote:
@Yada,

The R834DIA tests will be apples to oranges. If you test using a single pole, you will have a much smaller contact area. If you test one of the flat sides, you will have an increased contact area and will be shorting the poles. Neither of these approaches will provide anything similar to the cylinder results.

Just my 2 cents,
OC

OC, Harvey,

IMHO ... not apples to oranges at all. Wink

K&J performs pull tests on all of their magnets -- cylinders, rods, bars, etc. One difference, however, is that they use two plates, where I used only one. Hopefully this evening I will repeat the above test using two plates.

I understand the physical difference between the R834DIA and the D48 (cylinder vs rod), but this difference won't affect my approach to establishing a simple and generalized pull test with something like a fish scale. I'm simply trying to verify that I can obtain similar pull test values as K&J, regardless of the magnet under test (MUT ?). Essentially I'm trying to establish a general test procedure at this point.

If my fish test produces data close to K&J specifications, then that's a very good start. What I need to do next is apply some known weights to my fish scale to determine its accuracy. This should be easy, since hand weights (small dumbells) vary from 1 lbs, 2 lbs, .. 8 lbs. I just wish I'd thought about this last night when I bought the fish scale.

..Q: Does that make any more sense?

Cheers Smile
Yada ...
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Wed Jun 18, 2008 7:27 pm PostPost subject:
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@Yada,

OK. Makes more sense now that I see that you are simply trying to establish a relationship with K&J's published figures. It's oranges to oranges and apples to apples. Very Happy
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Wed Jun 18, 2008 8:02 pm PostPost subject:
Yadaraf
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overconfident wrote:
@Yada,

OK. Makes more sense now that I see that you are simply trying to establish a relationship with K&J's published figures. It's oranges to oranges and apples to apples. Very Happy


Yea ... from what I can tell so far, the pull force test has a fair amount of sensitivity. With a small, short-range scale, I think it should be easy to classify a bunch of same-sized rod magnets into N35, N38, and N42 lots.

For example, Bob's rod magnet is 1/4" x 1/2", and if I can get my hands on a range of same-sized magnets with known origins and pull forces, I should be able to classify Bob's magnet.

Down the road ... as you know, it's difficult to label magnets, and the ink wears off, etc., making it difficult to know the magnet's pedigree. If we had a simple test that would classify "mystery" magnets (1/4" x 1/2" in particular), then that would be a good thing ... down the road.

Question Will we be able to classify Al's odd 0.540" magnets? Perhaps. Dunno at this time. I'd like to think so. One interesting question is, "If the fish test works, will Al spend $2.97 on a fish scale?" Laughing

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Thu Jun 19, 2008 5:17 am PostPost subject:
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Yadaraf wrote:

"If the fish test works, will Al spend $2.97 on a fish scale?"


That's what makes the Allegro chip so attractive. It's small enough to fit in the slot and measure the magnets in place. This is why I asked Al if he had one of those to give us readings from. It would be a shame to move the magnets and find out it was their position in the slots that made it all work. Neutral

I'll try and get a scale and get some references as soon as possible.

Cheers,
Cool
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Thu Jun 19, 2008 6:16 am PostPost subject:
Yadaraf
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Harvey wrote:
Yadaraf wrote:

"If the fish test works, will Al spend $2.97 on a fish scale?"


That's what makes the Allegro chip so attractive. It's small enough to fit in the slot and measure the magnets in place. This is why I asked Al if he had one of those to give us readings from. It would be a shame to move the magnets and find out it was their position in the slots that made it all work. Neutral

I'll try and get a scale and get some references as soon as possible.

Cheers,
Cool


I thought about the Allegro chip, but you now how circuit fabrication goes ... circuit boards, passive components, LED displays, power supplies all add up $$. And then it has to be sold and shipped to others who can't fabricate. More costs.

Correct me if I'm wrong, but at the end of the process the gage produces only relative results -- I don't believe the hall effect sensor can get close enough to accurately and absolutely measure surface field strength. And then there's the issue of calibrating the unit for different magnet geometries: 0.500" vs 0.540" vs 0.625" lengths.

.. Q: How much do you think the "variable" Allegro gage will cost in the end (circuit board, power supply, LED display, etc)?

I'm now looking for cheap fish scale that is available via the web. First I want to make sure I can replicate K&J's pull force test, which I believe I can.

I must say that the $2.97 scale that I bought is not very accurate at the low end, so I'm looking at another scale for $4.97 and a third (digital) for $14.97. However, I will test the latter two on site with weights before making a decision.

.. Mother Lode (cheap): http://www.mysimon.com/9000-11034_8-0.html?sdcq=dnatrs-scales-price_range_10_20/dfllTrail-Scales~%2410%20-%20%2420

.. Rapala ($15 @Target, WalMart, Sport Authority):




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Thu Jun 19, 2008 12:28 pm PostPost subject:
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Home Made Gaussmeter:

1.50 Allegro chip
0.80 7805 regulator
2.31 9V Battery
1.20 Battery connector
0.90 Test /Jumper Lead
0.00 Chop Stick
0.01 Tape
0.05 Solder
-----
6.77


http://my.execpc.com/~rhoadley/magmeter.htm
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Thu Jun 19, 2008 1:00 pm PostPost subject:
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I don't even bother with the circuitry. I just solder some leads to the thing and use the little benchtop regulated supply for power and read the output on the DVM or the scope.
But like the article says, the calibration is approximate and a fixture must be made to keep the sensor at a known distance that won't cause saturation.
I'll try to get some measurements using this method today.
Watch this space--but give me 8 or 10 hours...
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Thu Jun 19, 2008 4:59 pm PostPost subject:
Yadaraf
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Harvey wrote:
Home Made Gaussmeter:

1.50 Allegro chip
0.80 7805 regulator
2.31 9V Battery
1.20 Battery connector
0.90 Test /Jumper Lead
0.00 Chop Stick
0.01 Tape
0.05 Solder
-----
6.77


http://my.execpc.com/~rhoadley/magmeter.htm


Looks simple enough. Thanks. Looking forward to your data and a picture and dimensions of your magnet fixture. Wink


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Fri Jun 20, 2008 5:39 am PostPost subject:
Yadaraf
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RE: Very Fishy Fish Scale

The small orange fish scale in the above picture is not accurate at the low end, and a 4 lb weight registers slightly above 3 lbs. Forget about measuring 1 lb.

I tested a $15 digital scale this evening with good results. It did not use a spring, but rather a strain gage like in a bathroom scale, thus it was definitely more linear. I ran out of time and didn't have my magnet assembly with me, so the saga continues Friday. I believe the resoultion on the digital scale is +/- 0.2 lbs.

For the two thick steel test plates, it appears that large grade 8 bolts will work well, and they're cheap as well. Plating, however, seems to make a difference, and yellow zinc seemed better that galvanized. I wanted to try alloy steel -- automotive chassis grade -- but Home Depot didn't carry any. I'll stop by Lowe's or NAPA while I'm out tomorrow doing other stuff.

Cheers Smile
Yada ..
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Fri Jun 20, 2008 8:15 am PostPost subject:
Harvey
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I did a pull test and had some fun with my rotor on Bobs other base.

http://www.youtube.com/watch?v=LkJGA7V38fc

I'll be offline most of the next 3 days but will try to get online in the evenings.

Cheers,

Cool
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Fri Jun 20, 2008 8:38 am PostPost subject:
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Does your WM still run ?
Shocked
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Fri Jun 20, 2008 8:41 am PostPost subject:
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WM?

D'OH Embarassed

Still run?
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Fri Jun 20, 2008 9:22 am PostPost subject:
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In your YT vid I see you having fun with a scale, but as an aside your Whipmag keeps running or seems to do so, so my question is, does it still run? By itself ?
Or is there a fish scale connection that I've missed ?
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Fri Jun 20, 2008 2:08 pm PostPost subject:
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@JTF,

I would have to say there is a fishy connection of a miniscule scale. Mr. Green

Although there is a logical explanation I am under agreement not to disclose its functionality publicly. The technology I am using was offered to me by a researcher after 12 years of research resulted in a product which can now be purchased by the general public. If I were to disclose its function it would probably violate a trade secret which I have agreed not to disclose. I have found it interesting to study the affects of the product relative to the WhiPMag. Smile
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Fri Jun 20, 2008 3:44 pm PostPost subject:
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And the plot thickens...
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Fri Jun 20, 2008 4:22 pm PostPost subject:
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Harvey wrote:
I did a pull test and had some fun with my rotor on Bobs other base.

http://www.youtube.com/watch?v=LkJGA7V38fc

I'll be offline most of the next 3 days but will try to get online in the evenings.

Cheers,

Cool


Harvey,

Nice job. I'm not sure how to interpret the pull test when two magnets are conjoined, as opposes to one magnet and two steel plates. Shocked I'm still looking for plate material and am leaning towards large nuts and/or bolts.

I must say that we think alike, however, and I was considering a twist-cord as well. Cool I was also considering slowly filling a paint can with water.

One problem with using steel plates is that if the test is performed vertically (like in your video), then the weight of the plates will intefere with the direct measurement. The problem with performing the test horizontally is that there will be some friction to overcome.

... work in progress ...

Cheers Smile
Yada ..
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Last edited by Yadaraf on Sat Jun 21, 2008 3:11 am; edited 1 time in total
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Sat Jun 21, 2008 3:02 am PostPost subject:
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Yeah, thats why I mentioned a vise in the video. Turn the screw to open the jaws and voila!. Ok... that's a bit simplistic, but you get the idea. The two magnets were just to get an approximation for comparisons with other replicators and other stator magnets in my collection.
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Sat Jun 21, 2008 3:17 am PostPost subject:
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Harvey wrote:
Yeah, thats why I mentioned a vise in the video. Turn the screw to open the jaws and voila!. Ok... that's a bit simplistic, but you get the idea. The two magnets were just to get an approximation for comparisons with other replicators and other stator magnets in my collection.


Again we think alike. Cool When I mentioned the bolts, I also envisioned using the threads and a "carrier" nut to produce a crude linear translation -- more like an inverse vise.

Also, I find that attaching a thick rubber band to one end of the MUT (or plate) helps stablilize the test -- especially with the strain gage detector. By comparison, the spring gage is naturally forgiving. Your cord probably does the same thing as my rubber band. Wink

Cheers Smile
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Mon Jun 30, 2008 4:23 am PostPost subject:
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DAY 38

RE: Weighing heavily on my mind

I visited Fry's Electronics and evaluated five scales ranging from $69 to $169. I took a few pictures while I was there, but unfortunately the magnets got too close to the camera, and now the mem card needs to be reformatted.

I weighed three different magnet types, eight each:

ZD49, 1/4" x 9/16", N35,
R834DIA, N42, and
Bob's 1/4" x 1/2", N??

The R834DIA's were the trickiest, because of the cumulative pull-force. I had to elevate them 2" from the scale surface, using a small aluminum box. The scales themselves were not very repeatable, and placing the weights off-center produced wildly different results. Furthermore, the tiny hand-held scales measured 1 g heavier than the larger scales. Stay away from these.

Of the five scales, the best seemed to be the:

.. HL-200i: http://shop2.frys.com/product/4427876?site=sr:SEARCH:MAIN_RSLT_PG



It was fast, repeatable, tared quickly, and seemed accurate to 0.1g

For eight magnets:
ZD49: 27.7 g
R834DIA: 41.6 g
Bob: 25.1 g

Divide by eight:
ZD49: 3.46 g -- (K&J spec at 3.39 g)
R834DIA: 5.20 g -- (K&J spec at 5.19 g)
Bob: 3.14 g -- (Mystery magnet so far)

Calculate densities:
ZD49: 3.46 g/0.452 cc = 7.65 g/cc
R834DIA: 5.2 g/0.691 cc = 7.5 g/cc
Bob: 3.14 g/0.402 cc = 7.80 g/cc

I don't know what to make of the density calculations at this time, but I do feel confident about the measured weights, because they are close to K&J specs. I looked at some large N42 and N52 magnets on K&J's site, and they had the same weight and density, even though strengths were markedly different. They must use the same powder regardless of the magnet grade, which seems odd to me.

EDIT: After pondering the density issue, I came up with this: smaller magnets have a higher plating-to-powder ratio, which makes it difficult to calculate the density, since there is more than one substance to consider. Consider nickle-plating a grain of sand. Clearly, the weight of the nickle would be much more than the weight of the grain. Thus, IMHO density should not be considered a factor when evaluating nickle-plated magnets.

Next, I need to measure the pull force.

Cheers Smile
Yada ..
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Tue Jul 01, 2008 4:13 am PostPost subject:
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Hi all

Quote:

After pondering the density issue, I came up with this: smaller magnets have a higher plating-to-powder ratio, which makes it difficult to calculate the density, since there is more than one substance to consider. Consider nickle-plating a grain of sand. Clearly, the weight of the nickle would be much more than the weight of the grain. Thus, IMHO density should not be considered a factor when evaluating nickle-plated magnets.



Nail on the head

Who cares about what they weigh anyway Question
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it seems a shame, the walrus said, to play them such a trick
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Mon Jul 21, 2008 4:26 pm PostPost subject:
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Harvey you pull test was 3 pounds 7 oz for stator to stator magnet to stator magnet.

Did you do any for the rotor magnet to stator magnets?
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Mon Jul 21, 2008 7:01 pm PostPost subject:
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@lostcauses,

No I haven't Sad It will require some way to secure each magnet. One to the scale and the other to the twistline. I havn't imagined a foolproof way of doing this yet. I tried a plastic bag as someone suggested, but the 0.25" surface punched clean through the plastic. Besides that, I wasn't happy with having the separation between them anyway.
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Mon Jul 21, 2008 7:38 pm PostPost subject:
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I wasn't happy with having the separation between them anyway.

Looks like will have to use a clamp method to do such. Wood or plastic. Maybe even aluminum etc.

Are you getting over ten pounds with the pull of the stronger rotor magnets to stator?
I am trying to get an idea of gauge or scale limits (weights) one can use with this.
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Mon Jul 21, 2008 11:23 pm PostPost subject:
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The rated pull force for the 1/4" diameter x 1/2" long N42 Cylinders is 3.99 Lbs. This is based on two well permeated 1" steel cubes, one each attached at each polar end of the magnet. That test depends sharply on the steels ferromagnetic characteristics and any flux bleed through into the testing apparatus.

Testing the pull force of two magnets with poles in contact, one may intuitively expect twice the rated force or 6.98 Lbs. However this could be different because of the shapes involved. The square surface of the steel will tend to concentrate flux along the corner lines and depending on how sharp they are can radically bend the path away from the magnet under test. Conversely, the rounded corners of the magnet will tend to align symmetrically with the other magnet (within reason) possibly creating a stronger bond between them as compared to the steel.

However there are two other considerations here as well. The steel acts as a backing plate reinforcing the opposite pole of the magnet. Both ends of the flux are utilized in this test. The second consideration is related to the magnet to magnet test insomuch as their are two involved and the secondary poles are 'floating'. But really, they must complete the circuit and have a holding effect.

Finally, we need to ascribe force distribution; i.e 'per square inch' . I believe the 3.99 Lbs is considered to be an equal force spread accross the square inch block or actually an average for that surface. How this relates mathematically when reduced to a quarter inch diameter surface area would need to be addressed. Theoretically the tensile pull is the same on the Fish Scale regardless of the contact area under test, but the magnetic field itself plays a part in this due to the density reduction over distance. In other words a quarter inch round steel will be less than a half inch round steel etc. until all the flux is contained after which the increase inverts.

I just did 10 tests with my Fish Scale: Stator magnet on the hook, rotor magnet in contact. Wow! I never reallized how strong my fingernails were. The surface is too slick to grab by finger pressure. But because the stator magnet is radiused I can get my thumbnail and ring finger nail to hook on the edges of the rotor magnet and pull slow and even.
1. 3.1
2. 3.6
3. 3.1
4. 3.4
5. 3.2
6. 3.6
7. 3.1
8. 3.6
9. 3.4
10. 3.5

So I get an average of 3.36 rotor to stator at contact distance opposing B vectors aligned. At 6.35mm away I calculate a pull force of 0.42 Lbs. My math may be wrong here so triple check me.

Cheers,

Harvey

ETA: My Berkely Scale from Wal-Mart goes up to 50 lbs.
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