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Old Feb 10, 2013, 11:38 PM
Good Better Best quest.
olmod's Avatar
Australia, VIC, Cranbourne East
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Quote:
Originally Posted by salty9 View Post
Not necessarily. Check http://www.rcgroups.com/forums/showt...ighlight=gauss

Educational and funny.
I did contribute to that thread now we have thin film hall effect devices available that can be used ,but you must build the stylus probe and design/build an amplifier then calibrate it, if you want low cost. device mfgs often have suggested circuits published in data/application sheets.
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Old Feb 23, 2013, 01:27 AM
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Originally Posted by jackerbes View Post
Are they of a size not found here?

http://www.kjmagnetics.com/products.asp?cat=168

Or here:

http://www.supermagnetman.net/index.php?cPath=37

Seem like a shame to not be able to find them...

Jack
No luck with these two local mag suppliers KJ only dose SAE and Supermagnet Man's Meredith never responded to my inquiry. Although the site (SMM) says custom magnets are not to costly to have made. After the first batch you own the mold so subsequent purchases are more economical .But I have no info further than that.
But I found this company. I just ordered 20) 10mm X 2mm X 5mm N42 with shipping from the old world for $14.20 https://www.hkcm.de/hkcm.php/?ad=
Working on cobbling together a reference tool for checking magnets. Thanks for all the ideas.
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Old Feb 23, 2013, 07:53 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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"..No luck with these two local mag suppliers ..."

Yeah, you're right. These magnets are not being merchandised very aggressively at all. I'm sure most of the ones on the motors we rewind are probably out of China and not many hits come up for places to buy them or the sizes and shapes we see in the motors.

It is almost dumb luck to get ones that are the same size. Micro Dan probably has the largest assortment of magnets that are about right.

Jack
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Old Feb 23, 2013, 09:28 AM
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Take a look at HKMC they have sizes MD dose not carry. SMM dose have several viable sizes just not what I need for a Eflite Park 480. I bought it for an E-flite Twist 480 (which I twisted right into the ground) The plane with that motor (added an oz. vs my Axi 2808) and real wheels (another oz.) became a beast. It was great before those changes... and then it got changed a whole lot. I'm repairing the frame and took the motor out to change the shaft. That's when I noticed the 890Kv motor I bought in the box from the LHS was not. Turns out it's the 1020Kv know wonder why the dern thing was so fast, swinging a 12X6E.
During shaft change I was marveling at the incredibly unexciting the magnets were and how ruff looking they were. Also was looking for cracks. It checked OK and when I tried to reassemble low and be hold it jammed up. Turns out it did have broken magnet. They are 10X2X5, MD carries 10x2x4. The windings look good for an OEM and it so happens I have an E-flite Stagger-wing that is made to order for this motor. So it will get some N42 replacement magnets. It would be nice to know what the stock magnets were. I'm going to save them so when I get my tool going I can maybe shed some light on it.
As far as the Twist 480 goes I'm on a quest for a 75g motor I can wind into a 890Kv that will swing a 12X6SF. I have a 2215 that will do it but I'd like to find a 2808 for it. I ordered 1) each brand (regardless of Kv) of 3530 (AKA 2808) from Leaders hobby. ranging from $6.00 to $16.00 got 6 motors coming for about $50.00. I should be able cobble up a good Frankenstein motor from the selection of parts. Although I guess that's not a good analogy as Frankenstein monster was made from dead parts, these are all new.
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Old Feb 23, 2013, 10:29 AM
Jack
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"..As far as the Twist 480 goes I'm on a quest for a 75g motor I can wind into a 890Kv that will swing a 12X6SF..."

It it is the prop you are looking at, the data on the APC 12x6 SF at flybrushless.com makes it look like it will take 250 Watts or so to get that prop up around 5,000 RPM. The prop is rated for about 5,400 RPM max.

But 75 grams will get you into some nice 28mm O.D. (22mm stator) motors that can be rewound to get you a 250W continuous motor.

At my house, and if there was room for it, it would be a job for an 80 gram DAT-750. That is one that can run all day at the 250W level. Here is the eLogger data on a rewind with 18 turns of 22 AWG in a Half Parallel dLRK wind with a Wye termination, the Kv was 911 on that. And if I remember right, that wind could be done with 21 or maybe even 20 AWG wire to kick the allowable current draw up a little more.

The DAT-750 dimensions are in the second image.

So many options to agonize over...
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Old Feb 23, 2013, 11:12 AM
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Well as of this date my collection is missing a DAT-750. I guess I'm like a car collector that doesn't have a model T....yet. Whats the height on the 750 stator?
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Old Feb 23, 2013, 12:17 PM
Jack
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Originally Posted by zeroback View Post
Well as of this date my collection is missing a DAT-750. I guess I'm like a car collector that doesn't have a model T....yet. Whats the height on the 750 stator?
Think of it as a Harley-Davidson more than a Model T. The Model T was much newer.

I think the back of the windings to the front of the magnet housing where the shaft emerges is like 19mm or so. As is seen there it is in it's supplied mount and that pretty much has to be used. You have a bearing tube (8mm or 9mm depending on how old it is) a mount is supplied to fit the tube. Two grub screws retain the tube in the mount.

So if you attached the mount to the firewall on the Twist with the grub screws on the top and bottom you could access them OK. You cannot normally access the screws that hold the mount to the firewall with the motor mounted as the motor's 40.3mm diameter blocks access to those.

Maybe I can loan you a motor to try? I should spin up a APC SF 12 x 6 first to see if that will work OK. I know a 12 x 6 or even 13 x 8 TE will work though.

Jack
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Old Feb 23, 2013, 08:46 PM
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Is this a carnation of a 750? When you mentioned that motor size I got to looking at my coveted pile of burned out motors and I'm thinking this is one with different dressing.
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Old Feb 23, 2013, 09:36 PM
Jack
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Dr Kiwi tested that motor, the data is on flybrushless.com:

http://www.flybrushless.com/motor/view/543

It handled about 300 Watts with an APC E 11x5.5 on 3S, a APC 12 x 6 SF would be a bit more of a load for it but a rewind should do the trick.

You don't hear much about those motors.

50 Cents, sounds like a killer deal,,,

Jack
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Last edited by jackerbes; Feb 24, 2013 at 07:53 PM.
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Old Feb 24, 2013, 02:35 PM
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The web site is not real informative either.
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