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Author Topic: MAGNETS . . .  (Read 1099 times)
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carpetbagger
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« on: February 05, 2014, 12:45:40 PM »

I play with electric RC and Free Flight and see several models that use magnets to hold on cowls and even wings. Cool idea, but . . . will a magnet mess up a radio control plane? If so is there a distance requirement for a magnet to electronics, including ESCs, and/or a distance from the Rx antenna? 
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Pit
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« Reply #1 on: February 05, 2014, 01:41:50 PM »

I do a lot of flying with models that are, as I like to say, "held together with magnets".  I have found no issues, but there is one area that I'm looking at a bit more closely.

That's where some models are using more than two magnets in the cowl area (near the motor).  It would seem to me that the fields in the motor (assuming electric power) and those set up by magnetic "hold-downs" might interact - possibly affecting the efficiency of the motor.  Probably not enough to be in any way important, as the motor case/bell prolly acts like a shield, but has gotten me curious.

Re the antenna: there is a basic rule of thumb to keep the antenna as far as possible/not touching from metallic/carbon components - FOLLOW IT.  I see many models with the ESC and the receiver in very close proximity to magnets with NO issues.

With the plethora of magetically held together models out there doing stuff that I can't even follow,  I think your worries are a non-issue.  Just follow the manufactures tips (if supplied) and a bit of old-fashioned common sense and you should have no problems.

YMMV (Your milage may vary)...
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alset
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« Reply #2 on: February 05, 2014, 01:44:49 PM »

I have not found any interference problems with magnets and RC components. I have never had any magnets closer than 3 or 4 mm though. I suspect that antennas are copper so would not be affected even if the magnet touched them. There are places on the Web that sell these magnets in bulk for very cheap, so check these out before you plunk down a lot of cash for just a few of them.

http://www.kjmagnetics.com/products.asp?cat=10
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carpetbagger
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« Reply #3 on: February 06, 2014, 06:02:46 AM »

Thanks, Pit. 3mm to 4mm is tighter than my plan which is more like 25mm from wires & electronics. Wow, I'd need to fire up my magnifier lamp to play with some of those dust-speck magnets on the site you linked to. cool . . .
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Konrad
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« Reply #4 on: February 06, 2014, 10:18:07 AM »

I too had this concern early in my electric power days, (1986). As I recall the magnetic field dissipated very rapidly by distance, law of inverse squares. My initial concern was with this placing two motors right next to each other, like in some gearboxes. The magnetic field of one motor has very little impact with the other.

But do avoid moving wires near a magnet. This might be the old 72mHz antenna whipping around in flight.  So unless there is movement relative to the magnets, there are no issues with the RF section of a RX when using magnets as hold downs

Now EMI is a real concern. I still have a habit of wrapping ESC and RX in foil to make a faraday cage if I have them in close proximity, touching, each other.

All the best,
Konrad

http://en.wikipedia.org/wiki/Inverse-square_law
http://en.wikipedia.org/wiki/Faraday_cage
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carpetbagger
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« Reply #5 on: February 06, 2014, 02:06:42 PM »

Foil wrap - HA. Jogged memories out of the dust bunnies in my brain. In the `70s a company in Falls Church, VA bui9lt one of the first RPV drones. Since I owned a rather large hobby in the vicinity I heard of lot of drone chatter since most of the folks working on the project were R/C fliers. The basic start up experimental used a standard radio (apparently souped up to extend the range), a 4-stroke gas burning ignition chain saw engine, and had an on-board TV system so the drone pilot could fly it via view from the drone's TV camera. An EMI/EMFnightmare it was, and one of many mods was to foil wrap servos. Also shielded cables, aircraft style shielded ignition system, etc, etc . . .
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mjmccarron
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« Reply #6 on: April 16, 2014, 11:11:17 PM »

I've been using rare earth magnets for some time now to hold down hatches, cowls, and even for wing attachment with no adverse effects. Unless they are very near a coil and moving, there is little to no danger of EMI. It would be hard to get them close enough to sensitive electronics to pose much of a threat.
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Ouzel von Schwartzwolfe
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« Reply #7 on: October 14, 2015, 02:11:11 PM »

Don't worry about any use of Magnets in your plane hulls guys, the field is stable (not changing in size) and not moving around inside and will not make any interference for the radio or receiver, CD cards and programmable controls should stay away from them and the motors. an inch or so is more then enough. (Magnets can but not always fubar the data in any kind of memory "thingy whats its"  by moving over or near it) you can mess up a memory card by wiping a mag over it a bunch of times but you have to work at it.   By the way the Motors are the most powerful magnets on any plane unless you put a REM as big in your plane for some reason Grin  and it still at worst could stop a servo from moving but not likely.

I hope this set your mind a easy about using magnets as hold downs.

and if you are still worrying about them "Velcro" is ligther and can be just as strong. Smiley
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