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Old Sep 20, 2002, 12:22 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
homemade remote actuator

I built this just before I went on holiday and before RCmicroflight's article showing a similar idea. It is based on what has been coined the tabmag in the UK by Eric Hook, he produced the first I ever saw although it was not built like this one.

I hope the photo makes sense, the coil is a tatty old self wound 100ohm job and the structure is made from pcb material although ply would be as good and lighter. The wire is piano but it should be copper/brass. This was a case of use steel or have no actuator for this late night creation.

It is esentially the same as a bird actuator except that the hinging is not that of the control surfaces. I added a pull-pull arm to mine.

I should mention that the wire peice can be made so that it wraps around the magnet, this is probably better than having a small balsa peice holding the magnet, also easier especially with copper wire.

This will be in an article but it seemed silly not to share it here as well, I suspect that others will fine tune the design and that can be presented.

Hope this helps those with a heavy tail.

Graham
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Old Sep 20, 2002, 01:05 PM
Stuck on a rock
epilot's Avatar
Faroe Islands, Sandoy, Sandur
Joined Nov 2000
5,881 Posts
Great minds think alike - I had doodled a design like that but my plan was to use litho plate for the frame (or alu from a beer can, but then I would have to empty it first )

You could loose the output arm by just extending the arm that holds the magnet.

Michael
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Old Sep 20, 2002, 01:15 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
The reason for the arm is that it was easy to drilln two holes then form them from the wire.

Graham
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Old Sep 20, 2002, 01:37 PM
Always looking UP
FANMAN's Avatar
Lilburn, Georgia, USA
Joined Nov 2000
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Pretty cool

Who is gonna start manufacturing these things? It would seem like they would be more and more readily available.

Any possibility of explaining (or showing) how the wires lead into the wrapped coil?
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Old Sep 20, 2002, 01:41 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
The process of making one is as easy as making undercarriage. Just a bit of wire bending. I sell bare coils 100/200ohm as do DU for the RFFS100 or you can wind your own. I might make a bending jig if there is enough interest, could do one for the RFFS coils as well.

I have a small circuit board bonded to the coil, this allows the wires to be soldered on. These beasts were replaced with homemade litz wire afterwards so save a few pounds of weight

Graham
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Old Sep 20, 2002, 01:52 PM
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dhurd's Avatar
Buffalo, New York
Joined Jan 2002
1,024 Posts
Fanman,
IF your looking for an actuator that has a control arm, someone already is manufacturing them. Bob Selman's actuators have control arms and alow you to remotely mount the actuators. Bob sells them (obviously) as well as myself. But then you don't get the satisfaction of having done it yourself.

Dan
DWE
www.smallrc.com
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Old Sep 20, 2002, 09:11 PM
Grand Poobah of Nothing
Trizza's Avatar
Once Australia, now Finland
Joined Feb 2001
1,022 Posts
How much does it weigh Graham? I might give this a shot.
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Old Sep 21, 2002, 04:24 AM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
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Not a lot, 0.7g possibly but it is over built and should weigh less, slap my wrists.

Graham
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Old Sep 21, 2002, 06:45 AM
Grand Poobah of Nothing
Trizza's Avatar
Once Australia, now Finland
Joined Feb 2001
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Right I think I'll give one a shot soon.
As an aside: I successfully made my first SMD version of my DPC/ESC. It weighs 2.5g with wires, the circuit board makes up a bit over a gram of that weight! I'm thinking of trying a piggybacked version.
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Old Sep 21, 2002, 09:03 AM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
By the sounds of it you used fairly thick circuit board. If you have a dremel and drumsander bit you can make it super thin and light.

Graham
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Old Sep 21, 2002, 10:47 AM
Crashmaster Extraordinair
Clarksville, TN
Joined Apr 2002
730 Posts
Bob Selman's MagAct is very similar to what you show here except that the magnet is mounted on an axis inside the coil and the arms are directly connected to the magnet. Nick Leichty also makes one that I havent had the pleasure of using but is much smaller and probably the same design as you show, possibly with the axle going through the coil instead of around (a much lighter solution considering the music wire for the axle is one of the heavier parts).

Bob Selman's MagAct (picture is of two mounted in the mutually-centering arrangement):

Cost: $15
Weight: 2.1g

Nick Leichty's Standard Actuator:

Cost: $40 / $75 / $100
Weight: .25g / .15g / .09g
The second and third numbers are the Mini and Micro versions of his actuator.

Also, RC Microflight published an article this month on doing a conversion of a standard actuator (coil+magnet) to a pull-pull arrangement by mounting it in a flat surface and attaching a metal yoke to the magnet that pivots on an axis outside the coul and has two attachment points for the strings. Unfortunately they dont provide any really good close-up pictures of the real thing and I dont want to link to the plan images themselves (subscribe if you want them, you wont regret it!).

Cost: scrap wire
Weight: coil+magnet+.25g
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Old Sep 21, 2002, 10:51 AM
Crashmaster Extraordinair
Clarksville, TN
Joined Apr 2002
730 Posts
also, something RC Microflight didnt think of and that I have been using in all of my pull-pull actuators since Bob Selman thought of it... If youre going to use two actuators, mount them so that the magnets are aligned when centered and have perpendicular axes of rotation. With MagActs the recommended spacing is approx 1" but you can adjust this to produce more or less centering force. Having them aligned makes them pull each other back to center, and having their axes of rotation perpendicular to each other (and to the alignment axis) insures that the magnets dont rotate each other off center (if you make the rotation axes parallel then when you turn one magnet the other will turn too).
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Old Sep 21, 2002, 12:38 PM
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USA, FL, Fort Lauderdale
Joined Feb 2002
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This is something I cobbled up based on a drawing by Graham some months ago. It uses a stock DU coil, and is made from 1/8" bass wood.

Dave W.
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Old Sep 21, 2002, 01:25 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
Spar, the point about this actuator is that it is easy to make yourself. The one shown in RCmicroflight is the same principle but I made mine before seeing that but it's (mine) not origional.

Nicks actuators use two coils with pivots between them I believe. Jberg has also done this as you will see in his depron guide mite thread.

The weight of the one I have made could be much less, a balsa base plate and 1/64th ply for the end plates. Then use aluminium wire for the axle etc?

Graham
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Old Sep 21, 2002, 01:45 PM
Was that my 15 minutes?
Andy Birkett's Avatar
Leicester. UK
Joined Jan 2002
117 Posts
Here my (unfinished) effort, waiting coil

This is made of a 3mm strip of card soaked in cyno and wrapped round the 3mm magnet. Two .5mm pins are the drilled into it and the all thing mounted on a piece of brass shim.
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