HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Aug 30, 2002, 04:22 PM
Registered User
jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
954 Posts
Depron Guided Mite

Hi,

that's my Guided Mite. It is ready finally. I've built my own actuators and glued them into the tail surfaces. Since my actuators weigh 1g each, there was no hope to get the CofG right. So I rebuilt the actuators as internal ones, axes crossed in the Ruijsink/Selman style. I've connected the ruder and elevator with 0.7mm CFK and small pieces of music wire (true music wire: a western guitar string of 0.4mm).

Motor is a KP00 with self-made BB gearbox 7:20 and a prop from my Micro Taxi. Rx is an ACT Pico 4uP (35MHz). I've exchanged the PIC processor on the board with one that drives two coils and a FET for ESC (thanks again, Graham!). I've also put a voltage booster (SOT23 charge pump) onto the rx board that provides the rx and coils with 5V/50mAh. So the space where the former standard plugs have been is now of some use! The antenna is from magnet wire now, and I've also exchanged the standard size crystal (huge and heavy!) with a GWS one (1g of weight gain). The rx is in the 5g range now, complete with coil drivers, ESC and DC booster.

Battery is one 140mAh LiPoly cell.

Now wish me low wind tomorrow! The little bird glides ok and is controllable, so it should work. All-up weight is 26,9g, so the wingloading is about 8g/dm^2.

Regards, Jochen
jberg is offline Find More Posts by jberg
Last edited by jberg; Sep 10, 2002 at 05:52 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 30, 2002, 04:28 PM
Registered User
jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
954 Posts
And another pic

Here you can see the control horns. The actuators are glued to the inside of the fuselage.

So I am in the sub-ounce class finally!
jberg is offline Find More Posts by jberg
Reply With Quote
Old Aug 30, 2002, 04:49 PM
Registered User
Leicester England
Joined Jun 2001
591 Posts
Sure flyer

That will fly great - rudder looks a bit small from the angle in the photos?

Power to weight is very good, the other guys are reporting 20 to 30 minute flights from similar machines. Wheels should be good in the snow this winter (designed by Barny Rubble!?)

If only we had a similar size machine with ailerons ....
Maybe a 13" span Lazer 200? I wounder what one of those would look like if it was made from stick and tissue maybe?

Aeronutz news letter is on the way ....

Its going to be a great winter season for indoor fliers
Mark
aeronutz is offline Find More Posts by aeronutz
Last edited by aeronutz; Aug 30, 2002 at 04:53 PM.
Reply With Quote
Old Aug 30, 2002, 05:07 PM
Registered User
jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
954 Posts
Re: Sure flyer

Quote:
That will fly great - rudder looks a bit small from the angle in the photos?
It is bigger than the original one, which looked too small to me (but my lightest plane so far has 48g).

Quote:
Power to weight is very good, the other guys are reporting 20 to 30 minute flights from similar machines. Wheels should be good in the snow this winter (designed by Barny Rubble!?)
I don't know Barny Rubble, but you are probably right! I've had not very much luck with Depron wheels up to now, so these were meant to be *sturdy* (which they are).

Anyway, thanks for your encouragement!

Quote:
Its going to be a great winter season for indoor fliers
Yes, definitely! My next model will probably be an Aeronca C3, sized up from a Fiddler's Green plan. Or an even smaller Junkers F13 (my favourite, for being high-tech of its time, civilian, economic, and German).

Regards, Jochen
jberg is offline Find More Posts by jberg
Reply With Quote
Old Aug 30, 2002, 06:14 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
looks like a winner!

I think Mark was thinking of the flintstones
Graham Stabler is offline Find More Posts by Graham Stabler
Reply With Quote
Old Aug 30, 2002, 10:18 PM
Living Room Aviator
drliu's Avatar
Joined Jun 2002
269 Posts
Nice Work Jochen! Best of all, if you ever get hungry flying your plane you can toast the wheels and make smores.

Let us know how the first flights go!

-David
drliu is offline Find More Posts by drliu
Reply With Quote
Old Aug 31, 2002, 12:33 AM
Grand Poobah of Nothing
Trizza's Avatar
Once Australia, now Finland
Joined Feb 2001
1,022 Posts
Hey nice!

Can I have a bit of info about how you did the internal actuators? Photos maybe?
Trizza is offline Find More Posts by Trizza
Reply With Quote
Old Aug 31, 2002, 03:48 AM
Registered User
jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
954 Posts
Ah, that Barny! We know him as "Barney Geröllheimer" here.

Dave, my dictionary has to pass on "smores". Anyway, you all help me improve my English very much!

Trizza, here is a picture of the magnet and the diamond tool I have used to drill a hole in it:
jberg is offline Find More Posts by jberg
Reply With Quote
Old Aug 31, 2002, 03:50 AM
Registered User
jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
954 Posts
And that is the complete double actuator, together with the modified receiver (with the DC booster still missing):
jberg is offline Find More Posts by jberg
Reply With Quote
Old Aug 31, 2002, 08:23 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Jochen,
You may have the first oval wound actuator coils. Do you have any idea what their current draw is and how much force they generate? What do they pivot on? Brass or ball bearings, or other? Very nice building of equipment.

Smores are (I think, never having been a girl scout) toated marshmellows between chocolate bars of some sort.

As Mark says, this looks to be the best indoor season yet.

Gordon
Gordon Johnson is offline Find More Posts by Gordon Johnson
Reply With Quote
Old Aug 31, 2002, 08:33 AM
Registered User
jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
954 Posts
Gordon,

they are wound of 2x300 windings (each actuator) of 0.05mm magnet wire, have 200 Ohms and pull around 20 mA at the PIC outputs (which are at about 4.2V when using 5V as supply).

I have measured slightly above 1gcm of torque, so with my 5mm control horn I have about 2g at the pushrod.

The bearings are made of PVC tubes, these are originally inner bowden cables and are 2x1mm outer/inner diameter. The axle is 1mm carbon rod.

I like sweet things, especially chocolate, very much, but I doubt that I would like smores!

Regards, Jochen
jberg is offline Find More Posts by jberg
Reply With Quote
Old Aug 31, 2002, 11:15 AM
Living Room Aviator
drliu's Avatar
Joined Jun 2002
269 Posts
Jochen,

Can you tell us the weight of your actuators? They look very interesting.

My joke was to notice that the cute wheels on your plane look like marshmallows! yummy...

From my own experience:

Actuator (including magnet) weights
----------------------------------------------
RFFS: 978 mg
Didel Nanobird (large, 30 ohm): 709 mg
Didel Nanobird (small, 50 ohm): 427 mg
Nick Leichty standard actuator (unwrapped): 200-220 mg

Of course weight means nothing unless your actuator is powerful enough (more on this later from Gordon, others, and myself).

-David
drliu is offline Find More Posts by drliu
Reply With Quote
Old Aug 31, 2002, 11:26 AM
Registered User
jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
954 Posts
Dave,

the magnets are arount 0.4g, as are the coils. When the single actuators were ready they weighed about 1g. After connecting them to a double actuator and adding a little CA here and there to protect the delicate windings I came out at about 2.3g for the pair.

An interesting question would be how the optimum relation between copper weight and magnet weight would be, if you, say, set 1g of maximum weight and 4.2V/20mA as maximum power.

For instance, if it turns out that the torque is directly proportional to the magnet weight and directly proportional to the copper weight then the optimum of magnet weight times copper weight would be when both parts have 0.5g.

When we choose to work with 4.2V/20mA = 210 Ohm then we have to double the number of windings when we take a wire of double area to get the same resistance. Since the magnetic fiield is proportional to current times number of windings then it would be proportional to the square root of the copper weight.

A nice optimization task. Anybody willing to do some variation calculus?

I have a 0.1g scale (Soehnle) so there are no more precise numbers, sorry.

Regards, Jochen
jberg is offline Find More Posts by jberg
Last edited by jberg; Aug 31, 2002 at 11:31 AM.
Reply With Quote
Old Aug 31, 2002, 04:59 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
Jochen, doing a bit of maths on the old actuators has been on my todo list for quite a while. It is difficult as sometimes we want min weight for a given torque, sometimes the best torque per gram for a given voltage and current. I might have a play if I get bored of sunning myself. The difficulty is modelling the physical effects of coil dimensions etc. For example a smaller hole in the actuator should give more turns for a given resistance and do the outer turns on a larger coil contribute as much as inner ones, when does a coil get too big for its boots. All very confusing.

Last post for a while

Graham
Graham Stabler is offline Find More Posts by Graham Stabler
Reply With Quote
Old Sep 01, 2002, 12:16 AM
Grand Poobah of Nothing
Trizza's Avatar
Once Australia, now Finland
Joined Feb 2001
1,022 Posts
Very interesting. Nice job!
What size are your magnets?
Where did you get the diamond tool?

You know somethings small when a 1mm carbon rod starts looking like a 3mm carbon rod in comparison to everything else
Trizza is offline Find More Posts by Trizza
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Profile Guided Mite plan Ralph B Scratchbuilt Indoor and Micro Models 7 Aug 02, 2004 08:01 AM
Lastest on Profile Guided Mite with DU system fill Scratchbuilt Indoor and Micro Models 17 Feb 19, 2002 02:23 PM
Profile Guided Mite joe price Scratchbuilt Indoor and Micro Models 4 Dec 04, 2001 01:39 PM
profile Guided mite finished! Paul Penney Parkflyers 6 Nov 30, 2001 03:38 PM
My profile guided mite Paul Penney Parkflyers 4 Nov 23, 2001 06:20 PM