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Old Sep 17, 2006, 12:57 PM
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Here's a short video clip of the Minimum:
http://www.rcgroups.com/forums/showthread.php?t=570963

Unfortunately the cameraman was a bit distracted and didn't stay on the Minimum all the time. That's why some of the best parts are missing. Enjoy, nevertheless.

Jochen
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Old Sep 09, 2007, 02:14 AM
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Hi again,

after my good experiences with the Micromum trikes (v6 and v8), I've decided to update the Minimum to a trike, too. The trike's better-looking (I think), a bit easier to build, and if you put a rudder on it, ROGs should be able even from grass surfaces.The good natured flying characteristics have survived the conversion and even the building instructions haven't changed very much. That's why there'll be a good deal of referencing the old instructions in the new ones.


Let's start with the pivot hinge and control arm. The instructions in post #4 still apply with two exceptions. There's no need for cutting the M4 thread as far as it will go, just use an 8 mm long aluminium tube with an I.D. of 5 mm instead of the 5 mm long one. As this moves the rotor up a bit you can now use a 4 mm thrust bearing instead of the original 5 mm one.


The first major changes concern the airframe (see Airframe drawing). Both the rotor mast as well as the support strut now have an O.D. of 5 mm, there's no bottom plate any more - that's why the main boom has grown out front -, and there's a new motor mount. The list of materials needed for the airframe now looks something like this:
- one piece of cf tube, O.D. 8 mm, I.D. 6 mm, length 170 mm
- one pieces of cf tube, O.D. 6 mm, I.D. 4 mm, lenght 120 mm
- one piece of cf tube, O.D. 5 mm, I.D. 3 mm, length 290 mm
- one piece of cf tube, O.D. 5 mm, I.D. 3 mm, length 230 mm
- one piece of cf tube, 6 x 6 mm, I.D. 4 mm, length 80 mm
- one piece of aluminium or brass tube, O.D.6 mm, I.D. 5 mm, length 35 mm
- one wheel collar, I.D. 6 mm
- two wheel collars, I.D. 8 mm


Use the building instructions in post #5 are still valid most of the way. Just don't build the original motor mount (the short 4 mm and 6 mm cf tubes), drill two 5 mm holes into the main boom for the rotor mast and support strut, use the slightly longer aluminimum tube to reinforce the top of the rotor mast and glue all three wheel collars on now. The third wheel collar is epoxied to the front end of the main boom in this version. There's one part left in the bill of materials we haven't yet used. That's the square cf tube with the round hole down the lenght of it. If you can't find this type of tube, use a round cf tube with an O.D. of 6 mm and an I.D. of 4 mm instead. Epoxy this tube to the bottom of the main boom, about 2 mm behind the bottom end of the rotor mast, rectangular to the main boom and to the rotor mast (see BottomView drawing). This part will take the axle of the main landing gear later on. To give the airframe the stability needed, take epoxy drenched cf rovings and tape the joint of the rotor mast with the support strut, the joint of the support strut with the main boom and the joints of the rotor mast and landing gear support with the main boom with those rovings. Make sure that the landing gear support is well fixed to the main boom.


The bottom plate of post # 6 doesn't concern us any more, instead of this we'll build the front wheel suspension and the motor mount (see MotorMount&FrontWheel drawing). For the front wheel suspension you'll need:
- one piece of cf rod, O.D. 4 mm, length 150 mm
- one piece of cf tube, 6 x 6 mm, I.D. 4 mm, length 40 mm
- two pieces of beech wood, 6 mm x 5 mm, length 40 mm
- one piece of cf sheet, at least 1 mm thick, 25 mm x 85 mm

Here's that odd bit of square cf rod again. To replace this part, epoxy a cf tube with an O.D. of 6 mm and an I.D. of 4 mm into a cf tube with an I.D. of 6 mm. Then sand the top and sides - if there are such things - of the outer tube down to the inner tube, and you've got something which, while not being exactly square, will do.
Cut the 1 mm cf sheet into two parts of roughly the size of the wheel supports and fix them together with some double-sided adhesive tape. For this kind of operation I'm using the type of tape which is normally used for sticking photographs into albums, it's thin, just strong enough and easily removable. Now print out the shape of one support on a sticky label of the right size and stick it onto the cf. Then cut the supports down to the correct size and drill the 2 mm holes for the axle and the two 2 mm screws. Take those two supports apart again. Use the same method to stick the two beech wood pieces together and stick one of the wheel support onto the side of this pack, correctly aligned, of course. Use the holes in the support as a template for drilling the two screw holes into the wood. Remove one piece of beech wood, replace it with the 'square' cf tube and drill again. Take everything apart again and stick the 4 mm cf rod into the round hole of the square tube. The front ends of both parts should be flush. First drill one hole through the round cf rod, put an O.D. 2 mm piece of anything through this hole and drill the other one. To keep the ends of the 'square' tube from splitting up under stress, tape them lightly with epoxy drenched cf rovings. Then sand some cut-outs in the wood pieces to allow for the tapings and reassemble everything, using 2 mm screws of 20 mm lenght. From a 3 mm piece of ply cut out a rectangular piece of the size of the battery you are going to use and stick it on the top of the front wheel suspension with some good double-sided adhesive tape.

The suspension just described will take the usual 65 mm slow-fly wheels, which have a width of just below 14 mm. If you are using thicker wheels, you'll have to increase the thickness of the beech wood parts to the size of your tyres.

The axle for the front wheel is a short cf rod with 2 mm diameter, held in place by wheel collars at both ends. For the main landing gear use a 3 mm cf rod with a lenght of about 330 mm. Slip a piece heat-shrink tube with an I.D. of 3 mm and a length of 90 mm over the cf rod and center it - no need to shrink it. This will protect the cf rod from breaking all too easily at the edges of its suspension. Then thread the axle into the 4 mm hole of the square cf tube below the main boom. Tape some textile adhesive tape around the axle and the heat-shrink tube on both sides of the square cf tube to keep the axle centered. To keep the wheels of the main landing gear in their proper postions, I use heat-shrink tube on the insides and wheel collars on the outside.

I've enlarged the original holes in all the three wheels to a diameter of 3.2 mm. This gives you a good fit for the main landing gear. Into the hole of the front wheel I've pressed a 15 mm long piece of my ever-present outer bowden cable tube. This has an O.D. of 3.2 mm and an I.D. of just over 2 mm and gives you the perfect fit for the 2 mm axle.


Cut the main parts of the new motor mount from 3 mm ply and drill the two 3 mm holes as shown. I suggest that you make the mounting plate that will hold the motor about 10 mm longer on the right side and cut off what you don't need later. Glue one of the parts that fixes the motor mount to the airframe to the mounting plate. Wrap a layer of shrink-wrap around the airframe, put your glued-together parts on the shrink-wrap and glue the remaing part to the motor mount. Insert the wedge that ensures a horizontal motor position into the U of the motor mount. Stabilize everything with the triangular moldings. If you want some extra strenght in the motor mount, you'll have to make those moldings by youself. Take a 6 mm balsa plank and cut out a triangular part by sawing perpendicular to the grain at an angle of 45 to the surface. This way the balsa fibers will run from one piece of ply to the other one, providing a very strong connection. Use a 3 mm screw to fix the motor mount to the airframe.


Post # 7 with the instructions for the tail unit is mostly valid again (see RudderFin and ElevatorFin drawings). Here are the alterations. The new tail boom has been shortened from 300 mm to 245 mm. I've discarded with the 3 mm x 0.3 mm cf rod glued to the leading edge of the elevator fin and am now using a 3 mm x 0.1 mm cf strip glued all around the elevator, which improves stabilty. And the 1 mm struts with a lenght of 195 mm have been replaced by 1.5 mm struts, 155 mm long.

There are two ways of making the pilot figure. The first one's simple. Cut the pilot from 6 mm Depron, using the outer contour of the Pilot drawing. The second one's better, because it gives you a pilot figure that can take more abuse. Cut the figure twice from 3 mm Depron (outer contour) and insert a thin layer of gf (inner contour) between those parts.


Build the rotor as described in post #8 (see RotorHub-ccw drawing), only make it turning ccw instead of cw. But you can use the old style head too, if you prefer a cw rotor.


Not many changes in post #9 up to the part when I talk about the motor mount. Use some double sided adhesive tape to stick your motor to the mount provisionally, in the position I suggested in the plans, install the pilot as shown in the first picture and adjust the hang angle to something like 8 by moving the whole front wheel/battery unit forward or backwards. Now have a look at the video in this thread:
http://www.rcgroups.com/forums/showthread.php?t=656504.
Adjust your motor offset to the right until you've got the prop wash compensated, then drill the appropiate holes, cut off the unneeded parts of the mount and fix your motor.


Now mount your rotor, program your Tx, read post #12 and have a good time flying the Minimum v2.

Jochen
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Old Sep 12, 2007, 03:43 PM
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And here's a video of the v2:

http://www.rcgroups.com/forums/showt...49#post8165897

Have fun,
Jochen

Edit: the link above is no longer valid, use this one:

http://www.rcgroups.com/forums/showthread.php?t=741749
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Old Sep 12, 2007, 06:52 PM
FPV really is fun.
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Wow! I love the steep banked turns and how slow it flies. Great job.
Scott
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Old Sep 13, 2007, 05:59 AM
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Scott,

as I've never flown a helicopter, my gyros tend to end up flying more like a plane, and I fly them that way.

Jochen
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Old Sep 18, 2007, 05:56 PM
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I couldn't bear the poor quality of the video here

http://www.rcgroups.com/forums/show...749#post8165897

any longer. I chucked the Windows Movie Maker out of the window and got myself something real. Result: smaller size, better quality, same location.

Jochen

Edit: I was wrong about the same location. The new one is:
http://www.rcgroups.com/forums/showthread.php?t=741749
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Old Sep 18, 2007, 11:31 PM
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Quote:
Originally Posted by JochenK
I couldn't bear the poor quality of the video here

http://www.rcgroups.com/forums/show...749#post8165897

any longer. I chucked the Windows Movie Maker out of the window and got myself something real. Result: smaller size, better quality, same location.

Jochen
Jochen,
link seems to be invalid.
Stephan
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Old Sep 19, 2007, 02:12 AM
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Stephan,

thanks for finding out. Here's the correct link:

http://www.rcgroups.com/forums/showthread.php?t=741749

Can't understand why the link changed when I just replaced the video in this post.

Jochen
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Old Oct 01, 2007, 02:31 AM
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Two new in-flight shots of the Minimum v2. The first one's at full speed and the second one shows the Minimum in autorotation, preparing for touch-down.

Jochen
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Old Dec 09, 2007, 09:54 AM
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Minimum v4 - the two-blader

The conversion of the three-bladed Minimum v2 to the two-bladed v4 took me longer than I thought because I started out on the wrong foot. My own fault. When I made the blade shims for the fisrt prototype, I built them with a leading edge thickness of 0 mm and a trailing edge thickness of 3 mm instead of the 1mm / 3 mm I had used before, without noticing what I had done. And then, when I started the flight tests of the v4, I found out that I didn't have enough lift. And did I search for that missing lift! Juggeled around with the c.g. and motor position, but nothing really seemed to work. The problem resolved itself when, after one of my numerous crashes, one of the shims went missing, and I had to build a new pair. Got it right this time, and from then on it was relatively easy. During this test phase I found out that v4 can do loops and even the rolls aren't too barrel-like. But there's not going to be an immediate repeat performance.

The plans have been ready for some time and so was the gyro built using these plans, but only yesterday the weather conditions allowed a test flight of the final version. Went well, so here are the plans - as usual in two versions, *.jpg for looking at and *.pdf for printing out.


Technical data:
DC rotor, two-bladed, 2" Aerobalsa rotor blades
rotor diameter: 1120 mm / 44"
AUW: 490 g / 17.3 oz.
RC functions: roll, pitch and throttle
battery: 3S/910 mAh LiPo
motor: Plettenberg Freestyle 24, 75 g, turning a 9x4.7 APC Slow prop at 8650 /min while drawing 12.5 A
servos: 28 g / 1 oz., metal gears


The pivot hinge and control arm are identical to v2, look at post #4 for building instructions.

The angles of the airframe and the length of the rotor mast have changed (see Airframe drawing). This is the new bill of materials:
- one piece of cf tube, O.D. 8 mm, I.D. 6 mm, length 170 mm
- one pieces of cf tube, O.D. 6 mm, I.D. 4 mm, lenght 120 mm
- one piece of cf tube, O.D. 5 mm, I.D. 3 mm, length 300 mm
- one piece of cf tube, O.D. 5 mm, I.D. 3 mm, length 230 mm
- one piece of cf tube, 6 x 6 mm, I.D. 4 mm, length 80 mm
- one piece of aluminium or brass tube, O.D.6 mm, I.D. 5 mm, length 35 mm
- one wheel collar, I.D. 6 mm
- two wheel collars, I.D. 8 mm
The building insructions remain the same as for v2.

The battery tray is new (see MotorMount&FrontWheel drawing). Cut the actual tray from 3 mm ply and cut a 5 mm wide slot into the rear end of the tray. This slot fits over the rotor mast support strut. Glue an 8 mm wide strip of balsa to the underside of the tray, at least as thick as the rim of the wheel collars you put on the airframe - 2 mm in my case. Glue two 5 mm x 10 mm wide strips of beech wood or similar to each side of the above mentioned balsa strip. The whole unit should now fit over the front part of the airframe, between the wheel collar and the support strut, with the tray sticking out in front. Use a rubber band to hold the battery and tray in place.

The front wheel unit is identical to v2, except for the thickness of the two cf parts holding the wheel. During one of my crashes those two parts broke, while the 4 mm cf rod - which is intended to break in such a case - remained intact. That's why the cf parts now have a thickness of 1.5 mm instead of 1 mm. Building instructions are unchanged.

The shape of the flanges of the motor mount and the wedge have changed a bit to fit the new mast rake, otherwise it's identical to v2, as are the instructions.

The only change in the tail unit is the length of the cf tube used: 250 mm instead of 245 mm. Building instructuions are unchanged.

The two-blader needed a new pilot, specially trained for flying these kind of gyros. Instructions remain the same.


The rotor is new, of course (see drawing rotorhub). Cut the flapping hinge out of 0.5 mm gf using the pdf-printout as a template. Mark the holes for the pivot hinge (8 mm) and rotor blades (3 mm) and drill them. Do not drill the 4 holes that hold the hub together. Cut the upper rotor hub out of some strong 2.5 mm plywood, again using the printout as a template. Mark the position of the central hole (8 mm) and the four outer holes (3 mm) and drill them. Sand the straight sides of the hub where the flapping hinge goes so that the sides are leaning inwards at the upper edge by about 30. Now cut out the bottom rotor hub and drill it's central hole.

Take a short piece of 8 mm O.D. rod and slip the bottom rotor hub, the flapping hinge and the top rotor hub on this rod. Align everything and use the holes in the top rotor hub as a template for drilling holes in the flapping hinge and the bottom rotor hub. Put a 3 mm screw in each newly drilled hole to hold the parts in place. Put marks on the three parts so you can reassemble them in the same position. Dismantle, bolt the upper and lower hub together and sand the lower hub to the shape of the upper hub, keeping the straight sides vertical this time. Take the two ball bearings and carefully epoxy them into the central holes of the upper and lower rotor hubs. Dismantle again. Make some counterbores in the top rotor hub for countersunk M3 screws and then put the flapping hinge between the hub parts and bolt together using those screws. This way you'll get a flat upper hub surface, which will protect the rear ends of your blades in crashes.

Cut two blade holders out of 2.5 mm plywood and two shims out of 3 mm balsa. These parts have the identical dimensions. Drill the holes for the blade-holding screws and sand down the balsa shims until the leading edge is 1 mm high while the trailing edge remains untouched (see cross section in drawing rotorhub).

Take two 2" Aerobalsa rotor blades of 540 mm length. Cover the inner end of the blades with pieces of 0.6 mm plywood as shown in the plan and drill 4 mm holes at the appropiate places. Epoxy small pieces of brass tube (O.D. 4 mm, I.D. 3 mm, length about 7 mm) into the 4 mm holes and sand them down until they are flush with the surface of the plywood. Cut off the inner ends of the blades according to the plan. Paint the blades with filler several times and sand them smooth after each painting. Cover the blades with some elf-sicking film or paint them in bright colors.

Put Nylon screws into the holes of the rotor blades, slip the shims on these screws and stick the screws through the holes in the flapping hinge. Then put the blade holders at the bottom of the flapping hinge and bolt everything together.


For instructions on how to install your RC equipment, read the first two paragraphs of post #9 of this thread, up to the part when I talk about the motor mount. Use some double sided adhesive tape to stick your motor to the mount provisionally, in the position suggested in the plans. Use a piece of velcro to stick the back of the pilot to the support strut and hold the feet in place with a rubber band slung around the front wheel unit. When you've installed everything except the rotor, adjust the hang angle to something like 5 by moving the battery forward or backwards. Now have a look at the video in this thread:
http://www.rcgroups.com/forums/showthread.php?t=656504.
Adjust your motor offset to the right until you've got the prop wash compensated, then drill the appropiate holes, cut off the unneeded parts of the mount and fix your motor.

Now mount the rotor and use a delta mixer in your Tx to control the rotorhead. Set up the throws of your servos to give you a maximum roll motion of the rotor of 8. Do the same for pitch. If your Tx allows this, mix throttle onto the roll signal so that the rotor tilts a further 4 to the right (seen from behind) at full speed. This value is dependent on your motor and prop, you may have to adjust this to your own needs.

Finally read post #12 and have a good time flying the Minimum v4.

Jochen


Edit: Here's the link to a video of the last prototype of the v4:
http://www.rcgroups.com/forums/showthread.php?t=764751
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Old Oct 14, 2008, 11:26 AM
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Help, no one in my town knows what ( gf sheets are? ) or me?
I'm looking to build a head. What else is it called? Or what else can be used instead of this gf?
Thanks DanT
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Old Oct 14, 2008, 11:46 AM
It Wasn't Me!!!!
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Joined Feb 2005
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Quote:
Originally Posted by DanT
Help, no one in my town knows what ( gf sheets are? ) or me?
I'm looking to build a head. What else is it called? Or what else can be used instead of this gf?
Thanks DanT
Dan,
Use the plastic cut from the side of a gallon milk jug.
C-YA RL
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Old Oct 14, 2008, 12:04 PM
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Quote:
Originally Posted by DanT
Help, no one in my town knows what ( gf sheets are? ) or me?
I'm looking to build a head. What else is it called? Or what else can be used instead of this gf?
Thanks DanT
I got mine for my Minimum head from here....
http://www.flugmodellbau.de/index.ph...re-sheets.html
PeterO_UK
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