Tailess, two rotor, electric Gyro

[mnowell129]

Here's a discussion starter in response to urmk...
This is my recent creation. G3PO.
You can find videos at
http://www.mickeynowell.com/id9.html

There are in-flight still pictures at
http://www.megapixphotography.com/Default.aspx?cat=Aviation&subcat=RC%20Electric

This model is 12.5 ounces, 30 inch rotor span, two blades, no horizontal tail surfaces at all. Takeoff or handlaunch. Flies slow or fast.
I can hover in 5 mph winds.
Intentional dead stick landings are no problem...
$40 of GWS dragonfly parts, the rest is scrap bin.
Takes about 75 watts to fly.

[JWarren]

Pretty cool looking bird! Looks like a nice starter project for newbies!

John

[umrk]

Original therad telling about its design stages and versions here...
http://www.rcuniverse.com/forum/My_electric_autogyro_flies%21/m_2325673/tm.htm

What are the pros and cons of using the Dragonlfy head parts?
How many degrees of movement do they allow?
How manuverable is it?
Is the flybar necessary?
Your flight impressions?

IIRC this is version 3 in your development stages using that head, any other mods that your considering implementing?

Thanks
mike
(if thats not enough Qs, I'll probably think of more after I get woke up. ;)

[dougmontgomery]

Nice work, I sure would like one of those, Take all the work out of getting mine to fly, Oh yea thats alot of the fun. Good job and let us know any improvements on a final. any way you could post some part #'s to this thread for those dragonfly parts? Doug

[mnowell129]

The parts list for dragonfly parts is on the rcuniverse thread already mentioned.
The advantage to the dragonfly parts is
1) they are cheap, total of $40 including shipping.
2) You can use tiny servos, this gyro is 12.5 (now 14 ounces with
repairs)
3) Incredible control, if you watch the video you can see
me make slow circuits in my street including turns of
street diameter.
4) dead stick landings are very doable.

All three versions had the same motor/mast head arrangement, only
differing in landing gear placement and tail length to improve the ground
handling and rudder control. This layout is pretty good because it does
just about everything I want.
I am trying to rebuild it over this weekend so it's not mostly glue and
I can draw the parts for others to build. There are only a few
critical bits to align, otherwise its pretty robust.
When I get drawings i'll post with instructions on how to build. Ground handling is typical, but I can takeoff in my street. Once in the air you can
tool around without much incident.

Gotta take of some business, will address the flybar issue later this evening....

[umrk]

Thanks Micky!

I couldn't get the videos to play so I downloaded them and they worked fine, probably my computers setup. It looks good in the air, and rather manuverable. I'll definately be looking for the plans and instructions to be posted.

mike

[mnowell129]

Yea, the best thing to do with the videos is download them.
Will have a drawing ready soon, there's not much to it,
just getting a few angles right.
It is very fun to fly, especially when its calm.
I can fly back forth down the street and make nice
rudder turns in the street, all at about head high.
In any kind of breeze you can hover.
I have a new one almost built, will put design up when
I fly it to confirm the construction.

[Kwok_Yu]

Micky,
Very nice autogyro. Do you fly rc helis also? I bet you this would also make a nice trainer for heli forward flight. This occurred to me because I gave up my gas heli before I could do forward flight.

[mnowell129]

Yes I am a heli flyer. The heli experience helps, but not as much
as you might think. This gyro flies very well when you use lots of
rudder to turn and very little roll control, mostly just to stay level
and help initiate and roll out of turns. You use a little back
elevator in turns, altitude control is mostly power.

[mnowell129]

[QUOTE=umrk]Original therad telling about its design stages and versions here...
http://www.rcuniverse.com/forum/My_electric_autogyro_flies%21/m_2325673/tm.htm

What are the pros and cons of using the Dragonlfy head parts?
How many degrees of movement do they allow?
How manuverable is it?
Is the flybar necessary?
QUOTE]
The flybar is the 64 millon dollar question, my answer will likely instill the wrath of some readers, but here it goes anyway.
The flybar is necessary with this model and this set of blades.
Rotorcraft obey certain physics. One of the overlooked ones in model gyro
copters is a property called "following rate". This is how fast the rotor system
follows the control input.
Following rates need to fall in between 1/4 second and 2 seconds for a
human being to be able to control a rotor craft. I'm not making this up,
I'm paraphrasing from a reference I'll gladly provide later if someone wants it..
Two bladed teetering rotors, even full sized ones have a very high following rate and are generally considered unstable. The bell 47, invented by
Art Young had a stabilizer rotor to make it flyable by humans, all bells that followed had this bar until the control systems were augmented with electronics to get rid of the flybar and its additional drag.
There are few exceptions , the R22 and the Bensen gyrocopters. By careful design, weighted blades, etc. The control response on these aircraft have been tailored to humans. These are unique design points due to the size of the craft, rotor mass and rotor rpm.
Following rate is increased when the blades get lighter or move faster. Thus model sized rotors have really high response rates. This fact nagged model helicopter designers for years until it was understood. The model heli solution is the flybar, which virtually all model helis have. There are a few model heli's that have gone flybarless, Hubert Bitner's Horizon is one example. To make it flyable it had LOTS of tip weight and it was still twitchy to fly.
Three and four bladed model rotors become too responsive, where 3 and 4 bladed full size craft are flyable. It is similar to the fact that you can balance a broomstick in the palm of your hand, but not a scale model of broomstick made with a #2 pencil.
To make model rotorcraft flyable, the too high response has to be tamed somehow.
The solutions thus far have involved wings, large horizontal tails, tall rotor masts, low centers of gravity, delta three hinging, and other techniques.
I simply applied accepted model heli theory, used a flybar and made my rotor stable. Thus I don't need any other dampening to make my craft flyable. Even though the takeoffs are still kind of challenging I will let anyone with demonstrable 4 channel airplane skill fly mine, it is pretty easy to fly.
Just show up at my field. Jim from lakeland has already done so.
Note that I recently got to fly an electric spin doctor. It was a little easier to fly than mine, but much lower in performance, and took much more power to fly. Don't take me wrong, I understand the appeal of the simple heads and tilting shaft models, i thought a long time (10 years) about how to get the stability in one of those systems. But it isn't worth it to me. I have positive control at all airspeeds, don't need big servos, can dead stick land almost straight down and fly figure 8's in front of my house in the street. The flybar is not that big a deal to me. Flybars were a big deal at first with model heli's. They are a non issue nowdays...
Anyhow, thats the giant answer to the flybar question. Sorry for the longwinded answer......I hope it was a helpful answer..

[umrk]

Very helpful, Thanks.

So as I suspected this would probably be a better second gyro for someone with limited experience, and rather manuverable. I'm wanting to build one but will probably build a PT Gyro first to get familiarized with Gyros, then move on to this one, which sounds more like what I'm after.

mike

[umrk]

Parts list for the head...
Post #48
http://www.rcuniverse.com/forum/m_2325673/mpage_2/key_/tm.htm#

[mnowell129]

The PT gyro appears to have a direct control head. These two gyros will fly similarly, so I think they are the same second step. Step one is probably something like a gyrace or spin doctor. My experience with the spin doctor (flying model magazine plans) is with my flying buddy down the street who built the rotors/wing and put them on a slo stick. This kind of layout is easy for the beginner it seems...

As to the PT Gyro, and the direct control gyros in general. So called "direct control" heads are actually using cyclic pitch, the same as a helicopter, the same as my gyro. The designer of the DC head that most modelers use was Emilio Cabezis(sorry if I spelled your name wrong Emilio). We talked about this at some length many years ago and agreed upon the term "shaft tilt cyclic pitch" as being an accurate description of the tilting head direct control.
The gyroscopic forces are really to high to actually directly tilt the rotor head, you have to make it precess in the right direction with cyclic.
If interested i can make a sketch of how this is cyclic pitch.
While simple to build this kind of control has some issues to overcome, the largest is the high control forces feed into the servos. I've heard some modelers suggest 120 ounce inch servos with metal gears.
Here is where I think there is some confusion, the large forces are not due to the tilting of the rotor they are due to the blades trying to pull themselves flat with what is called an offset flapping hinge during the transition part of a tilting head control input. This produces a large force in the servo every 1/2 revolution until the head is realigned with the rotor shaft.
Anyhow, blah blah blah... let me know if any of these topics create interest that you want to dive into some more....
mick

[mnowell129]

I have built another version of my gyro.
Video from today at
http://www.mickeynowell.com
Then click "HobbyWorld".
The first .jpg plans for this model and more details at
http://www.rcuniverse.com/forum/How_to_build_G3PO/m_2380064/tm.htm

[dougmontgomery]

Hey Mickey, I'm going to start getting parts. Could you post the Rotor blade width and length, with an outline of the airfoil. I seen the side shot but a scale one would be good, even if you trace it. D.

[mnowell129]

The blades are 14" by 1-3/4" inches.
Heres a picture of the airfoil in the calipers for reference.

[JWarren]

I see you are using the Clark Y. Have you used any of the blades from Aerobalsa? Thats what I am using. If you have, have you noticed any differences?

John

[mnowell129]

Yes I've used the 2" and 1.5". The 1.5" work better than the 2 in my application. The aerobalsa blades are very well made but I don't think the particular airfoil is critical. What seems to be important is the aspect ratio of the blades and the quality of the finish. The aerobalsa blades are easy to get a good finish on and are well made. I will continue to use them, rather than build my own except in circumstances where they don't have a size that fits what i'm working on.
I don't have an apples to apples comparison because when I put the aerobalsa blades on I increased the span and decreased the chord at the same time. However I am flying those blades still and they fly very well. I will make a good comparison when I make some homemade blades of the same dimensions. I'll put a post here when I do that.
mickey

[JWarren]

What type finish do you use for your blades?

[mnowell129]

1 coat of spray clear laquer sanded out, then a second coat
of the same. Then monokote trim sheet applied helicopter style.
That is start at the te on the bottom then wrapped over te over the top,
around the le and back to the TE.
Leaving town today, will be back sunday, will check here then.
mickey

[dougmontgomery]

Hey Mickey, Had a blade Strike on Green G3P0 and need to build my own first set. I will try to repair and Balance to the other one.

I will be ordering some of the Aerobalsa blades and would like to know the process to make them as nice as yours. Doug

[mnowell129]

Here goes.
First don't try to match the other blade. I made it by cutting down a 2" blade so the 1.5" won't match it. Make two 1.5".

1) Cut to length
2) Sand the sharp leading edge to a nice round contour, between 1/16" and 3/32" inch.
3) Sand blades overall with 220 grit.
4) Use a dremel with a cutter ball (3/32") and some kind of guide, cut a groove for the lead 1" in from the tip, 4" long, 1/8" back from the leading edge. (pic)
5) Cut two pieces of 1/16" solder and roll straight.
6) Embed the weight in the groove with thick CA.
7) Carefully sand the CA back to airfoil shape. (pic)
8) Sand the top of the root flat for the blade reinforcements. The flat ends up being 5/8" by 1-1/2". The flat is centered over the hardwood/balsa join line. When viewed from the end the top and bottom surface should be parallel.(pic)
9) Make 4 pieces of 1/32" ply, 5/8" by 1-1/2". Glue the top ones on centered of the join line.
10) Glue the bottom ply pieces lined up with the top ones.
11) In a drill press drill the 3 mm holes. They are 1/4" and 1" in from the end, 1/2" back from the leading edge.
12) Taper the trailing edge at the root at an angle so that the blades are the full chord width at the outboard end of the ply reinforcements.
13) Soak some thin CA along the trailing edge (last 1/8" inch)
14) Final sand carefully.
15) Spray with instant dry clear laquer.
16) Sand with 320
17) Spray again
18) Sand again.
19) Weigh the blades, add spray to the lighter blade until they are within .1 gram.
20) Make a very light spray coat, don't sand.
21) Tack rag the blades.
22) Take monokote trim sheet cut to the blade length minus the length of the ply root pieces.
23) Take off the backing on the trim, lay on a flat surface.
24) Put the blade trailing edge down on the trim sheet, with the bottom of the blade facing you, 3/16" in from the edge of the trim sheet closest to you.
25) Lower the blade towards you, you will now have the blade flat on the table with the bottom trailing edge stuck to the edge of the trim sheet, and most of the trim sheet behind the trailing edge.
26) Pick the whole mess up and make sure the monokote is pulled snug and stuck down on the TE.
27) Roll the trim around the trailing edge, leave no bubbles.
28) Continue to stick the trim sheet down by holding it up in the air and running your finger back and forth down the blade, sticking the trim down from TE to LE.
29) Roll the covering around the TE, make sure to not leave any bubbles.
30) Use the same procedure to stick the trim down all the way to the TE, overlapping where you started.
31) Use a very sharp new blade and trim the covering flush with the TE.
32) Make sure the covering is stuck down everywhere, especially at the TE.
33) Put thin CA on the tip and the root so the covering stays stuck.
34) Reweigh the blades, use scotch tape on the leading edge of the light blade at mid span until they weight the same.
35) Done, go fly.

[dougmontgomery]

Mickey, Well I went down again from about 5 feet up. Rotor blades folded up and it broke my tailboom where I had It Sleeved. I think I will be rebuilding a fresh uncrashed version that has all the correct angles in the frame. Put a lighter tailboom, the one the plans call for. Re-trim and fly. Will start this Weekend. Your post really should get more attention!!!!Doug

[mnowell129]

Mickey, Well I went down again from about 5 feet up. Rotor blades folded up and it broke my tailboom where I had It Sleeved. I think I will be rebuilding a fresh uncrashed version that has all the correct angles in the frame. Put a lighter tailboom, the one the plans call for. Re-trim and fly. Will start this Weekend. Your post really should get more attention!!!!Doug
Sorry to hear of your crash. A new one always flies better anyway.
The Good news is that after 5 of these things I can build one in an evening.
Don't really understand what you mean about the post getting more attention...
BTW I'm lining up manufacturing for my stuff...

[dougmontgomery]

Mickey, When Do you anticipate to having the parts available to the Public?
What will the manufactured parts consist of? Doug

[mnowell129]

Mickey, When Do you anticipate to having the parts available to the Public?
What will the manufactured parts consist of? Doug
I'm talking to laser cutters now.
I'm also open to suggestion.
Here's my current thinking.
The heli parts are off the shelf so do I re-package them, maybe since there are variations in brands. However I've got to mark them up to handle them. The lowest cost to the end user is to include a purchase list with exact part numbers.
The fuselage is pretty simple, I guess I could cut the couple sticks needed.
I can have the rudder/fin laser cut.
The tail parts are mostly off the shelf stuff except the fin mount.
Here's what I see the hard bits to be:
1) Metal blade straps, I'm working on making these.
2) Wood parts
3) Landing gear wires, two axles and tail wheel wire.
4) Anti-rotation link, but I've got that down to two pieces of carbon fiber and a piece of 1/32 ply.
5) The blades.

The blades are the big issue for most non helicopter flyers. But they are pretty easy for people who have built helis.

My current thinking is a kit that includes :
Blade blanks, trimmed to length, routed for weight, blade roots glued on and holes pre-drilled. Blade covering. Blade weight.
Metal blade straps.
Wood parts
Anti-rotation hardware.
Landing gear wires.
Rudder and fin.
Rudder horn.
Precut tail boom, and tail brace.
Precut main landing gear.
Wheel collars drilled out to 3mm for main shaft.
Tail wheel, and hardware.
3mm bolts and plastic stop nuts for blade straps and head.
Head stiffener.
1mm pin for the head.
Instructions

Videos on CD on building/flying ( in my street of course!)

As an option I may offer built, balanced blades, but I'll have to figure out what that would cost.

The buyer supplies the motor/radio/ESC, etc.
Head parts.
Main wheels and wheel collars.
The builder would have to build up the chassis, rig the servos, motor etc.
Build the head, weight, finish and balance the blades.

What do you think?

[dougmontgomery]

I think there are two kinds of sales here:

(ARF)I know 15 to 20 flyers and they would prefer to just get out the credit card and not have to shop around for anything but normal radio gear,servos,motor set-up prefered for airplanes have everything assembled except main gear for packaging issues/price
or:
Offer a basic kit, that contained the Carbon Fiber, 3/8" stock cut to length, axle mount, vertical fin, rotor blanks/straps/lead with plans and video for the "like to build generation"
a kit with everything needed except radio gear and servos and motor set-up.

My concerns would be that if it build their own doesn't get set-up right that you will be answering tons of questions . People want sucess right out of the box, crashes hurt pocket books, sucess of the product.

I tried kitting a profile foamy and man it was a lot of work, then I didn't have the time to do what I love to do, Design new. Production is long and drawn out, boring, repetitive.(need I say more.)

You have a really neat product and If it could be produced by someone other then yourself, the profit margin wouldn't be there but at least you could keep using your brilliance to figure all those other ideas out. Put a poll here in the groups for the G3PO and see How it hits, then make 3 kits for that Autogyro fly-in coming your way. I am guessing about 135.00 for labor and parts/plans all in raw form, Shipped.(Basic kit)
For the (ARF) add your labor cost,(hard to sell at that price unless someone else sets up a production line to put together.)

[mnowell129]

You are almost right on the money. Spreadsheet says around $140 including shipping for a complete kit of raw materials including head pieces.
How do you do a poll to figure out if there is any interest at this price level?
mickey

[dougmontgomery]

Mickey, You will have to start a new thread on the "Manufactured G3p0-Kits, parts:anybody interested?" On the very bottom under manage attachments there is a poll box.

I really appreciate all the work you put into this and stay focused. (Build and they will come.) With the uproar of the E-rc, people seem to want to have different flying aircraft, and the Challenges that make them fly. Even if they are self induced. Doug

[mnowell129]

Thanks for the encouragement.