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Old Jun 18, 2015, 02:43 PM
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Success with 3-Channel Autogyro

UPDATE : I have named this cool copter "Otto Jr.".......Hi Gang, I'm happy to report that I'm making progress with my latest RET creation. Several test flights have proven that it flies, and has a slow, soft, and controllable power-off glide. Basically I whipped up a coffin-shaped fuselage with a large, polyhedralled horizontal stabilizer, attached a rotor head and mast similar to Leadfeather's Mr. Twister (I used 4 blades instead of 3), installed my trusty Park 340 /20A ESC/3s1100 and it flew straight off the board. After the first flights, where the prop kept popping off at anything above 1/2 throttle, I changed the battery to a 2s 850mah. It was too hot to test the new setup today, but I will give it a go real soon. I was up @ 75 feet, and at an awkward angle when the prop departed, and the machine righted itself, then settled very gently with some forward speed. I flared nicely, and also was able to steer it well while descending power-off. The rudder/elevator/throttle control has a friendly feel that reminds me of my twin-rotor designs. Specs are: 29" rotor diameter, 27 1/2" long, 12.2 oz (348 g.) RTF, 88 sq.in. total h. stab/elevator area. The combination of this lifty rotor head, and a lighter AUW of the machine (as compared to 15.5 oz. for Mr. Twister), makes for a nice floater. I'll keep you posted on future flights. Video hopefully coming this weekend. Charlie Anderson
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Old Jun 19, 2015, 11:33 AM
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Hi Gang, Well, after 3 more fun flights, I can say that I LOVE this model !!! Very, very satisfying, after 3 decades of chasing the single-rotor, wingless, RET controlled autogyro. It handles left and right turns equally well. The model did need 2 or 3 degrees of right rotor trim to compensate for motor torque. I am also using 60% exponential and dual rates. The control throws needed taming by 50 %. Duration is @ 4 minutes with the 2s 850, with spare power to set up a good landing. Power is sufficient for a reasonable climb-out, but I plan to rework my Park 340 in order to eliminate the prop saver. I want to go back to the 3s 1100. I like power-to-spare. I don't suppose there is any other way to keep the prop on. Perhaps a tighter O-ring would suffice. I have the collet-style spinner that came with the 340. I've been using a GWS 8 x 4.3 black prop. Unfortunately, I have already cut the motor shaft (so it didn't protrude through the firewall). This motor's bell housing seems to have a built-in prop saver. I hope I can simply remove the old shaft, replace it with a new one, then let the excess protrude through the prop saver and mount the collet spinner. I've never used that style spinner before. Do they work well ?? Why don't they just use a nut and washer like the gas engines ?? Will a tighter O-ring work, with the power of the 3s ?? Any suggestions would be appreciated. Thanks !!! Charlie Anderson
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Old Jun 19, 2015, 01:19 PM
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After further review, I see the collet spinner will only fit props with a larger center hub. I have a robust-looking APC 7 x 3.8, and now I see the Eflite Park 340 instructions call for the use of this smaller diameter prop with the 3s batteries. I'll try this smaller prop w/propsaver tomorrow, and see if it still pops off when I rev it up. Charlie PS I found a length of 1/4" wood dowel, and installed it at the leading edge of the horizontal stabilizer. The stab is now much more rigid.
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Old Jun 20, 2015, 11:06 PM
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Hi Gang, I had a good gyro flight today..... but it wasn't with the 3s lipo/7 x 3.8 prop The prop kept departing, even when using a new O-ring and prop saver. So I will enjoy it as is, continue to use the 2s 850/8 x 4.3 combo, and also order a new motor (with the shaft protruding at the front of the motor) . There will be a weight gain from the aluminum collet spinner, but this bird should handle it with no problem. I think I will stick with the 1700 kv/145 watt E-flite Park 340 (at 27 grams)....unless someone can recommend a suitable lightweight replacement. The model's durability was tested today when the prop popped off at 25 feet during a very steep climb-out....it nosed in, at a good clip, and the 3/32" landing gear absorbed all the punishment by bending back slightly WHEW !!! No damage to the 6mm depron fuselage. The rotor blades just folded back, as they were designed to do. The 3 mm depron blades weigh 7 grams each, and the rotor hub (w/brass bushing and hardware) weighs 12 grams. I am amazed at the strength of the 1/32" ply blade spokes. They are working like a charm !!! The new machine handles much like a 3-channel trainer airplane, like the old classic Sig Senior Kadet 3 ch., or the big Telemaster 3 ch. I am getting more comfortable with flying my new gyro, after somewhat of a gyro hiatus. I flew a converted Ace Whizard twin rotor design for years, and this model is the closest thing to it, as far as the "feel" goes. It will be a big help to finally sort out the "popping prop" syndrome. I will try to perform more manuevers as I regain latent gyro flying skills. If I was a bit quicker on the elevator, I may have been able to level the bird a bit better, but....... All's well that ends well !!! Happy Landings !!! Charlie Anderson
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Old Jun 22, 2015, 12:12 PM
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Hi Gang, I am going for the gold !!! , and ordered the latest model Park 370/1360KV motor. It weighs approx. 0.6 oz. more than the 340.....no worries, as the model has plenty of room inside to shift the battery for balancing. While I was at it, I also ordered some APC 8 x 3.8 SF props to fit the spinner. I calculated the rotor disk loading to be just under 3 oz./sq.ft. (assuming 13.5 oz. AUW with new motor, prop, spinner). That sounds like a very good number. Would anyone care to check that math ?? Charlie
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Old Jun 23, 2015, 10:50 AM
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Airfoil Blades

Hi Charlie,

Congratulations on your successful Mr. Twister with longer blades! We played with flat foam blades for a long time, and found we needed lots of motor power to make them work.

Flat blades have lots of drag, and that is why we needed so much power to pull them through the air. Fortunately we developed a simple and easy method of making foam blades with nice Clark Y airfoils that enhanced performance BIG TIME! After flying airfoil blades, we will never go back to flat blades.

Judging from your pictures of your Mr. Twister, I think you could just bolt on the airfoil blades instead of the flat blades. We used the same 1/4" round ply head that Dan developed for Mr. Twister on our first airfoil blade rotor. We even use the carbon rod on the leading edge and the tip weights of .1oz.

I really think you will enjoy airfoil blades. Check out my RCGroups post about them here http://www.rcgroups.com/forums/showthread.php?t=2416605

I am happy to answer any questions you may have.

Cheers!
Russ
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Old Jun 23, 2015, 04:01 PM
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Rubber Band

Charlie,
I forgot to tell you that I have used a single #64 rubber band wrapped around the prop saver screws, and it has held the prop tightly. You must stretch the rubber band and wrap it around several times, but it works well to keep the prop on.

Good Luck,
Russ
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Old Jun 23, 2015, 08:00 PM
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Hi Russ, Thanks for the tips on airfoiled blade construction and prop saver "taming" I hope to have my new Park 370 motor by the weekend. It will be interesting to see what duration the model has, using the new power combo. I have built a control-line autogyro with throttle control, and will be relegating the trusty Park 340 to it. I hope to put the copter through the paces after I've gotten accustomed to flying it again. I've flown helis lately, and it's a different mindset totally. I love slow gyro flight and vertical descents. Charlie
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Old Jun 25, 2015, 04:55 PM
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Hi Gang, Today I received my nice, shiny new E-Flite Park 370 1360kv, and installed it in a jiffy. I had to relocate the ESC, and moved the 3s1100 to the spot just ahead of the rotor shaft. Boy, does this motor run smoothly !!! I have a good feeling about this power combo. It would be great to end up with 6-8 minutes of flight time. If I need more duration, I'll pick up a 3s 1300 or similar. The model now weighs 14.2 oz (403 g.). The weight increase was a bit more than expected, but is still within the recommended range for a 3-D model. Heavier hub prop, heavier spinner, heavier, more powerful battery= heavy duty reliability !!! Rotor loading is now @ 3.09 oz./sq.ft. I hope to be testing this model first thing in the morning. The transmitter is on charge, and I'm charged up, too !!! Charlie
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Old Jun 26, 2015, 10:39 AM
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Good Morning, fellow gyro enthusiasts !!! OK, a couple more flights this (hot !) morning and I'm happy. My Park 370 is working well. The "prop-popping" has been cured, and the climb-out is fantastic with the 3s. It will fly straight and level at slightly less than 1/2 throttle. I increased the control throws to 75% and response is very good. I flew for 4 1/2 minutes each flight. I believe I have a weak 3s and may order a new, larger capacity battery. The label has been marred, and I'm not quite sure if it was a 1000 or an 1100 mah. I would like to get 6-8 minutes duration. I don't want to add too much weight, however. Shall I go to 1300 or 1500 mah lipo, and what kind of duration can be expected ?? Is there a way to calculate expected runtime ?? Any help would be appreciated. Thanks !!! Charlie
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Old Jun 27, 2015, 08:01 PM
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Hi Gang, It looks like a 3s 1600 might do the trick. I ordered one from Grayson Hobby, and it should arrive Monday. The weight of the model has been steadily climbing, and with the new battery in place, I am expecting an AUW of 15.5 oz., which is exactly what this rotor was designed to support. If I lose some "floatability" and I find the descent rate to be intolerable, I will build some longer blades. I can modify the vertical stabilizer and rudder to compensate. I'll head out early in the morning for a couple of flights. The heat and humidity in the Ocala National Forest at this time of the year can be unbearable. I am not very well these days, and a couple flights in that heat is about all I can take. Three years ago, in August, we had a temp. of 99 F., and a heat index of 127 F. !!! I hope you are all having a great weekend....Happy Rotoring !!! Charlie
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Old Jun 28, 2015, 10:03 AM
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Prop size

Hi Charlie, I thought Kyle and I were the only gyronuts crazy enough to fly when the weather is HOT! We routinely go out in 106 degree temps, but here in Arizona we have much lower humidity, at least when the thunderstorms are not around.

One thing we learned from flying autogyros is that they like to fly with larger props. Recently, we took the 9 x 4.7 prop off our 1300 Kv motor that ran on 3 lipos and replaced it with a 10 x 4.7 GWS slow fly prop. Of course to keep from harming the motor we reduced the power supply to 2 lipos of the same size.

The results were very satisfying. The larger prop works better pulling the blades through the air, moving a larger volume of air more slowly, sort of like being in the right gear for hauling the load. The motor and esc temperatures were noticeably cooler, and we got about 30 % longer flight times.

Perhaps this approach could help you get the flight duration you desire?

Cheers!
Russ
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Old Jun 28, 2015, 01:04 PM
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It was a GLITCH! Honestly!
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Nice one Charlie!

I know you have been keen to crack this for many years. video of your efforts in the air?

Rich
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Old Jun 28, 2015, 01:56 PM
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Hi Russ, Hey, thanks for the helpful suggestions. I am rather new to electrics, and I can see there is a lot to take in. It seems a bit paradoxical that a smaller battery would use a larger prop. I'll have to give the larger 2s battery and 10 x 4.7 a try soon. It would be great to keep the bird as light as possible. Rich, thanks for the encouragement. My video girl has flown the coop, but I will see if my neighbor can help. He has a couple of young boys, and they would get a bang out of the whole adventure. I don't know exactly why the 3-channel bug bit me so badly....I suppose it's because I learned to fly on the Carl Goldberg Eaglet 3-ch., (which was a ton of fun), then had experience with other large 3-ch. models. There is a virtue to simplicity.....and it's just great when a plan of your own design comes together Eventually, I did find a use for my thumb when I picked up micro helis a few years back. Since then, I've realized that I get much more pleasure from flying my gyros, so here I am again, and it's fun !!! Charlie
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Old Jun 28, 2015, 04:43 PM
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Charlie...you said it....The main thing is to keep having fun! When we started it was crashes and disappointments, but we learned like you are learning. There seems to be something else to learn all the time with autogyros. Hi Rich, my son Kyle and I have been looking over your shoulder more than you could know, and your work has inspired us. Viewing the video from 2007 when you started out really let us know we were not alone. Thank you so much for sharing and mentoring those of us who are learning!

Watch out Charlie....autogyros are addicting. I have a hanger of 20 or so fixed wing models, and a load of kits yet to be built, but since I discovered autogyros, the other aircraft just sit while I build and fly the gyros.

Oh, and regarding your prop/motor... I read you just bought a new motor, so figured you should just use it with the larger prop and 2 cells. Probably your best solution down the road is to buy a motor with a lower Kv, say 890 or so, run the larger prop, and use 3 cells. The motor you just bought can't handle both the large prop and the higher voltage of 3 cells at the same time.

Anyway...keep enjoying the rotary fun!

Russ
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