Revolver Pusher type Autogyro trainer

[Jussi]

A short question: Why the root of autogyro blades is carved off? Does it have some practical function?

Is it just for style? Reducing some weight or for aerodynamics?

Second question: do you aim for zero degrees or some negative for blades before first tests? I do not mean the bottom of blades but the chord line.

[Jussi]

LazerCat haz inspection on my newest project's progress! Controls are ok, cat is onboard - good to go? Ok, we still need the motor and skis. Maybe better blades for this autogyro?

You all seem to have some side offset towards descending blade for the motor. How much do you recommend it sideways? As much as you can get? I plan to print a motor mount according to your experiences.

[Richard Harris]

Jussi,

You need to keep your aerofoil completely flat on the bottom (right up to the leading edge), it helps the blades to spin up. Replicating the aerofoil shown on the plan will give you the best results, if you need some photos or a sketch that can help better explain this then just ask?

If using a standard tractor propeller mounted (so that its leading edge is forwards) then your thrust offset should be to the right (viewed from behind).

It may be my eyes but your rotors look like their rotation is clockwise (when viewed from above), if they are then basic trim settings will be incorrect as the original has anti- clockwise spinning rotors.

Its looking good , even your cat looks impressed!

Rich

[Jussi]

Ok, I understand it makes about zero degrees for pitch if leading edge is sanded to same level with trailing edge. I will use that as a starting point.

Yes, my rotor will rotate clockwise. Then it would be same "aileron" trim but to the other side than yours. Initial aileron trim towards advancing blades on both setups.

[Big T]

That’s going to be interesting, never seen a clockwise model gyro.

[Steve Jones 2]

Simple , Left hand motor offset , right rudder trim and when air side naturally turns right rather than left

Steve

[Jussi]

Why is that? I had to watch my autogyro video again. Both my older gyros seems to have had clockwise rotation. I try to think theoretical and practical reasons, but I think it does not matter. You just tilt the rotor other side for normal straight flight. My blades rotate this way because... well those just rotate this way. Maybe it wants to play in same team with my RC helicopters

[Richard Harris]

Posted by Jussi on 20/01/2021 19:55:02:

Yes, my rotor will rotate clockwise. Then it would be same "aileron" trim but to the other side than yours. Initial aileron trim towards advancing blades on both setups.

Yes, that is correct

I think Steve is describing prop rotation which is something different.

[Jussi]

Ok good to hear Richard. I tried to reply to Big T about the rotation of the rotor. Steve was just faster to reply than I was. Maybe I should use more often Quote -function in my posts. Sorry about the confusion.

About the side offset and Steve's reply: Everyone seem to have it towards downwards going blade. Maybe I just bolt the motor to the side of centerline (some preset distance). It makes the motormount smaller.

[Jussi]

Another Revolver 2 built ready. First baby hops done during taxi tests so basically you could call it ready to fly. Darkness came too early or maybe i went test flying too late. Anyway the Revolver had tendency to roll to advancing blade. Maybe I will add some negative pitch for higher rpm and more trim towards retreating blade. I watched RC Air Adventures videos on youtube. I didn't understand all his explanations but low rpm is bad. In other words too high blade angle is bad or too low disk loading is bad because it results low rpm? My Revolver's all up flying weight is about 1080g. Pitch angle is about zero.

Snow is very forgiving for test flights but I managed to break the deltaplate little. I will make a new one from glass fiber of maybe I will print similar from PETG plastic. In the printed version I could design required pitch angle directly to the center delta plate. Second thing is to build longer nose ski. I should have known better as I fly often in winter time, but small nose ski will drop easily to foot prints on the snow. Cabin is now attached with rubber bands. It will get something better later.

Edited By Jussi on 28/01/2021 15:43:30

Edited By Jussi on 28/01/2021 15:47:51

[Richard Harris]

Jussi,

With your blades turning in a clockwise rotation I would guess you will need a few degrees of right trim.

If you want to give yourself a head start turn on the model and hold it above your head into wind, once the blades are at full RPM you will be able to 'feel' which direction the model is rolling as it goes light in your hands. Simply trim this out until it feels neutral, never do this with the model turned off! When slowing the blades just point them into wind orientating the top of the blades into wind.

I've never heard of a plate being printed before so would be unsure of how brittle it may be? There is no reason why you couldnt drill an extra set of holes in your damaged GF plate, just bring them in on a smaller diameter (say 10-15mm) if you can.

I like the skis! look forward to how you get on, don't forget your video camera

Rich

[Jussi]

Your idea of hand trimming sounds good idea. I flew half battery, which resulted less than perfect landing. The gyro was out of trim so it went too steep turn which I couldn't recover.

Yes, the PLA is brittle especially at cold weather. Luckily delta plate was only damage to the Revolver. Maybe more flexible PETG plastic would be more suitable for this application. I know the 90 degrees spot near blade holder is the weak break point. It should be rounded. On the other hand that is the first place to brake in event of a crash.

Now I'll go back to basics and continue with original glass fiber delta plate. I didn't want to go to our club with CNC machine so I used my manual CNC (knife and ruler) to replicate a new one. Next test flights will be done earlier so visibility is better. I am also waiting for good steady wind for my next test flights. Some right trim is now added and little more movement for next flights. I try to have someone with me for the video.

[Jussi]

It flies ! Couple of test hops near ground which after more flying higher. Trimming more to the right seemed to solve the problem. -11 Celsius temperature, limited flying space and low sun didn't help the problem but steady 6m/s wind was nice.

My Revolver2 felt little bit of pitch sensitive. I noticed some sudden nose ups every now and then. Maybe tail heavy (Hang angle about 16 Degrees nose down) ? Maybe I must fix my servos (Corona CS238MG Metal Gear Servo 4.6kg / 0.14sec / 22g) better to fuselage for eliminating flex. Maybe too low rpm. 0.8mm glass fiber delta plate should be suitable for this model.

 

Edited By Jussi on 03/02/2021 17:38:24

[Richard Harris]

Jussi,

Thanks for posting a video and Well done, it looks cold in Finland!

Your Revolver is very pitch sensitive of which it could be a number of things:

1: Nose weight may need to be added

2: Tip weights to the blades may need to be added dependent on their weight?

3: Your triangular plate mount could be too flexible

4: Your motor could be too high

5: Throttle back a bit, its not a fixed wing

With your nose weight an easy way to find out if it is far enough forwards is to take the model up high and turn off the motor. Your Revolver should descend slightly nose down and move slowly forwards (in zero wind conditions), if it stops in the air then rotates constantly weather cocking back into wind then your CG is to far back.

To test that your motor thrustline is too high get a bit of height and back off the throttle, if it calms down try adding the throttle to see if pushes the nose down. If this is the case move your motor downwards, the closer you can get the motor to the vertical thrustline the better.

Its hard to tell from the video about your blade weights as I cant distinguish the cone angle as it flies by.

The tri plate on the Revolver was tested in many configurations, the best results came from the double plate and a thicker 1.5mm plate. However the double plate was the set up that worked consistently across all prototypes with limited trimming requirements.

I would try one thing at a time and see how it goes?

Rich

[Jussi]

Thank you for the reply Richard,

the idea of trying one thing at the time sounds logical and good approach.

Directly from your answer I notice that my delta plate is most likely too thin. I use just one 0.8mm glass fiber. Not sure but too much flex could cause big cone angle and this could translate to nose up pitch at certain high flying airspeeds? More rigid head might mitigate this problem. Adding tip weights would also keep blades more stable or what is the purpose of tip weights?

Do you mean that you have 1*1.5mm plate or you have 2*1.5mm plate or you have 2*0.8mm glass fiber plates on top of each others? I can produce easily more GF delta plates at my hobby club.

Motor is close to balance point. I made small bend to rear fuselage for lowering the motor. This is most likely ok. Flying speed was a bit high for normal gyro flight. I wasn't sure about flying characteristics so I kept some extra speed. Now after the flights it is trimmed better.

Yes, now it's a little too cold for my taste. Fingers freeze fast and telephone's cameras work strangely. Also the LiPo batteries do not like cold at all. More test flights about the thrust lines and balance points and so on will be done later after it gets little warmer. Now I am happy after my first longer successful test flights.

[Steve Jones 2]

Looking at video and considering my 2 Revolvers which fly well ... I would suggest adding 5g at the tip of the blades and your head plate needs to be stiffer.

my head plate is 1.2mm which is a 0.8mm and a 0.4mm . Not glued just added together

Steve

[Jussi]

Thanks Steve, I'll try the double sandwich thing first.

I took a look of Coolwind instructions second time. It said: "Thickest plate on the top, followed by thinner plate, and the circular anti-strike disk on the bottom."... my bad, I used only 0.8mm with circular bottom plate

After some flying more rigid head I'll experiment with 5g tip weights in order to see effects of each change.

[Steve Jones 2]

Jussi, mine flew with the double plates from the start .. but was sensitive to pitch in flight.. adding the tip weights as only change ..fixed the problem

Steve

[Jussi]

Ok Steve, 5g soldering tin for each blade tip. This is why I love forums: you don't have to research every problem your self. Good to hear you had same problem and the solution was easy. Thank you.

[Richard Harris]

Lets see if this works with just a copy and paste of the URL, if it does our friend from down under will be happy!

 

 

[Jussi]

2nd test flight was today. It was lot of better. Three flights.  It took for a month to get warmer weather. Today it was +5C but wind was 7m/s and gusts 12m/s (14/23 knots), which was not perfet wind for a test flight.

 

Stronger GlassFiber plate was lots of better. It was 0.8mm at bottom and 0.4mm at the top, totalling 1.2mm. Maybe 1.5mm GF triangle would work even better but this was enough good. Steve, I'll try your tip weights later as this flies nicely allready. This flew surprisingly well considering the strong winds at 2nd test flight day. I was able to hover the autogyro today at this wind and landings were 0 meters on snow.

 

There are still things to improve to my Revolver 2. On the ground I realised (after may mechanical trimming) that my elevator trim was working reversed what i wanted. No wonder it was difficult to fly and caused some elevator nodding.  I have flown with futaba about 20 years now and often I still find it difficult to navigate through menus. Now I have Futaba T16SZ. Now elevator trim works normally.  I have to admit, I like the reliability of Futaba but I really hate their user interface. They really lag behind others.

 

I was not happy not to have no nose up at higher speeds. Elevator was remeasured at home. It showed -1 degrees angle to the fuselage line. Elevator is difficult to cut it off, so I build "aerodynamic stability enchancers" AKA trim tabs to the elevator  It can be seen on last picture. "Elevators" can be bent on the ground to get the best results. Elevators are "depron foam" and the hinge is thin aluminium from beer can. Lack of nose up at high speeds should be fixed by the elevator trim tabs. 

Edited March 4, 2021 by Jussi

[Richard Harris]

Jussi,

 

Glad to hear things are improving and that the weather is nice and warm for you to get out and fly  ?

Regarding the head plate thickness, the thicker you go the stiffer the flex will be. In turn  this is likely to push the nose upwards quite a lot so be aware of this.

I'm interested to know how the elevator 'trim tabs' work out? by nature of the beasts all my autogyros tend to nose up with speed.

Looking forward to your next flying video , still no flying in the UK at the moment so it would be very much appreciated by many ?  ?

 

Rich

 

[Jussi]

Today I flew another another three flights. It is getting better and better all the time after mechanical adjustments. Also the control throws (elevator and aileron) are adjusted to my liking. Now it is trimmed for nice slow cruising speed, which looks good and feels good to fly.  I am starting to re learn how to fly autogyros after more flights. Revolver requires little bit different flying technique to the fixed wing models.

 

Trim tabs are good idea. Those were used carefully with only small deflections (3mm up or so). It gave me the results I wanted. Of course correct way is to re align the elevator to correct angle but trim tabs gives you possibility to make small adjustments at the flying site.

 

Basically there is no need to change delta plate thickness. This flyes well now. Maybe in the future I'll experiment more with this thing.

 

It is not the most stable or relaxing plane to fly but sure it is most exciting one to fly! Yes, the skis should be other color than white. Maybe my RC helicopter background helps me with orientation and I was ok with that.  Now i understand why I wanted to fly autogyro after many years. Also the building of Revolver was rewarding for me. It had many great new ideas for me.

[Jussi]

Richard,

 

today was my 4th test flight day. Revolver 2 seems fo fly predictable now.

 

 

Edited March 5, 2021 by Jussi

[Richard Harris]

Jussi,

 

That certainly is predicable! 

I enjoyed that flight, thanks for posting ?

 

Rich