Gaui 550 Power Systems General Discussions

[olddutch]

Hi guys....it's been a while since I visited here. I have since replaced the "Rock & Roll" and elevator lever with cnc, made a bunch of corrections with help from a local with the same heli. Yesterday we put it up in the air. No matter what, the tail will not hold. We suspect the speed to be too low. I am running 14-50-29-61. After factoring in the 83% motor efficiency rating that gives me less than 1600 rpm. I just now ordered some other gears and will see if the higher HS will be the answer. (Motor is Z20980). I am going to shoot for a HS of near the 2000 mark.

I'll be away for about a week and after I try it again I'll get back in here and let you know how I made out.

Cheers!.....Rich

[dunkonu23]

Hi Rich,

Nice to see you back!

With your headspeed, I would think you would get the tail bouncing up and down. Tell me, when you get the chance, what exactly is the tail doing to not hold?

Scott

[olddutch]

Hi Scott....The tail does not bounce. It drifts to the left. Tail swings to the right and more or less holds its position as the heli drifts to the left. I did not fly it and this was my observation. Two or three times he stopped and mechanically adjusted the rudder push rod to add tail pitch in the desired direction. Nothing worked. I recall that he varied the gyro sensitivity from 30-80 and we did not notice any changes. On the bench the gyro works quickly and in the correct directions. Our final theory is that the head speed (1500 +) does not provide enough tail rpm. It will be about a week before I can get back to it. In the meantime, if you have any ideas please pass them on to me. Thank you.....Rich

[9sec240]

You said you had a 29 gear. Did you mean 20 for the OWB?

Are you flying it as a 550? What tail blades? Wat gyro?

[Jerrymac]

Just a couple of thoughts Rich. Try changing the 50T main to a 42T to get more head speed. Or, one other thought. Is this happening while just hovering , or during FF ? If it is just during hovering it could be your throttle curve is not giving you enough head speed.

In normal mode I have my throttle curve at 0-40-80-90-100. That gives you a good head speed at lift-off. Some people set it at 0-25-50-75-100 and that does not give you enough head speed when taking off and hovering at just over mid-stick. If you are using a linear throttle curve, try setting it up closer to what I use and see if it helps.

[olddutch]

First of all, my apology for the tipo on the OWG. It is 20. No forward flight yet. Jerry, I like your suggestions. As soon as I receive it, I am going to install a 42t FMG. My throttle curve is 0-45-90-90-90, as set up as my friend. He has spent literally hours fine tuning the set up. Very fussy, very competent. To answer the question about the gyro, it is Gui GU-210.

It will be about a week before my next trial with all of this. Will be in touch then. Meanwhile I am most appreciative of your interest and willingness to be of help....Cheers! ...Rich

[dunkonu23]

Jun 12, 2010 14:29:19 GMT -5 olddutch said:

First of all, my apology for the tipo on the OWG. It is 20. No forward flight yet. Jerry, I like your suggestions. As soon as I receive it, I am going to install a 42t FMG. My throttle curve is 0-45-90-90-90, as set up as my friend. He has spent literally hours fine tuning the set up. Very fussy, very competent. To answer the question about the gyro, it is Gui GU-210.

It will be about a week before my next trial with all of this. Will be in touch then. Meanwhile I am most appreciative of your interest and willingness to be of help....Cheers! ...Rich

I don't know anything about your gyro, but with that in mind, you may want to try this...

One more thing to check... is the gyro operating in heading hold or Normal mode? From your last description it sounds like it's in Rate mode. Rate mode without enough tail pitch will give you the exact thing you describe. What you may want your friend to do is put a small pitch guage on the tail blades and set the pitch at center stick (via the control rod length) to 8 degrees--this will get you into the ball park for pitch. Do the adjustment while in rate mode. Take off in rate mode, observe and adjust out any drift by shortening or lengthing the control rod via the links. Once you get no drift, switch to heading hold mode and fly in that mode.

Additionally, if you're using the frame mounted rudder servo with long control rod (one with the bend in it), you may need to trim about 2mm from each end of the rod in order to get enough adjustment to get that 8 degrees on the tail blades.

This is how I set up my tail on the 550. Works everytime. T

Scott

[9sec240]

The GU-210 gyro is not all that great. It is a pizo style gyro so it is very susceptible to temp changes and vibration. Even in the best case, I always have to use some trim to get the heli to stop drifting. Overall though, it holds the tail OK during flips and rolls.

It did not make a difference if it was set up with the slider centered or rate mode, it would drift.

[dunkonu23]

Good deal, Ivan. I knew I didn't know.

Scott

[olddutch]

As for temp changes affecting the gyro, we were outside for over 4 hrs. working on this. Unseasonably cold (65 deg.). We started out using rate and making changes as you outlined, to add pitch to the tail. This was not measured but we ended up with what must have been at least 8 deg. The pilot switched from rate into HH just to see if it made a difference. Of course it did not. He said he noted some improvement after he put a lot of pitch at mid cntr. in the tail. But little difference. FYI I am using 500 wood, fly bar and paddles are Align 600 and the tail feathers are also Align 600. My local mentor has had his Hurrie 500 for 2 yrs. and is a very good pilot. He has used many combos during this time. He told me that he started out with a HS of around 1900 and had no trouble. That is a far cry from the 1550, or so, that mine was running. When I set this up I did not realize that the Gaui HS chart did not take into consideration the efficiency of the motor which is said to be 83%, for this Z20-980. I am learning......but mostly what I am learning is that I have only scratched the surface of what this is all about. Thanks to you guys, I will learn.......Cheeeers!

[Jerrymac]

Well Rich, the fact that the person helping you out also flies a Hurri should make it easier to get it sorted. Sounds like he has gone over it very well. I think you will find that re-gearing for a higher head speed will help a great deal with the tail problem. I am running 1800 to 1900 on my 550mm bladed Hurri and the tail holds great. Even at that head speed the 550 is very stable and easy to fly.

I have never used the GU-210 so I can't comment on how well it works or any set-up tips. I have used and still do use cheap Telebee piezo type gyros on my smaller helis and they hold fine, although I have to set the gain nearly 3 times higher than I do with the JR G770's that I use on both of my Hurris.

[olddutch]

Today was another frustrating one. Head speed is not over 1800 and the hover was solid. That is....all but the tail holding. Several attempts followed increasing pitch on the tail, changing the gyro gain + - . My friend loaned me a GY 401 and I am going to swap out the gyro with it. I might add, that for one short hover, the gyro in HH did a very nice job. A couple of minutes later in did not hold. So, the gyro is now # 1 suspect. I will keep you posted.

[9sec240]

What do you mean by "not holding"? Is it moving a lot during pitch pumps, flips and rolls or is it just drifting as it is hovering? I was never able to get rid of drift on my GU210s. The only thing you could do was use radio trim to cancel the drift a couple times during the flight.

The GY401 will be incredible compared to the GU-210.

[dunkonu23]

Good luck with the 401, Rich... Like Ivan says, you're going to notice a difference--I have no experience with either gyro, though. I have heard good things about the 401, though.

Scott

[olddutch]

Wild weather has prevented me from trying the 401. Ivan, I appreciate your comments regarding the 210. Wish I had learned of it before I bought it. I could find no negative comments regarding it at the time. What is going on is that in a tail-in hover the tail immediately ( yes it begins on the ground) swings to the right....hard, and stays there. No pumping or oscillation of any kind. It just stubbornly and smoothly points the nose to the left. If you push the rudder over and center the stick, it just goes right back where it wants to go. We have swapped out the rudder servo wheel, shortened the wire in several attempts. I have shipped back the 210 and perhaps it will be replaced. But after reading of your experience I am not looking forward to trying another 210. Then again I don't like wasting my money on junk and this is not helping my attitude towards Guai.
So, I will try my friends 401 to rule out or confirm that the 210 is actually the problem.
I'll be back......Rich

[dunkonu23]

Well, tonight I did my own power system mod... I went from the 50 tooth front main to the 42 tooth front main. With a 14 tooth pinion, 42 front, 20 OWB, and 61 tooth back... at 100 flat, head speed can be over 2600 rpm. I tested it and WOW!! I only flew it for 3 minutes to get a battery check, but I can safely say that it's insane, now. I'll try flipping it tomorrow... right now, it's dark and stormy..

Scott

[Jerrymac]

Rich, I haven't used either of those gyros myself, but the 401 seems to have been a long time favorite for many people. I am using JR gyros on my Hurri 425 and 550.

Just a thought, but how far out is the ball on your tail servo arm from center? On my 550 it seems to work the best at about 13mm out from the center. Oddly enough, on my 425 with the same gyro it seems to work better at 10mm out, although it has a different tail servo.

Scott, that sounds like some pretty insane head speed running 550mm blades. I was thinking around 2300 to 2400 on my new "500" build would probably be more than I really need. I do think I will bump the head speed up a little on my 550 now that I am getting better at flying it. Only running about 1800 to 1900 now, and might go to around 2100 with some gear changes.

[dunkonu23]

Rich, just to chime in... Spartan gyros here.

Jerry... I would think 24-26 would be right in the wheelhouse for a 500. I'm going to set my Velocity for 1700/1900/2050 via governor, so I think you could pull a lot more headspeed on your 550, bro! I do appreciate exactly what you've done with your 550, though.

Scott

[Jerrymac]

Jun 19, 2010 8:40:50 GMT -5 dunkonu23 said:

Rich, just to chime in... Spartan gyros here.

Jerry... I would think 24-26 would be right in the wheelhouse for a 500. I'm going to set my Velocity for 1700/1900/2050 via governor, so I think you could pull a lot more headspeed on your 550, bro! I do appreciate exactly what you've done with your 550, though.

Scott

Yeah Scott, I know I could safely run a higher head speed on the 550, but, my concern was the pilot was not good enough.

Now that I have been flying it more, and feel more comfortable with it I will bump it up a little at a time and see how well I can fly it. Even with the lower head speed I am running, it flys pretty fast.

Surprising how much difference blade size makes. I feel real comfortable flying the 425 with a head speed of around 3000, but it is a completely different flying heli than the 550. I think I am going to increase the pitch range on the 425 as full collective punch-outs are a little mushy right now with only 10 degrees. The motor does not bog at all so I think I will take it up to 12 or 13 degrees and see how it flys.

Even with the lower head speed on the 550 it climbs much faster than the 425, but I have + - 13 degrees pitch on it.

[9sec240]

Wow Jerry.. 3K on your 425!! That is COOKING!! I am surprised that it is not a rocket ship on collective even with only 10°

BTW, I got the blade spacers yesterday and installed them. I would have posted yesterday but my power was out from 4PM till about 1 PM today!!