Gaui 550 Power Systems General Discussions

[olddutch]

Jerry, I believe that the original stock motor is 800 KV. Not sure if one could get the needed HS out of it for the 425. As you mentioned, the 425 needs faster HS. What really got my attention real fast, was your comments regarding handling between the two sizes. It was enough for me to decide to go to the 500 or 550 size right away. I see that for each (500 or 550) there is a conversion available, depending upon what blade length you want. So which size do you recommend ? I believe that I'll get the Z20A980 regardless........Rich

[Jerrymac]

Rich, I am still using the stock Gaui 850kv motor in my 550 and it works fine for my flying skills. In my 425 I am using a Z20-1470kv motor.

I have never flown the 500mm blades so I really can't comment on how the heli flys with them. You can still install the long boom with 575XL belt and run either 500mm or 550mm blades.

If you want my opinion, (and remember it is just my own opinion ) , if you already decided to go with the Z20-980kv motor I would suggest just going with the long boom and 550mm blades. You could still run 500mm blades with that set-up if you want to.

With a head speed of around 1900 and running 550mm blades my long boom Hurri is very stable and easy to fly. It just kind of sits there in a hover waiting for you to tell it what to do. It will fly extremely fast if I want it too, but also will just float around like a hot air balloon if I want it to too.

I am certainly not trying to tell you how to build your heli, but, just trying my best to answer your questions based on my own experience with the Gaui 425/550's.

Jerry

[olddutch]

Jerry, I am grateful for your advice. Somehow I got the impression that the 550 blades would be too much for the 850KV motor. However I am impressed with what you are flying and that sounds like what I really want to do. Also, I went into my Phoenix sim and set the govenor on the 550 to max at 1600rpm with the 550 blades. Voila....it flys just fine. So that is just the way that I am going to set up mine. Gearing to be 14-20-50-61 unless you say otherwise, but that is how I came up with the 1600rpm. Should I use a straight 90 pitch curve or what? Now I am getting excited about this as I have finally made some firm dedisions. Thanx much...Rich

[dunkonu23]

Rich,

I'll chime in here if you don't mind. 1600 may be a bit low, on the sim it will be fine. I don't recall if they have damping settings for the 550 on Phoenix, but just in case... when you're flying yours look for things like tail bounce--that's your indicator of one of two things: Blade RPM too low or damping too hard. Damping is adjustable on the Gaui based on the orientation of the washers on the bolt holding the grip to the feathering shaft. You'll probably not have to worry, but I needed to mention it when I saw your headspeed.

90 flat on the idle 1 or 2 curve is fine, it'll get you close if not spot on to 1600 rpm. I checked with the headspeed calculator on the Gaui site:

www.gaui.com.tw/html-en/550_rotor_speed.html

Enjoy! It's an exciting hobby!

Scott

[olddutch]

Thanks Scott. In calculating HS I used 800KV as that is given on several web sites. However, I also see it as 850KV. At 850 the HS is over 1700, so that would be good. I haven't noticed any tail bounce on the sim, but of course it's only a sim. I'll be watching for this when I get to flying. Your comments are well taken. Thank you.......Rich

[dunkonu23]

You're welcome, Rich! I'm looking forward to your finished build and your impressions after your first flight!

Scott

[Jerrymac]

May 10, 2010 10:57:11 GMT -5 dunkonu23 said:

You're welcome, Rich! I'm looking forward to your finished build and your impressions after your first flight!

Scott

Yeah, me too. And feel free to start your own thread, that way we can follow along better and try to help out if you run into any problems.

Good luck with the build.

[olddutch]

Well guys, I pulled the trigger a bunch of times today and have things ordered. I ordered the basic 425 kit, Z20A980 motor, Hobby Wings 60A spd. control, Hyperion D20GMD tail servo, Gu-210 gyro, conversion kit to 550 size, a full head CNC unit, CNC blade balancer, and misc. parts to handle a few dumps, battery packs, a couple of bearings for set up, and maybe a couple other things. Believe me it was not easy to find all of this in stock. Many suppliers are out of stock on nearly everything for the 550. This stuff is coming from 7 different locations, plus my local shop. I owe each of you thanks for steering me to the distributors that I ordered from. You have been so very helpful. Now it will be awhile before I receive all of this, and then the fun begins! So it won't be anytime real soon that I will have any flying report. Maybe you will hear from me as I due the assembly. Thanks so much!!....Rich

[dunkonu23]

Wow! You're pimpin' out that bird, Rich! Way to go on all the CNC stuff. While you're in a buying mood, consider the CNC Antirotation bracket. For some reason, I never trusted just the elevator arm, alone.

Building is so much fun! This kit goes together really well, so enjoy! Keep us posted on progress. As always, if you have any problems, let us know and we'll do our best to help.

Scott

[olddutch]

Scott, the cnc anti rotate brac is included with the complete head deal. $ 159 at Flying Hobbies. It is a Gaui item, not an off brand. I may have over spent a bit, but I have seen plastic head pieces bust up rather easily so I thought I'd be better off in the long run to buy better quality right off. Another benefit may be that the head assembly will work smoother. Also, I considered the safety aspect, with particular attention to the grips and elevator brac. I have seen this same package priced much higher. I'll be back........Rich

[dunkonu23]

Now that I think back, you're right.. it does come with the CNC Antirotation bracket. If I recall correctly, mine didn't come with screws to attach it to the frame. I remember buying the bracket separately and got screws with that before I got the head assembly. Go figure.

Just don't be like me and forget what you've ordered... I've got boxed that I've never opened... when they come in, I write what's supposed to be inside on the boxes..."tail blades"... "Charger"... "Booms"... "Grips"... my wife has designated a corner for my unopened stuff. But, I digress...

Safety is important. I'm all about it. After getting caught up in a spooled up helicopter, it's no fun. Flybars hurt.

Scott

[Jerrymac]

Rich, looks like you will have a well built Hurri when you are done. One thing I didn't notice in your shopping list was blades. You didn't forget the blades did you? If you are looking for some nice inexpensive 550mm blades for starting out with, the Pro 3D's at HeliDirect work pretty well. I have both the FRP and the CF ones and I am pretty happy with them for the price. They even balanced almost perfectly right out of the package.

www.helidirect.com/main-rotor-blades-pro-best-value-c-1_117_120_785.hdx

[olddutch]

You wouldn't believe how hard a time I had finding 550 blades. I wanted woodies to start off with. Like most other parts, they were out of stock. Finally found some at All e rc, so I ordered 2 pr. Earlier I forgot to mention that among the cnc stuff I ordered a cnc tail gear and shaft. Hadn't planned on it but saw it on cnchobbies.com. A dealer told me that all rc stuff is in short supply. It seems as though distributors have not been ordering in quantity and the Chinese won't ship partial containers. So until business picks up there will continue to be shortages. If you think you may need something, I would suggest trying to find it now. Incidentally, in my search I found that the source listing the best variety of parts for the Gaui is Flying Hobby. Prices are competitive too. But their inventory is thin at this time also. Shipping is from Hong Kong and you can choose between two ways. Too bad All e rc doesn't have more inventory for us, as he was the best to deal with. Great pricing and he shipped 2 hrs. after I ordered. Thanks for the tip on blades, Jerry.

[olddutch]

A little note here regarding vendor service. Today I received complete shipments from both Dumb Thumbs and All e RC. I am impressed as this was exactly 48 hrs. from order to receipt. All e RC shipped N/C and Dumb Thumbs $4.99. Each of them shipped Prioriy mail. I am impressed.

[9sec240]

Two orders recently with impressive shipping from each. I ordered from HeliDirect on Sunday and received my order Wednesday morning. Not too bad from Mass to Chicago. The other order was from Infinity Hobby. I placed the order on Sunday and it arrived this morning (Thursday). Four days from CHINA!!

On the power system front, I just swapped out my 50T front gear for a 60T and changed the one way from 19T to 20T. I am trying to bring the head speed down a bit. Set up with 11° of pitch and 8° cyclic, it flipped and rolled FAST. I actually turned the swash mix down to slow the flips and rolls. I wanted to also install a 14T pinion but Infinity was out of stock. Head speed is too slow now. I turned the swash back up but flips and rolls are not quick enough. That 14T pinion is exactly what I need. It should split the difference between the two.

Align 500L 1600kv motor
Align 60A ESC
13T pinion
60T front main
20T one way
61T rear main

Head speed calculator says the original head speed was 2733 and new head speed is 2397. The 14T pinion says 2582

[Jerrymac]

No wonder my head speed seems scary fast. My set-up is;

Z20-1470kv
15T pinion
50T main
20T OWG
61T rear

At 95% motor efficiency, that puts it at 3049 according to the head speed calculator I use. Guess I should put the 14T back on mine again.

[dunkonu23]

May 13, 2010 21:31:09 GMT -5 9sec240 said:

Two orders recently with impressive shipping from each. I ordered from HeliDirect on Sunday and received my order Wednesday morning. Not too bad from Mass to Chicago. The other order was from Infinity Hobby. I placed the order on Sunday and it arrived this morning (Thursday). Four days from CHINA!!

On the power system front, I just swapped out my 50T front gear for a 60T and changed the one way from 19T to 20T. I am trying to bring the head speed down a bit. Set up with 11° of pitch and 8° cyclic, it flipped and rolled FAST. I actually turned the swash mix down to slow the flips and rolls. I wanted to also install a 14T pinion but Infinity was out of stock. Head speed is too slow now. I turned the swash back up but flips and rolls are not quick enough. That 14T pinion is exactly what I need. It should split the difference between the two.

Align 500L 1600kv motor
Align 60A ESC
13T pinion
60T front main
20T one way
61T rear main

Head speed calculator says the original head speed was 2733 and new head speed is 2397. The 14T pinion says 2582

On the pinion, did you try that Japanese site? Seriously, man... they're quick.

On the headspeed... my T-Rex 500 is 2950, so I think the Gaui can take what you give it. 23xx is too slow for your flying style. I dunno, I'd be tempted to go for 27xx.

Scott

Scott

[olddutch]

I have completed assembly of the Hurrie and I enjoyed it. I installed the Z20 980 to give me a head speed of what the Gaui chart says will be 1854 rpm. I thought that to be good for the "ol man". But I did not consider the 83% rating of the motor. If that is a deduction from the published 1854, then I will be down under 1600. Probably not good. I just spoke with a very experienced heli guy, and he told me that I must have around 2400 rpm to get effective tail action. I did not want to hear that because that would mean changing gears. Also, on the Phoenix Sim I have been flying with a governed speed of 1800 and it flys just fine. I have noted a very slight amount of tail wag at hover as I am powering down to land. Now the question is, just how close is the Sim to the real thing. I am looking for a tame cat here to start out with, but I know that one must have good tail conrol. So now I am confused. Can you give me some input on this. Has anyone experienced lack of tail control with the low H.S. I mentioned? Your response would be very much appreciated. Thank you.......Rich

[Jerrymac]

Well Rich, first of all, you certainly don't need a head speed of 2400 when running 550 mm blades. In fact, that might be at the top end of what anybody would want to run with 550's. My head speed on my Hurri 550 is around 1800 to 1900 and it flys well enough for my flying skills. Even at that head speed, it is pretty fast.

Secondly, consider that a fully charged 6s lipo ( or 2x3s ) is 25.2 volts when fully charged so the head speed will be higher than the calculated speed at 22.2 volts. Mine is usually around 22.5 volts when I land, although it will be lower in flight do to the motor draw.

If the tail doesn't hold well you could use larger tail blades like 92mm but I think it will be fine. A little tail wag at hover tells me that it is holding ok. If it drifts a lot, then you have a problem.

BTW, just wondering if the experienced heli guy you spoke with had any experience with the Hurricane 550? Different helicopters fly differently. My head speed on my Hurri 425 is 3000rpm, but I would never think of running that on my 550.

Oh yeah, maybe Scott can answer your question about the sim as he is using Phoenix too.

[dunkonu23]

Rich,

Here's something to think about when someone tells you a specific head speed is needed to hold the tail: Autorotation. Simply put, head speed will usually fall rather quickly once negative collective is removed, yet the tail still holds. Granted, the main reason for a tail rotor is to counter torque, but still even on spool up, once set, the tail holds. So, I think the experienced heli guy is incorrect. So, just a countering thought.

On Phoenix, I set pitches and headspeed equal to what I fly. I set disc size so that it is EXACTLY what I have in real life which includes the grips. Same thing for the tail rotor. In fact I actually meaure the disc size, then input it. Once that's done, I trim the helicopter so it feels like mine, then fly. It's pretty close. It's not perfect, but I've been told properly setup simulator models fly very much like a flybarless helicopter with a Flight Control System.

I hope this helps,

Scott