HobbyPartz GY48v


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GY48V GYRO Review

Who does not like inexpensive electronics that perform above your expectations? Well, the GY48V Heading Hold Gyro  sold by Xheli, Hobbypartz might just do that for you. It sure did for me!  I"ve purchased, tested and flown quite a number of inexpensive gyros in the past 2 years of my switch from Nitro to Electric flight.  At under $20, this Piezo sensored gyro sure fits the bill.  With a hard Aluminum case designed to withstand most crashes, this gyro came ready to mount (I did not have to mod it like a G401B gyro needed).  Only using 2 layers of foam tape, I mounted this gyro to my EXI 450 SE Carbon helicopter after pulling the G401B gyro off of it, I followed my normal method of gyro installation and setup (read further down the page) and I was off and flying.  I was able to get the same holding I did with the G401B at 40% gain setting (I use the gear channel method and not gyro sense).  But with this gyro, I was able to crank up the gain to over 90% with no wag or unwanted bounce until I hit around 100%.  My tests flights, I flew at 75% gain. It Held above average in punch outs, flips and backwards flight.  I did not have any expectations that this would meet or exceed my GP750, GY401 or GY520 gyros in my other helicopters but it came darn close in many flight charactoristics. I would charactorize myself as an advanced flyer.  It held my 450 Tail through everything I did.  The Piro stops were snappy and the piro rates were consistant and smooth.

I will premise my review by saying that there is more to a solid tail than just a gyro. You want slop free mechanics, Unloading of the servo (chinese weight mod) as well as a decent tail servo.  By costing less than $20, this gyro will free up your funds for $$ to spend on a decent tail servo (no, don't put a $10 servo on your tail if you can afford $35 for something that will peform way better).  On my 450, I have a JR 290G Digital Tail servo.  Thus I was able to set up the GY48V in DS (Digtal Servo) mode. When picking a tail servo, you want a KNOWN TESTED and trusted tail servo. Don't just read specs, read reviews, look at videos and research the person who is talking about it. Did they fly it? Do they even do any backwards or even advanced 3D flight? Go ahead and youtube search the GY48V gyro, See what people are putting as tail servos on thier helicopter.  I've tried cheap servos (TP-90, HXT-900, Fitec 9257D), they don't work well, and this gyro does not make a slow or cheap servo work like magic. Invest in a good tail servo. Look for one that you can get spare gearsets and cases (like the JR290G).

How I Mount the Gyro:
Mount the gyro onto the top or bottom of the boom block (your choice). Some people like to mount it on the bottom to protect it. I like to mount it closer to the vertical CG (The top of the boom block is about at vertical CG).  I use 2 layers of 3M indoor/outdoor foam tape (Grey in color and has red release paper).  If I know I have a helicopter that is problematic or prone to vibes, I'll use Kyosho green Zeal gel tape. Although I started with Zeal Tape, I took it off after initial flight tests and just used 2 layers of the foam tape.  Better foam tape is available like the Align or Curtis Youngblood foam tape. (I don't like the 3M white foam tape that has white/green release paper, people have reported it comes apart in heat or flight). 
(click image to enlarge)

NOTE: Disconnect motor while working with the gyro on the bench. Reconnect motor only when your ready for a flight test.

Servo setup:
For the servo, I start off by using an appropriate distance from servo center to servo ball. Unless the servo manufacturer or gyro manufacturer specifies a distance, I use 7-8mm for a 450 helicopter and 10-11mm for a 500 sized helicopter.  This typically will allow me to use 90-100% on the travel limit dial and reach full right tail movement without the slider hitting the inside end. With the ball much further out, you gain servo linear speed but lose servo resolution and torque. With it moved inward too much, you gain torque but lose servo speed and at the extents (needed for fast piros or holding a tail slide/backards flight), you would lose your linear movement and the tail might blow out easier.  The Gyro is first switched to the appropriate servo speed (DS=Digital Servo, NOR=Normal Analog servo). All subtrim and trim is removed from the Tx. Hook up the gyro to the Rudder channel and Gyro gain channel (Gyro gain channel is typically CH5 or Aux2 depending on the Transmitter and Rx.  Flip the gyro gain switch so that you are in Rate mode (LED OFF ON GY48V). Mount the servo horn so that the arm is 90 degrees to the tail rod (as shown, with the JR290G, I'm using the small X shaped servo horn and I"ve trial fit it to find out which arm will give me 90 at zero trim.

(Click to enlarge)

Servo position on the boom:
I typically will set up my Tail servo so that when in Rate mode, the tail rod length or servo position on the boom will yield near zero tail drift while in a hover in idle up.  On an unmodified 450 or 500 Align or Clone, this will be a mm or so LEFT of center on the tail slider. The Tail blades will have pitch shown like in the following 3 photos. Note how the leading edge of the tail blade when on top is facing back. In the right most photo, the top blade tip is pointing right and the bottom blade tip is left.



Servo Delay:
For a fast Digital servo like the JR290G, I set this value to fully CCW (zero delay). The delay is typically increased for a slower analog servo, or if you get bounce at the end of a quick piro. It will soften the tail movement when you quickly move the sticks. Too much delay can make the tail feel "mushy" and DELAY to the reaction of your sticks.

Servo Limit:
With the gyro still in rate mode, Start with the dial at full CCW value.  Move the tail stick a little RIGHT. (If your tail slider does NOT move left when looking from the back of the helicopter, reverse your tail channel (not the gyro gain channel).  Move your stick slowly right. Move it all the way to the end and make sure it does not reach (It shouldn't if you have used the ball lengths I have recommended. Now with the stick full right, increase the limit value slowly moving it CW (using that small plastic screwdriver that came with the gyro) until the slider just gets to the full left movement. If you go too far, you might hear the servo buzzing. Set the dial so that it is NOT hitting the end. Now slowly move full left. The tail slider should NOT hit full right slider movement. If it does, turn down the limit dial. You should have more than enough slider movement for nice piros and tail holding.  

Servo Reversing:
Still powered in Rate mode, I perform a bench test (Pinch test). Reverse the Gyro if needed.

Ready for flight test. I will set my gyro gain for 30% (once again, I don't use gyro sense, I use gear mode). That is typically enough for a maiden flight with enough tail holding and likely no wag. If it wags on take off, lower gain.  It is best to test the gyro on a day that is not very windy.  DO NOT FLIGHT TEST INSIDE YOUR HOME!.  Before you flight test, allow the helicopter to equalize to the outdoor temperare for about 10 mintues or more. When you power up the helicopter, DO NOT MOVE IT, after you plug in the power, the gyro will initialize.  It's best to initialize it in Heading Holde mode. Gyro LED will come on solid. You can switch to rate mode to carry it to your launch pad and switch back to HH mode before take off.  

Adjusting gain:
There are many methods for adjusting gain, You basically want enough gain to hold the tail and not wag. I will test hover and do some small up/down movment and 45 degree piros.  I will creep up the gain 5 points at a time looking for tail to start wagging. I will then back it down about 5-20 points depending on how high it gets (say wag at 90, I then set it to 75), (Wag at 50, I set it to 40).  I will then do some 360 quick piros. If it bounces at the end, I might move up the delay a little at a time.  With my 450 and the JR290G, I did not have to increase the delay and my gain was finalized at 75.  Then go flying. if your tail is blowing out or not holding, increase the gain. If you get bad wag in manuevers, back it down.

One thing I will add is that this gyro has an inexpensive Piezo sensor. These sensors are sensitive to vibrations and temperature changes.  If you have an unbalanced head, tracking error or unbalanced tail blades, it will affect this gyro MORE than a more expensive gyro (GP750, Mini-G, Spartan, GY401, GY520, LT2100 etc).  Those things are not good in general and should be addressed, but they will affect a piezo gyro more. Vibrations affect the gyro. Trimming will help, but as your headspeed drops in flight, so will the drift change.  Also, if you live in a climate where you fly in the cold or extreme heat, it is imperative, you let the gyro stabilize.  Temperature swings can make it drift during flight.

YOUTUBE VIDEO with EXI 450 and GY48V/JR290G
Another Video with GY48V (jump to 3:50 to see hands off in a cross wind)

One more thing, Use the Tx Travel adjust for Rudder in order to control the MAX Piro Rate
YOUTUBE VIDEO illustrating controlling Piro Rate

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