The HK-500GT is a clone of Align's T-Rex 500, thought to be manufactured by Skya in China and sold by HobbyKing. Other retailers (such as Giant Cod) sell helicopters with the same name but vary slightly in a few minor respects. The EXI-500 is reportedly very similar, and is also thought to be manufactured by Skya.

Contents 1 Specification 2 Recommended corrective action 3 Stock parts that need replacement 4 Recommended equipment 4.1 Head Speed 4.2 Power System 4.2.1 Motor 4.2.2 ESC 4.3 Servos and Gyros 4.4 Differences between HobbyKing and Giant Cod versions 5 Useful information 5.1 External Links

Specification

• Length: 840mm
• Height: 310mm
• Main rotor diameter: 970mm
• Tail rotor diameter: 200mm
• Motor pinion gear: 13T
• Main drive gear: 162T
• Tail drive gear: 31T
• Drive gear ratio: 1:12.46:4.68
• Weight(without power system): 1370g
• Flying weight: Approx 1700g

Recommended corrective action

• It is important to check all machine screws that are fitted into metal are securely threadlocked. Any screws that screw into plastic can be CAd if not tight. Often some screws have been fixed with too much threadlock. This can make it impossible to remove screws.
• Thrust bearings in the main and tail blade grips must be greased.
• Check that engagement between the tail autorotation gear and the belt pulley shaft gear is adequate and won't slip under load before flying. Many fliers have reported stripped tail gears, which is probably due to this problem. To perform a visual inspection for proper mesh, it may be necessary to remove the main gear from it's hub, and reassemble with the main gear missing, (unless the gears are vertically misaligned as in the photo to the right, or the lightening holes in the main gear are position such that they allow inspection - the HK supplied 500GT black gears do, the T500/GC/Align white gears don't). This allows the gear mesh to be viewed from above as in the picture below left. It may be necessary to slot the frame (below right) to allow the boom holder box to be moved forward by between 0.25mm and 1mm to fix an inadequate mesh, though modification of the pulley shaft bearing holders in the boom holder might be an alternative. Align main gears may have a slightly larger diameter, improving the mesh. However, the Align pulley shaft gear may be a fraction smaller. Even after changing the gears, it may still be necessary to slot the frame.

Stock parts that need replacement

Part description	Reason for change	Priority	Align part number	Possible issues with replacement	Cost
Tail rotor blade grips and securing bolts	Frequent reports of dangerous failures. Very weak bolts. Poor alloy grip design has stress concentrations at slot corners. Kits from before November 2009 also lacked thrust bearings.	Safety critical	H50034T / H50119T-00 / H50119T-75		UK:~£8+
Feathering shaft	May be supplied bent (check by rolling on glass), better quality bolts to secure main blade grips	Change if faulty, possible safety improvement	H50023		UK:~£4 (pack of two)
Main shaft	May be supplied bent (check by rolling on glass)	Change if faulty	H50086	See section on differences with Giantcod version - these kits will require changing other parts at the same time.	UK:~£7 (pack of two)
Tail shaft	May be supplied bent (check by rolling on glass)	Change if faulty	H50037		UK:~£4.50
Main drive gear or Main gear hub	May be supplied wonky	Change if causing vibrations, rubbing on frame or excessive misalignment with motor pinion.	H50018T and/or H50003T	See section on Giantcod version differences. Many have reported Align parts not being much better, so check before you buy if possible	UK:~£8 (pack of 2); ~£11
Tail drive gear	May strip easily (possibly due to wrong diameter)	Replace if faulty	H50043	Some have reported that this part is not fully interchangeable, with a different distance betwen the gear and the belt pulley, and a different gear diameter, though others have used successfully.	UK:~£8.50
Ball links	Too sloppy on some kits	Replace if any looseness	H50054T, H60071A	May be necessary to replace link rods also H50091T. Cheaper to get replacements from HobbyKing - "HK-500GT Linkage Rod"; item number 10164.	UK:~£2.50,£3,£2.50
Main grip thrust bearings and spacer washer	Spacer washer between axial and thrust bearings missing in a few kits, improved bearing quality	Replace if part missing	H50004T		UK:~£4.50
Tail servo holder	Some kits contain non-reinforced plastic part that is too flexible.	Performance improvement	H50038 (CF) or H50039T (GF) or H60041 (Trex 600 part allows use of standard servo for increased tail performance)		UK:~£4+
Dampers	Stock dampers are a bit soft, they will likely wear quickly and potentially cause problems with blade tracking. They are also slightly too large, causing binding when the bolts are tightened.	Performance improvement	H50022		UK:~£2.50

Recommended equipment

Head Speed

• 2200 rpm for idle up 1
• 2500 rpm for idle up 2

Depends a bit on your flying style and preferences of course.

Align advises not to go over 2650 rpm.

Power System

Motor

• Scorpion HK-3026-1600Kv 14T Pinion, 6S 2200-3000mAh 30C
• Hobbymate HB3650 1600Kv 14T Pinion, 6S 2200-3000mAh 30C
• Turnigy Typhoon 500H 1800kv 11T Pinion, 6S 2200-3000mAh 30C
• Turnigy Typhoon 500H 1800kv 12T, 13T or 14T Pinion, 5S 2500-4000mAh 30C
• Turnigy 3025-1500kv, 13T pinion, 6S 2200-3000 mAh
• Hobby King 500H Heli Motor 1600kv (500 Class)
• Turnigy 500 H3126 Brushless outrunner 1600KV

11T pinions are hard to find and because they are so small they will strip teeth from the main gear more easily than a larger pinion, so avoid 1800Kv motors if you plan to use a 6s battery.

ESC

• ESC: 60 or 80-Amp with 3A+ BEC
• Turnigy Plush (has a built in BEC) though the soft-start is very poor
• Hobbywing Platinum - has good soft start, low to mid range pricing.
• Super Simple (with an external BEC) (no soft start?)
• FMT 70 amp from ebay
• Castle Creations ICE (good, and highly programmable, but expensive)
• Kotronic Jazz (has the best governor mode, but expensive)

It's strongly recommended to use either a seperate BEC or switching one (SBEC), because the loads from 4 digital servos, plus the gyro and the receiver may exceed the capacity of a built in BEC. This could cause a receiver reboot, which will almost certainly cause a bad crash. If using a flybarless unit, this increases the current demand.

• Hobbywing 5-7.5A 8v-42v UBEC (possibly overkill but a safe option.)

Servos and Gyros

• Cyclic Servos:
  • Turnigy MG930
  • Hitec HS81, the metal gear version HS81MG is advisible because plastic gears will strip on a crash
• Tail servo:
  • Align DS520 (moderately priced and designed specifically for the T-Rex 500 tail)
  • Turnigy MG930 (a faster servo is recommended for more serious 3D flying)
  • Hyperion DS20GMD
• Gyro:
  • HK401B (see article for recommended mod)
  • E-flite G210HL MEMS headlock gyro used in Blade 450 Good reasonably priced option for sport flying.
  • Hobbyking/Assan GA-250 (early versions only work with digital servos). There seem to have been some issues with long term reliability.

Several fliers have reported tail servo failures when using cheap tail servos. It may be worth buying a good quality tail servo, as a single crash caused by a failure in flight would cost a lot more in spares than was initially saved. Gyro driven servos have a very tough life and need to be excellent quality.

Differences between HobbyKing and Giant Cod versions

• HK Main blade grips have a raised ring around the blade screw head
• HK tail grips and pulley case are fibre reinforced nylon, GC version are alloy.
• Main and autorotation gears are made from a different colour plastic to a different shape. (GC version appears to use HK-T500 parts here)
• The diameter of the bottom of the main shaft differs, GC version is 8mm, HK version is smaller like Align. This makes the main gear hub/one-way bearing assemblies non-interchangeable. (GC version appears to use cheaper HK-T500 parts here) If a stepped main shaft is to be used with T500 main gear hub, replace the one way shaft (Align H50017T) to ensure compatibility. There may be problems with the hole through the tail rotating gear and one-way bearing case/main gear hub and the main shaft lining up, in which case it may be necessary to replace all three parts.
• The HK version has a three-piece skid assembly, with aluminium tube skids. The GC version is a one-piece plastic molding as per the HK-T500.
• Cosmetic differences such as HK version has laser engraving on hub, main blade grips, tail boom, and machined silver ring on head button.
• ...

Useful information

From RCGroups thread (The number at the start of each paragraph is the post number) Sections can be removed when information has been integrated into the article.

7 - It appears that the HK-500GT is manufactured by the same company as the EXI-500 "plastic version" and CopterX 500, just rebadged for HK.

17 - One thing to clarify about the cyclic servo installation - frame spacers are NOT needed for the TowerPro MG930 servos installed in the front of the HK-500GT frame because they fit perfectly without making contact, unlike other servo brands which require spacers to fit into the EXI 500 frame. I'm not sure if the frame dimensions are any different on the HK-500GT compared to the EXI 500 (I'm assuming they are identical since both are "T-Rex 500 compatible"), but I know some of the Hitec digitals (such as the 5245) will not fit into a T-Rex 500 frame without spacers. Finless Bob recommends NOT using the rubber grommets for the servo. I however used them anyway as they do reduce vibration to the servo, and if you wrench them down tight enough, wobble won't be a factor in the slightest sense. Finless Bob sometimes goes over the edge with his recommendations; IMO not using the grommets is a poor idea for many reasons (i.e. minimizing vibration on the servo as to not loosen the servo screws during flight). It's not just Nitro heli's that vibrate, electric heli's vibrate as well, hence the need for using blue loctite on any frame screws that thread into metal.

25 - A few spritzes of a silicone-based lubricant can help prevent belt static, avoid petroleum-based products as they can cause rubber to deteriorate more rapidly over time. However, it's only a temporary fix. Some guys will run wire from the boom to the negative lead on the ESC, but in all honesty running a wire connecting the boom to any area of the frame should be more than adequate. The T-Rex Wikipedia write-up specifically mentions the T-Rex 500 as being especially susceptible to static issues...

30 - I've NEVER heard of people having issues with the AR6100's on heli's, I know several guys who use the AR6100's on the much larger 600 sizers and have had 0 issues, no hiccups, no glitches, nothing but 100% reliable operation. Is the 6200 a safer bet? Perhaps, but it's nearly twice the cost, so if you're trying to build a 500 on a budget, the cost of the 6200 over the 6100 might be significant.

36 - I use the governor within my CC Phoenix ESC to set a specific head speed (keeps the blade RPM's within reasonable limits), it works well for my purposes and I run the throttle up near 95% once I'm at neutral pitch or above, though most fly'ers in my club don't use the governor at all with an electric heli. They set their throttle according to pitch and set the ESC for fixed endpoints. The new Castle firmware will tell you your approximate throttle % (within the SET RPM governor mode) based on the specific head speed that you set on the throttle (0-50%, 51-99%, and 100% throttle). You then input the motor Kv, gear ratio, and number of poles in the motor, which is what the Castle firmware uses to calculate your throttle % at a given head speed. Then you set your throttle % within the pitch curves for each flight mode, in most cases your pitch curve will end up flat. The reality is that it's perfectly fine to just set your throttle in the radio, and used fixed end points within the ESC. I would not recommend using governor mode in a Turngiy ESC as many have said that it's unreliable. For electric heli's, the ESC likes to run near 100% throttle anyway (because the motor is constantly running, unlike a plane where the motor runs at varying speeds all the time), the closer you are to 100% throttle, the better the efficiency out of the ESC and motor. If you're inhibiting throttle, the ESC has to apply more resistance to reduce the current going to the motor, meaning the ESC will get warmer. It's a lot more important with a heli to get a proper match between battery/esc/motor/pinion size so that you achieve proper head speed for the size of the heli without bogging down the motor or drawing more current than the ESC or battery is rated to handle continuously

61 - Autozone happened to carry the CRC Di-Electric silicone-based grease for about $9 per 3.3 oz. bottle, enough to lube thousands of thrust bearings, no other well-known stores had silicone-based grease, was glad that Autozone had this stuff so I bought a can of it. It has its own applicator (not needle-precise, but precise enough for thrust bearings), and is 100% petroleum-free. It's approved for use on o-rings, rubber parts, flashlights, batteries, motors, electrical contacts, etc.

70 & 90 – Chinese Weight Mod. http://www.mycoolheli.com/chineseweightmod.html My chinese weight mod on the 500 looked like this: 3mm x 20mm cap head screw 7 total 3mm steel washers, 4 on the outside, 3 on the inside Nylon locnut on the inside. Depending on the thickness of your washer, you put as many as you can fit and still have the screw reach the end of the nylon locnut. You also may have to put more on the outside then the inside. The reason is that you don't want the screw sticking through too much on the inside that it hits any of the tail stuff like the control arm and such. You need to leave room for any flex under power too so don't let it get close

74 - As for mounting the electronics, check the T-Rex 500 manual and some of my photos. I mounted the ESC and BEC on the left side of the heli, and the Rx on the rear, which was one of the recommended mountings within the T-Rex manual. My Gyro is mounted on the top of the boom housing, many others will recommend against this but I'm not too concerned about a $20 Gyro getting shredded in a crash. Most of my wires are routed through the inside the frame to the back where the Rx is located. Number of servo extensions used: 0.

183 - Here's an EagleTree graph from a brief flight this afternoon. Flight style was mainly hovering with a few punch outs to see how high I could spike the amp draw. 36 Amps was the peak current draw reading (743 Watts). I attempted to record the flight in HD, but no video made it onto the SDHC card. I probably thought I hit the record button but simply did not. I'll get video tomorrow.

Power setup for anyone who's curious:

• Motor: Scorpion HK-3026-1600Kv
• ESC: Castle Phoenix 80-Amp
• Throttle curve: V-shaped throttle, 100% at the lowest point, 70-80% at mid points, 100% at the high point (Spektrum DX7)
• Servos: 4 x TowerPro MG930
• Pinion: 14T
• Battery: 2 x 3S (6S) in series, 2200mAh 30C
• Avg. Flight time expectation: 7-8 minutes

188 - I run about 2900 RPM and It's hot and responsive at that RPM. I ran about 2600-2800 RPM and it's pretty docile down at that RPM. If you wanted to run a lower RPM, you really needed a 5S, 1600Kv motor or say a 12T pinion.

189 - BEC's can cause erratic behavior when they are overloaded or overheating, I'm guessing your tail servo wasn't getting a good voltage supply from that internal BEC which may have been why you were having tail drift issues. I'm honestly surprised you didn't cook your internal BEC after a few seconds or minutes of flight, especially if you're using 6S to power your 500. Internal BEC's are often only rated to handle up to 3S, the rule of thumb that I follow is 3S or 3 Servos. Even on a 450-sized heli, where I'll run on 3S, I use an external BEC because I want to make sure all 4 servos are all getting a constant 6V and that I'm not overloading the internal BEC of whatever ESC I'm using. The Castle Phoenix user manuals always state that the internal BEC should be disabled (using an external BEC instead) when you're using more than 3S or 3 servos. My head speed comes up near 2600-2700 RPMs at 95-100% throttle, I'm using a 14T pinion on a 1600Kv motor (powered on 6S). Your throttle curve will also need adjustment, you'll find that having 25% across the board, even if your head speed is up there, will cause poor performance in both negative and positive pitch ranges on your throttle. Most set up their throttle curves in a "V" shape, the lowest point of the V ending up at the 50% mark, with the throttle at its highest points at the low/high point of the curve. This is a typical setup for 3D (inverted flight). However, I find it works well for sport flying and forward flight also.

195 - BL Motor Hobby city HK 1600Kv with stock pinion Cyclic Servo Tower Pro MG930 Digital Metal Gear servo Tail servo Futaba S9257 Gyro Futaba 401 ESC Mystery 80 A(Plan to replace with Turnigy 60A or other) UBEC Turnigy 3A with Noise Reduction Li-Po Flightmax 5S 20C 3000maH Li-po E-Fly 6S 25C 2800maH Li-po Mystery 5S 25C 2800maH

198 - HeliDirect.com. Great customer service, fast shipping, and their Rhino pinions are simply the best that I have used (quiet, hardened steel, mesh with the Align gears perfectly). Here's a link to HeliDirect's pinion page for the search results on "500 pinion" -> T-Rex 500 Rhino Hardened Steel Pinions. The Rhino hardened steel pinions go for $2.50 for 2 ($1.25 each), and are vastly superior to the Align brass pinions (which are soft and noisy). You'll need a 0.6M 5mm pinion for the HK-500GT. Depending on motor Kv, if you're around 1600Kv, 14T is good. For higher Kv motors (such as the Turnigy Typhoon, 1800Kv), the 13T would be a better choice.

202 - One of the guys at my field runs his Turnigy Typhoon 1800Kv on 6S using a 13T pinion, his head speed is high but his heli performs very nicely (he has a Flasher 500). Why not start off with this 12T Rhino hardened steel pinion from HeliDirect? At $2.50, even if your head speed is too hot for comfort, you can dial down your throttle, or continue in your search for 11T. I haven't heard of too many using 11T's on a 500 (that's the size I use on my 450), and HobbyCity includes a 13T pinion with their HK-500GT kits (while also recommending the Turnigy Typhoon 1800Kv motor). Btw, the 13T pinion included with the HK-500GT seems to be identical in quality and material to the Rhino pinions sold at HeliDirect. It is probably manufactured at the same company HeliDirect uses for supplying their "Rhino" pinions.

204 - Looks like the 11T are out of stock at ready heli. http://www.readyheli.com/RevCo_Hard_.../ho-0600lh.htm Several EXI 500 pilots are running 11T's with the Typhoon 500H. It was said that battery time will be reduced if your not running 80% throttle curve or higher on the motors. I don't know if that is true or not but It did seem that when I went to an 11T my flight time got better. I set my timer for 6 minutes and can hover for 7 minutes easily with the 11T. I found that with a 12T even, that the headspeed was just not consistant when flying. I'd pull a roll and while inverted the headspeed jumped up alot. I could have possibly messed with the throttle curves some but I just find that the flatter a curve I get closest to 100% the better the heli flies. Typically I find a 100,95,90,95,100 curve up to flat 100% in idle up just flies the best. If I can load up my RPMS near zero pitch, it helps w/ tic tocs, rolls, flips and such.

216 - http://www.mycoolheli.com/gyrobenchtest.html

226 - http://www.bphobbies.com/view.asp?id=D0896182

228 - Xheli carries the EXI 500 parts that is the same Skya heli as the HK500GT.

236 - esky belt cp trust bearing can be retrofit to plastic HK tail blade grip

243 - Motor : Taiwan 1630Kv Pinion : 12T Minutes flown : 6:00 Mah put back in : 2000 Battery type: Turnigy 3000mAh 20C ESC type and Timing :Volcano 60A, Timing = Low mAh per minute : (mAh put back in / minutes flown) : 333mAh/Minute Special notes : 100% flat throttle curve

Motor: Scorpion HKII-3026-1600Kv Pinion: 14T Rhino Hardened Steel Minutes flown : 6 minutes 20 seconds mAh back into battery: 1400mAh consumed Battery type: Zippy FlightMax 2200mAh 3S x 2 (6S) 30C discharge mAh per minute : 250mAh/minute

Motor: Turnigy Typhoon 500H 1800kv Pinion: Stock Minutes flown : 6 minutes 5 seconds mAh back into battery: 1954 Battery type: Zippy FlightMax 3000mAh 6S 20C discharge mAh per minute : 325.6 mAh/minute

350 - I used the single, one-sided arms that came with the MG930 servo and placed the ball links on the outer-most holes for cyclic. You have to be real careful about drilling the hole in the arm (a 1/16" drill bit works best) for the ball link as to not weaken the plastic too much. On the tail servo, I used the 4-sided control arm and clipped 3 of the arms off, then used the 2nd hole out (from the center) on one of the thick, longer arms. I used the T-Rex 500 manual as a guide for determining the distance from the center of the arm to the hole. After at least a couple dozen flights, there is no sign of weakening or "give" in any of the servo arms.

377 - You can run the throttle curve lower to around 70% until you are comfortable. This may put extra stress on your packs and ESC though. Brushless motors like to run at full speed. This is where they are most efficient. Personally if a 13tooth pinion will get you 2600 - 2700 rpm on the head, I would run it like that. 26-2700 rpm is a sweet spot for 500 size machine. If you are not comfortable with that though, I would look at dropping pinion size before lowering the throttle curve It's better to drop down a pinion size rather than compensating on the throttle curve. Even though a larger pinion might squeeze out higher RPMs, it can cause the motor to bog down on a climb out. I run a 13T pinion with a 1600kv motor, this set-up gives me a head speed of 2425 which is fine for someone with little experience like myself.

388 - A 13 pinion will be better on 6S lipo,asuming your motor is 1600kv. A higher HS is always better to fly circuits etc. A slower HS is better for a beginner,less intimidating and more forgiving of wrong stick input with hover practise. I always set up my Normal.setting slower and then crank up the HS in Idle1 &2.

423 - I purchased mine (Rhino hardened steel pinions) from helidirect.com. If you're going with the 1800kv Turnigy Typhoon motor, 12T is as large as you should go on 6S. If you read back a few pages, you'll notice that a lot of others are pursuing 11T pinions for that motor (on 6S). The HK-500GT (as well as the T-Rex 500) requires 0.6M pinions and the standard shaft size is 5mm. Here's a link to the helidirect Rhino pinions for the T-Rex 500... http://www.helidirect.com/advanced_s...inions&x=0&y=0 Note that the stock 500GT pinion is 13T (fine for 5S on an 1800Kv motor). I use a 14T pinion which gives me ideal head speed and performance on a 1600Kv Scorpion motor.

432 - Your Idle up (ST1/ST2) curve should be V-shaped, such as: 100-90-85-90-100 (this is what I use in ST1 mode) 100-95-90-95-100 (ST2 mode) If your power setup and pinion are matched ideally for your motor, it's best to run near 100% throttle, this is where your motor will operate most efficiently. If your head speed is too high at 100%, set your ST1/ST2 curves at 90-85-75-85-90, just make sure your highest throttle points are reasonable in terms of head speed. If you get into inverted flight, it's important to have a symmetrical V-shaped throttle curve so that your negative pitch will have as much climb-out power as the curve in the positive pitch range. Just keep in mind that your heli will come down fast when you punch into negative, so you may want to try the curve out within a simulator so that you are accustomed to it and know what to expect at full throttle when you punch into negative. All of the guys who fly heli's in my AMA club who do not use governor modes set V-shaped throttle curves, I learned this from the other experienced guys in my club. You don't want your throttle to cut in the full negative in your idle up modes, if you're hovering 20-30 feet off the ground and you punch full negative on a normal throttle curve (where point L, or full negative, is set to 0%), you'll shut your motor off which can possibly cause a crash due to soft start mode, your motor may not spin up in time to save your 500GT from hitting the ground hard. Generally the normal throttle curve is only used to start up the heli, but if your ESC has a decent soft start, you don't even need to use normal mode at all, or simply set your normal curve to start at 50 so that you don't accidentally spin down your motor when you're 10-20 feet in the air. Throttle should be cut only by the throttle hold (i.e. DX7) or a separate throttle cut switch. The point is, you don't want to throttle your heli down at *any* time during normal flight. If a crash is inevitable in flight, you'll reduce damage by hitting the throttle cut switch so your blades won't be spinning at full RPM when the heli hits the dirt; in most crashes, you often won't have the time to react and hit your throttle kill switch, but it's a good way to reduce head damage in a crash if you kill that throttle in time. If you really want to taylor the heli to your style of flight, you can mess with pitch curves also to "soften" the pitch on the negative or positive side to control the rate at which your heli will ascend and descend at the various throttle positions set in your throttle curves. The Finless Bob videos on helifreak.com explain all of this in more detail

470 - Depending on your Tx, you can "sort of" simulate a soft start on a crappy ESC using the throttle curve (just make sure you don't fly on that curve). Set the normal curve to 0-15-35-70-90 or something that only gives gradual throttle from full negative to the mid point, then throw the Tx into idle-up (ST1/ST2 modes on a DX7) mode and avoid flipping your throttle switch to normal during flight. Always remember to spin up the heli in normal mode as flipping it into idle-up from the start will result in a really fast start combined with an inevitable tail kick.

471 - You're right about the 500 having static issues, most notably the carbon framed T-Rex 500. The Aluminum frame/boom on the HK-500GT actually works in favor of preventing/minimizing static. To date, I have not grounded my boom and have had 0 issues with static during flight. If you live in an arid climate, however, I'd ground the boom for preventative reasons. I wouldn't use a ball driver (with the rounded end), a quality hex driver is key (hardened steel preferably). Most of the frame screws, if I recall, are 2.0mm. The button head screws on the main blades are 2.5mm, but there are some 1.5mm button head screws on there also, so it's good to have a complete set of hex drivers to make sure you have all the sizes covered.

575 - use lithium grease on the bearings and tri flow on the slider and other parts

584 – Photo of grounded boom. don't forget to scrape the boom.

625 - I replaced the main shaft bearings, dampeners, main shaft, and spindle. Everything else is stock.

626 - 4 turnigy servos, hb 3650 motor, hobby city gy401 clone gyro for $14, and turnigy BEC.

633 - Don't over-tighten the button head screws in the grips - if you have trouble moving the grips by hand, so will the servo, there should be no resistance within those grips, they should move freely and smoothly. The trick is to add a drop of blue loctite on each screw and get them both screwed in to the point where they are in there firmly, but not tight to the point where the grips don't move, the grips need to rotate freely back and forth without binding. The grips should not wiggle or pull away from the center of the tail rotor, if the grips don't move in and out, you have screwed them in far enough. Don't lather the screw with too much loctite as you will risk getting loctite into the thrust bearings, this can lock the bearings and prevent them from moving smoothly. Allow the loctite to have a couple of hours to set up, it will fully cure overnight, locking the bolts in place. The same applies to the main blade grips, over-tighten the feathering shaft bolts and you'll have binding issues. Do not get any grease on the screw threads or they may come loose during flight (the grease will prevent the loctite from adhering to the threads) which could spell disaster

637 - Main and tail grip binding issues: I'm going to assume that Skya makes the GT for Hobbycity as the EXI version, so here it goes... Main grips: Get some Align dampners. The supplied dampners are too big, and bind up the grips when they are tightened down. Or take a razor blade to the supplied dampner to shorten to proper size. Tail grips: There is a washer under the inner thrust bearing race which is there to remove tilting slop while on the bench. A nice inclusion, the only problem is that it is too thick. The Align birds dont have this washer...remove. I do not know if the Align grips rock on the bench or if they have better tolerances, but while spooled up I'd guess that centripetal forces would make this slop disappear. If you want to stick with a slop removing washer and do not have a 6mm ID shim of appropriate thickness, a 4mm Tamiya shim (on mine a .01mm on one side and .02mm on the other side) between the hub and grip radial bearing can be installed to take up the slack and not bind up the grips. Using these ideas you can torque down the screws and not rely on locktite to keep the screws in place. Also note that there are large and small ID thrust bearings in the head and tail...and where they are supposed to go

716 - 5S pack is better suited for the Typhoon 1800Kv motor, you can get away with 6S if you govern your throttle (or lower values on your throttle curve). 2300-2500 RPMs is an ideal head speed for the 500GT. If you check the dark horse calculator, 6S on a 1800Kv motor equates to a head speed of roughly 3000 RPMs, which is way too high for a 500 sized heli. Don't go higher than a 12T pinion on that motor. A motor in the 1600Kv range is more ideal for the 500GT as it gives you more pinion options as well as being well-suited to run on 6S high capacity batteries. Ideally, you want to run your heli at a high throttle % to get the best efficiency out of your power system, but 6S on an 1800Kv motor won't allow for that. 5S, on the other hand, will work just fine.

746 - I'm using upgraded dampers (helidirect) with the Align feathering shaft, but the washers/bearings in the blade grips are stock. I'm considering ordering a few sets of the ABEC-3 bearings from helidirect also, and replacing the stock HK bearings (in the blade grips for now, might replace the rest later) with the ABEC-3 versions. Anyone have any experience with them? Am I correct in assuming the bearings in the main blade grips are 6mm x 12mm x 4mm (considering the thrust bearings are 5mm x 12mm x 6mm)?

747 - Radial bearings, the manual shows 6x12x4, MR126ZZ

763 - Sure, you can buy the Align screw set from helidirect for $7, here's the link: Align T-Rex 500 Frame Screw set The part number is H50048-1 if you want to check prices at other vendors.

784 - 1850Kv motor needs an 11t pinon gear to work with a 6s battery. The 12 and 13t pinons are for 5s batteries

788 4 x Turnigy 930MG Digital Servos: ~$60 1 x HobbyKing heli 500 Motor (1600Kv): $22 1 x HK 401B Gyro: $14 1 x Turnigy Plush 80A w/UBEC: $40 1 x HK-500GT Kit: $67

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Total: $203 Get it shipped for ~$40 3-5 day EMS Express ($31 for US Air Parcel) Add a 6S battery (unless you have a couple of 2000mAh+ 3S batteries already on-hand) for about $34

809 - It's not a bad idea to order some extra flybars (stabilizer bars), feathering shafts, and a main shaft, though the Align versions of them are better (made of higher quality hardened steel) but also more expensive. For the tail servo, the TowerPro (now Turnigy) MG930 is fine for sport flying and mild 3D, but the ds520 is obviously nicer. If you want to go full size, the Hyperion DS20 is fine and priced very reasonably.

838 - Here is what I did for servo mounts. I tried the grommets and eyelets but they are crap and the head of the bolt goes down in it. So, I have plenty of spares so I used some extra servo brackets and drilled them out so the bolt will fit. Works great!

841 - If you're aiming to fly competition style, the higher Kv (1800Kv and up) motors on 5S are where the high performance is at, but the best all-purpose setup is a lower Kv motor (~1600Kv), they are ideal for 6S and you have a wider variety of pinion choices there, 12-16T, depending on where you like your head speed and what bogs your motor on climb-outs. 6S on a 1600Kv motor will also have lower Amp draw characteristics, that equates to longer flight times and less wear on the LiPo packs. $100 on shipping seems outrageous, try breaking up your order in segments and you may be surprised that it will lower the overall shipping costs significantly, but I still have a hard time believing that your shipping would cost $100.

875 – Hobbymat HB3650 works fine for me as far as I can tell. Runs very smooth. Using 6s and 13t pinion.

951 - investing in decent electronics rather than worrying about replacing the stock parts with Align parts, unless you are some sort of world-class 3D performer that plans on pushing every component to its limits. If you have an advanced skill set, then I would recommend replacing the gears, main shaft, feathering shaft, stock blades (with carbon fiber), and adding metal control arms to the metal head to reduce play. However, there is very little play on the stock head out-of-the-box, so the 500GT really is a good buy regardless of what some others have posted/stated about HK heli clones. The Turnigy (formerly TowerPro) MG930 Digitals are great cyclic servos, and I'm even using one on the tail, HobbyKing sells them for ~$14 each. The HK Turnigy motors generally have positive feedback from those who use the motors in their heli's, and the HK-401B Gyro is a real bargain at $14, so in all honesty you can put some decent electronics on there at a great price directly from HobbyKing.

978 - The higher-power Turnigy Plush ESC's (60A and up) have built-in switching BECs that are rated up to 6S, so no need to really wire an external BEC if you go with any of the high Amp Plush ESC's. If you go with a SS ESC, you will need to wire a BEC to it. The Turnigy 3A-5A BEC's are available from HobbyKing for ~$7, I use one of these myself on my 500GT (combined with a Castle Phoenix 80A ESC) and it works great. An external BEC is easy to install, you solder it to the male Deans connector used on your ESC, just match up the +/- wires and solder the ESC battery leads combined with the leads from the BEC to your ESC male Deans connector. After you solder the battery leads from the BEC to your ESC/Deans plug, you pull the RED wire (just lift the plastic tab) from the 3-pin Rx connector so that battery power is no longer routed from your ESC to your Rx, rather the battery power for the Rx comes from the BEC. I have always used the 6V jumper setting on the Turnigy BEC, by default they are set up for 5V, which is fine for most applications, but you'll get better servo response on 6V. What I have done (which allows for an easy BEC swap-out) is to wire a JST plug to the Deans plug on the ESC, then I can just plug the BEC into the JST and unplug it if I need to swap it out (if it fails). The Castle BEC's are nice because you can configure the exact voltage (from 4.8V all the way up to 9V in 0.1V increments) using CastleLink, but it's definitely not a necessary feature. Castle has a great diagram on their website showing the wiring diagram, it's fairly straight-forward. If you can solder a Deans, you can easily solder the BEC during the Deans installation.

980 - The best governor is most likely the Kontronik Jazz... CC governors have improved over the years but are stil fickle to set up and, in my experience, not as 'smart' as the Kontronik. Kontronik is a one step setup (work out the throttle setting for the desired HS) - it works out all the other stuff like motor timing, acheivable HS for a particular pack etc. during initial spoolup. It's not necessarily true that a BL motor will be at it's most efficient at 100% throttle (not my any means) there are many other factors that come into play - such as the max RPM that the motor can run at, config of the motor (windings etc.) and, not least, the ESC capabilities. It is true to say that in general it is inefficient to run an ESC at less than 80% throttle with heavy loads (such as a pitch loaded heli rotor head) - but that does depend on how smart the ESC is (again Kontroniks seem to cope better). In general you'll end up with a lot of excess heat if you do this - in the ESC, batteries and motor.. can cause damage and also wastes a lot of power.

External Links

• HK500GT at Hobbyking.com
• T-Rex 500 manual on Align website
• Trex 500 build videos from Finless Bob. (There are some differences with the T-Rex but the videos are useful anyway)