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Old Oct 13, 2009, 03:16 PM
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Western NY
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HK-500GT 3D Helicopter Build Thread

I will update the first post regularly with part replacement recommendations as various issues surface and are resolved.

This post last updated on: April 22nd, 2011 (Added some notes for HK-500CMT kit build)

The HK-500GT was delivered by USPS today, it arrived quickly via EMS express shipping from HobbyCity. Everything arrived in perfect condition, no damaged or crushed parts. The fiberglass canopy looks great, sharp paint job and lots of room inside.

From what I can tell, the frame does seem very rigid and it's light weight. According to HC's website, the head and tail are composed of FRN Fiber Reinforced Nylon. The head has a lot of metal parts, and is not "plasticky" as are the cheaper HK helicopter heads. The FRN alloy parts on the head and tail really do seem quite tough.

Pictured are the 4 TowerPro MG930 Metal Gear digital servos (will be using for cyclic and tail), upgraded C/F fin and stabilizer (from helidirect.com), and a metal motor mount to replace the stock HK-500GT mount. I will begin the build this evening, and will take some photos as I progress with the build. I'll point out any inconsistencies or problems with any parts along the way.

For others building the HK-500GT:

Let's keep all the build-related discussion for the HK-500GT within this thread, rather than spinning off multiple other threads for the same build. I didn't start this thread to become my *own* personal build thread, I am hoping this thread opens up discussion from all others who want to post their build experience.

------------------------------------------------------------------------

References:

HK-500GT Product Page

T-Rex 500 Assembly Manual
(use as a guide for the HK-500GT assembly)

Dark Horse Calculator - very useful for determining how much power your heli will draw based on Motor Kv, battery, and pinion size. Lots of T-Rex heli presets.

Finless Bob Heli Setup 101 Videos - anyone new to heli's, this is a must-watch

Melnic's EXI 500 Setup Summary - excellent summary of popular servo, battery, pinion size, motor, and Gyro choices for the EXI 500, which also applies to the 500GT considering they are both manufactured by Skya in China.

------------------------------------------------------------------------
Stock parts that need replacement:


I will maintain a list of recommended replacement parts for the HK-500GT in this section within the first post so that new readers can see this info up-front either before buying or before assembling the HK-500GT.

You should NOT fly the HK-500GT until the following parts have been replaced:

(1) Tail rotor assembly (tail rotor blade grips). DO NOT FLY on the stock tail rotor, use of this part will cause loss of tail control and may result in a crash or serious injury. This problem was first noted by st200ol within post #42. The stock tail rotor contains no thrust bearings (though NOTE THAT THIS HAS BEEN RESOLVED IN NEWER 500GT BATCHES), which means that the tail rotor will not be movable at ideal head RPMs > 2000 RPMs. The tail may seem fine at lower head speeds, but once the head speed comes up where it should, the tail will be virtually unmovable. Replace with Align part H50034T, or just buy the correctly-sized thrust bearings. Average price of the part is $12.99 at most hobby shops and online vendors. You can continue to use the stock part once you add in the thrust bearings, as per the T-Rex 500 assembly manual. The stock tail rotor should be replaced with the Align part regardless of the presence of thrust bearings because the Align bolts are much stronger/harder than the stock 500GT tail grip bolts.

*** UPDATE Dec. 16 2009 *** HobbyCity (HobbyKing) has supposedly CORRECTED this issue as of November 2009, and now include thrust bearings in the tail assembly. I have not received any confirmed reports, however, of the bearing issues being resolved.

*** UPDATE Feb. 4th 2010 *** It is still recommended to replace the stock 500GT tail rotor grips with the ALIGN part, H50034T. As a few have noted with the EXI 500, the bolts in the tail grips can break/sheer during flight which result in uncontrollable piro'ing and can result in a serious crash. Tumber noted this issue on Feb. 4th, 2010, as his 500GT piro'd out of control and he noticed that one of his tail rotor grips had gone completely missing.

*** UPDATE Mar. 17th 2010 *** A user has reported this his stock HK-500GT flybar paddles gave out during spin-up testing indoors which resulted in property damage. If other reports surface, the paddles may need to be changed out with the Align T-Rex 500 flybar paddles. I'd also recommend replacing the flybar with the Align part since the material used for the flybar and threading might be higher quality. The paddle failure was not the result of a faulty part, rather a result of blue Loctite coming in contact with plastic. Locite reacts with most plastics and severely weakens plastic, causing it to shatter when the slightest pressure is applied. DO NOT USE BLUE LOCTITE ANYWHERE NEAR PLASTIC!!! Use Medium CA instead, it works nearly as well and will not harm plastic parts.

(2) Tail servo holder. Stock tail servo holder is too flexible and does not include a c/f or FG mounting plate for the servo, so the tail servo can move during flight which will reduce throw and response for rudder control. Replace with Align Part H50038, avg. price at hobby shops and online vendors is $9.

(2b) Tail servo holder. As per Melnic, an even better solution may be to replace the stock 500GT tail servo holder with the T-Rex 600 part (H60041). This will allow the use of a standard servo, providing more torque and better response on the rudder.

(3) Feathering (Spindle) Shaft. The stock feathering shaft bolts are soft/weak and may sheer off during flight, this could cause serious personal injury so the recommendation is to replace the stock spindle with the Align part. The Align part number is H50023.

You should replace the following stock parts of the HK-500GT before your first flight, but experienced Heli pilots might be ok without replacing right away:

(1) Tail gear assembly. Replace with Align part H50043. (tail pinion gears will strip out easy in a minor crash or hard landing).

(2) Dampers. Stock dampers are a bit soft, they will likely wear quickly and potentially cause problems with blade tracking. Replace with Align TRex 500 dampers (H50022) or these upgraded dampeners from helidirect.

------------------------------------------------------------------------

Remember to always do a spin-up test before installing the main blades to ensure that your motor is spinning in the correct direction. Ensure that the main rotor is spinning CLOCKWISE, and that the tail rotor is spinning COUNTERCLOCKWISE. The next step is to spin up with the blades installed (make sure they are in the proper direction, I've seen tail blades installed backwards many times) and make tracking adjustments until the blades are tracking properly. Then observe behavior of the heli on a flat, relatively smooth surface so that tail behavior is observed before your first hover. This will help eliminate a large percentage of crashes that can occur during the maiden flight.

April 22nd, 2011 Updates:

It's been awhile since I've updated the first page, but wanted to put some notes in here about the HK-500CMT kit. I recently assembled one of these for a friend of mine and wanted to point out a couple of minor issues.

Issues with HK-500CMT build:
(1) Belt tightness - out of the box, making no modifications, the belt will be too tight with the boom pushed all the way in as well as the tail assembly being as far forward as possible on the boom. Easy fix: simply shave off a mm or so off the end of the boom. This can be accomplished using 200 grit sand paper. Mark a line 1mm from the edge of the boom with a Sharpie, and sand away using a sanding block until you hit your 1mm mark. 2 minutes worth of sanding is all you'll need. A drum or belt sander could also be used to really speed things up, but be careful not to shave off too much metal or you will not be able to sufficiently tighten the belt. The stock boom is made of fairly soft aluminum, so there is no reason to bother with a hacksaw or a dremel, unless you are highly skilled. The other option is to replace the stock HK-500CMT belt with the Align belt, which is the correct length.

(2) Metal tail assembly - the tail housing does not clamp down tightly enough on the end of the boom (there is no nub on the end of the boom to fit into the tail assembly housing), it can rotate by hand force and may rotate during flight. To fix it, insert a thin object such as a zip tie or a small thin piece of scrap metal through the hole on the tail housing when the clamp is as fully open/loose as possible, that should allow the tail housing to clamp to the boom sufficiently. The problem is more noticeable in cold weather (as the metal will expand and contract with varying temperatures).

Other than that, the CMT kit was good quality. Most if not all the screws I found were already thread locked at the factory, though I disassembled the head and tail to re-threadlock all the screws after greasing the thrust bearings. The thrust bearings were in fact oiled at the factory, but grease is preferable as it won't fly off from the forces of rotation.
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Old Oct 13, 2009, 09:13 PM
Gone Flying.
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Spent some time this evening assembling the HK-500GT. All the screws on the frame are wrenched in with blue Loctite, so removing them is a pain, but a set of good Hex drivers will do the job. The first step I took was assembling the landing gear. This was simple, small bolts fit into recesses above where the landing skids attach to the frame, installation of the landing gear took about 5 minutes.

The Tower Pro MG930 servos went in as smooth as can be, they pop right in through the frame and small plastic pre-threaded mounting brackets for the servos are included in the HK-500GT kit. No spacers necessary. I still can't believe how much metal is used in this frame - even the stock motor mount was metal, so the upgraded mount was entirely unnecessary.

The boom installation was a bit trickier. The housing needs to come out of the frame so that the belt can be wrapped around the gear. The housing pulls apart at the center, allowing the tail gear to pop right out. The tail gear is solid, splined on the shaft so there won't be slipping issues like there were with the HK-450. The frame screws were secured with blue Loctite so it was a bit of a fight getting them out of the frame, but a little bit of patience and persistence paid off. There are a total of 8 screws holding the boom housing inside the frame, then 4 screws for tightening the boom. Make sure the belt/gear moves in the correct direction before installing the boom/tail gear housing back into the frame. There is a slot and a hole on the boom for aligning everything properly. One minor mistake with my particular HK-500GT kit was that the tail boom doesn't center perfectly against the frame due to how the slot/hole on the ends of the boom were cut, however, it's VERY close, just a small imperfection that does not require any correction.

Overall the installation has gone smoothly up to this point. Since all the threads are metal in the frame, be sure to use blue Loctite (or permatex) when tightening the screws in the frame. Photos of my progress have been uploaded.
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Old Oct 14, 2009, 04:07 AM
trex 500esp msh protos
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so, no issues so far?

edit, I am suprised that you posted the build thread in this section instead of the large heli forum as this one does not seem as well read
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Old Oct 14, 2009, 07:00 AM
Gone Flying.
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henry -

No major issues up to this point - note that I still have to "level" off the head, install the motor into the frame, route all the wiring, balance the blades, etc. The boom is generally the portion of the build of a heli that I loathe the most, the HK-450 boom installation wasn't always smooth (I've built several HK and T-Rex 450's), things weren't always lined up and I had one HK-450 kit where the slot at the end of the boom was on the wrong side, so I had to dremel out a new slot. This kit hasn't been without its imperfections, but I'll say that most of the parts are high quality, even the servo mounting brackets had metal thread inserts inside them that matched the screws provided for mounting the servos. It's a big difference compared to the HK-450 build.

I can request that this thread be moved to the larger heli forum if that would help, but from what I observed most if not all of the HK-500 stuff was in here.
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Old Oct 14, 2009, 07:20 AM
trex 500esp msh protos
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Quote:
Originally Posted by rcnewb
henry

I can request that this thread be moved to the larger heli forum if that would help, but from what I observed most if not all of the HK-500 stuff was in here.
does'nt matter at all,if your happy with it here then all is good.

sounds like this bird is better sorted than the original plastic version,I may have to get me one of these though why I need another heli I don't know
henry
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Old Oct 14, 2009, 07:41 AM
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There's always a reason to have another heli

My main reason for buying the HK-500GT was that I didn't have anything larger than a 450, and after all the upgrading and swapping of head parts with the HK-450, I was hoping the HK-500GT kit would not only give me that larger, more stable heli, but also parts that would not need upgrading down the road. So far the HK-500GT kit has lived up to and exceeded my own expectations.

All of the "upgrade" HK-500GT parts on the HC/HK website (with the exception of the carbon blades and frame), are *already* included with this kit. The head is mostly metal, and the tail assembly is mostly metal also. The nonmetal parts on the head and tail are FRN (fiber-reinforced nylon), so I don't foresee anyone needing to go out and drop $$ on upgrade parts. The good news is that HobbyCity already seems to be counting on the HK-500GT as a top seller, so they have a good stock of replacement parts already, most of which are 1/3rd (or less) of the cost of comparable T-Rex 500 parts.

I've seen the plastic version of the HK-T500 (a guy in my club bought one RTF), the metal head and tail assembly alone on the HK-500GT make it well worth the extra $16. I can't see why there would be a reason to buy a HK-T500 over the HK-500GT to save $16.
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Old Oct 14, 2009, 09:00 AM
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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.

I have two of the EXI-500 helis, one almost ready for hover testing and another about 50% complete. No problems with either kit yet. I've been using the Align Trex 500 assembly manual for reference when needed.

I agree that these shouldn't need much upgrading as the head is mostly metal. The aluminum frame may prevent some of the statis discharge problems that others with the CF frames have encountered.

RCnewb, it's great that you're doing a build thread. There's some good information on the EXI-500 thread in the Large Helis section, but you have to wade through alot to extract it.
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Old Oct 14, 2009, 09:56 AM
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I agree that the EXI-500 and HK-500GT are very similar. The nice bonus of buying from HC is that their HK kit includes the main rotor blades, whereas they need to be purchased separately from xheli.com when buying the EXI-500. The price on the EXI is steeper also, though the shipping costs from HC are most likely a bit higher so the prices probably get close in the long run. The aluminum frame could be used to cut down on static, as long as a small wire was run from the boom to the frame since the boom technically doesn't make contact with the frame.
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Old Oct 14, 2009, 09:56 AM
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Dissapointing in that unlike the 250GT this still has the metal frames and plastic tail. They have these on their web site and should have made the new GT full carbon and aliminium....
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Old Oct 14, 2009, 10:00 AM
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Agreed, no carbon frame for the 500GT. However, the head and tail assembly are mostly metal, no "plastic" in it either - all nonmetal parts are composed of a more rigid FRN (fiber-reinforced nylon) for both the head and tail assemblies. The 250GT head and tail assembly both have some plastic in it (not FRN), otherwise the ratio of metal to nonmetal parts in both the 500GT and 250GT head/tail assemblies is nearly the same. The frame is the big difference, and considering the total cost of the 500GT is only ~$12 higher than that of the 250GT, the aluminum frame makes sense. As someone posted above, the aluminum frame may be helpful in reducing the static issues that have plagued some of the other 500 kits with c/f frames. Aluminum is a decent frame material, in a more minor crash bent aluminum can often be repaired, whereas weak spots in a c/f frame will splinter and break.
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Old Oct 14, 2009, 10:33 AM
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I meant the tail cases, the 250 is all aluminum and the 500 plastc. Are the tail grips aluminm on the 500?

I can't see any plastic on the 500 head except the radius arms, is there?
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Old Oct 14, 2009, 10:40 AM
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The tail grips are FRN (a step up from plastic but not metal), so they are nonmetal as you noted. When I first looked at the 250GT, the tail grips looked plastic there, but I did a double-check and realized they were metal. Regarding the 500GT head, that's correct, the head is metal except the radius arms which are also FRN.
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Old Oct 14, 2009, 10:42 AM
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Good info, thanks... Good luck with the build, can't wait for a flight report.
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Old Oct 14, 2009, 10:48 AM
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Should have it flight-ready by the weekend. I'll post video if I get a decent flight. Expecting the Scorpion HK-3026-1600Kv motor to arrive by the weekend.
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Old Oct 14, 2009, 11:49 AM
Team Mulikow 3D
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Quote:
Originally Posted by RCForever
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.
Agreed - and I think that the EXI 500, HK500GT, Flasher 500 and Bullet 500 (that I have) are all made by Skya (actually I don't think that the Copterx is).

I had some tracking issues with mine - it turned out to be a combination of the plastic mixing arms (twisting under high forces) and the wash-out base being over-size on the mainshaft - I replaced the wash-out block with an Align one and the mixing arms with metal Skya ones and job-done.

Mike.
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