500 Size AH-64A Apache build

[F106DeltaDart]

Looks like I got lots of reading to do before I get my kit. I’m sure when I start this I might have a few questions for you.

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Sounds good, always happy to answer any questions. It’s been a difficult build, but I’ve learned a lot over 2 years of building and tweaking with it.

[Gravythe clown]

Looks like I got lots of reading to do before I get my kit. I’m sure when I start this I might have a few questions for you.

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[F106DeltaDart]

Speaking of Blades... where did you get those blades ?

From here: http://www.ehirobo.com/carbonhobby-b...ain-rotor.html

[3dzoom]

Today I worked on the setup for the mechanics. The main objective was to substitute the stock align shaft to move the rotorhead lower similar to the real Apache. I did not however, realize how much of a pain this would be. The rotorhead that I bought for this project was a custom scale Apache from CNCHelicopter, which I now would not recommend.. The first issue was that the ball links on the head took a lot of force to move, not free to move as they should. So, I decided to change out all the linkages to Align hardware. While removing one of the ball links, the screw snapped clean off, inside the threaded hole. Trying to remove this lead to the discovery of more issues, including cracked parts, and poor tolerances. So, I elected to use the Align four blade head instead. I had to cut down the tip on the DFC mainshaft to get it to fit, and shrink all of the pitch links, but I finally have something that looks a bit more reasonable. Here are a few photos of the new head and lower positioning, couldn't resist a test fit with the blades attached..

Speaking of Blades... where did you get those blades ?

[F106DeltaDart]

Thanks for the info. I have ordered the Gartt 500 Flybarless head, torque tube carbon fiber heli.

That should work quite nicely!

Over the weekend I finished piecing the Apache fuselage back together. Just needs a few paint touchups and it will be good as new! Still working on the mechanics though. Finishing up setting up the new tail rotor setup, putting on new pitch links, and getting the tail servo reinstalled and set up. Not much more time left though, will be leaving for the Southern Scale Challenge on Thursday!

[MrCollins63]

Thanks for the info. I have ordered the Gartt 500 Flybarless head, torque tube carbon fiber heli.

[MrCollins63]

Welcome to the forum MrCollins! The kit is really designed for the Trex 500ESP torque tube mechanics. It includes special side frames that lower the tail boom and a raised tail gearbox system that are likely only to fit on Trex 500s or clones of the same model. I would recommend keeping an eye on the Rcgroups classifieds for one, I've seen quite a few good deals pop up there. Alternatively, you can purchase an HK-500TT (Clone of the Trex 500): https://hobbyking.com/en_us/hk-500tt...-w-blades.html. I would personally replace the gears, mainshaft, and torque tube with align parts though. Hope this helps!

[RCjetdude]

Looking good sir!

[F106DeltaDart]

Repairs on the Apache are moving along steadily. The airframe is coming back together, and the metal gear is now installed. It was a perfect match, and actually seems to have a better mesh with the pinion. Hopefully it will be back on its own gear by the weekend!

[F106DeltaDart]

There are also a few clones for sale on ebay as well since hobbyking is out of stock: https://www.ebay.com/itm/GARTT-500FB...YAAOSwq5dcgHK-. https://www.ebay.com/itm/RC-remote-6...UAAOSwl2haJQDW

[F106DeltaDart]

Hi! I plan on building a Roban 500 size SH-60 helicopter. Which heli mechnics besides the TRex 500 can I use? Any info would be greatly appreciated. Thanks!

Welcome to the forum MrCollins! The kit is really designed for the Trex 500ESP torque tube mechanics. It includes special side frames that lower the tail boom and a raised tail gearbox system that are likely only to fit on Trex 500s or clones of the same model. I would recommend keeping an eye on the Rcgroups classifieds for one, I've seen quite a few good deals pop up there. Alternatively, you can purchase an HK-500TT (Clone of the Trex 500): https://hobbyking.com/en_us/hk-500tt...-w-blades.html. I would personally replace the gears, mainshaft, and torque tube with align parts though. Hope this helps!

[MrCollins63]

Hi! I plan on building a Roban 500 size SH-60 helicopter. Which heli mechnics besides the TRex 500 can I use? Any info would be greatly appreciated. Thanks!

[F106DeltaDart]

I will try, but no guarantees. Trying to get a few other projects ready, and not sure if I’ll be able to get the Apache back together by then.

[RCjetdude]

Nice! Will you have it with you at the Southern Scale Challenge?

[F106DeltaDart]

Finally received my Aluminum gear this morning, and I can’t wait to start getting the Apache back together. The gear came out great!

[F106DeltaDart]

After a lot of back and forth, I finally found a place willing to make me a gear in aluminum. This should be able to hold up to the stresses of a 4 blade head much better than the stock nylon (of which I have stripped 3 gears so far). It is a two phase operation. First, the gear has to be machined without the teeth on a machining center. It will come out of that machining looking something like this:

Then, I take the gear to a gear specialist that will cut in the teeth. Hopefully, the Apache will be flying again soon with a new aluminum main gear installed.

[F106DeltaDart]

Finally got around to working on the rest of the tail rotor. I had 2 main issues with the CNC helicopter tail rotor I’ve been using. Problem #1 was vibration. The “barrel” that slipped over the tail shaft was not machined 100% correctly. When rotating that rotor by hand, there was a slight, but noticeable wobble at the end of the barrel. Problem #2 was a lack of full throws. The tail rotor only went to +/- 25 deg pitch or so. Most tail rotors can go +/-45 deg, and this definitely contributed to my tail authority issues.

The solution was to start from scratch, and build my own “cascade” type tail out of 2 stock Trex 500 tail rotors I pressed the bevel gear off of the stock tail rotor shaft, and pressed it on to a longer 4mm shaft. I also will be drilling a pin through the gear to pin it to the shaft. The two tail rotors are linked together with Trex 450 ball links. The result is balanced tail rotor with +/- 45 deg of pitch. And, it uses stock Trex parts, so it will be easier to repair if anything happens. One step closer to getting back in the air!

[F106DeltaDart]

Finally getting back to this project after a few months. The new landing gear and main gear are hopefully finally on the way here.

In the mean time, I wanted to try to tackle some of my issues with intermittent tail rotor authority. The first item on the list was reversing the direction of tail rotor rotation. For the most efficiency, your forward-most tail rotor blade should be rotating up into the rotor wash. The opposite was true on my model due to my angle gearbox. So, I decided to switch up some of the internal gearing, by moving the bevel gear that turns the drive shaft from the top to the bottom side. This involved very carefully pressing off the stock gear, and securing it on the other side with some JB weld and a pin. It’s nice and solid now, and the tail rotor direction is correct!

This is only part 1 of the fixes. I also have a few pieces on the tail rotor itself that I want to change that I’ll get to next..

[Hardway]

FUN FUN Helicopters!!! Sorry. A real bummer for sure... Sometimes they have mysterious things happen for no apparent reason... Usually after you have spent a good year tuning them to perfection with zero glitches.... Then they break!!! :P

[F106DeltaDart]

Well, I took the Apache to the Texas Scale Championships on Saturday this weekend, and things could have gone better... First flight went awesome, the chopper performed perfectly and I completed all of the maneuvers without too much difficulty. The second flight however, did not go well. I was climbing into a wingover turn, and heard the dreading shredding noise of a main gear being torn apart. Power dropped almost immediately, unlike last time where I was level and at altitude, I was pointing downwind, with the nose aimed at the sky at about 50 ft. I was able to get the bird level, but couldn’t recover enough RPM for a successful autorotation. Keep in mind this is a 7.5 lb heli 500 size bird, so she drops like a brick without power. It hit level, and in the tall grass about a foot off of the side of the runway.

Damage was admittedly nearly not as bad as it could have been. Since pretty much all the rotor energy had been expended, the head and blades are undamaged. The worst is a few large rips in the fiberglass, and a broken gear strut. Otherwise, it was just the glued on detail pieces that came off. It will fly again, but the main gear really concerns me. There was no clear point of failure like last time. Pinion was still aligned properly, one way was tight, and it performed the exact same maneuver before without issue. I’m starting to think that looking into a custom CNC gear might be a better way to go. Or, just sticking to level flight and low torque maneuvers.