500 Size AH-64A Apache build

[F106DeltaDart]

Over the past 3 months I have flown each of the new tail pinions with next to no difference in tail performance. This left me incredibly confused, and I had spent a while trying to experiment to see if there was a weird aerodynamic issue going on. Then yesterday I finally had the breakthrough that I needed.

For a while, I have had a tail servo (MKS X6 HBL599) siting around that was planned for a Roban EC135. I never pulled the trigger on it, so it was just sitting around unopened. I figured just to eliminate the servo as a potential issue, that I'd try installing it. The 22T tail pinion was also installed. I figured this would do nothing. I already had a stupidly oversized tail servo.

Original servo: MKS DS8910A+, 6V Stall torque of 2.6 kg-cm (I use this in all my other 500 helis)
1st Upgrade servo: BK 7005HV, 6V Stall torque of 8.4 kg-cm (This was in the Apache for the last several years)
2nd Upgrade servo: MKS HBL599, 6V Stall torque of 30 kg-cm (The nuclear option!)

I took the mechanics out for some flights and was shocked to find excellent tail response! No more slow, faltering pedal turns. I guess that the cascade tail really requires a ton of torque. I'm sure I could get away with less, but I'm certainly not messing with it now! Next step is to try it with the fuselage installed, and in a bit of wind.

[F106DeltaDart]

Well, I think I may have finally nailed down why I've been fighting tail issues with my Apache for so long. I finally took it apart and got the ratios of the stock gearing. 112T Autorotation gear and a 31T tail pinion makes for a 1:3.6 Main/Tail ratio. I suspect the reason why the pilots using the stock belt drive have not seen these issues, is that the front drive pulley is being used as a a 2nd stage gearing to get the tail ratio higher, and may have a higher tooth count than the tail pulley. I can't confirm this, as I got rid of the belt drive parts years ago. But with a 1:3.6 ratio, everything I've seen makes perfect sense.

This leaves me with 3 options:
- Convert back to belt drive and find the original drive pulley
- Find a different front tail drive pinion (Ideally 25-22T for ~5:1 ratio) - Runs Risk of over-stressing autorotation gear
- Direct motor drive to torque tube input - e.i. miniquad motor to independly drive tail shaft.

I did some quick searching for pinions knowing that the stock trex 500 Auto gear is Mod 0.6, and found some Tamiya truck pinions that might work.. https://www.amainhobbies.com/search?...+0.6mod+pinion

For now, that seems like the easiest change to make. I'll start with the 25T and decrease from there if needed to keep stress low on the autorotation gear. Should receive the gears this weekend.

[eawings]

I used our MKS HV9780 Mini Tail Rudder servo Alpha.

[Alpha]

Which Torq servo did you use for the tail?

[eawings]

I would like to show some photos of our 500 AH-64 conversion build. Any questions. let me know. This a Belt Drive tail unit with 4 bladed tail rotor from Bangood China, Align 500 4 blade Scale main Head, Torq Mini Servos with Castle 80A ESC, Bavarian Demon 3X, Scorpion HK3226-1400KV Motor and MKS HV9780 Tail Rudder.

[RcJet59]

Right on! thanks man

[Gravythe clown]

Try PKM on Facebook. Be ready, they aren’t cheap.

https://www.facebook.com/phukethobbymodel.shop/

Gravy

[RcJet59]

F106DeltaDart, thanks for getting back to me. I'll just wait and hopefully someone starts making more or make my own.

[F106DeltaDart]

Unfortunately, the gearbox setup I used is discontinued. Used to be made by a company called smartmodel: http://www.electric-rc-helicopter.co...ive-t5433.html. I had to mode the side panels to get the higher angle required for the Apache tail.

[RcJet59]

Hello gentlemen,
I have been reading this thread to get familiar with the building of the Apache. I recently bought one (Not the RC Aerodyne scale fuselage kit) but a "copy" of it? who knows. Looks familiar but it has some unscaled looking bumps to fit the main gear. I wish I had done research on it before pulling the trigger. Unfortunately it didn't come with the side frames that lower the tail boom and raised tail kit. I bought everything (Torque tube) I needed to try and build it but one of the parts (raise tail) will not work with the Apache. The tail part is meant for theUH-60 500 Scale & AH-1 500 Scale. I know F106DeltaDart used a Torque tube drive setup? Can you point me to the one you used? Or even the tail conversion. Any help is appreciated. Thanks guys. Happy flying/ Building.

This one looks similar to the one I bought. I found this picture on google.

[Gravythe clown]

Holy cow, that’s a heavy bird. Yeah your thicker cord blades hopefully help.

Gravy

[F106DeltaDart]

From all of the discussions around weight, I realized that the only time I ever measured flight weight for the Apache was on an old (and very problematic) kitchen scale. I ended up throwing it out a year later as it was more or less worthless. So, I got out a newer scale to hopefully get a more accurate handle on the weight. All up, it came in at 9.5 lbs, which explains a lot. Likely both the tail rotor issue, and the gear stripping. In other words, keep your Apaches light! This weekend I’m going to try some larger chord RT 430mm blades if weather holds. Their wider chord will hopefully take the weight better and create more lift for less torque.

[PawPaw]

I’m belt drive. So far, I haven’t found any issues with my stock setup and F106 designed 4 blade X tail. My flying style has been ultra conservative..read that as CAUTIOUS...as I test and gain confidence in the method I used to attach the tail belt pulley to the longer shaft needed for the 4 blade setup. Issues may show up when I fly it harder but right now I’m predicting it will be ok. Also, I do fly with FBL governor mode instead of ESC governor which may show some difference.

[Gravythe clown]

Yeah I would have expected yours to be more than just 0.4 lbs. with everything you have added.
I definitely think the TT drive is not helping your gears from stripping. But I also wonder if lower KV lower pinion and higher voltage isn’t amplifying the TT torque issue
Your setup is not working as hard as mine which will allow it to spin up fast and with more available torque, where mine would stall out quicker, rather than push through.

it will be interesting to see where pawpaw’s shacks out at. He’s using same power set up a you but I believe he’s keeping belt drive.

Gravy

[F106DeltaDart]

I wasn’t going to add this video as it was a quick up and down. I forgot to do my (need trim test) first, turns out 3 clicks of forward into the microbeast plus was the magic number. We didn’t recorded them but the next two flight were locked in.

https://youtu.be/UsoDerFVEwg

I too am trying to figure out why you are having issues with the main gear stripping, so I’ll just post my info again.
1210kb scorpion
16T pinion
4s power
1900rpms
10 second spool up from off to 50% of its way to 1900
another 10 spool up from 50% to its resting point around 1900rpm.
I’m using the simple governor setup in the castle creations

maybe somewhere in all that is the answer.

Gravy

Interesting. I'm using:

900kv Scorpion
14T pinion
6S Power
1900 rpm
25 sec slow spool
Set RPM mode (castle talon 90)

The only thing I can thing of for the gears stripping, is the torque tube conversion. The torque tube instantly transmits higher torque loads directly to the drive gears when it has transient loads. The belt drive has a bit of give, and can absorb those impulse torques. Would certainly explain why the gear stripped completely the last 2 times that I tried to do a stall turn. I'm pretty convinced that my model is heavier as well. Between the torque tube conversion, all the nose weight to balance it, the 3D printed cockpit, and servos for the tail, TADS, and gun, its got to be heavier than the stock model.

[Gravythe clown]

I wasn’t going to add this video as it was a quick up and down. I forgot to do my (need trim test) first, turns out 3 clicks of forward into the microbeast plus was the magic number. We didn’t recorded them but the next two flight were locked in.

https://youtu.be/UsoDerFVEwg

I too am trying to figure out why you are having issues with the main gear stripping, so I’ll just post my info again.
1210kb scorpion
16T pinion
4s power
1900rpms
10 second spool up from off to 50% of its way to 1900
another 10 spool up from 50% to its resting point around 1900rpm.
I’m using the simple governor setup in the castle creations

maybe somewhere in all that is the answer.

Gravy

[F106DeltaDart]

Glad to hear everything is flying well Gravy! I’ll have to admit I’m a bit jealous 😁. No more tail issues and no shredding gears is great news. I took my Apache out again on Saturday, this time fitted with a brass pinion and the aluminum main gear. Results were good and showed no real signs of wear. The tail performance though, is unchanged. A 6 mph winds had me at full tail rotor inputs multiple times to stop the tail from blowing out entirely. It has to be due to some combination of my higher weight and changing the tail to the other side. I’m going to do some more tweaks to headspeed and I might try changing out the blades as well. I can’t help but wonder if the gearing of the belt drive was a bit better than my torque tube setup. Wish I could be there to see an apples to apples comparison of both Apaches.

[Gravythe clown]

Well the restraining order is very clear on what you can and can’t do while in a supervised visit.

it’s going to take some time to get that video of yours done. Got some great slomo stuff to slice and add. Even the sound in the slomo is great.

Gravy

[DCORSAIR]

Wow, nice pics of them together, next time we might get someone to record a flight together in the air, glad you came over and you got that 500 Apache dialed in nicely, not one vibe what so ever, your hardworking building skills and 3D printing skills are really showing off in that Apache, and that Cobra looks awesome as well, it's still my favorite, I did notice you kept a close eye on it when I was touching her and adjusting those blades.

[Gravythe clown]

Went flying today at DCORSAIR’s place. We got the boys together.
my 500 AH-64 flew great. I got my dialed in after the 1st quick flight which I’ll post later along with his 700 AH-64.

or mine I added 3 clicks of forward stick trim to the microbeast and she flew on rails.
I got three more flights in her or a total of 12 minutes. 1st flight was quick make adj then send her.
after that it was flown hard and put away wet.
gears still look good, I’m not seeing any signs of wear yet.
looks like we might have figured out my shake issue on my cobra. I’ll know for sure after some adjustments and post in that thread.

good day to fly the Apaches though.

Gravy.