500 Size AH-64A Apache build

[PawPaw]

If I read everything correctly, it flew well before you modified the tail transition unit with the added bearings?

[F106DeltaDart]

Yeah F106 switched to Torque tube, I’m still belt drive.
yes I’m using the brass gear. Alas I’m now having this issue with mechanics outside of fuse. So at this point it’s fully a mechanical issue.
I just pulled out the whole tail drive system from the main frame back.
the belt is supper smooth now, the control rod from the servo all the way to the tail control arm is smooth.now now any tightness left is the pitch control on the tail shaft and the blade grips.
so I’m piercing together a new tail section to try.

I also ordered new aluminum pulley shafts as I found a crack on the plastic one.

I’ll update after some more testing.

Gravy

I might still have the original belt unit that came with mine if you need it.

[Gravythe clown]

Yeah F106 switched to Torque tube, I’m still belt drive.
yes I’m using the brass gear. Alas I’m now having this issue with mechanics outside of fuse. So at this point it’s fully a mechanical issue.
I just pulled out the whole tail drive system from the main frame back.
the belt is supper smooth now, the control rod from the servo all the way to the tail control arm is smooth.now now any tightness left is the pitch control on the tail shaft and the blade grips.
so I’m piercing together a new tail section to try.

I also ordered new aluminum pulley shafts as I found a crack on the plastic one.

I’ll update after some more testing.

Gravy

[F106DeltaDart]

Sounds suspiciously like the fuse tail fin is blocking the airflow, but wouldn’t think it would that much. Are you using the brass tail drive gear that came in the kit? I remember F106 had tail holding issues and he figured out he was using the wrong gear.

There is definitely an issue with tail blockage on this particular airframe. I’ve always had tail authority issues with this bird and have tried everything in the book to minimize them, but I still regularly have tail issues flying in wind. No oscillations though, just loss of tail rotor effectiveness (LTE).

The first issue I had was the tail pinion. I ran a different tail drive pinion (one that came with my torque tube conversion), and I couldn’t even hover without the tail blowing out. The one included with the kit was a lower tooth count and provided more tail RPM, and was enough for successful hovers. I ended up slowly increasing head speed all the way to 1900rpm to get enough authority for basic maneuvering.

The second issue that I had was tail travel. The original tail I was using (made by CNChelicopter) had much more limited travel than a normal tail. I modified it and switched to another much stronger servo (BK-7005HV). I also switched to the largest tail blade that I could find that still provided tail clearance. Again, all this improved things, but I still experienced LTE even in light winds.

The next thing I tried was switching tail rotation direction, and making my own cascade tail rotor from 2 stock Trex 500 tail rotors. For efficiency, the forward-most tail blades should rotate up into the rotor wash. It’s not a huge efficiency gain, but I was looking for anything that I could get. The custom made tail allowed for a full +/- 45 deg travel on the tail, which also helped.

After all of this effort, I can fly without issues in very low wind (up to ~7 mph). In higher winds, a quartering tailwind or a direct crosswind can still cause LTE. With some minor effort, it’s easy to recover from this. If the tail blows out, reduce collective and get some forward speed. It will lock back in quickly when power is reduced. However, predicting where it will happen gets difficult in more wind. I’ve had it happen flying figure 8s in 15mph when it gets at just the right spot and speed. Hopefully this helps a bit, but it still isn’t exactly a solution. I still think the model needs a higher tail ratio but I’m out of ideas from simple changes to make.

[PawPaw]

Sounds suspiciously like the fuse tail fin is blocking the airflow, but wouldn’t think it would that much. Are you using the brass tail drive gear that came in the kit? I remember F106 had tail holding issues and he figured out he was using the wrong gear.

[Gravythe clown]

Yeah it’s prospective. There is a nice gap between the top (entering) belt and the bottom (returning belt bearings). The whole drive system is very smooth now, where in the past it was always tight.

took extra pics but really hard to see the gap in the pic but it’s there and about 2mm.

just checked my tail control linkage travel free from servo. And it’s smooth. My servo is one I’ve used (same brand and model number DS525M 333hz 1520 pulse) for my cobra. Also I flew several flight with the mechanics before first flight in the Apache fuse. the tail was dialed in with my gyro setting at about 65% (heading hold). Now it’s still not controllable at 100%.
im going to try and change the servo out first, other than that I’m not sure what else to check, I’ve going through the setting a dozen times.

Gravy

[PawPaw]

Maybe it’s my perspective of the pic, but looks like the belt is in contact with both sides of the lower bearing and is getting pinched between the upper pulley? I’m not as far along as you, but I just ran my mechs up to 1700 for a few minutes and my tail just gets lukewarm. Feels like it’s the belt, not the pulley. What 4 blade tail unit are you using? I bought a Chinese one off Ebay and still not sure if I can even use it....blades don’t track 100%....and will prob need to fab new links if I don’t trash it first.

[Gravythe clown]

Pawpaw take a really good look at the tail transition piece. After making my metal replacement for the control rod setup, I noticed a bunch of heat today after a test run up. Don’t like how any of that is setup. So I replaced the whole pulley setup with 4 bearing. What a difference that made. The whole tail drive is like silky smooth now.
However every since I have put the mechanics into the Apache and tried to fly it, the tail is uncontrollable. Just not sure what the deal is now. It flew great when I was first setting up the mechanics but now it just won’t stop waging,

Sometimes I just feel as though I’m not meant to fly this bird.

Gravy

[PawPaw]

I just plan to firm them up enough to keep the stop screw from bottoming out in the slot when sitting under its own weight. Just a few mm’s will do the trick I think. Not gonna risk stripping out the alum threads removing that steel grub screw, ‘tho.

[Gravythe clown]

I left them stock. I found on the 700 it was better for them to be weak and compress. It definitely helps in the what I call danger zone. The time between fully siting on the ground up until both wheels in the air.

Gravy

[PawPaw]

Yeah, I’m thinking I will either find a stiffer spring or try putting a short plug in the strut to firm them up. Depends on how tight those grub screws are in the stop slot...aluminum and steel don’t mix well.

[F106DeltaDart]

Hey F106 and Gravy....either one of y’all do anything to the LG springs? Seem pretty weak.

I just left them stock, but they are definitely on the weak side. They sit fully compressed on the ground.

[PawPaw]

Hey F106 and Gravy....either one of y’all do anything to the LG springs? Seem pretty weak.

[DCORSAIR]

Got my piece made tonight. I found a piece of metal at work that was the same thickness ( or close enough) as the original piece. Marked it up using the original al as a template, drilled out the holes then cut and grinder it into shape. It’s a little bigger size wise but the holes are on mark. It’s also strong. So now I just need to uninstall the mechanics again and change out this piece. This is where I am glad I used hot glue to glue The wooden tail tube holder in. A little if alcohol and the glue will come right off.

Gravy

Looks like that will work, good idea on the hot glue, in fact that is something I need to purchase for my shop, I heard hot glue works great for certain things, will have to give it a try...

[Gravythe clown]

Got my piece made tonight. I found a piece of metal at work that was the same thickness ( or close enough) as the original piece. Marked it up using the original al as a template, drilled out the holes then cut and grinder it into shape. It’s a little bigger size wise but the holes are on mark. It’s also strong. So now I just need to uninstall the mechanics again and change out this piece. This is where I am glad I used hot glue to glue The wooden tail tube holder in. A little if alcohol and the glue will come right off.

Gravy

[PawPaw]

Thanks, Gravy. Good info. Haven’t progressed that far yet....still waiting on 4 blade tail hub from China.

[Gravythe clown]

All put together today. Decided to hot glue the tail support block in instead of epoxy. I did it so it can be removed later if needed. Glad I did, as it needs to come out again. The tail control arm transition plate is bad design. I thought I fixed mine but was wrong. I’m going to make one out of metal so the hole won’t oblong. The hole section is just sloppy. I knew it was going to be an issue, and should have just built the metal one to start off.

https://youtube.com/shorts/t0gcPiwx9B8?feature=share

Gravy

[Gravythe clown]

Actually the Apache installs really easy. I have them in and out a few times. It’s the Cobra that will require the colorful vocabulary.

Gravy

[PawPaw]

Can’t wait to hear the colorful language.

[Gravythe clown]

Well time to put the mechanics back in.

Gravy