Roban apache 700

[Granpappy]

Seeing those flats on shaft and just a grubscrew holding it on gives me the shivers every time i see it

Head speed will be a lot lower on a 4 bladed heli I guess, but having the feathering shafts held in place with grub screws is pretty crazy. Are there any reports of blades being thrown on these aircraft?

[chopper1]

I don't think anyone has had one throw a blade.But I have seen the feathering shaft move in flight which obviously puts the head way out of balance and creating very bad vibration.They may have a low head speed as you say but theres still a lot of force created .
The reason I fitted a roll pin through each shaft instead of just drilling through the existing grub screw hole and fitting a bolt is because this way you can assemble the head in the normal way intended so you have zero play in the blade grips.Then nip up the grub screw to hold the feathering shafts in the correct position.Then remove the blade grips to aid holding it in a vice to drill for the roll pins.
Roll pins I used were 3.5mm diameter by 14mm long .
You must run a very low spindle speed on the drill as the shafts are very hard and will otherwise burn out the drill very quickly.I used 300rpm.

Hope this helps .

Ian

[ChrisB]

No not sure if any have totally let go inflight(but there aint much of a lip there),as Ian says we have seen them slip inflight causing very bad vibes,thats enough to potentially destroy the heli in itself before you could get it on the ground,hence Ians modification.

Maybe the designer was smoking something while doing this bit

But we have been told that Roban are redesigning this part and our member with it said he will be pressing for the new parts FOC in spite of this fix.

That aside,it is indeed an awesome looking model for sure

[Granpappy]

Yes it is an awesome model and I would love to have one.

I've found with grub screws that sudden forces on whatever they are securing can strip the grub screw threads and they pop out.

[ChrisB]

Just wondered if anyone with the Apache can comment on their tail performance,our Nevs has got a really vague tail on it(thinks old Futaba mechanical gyro) it has no holding power and continues on after stick release or it stops loosly and runs back the other way.

The model has some low frequency vibes i would guess main rotor rpm related but V Bar log in hover shows good health thruout and max vibe level meter after flight is barely a third of the way up.

We tried various headspeeds and gains from low to maximum possible on V Bar and nothing cures it,stop gains etc also dont help.

Myself and Ian flew it and agreed the tail just has no hold whatsoever,i have not seen a Vbar with a tail this loose before.

From a mechanical point,everything is very smooth and free running on the tail pitch control mech,there is no sloppiness and no obvious mechanical cause for it,Nevs put it together well and it all looks tickety boo.

We are wondering if trying longer tailblades will help(115s) as the tail fin is huge and maybe blocking its effectiveness but this would have been picked up at design stage.

We will be taking it to Southern Helifest next weekend so hopefully the SCHC boys may shed some light on it.

Ian is going to chime in later but for now we are keen to hear about others tail performance.

The only thing i thought about afterwards is if any of the tail grips are locking up at running speed.

Ta

[PHIL1967]

I think my mate lee will be able to advise you a bit better than me on gains n such but he set my Apache up from scratch really on a beast x it took off on its maiden and flew itself tbh and the tail felt fine even thou it's only had one flight it felt fine ,head speed on mine is around 1150 rpm spoke to the very helpful Jon copplestone the other day and his Apache is running 1250 rpm he hasn't mentioned any problems with the tail only the grub screws in the undercarriage so it sounds like a gyro problem , how bad are the vibrations bud

[ChrisB]

Cheers..

The vibes are low frequency and quite heavy and being shown in rocket pods, and both fins on the tail, so not ideal and an obvious culprit here.

I have found before that swapping blades around on the head between grips can sometimes cure a head related vibe, there is no obvious mechanical issue with Nevs heli to suggest whats causing the vibe.

We didn't do it today but I asked him tonight to check that the tail gyro sensor is actually working correctly and not gone bad on the V bar and that the setup stages are all done correctly(going back to basics).

As the logs files are clear of vibes I will ask Mikado if they can advise any further, but maybe,if its just the fuselage items vibrating themselves rather than because of a mechanical issue, these may not be getting transmitted back to the sensor.But if the sensor is seeing them,even if log says otherwise then for sure that could be the culprit.

[PHIL1967]

Believe it or not an out of balance main blade on my Apache caused a lot of problems with vibrations on the fuz and particularly the tail these blades are paired by the way you will see how if you get the centre of gravity of the main blades you will see how far apart they are , theses are defiantly paired you said it in your 2nd paragraph mate , I spent a little time stiffening my fuselage with carbon plus balsa wood and it seems to have worked a treat and of course balancing the blades goes without say , hope this helps

[chopper1]

Thanks for the feedback Phil1967.
I no Nev did check the balance of the main blades before we fitted them and they were good. Dont think he checked the balance of the tail blades though.
Interesting that you stiffened up the fuzz which helped reduce the vibes.

The good news is the mod I did to the head block has worked a treat.We feel a lot safer with it now and the head runs very smooth now.Just this tail to sort.

I am hoping that Nev finds a fault in the gyro sensor to be honest as that would explain all the issues.
Like Chris B says it flies as if there was no gyro on the tail and any changes to the gains or head speeds have any effect .
Fingers crossed that we can see others flying them at south coast helifest next weekend and see if they can shed some light on the issues.

Ian

[PHIL1967]

I'll get a few pictures of the carbon I fitted on the vertical fin tbh it was really weak around the knuckle at the base Al dig it out n get some pictures up

[PHIL1967]

You can see the carbon cloth on the tail also a few more ribs fitted with sticka flex which is removable with a little persuasion with a scalpel the front was done with a sheet of balsa approx 75mm x 13mm shaped to fit the inside of the fuselage from the top of the wing to the top of the fuselage just behind the motor , the rocket launchers on both sides was stiffened with a strip of carbon glued into both sides using epoxy resin also worked a treat it isn't very scale but tried to hide it as much as ,here's a few pictures

[chopper1]

Thanks for the pictures Phil, thats very helpful mate and makes a lot of sense.

Ian