250 heli build help - copterx 250

[Krager]

Originally Posted by bazsound

something says to me this is no where near 5000rpm just doesnt sound like its screaming.

5000 rpm sounds pretty screaming. I'm using a 4000 Kv motor on 3S with stock gearing to run 4500 rpm governed. About the most I can get with any overhead for the governor is 4800 rpm. It sounds like a healthy rpm to me, like it's definitely moving out. At one point I tried 4800 rpm and it felt too intense for my skill level, though I will crank it up that high if and when I feel I can utilize it.

It depends on your motor Kv, but if you're running the stock 8:1 with a typical 3600 Kv motor on 3S, you wont get a whole lot more than 4500 rpm at full throttle with neutral pitch. Then it will fall off a few hundred rpm when applying maximal pitch. Generally with no load you won't see motor rpm any more than 95% of nominal battery voltage times motor Kv. However even at neutral pitch there is still some load slowing the motor down a bit.

[bazsound]

im running a 3400kv motor, i think hte calc i was using was very optomistic, used another calc which came just shy of 4000rpm which seemed a bit more likely.

I flew the heli recently in very little wind and did some aggressive pitch pumps at the time i didnt think it was that much but reviewing the video the heli shot up like a rocket with what sounded like a normal amount of head bogging for being so agressive on the collective, surprisingly the tail did not blow out.


unfortunatly for unknown reasons the heli crashed after some moderate paced back and forward flying to test tail stability in forward flight.

after deciding to bring it back in for further tweaking as a slowed down the heli suddenly started to drop at an angle, i gave it a healthy bump of coollective and nothing happened and it hit the ground.

Broke feathering shaft, stripped teeth on main gear, broke landing gear and dented the metal tail tube.

The plastic ball links also came of the swash to blade grip links, leaving the both plastic bits on the blade grips, im unsure if this was the cause of failure, or a result of the crash. Im using the align links which are tighter than the stock copter x links so probably that was it (the copterx blade links when i tippted the heli off the links just popped off)


Being an inexperienced flyer i would have expected it to be dump thumbs but this was a sudden loss of altitude, like i just gtave it negitive collective.

My collective ended up being full positive which should have sent it flying upwards at an angle.

unfortnatly didnt catch it on video.

Possibly the gyro glitched out ? couldnt have been signal loss as i was only 10m away. im guessing the gyro glitched out and twitched the servos. Ive seen it do it while connected to the usb programming cable.

I changed my foam tape to mounting tape which was infantly better, 2 layers. probably have around 10 flights using this tape (aswell is tweaked gyro settings) and apart from the bounce was much better.


So will put in order for blade grip bearings and CF tail tube. The blades surprisingly were undamaged apart from some grass marks. No cracks no chips. Ill rebalance them and closely examine them incase i missed something.

i already have a spare feathering shaft and spare mainshaft, so will change the mainshaft aswell, and obviously the maingear.

kbar should be here in a few days and hopefully the 0.07s metal gear servos i ordered aswell..

[bazsound]

Found that i did get video of the crash and after reviewing it, collective did respoind but shot the heli at an angle. (sun was in the way making it hard to see)

heres a few videos of it flying and then the crash

https://www.youtube.com/watch?v=RZ4E...iSOPae&index=3

https://www.youtube.com/watch?v=Vjsy...iSOPae&index=2

https://www.youtube.com/watch?v=ZuBv...iSOPae&index=1

Edit:

kbar arrived :-)

Need to figure out best way to mount it. i know i can enlarge the lower frame with washers, i may do that at a later date.

Mounts on the side fine, though the provided pads didnt seem very sticky, first one idnt stick very well and kbar just fell off, 2nd one i let sit for a minute on the kbar, then firmaly pressed it onlto the side frame and held for a minute. its holding

really want to velcro strap it but theres a clearence issue with the main gear, the velcro will rub on the maingear...

Just need my replacement parts to arrive.

edit edit:

did a quick search for sudden drops of altitude gave a few things i didnt know off.

Mainly RF interference, particularly with alot of CF parts... also the motor itself can produce alot of interference

One thing i noticed in the video is that there seemed to be some strange interference.

Is my motor producing excessive RF noise? .....

[navigator2011]

Originally Posted by bazsound

Mounts on the side fine, though the provided pads didnt seem very sticky, first one idnt stick very well and kbar just fell off, 2nd one i let sit for a minute on the kbar, then firmaly pressed it onlto the side frame and held for a minute. its holding

really want to velcro strap it but theres a clearence issue with the main gear, the velcro will rub on the maingear...

This is concerning ... I recommend that you use Align's gray 3M mounting pads. I have used them on my 250, and they are rock solid. Also, as you may know, it is a good idea to clean the bottom of the receiver and the mounting surface with alcohol before applying the pad. If the receiver falls off during flight, that will be a disaster, and using straps runs the risk of directing vibes to the gyro.

I don't remember if I shared with you a write-up about my latest 250 build--it has some pics of mine with an AR7200BX mounted on the side of the lower frame.

Crafting an Align Trex 250 DFC with AR7200BX and CC Talon 25 ESC

[bazsound]

Originally Posted by navigator2011

This is concerning ... I recommend that you use Align's gray 3M mounting pads. I have used them on my 250, and they are rock solid. Also, as you may know, it is a good idea to clean the bottom of the receiver and the mounting surface with alcohol before applying the pad. If the receiver falls off during flight, that will be a disaster, and using straps runs the risk of directing vibes to the gyro.

I don't remember if I shared with you a write-up about my latest 250 build--it has some pics of mine with an AR7200BX mounted on the side of the lower frame.

Crafting an Align Trex 250 DFC with AR7200BX and CC Talon 25 ESC

The 2nd pad stuck better after leaving it a while, but i was able to get the esc loose after a minute of wiggling. not impressed with the kbars provided mounting pads, maybe thats why there are 6 of them included because there rubbish.

Ive got mounting tape which i used to fix the cx3x200 gyro to the side, that stuff sticks welll. I used a velcro strap to ensure the gyro was solid. I used a strip of soam on the velcro strap so that vibration wasnt transmitted.

But wont be doing that as i discovered the velcro strap is very close to the main gear.

I should hopefully have replacement parts tomorrow, good thing about this heli is parts are availible in the UK.

the cx gyro i may have some fun , build a homemade quadcopter for when you want to fly something that might not quite do what you expect lol

Ive read about static issues. ill keep the belt lubricated (have silicon spray)

[nflanagin]

Could be - or it could be your radio and setup. If you lost signal and failsafe wasn't setup, it might head straight into the ground. Was the heli pointed in such a way that it blocked the receiver/antennae? Usually, that close though, does not cause a problem - unless it's clone stuff.

What radio and receiving?

[zzyzx_cm]

Cx3x2000 def needs to hit the trash that thing is a horrible waste of time. That cx9g servo on the tail will piss you off as well. Ds76t is less than 20 amd easy to come by at a lhs. The 3m extreme outdoor mounting tape is 7 bucks a roll at home depot and is tits.

[bazsound]

Reciever is an orangerx 610 not exactly known for distance but im not flying this close than i would my v977. The reicever is on the gyro tray with both ariels sticking out, one points straight back towards the tail and the other out the side.

Not sure if maybe it should go on the other side, so 1 airial is poiinting up and the other out the side.

It waasnt loss of signal i dont think. headspeed didnt drop, i havnt got round to properly setting the failsafe (been trying to find a manual on how to do it) i checked what happens on loss of signal and the motor doesnt cut out but runs at low speed.

im also running higher power 150mw.

The only thing i can think of is the gyro glitched and delayed the collectrive input. ive read of a few people observe cyclic twitches like the gyro was resetting.

oh well, got my kbar now. might upgrade the reciever to a satalite.

Edit

kbar installed and gone is the lack of stick resolution to swash movement, i know have full stick range with swash.

Im still having to be on the 3rd hole from centre on cyclic to reduce throw, at 80 on the collective in vbar, i get about 12 degrees pitch 1 way and 14 the other. and on cyclic i have 10 degrees at the 80 setting.. at a guess the copterx a flybar clone with an fbl head (a very detailed vbar series of videos explained the problem with converting flybarred helis to flybarless and explained that it works well for flybars but for flyberless results in too much mechanical gain for FBL systems)

So i guess ill have to live with it, unless my servos that are coming have less throw.

Spent most of the day slowly rebuilding it, making sure all the servo links are close to what the manual calls for. couldnt get close enough 90 degree arms so had to use trim (and also some trim to get 0 pitch).

spent a few hours setting up the gyro and called it a day. So far no glitching, no twitching no strange behavour.

we have hope yet...

[bazsound]

Originally Posted by zzyzx_cm

Cx3x2000 def needs to hit the trash that thing is a horrible waste of time. That cx9g servo on the tail will piss you off as well. Ds76t is less than 20 amd easy to come by at a lhs. The 3m extreme outdoor mounting tape is 7 bucks a roll at home depot and is tits.

Yeah as soon as the kbar arivved it got ripped off, i may use it to build a quirky quad.

Ive got some turnigy servos coming, mainly to replace the cyclics. there much faster at about 0.07s at 4v i think. Still not quite fast enough for the tail but a damn site better than the 0.17s servo thats in it.

that should get me in the air for mild learning doing what your supposed to be doing while learning to fly and not what you do when you have a micro that can take a beating.

can you get the washers that go between the blade grips and rotor (the very thin one that sits between inside grip bearing and rubber dampner) 1 got lost in the crash along with a bearing, which seams to happen every time i snapp a feathering shaft so far.

align UK feathering shaft comes with 2 shafts but only 1 set of washers.

I still had 1 of the copter x washers but this is much thicker than the align washer. align washer is 0.2mm thick whereas the copterx washer is 1mm thick

edit:

Added some pictures to show progress aswell as the geometery issue with the servo to swash links.

2 of them actually look pretty close to 90 degrees but one is much larger than 90, maybe i can move the servo horn down and icnrease the length of the arm if it doesnt need to go down too much

[Toocool4]

You don’t take very good care of your Hi-Fi do you?

[bazsound]

Originally Posted by Toocool4

You don’t take very good care of your Hi-Fi do you?

it was given to me, and is only used to power a set of Studio Monitors, pretty much the only thing going in is my computer.

Anyway, i got it all setup and trimmed out. fired up the vibration motitor.

Spooled up, yikes horrible nose have i stripped teeth on the pinion? Noppe grub screw is loose. So fix that and sounds normal again, but there is lots going on in the vibration montiro. Big one around 90hz and the smaller ones further up.

:/

vibration currently sitting just under 3000 at +70 (devo range, cant remember what that is in %) headspeed might actually be a bit low.

But tail wagged baddly at the suggested 40%, fast wag probably 10-15 degrees either side . reducing it to 20% helped but it was nowhere near as good as the copterx gyro.

couildnt get it to hover, didnt feel very connected and was pretty much mushy, like the copterx gyro until i increased the cyclic gain (its at the recomended setting for a 250)

[nflanagin]

Looks like your servos and blades are at 90 degrees, but why aren't the idler arms at 90 degrees. Looks like you need to raise the swash which is why the pitch in positive and negative are so different.

[bazsound]

Originally Posted by nflanagin

Looks like your servos and blades are at 90 degrees, but why aren't the idler arms at 90 degrees. Looks like you need to raise the swash which is why the pitch in positive and negative are so different.

Yeah i need to pull it apart again to readjust the links.


yep 90'd the arms as best as i could, its such a pain to increase link arm lengths because to do the rear link you have to remove the swash guide.

also need to move them 1 hole out due to binding on base of the swash guide.

guess ill just have to live with slightly too much mechanical gain until i can get blade grips with further out ball links (microheli fbl head i believe was recomended to fix this issue)

really disapointed that my tail wag has went from being minor on the copterx gyro to almost unflyable with the kbar :/

https://www.helifreak.com/attachment...7&d=1296615264

that should stop my binding issues, the copterx antirotatition bracket is much closer than the align.

[bazsound]

I give up trying to get correct head geometry, the micro heli head isnt really availible anywhere and ive read bad things about slop in the tarot head.

Ill just move back 1 hole on the servo and just live with lower settings in the kbar.

Ive got risistance in the tail, the ball links are too tight.

Edit,

just spend some time testing and tweaking.

Without tail blades and main blades but with both rotor still on the vibration seems decent (ill get some pictures up of the kbar vibration monitor) sitting arond 1500 .

Put the main blades on and see a problem, tracking is out (but expected as i had links for changes is servo arms) got the tracking as close as i could, seemed that if i went 1 turn further it would just through it out badly. Sound from the blades was much much quieter, and vibrations was greatly reduced.

Put the tail blades on and that didnt seem to add much, infact holding the heli while still feeling vibration through tail tube didnt seem so bad.


Test hover indoors.... horrible, tail wag, mushy feeling trouble getting it into a stable hover. The wag made trying to do corrections impossible.


After much back and froth between the laptop, i managed to calm down the wag by reducing acceleration slightly and reducing the I gain and P gain by different amounts then increasing the tx gain. The wag would get worse at lower gain get better as increased it then would suddenly get to a fast wag. so backed it off.


The tail is still far worse than the copter x gyro (yes i know what!) the copterx gyro still wagged a bit but was more locked in before i crashed.

The kbar after my tweaking has some random wagging.

I discovered there was resistance in my tail, the ball links were too tight, loosened them of and its now nice and free.

My tail servo is crap so that doesnt help but the copterx gyro once i spent some time with it seemed to do ok.


The worrying thing is that i increased the headspeed 5 points and it got noisy, no idea where its coming from, Main shaft bearings are align as is the maingear. bearings were repalced before the crash checked them when changing the blades, and there still silky smooth.

Main gear was changed as i stripped teeth so thats new. One way bearing is fine.

After much tweaking i got it to a slightly better feel by increasing the rotor gain to 50 (any higher and it gets unstable) expo down to 15% and increasing agility to 100.


I used the vbar softares measurement calculator to work out pitch, at full positive i get 12 degrees with it sitting at 60 a bit on the low side, cyclic is down at 55 purely because the rear link hits the antirotation bracket base. Copterx bracket sits closer to the swash (will replace with align, the copterx 1 is cutting into the pin)

Frustrating... as apart from the tail being not great it was setup well enough that i could smoothly control it. the kbar im having a real hard time just hovering

[bazsound]

Vibe anylis. No blades, main blades, tracking adjust tail blades.

there may be duplicate and i think there in reverse order

[navigator2011]

Originally Posted by bazsound

My tail servo is crap so that doesnt help but the copterx gyro once i spent some time with it seemed to do ok.

Correcting this may make a bigger difference that you expect. After installing an Align DS426mg into my 250 and carefully tuning the gyro, there is scarcely any tail wag at all. In my other 250, I installed an MKS DS95i, and there is absolutely zero detectable tail wagging.

As for your cyclic issues, I think you should build the helicopter according to the specs listed in the manual and then tone down the helicopter with careful receiver and Tx setup. Also, please do check out some of Finless Bob's build videos here:

Trex 250 build videos

I also highly recommend Finless Bob's setup videos, here:

Heli Skills and Setup 101 - LOOK here first!

[bazsound]

Originally Posted by navigator2011

Correcting this may make a bigger difference that you expect. After installing an Align DS426mg into my 250 and carefully tuning the gyro, there is scarcely any tail wag at all. In my other 250, I installed an MKS DS95i, and there is absolutely zero detectable tail wagging.

As for your cyclic issues, I think you should build the helicopter according to the specs listed in the manual and then tone down the helicopter with careful receiver and Tx setup. Also, please do check out some of Finless Bob's build videos here:

Trex 250 build videos

I also highly recommend Finless Bob's setup videos, here:

Heli Skills and Setup 101 - LOOK here first!

amazing! those videos will be very helpfull !

I replaced the copterx antirotation bracket which solves the binding issue and also the issue of cutting into the swash pin.

I also got another feathering shaft to replace the lost washer and blade grip bearings (the only spare i had was the copterx bearings and guess what, 1 of them was notchy and the other was starting to go notchy)

been busy working all weekend so no time to work on the heli.

First thing ill need to do is balance the blades again as i dont think ive done it right, the blades are increasing the vibration alot.

[bazsound]

Align anti rotation bracket solved the binding issues with the rear servo to wash link, however the holes in the frame dont quite line up, there about a mm to low so the canopy pins go in at an angle.

Spent half an hour experiment with kbar settings and got it close to how the copterx gyro was flying. I had to increase the cyclic gain to 60, also increased to 105 precision, paddle sim to 40. And turned off Expo.

This made it much easier to hover however i did notice a couple of odd cyclic moves that wernt me.

Also got the tail much better, its never going to good with a 0.17s servo but it was atleast doing its best to lock with barely any wag. The wag is random and unpredicatable, i also felt like i kept having to give right rudder as if the tail was drifting slightly.

Think my P ended up at 80, i at 40, accell 50 though and bumped up the overall gain to till it fast wagged and bumped it back a notch.

Virbration is definatly an issue, now that i can get it into a hover without bouncing of the floor can get better reading of vibrations, its getting over 3000, logs show abnormal vibratino allerts, high vibration allerts and severe vibration allerts now and then.

Also got a servo out of range erro and few other errors

[bazsound]

I was right about the tail, the tail hub has been installed to far down the shaft.

Looking at copterx manual it looks like there is a hole in the shaft for the grub screw to locate into meaning non adjustable. I had a good 3-4mm of the shaft sticking out the hob which meant less slider travel, and i was not getting 0 pitch with the slider centred.

5 minutes later to readust it, theres now only 1mm of hub sticking out (couldnt get it flush , the flatspot must not go far enough)

So now i can get a proper centering with the correct amount of travel.

Edit:

remounted gyro with the provided pads.

did a quick bench test and got first reading of 1200, gave it some load and got 1500. vibrations are WAY better, the heli actually sounds quieter now aswell and feels smoother.

I sanded the tail blades a little where it sits in the holder as there was flashing which was causing binding.

I also put a velcro strap on the gyro and tested again. 1250 no change doesnt seem to be effecting vibrations. The gyro pads dont seem to be super sticky, ive managed to unstick it by pushing on the gyro so until i can get super sticky ones ill leave the velcro strap on.

One of the problems though with mounting it on the side is theres not much for it to stick on anyway, as theres holes in the frame.

Will need to get batteries as my tx is complaining of low batteries. Last thing i want is to have a signal loss induced crashed after getting things much better

[bazsound]

https://www.youtube.com/watch?v=ijEkZZbN-yY

After much tweeking the tail is probably as good as it will ever be for a crap servo, theres not really any wag but it does randomly drift counterclockwise every now and then.

I thought i had my vibrations way down, but once i got it on the floor and checked again they were hitting 1700. after some hovering in the air it was reading 2700 and seeing high vibration alerts and a few extreme vibration alerts.

But i dont know if that was just bouncing off the floor.

I cant seem to get the blade tracking to be perfect i get it almost spot on, then another turn will put it out.