Hi guys,
you may remember my post a few weeks ago on the issues I was having with the HK250. Well I am pleased (if that's the word) to report that finally this thing is flyable and more importantly stable! ok, so it's not quite as hands off hover stable as the bigger 450 and 500 but it is VERY flyable now.
I flew it yesterday in our bedroom for a complete pack just finidhing off the setup and it was fine.
Sadly, it has cost me probably more in parts than it was probably worth. The issue you may remember was the horrendous tailwag that nothing I did improved, 3 different gyros, as many different servos - both digital and non, read every post i could find on the internet on the very well documented tail wag issue.
finally in desperation i started swapping parts out for genuine align. This is what iv'e changes so far:
dumped the hobbywing esc for a CC phoenix 25 (awesome esc)
kevlar belt
align boom
align boom holder
align tail pitch assembly (SE)
align (upgraded) metal rotor control arm (improved moment arm)
align latest version tail holder set (SE) with chinese weights) modified to double bearing to remove the slop
align SE skid set
align A and B links
align 37mm tail blades
align paddles
carbon fibre 205mm blades
align rotor hub (nothing i did could stop the hk hub wobbling - even tried 2 before giving up)
modified the hk mixing arms to use ball races instad of the crap bushes
Corona DS929MG tail servo
align feathering shaft and align main shaft as the HK ones are made from plasticine i think
all the tail end stuff got a totally slop free mechanism that got the tail well and truly sorted and coupled with moving the ball link to within 5mm of the centre of the servo almost illiminated the tail wag. not totally happy however i started on the head and changed all the other lot out to make it totally vibration free. The other mod was to strengthen the electonics plate on which the gyro sat - i noticed once purely by chance that it appeared to vibrate just slightly at a certain head speed and it really upset the gyro - glueing on some carbon rod filed to a slight flat stopped this.
I also came to the conclusion that the headspeed was too high, at 100% throttle on 3D mode it was just too wild and although this is contrary to everything i understood about a higher headspeed lowering the throttle curve to 90% at the top end whilst increasing the CCPM pitch (from 60% to 80%) improved the stick position to just above 60% stick travel for a nice steady hover and taming the cyclic, although i did initially dial in 25% expo as well but iv'e since taken that out.
I have a 14tooth .4mod pinion on order just to try it, see if it allows the throttle curve back up to 100% out of curiosity.
gyro gain now - and this is back with the 250MEMS gyro which at first i condemned then realised that it was actually not the root cause..lol is 34 on rate and 60 on HH (DX6i settings) and at this it's a solid hold with no bounce on fast pyro's stopping well.
so the conclusion is that this little heli is great when it's dialed in and set up real well but costs a small fortune to put right - though to be fair i got a bit carried away and some of the stuff like the skids, links although they do fit better than the HK ones, head if you can get one that actually centres, the esc but again the spoolup on the cc is just soooo smooth and possibly helps the gyro stay settled, may not have actually have been necessary to sort it. the other stuff in the list was without doubt was.
oh and invest in a swash plate levelling tool as well and check it all the way up and down throught 10 degrees positive and negative pitch to be sure, interestingly i had issues with one servo having an inconsistent movement over the range travel compared to the other two and eventually swapped this out as well to solve that issue.
I hope this saves others with this heli their sanity chasing the cause of similar issues.
cheers!
Rich - now with significantly more grey hairs than when i embarked on this project!
you may remember my post a few weeks ago on the issues I was having with the HK250. Well I am pleased (if that's the word) to report that finally this thing is flyable and more importantly stable! ok, so it's not quite as hands off hover stable as the bigger 450 and 500 but it is VERY flyable now.
I flew it yesterday in our bedroom for a complete pack just finidhing off the setup and it was fine.
Sadly, it has cost me probably more in parts than it was probably worth. The issue you may remember was the horrendous tailwag that nothing I did improved, 3 different gyros, as many different servos - both digital and non, read every post i could find on the internet on the very well documented tail wag issue.
finally in desperation i started swapping parts out for genuine align. This is what iv'e changes so far:
dumped the hobbywing esc for a CC phoenix 25 (awesome esc)
kevlar belt
align boom
align boom holder
align tail pitch assembly (SE)
align (upgraded) metal rotor control arm (improved moment arm)
align latest version tail holder set (SE) with chinese weights) modified to double bearing to remove the slop
align SE skid set
align A and B links
align 37mm tail blades
align paddles
carbon fibre 205mm blades
align rotor hub (nothing i did could stop the hk hub wobbling - even tried 2 before giving up)
modified the hk mixing arms to use ball races instad of the crap bushes
Corona DS929MG tail servo
align feathering shaft and align main shaft as the HK ones are made from plasticine i think
all the tail end stuff got a totally slop free mechanism that got the tail well and truly sorted and coupled with moving the ball link to within 5mm of the centre of the servo almost illiminated the tail wag. not totally happy however i started on the head and changed all the other lot out to make it totally vibration free. The other mod was to strengthen the electonics plate on which the gyro sat - i noticed once purely by chance that it appeared to vibrate just slightly at a certain head speed and it really upset the gyro - glueing on some carbon rod filed to a slight flat stopped this.
I also came to the conclusion that the headspeed was too high, at 100% throttle on 3D mode it was just too wild and although this is contrary to everything i understood about a higher headspeed lowering the throttle curve to 90% at the top end whilst increasing the CCPM pitch (from 60% to 80%) improved the stick position to just above 60% stick travel for a nice steady hover and taming the cyclic, although i did initially dial in 25% expo as well but iv'e since taken that out.
I have a 14tooth .4mod pinion on order just to try it, see if it allows the throttle curve back up to 100% out of curiosity.
gyro gain now - and this is back with the 250MEMS gyro which at first i condemned then realised that it was actually not the root cause..lol is 34 on rate and 60 on HH (DX6i settings) and at this it's a solid hold with no bounce on fast pyro's stopping well.
so the conclusion is that this little heli is great when it's dialed in and set up real well but costs a small fortune to put right - though to be fair i got a bit carried away and some of the stuff like the skids, links although they do fit better than the HK ones, head if you can get one that actually centres, the esc but again the spoolup on the cc is just soooo smooth and possibly helps the gyro stay settled, may not have actually have been necessary to sort it. the other stuff in the list was without doubt was.
oh and invest in a swash plate levelling tool as well and check it all the way up and down throught 10 degrees positive and negative pitch to be sure, interestingly i had issues with one servo having an inconsistent movement over the range travel compared to the other two and eventually swapped this out as well to solve that issue.
I hope this saves others with this heli their sanity chasing the cause of similar issues.
cheers!
Rich - now with significantly more grey hairs than when i embarked on this project!
