ideas HK500GT tail authority problem

[Delarado]

do you have a go pro or similar you can attach to the boom to get an idea of what the tail pitch slider is doing?

[helijohn]

do you have a go pro or similar you can attach to the boom to get an idea of what the tail pitch slider is doing?

Sadly no.

[trillian]

If you cannot spot anything mechanical and if everything seems to be moving properly when you move the rudder stick then I'd start swapping things one at a time till the problem goes away. I think based on what you have said so far I'd start with the grips or the tail servo. If you can just borrow the tail hub with grips off another heli prob start there.

[helijohn]

I think based on what you have said so far I'd start with the grips or the tail servo..

If I can't hit on a solution soon I'll have to try it.

[dillwhacker]

Take off the mains. Grab the frame very firmly. Hold heli at arms length and spool it up to 80%.
Then wiggle the heli's tail about.
It should feel REALLY powerful in HH, almost so you can't push it too far, and you can see the pitch fork movement, and hear the tail blades RPM.
I do this to adjust starting point gyro gain - just get it to feel really firm without any oscillation.
At full headspeed, you need pretty strong hand muscles to overcome the tail blade force if you are holding the frame between the skids.
HTH

[helijohn]

Take off the mains. Grab the frame very firmly. Hold heli at arms length and spool it up to 80%.
Then wiggle the heli's tail about.
It should feel REALLY powerful in HH, almost so you can't push it too far, and you can see the pitch fork movement, and hear the tail blades RPM.
I do this to adjust starting point gyro gain - just get it to feel really firm without any oscillation.
At full headspeed, you need pretty strong hand muscles to overcome the tail blade force if you are holding the frame between the skids.
HTH

Great idea for setting the gain.

I had it on the bench a few days ago (with the blades off) and the thrust from the tail was very strong - too strong to hold.


I have been working on getting more tailshaft length and it allows me more pitch for right turn.

I still can't see why the gyro itself is not keeping this bird in line. In HH mode with no input these CSM gyros do tend to drift to right rudder but once some stick input is given that stops and it has never been a problem with my other CSMs. Besides, this was happening with the gyro that was on it before.

[helijohn]

I think I may have sorted it.

I said I kept feeling there wasn't enough thrust to overcome the torque and I wanted more right turn blade pitch on the tail blades. It was like I needed more right stick.

I worked it so the shaft is a little bit longer and then I had problems with the pitch forks hitting the control arm on full right rudder. I wouldn't mind betting that this is what causes so many HK500 tails to disintegrate; the forks fouling the control arm would just wreck it all. I Dremelled the clearance. Funny thing is on the CMT version there was so much movement that the blades could hit the boom on full left pitch.


500GT clearance WMF.JPG

I know it looks like there is plenty but I took it to a just clearance state. It was really catching and jamming badly before.

This meant I could give the mid stick a lot more right-turn pitch than I would normally give yet still have room for the slider to go along the shaft a enough to give me oodles of right rudder.

500GT right pitch WMF.JPG

I am guessing - I know I have much more than 8° - but I think it must be almost about 15° at mid stick.

Then I tried it and viola. The slow piro was gone. In rate mode I was getting the right 'feel' to the rudder and when I switched it over to HH mode and brought the gain to 60% (where it us meant to be for the CSM560) it was rock solid.

Thanks for all the suggestions.

[atomiccomp]

Tell me about it. I even set it with some big angle of right turn and it didn't help. I have flown without gyro back in the day so I expected to be able to beat this in rate mode. I had a HK401B on it previously and it was just the same.

Turning left smacks of torque turn and that points to a weedy tail thrust.

It has a Goteck coreless motor digital servo BB on the tail and it seems to be responding OK to inputs.

I'd start of by binning the Goteck, its likely that's where your issue is. I had one on my 450 and it gave constant trouble from about 10 flights in. It worked great on the bench but not during flight. I replaced it with a second hand futaba 9257 for £20 and the 450 flew great after that.

[helijohn]

I'd start of by binning the Goteck, its likely that's where your issue is. I had one on my 450 and it gave constant trouble from about 10 flights in. It worked great on the bench but not during flight. I replaced it with a second hand futaba 9257 for £20 and the 450 flew great after that.

It's working fine now hopefully but I need to give the tail a proper trial.

I had intended to maybe go to a full size servo after sorting out the trouble since fitting the CSM560 with something that complements it.

[atomiccomp]

It's working fine now hopefully but I need to give the tail a proper trial.

I had intended to maybe go to a full size servo after sorting out the trouble since fitting the CSM560 with something that complements it.

No problem, hope you get some fun from it now! I posted that before I read your last post stating you had sorted it.

[helijohn]

No problem, hope you get some fun from it now! I posted that before I read your last post stating you had sorted it.

It's a good idea nonetheless.

I'll get better kit on it as I get to use it. I am wanting an AR7000 Rx next but it wasn't urgent as it is mostly a back yard heli.

[helijohn]

I'd start of by binning the Goteck,

Well since I made my last post the heli went in again, blades and all sorts mashed again.

Had some bits left from the last head unit so fixed 'er up again and I changed the Goteck and put an Align 650 on.

Tried it today and it is back to the same monkey business. First battery it is fine and I thought binning the Goteck had sorted it but comes the second battery and about a minute in it started doing just the same. It begins with tail swings that get bigger and bigger until it is a complete pirouette so I landed it before crashing it yet again.

[trillian]

Well since I made my last post the heli went in again, blades and all sorts mashed again.

Had some bits left from the last head unit so fixed 'er up again and I changed the Goteck and put an Align 650 on.

Tried it today and it is back to the same monkey business. First battery it is fine and I thought binning the Goteck had sorted it but comes the second battery and about a minute in it started doing just the same. It begins with tail swings that get bigger and bigger until it is a complete pirouette so I landed it before crashing it yet again.

Hmmmm, maybe bearings binding in the tail grips? I think that was mentioned before. It sounds like something mechanical is not letting the gyro make the correction it's trying to make, then whatever it is lets go at some point and results in a move which the gyro then tries to correct the other way and so on.

I have a hub with grips and slider assembly that I took off my 500 that definitely works, I could send it for you to try. I only removed them because I got some blingy airframe bits and a tail unit with metal grips.

[helijohn]

Many thanks Sheryl. I like the concept of a mechanical stickiness but the stick control seems to be lost which is why I landed it 'real quick' while I still could. When I had it stripped the tail was deliriously free. I am wondering if it could be an Rx problem.

[trillian]

Many thanks Sheryl. I like the concept of a mechanical stickiness but the stick control seems to be lost which is why I landed it 'real quick' while I still could. When I had it stripped the tail was deliriously free. I am wondering if it could be an Rx problem.

Well with bearings they can appear totally free but then bind under real flight loads, I suppose tail blades less so than main blades, I don't know how much force is pulling on the tail grips. If the RX channels for rudder or gyro gain were doing something erratic you'd expect to see it happen on the ground at some point but stranger things have happened.