SK-720 has cost me $1200+ so far. Please help!

[Ian Davidson]

Originally Posted by Silverexpress01

Have you checked for any stripped servo gears? I would disassemble the one that lags behind the rest. Or at least swap it around to see if the issue follows as Helos described. It may not be a gear, but a bad servo altogether.

If I exercise the cyclic using the sticks (when the helicopter is just sitting on the ground e.g. in my kitchen), all 3 servos appear equally fast, smooth and powerful. When I thrash the collective up and down (again when the helicopter is on the ground) the swash-plate moves up and down perfectly flat without any indication that one of the servos is struggling or lagging.

Moving the servos by hand, I can not feel any hint that one might have a broken gear tooth.

[Silverexpress01]

Just a suggestion, utilize something non metallic as a probe, and while powered up poke the wires and connecters for an intermittent contact/connection.

I'd look for something obvious first.

[Helos4me]

Quote:
Also, the lop-sided way the swash-plate moves when I power the system up (shown in the close-up video below) has always been the way it's done it. I've never seen anything different. Is this not normal too?? I've always re-flashed my SK-720 with the latest firmware and installed the latest software on the PC when an update has been released.


Yea buddy, bad JuJu. No good.

So don't feel bad, if this is your first FBL experience, you wouldn't have known better. Just bad luck of the draw. And don't let it put you off to SK. Once it's fixed, and you get it tuned, that thing will fly like it's on rails. SK has great sensors, but like anything, something changes between time of departure and time of arrival!

SK will fix you up.

[Ian Davidson]

Originally Posted by Helos4me

Yea buddy, bad JuJu. No good.

So don't feel bad, if this is your first FBL experience, you wouldn't have known better. Just bad luck of the draw. And don't let it put you off to SK. Once it's fixed, and you get it tuned, that thing will fly like it's on rails. SK has great sensors, but like anything, something changes between time of departure and time of arrival!

SK will fix you up.

Once again, I can't thank you and everyone who has contributed on here enough!

What disappoints me though is that I detailed this exact problem to SK on 2nd May (including the video clips shown in my first post, the last of which clearly shows the swash-plate going though it's lob-sided initialisation), but this wasn't picked up by them. Since the 2nd May I've spent $600+ on repairs.

Also, why would the SK-720 ever allow itself to stabilise a helicopter when the gyro knew it wasn't right in itself (the error message on the PC saying "Gyro failed to initialise") ?? Hmm...

Oh well, I'm mustn't be too critical of SK - I need to politely request that they replace my SK-720 for me.

[Ian Davidson]

Originally Posted by Silverexpress01

Just a suggestion, utilize something non metallic as a probe, and while powered up poke the wires and connecters for an intermittent contact/connection.

I'd look for something obvious first.

Thank you. Yes, since starting this thread I have put a continuity meter between various points on the power wires and wiggled cables and even tapped vigorously the power switch to see if I can find any break-points, but so far nothing. It seems I have a duff SK-720

[georgi UK]

=] please keep us posted as to the resolution here, I was involved indirectly with another controller running on a twin shaft turbine.

https://www.helifreak.com/showthread.php?t=277654

one of the beta pilots that ran a turbine during SK testing had zero issues here, from what I can see there is a voltage drop beyond operational limits, and then all hell breaks loose, which I would expect.

this is either externally or internally as far as the SK is concerned,

georgi UK

[Helos4me]

You know that brings up a check you could do. Hook the SK directly to a power source, hook up the usb and see if you still get the initialization error message. No servos no other accessories. If you don't then you have a wire crossed somewhere.

[Thunder Fighter]

I had the message about the gyro failed to initialize with one of my Skookums, Art told me to try leaving the unit motionless for a minute then doing a "reset log counter", as this does a minor calibration. I haven't seen the error since.

//Dennis.

[Helos4me]

That's good to know and worth a try. Still best to contact Skookum. Too much at risk.

[Ian Davidson]

Thanks guys! I'm now out-of-action for a couple of days, but I've emailed SK and I'll keep you updated on my progress. In the interim period though, I'll definitely try what you've suggested (reset log counter and remove servo wires) and I'll let you know if this yields any results.

Georgi, I must admit I was aware of the HC3 issue with 2-stage turbines and that had crossed my mind with respect to the SK too, but with hindsight I now know my SK-720 doesn't seem to be working as it should before I've even fired the turbine up.

You guys really have been very helpful - thank you!

[Silverexpress01]

Originally Posted by Ian Davidson

Thanks again Georgi; it's just possible you might have shown me the light. I was perhaps failing to see the wood for the trees! With your help, I think I've now realised what could be causing it...

Since both the 5V and 6V rails within the regulator are separate/independent and yet both appear to fail under load, then it must be the power source feeding the regulator. I know the battery to the regulator is perfect BUT there is a 10A toggle switch in-line between the battery and regulator, so it's possible this could be failing... especially under a combination of load and vibration. Not only that, but it's a two pole 10A toggle switch, so it's also possible each pole might only be rated at 5A !!

Thanks again Georgi - I'll bypass the toggle switch and report back!

Just a thought - in place of the switch, would a Deans connector work? The female connected to your circuit and mounted on the heli, and the male would work as a removable jumper plug. It would take a lot of vibration to unplug a Deans Ultra.

[Helos4me]

You get the warning just plugging in the usb to the sk right? No power to servos or anything else? If so contact Skookum. Everything else has been eliminated anyway.

[Ian Davidson]

Art replied and kindly offered to do an advance exchange so long as I email proof that I've dispatched mine back. I'm now at the stage where this seems the most sensible (and cheapest!) next step. Art did explain the reason behind the Windows XP error message and tilted swash-plate at init, but I must admit I didn't quite follow it! That said, since I'll be returning mine (and I've had a long day), I decided not to ask Art to explain it again.

I'll keep you chaps updated! Thanks again

[georgi UK]

=] Ian, thanks for getting back to us, I do want to see that maiden vid much as you do!!

how much $$ to try an entry level model?? and is the jet too much messing around, or fuel n go??

georgi UK

[Ian Davidson]

Originally Posted by gmcallister

=] Ian, thanks for getting back to us, I do want to see that maiden vid much as you do!!

how much $$ to try an entry level model?? and is the jet too much messing around, or fuel n go??

georgi UK

Trust me, the jet engine has been the most reliable part of the whole thing - it's never let me down! Other than the initial cost of the darn thing, there really are no negatives to them. They're powerful (oh yes!), reliable, sound great, easy to start and easy to stop. They're fantastic!. They do drink A LOT of fuel though (1/4 gallon might last you 10 minutes if you're lucky), but the fuel is relatively cheap, so it's not a big problem.

Cost wise, if you want to build one new, a simple pod-n-boom (like mine) is going to set you back at least $6k or £4k minimum. If you want one built for you in a scale fuselage, then you can double that easily. I think you should be able to pick up a second hand pod-n-boom though for perhaps $4.5 or £3k. If you're going to get one, go for a 2-stage. They're more expensive, but much more powerful, efficient and elegant in my opinion.

[georgi UK]

=] sell the house then!! wow that's expensive for the thrill, didn't realise it was that bad.

think of how many SK's that would buy!

georgi UK

[fusionsx00]

Jetcat and auto start

1 button push start

[rcflyerheli]

One thing I noticed in your last video, and this can possibly mess EVERYTHING else in your setup up. When you are showing the stick values you first say you are moving the cyclic (aileron) to the left and you get a red indication from the 720. That is correct. But then you say you are moving the elevator stick up and you also get a red indication. For up nose up movements you should get a green indication. If you simply reverse the elevator direction, now your swash will not move correctly. I would go through the initial setup wizard again.

I have gone back and reviewed your video again, and now I am not so sure what you are indicating. When you first start moving your right stick you indicate left and up. Left is self explanitory, but when you refer to up, are you referring to stick movement or what should be heli movement. As a pilot, we always refer to aircraft movement, so aircraft nose up is actually aft stick or stick movement towards the bottom of the xmitter. If you move the stick so as to achieve nose up tilt, the indication on the screen should be green. Look at step 24 on the initial setup wizard.

Good luck

[Ian Davidson]

Many thanks for your input, but apologies, with hindsight my voice-over wasn't very clear!

I was describing the stick position, not the resultant helicopter nose movement. When I said 'up' I meant I was pushing the stick 'up' and thus nose down. When I said 'down', I meant I was pulling the stick down/back and thus nose up. I'm pretty sure the SK-720 was set up correctly, but as of 2 hours ago it was dispatched back to Skookum for a replacement.

[rcflyerheli]

Originally Posted by Ian Davidson

Many thanks for your input, but apologies, with hindsight my voice-over wasn't very clear!

I was describing the stick position, not the resultant helicopter nose movement. When I said 'up' I meant I was pushing the stick 'up' and thus nose down. When I said 'down', I meant I was pulling the stick down/back and thus nose up. I'm pretty sure the SK-720 was set up correctly, but as of 2 hours ago it was dispatched back to Skookum for a replacement.

I knew that would be one of the two possible answers. Sometimes, though, it is the simplest things that we overlook. Is Art just going to send you a replacement? Good luck. I just got mine back after sending it in for a cracked case and update to the latest firmware. I just finished the setup last night, but it is so windy here (and hot) haven't been able to test fly the bird. I did run it up with tail blades and no mains, and got nice low (.3) max vibration readings, so hopefully the mains will be balanced enough for self leveling to work. One other thing in one of your videos, the gyro in general will always tilt the swash opposite the type of pitch/roll/yaw the heli experiences. It's not just the auto level that does that. I haven't ever used the auto level function on mine. I may set it up on one bank just to try it.

Any way, hope you are able to get everything worked out. Your bird is sure a sweet sounding machine.