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HelicopterScale Model RC Helicopters News  DJI WooKong-Heli Autopilot System for Scale/Hobby
12-13-2011 10:01 PM  5 years agoPost 21
Joel Rosenzweig

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Marlborough, MA -​USA

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Still waiying foe an answer from anybody who has used one of these units on a relly heavy machine
Maybe you missed my posts from August / September when I installed the Wookong-H into my Vario Air Crane. It's 40lbs, and has a 6-bladed head.

The thread is here: https://rc.runryder.com/helicopter/...3/?p=5493693#RR Scroll down to see the YouTube video.

Joel

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12-13-2011 10:27 PM  5 years agoPost 22
PETER ROB

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Devon UK

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one of these units on a really heavy machine

Joel, Thanks, that is 2 machines now
I was hoping for a reply post from DJI, but it looks like they have not done any testing on the really large machines
Peter R

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12-14-2011 08:27 PM  5 years agoPost 23
coptercptn

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Mesa AZ. USA

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I'm in the process of installing one in a 6 blade Ch-53 43lbs

Home of the "Sea Cobra".....

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12-24-2011 04:52 PM  5 years agoPost 24
MattJen

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UK

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Has anyone installed these on a heavy 2 STAGE TURBINE ?

is the aircrane a two stage turbine?

reason for asking is all i hear is FBL units suddenly doing funny things, like putting in full pitch, then full negative, or tipping over,a fellow longranger owner had his machine suddenly to do a tick tock, and in it went tail first,it was not a DJI, but another manufacturer...as have all the other incidents been.

The common thread in all that i have found is not so much the weight, but the frequency that a 2 stage turbine runs at, it seems to run at such a high frequency it interferes and messes up the electronics of the FBL unit.

The last thing i want is my pride and joy to be smashed, all in the name of making it look that little bit more scale.

It seems with these you are in the lap of the gods when they go wrong, as you have no control...
SOme i know try out these units on a cheap to replace model, so if it goes in then expensive machines and equipment are not wiped out.

Matt

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12-26-2011 01:37 PM  5 years agoPost 25
NickC

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Leicestershire UK

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Hey Matt

Your one number out

The CH54 is the Aircrane the CH53 is the Super Stallion.

I think the 53 runs a PHT3 single stage (like the one Dave Hollins had) the Aircrane does run the SPH5 two stage.

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12-26-2011 02:00 PM  5 years agoPost 26
modtron

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Oxford. UK

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Matt, what make of LongRanger was this and what system was being operated ?

Was it a turbine powered, if so single or 2 stage system ?

I am asking because the only system that has shown any problem as you describe, was the HC3 series from Helicommand and that was for an Acoustic sound problem which only occured with 2 stage systems.
This has now also been corrected along with the use of a protective acoustic housing.

As you are well aware, many people are now using ALL types of stab systems with electric, glow, petrol and turbine with NO issues what so ever.

It seems with these you are in the lap of the gods when they go wrong, as you have no control...

Very true, but then that also applies to everything we operate by radio!

modtron
Oxford UK

ps - both the Aircrane and the CH53 use the JetCat 2 stage system

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12-26-2011 06:52 PM  5 years agoPost 27
coptercptn

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Mesa AZ. USA

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I'm using a Jakadowski Pro... it is two stage.

Home of the "Sea Cobra".....

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12-26-2011 06:58 PM  5 years agoPost 28
PETER ROB

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Devon UK

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I'm using a Jakadowski Pro... it is two​stage.

Is it?
Mine has gears attached, makes it single stage
Peter R

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12-26-2011 07:05 PM  5 years agoPost 29
modtron

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Oxford. UK

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To date Jakodofsky have never made a 2 stage engine available for sale.

Single stage = single drive train via gears from connected turbine shaft
2 stage = drive via separate thrust driven 2nd stage gearbox - no direct drive - also normally higher running rpm.

modtron
Oxford UK

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12-26-2011 09:16 PM  5 years agoPost 30
Joel Rosenzweig

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Marlborough, MA -​USA

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My Air Crane is electric powered.

Joel

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12-27-2011 09:33 PM  5 years agoPost 31
MattJen

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UK

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Hi Modtron, and others.
As you are well aware, many people are now using ALL types of stab systems with electric, glow, petrol and turbine with NO issues what so ever.
Not on Two stage turbines, as most of the scale fuses out there for turbines are using the Jetcat or Jako single stage, which run at 90-94000, much slower than a two stage that is running around 140,000.
it also seems the low head speed they struggle with, I have tried to hover a well setup Beastex, it is fine in FFF, but you slow down to do a piro or slow flying you are fighting the machine all the way.
As you know, I can fly slow and extremely precise..

I have witnessed shocking results with the Skookum, and Beastex and Vbar,

John Tanners Longranger which is sitting on my bench as we speak went in,
His test flight with the beastex saw the model take off and then rear backwards (i.e. a large amount of rear cyclic was applied - but not by him), he put in a lot of forward cyclic, which worked, but he then had the model going to a 60º nose down attitude, back cyclic and the same happened. so it became like a tic toc manouver, He decided the only safe way of getting it safely down was to reduce collective as He put in forward cyclic and in effect slammed it down on the undercarriage,
The resulting damage was a flattened u/c and the fuselage/tail joint cracked open. Bear in mind the model has a full aluminium boom in the tail, so the crack was not structural.
He straightened the u/c, repaired the crack, fully checked the mechanics, replaced the flybar and continued to fly it without the Beastex and has not had a problem since..

The other was a predator Wren 2 stage, the poor guy has had 5 crashes due to his FBL unit, it just seems to hit a freqency at a certain RPM,
me and Bell Bloke think around 100,000 rpm, - ( speculation) it then causes the Unit to go mad leaving you in the lap of the gods..

Very true, but then that also applies to everything we operate by radio!

Point taken, but you can programme a fail safe which will try and limit the damage, you can also do regular checks on your servos.
But it seems when these FBL units go they do all number of mad things,the video shows below it suddenly putting in full negative and then full positive, luckily the machine went up rathar than straight back.

Here are 2 vids of this event happening the second was the first flight after the Rebuild.. I cringed when i saw it..

Matt

Watch at YouTube

Watch at YouTube

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12-27-2011 09:58 PM  5 years agoPost 32
Dr.Tim

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Mojave Desert

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Those are real bad videos!! I hate to see things like that .. I have been flying my Turbine Lama with the Skookum 360 now for several months with excellent results, even in high winds! (Look up the video from Scale Masters, The Blue and white lama is mine) I think the problem with most these systems is vibration (FREQ.) as most turbines even thouogh they feel smooth when they reach full power there is some. The best we can do is isolate these units from it as much as posible. In my Lama the unit is as far forward as I could get it and keep it level .. I think Dampening is the key.
A few prayers don't hurt either!

Dr.Tim

From Simple minds come simple ideas! Approach Engineering

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12-27-2011 10:07 PM  5 years agoPost 33
MattJen

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UK

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I agree Dr Tim,

But your lovely machine is using a single stage,as is Modtrons lovely models like his EC120, all the problems i have seen are when the power unit is a two stage..

I am not trying to stir up a hornets nest or start an argument with anyone manufacturer, but the more we all chat about these issues, the more improvements we will see.

At the moment it is not all success with these units on 2 stage turbines, and I think in my own opinion it is unsafe and unwise to use them on large scale models utilising a two stage turbine.. that has regular use, not a machine that comes out for shows or special events..

It does remind me when electrics first came onto the market and we were on 35meg, we were getting lock outs from the RF of the speed controller, and it was only when we started to highlight these issues on forums such as these the manufacturers made the improvements to the high standards we have today, where flyers can now even fly a large scale models like the 1/4 scale jetranger,lama etc on Lypos.. and have full confidence in them.

Matt

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12-28-2011 12:56 AM  5 years agoPost 34
helibeli

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wales.uk

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Is it a mechanical vibration problem or are the electronics being interfered with by harmonics from the twin stage turbine?

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12-28-2011 11:46 AM  5 years agoPost 35
modtron

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Oxford. UK

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Interesting videos ?

On the first one, you can hear 2 kicks on the tail at 1.38 - just before anything else happens ?

As I stated before, Helicommand addressed this issue with 2 stage engines as being "Acoustic" interference that was affecting the HC3 series. Their cure, amongst other things is to now use an Acoustic foam hat covering the gyro unit.

The other possibilty maybe a Static discharge at the higher operating rpm of the 2 stage units ? - just a thought, as I know it has been reported to have be an issue in turbine powered aircraft some time ago.

I'm not convinced it's mechanic vibration as the engine unit should be smooth when it's at it's running speed of around 140,000 - 160,000 and as there is no drive other than thrust between the engine and the gearbox, any variance is taken up on the gearbox input drive wheel.

If it is only noticed at around 100,000, then maybe it is still an acoustic issue with the BeastX system ? Would be good to see a run without any blades to see if it can drive through it ?

I personally have no experience of the BeastX system, but hear of good reports and the same goes for the Skookum systems.

As for damping, a lot of the systems on the market are now being supplied with very thin foam tape for a Solid Mounting.
The sensors inside the case are already damped internally, so if you then add more damping to the case, you actually make the system worse not better.

Interesting topic, non the less.

modtron
Oxford UK

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12-28-2011 03:47 PM  5 years agoPost 36
MattJen

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UK

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Interesting Info Modtron..

I to think it is not Mechanical, Bell and I almost certain it is the turbine frequency at a specific RPM range, but until someone does a real detailed specific test all it is 2 modellers speaking an idea..

It does seem to be limited to just two stage turbines, I to have not heard of any issues on single stage,Electric,Gasser or Nitro..

The fact HC have come out with a fix to eliminate High frequency does seem to indicate there is a potential risk of interference from these 2 stage turbines.

Trouble is it is all still very new and there isn't many two stage Jetcats or Wrens in scale applications.

The Mw44 in the Trex and others seem to be running at high 3D specs, 2000/2200 rpm. Which seems to indicate it is out of the danger zone..

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12-29-2011 02:39 AM  5 years agoPost 37
Bell Bloke

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UK

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Hi Guys, this high frequency issue is a problem that I have been aware of for the past 5 years when I purchased a couple of auto pilot systems. I found that when they were fitted to a 2 stage engine the moment the turbine hit 110000rpm the auto pilot would go wild and crash the helicopter. I realised after doing a download from one of the auto pilot systems that it was picking up a very odd frequency, this I quickly realised was the turbine.
The fix was to pack the autopilot in sound foam, however that only worked while the canopy was off. With the canopy on the autopilot became unstable again although not catastrophic. The fix was to put sound baffles in the canopy as well and sound deadning foam, also I cut the air intake in the canopy much larger to encourage all the air to feed the turbine from the front. The auto pilot download showed that with all of these measures in place there was no interference from the turbine any more even at full power.
My conclusion is that these units are affected by turbines running at 110000rpm+ as my data print outs show this.
I dont think many of the new systems out there are tested on 2 stage turbines, only electric and piston engines.
In this game it is us the consumers who are the test pilots, and it is in this spirit that there will have to be a few turbines sacrificed in the name of progress before all the bugs are finally fixed....
Just make sure its not your lovely turbine that has to be sacrificed to achieve this goal

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12-29-2011 05:07 AM  5 years agoPost 38
mcfast

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Quebec Quebec Canada

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Ha, Bell Bloke that's a good one! should help a lot guys.

P.S. sorry for the spelling or the grammar I am dyslexic!

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12-29-2011 06:53 AM  5 years agoPost 39
PETER ROB

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Devon UK

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this high frequency issue is a problem

Ross, Good to see you are still interested
Your conclusions, to which I agree, are 5 years old, and from one type of unit
WHith the advances in stabilisation units in the last 5 years, and the differing set ups, surely there would be a lot more reported accidents if it were only high frequency based as every 2 stage turbine has to go through the the revs you are quoting
You are saying that this only happens with 2 stage turbines, if this is the case what is causing all the accidents on non 2 stage setups,
The one reason I have so many xtabilisation units in the spares box, is because, I am a firm believer, that they are not what they claim to be, and a good mechanical set up should be acheived before adding these units
There is a place for stabilisation units primerily, in the commercial market for which they were originally designed
Peter R

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12-29-2011 10:30 AM  5 years agoPost 40
Bell Bloke

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UK

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Hi Peter, sorry, I am bang upto date on this one.
This issue goes way deeper than that for me ie. I have had 2 people with me crash their turbines recently after I suggested there may be a problem with High Frequency affecting the units that they had. Both had originally come to me for setting up new turbine machines and or which they within weeks converted themselves to flybarless. I had suggested to them both that they should put large training undercarriage on and if possible do data downloads to varify that the turbine was not affecting their units. Unfortunately one guy chose to ignor this advide and crashed and the other guy who did take the advice had the unit go full pitch on him and he crashed too.

Have I lost interest?..

Well when I read about the helicommand 2 years ago I knew exactly what the problem was and I had a long discussion with Matt about it. He said that I should post something in the forums, but I told him, it ain't worth it anymore. I knew if I dared suggest what the problem was and even more the fix, I would get all kinds of crap and flack from 'interested partys'
This hobby as I have always said is a real money maker for some people and they don't like people like me putting their underdeveloped products down...
After all who am I....and who are people gonna believe here, me or the manufacterer.
So now I am sorry to say, I just watch....trying to help people here is just too stressfull.
I now only help the folks who wanna be helped, and I do, and that gives me much satisfaction.

I should like to add that I have no experience with the dji system and am not at all in anyway wanting to suggest that there are any issues with it.
I am just posting in response to Matts post which unfortunately happens to be in this section.
The dji system looks very interesting and power to them I say.

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