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HomeScale✈️AircraftScale HeliScale Helicopter Main Discussion › Vario Cobra PHT3 Turbine.
04-25-2014 04:03 PM  6 years ago
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Double Decks

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Vario Cobra PHT3 Turbine.
Omg where to start. After my last frightening EC135 build I thought get back on don't give up. So along came Richard Morris with this Cobra for sale, When I got it home there was not a lot to do as it was in very good condition, apart from minor scratches. The most difficult job was to replace rear drive coupler as this was worn out. Crub screws rounded off no matter how I tried no joy, so out with the dremil and cut through the shaft the pulled out from the front. New tail shaft and couplers were ordered from Vario. While all this work was going on my turbine was on its way to Nigel (Modtron) as he was off to jet power so he could take it by hand, While the EC 135 was shaking it head off, it threw the belts and bent the main shaft. While talking to Nigel I found out this used to be his Cobra who then sold it to a guy in Maidenhead small world, So with Nigel interested in this build he ordered me a new complete head, complete rear gear box, linkages. All of these were quickly delivered so on with the task of building them up. Quick turn around from jetcat and on with installing unit into fuse, i already installed new tail shaft, bearings and coupler. Once turbine was fitted to frames it was slid into fuse with no problems. With all in and lined up on with electrics and plumbing also fitted machine gun sound module and machine gun effect flashing LEDs to front moving guns. With the head and tail gear box fitted everything went together quite quick. Nigel already said he would pop down once finished to give it the once over but I traveled up to Oxford on Monday. Nigel looked over the head and made a few adjustments, checked over tail and again made adjustments, replaced fuel fitting and checked over overall settings in my radio. Today managed to test her out, into hover without HH on tail and Held, Nigel was spot on with settings, no drifting left or right but wanted to fly of straight, on checking CG at Nigel's she was a tad over nose heavy, so with the extra battery's up front I removed some of the lead weight, now she come up into hover without flying off, she dose hover tail down as with my old NH90. As you can see in photos fuse with grey primer and finished project

Alan matthews
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04-25-2014 04:20 PM  6 years ago
modtron

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Alan,

Great news all round at last, this is what I call a success story and should not be hard to achieve by anyone.
Now go get some air time and enjoy it.

modtron
Oxford UK
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04-25-2014 04:34 PM  6 years ago
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Just had another test LOVE IT, Once again Thanks Nigel
Alan matthews
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04-25-2014 06:54 PM  6 years ago
mookie

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Fantastic job Alan, really good to see you got straight back into it, and ended up with a superb looking model. Can't get over how fast you got it in the air. I'm being put to shame, but like you Nigel is really helping me out, phone calls, emails, texts and parts etc.
Hope to get to see the cobra flying soon.
Enjoy it, Great job!
valve boy!
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04-25-2014 07:41 PM  6 years ago
Mojave

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Palos Verdes, Ca. USA

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That Cobra turned out super nice! I also like the paint scheme on the R22 in the background, very cool...
Barry
All helis and planes have an expiration date stamped on them...you only find it after you crash!!
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04-25-2014 07:49 PM  6 years ago
Double Decks

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Thanks Malcolm , can't wait to see your NH when finished. Hi Barry The R22 also came from Richard, this was done in the Silverstone Heli Air livery, Hope you are wellAlan matthews
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05-04-2014 07:01 PM  6 years ago
Double Decks

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Vario Cobra
Well what a great sunny day, light winds throughout out the day. Had 4 tanks of fuel through her today really getting used to her

Alan matthews
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08-24-2014 11:31 PM  6 years ago
Coolheli

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Mississauga,Ca

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Hi Alan
I’m in the process of setting up and flight testing the Cobra and have some questions for you if you don't mind?
1.Head speed -...
2.Blades size and manufacture -...
3.Main shaft size -...
4.Turbine speed and gear ratio -...
5.Head speed -...
6.Governor -...
7.Inside the fuse temperature -...
8.Are there any fans incorporated to help the airflow inside the fuse -...
It is dangerous to be right in matters on which the established authorities are wrong. Voltaire
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08-25-2014 10:23 AM  6 years ago
modtron

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Oxford. UK

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Coolheli,

Answers to your questions.....

1.Head speed -
1283 rpm
2.Blades size and manufacture -
1810.00 dia Vario Pt. No. 419
3.Main shaft size -
12 mm Vario Pt. No. 35/47
4.Turbine speed and gear ratio -
94000 rpm @ 73.25 : 1
5.Head speed -
see above
6.Governor -
Turbine at 100% power
7.Inside the fuse temperature -
Normally around 550 - 650 c
8.Are there any fans incorporated to help the airflow inside the fuse -
None required at all.

modtron
Oxford UK
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08-25-2014 09:48 PM  6 years ago
Coolheli

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Modtron
Thank you for your replay.
We are running just under a 1000 rpm on the main rotor so that may be a reason why the heli feels a little lose. Will have to deal with the high internal temperatures first though. Already installed a computer fan in front of main mast mechanics as I was afraid of the servos getting cooked. Two more temp. sensors will be installed before next test. It seams to be non issue in flight but a major problem when stationery/hover and after landing.
Temperatures in our are in low 30C so that doesn't help either.
It is dangerous to be right in matters on which the established authorities are wrong. Voltaire
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08-25-2014 10:05 PM  6 years ago
modtron

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Oxford. UK

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Are you running a PHT3 turbine as I don't see how you have the head speed at 1000 rpm.
If it is a turbine then you are cooking the engine by running it to slow and that's why it's getting hot !
It is designed to run at 94000 / 1283 rpm and at that speed and load the temps will reduce.
Can you list what you are running and how ?
modtron
Oxford UK
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08-26-2014 07:12 AM  6 years ago
Double Decks

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Hi Coolheli, sorry been busy this weekend to get back to you, but Nigel is correct, I have no extra fans built into the fuse and she runs well within the temp rangeAlan matthews
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