Tren 744 Turbine

[kevinww]

The 744 is now converted to a Flybarless 844 using VBar and swinging 800 blades. The original 8.2 ratio gearing was also re-installed instead of the 7.6 to help spin those larger blades. First test today showed it is an awsome setup. Extreamly stable but very nimble, it has almost constant headspead around 1600 and it flies like its on rails, one added bonus is the longer boom meant the CofG was almost spot on whereas before with the 700 boom I had to add some lead weight to the tail to get a decent CofG.

Now all I've got to do is work out how I can get the 844 and the Xxtreme in the car at the same time.

[DenisFerrari]

Any update video or photos?
Cheers
Denis

[kevinww]

Heres a short vid that was taken on a cell phone.

YouTube

YouTube

[DenisFerrari]

Looks great,
Congratulations!
Thank you
Denis

[kevinww]

Made some more tweaks to the 744 turbine and I think I've found the perfect setup for my flying style.

It's now running Edge 753 mains and 115 tails on standard 8.2:1 gearing with the turbine running at 185,000rpm.

This gives it a lot more initial punch over the Edge 813 blades which were a bit on the heavy side and slightly marginal on tail clearence with 115 tails, the cyclic is also quicker and the whole heli feels more responsive and alive.

[Aussieheliguy]

So what's the head speed at that rpm? and what is the fuel burn rate like now?

What service interval do you expect with the engine running at that rpm?

A while ago I was considering buying a tail pipe to use the gas generator in a plane, but was told by Wren that the heli engine wasn't balanced to the level of the thruster aeroplane version. I was advised it wasn't a good idea.

I limit my 44 to 150K, it now has over 100 hours on the original bearings, it has been back for a service at 70 hours and didn't need gas generator bearings replaced.

[kevinww]

Head speed is around 1750-1800 and I lost around 30 seconds of flight time.

Service Interval is not so much of an issue as Wren UK is only 200 or so miles up the road, but I would expect 50 hours or so.

Not sure why they would say that about the balence, the original motors came preset at 175,000 and the manual suggests going to 185k for aerobatic / 3D flight. As far as i was aware the only difference is the gearbox, maybe they changed it on later motors, mine was one of the first batch.

[sunnyville]

Well I just maidened my 744 today(no longer boom yet still on 710s).
The manual still stated that you can turn it up to 185k for even more bite but it will shorten bearing lifespan.

[Aussieheliguy]

Maybe they were just trying to get me to buy another engine,

[Wren Turbines USA]

Most setups only require 180,000 to 186,000 rpm.
Naturally the bearing life will be shortened if higher rpms are used, as the last 10,000 rpm is where the biggest power curve is at.
As an example:
On our Wren 160 thrust turbine, the motor makes 34 pounds at 123,000 rpm, but at 116,000 it makes 28 pounds.
The 44 helis that I have been involved with are stupid overpowered.!!!!
The gearbox on the 44 Heli is the same physical size as an OS .91 Heli glow motor.
The .91 glow motor is rated at 3-4 SHP
The Wren 44 heli is rated at nearly 8 SHP

Gotta love the smell and the ease of starting.
You can see a couple of videos from IRCHA with "Pinion in the Pocket" on You Tube.

BTW....I have 2 of the 44s ready to ship if interested, email or call for a great deal before the end of the year.
Happy Holidays!
Ron Ballard
Wren Turbines USA

[Aussieheliguy]

So are you saying, instead of reving their ring out, regear to suit the power curve. Gear them like a 4 stroke not a 2 stroke.

[cbergen]

Proper gearing certainly plays a part in performance and fuel consumption.

And why we offer different gearing to suit your style of flight, or 700 vs 800 size blades.