Wren 44 + 800T

[KevinChiu123]

Wren 44, Align 800-T. (FK-810mm).

Moreover, MD-8 is also coming.......

[sunnyville]

Nice heli although I don't know what md8 means. Did you make those frames yourself? What blades are those? Is that the 800 stretch kit?

[KevinChiu123]

Thanks a lot for your compliment. Yes, we modified the airframes for us.

RotorTech 810, tail 115.

MD-8 is an EP heli. We plan to modify this heli for Wren 44 again. We love the simple and strong construction of this heli. You might not be able to read Chinese, but you can see those pictures.
http://www.rctech.com.tw/news/product/4005-md.html

http://www.rctech.com.tw/rctmag/rcat...3956-rcat.html

The test flight yesterday for 800T is here~
[ame]http://www.youtube.com/watch?v=bm2zFTFf8eQ[/ame]

[simon2469]

Looking good guys !

So is this a convertion kit that you are working on ??

How do the red Tank fair with the heat? I see you've got some Heat shield on them.
I must say, I am scratching my Head trying to work out how to get at least a Ltr of fuel on Trex frame.

[KevinChiu123]

Hi, simon2469:
Thank you very much.

Yes, we are working on a conversion kit for the combination of Wren 44 and MD-8. It would be the same as what we did on the Align 700.

The heat is fine. The heat shield is for a much better protection.

For your fuel issue, I know someone melted 2 tanks together. (This is dangerous, once it leaks.......... )

Or, you may put 2 tanks side by side with a plate underneath them then go through the frames.

Or, I had been thinking about putting a MSR 975cc (33oz) under the base plate/engine. Of course, you need to have a taller custom made skid just like mine. However, I decided to put 2 MSRs~ 650cc (22oz).

[sunnyville]

What did you use to attach the fuel bottles to the frame?

[KevinChiu123]

We modified the airframes, designed the base plate, engine mount, & fuel tank mount then made them by CNC with alu. 7075.

For your reference/s.

[cbdane]

Having the fuel bottles that far aft is sure going to change the CG in flight as fuel level drops.

[KevinChiu123]

Thanks a lot for your advice, My heli's CG is just fine. ..^.*..

[cbdane]

Originally Posted by KevinChiu123

Thanks a lot for your advice, My heli's CG is just fine. ..^.*..

You're right. Not everyone needs the performance and agility of a well balanced machine.

[desertstalker]

They dont look that far back to me (the centre of the mounts seems to line up pretty well with the mainshaft). Would probably only need to slide them forward an inch or two (if anything, hard to tell with the shape of the bottles) to get it perfect (I assume that would be too close to the exhaust though).

That pic makes the tanks look further back than they actually are.

[cbdane]

Originally Posted by desertstalker

They dont look that far back to me (the centre of the mounts seems to line up pretty well with the mainshaft). Would probably only need to slide them forward an inch or two (if anything, hard to tell with the shape of the bottles) to get it perfect (I assume that would be too close to the exhaust though).

That pic makes the tanks look further back than they actually are.

I'm sure it will be fine. Especially with a flybarless system which will adapt to a shifting CG.

[helibeli]

What is the head rpm?it looks really slow or is it just the camcorder.

[KevinChiu123]

It is just the camcorder.

The Align 800's head rpm is 1650.

On the other hand, regarding the progress of my MD-8, we cut the driving gear, made the thread in it, then successfully installed it on the drive shaft of gear box for testing the temperature.

[ame]http://www.youtube.com/watch?v=Gk_hUklVbXE[/ame]

It is not too hot. We decide to let the engine drive the main gear without a clutch system.

[sunnyville]

Now that is interesting. What would be the advantage or disadvantage of not using a clutch? My heli uses one as do most other trainers. Is that down to the fact that they've all been converted? Because the Magnum 44 is no conversion and still uses a clutch. Does the clutch maybe reduce the amount of stress put on the second stage/gearbox of the turbine? Because here without a clutch you have more sideways force on the clutch shaft/bearings of the turbine. Just a theory.

[KevinChiu123]

My both Jetcopter and Wren 44 (Align 800) use clutch. We believe that a clutch reduces power due to the less direct hp output~ from gear box to the rotor head (i.e., friction eats up your output).

Of course, what you say is 100% correct~ "Because here without a clutch you have more sideways force on the clutch shaft/bearings of the turbine".

We will custom make a nut with a long shaft to replace the black bolt that you see now on the gear box shaft. The long shaft works the same as the clutch for reducing sideway force.

For any other turbine heli on the market, I believe that the majority of them still use clutch.

Anyway, keep you posted with any furhter progress. ..^.*..

[helibeli]

I wonder what might happen to the gearbox in an accident situation? I like the innovative gear cutting.

[cbdane]

AMA in U.S. may require a clutch.

[KevinChiu123]

Originally Posted by helibeli

I wonder what might happen to the gearbox in an accident situation? I like the innovative gear cutting.

If any accident happens , I believe that gear box will not be the only concern.
The engine must go back to the Wren for "complete" repair.

Thanks a lot for your compliment on the gear cutting.

[KevinChiu123]

Originally Posted by cbdane

AMA in U.S. may require a clutch.

Hi, dear cbdane: what is the major purpose for clutch?! why a clutch is required?

I know that a nitro engine needs a clutch at low rpm for seperation of direct output between engine and main gear. Especially for autorotation. Moreover, nitro engine is very responsive on throttle.

However, regarding turbine engines, we do not fly until the engine is at almost full power. During flight, we adjust only pitch. In other words, we don't need low range rpm at all.

On the other hand, once the engine quits, the one-way free-going bearing in the center hub will not rotate turbine's gear box.

Therefore, we decide to move the clutch away.

Is my theory correct?

Thanks a lot for your advice.