My Wren 44 Turbine T-Rex 700 - Sneak peak

[DenisFerrari]

On both my Wren 44 helys, I've always used fuel line, then burner priming procedure as they're described in the manual (an like Mike Murphy by Wren UK suggested me) and I never had a single problem during first flight or every time fuel line circuit is open or been modified or got partially empty.
...my 2 cents

[Calil]

Hey Dennis!!

I do the same. The problem was that the filter it self was allowing entering air in the line, creating tiny bubbles. Now I know why I almost crashed it! I'm happy I found out!

[cbdane]

Something doesn't make sense. If the filter is in the high pressure line (downstream of the pump), as per the manual (i.e. not on the suction side) then there shouldn't be a tendency to draw in air or create cavitation bubbles. I suspect you may have just been seeing trapped air working itself out of the fuel system and, as Denis points out, this should be taken care of with the initial purging process before the first engine start. In my experience with the 44 (over 4 years of flying it), this filter design has been fine.

[Calil]

cbdane

I tought the same but even with after all the procedure Dennis pointed (that is in the manual) I put the helicopter in the vertical position and I keep taking the bubbles out the filter and the thing never ends. So I changed the filter, put a jetcat filter, and changed the position, now I will use the filter here:





I have been helped by the guys who flies jets for over 12 years already so I think I have a very good support besides the great support you guys gave me

Another thing is on the way is that I will change the Y (3x3x3) for a 4x3x3 so I'll eliminate the festo before the Y.

I ordered also a lot of 3mm tubes from Wren. I'll change it when it arrives to clear tubes instead of the green ones so I can see bubbles more easily.

[KevinChiu123]

Is it possible that the wren filter was not tightly sealed?!

[Calil]

No way. Everything was checked carefully

[Calil]

La commedia è finita!

Finally after almost a month it's ready for another test. Much improvement was done (like biger fuel lines between the UAT and the pump and bet the pump to the Y festo(that will be changed to a 3x3x4 as soon it arrives). The UAT now has 2 fixation points. There is no regulator, I'm using a A123 baterry. The pump uses LIPO.
This canoppy is a previous used one, I have two original canopies that I'll adapt later.

[KevinChiu123]

Congratulations~~~

[CZorzella]

Please share some footage when you get this bird to fly. It looks awesome!

[KevinChiu123]

I have a question, just a thought~

Don't you think the rear plastic skid seems to be lower than the front one?

The weight loading on the rear end seems to be heavier than the front one.

What if it snaps?! Is it possible to happen?

I have not used any plastic skid yet........ How strong is it?!

Is it possible that your tail blades/vertical fin might touch the ground/grass?!

Is there any possible way to reinforce it?!

[Calil]

Actually the CG of the heli is perfectlly balanced, It's just the picture that make it looks heavier on the back.

These plastic skids are very stronger but has a lot of (I don't know if this is the right word) "elasticity"? and they saved all the other parts in my auto rotation because the rear one was the one that broke.

when I grab the helicopter by the top of the DFC head, I see the CG is more in the front. After filling the tank and putting the battery, it becomes perfect balanced.

[Calil]

Originally Posted by CZorzella

Please share some footage when you get this bird to fly. It looks awesome!

I promise I will

[Calil]

Ok guys another "safety upgrade". I realize that the wires here:



Were touching the edge of the carbon fiber frame. That would be a disaster someday, then some protection was needed:



Don't worry about the festos after the solenoids, that will go out as soon as the new tubes arrives.

[KevinChiu123]

Great!!!

Enjoy your excellent heli !!!

[cbdane]

Originally Posted by KevinChiu123

Is it possible that the wren filter was not tightly sealed?!

Originally Posted by Calil

No way. Everything was checked carefully

Very strange. Either there is a leak in the filter or there isn't. It's a machined aluminum housing with a single seal which had to be leaking. Furthermore, even a small leak would not normally draw in air if the filter was truly in the high pressure line after the pump. If it wasn't, we're back to entrained air from somewhere else in the system. My brain is always handicapped by logic; sorry for that and just trying to be helpful.

[KevinChiu123]

Thanks a lot for cbdane's concern.

Regarding the wren filter, what happened to me was this following incident~

There was a little bit air trapped in the filter.

We did not get the air out of the filter until we consecutively and gently knocked on the filter for 1-2 minutes~ within this process, the engine and pump were still running.

Then, the filter has been working properly so far.

On the other hand, my MD-8's major problem came from the new, but suspected to be bad, Hanson UAT. However, since I changed the new one with my used Hanson UAT, MY MD-8 flies great!!!

Based on the owner's manual, Wren recommend owners use only BVM UAT. I have bought 3 of it from USA.

Most important, no one will be so stupid to use a Wren 44 heli to test whether the Hanson New UAT is good or bad.........

I just simply get rid of it........

Best luck to all of us~ Fly with safety is the only concern.

[Calil]

cbdane

I'm very gratefull for your help, don't get me wrong. But what I did: I put the helicopter in the vertical position. And I stayed about 10 minutes getting air off the little filter. It never stops. I was tired after "tapping" it for so long. If the air just was formed inside the filter, after so many time tapping it, it continues forming air bubbles, then I realize it was it. I opened it, resealed it, and same thing was happening.

Now the filter is in the vertical, it's a jetcat filter, much bigger. Let's see how it works, I'll test it sunday.

Kevin:

I'm using the BVM UAT. With such a bigger investment, I would never risk using a not so known UAT. I'll keep to the already tested itens. Best of luck for us both

[Calil]

Hello guys

After a flameout (probably air in the line fuel) and a rebuild I'm facing a new problem. What I believe beeing static interference.

Well, I'm hoovering it normally (still afraid since the last flame out where I had to autorotate it). And guess what? Everytime I land the turbine shutts off. So, what you think? Take this carbon out and move the ECU to the plastic and also away from the fuel line (may be static from the fuel pump coming through the line?)

Remember I made this carbon base to the ECU, I believe may be it's conducting a lot of static

[KevinChiu123]

Hi, Calil:

Is the fuel line pinched as 90 degree "rectangular"?!

Or, just an incorrect image from camera?!

[Calil]

Originally Posted by KevinChiu123

Hi, Calil:

Is the fuel line pinched as 90 degree "rectangular"?!

Or, just an incorrect image from camera?!

no, that's the pre-build image, just to show the carbon plate behind the ECU. That was like that just to keep the line close when I was building.