Wren 44 PTFE tube

[DenisFerrari]

Hi all, done 3 start-ip and some idle whit Wren 44 hely and I observed couple of drops only in the PTFE tube carrying small amount of fuel into the 2nd stage gearbox.
Of course fuel was on the tube coming out from the engine.
Maybe idle regime is still too slow to generate enough pressure to send drops of fuel into PFTE tube ?

Any suggestion is highly appreciated

Thank you and happy flying!

[yf222000]

From what I have noticed on my 44, it doesn't really pumps a lot of fuel into this tube to lubricates the gearbox at idle. However, once at flight idle or flight rpm, more fuel will be push through to keep the gears cool and slippery during flying. I don't know if this is recommended by Wren, but I opened up the rear gearbox cover and inspect the gears after the first few flights. Also noticed that there is plenty of fuel in the gears without any worries of it overheat or dries out.

[DenisFerrari]

Thank you!
I think it's not reccomended by Wren to open gearbox end , unlesss strictly necessary. Anyway, as you say, I think in my case is normal since so far I did only 3 idle runs. As told, I see fuel at junction between fuel coming out from motor and PTFE tube, but I believe fuel pressure at idle is still not high enough to push fuel on the other side , into the PTFE tube, thrugh the pin.
Think it's normal then.

[yf222000]

I think it's normal. I read the manual again last night. It mentioned that the only user serviceable and accessible area is the gearbox rear cover for inspection. That's why it included the special Delrin tool for that purpose. Hovers her a couple times and you will see more fuel being pump in the lub line for the gearbox. Of course it won't be completely filled like the Kero burner line. It will be sporadic droplets and sections of drops fills the line.

[DenisFerrari]

Originally Posted by yf222000

I think it's normal. I read the manual again last night. It mentioned that the only user serviceable and accessible area is the gearbox rear cover for inspection. That's why it included the special Delrin tool for that purpose. Hovers her a couple times and you will see more fuel being pump in the lub line for the gearbox. Of course it won't be completely filled like the Kero burner line. It will be sporadic droplets and sections of drops fills the line.

Excellent thank you!
I'll keep an eye after first hovers

[Wren Turbines USA]

The lubrication system of the 44 Heli only allows a very small amount of fuel (containing the 5% oil) to the front gearbox and what you are seeing is normal!!!

Ron

[MattJenner]

hi folks,
this was a test we did when i first had my MW54 which had the new fuel feed gear box system, prior to this we used to have sump filled system.

I apprecite it is 54 but the principle is the same, it starts off as a drip at idle and but as you increase RPM that spitting first becomes a flow that does soak the gear box with a fine mist.

A reliable system.

Anyway it was a just a vid me and bell bloke did to show how it flows as rpm increases.

[DenisFerrari]

Almost 30 flights done with my T-Rex 700 Jet with Wren 44 Hely, everything's great!

Just noticing that PTFE tube, at end of flight, normally has only 1 to 2 drops of fuel in it. I see fuel before PTFE tube , on the short transparent tube coming out from the engine and connecting on the metal junction where the 2 needles are, but I see very very few (1 to 2 ) drops of fuel in the PTFE tube.

Everything's looks great so I think that what I see is normal.

How is it in your Wren 44 hely's ?

Thank you

[cbdane]

Originally Posted by DenisFerrari

Almost 30 flights done with my T-Rex 700 Jet with Wren 44 Hely, everything's great!

Just noticing that PTFE tube, at end of flight, normally has only 1 to 2 drops of fuel in it. I see fuel before PTFE tube , on the short transparent tube coming out from the engine and connecting on the metal junction where the 2 needles are, but I see very very few (1 to 2 ) drops of fuel in the PTFE tube.

Everything's looks great so I think that what I see is normal.

How is it in your Wren 44 hely's ?

Thank you

This sounds right to me. On my Bergen, the PTFE tube made a low arc well below the turbine and frame of the heli so I always saw quite a few "droplets" of fuel in it after a flight, in the lowest part of the tube. I became worried about my new install since it doesn't typically show much fuel in the tube after a flight and I don't see much "action" through the tube at any moderate head speeds at which I'm willing to (carefully!) approach on the ground. The difference is that my new PTFE routing keeps the tube higher with respect to the gear box so a thin film of fuel seems to whisk right through without forming droplets. The last observation that put my mind at rest was to look at the bottom of the gear box during idle (being careful not to toast my face). Right at the fitting I can see a healthy amount of fuel being "suctioned" into the gear box, even at idle. A final test, of course, is the "puff" test at the end of the flight. Tilt the turbine end toward the ground immediately after shutdown. This will allow the excess lubricant/fuel in the gear box to spill out into the exhaust and generate a big "puff" of white smoke. This also should give good indication that the system is working.

[DenisFerrari]

Great...so I think it's normal

In fact, yesterday, just after a flight, I tilted laterally the hely and I saw white puffs coming out by exhaust ...I think what you're observing is exactly like what I see.

Good!

Thank you again