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HomeTurbineAircraftHelicopterTurbine Helicopters › Wren Primary Gearbox Oil
10-12-2005 12:40 PM  12 years agoPost 1
Bell Bloke

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UK

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Ok folks here are my findings, yesterday I purchased a little temp probe gadget from Maplins (BAR CODE- 4 891727 003155). It was only £7 / $10 so why not.
Now I figured that this maybe useful to monitor the gearbox temp because it's all too easy to neglect to change the oil when you should. It has been found that the oil is reluctant to drain out when you remove the drain plug this is due to surface tension. I have found that if you drain the oil from the rear mount screws while the turbine is still warm, it just pours out, every last drop. New oil can then be syringed back in, the whole operation takes only 5mins and there is no need to remove the engine. After 6 hours flying my oil was only slightly darker than when it went in, and it was only down by 3ml. So I'm changing mine every 7hours just to be safe.
As for the temp probe, well I figured that as the engine gets older there would come a time when the seals will need changing. When will this be? Who knows. So by monitoring the temp, this should serve as an early warning for anything abnormal.
Here are my results based on a cool day in England.(20 degrees C).
In a constant hover the gearbox temp reads 50 degrees C on the button and curiously when the motor is shut off, it climbs to 70 degrees C within 60 secs.
If you don’t have a temp probe here is what 70 degrees C feels like....
Just boil a kettle and pour the water into a cup, wait for 5 mins and stick your finger in. That's 70 degrees C!
By the time your Wren has stopped the temp will be 70 degrees C too.
I find I can only touch the primary gearbox for 3secs before it gets too hot.
So how's that for a rule of thumb/finger!
Hope this helps you folks, and that it takes away some of the guesswork in this area.

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10-12-2005 01:23 PM  12 years agoPost 2
NEIL2-UK

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UK - South East

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How HOT!!
Hi Bell Bloke

Where do you check your temperature... on the button?

Are you using the hypoid gear oil with EP additives to assist lube when the box suddenly dumps its oil?

Do you still keep the std Predator cooling fan in place on the clutch hub or have you upgraded to a larger fan?

Your Quote: "... when the seals need changing. When will this be? Who Knows..." Ask Wren.
But I guess the service manual that you got with the gearbox giving operation details, and oil specs, and temperatures, would give an indication of the wear rate within the box?

NEIL

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10-12-2005 02:02 PM  12 years agoPost 3
Bell Bloke

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UK

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Hi Neil, the oil I use is Castrol differential EPX 75W-80.
The stick on temp sensor is stuck to the bottom of the gearbox, and the fan is just the standard fan as machined by Wren. The display on the sensor is on a constant read-out LCD. I suppose I could ask Wren about the longevity of the seals on the box but these things are hard to life as are all things mechanical.
It depends of usage, loading and age, this much I have found with the cars I drive. If you store them and use them gently they seem to go wrong more than if you drive them hard (not thrashed) and on a regular basis. Wren, I think would be hard pushed to make any kind of life prediction on a seal as they do tend to wear out in there own particular time. Besides if Aston Martin or Lamborghini can't do it, how could anybody else. Still, even with all of these variables it still maybe possible to find a pattern if we all swap notes, this is good for us and the manufacturer. However it does rely on people being methodical and honest with their findings so as to build an accurate picture.
Ps. forgot to add, my turbine is running at 120,000 rpm, that's more than enough, for me at the moment!

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10-12-2005 02:53 PM  12 years agoPost 4
wolfdad

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Southern Maryland

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Interesting information and I concur with accurately and continuously documenting wear and failure data. Spotting a failure trend becomes very easy...one of the reasons I stay pretty anal about my FADEC data. I have already been able to ID and take action on a potential failure in the gas generator section.

Gearbox temps are a very interesting "talking point," since it seems that nobody knows what is too much or not enough and, Bloke, as you indicate, we have no idea on seal longevity....all on the frontier yet to be explored. I also have not seen anyone that has come up with a recommended oil change interval for the gearbox either. I would also think that a "run-in" period should be observed, with an oil change after that with a new gearbox.

wolfdad sends...

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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10-12-2005 04:27 PM  12 years agoPost 5
Bell Bloke

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UK

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Well Guys, just when you think you are being all methodical and thorough, this hobby pulls your pants down and makes you look an ass!!!
Just had to auto my Predator. Why? Well my own fault, when putting on the canopy I loosened the turbine temp probe plug that goes into the fadec. Result.... Turbine shut down! Well I won't make that mistake again, nor will I underestimate the power consumption of digital servos, like I did last week resulting in the same, failsafe shutdown. I tell you I really hate unplanned autos, it was my fault on both occasions and both times I've got away with it. So for all you turbine jet jockeys out there check your fadec plugs and don't make the same mistake as me. But then I'm sure you won't!
Really clocking the hours now!!!

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10-13-2005 09:56 AM  12 years agoPost 6
Bell Bloke

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UK

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Wolfdad, what did you find out in your fadec data?

RE "FADEC data. I have already been able to ID and take action on a potential failure in the gas generator section."

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10-13-2005 10:24 AM  12 years agoPost 7
richie1967_uk

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London UK

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can you guys wait a week before posting about having to do forced autos, I am that close to taking the plunge and ordering my MW54 Mk 3 and i dont want to be scared off!!! I was thinking of going up to wren on the 23rd and building it, however its a long way top go on my motorbike in this weather!! Did you guys build the kit on your own?

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10-13-2005 10:57 AM  12 years agoPost 8
wolfdad

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Southern Maryland

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Earlier this past summer, over the course of 4 or 5 flights, I had seen the "average" operating temp go up by almost 80° for no apparent reason (no significant change in ambient conditions, fuel, etc.). At about the same time, I also experienced a significant increase in fuel consumption (time per flight dropped by two plus minutes). When I spoke with the folks at Wren after sending them the FADEC data dump, they strongly recommended sending the engine back in. As it turned out, due to vibration from the pending gear box failure, two of the fuel nozzles had vibrated loose. The engine was repaired and returned and the gear box failed about a month later. No way to know what the source of the vibration (or even that the vibration existed until the failure) was at that point, however the engine probably would have been "toast" on the next turn.

wolfdad sends...

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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10-13-2005 02:34 PM  12 years agoPost 9
NEIL2-UK

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UK - South East

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Not A Vibration problem...
Hi Wolfdad

It is unlikely that any vibration from the gearbox would have caused such a combustion chamber problem as the heli would have been shaking itself out of the sky with that kind of vibration.

BLADEBENDER had a similar combustion failure about three weeks ago, and I do not think he is alone in the experience.

As you say it is good to keep checking the engine data and being aware of temperatures.

NEIL

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10-13-2005 05:47 PM  12 years agoPost 10
Bell Bloke

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UK

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Hi richie1967_uk, please don't be put off, all of these little glitches are due to my own stupidity. I only post them because they are little oversights that can be made, but should not be made. In posting my errors on this forum, I'm sure that some people may say to themselves, "I can't believe Bell Bloke doesn't check his fadec plugs before he flies." But there maybe some out there who say, "hmm, actually I wonder if mine are pushed all the way in."
Being a "newbe" to this hobby I am making simple mistakes that an "old hand" would not. My models are well constructed, with all of the cabling neatly routed and tied, I do try and check everything after every flight with all of my models, but every model is different and familiarization takes time. That is why I only tend to low level hover a model for the first 5 hours, which is my test period.
Recently I've been writing articles for Rotorworld showing my Electric Scale Helicopter conversions, this month it's my Hirobo Lama and a Bell 47G has featured in previous issues. Some people on reading them may think that perhaps I was some kind of an expert.... But I'm not.
Yes I can build a really nice realistic, budget scale helicopter, from an ordinary kit, and yes I convert them to electric because for me it's the most realistic sound this side of a Turbine, Infact my mates think that my Bell 47 sounds more like a "real" helicopter than my turbine. However all of my helicopters have suffered flameouts, in there initial settling in period, even the electric ones!
The thing is richie1967_uk, just think of it as, me making your mistakes for you so you don't have to. Besides I bet that you knew that digital servos use 3-4 times more power than ordinary ones, so that's one mistake you wouldn't have made, unlike me.
Joining a club rather than going it alone is a good move, because you see other people’s mistakes first hand and pick up tips, which is useful. So far I've gone it alone, so I'm learning the hard way.
So please don't be put off. This hobby is great!! I'm just trying to inspire, if I'm putting you off then I'd better stop writing.
Just get your Wren/Pred and have fun....
PS. Here is some of my electric stuff, my Bell 47 will fly for 25mins!
PPS. Many thanks Wolfdad for that info, I shall keep a close eye on things.

All are electric except the Skeeter, the only one left flying!

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10-13-2005 05:55 PM  12 years agoPost 11
richie1967_uk

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London UK

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No worries, nothing is gonna put me off buying the turbine, in fact i am gonna order it tomorrow!! I thought i would start with the MW54 Mk3 kit...build it and bench test it, then get used to starting and running a turbine. Next stage would be to buy the 2nd stage and gearbox and the heli!! (an xmas presi for myself).....so just to warn you, i will be asking question after question in the very near future!!!

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10-13-2005 06:11 PM  12 years agoPost 12
Bell Bloke

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UK

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richie1967_uk, I totally forgot to say, my engine was a "flatpacker" (kit) but it astounds me that you hadn't heard that mine was constructed by;
MR CHEESE...... a Norfolk cross breed dog of above average intelligence.......
A dog who has been consulted on many occasions for his technical expertise by the great and the good, within this Runryder forum.......even Peter Wales has a hotline to his kennel now!.......... MR CHEESE is a dog that makes Gromit look like a complete Wallace!!!

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10-13-2005 06:41 PM  12 years agoPost 13
richie1967_uk

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London UK

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now i know where the expresion "its a dog's life" comes from......Should i get the flat pack or spend 50 quid to get the kit with the pre balanced turbine?

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10-13-2005 07:50 PM  12 years agoPost 14
coolice

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Northamptonshire, England

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Hey Richie,

If you can make it down to WREN's on the 23rd for their open day and at the same time build your turbine there, then I would suggest doing it that way.
Not only will you be among company that can help you assemble & test your new pride & joy, but you will have a great day with some very nice people to.

If all goes to play I shall be there also, with Predator Turbine hovering around the business park one minute and enjoying the company the next.

Bell Bloke : You are not alone in the plug experience. Last year I to had a similar problem which after a call to WREN pointed me in the direction of the Fadec plugs. I have fishing line wrapped around the unit now making sure I do not disturb them during canopy removal fixes that.
.

Ian Contessa
Team Robbe SchluterUK
Midland Helicopters

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10-13-2005 08:04 PM  12 years agoPost 15
Bell Bloke

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UK

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I'd flatpack everytime, because it teaches you not to be afraid of your motor!
And when the time comes, which is a long time from now, you can change the bearings yourself. Just follow the instructions, don't skip bits and don't force anything because you don't need to. It's really very simple, all the clever difficult stuff is done by Wren. You don't need to send it back to be checked either, just use it.
I would feel loathed to tell anybody that I built my turbine, because that's taking credit for something that Wren has made so simple, besides Mr.Cheese would find out and then I would be in the dog house!

PS. Small tip, I made a tiny torque wrench from spring fishing scales.
I used this to make sure that all of the screws were to the same torque.
There are no torque settings, so what you do is tighten a bolt until it ''feels" right and then mark it. Then undo it, and use the spring scales to pull on the end of the allen key until it hits the mark, make a note of the reading and that's your torque setting.
I found that I had to pull 3lbs on an allen key 10cm long on the bolts that connect the interstage to the gas generator. Please note that it is not 3ft lbs because the allen key is not 1ft long. It is mearly a system to even the torque loads.
If you have a sensitive finger pull it with that and even the loads that way!!

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10-14-2005 06:09 PM  12 years agoPost 16
Bell Bloke

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UK

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Mr. Cheese, who would normally advise me on the thermometer technical data is unavailable for comment today, apparently he's still hung over after going out on the town with Gromit and his bitches following the world premiere of
THE CURSE OF THE WERE-RABBIT.
But my own research in this matter means that I can now tell you that the Probe Code is: GW57M Thermo/Clock
-50 - +70C available at Maplins.

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