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HomeTurbineAircraftHelicopterTurbine Helicopters › Wren 2nd stage turbine removal
06-24-2015 10:08 PM  3 years agoPost 61
MattJen

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UK

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what the best way if any of doing this I was thinking of taking a feed from the tunnel feed to the gearbox

We used to fill our gear box with oil every 5hrs, the way we would do it is remove the back bolt from the frame spacer then use a syringe and squirt the 15ml into the gear box, then do the screw up.

If you run out of oil or forget to replace it as some did in the early days you would get a burning smell and lots of smoke and smell of oily fish, it would also burn the seals..

All The Best

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06-25-2015 07:46 AM  3 years agoPost 62
steph

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Hampshire England

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Hi Matt

No smell of oily fish but no oil in gearbox
I see your oil fed gearbox has larger bearings probably to compensate for the oil feed

The world is round you can run but you will always end up where you started from

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06-25-2015 02:34 PM  3 years agoPost 63
Chris Bergen

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cassopolis, MI USA

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Steph, A little story from about 6 years ago.

The 2nd Intrepid Turbine built, by me, with all the updates added from learning from the 1st machine, taught me a couple of very important things about Turbines and specifically the oil filled gearbox (which is VERY different than the Fuel fed and lubed gearbox which came out a few years later).

Per the manual I put in the requisite amount of oil (my memory says 10cc/10 ml, but may be the 15 that you mention). After the very first runup and hover I pulled the drain plug from the bottom of the gearbox to inspect the oil amount.

NOTHING came out... Empty....

So I refilled it with the 10cc (or 15) of oil and flew it again. Again I pulled the drain plug, and again NOTHING came out...

Well crap.. It must be leaking out, going forward through the seals into the exhaust area.

So in frustration I filled the gearbox almost to the top with oil.

On the next flight, which consisted of a 5 ft hover for about 2 minutes, all of a sudden this thick white smoke came pouring out of the exhaust, completely enveloping the helicopter which I now could not see through all this smoke!!

Luckily I was able to land the heli without damage but the thought racing through my head (and my mouth) was that just effing fried a $4000 turbine...

After calming down and letting the turbine cool down, it was noted that the gearbox was no longer green, more of a tan/sand color and the exhaust was COATED in burnt on oil residue... Damn....

I put in a phone call to Wren to see if they had an idea of what I had done to my engine, and after describing my procedure with the oil it was determined that since I overfilled the gearbox the pressure build up in the gearbox forced that large amount of oil through the seals into the exhaust. The seals were rock hard from the heat generated, which is what also turned the green anodizing to a tan/sand color.

I ordered new seals for the gearbox from Wren, cleaned the gearbox of all oil and filled it with ONLY the amount specified in the manual and flew the heli that way for the next few years until upgrading to the fuel fed gearbox....

I occasionally would add another few cc's of oil, maybe 5cc's to top it off every 6 months, with no further issues.

So, the moral of this story is, though you may believe that there is no oil in the gearbox, it's in there. It's coated all over the gears and sidewalls of the gearbox, being thrown around by the gears vs just laying in a puddle on the bottom awaiting the drain plug to be opened to just pour out.

One of the MAJOR differences between the oil filled gearbox and the fuel fed and lubed is the rubber seal just forward of the small pinion. This seal is what keeps the oil in the gearbox. In the fuel fed gearbox, there is no seal, its a bearing that allows the excess fuel to move forward in the tunnel, lubricating the bearings in the tunnel then out the exhaust.

So the question is, do you have a seal or do you have a bearing in the tunnel?

Chris D. Bergen

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06-25-2015 02:37 PM  3 years agoPost 64
Chris Bergen

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cassopolis, MI USA

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BTW, the picture that Matt has up there is a Fuel lubricated box, noted by the line going into the side of the box.

Chris D. Bergen

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06-25-2015 03:13 PM  3 years agoPost 65
MattJen

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UK

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the picture that Matt has up there is a Fuel lubricated box,

yes but the screw that we used to un do to fill the gear box with oil are in the same place on pred wren whether its oil/fuel fed. hence why I put this photo up.So Steph knew what I meant.

but for the sake of clarity here is my oil fed gear box, with the same 2 bolts that fit into the pred frames.

All The Best

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06-25-2015 05:26 PM  3 years agoPost 66
Chris Bergen

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cassopolis, MI USA

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Exactly right!

There was a third gearbox, with smooth sides, it doesn't have the drain port.

Chris D. Bergen

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06-25-2015 07:14 PM  3 years agoPost 67
steph

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Hampshire England

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So the question is, do you have a seal or do you have a bearing in the tunnel?
I have a seal in the tunnel and a bearing the bearing has a open side and a closed sealed side
I remember when I first got the turbine probably 10 years or so ago, I checked the oil in the gearbox then I thought there was no oil in there so I filled it with 15ml of oil when I flew the turbine white smoke came out just like you said this was my learning curve from that instance.

I understand the oil coats the gears and pinion and in the middle where the bearing sits is a well, oil sit in there 15ml is a lot of oil to be absorbed by one gear and a pinion yes today I refilled the gearbox before I flew and sure enough white smoke came out of the turbine exhaust what more can I say on that learn from other peoples mistakes I should have learned from mine

so another strip down and clean up replace the seals so on so forth

The world is round you can run but you will always end up where you started from

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06-25-2015 07:32 PM  3 years agoPost 68
Chris Bergen

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cassopolis, MI USA

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I was afraid of that...

With a new seal, put in your oil and go fly!! Don't stress about how much is in there, it'll be fine.

Chris D. Bergen

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06-25-2015 07:37 PM  3 years agoPost 69
steph

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Hampshire England

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its just the gearbox runs very hot and I am concerned its running too hot

The world is round you can run but you will always end up where you started from

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06-25-2015 11:37 PM  3 years agoPost 70
dgoss999

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UK - Lancashire

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Steph. Have you measured the gearbox temp (eg. With IR thermometer). I'm interested just how hot it is...

"Believe none of what you hear, and only half of what you see." • Benjamin Franklin

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06-26-2015 02:01 AM  3 years agoPost 71
MattJen

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UK

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the temp question on the gear boxes was raised back in 2005,

The whacky and excentric Bell Bloke did a war and peace on it, here is one of his posts taken from 2005

I will add, the reason he changed his oil every 7hrs and later 10 hrs, was because he was doing aerial film work with heavy camera and clocking up a lot of serious hours..

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.

All The Best

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06-26-2015 02:25 PM  3 years agoPost 72
steph

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Hampshire England

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Well its sad to say this but my predator is finally grounded taken out of service shelved due to the fact its a money pit and I can't justify throwing too much money at it at this time seems its just one thing after another that's going wrong with the second stage and gearbox.
So unless I can get a gearbox and second stage at a good price its shelved

Thank you all for your help

Steph

The world is round you can run but you will always end up where you started from

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06-26-2015 03:57 PM  3 years agoPost 73
MattJen

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UK

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sorry to hear this Steph..

What is it you actually need, I have a shaft tunnel, did you hear back from the person who bought my previous turbine..

Matt

All The Best

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06-26-2015 04:47 PM  3 years agoPost 74
Chris Bergen

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cassopolis, MI USA

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What else happened?

Chris D. Bergen

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06-26-2015 06:12 PM  3 years agoPost 75
steph

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Hampshire England

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What else happened?
while I was taking the second stage turbine apart one of the blades snapped on the turbine wheel it must of had a fracture of some sort
What is it you actually need, I have a shaft tunnel, did you hear back from the person who bought my previous turbine..
yes I did he sold it to a guy in the states for £650

I think what i have is probably going to cost too much to repair every time i repair something, something else pop up so that why i have shelved it

I need a complete gearbox and second stage to rebuild

The world is round you can run but you will always end up where you started from

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02-20-2016 11:15 AM  32 months agoPost 76
steph

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Hampshire England

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Getting interest back in my predator I was able to source this complete interstage and gearbox
Not sure what gearbox it actually is looks to me like it could be a mike baileys ?? anyone have any info on these box's

The world is round you can run but you will always end up where you started from

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02-20-2016 01:00 PM  32 months agoPost 77
Chris Bergen

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cassopolis, MI USA

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Bailey's were most typically blue. There was another scheister making similar gearboxes, Neil Keys I think his name was.

He had a thing in for Wren for some reason, copying their stuff and passing it off as the real thing...

It was a long time ago so I couldn't say if that's what you have or not...

Chris D. Bergen

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02-20-2016 02:36 PM  32 months agoPost 78
GyroFreak

rrProfessor

Orlando Florida ...28N 81W

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I have been following this thread as I have an interest in miniature turbine details. Not to own one, just love looking at the details and discussions of seals and bearings.
Steph, hope you are able to get this little frustrating whacky turbine going again, without incurring a bank loan.
Paul

I think about the hereafter. I go somewhere to get something, then wonder what I'm here after ?

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02-25-2016 12:09 PM  32 months agoPost 79
steph

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Hampshire England

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Received the parcel the other day looking at the second stage and gearbox all look in fairly good order so I 'll just check the gearbox for oil and modify the clutch assembly and fit to the engine

When checking the gearbox for oil it was packed with grease my question is
Grease or oil what is better or dose it make no difference for now I am leaving the grease in situ

Next question Grease what type is best for this gearbox is there a particular grease to use and how much grease should be in the box

The world is round you can run but you will always end up where you started from

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02-25-2016 06:12 PM  32 months agoPost 80
MattJen

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UK

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I personally never heard or seen grease in a gear box,
but if indeed it is a baileys gear box then I don't know as ive only seen one on the hobbyparts conversion but that was fuel/oil spray lubed gear box like the Wren one, not grease.

Can you put up a photo of in the inside of the gear box ?

I hope it is not a turbine techniques one..

All The Best

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HomeTurbineAircraftHelicopterTurbine Helicopters › Wren 2nd stage turbine removal
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