Turbiner

When the bearings became noisy on my P70 I decided to replace them myself. I am no expert on turbines, but I have built a Wren kit and have 20 years experience of model engines. The strip is not difficult. I have just a few tips and info.

Make sure you have a very clean workspace before you start.
Take photos as you take it apart, this will help when you rebuild.
Mark the positions of the compressor and turbine wheels and replace them in the same position.
The mainshaft nuts are both left hand thread.
Probably the most difficult part to remove is the turbine wheel, it is very tight, you will need a press or some kind of puller to remove it.
When replacing the turbine wheel on the shaft I suggest you put the mainshaft in the fridge for a couple hours and heat up the turbine wheel, this way it will fit very easily.
Note the which way around the bearings are, the preload has to be applied on the correct side of the bearing.


If anyone has rebuilt a JetCat, maybe they could add some useful tips or info.

Guillermo Ibanez

My Feedback: (1)

Hey Turbinator, very interesting post

Please post more pictures about the assemblying.

How did you take out the turbine wheel? I mean where did yo place the extractor legs? In the bearing? Because I think there is no space for placing the extractor legs between the bearing and the turbine wheel.

Is not better to remove the turbine wheel if you place all the assembly (turbine wheel and shaft) in the fridge? When a shaft is freezed its diameter will be reduced and when the turbine wheel is freezed, do the shaft hole be enlarged? Doesn't a hole circular walls be contracted increasing the hole diameter when freezed instead of heated?

Do you have both nuts tightening torque?

Guillermo

Guillermo

F86_SABRE

I think the problem with turbine stripping is:
1. how to position the bearings in the correct manner so that they will not come out
2. balance the rotors properly (preferably assembled). I have not, as yet, seen any available good home balancer for the do-it-yourself type of person.

Reuben

simon1

My Feedback: (1)

WOW, a man on a mission! So far its almost the way I did it. A couple of pointers tho, just before you pull the combustion chamber off the fuel manifold, with a felt pen just mark on the Diffuser the position of the glow plug hole, that mean when you put it all back together the combustion chamber is in the right orrentation. Another pointer is when you slide the combustion chamber back over the fuel manifold, just have a look down the burner tubes to make sure all the injectors are seated in the tubes, as it quite easy to miss, and they will be in the heart of the C Chamber which you dont want.
I always just put a drop of neat turbine oil on each bearing once they are reseated on the shaft, the rear bearing will be starved of oil until the mist works its way down the tunnel when the turbine is started for the first time. Not sure if its needed, but it cant hurt.

Keep it up, we may start a revolution.

Regards Simon

frema

He Turbiner.
I stripped several p80 engines ,and p60 and p60se , and many many more.

The only thing you have to be carefull with is the feulring at the back of the diffusor.

When you take this out , there is an oring , and when thats damaged , you have a leak.
So you have to be very carefull with what you do.

I never saw a p70 engines from inside ,thank you for that.

I never knew the p70 was the only one who has the radial diffusor.
The p60se got the normal axial radial diff ,and also the p80 got it.
I have a very special p60se , because it was the first one with the machined compressor.

You did the right thing about replacing the bearings.
I also use a press to press the turbine wheel from the shaft.

and when i replace it ,i just heat op the turbine wheel.
With the compressor i do the same, heating up the compressor for a few seconds , and it falls of , and when replacing heat , and then push on the shaft , you have a few seconds time to set it on the marking ,and then you cant move it , just place the spinnernut , and finished.
i am building engines from 2000 ,and i develop small and big one ,and also build my one kj66 turbo prop and and the smallest turbo prop in the world (65mm).

frema

Oh just forgot to ask you , what is the size of the turbine wheel and compressor?

Xairflyer

My Feedback: (1)

Great stuff Turbiner this is what we want


If you mark the shaft, compressor & turbine wheels you should not need to balance, even if the shaft and wheels have been re balanced on a balancer, you still need to remove the compressor wheel again to assemble the engine.

Xairflyer

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How is the combustion chamber attached to the diffusor

simon1

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Hi, it doesn't , there is a lone socket bolt on the bottom of the turbine case which goes into a small bracket on the C chamber, and it slots on the ngv on the back.
Regards Simon

drdoom

My Feedback: (9)

Start a thread with More information and Pictures of your Micro Turbo Prop.

jetnuno

Great thread....

At least some of us dismistifying the turbine top secret expensive world

Xairflyer

My Feedback: (1)

Please start new threads for each turbine strip, this can be a P70 one, If we keep to the same titles e.g. "Simjet 2300 Strip" they will be easy to keep track of over time, once there is a good number we can start another thread with all the links to each of them so in a few years time they will be easily found by people.

Turbiner

The compressor and turbine wheels on the P70 are 66mm. Same as the old KJ66.

Gerald Rutten

Hmmm..., very interesting!

Turbiner

The bearings are lubricated via a T in the fuel supply, the arrow shows a small needle inside the tube which, I guess, meters the supply. Not sure on the best way to check that this is working properly, as it is a very small needle, a spek of dirt would block it. Shows the importance of good fuel filtering.

Xairflyer

My Feedback: (1)

Yes it is just a restrictor to limit the flow, some just have a simple hypo needle pushed into the oil pipe.

JetCatJimmy

So this needle will lubricate both front and rear? Interesting! This is a great thread by the way!!

JetCatJimmy

What do you mean by the mist working its way down the tunnel? You're talking about the kero mist flowing along the turbine shaft?

mr_matt

My Feedback: (10)

Careful, there is a filter in that sliver tube. If you pull the 4 mm tube off the downstream end of the filter, you have to be incredibly careful when you put it back on. If you get any dirt on that side it can clog the oil feed to the bearings!

The P-70 is a diametrical shrink of the P-80, just as the P-180 is a shrink of the P-200.

When you mark the rotating parts to put them back together remember that you need to account for the relative motion you will get when tightening the nuts. If you have access to a balancer, you really should balance the whole turbine as a completed assembly when you are done.

Good luck, the pictures look great BTW!

Turbiner

Appreciate your input Matt. I see what you mean about the lubrication tube.
It would certainly be ideal to balance the shaft as a complete assembly after the turbine is built, however, I am not sure what system is used to do this?

Turbiner

Thought I would mention bearings and where to get them. For the P70 you need Full complement 608 size Silicon Nitride Ceramic Bearings 8 X 22 X 7.

In the UK, you can get them from http://jmprecision.co.uk/index.php?pr=Home_Page @ £39.50 a pair you wont get them cheaper, however they do look a bit different from the original German ones (photo), I have fitted these in mine and wait to see how long they last.

Wren Turbines http://wrenturbines.co.uk/ also have them listed @ £52 each, these are GRW German bearings and might be a better quality.

In the US, Flightworks inc http://shopping.netsuite.com/s.nl/c.ACCT103531/sc.1/.f also list GRW bearings @ $85.95 each.

Also Boca Bearings http://www.bocabearings.com/main1.as...&pg=10&mfr=306 also GRW bearings @ $94.95 each.

It is also advisable to replace the pre-load washers which are also available from JM Precision.

The bearing on the left is the original JetCat and the other one is from JM Precision.

simon1

My Feedback: (1)

Here is a picture of the the little bracket that the socket head bolt screws into. This is the P80, but sure its the same on the P70.
The 2nd picture is the back of the C Chamber that sit in the NGV to keep it all secure.
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quist

My Feedback: (198)

US bearing cost $170, hopefully the engine is correct when completed.

Jetcat USA does the job for $250 parts included.

hmmmm, I think I will continue to send the motor to Jetcat USA. But this is an interesting thread.

Bryce Watson

My Feedback: (6)

Dad always told me, "Always take your car to the dealer", but he never did. [sm=biggrin.gif] So after watchin him and learning how to work on cars including tearing down and rebuilding a 400 big block on my first car, that's all I do these days; Is take em back to the dealer.

1st, because at least I have a warranty afterwards. [sm=shades_smile.gif]

and

2nd, cause I just don't like getting my hands dirty anymore.

johnnyjet

My Feedback: (4)

Turbiner,
Thanks for the photos of the P70.[sm=thumbup.gif]
One question, how difficult was the rear bearing to remove from the bearing tunnel?
Thanks,
Johnny