Got a "Napier Gazelle" but need help

[TwoGears]

Hi everybody!
I'm here because I've accidently run into a old Napier Gazelle turbine engine.
Well, after a hard trip with this old piece of great engineering, back in my transporter
I finally brought it to my workshop. After the turbine was unloaded I immediately
started to examine it. But right after two hours I came to the conclusion that I need
help. Since there isn't much information on the internet about this type of engine
and I'm not a aircraft engineer, I'm here to ask you people for help, which are more
familiar with turbines than me.

Right now I'm investigating the starter box, and so far I can tell it consists of a huge
contactor (for the starter motor?) and some other circuits with capacitors and inductors.
But before I can say something I'll have to draw the schematics together.

Until then, maybe you can identify some parts on the pictures I've uploaded (see below)
I'll upload a lot more pictures soon.



Thanks,
Ben

[cursorkeys]

Wow! What a beautiful engine. It looks complete and in excellent external condition too.


Top Picture from left:

Well, the screen is obviously the compressor intake The casing behind it will contain the accessory gearbox for all the things like the tachogenerator, FCU/Fuel pumps, oil feed/scavenge pumps, starter-generator and overspeed limiting devices if they aren't integral to the FCU/Fuel pump.

I can see two ignition exciter boxes behind the intake at the top (red writing). One connection on each box should be the LT input and one should be the HT to the igniter plugs. The HT will absolutely kill you from these devices as it's many Joules unlike a car ignition system.

Underneath that looks like an oil distribution block (pipe has brown band which is convention for oil lines, black = air, yellow = fuel).

Underneath that is the fuel pump.

Underneath that is the fuel filter.

Underneath that is the oil scavenge pump.

Underneath that (not really visible in the pic) is the oil pressure pump. The silver thing is an oil/air separator on the scavenge pump.

Moving to the middle of the engine, the black rectangular assembly with the silver dome could be a valve pack for engine anti-icing.

The red blanked pipe is probably a compressor bleed for cabin heating or air winches etc.. If it is then it will need properly blanking before you run the engine.


Second picture:

Same really, except you can see the fuel lines to each burner can. and the large black pipe disappearing towards the end of the engine is likely compressor bleed for gas-generator turbine bearings or PT (power turbine) bearings cooling purposes.

You can see some sort of fitting at the end of each burner can. If these aren't blanked then there were possibly TIT (Turbine Intake Temperature) probes fitted and you'll need to get some probes or blank these holes.


Third picture:

Some more red-bunged pipes visible, the one at the accessory gearbox is a centrifugal breather pipe. The other one in the middle is likely to be another compressor bleed that will need to be blanked.

The big starter (starter-generator?) is visible at the bottom right. A monster like that will probably want 28V at 800A

Above the starter is a tachogenerator.

The oil tank is visible in the middle wrapped round the engine. This will take a special turbine oil which will hopefully be written on it somewhere (Wiki says DERD 2487 spec which is AeroShell 750).


Last Picture:

What an absolutely awesome exhaust! Oh, and you can see a radiant-heat shield for the oil tank and some oil feed/returns for the rear bearings



I've never seen one of these engines before so that is all complete guesswork based on engines I've seen and owned. But might be helpful to give you a start in exploring it maybe.

Where are you based?


edit:

Looking online this a rare beast! The UK helicopter museum have one (and a Bristol Belvedere) so it would be worth asking them for manuals: www.hmfriends.org.uk

edit 2:

I have updated my guess work based on the FlightGlobal archive docs so I look clever (I was mostly right...)

[cursorkeys]

Flight magazine have a full text description and some sectional pics in their 1957 archive:

www.flightglobal.com/pdfarchive/view/1957/1957%20-%200628.html

[turbochris]

heh heh free turbine.... just bring it to my house w a few cases of beer and we'll be on national TV in no time!

[TwoGears]

May 31, 2013 3:11:16 GMT -5 cursorkeys said:

Wow! What a beautiful engine. It looks complete and in excellent external condition too.

...

Thank you very much cursor keys! Due to your informations, the sheet and a lot of comparison work
the last days, I'm now a lot more familiar with the parts of my turbine here 
Although there are still a lot questions open right now and a few more have shown up.
Your hint with the colored bands around the pipes was indeed very helpful. At my first attempt discovering
the engine I didn't even notice those small bends but they deliver a lot of information.

The large black pipe (as mentioned under the section "second picture") has to be bleed air. Even the
bend around it says COMPRESSED AIR but I'm still not sure what for because it's intake is after
the PT-part. Maybe for cooling the reduction gear and/or torquemeter?
The drawings on the magazine you linked, doesn't really show where this pipe is leading to. On page 632
in the right lower corner there is an inlet shown for "6th stage (filtered) bleed air" which would match
with the compressed air the pipe delivers.
(Picture: Red = pipe / orange = air filter)



As you told, the green thing on the picture is likely for engine anti icing. I don't know about that but I can
tell that there are both oil and fuel pipes leading to this case.

The green marked one is still a mistery to me. It looks like a second oil distribution system. Or maybe it's just
for spreading scavenge oil? I don't know yet.

I'm also still not sure about the two red-bunged pipes on both sides of the engine. I lit in with a lamp but
either they connect directly to the diffusor chamber or through them right to the casing of the compressor
bearing case. This will need some more investigation.


Further I've found two new sensors and/or measuring devices, as shown in the following pictures:

1) Most likely some kind of oil temperature (or pressure?) sensor. Because on the pipe system it's
mounted on the bend says LUBRICATION.



2) Since this sensor is mounted directly beneath the reduction gear it maybe is the output of
the torquemeter.



I'll go on investigating next weekend. Until then I try to figure out the electrical schematics
of the starter box and how they have been connected
I also hope for a reply from the UK helicopter museum. Hopefully they have some more detailed
plans and drawings.

Maybe I'll also find out where the cracking sounds come from when I turn the turbine through
the torque ring. It doesn't sound like something is damaged. It cracks periodically and seems
to come from the power turbine or near it. It also cracks twice a turn therefore a loose blade
slipping it's mounting screws up and down, came into my mind but the cracking sounds kept
the same even when I turned the turbine more fast. They just came in shorter periods as I
increased the turning speed of the torque ring. However, the turbine turns perfectly and I hope
it's not that serious. If I can't find the origin of these sounds I guess I'll have to take the rear part
of the engine apart 


Again, thanks for the help so far.
Ben

P.S.: I'm based in western Austria and owning a turbine is not very common around here 

[turbochris]

that's probably the output for N2 rpm the torque meter is usually a pressure port but I'm not sure

[TwoGears]

Jun 3, 2013 11:57:29 GMT -5 turbochris said:

that's probably the output for N2 rpm the torque meter is usually a pressure port but I'm not sure

You won't believe how far this sentence led me in my research. After i read the whole part of the flight magazine about the Napier Gazelle and corresponding articles in earlier releases again and again it finally makes sense. I feel like a noob now, which indeed is good though.

I always had the picture of a combined shaft in my mind and never realized that the complete part from the free-power tuebine over the reduction gear to the torque-ring is standing by itself. And the remaining parts is the turbine itself. Also the secret about the torquemeter is clear now. It's just for controlling oil flow through the rear bearings.

I also got a clue that the blue part on the picture in my last post could be a oil lifting pump for less important parts of the turbine. But this couldn't be told from far away and needs some more research.

---

I also managed to find the FCU, which I also saw many times but didn't realize waht it really was until I ckecked some pictures I made.
But besides the obvious throttle lever I have no idea what the two other ones are for. Maybe one could help me out with some ides or
a few informations?



I also need some help about the oil. There seems to be no available distributor of AeroShell 750 oil around here.
Does someone know any distributor in germany, swizerland, austria or UK ?

[cursorkeys]

Jun 5, 2013 16:55:46 GMT -5 TwoGears said:

I also need some help about the oil. There seems to be no available distributor of AeroShell 750 oil around here.

In the UK I can Suggest SilMid (http://www.silmid.com/products/aeroshell-turbine-oil-750-1lt-can-def-stan91-98-2.aspx), they give great service and are pretty competitive. There are at least 5 others as well in the UK if you need them.

Jun 5, 2013 16:55:46 GMT -5 TwoGears said:

Also the secret about the torquemeter is clear now. It's just for controlling oil flow through the rear bearings.

That sounds interesting. Does increased torque adjust the amount of lubrication?
On the torquemeters I've seen they just use the displacement of part of the reduction gear train (the thrust on the gear due to torque) to adjust a flow of oil that then goes to a meter or pressure transducer (i.e the oil is just for sensing movement and thus torque).

Jun 5, 2013 16:55:46 GMT -5 TwoGears said:

[engine controls picture]

For the H.P cutoff, it's probably just on/off with no real center position. On some engines like my M701c-500 you have to move the H.P cutoff partially into the center while starting to starve the engine of fuel and keep the EGT in range but that is not normal for other gas turbines!

[turbochris]

I'm supposed to use 750 in my nimbus but run 500 w no problems. Type 4 ATF seems to be worth looking into. The torque meter works by the side load of the helical cut gears, which is proportional to the torque load. The side load pushes on a pressure regulator, more pressure is more pressure, it's fed by a restrictor so it will not affect the lube rate to the rear, at least that's how it is on my nimbus. Are there any magnetic plugs on the thing? You should live next door to me.

[ernie wrenn]

No ... I need the help with new ideas.

That small lever might be a start, idle, and preflight run up. The Rolls Royce has a separate control valve that must be opened to start and prove operation before full RPM.

[cursorkeys]

Jun 6, 2013 12:11:00 GMT -5 turbochris said:

I'm supposed to use 750 in my nimbus but run 500 w no problems. Type 4 ATF seems to be worth looking into.

I know quite a few people do use the wrong oils in mil/commercial turbines and no-one (that I know of anyway) has exploded yet. But, for less that cost of a single fuel pump you can buy the correct oil. We run these things out of service life and maintenance, and the oil is as much for cooling critical bits like bearings as lubrication.

A mate commented last night that we are getting far too complacent about using and abusing old turbomachinery and I think I agree with him.

Everyone can do what they like but it's worth a thought how much energy is in even a small GT's rotating assembly.

[turbochris]

we're pretty safe. We know what to look for. If you were to run your turbine at rated output for a long time as in a heli or boat then use the right oil. Watch the temps, watch the rpm, watch the oil pressure, watch the oil filter and magnetic plugs.

Substituting things on these engines is OK, ignorance is what blows them up.

[TwoGears]

Hello Guys,
Finally I'm back home with internet and WOW so many new posts! I didn't know where to start first.

cursorkeys
Thanks for the link of SilMid. Unfortunately it's not that easy to send something to
Austria and twice the effort for private orders. but they gave me a hint of a dealer in
Germany which indeed offers this kind of oil. I ordered 12 litres now, which should
be adequate for filling the turbines lubrication system and mixing some fuel for the
first few starting attempts which hopefully will be in near future

I misread something in the text about the turbine and it's indeed as turbochris
in the post below yours described. It's not for controlling any lubrication.

At the weekend I'll go on discovering my turbine. I'll have a look at this ON/OFF lever
to be sure it has really just two states. Last time I pulled it the middle position indeed
was very smooth running. So your theory could be right on this.


turbochris
Thanks very much for clarifying the functionality of the torquemeter.
I can't remember any magnetic plugs near the torquemeter but there are a lot of sensors
around the engine I didn't discover yet and/or know the purpose of.
I'll have a look at the weekend.


@ernie wrenn
So the real purpose of this lever will be a secret until my first try to start it.
It likely could be as you told. since the scales range is very small it likely could
be some adjustment for idle speed or something. It also has two range limit screws.
I also will have a more close look on this at the weekend.


I'll keep you up to date. Thanks for helping so much!
Slowly I begin to understand this kind of motor more and more.

See you guys,
TwoGears

[TwoGears]

Hello guys!

Was absent a long time now, due to my job. But I spent the whole weekend with my Gazelle.
It's cleaned, the complete oil has been replaced with AeroShell 750. The former oil looks the
same and has the same viscosity. I think it had the same DERD-Standard like AeroShell 750.

Ich also checked if the turbine and all the gears turns without any noises and cracks by turning
the starters clutch. It was a whole succeed! So I'm looking forward to get that thing on fire soon.

At the moment I'm a little bit stuck with the starter box. I've gone through all connections and
drew down some schematics. But there is the problem that I have two very similar circuits in there.


This is the starter-box:



As you can see, there are two circuits which are not connected in any way. First I thought the
right one (Schematic 2) is the one to connect the starter motor. But after retrieving the schematics
and viewing some pictures I took when I got the turbine, I tend to the left one.
I realized that I accidently removed some captions when I cleaned the box. But they were on the
pictures. They just showed that the outputs of the left circuit were (Bat+ / Bat- / STARTER)


Schematic 1:
My favourite because it has a timer which is directly controlling the relays without the inductance in the
line. My thoughts on this is that when you connect the battery the starter motor is first served via the
power line where the inductance reduces the huge current. This leads to some cheap soft-start effect.
After some time (timer settings) the second power line is switched on and the motor is served directly.
Although, I'm not sure if those, in my eyes small, power relays can handle the currents.
And I'm thinking about to re wire the whole thing and use the huge relay from the right circuit.
I also think that K6 (a cut external relays) is meant to be some ON-button or something.




Schematic 2:
This one looks more like a circuit which can handle the powers of the starter motor.
Although I share the theories with the left circuit (Schematic 1), this one seems to
work properly too.
Because of the huge relays it doesn't need any soft-start. But what is that parallel
inductance for? It's quite useless because of the main power line.
This also has some kind of ON-button whcih can be connected to conector-pin Nr. 2



However, I hope you have some more experiences on circuits like this. Otherwise I've the starter
motor still removed for testing the circuits without initially driving the whole gears and turbine wheels.
But I want to hear your thoughts on this before I start testing, because a damaged starter motor
would cause a huge delay in my project 

Thanks for the help.

[cursorkeys]

Glad it's all going well so far.

Be very careful operating the starter without a load, if it's series-wound then it will overspeed without a load. Do you have any of the electrical manuals, they should show the motor winding arrangement.

Are those 'inductors' cored? If not then they are probably just coiled wire there for their resistance. They will have some self inductance with air but it will be negligible.


Personally I'd rewire it. Because it looks like a hobbyist made it in the first place and I wouldn't trust it. A welded relay contact could mean the starter fails before you could abort the start and get the batteries disconnected.

If K4 is an Albright SW200 then it will do a kiloamp no problem. I use SW200s for all my high-current switches, they seem very reliable.

You can get fuses that work great at these current levels: www.thetoolboxshop.com/mega-fuses-and-holders.html
I use the 500A ones and they are quite happy with the 5 or so seconds that the GTD starter pulls 800A for.

I've also put a battery disconnection switch from a big truck on my battery box. It was either that or keep a pair of bolt cutters around for piece of mind