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Bad Design ?

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John Stevenson08/04/2014 18:37:14
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So doing the final checking today on a Rolls Royce Trent engine compressor blade on ower test bench.

 

 

These are very high value items made from an alloy of Titanium, unobtainium and megadoshium.

 

Hours of work and many knuckles go into these at all points of the manufacturing process before they are fitted to the hub.

 

They fit into the hub by the dovetailed machined end clearly shown on ower expensive test fixture. However to my mind just a push fit into a hub isn't really good enough for a blade that has to do this amount of work so today I modified the design, prior to RR approval and drilled and tapped two M6 holes in the bottom the take two M6 coach bolts.

 

Anyone still following my reasoning ?

 

Edited By John Stevenson on 08/04/2014 19:16:07

Speedy Builder508/04/2014 18:42:56
2592 forum posts
207 photos

I love your workbench - A tool for everything and everything in its place !! just like mine.

BobH

Phil Whitley08/04/2014 18:45:29
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I think you are going to mount it on top of your biker helmet to increase your awarness of surrounding traffic by making your head spin, or maybe on a block of mahogany as a presentation peice. Wait...............I can hear a noise in the background, perhaps it is just your Teachers Grousing?

Phil

Phil Whitley08/04/2014 18:50:28
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Building a wind generator? is that an alternator I see next to it?

Phil

John Stevenson08/04/2014 19:15:02
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Seriously it is a compressor blade out of a Trent engine.

The bit next to it is an out runner motor which is part of a post just put up in the "What did you do today " thread.

Phil Whitley08/04/2014 19:18:23
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Come on now John, everyone knows that RR make turbine parts out of Oscillating Eqinishium, and thats as rare as!

Phil

Phil Whitley08/04/2014 19:20:29
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Yes, I can see it is a turbine blade, but I am puzzled as to what the motor is, I will look at the other thread.

Phil

Phil Whitley08/04/2014 19:32:55
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Sorry, I wasn't familiar with the "outrunner" motor, got it now, but you have me baffled, something to do with a wind tunnel perhaps?

Stewart Hart08/04/2014 19:42:51
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Your going to bolt it to a chunk of wood to make it into a bit of sculpture, so the M6 coach bolts are a good idea.

Stew

V8Eng08/04/2014 19:46:19
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All done with a battery drill as well!

wink

Edited By V8Eng on 08/04/2014 19:46:51

JasonB08/04/2014 19:48:08
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How are you going to tighten up the coach bolts? You usually turn the nut not the bolt.

Is that a bottle of your "special tapping fluid" in the background?

J

 

Edited By JasonB on 08/04/2014 19:49:52

DrDave08/04/2014 22:28:51
240 forum posts
47 photos

Compressor blade. Outrunner. If that is going into a ducted fan I'm standing well back!

Ian P08/04/2014 23:23:44
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Posted by John Stevenson on 08/04/2014 18:37:14:

So doing the final checking today on a Rolls Royce Trent engine compressor blade on ower test bench.

They fit into the hub by the dovetailed machined end clearly shown on ower expensive test fixture. However to my mind just a push fit into a hub isn't really good enough for a blade that has to do this amount of work so today I modified the design, prior to RR approval and drilled and tapped two M6 holes in the bottom the take two M6 coach bolts.

Edited By John Stevenson on 08/04/2014 19:16:07

I see you have changed tactics compared to the subject of ejecting Morse tooling from tailstocks You were fairly firm expressing a case for not modifying the wrong thing to accommodate something that was already OK.

Surely here it would have been better to make the matching female dovetail so you did not have to drill and tap the M6 holes, (or just stick it in place with BluTack (also available in white now!)

If I had one of those blades I would hang on to it until I collected a full set,

Ian P

John Stevenson09/04/2014 00:52:23
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OK guys most of you have guessed it's a scrapper.
No idea what's wrong with it. Got it sent in by the company who polishes the blades for RR.

They were given this one as a show sample and the holes in the bottom are just for mounting on a plinth.

Drilled OK but tapping started to be a bitch so I drilled over size for tapping at 5.5 so it would tap easier. Still enough thread to hold it for it's intended purpose.

Even scrap there has got to be a few bob's worth there and I dare say RR don't hand these out to anyone.

Jason,

The "tapping fluid" is for the central heating on the odd day I don't have the wood stove on.

Sod the H&S hic..........................

john kennedy 109/04/2014 08:28:59
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I hope it wasn't my fault, i used to make the dies to forge those blades. We sometimes had a few of those fully finished and polished blades kicking about at work. They had been rejected for the tiniest inclusion found,although they were all ultrasound tested before they left. I'd hate to put a price on a finished one but 35 years ago a billet of titanium to make one cost £600.

Geoff Theasby09/04/2014 08:42:38
613 forum posts
17 photos

I have an RB199 turbine blade taken from a Tornado after 'Desert Storm', it's encrusted with solidified molten sand. It is also drilled with a series of air cooling holes so small they will only take a piece of 36swg wire.

Regards

Geoff

frank brown09/04/2014 12:04:20
436 forum posts
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I saw a programme about the manufacture of Rolls Royce engines. These blades are "grown" as a single crystal.

Frank

Ian S C09/04/2014 12:41:13
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I see you have an anti terrorism weapon there in the background, There is one in Air New Zealand's head office in Auckland. During the first Fiji coup, an attempt was made to hi jack a Air NZ aircraft, but the co-pilot hit the hijacker on the head with a full bottle of Teachers, and saved the day.

There are about as many designs of blade root as there are types of engine, probably more as engines change as they develop. Ian S C

Brian Wood09/04/2014 12:46:27
2549 forum posts
39 photos

Hello John and others,

In the real thing, the blades are left slack in the socket which explains the sound of spoons rattling when one of these engines windmills on the wing.

In fact all the blading, including the hot end with fir tree roots is slack to allow for expansion from heating in duty.

The hot blades run at 200 degrees centigrade above the melting point of the expensive alloy they are grown from as single crystal items. Melting in service is stopped by the gale of cooling air pumped throught the blading from the root, it escapes from rows of small holes spark eroded through the the blade aerofoil into the cooling ducts inside. $10k each on completion!

The big fan blade you pictured is hollow with a honeycomb interior, more manufactuing magic!

Brian

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