ALU. Rotor. SHHHH!TOP SECRET.

[Bob Monkhouse]

Ps. what a beautiful engine and an even more beautiful aeroplane, there nowt to send a shiver down your spine than the sound of a spit and the sight of one doing that classic roll.You lucky bugger.

[fil_auto]

Indeed Sir..... even though I\'m far more interested in modern stuff.... with age one realises that these are some seriously impressive engines / planes... and to be frank could well have been a v good idea to soak more of the opportunities when a child!.... events, garage workshop, learning the ropes etc etc....

Am pretty sure he\'s got another fuselage in the making atm! :mmmm

Ps. what a beautiful engine and an even more beautiful aeroplane, there nowt to send a shiver down your spine than the sound of a spit and the sight of one doing that classic roll.You lucky bugger.

[Bob Monkhouse]

Going back to the heat concerns of the alu. rotor. These things are expected to make11000+ rpm. An engine that is making those kind of numbers isn\'t going to be doing 20000miles between rebuilds, we\'ll see how they do on test. Bob.

[fil_auto]

Yep, fairplay and back to the thread!:Thumbs-up

Will be watching this Bob with baited breath! sounds v interesting.... :3gears-lh

Going back to the heat concerns of the alu. rotor. These things are expected to make11000+ rpm. An engine that is making those kind of numbers isn\'t going to be doing 20000miles between rebuilds, we\'ll see how they do on test. Bob.

[TiddlesRX7]

Hasn\'t someone put one of them in an old Rover?

[Bob Monkhouse]

Whats that, an aluminium rotor or a merlin engine? Rover actually campaigned a gas turbine engine in a race car in the sixties(thats a jet engine). Someone also put a Merlin in a Modified Ford Capri in the seventies, that was apparently rather quick!!!By the way fil, Iam an orphan (well, my old mans an ex parrot and I\'m sure I could hurry mumsy along) so if your dad wants to adopt someone to work on his Spits. and the Merlins I\'m your man!

[Bob Monkhouse]

Sorry for being a bore, but is it a mark IX spitfire? It seems to have a four bladed prop and also a bubble canopy, I thought the bubble canopy came with the later five bladed props on the griffon engine. They ran 18psi of boost on the blower apparently.

[najiru]

Going back to the heat concerns of the alu. rotor. These things are expected to make11000+ rpm. An engine that is making those kind of numbers isn\'t going to be doing 20000miles between rebuilds, we\'ll see how they do on test. Bob.

Fair point that if you\'re happy to accept you may need to replace the rotors every so often in order to get the extra performance then no probs. Are you willing to tell us what alloy and temper has been used just out of interest? I\'ll stop rabbiting on now :Yawn
 
As for a composite rotor I\'m not too clued up on high temp resins. The highest we use if bismalemide [BMI] which I think you can take to about 230C. After that you\'re looking at polymides which go to 300C ish but I don\'t know how either these would stand up to the fuel/oil. Could always use carbon reinforced aluminium or ceramic lol, not sure anyone is going to shell out for something like that though! Maybe the F1 boys.
 
Be interested in how this goes, I hope it\'s a success as this is the sort of thing we need people to be doing. Sorry if I\'ve seemed a bit negative :p
 
btw Tiddles there are a few merlin engined cars, not least \'The Beast\'. A quick search on google/youtube should find you some amusing videos. Check EVO magazine\'s site as they did a feature on The Beast a while back

[shaunwil]

I suppose the other thing to consider is what coatings are available to aid in getting the temps out of the engine and away from the rotor.

http://www.camcoat.com/1.Thermal%20Barriers/Thermal_barriers.html

Shaun

[d6277n]

Cool thread. Love the sound of Griffons and Merlins, or any of the big old V12s for that matter. IIRC, good Merlins are getting pretty rare now so those might be worth a fair bit.

Composite rotors is a tricky one. If the heat soak temperature for a rotor is in the low hundreds of degrees C, then things like BMI/polyimide-based composites or similar may well have a chance. There will also be higher temperature systems someday, it\'s all in the chemistry.

The thing that worries me is that you\'ve got a transient much higher temperature when the flame front contacts the material, and the local environment is full of lots of nasty reactive oxidising species. Given that carbon fibre is essentially just carbon + "stuff," it\'s not going to be great in a high temperature oxidising environment - you may find that it disappears incredibly quickly.

In theory, you could put a composite centre section (over a metal former) where the temps are lower and the environment less harsh, and then put metal around the outside. It would require some clever high precision manufacturing processes and serious consideration of coefficients of thermal expansion, bonding methodology and the like. No idea if it\'s actually possible.

Chris.

[chrisJDM]

i agree this is a awesome thread and great reading, i know nothing about what you are all talking about but its still great to read :Thumbsup!

[najiru]

As you say thermal expansions will probably be the biggest problem with covering carbon composites as they have very low expansions and most suitable metals have fairly high. Where we link large machinings with composite skins we often get more load coming from the differences in thermal expansion than we do from flight conditions.
 
The coatings Shaun linked to were interesting though and would possbily do the trick. One last concern on this would be thinking where the heat goes, there may need to be an additional thermal path to the centre of the rotor in order to effectively cool it.

[od404]

I love threads like this, lots of good points being thrown about.  I would say from a fatigue point of view you are looking at two main areas; high cycle fatigue caused by mechanical loads (combustion pressure mainly, assuming the rotor is perfectly balanced for analysis sake) and low cycle fatigue cause by heat cycles.

The problem I see with the rotary compared with pistons is that at all times, part of the rotor will be being subjected to combustion temperatures which overall is likely to increase the overall temperature of the rotor during operation.  The entire piston is likely to see lower overall temps, but a higher difference during the cycle.  A bigger swing in temps is generally worse from a fatigue point of view, unless the material temps have been raised sufficiently to reduce the materials properties.

I guess we can only discuss all this in theory, unless someone wants to run such an analysis on a rotor...

The idea of using composites interests me too from this point of view, but I have little experience with these materials myself.  My day to day job involves structural analysis of large diesel engine components, most of which are cast iron (even our pistons), so this is where most of my experience comes from.

It\'s great to see these threads as it helps me to learn new things

[BlitzBoy]

When ya cutting the apex groves into the Rotor Bob?
So it seems we have three people in the Rotary community doing Billet Rotors.
Bob
Eastcoastrotary
Hayward

[Timrxmotors]

Going back to the heat concerns of the alu. rotor. These things are expected to make11000+ rpm. An engine that is making those kind of numbers isn\'t going to be doing 20000miles between rebuilds, we\'ll see how they do on test. Bob.

Not worth making then,my 12A engine revved to 13,000+ rpm,with cast iron rotors!