another tip-jet find

**pgkevet** · 30-04-2012, 09:24 AM

**dillwhacker** · 30-04-2012, 10:36 AM

Interesting, that.
Wasn't there a heli (Russian maybe) that had Ram-jets on the tips, and no main motor to drive the rotor? Always seemed like a nice idea - really simple mechanically. Could even use centrifugal force as your fuel pump - sort of self regulating too!
Anyone fancy a couple of small pulse jets on the tips of a 700 for starters? Could be a lot of fun. Would look good in the dark!

**trillian** · 30-04-2012, 11:52 AM

I went searching for info on Voljet and wasn't seeing anything but ran across this .pdf doc. They were funded by Saudi investors and ran into some tech problems at first and then various issues with red tape and politics, eventually running out of money, then having some renewed interest in the early 1990s only to have that scuppered by Iraq invading Kuwait. http://hoytstearns.com/NaglerScans/Liberatore1.pdf

**pchristy** · 30-04-2012, 05:56 PM

Don't know if this has been covered in earlier threads, but what about the Fairey Rotodyne?

Late 50's / early 60's, I well remember the excitement and publicity that surrounded this aircraft! Unfortunately the din from the tip jets was such that no-one with normal hearing would allow it anywhere near a city centre! Great shame, as it was a truly revolutionary aircraft!

**pgkevet** · 30-04-2012, 05:58 PM

That document presents an amazing and at times sad story..incredible indeed.

**dillwhacker** · 30-04-2012, 07:04 PM

Interesting comment in the vid of the Fairey Rotodyne..."for landing the tip jets are re-lit".
What did it do in normal forward flight? Autorotate like a gyro-copter-thingy?
What were the tip jets? Ramjets?
Anyway, I want one!
What's the tipspeed of a 700 ?
What sort of speed do ramjets need - I thought almost supersonic?
I can feel some research coming on....

**Gixxer** · 30-04-2012, 07:17 PM

Originally Posted by dillwhacker

Interesting, that.
Wasn't there a heli (Russian maybe) that had Ram-jets on the tips, and no main motor to drive the rotor? Always seemed like a nice idea - really simple mechanically. Could even use centrifugal force as your fuel pump - sort of self regulating too!
Anyone fancy a couple of small pulse jets on the tips of a 700 for starters? Could be a lot of fun. Would look good in the dark!

A great design and I can't understand why it never took off (excuse the pun). The only downside is you need an engine (or maybe a small turbine or even electric power) to get the ramjets up to operational speed, but the design is very simple, with no moving parts in the ramjets, so they're effectively like a gyrocopter on steroids

... and they do look well at night.

**dillwhacker** · 30-04-2012, 09:54 PM

I like this idea - I have done so since I was a kid & tried to make a ram-jet work with some steel tubes and a fuel feed pipe and a stick of wood spinning round in a power drill. Never got any thrust from it - just flames and smoke. I did make a working pulse-jet at school - very noisy and quite awesome! Used razor blades as the vane valves. Needed a blowtorch to start it! Modern valve-less pulse jets look really fun.
Imagine a 700 size, with a potty little 450 motor and 3S LiPo just to spool it up - a litre of red diesel as fuel (50p), get to 2500 RPM and hit the big red 'light jets' button on the TX....or am I dreaming again?
Come on you engineering types - give it a try! How much fun do you want?

**pchristy** · 01-05-2012, 08:32 AM

Originally Posted by dillwhacker

Interesting comment in the vid of the Fairey Rotodyne..."for landing the tip jets are re-lit".
What did it do in normal forward flight? Autorotate like a gyro-copter-thingy?

Yes,in forward flight it became an autogyro, like the Jamed Bond "Little Nellie"

IIRC, for take off and landing, compressed air from the twin turbo-props was fed down the rotor-blades to provide some thrust. When full vertical capabilities were needed, fuel was added and lit creating a sort of ram-jet - albeit one with a separate air supply.

It was when the tip jets were lit that it became too noisy to be practical. Wonderful idea, though. Shame it was never properly developed. I'm sure the noise issue could have been overcome.......

**pgkevet** · 01-05-2012, 10:11 AM

a superb quote from the site below..

from Hiller HOE-1 / YH-32 Hornet helicopter - development history, photos, technical data

For this role the Hornet lacked what we now call 'stealth', as it could usually be heard by the enemy and the glowing engines could be seen from a long distance. Hiller once claimed 'the Hornet's sound range compares favourably with that of a conventional-powered helicopter' but without an intercom system the pilots had to scream at each other to communicate. The museum owning the only remaining flyable example of the 17 Hornets built received complaints from neighbours a mile and a half away when they last flew it.

The high drag of the ramjets meant the blade angle had to be set to a very negative angle when power was cut, and this led to the Hornet plummeting at 15mps during auto rotation. Only a very skilled pilot could arrest this descent just before the ground

**pchristy** · 01-05-2012, 05:10 PM

There's a pretty good article on the Rotodyne here:

Fairey Rotodyne - Wikipedia, the free encyclopedia

which confirms most of what I recollect from the time. It looks as if they were well on the way to solving the noise problem when politics once again messed up a world beating project! How many times have we heard that?

As an aside, the prototype was measured at 113dB at 180M!!! Brings our noise limits into perspective, doesn't it?