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Early Jet Engine Development


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I have had the accompanying article since it was published in the 1954 Aeromodeller Annual (when I was a boy!).  It's a very interesting account by the author of the article,  Mr. W. Ball, relating his post war development of his designs for rocket and pulse jet engines, (large) delta radio controlled aircraft, and- axial jet engines! 

 

This was a good 30 years  before the success of the UK team led by Jerry Jackman, in making that first micro-turbojet flight, in 1983. 

Interestingly, towards the end of the entertaining article, as he relates, tragically, the results of 10 years of work were destroyed in the Great Floods of January 1953  (I remember them well- who says that Global Warming is new??)

 

Now- was this a man before his time?  There's a cutaway illustration of Ball's jet engine- I am not familiar with jet engine design, but some of you may know how practical the design was- or not?

 

There is no real way of telling.  Unless some of you may have more information?

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Edited by Tosh McCaber
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I remember a series of articles in model magazines in the 1960s on the same subject. Was that a follow on development or a rehash of that original article?

A most fascinating series of articles to a young modeller, and I read them all several times, but I never really knew whether to believe it or not back then as it seemed almost science fiction (or wishful thinking).

I too would love to hear any first hand information from back then.

 

Dick

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I am doubtful, that the project was successful. The drawing seems to be a rehash of full size axial flow motor, in principal it could have worked if it could be built.

 

The first issue would be the materials of construction, these tend to be high nickel materials. I understand that many, if not all use commercial turbo charger impellers, reworked, are used in models today

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The next issue is engineering a multi stage compressor stage axial flow engine . Again I understand most, if not all are centrifugal single stage compressors in models. Keeping it together is the next issue at the revs used. I understand that the bearings are an issue, ceramic balls appear to be used in models. Keeping it all together is, well, not that easy

 

Lots of challenges, could even a enthusiastic modeller manage it, at that time?

Edited by Erfolg
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In the mid 60s I was working with J L Scott Scott the rocket man and also an avid aero modeller and engine expert assisting ED . Our dream was to produce a small gas turbine , The compressor was machined on a cleaver adaption of a Gorton milling machine to produce 3D ,  John did all the "maths " and it came out at 140,000 rpm !! At that time my proper job was to come up with a bearing , for rocket turbo pumps that would do 70,000 and last long enough to get the craft into orbit . It was a self lubricated hydrodynamic self aligning bit of kit , the basis of which is used on many baby jets of today .

The turbine was genuine turbine material of the day ,which eludes me at present  did it run ?? not really   , and when it did eventually the back end melted !

Great fun 

cheers

Google JL Scott Scott if you have an interest in British Rocketry  

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Typically materials such as Inconel, Hastelloy, Stellite were used and available at the time period indicated.

 

There are a number of issues with them, typically they are (or were) not readily available, Perhaps more significant to the average guy, is that they are incredibly difficult to work, in that they work harden readily, this means that cutting, filing, machining is difficult. Typically a light cut on a machine tool, skids over the surface, a slightly heavier cut, gets below the surface taking more of than you intended, leaving a work hardened surface. Next is welding causes much higher shrinkage than is normally expected.

 

In my day the blades would be typically held in place using (so called) fir tree root, where the hub and blade were in shear due to centrifugal forces, in axial flow machines.

 

Keeping the bearings cool was achieved by air flow, into that area, in addition to other measures.

 

Building such machines at small size must be a real challenge (even today). I suspect that is why the present model turbines are centrifugal types, rather than axial flow, just living with lower compression ratios than axial flow turbines in principal can achieve, with improved lower fuel consumption.

 

Assuming that something was built I suspect that it would have failed at the rotational speeds required to power a model.

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2 hours ago, Erfolg said:

Typically materials such as Inconel, Hastelloy, Stellite were used and available at the time period indicated.

 

There are a number of issues with them, typically they are (or were) not readily available, Perhaps more significant to the average guy, is that they are incredibly difficult to work, in that they work harden readily, this means that cutting, filing, machining is difficult. Typically a light cut on a machine tool, skids over the surface, a slightly heavier cut, gets below the surface taking more of than you intended, leaving a work hardened surface. Next is welding causes much higher shrinkage than is normally expected.

 

In my day the blades would be typically held in place using (so called) fir tree root, where the hub and blade were in shear due to centrifugal forces, in axial flow machines.

 

Keeping the bearings cool was achieved by air flow, into that area, in addition to other measures.

 

Building such machines at small size must be a real challenge (even today). I suspect that is why the present model turbines are centrifugal types, rather than axial flow, just living with lower compression ratios than axial flow turbines in principal can achieve, with improved lower fuel consumption.

 

Assuming that something was built I suspect that it would have failed at the rotational speeds required to power a model.

 

I am sure an enterprising company could make one.

 

Question is would anyone pay for it? A "simple" centrifugal compressor type is expensive enough. Perhaps more crucially, they are also demonstrably "good enough" for our purposes...

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I'm sure that Alec, you're correct.  I've had subs to most of the model mags one way or another since 1954 (threw out 1200 a couple of years ago- nobody wanted them!), but I must say I didn't see any rebuttal.  However, I do find it hard to believe that development of complex jet engines took place in a model shed(!) that he told us was drowned by 10 feet of flood waters!

 

Anyone else remember any articles regarding it being a con?

 

However, I really do like his delta designs!

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It has almost certainly a bit of kite flying, if not a deliberate con.

 

It is noy just me then, as Paul also moves out of the obvious plane of the rotating components. Again I did not realise the revs that these model turbines revolve. Just keeping the rotor components together has to be a major issue, without the temperature issues.

 

Like others the company I worked for produced rotating turbine type products, also doing some contract work for others. Again in my early youth, I was assigned to assist on a out of balance over speed rig. My role was from memory was to essentially stand and watch. On one particular occasion, the rig was approaching the first critical whorling speed, where massive vibration was encountered, after a number of attempts at achieving the designated revs, the principal engineer was called in. He simply drove through the revs range. Some time later I heard that another overspeed test on another site (same company, same division) had a failure where chunks of the containing enclosure were recovered from some miles away (according a news paper). I was afraid at the time, realised that I was perhaps lucky with my experience. All of this was done at ambient temperatures. I seem to remember all that was being measure was constant shaft running oscillations, vibration levels, and frictional forces.

 

The blading on the fir tree attachments on the female parts was achieved using a long (perhaps 15-20 foot) broaching machine, well outside the DIY enthusiast.

 

I am assume that outside of hot rotational components, the materials are probably steel and Stainless Steel (high, nickel, chrome steel)?

 

Just do not believe that it was possible in  the 50s for the average Joe, or even a highly skilled and well resourced guy in his shed/workshop to build a sucessfull axial flow turbine. I suspect that is true today at model scale manufacturers, or we would have seen at least one demonstrated somewhere.

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35 minutes ago, Erfolg said:

It is noy just me then, as Paul also moves out of the obvious plane of the rotating components

 

Full size turbines undergo destructive tests to demonstrate the effectiveness of blade containment on their nacelles.

 

I can't see any such structures present on any model turbines...

 

 

 

Edited by Nigel R
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46 minutes ago, Erfolg said:

Just do not believe that it was possible in  the 50s for the average Joe, or even a highly skilled and well resourced guy in his shed/workshop to build a sucessfull axial flow turbine. I suspect that is true today at model scale manufacturers, or we would have seen at least one demonstrated somewhere.

 Never mind the moving bits in the turbine, in the '50's the average Joe wouldn't have been able to put together a reliable 10 channel the radio to have any reasonable level of control. 

 

PS the quoted 26,000 rpm (max) seems awfully low to me.

Edited by PatMc
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