Home made jet engine

[Andy_GParticipant @andy_g]

Inpired by comments on the 'See through Jet Engine' thread, here's my engine:

 

 

 

It's based on the plans in Thomas Kamps' book and eveything except the compressor wheel (a turbocharger part) was made in my shed on my Chinese 7×14 lathe.

 

 

The turbine wheel was hacked out of an Hastelloy X disc with an angle grinder and a Dremel, but came out well, I think:

 

 

There's a fairly detailed write-up of the build on my website

Introduction

(Link)

 

First start-up

 

 

 

 

The subsequent run using liquid kerosene fuel

 

 

 

For the real massochists, an video of me mumbling as I assemble the parts:

I'm currently waiting for parts for a Hall-effect RPM sensor before I run it again.

Edited By Andy_G on 01/07/2022 09:31:25

[Andy_GParticipant @andy_g]

[HopperParticipant @hopper]

Beautiful to behold.

[Alan JacksonParticipant @alanjackson47790]

Superb

[Andy_GParticipant @andy_g]

Thank you!

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Brilliant ! I am really impressed with hacking out the Turbine with a Dremel and Angle grinder.

Keith

[JAParticipant @ja]

Have you made the jet pipe yet?

When I was an apprentice and at college in the late 1960s anyone suggesting that a model jet engine would work, let alone be made in a small workshop with simple tools, would have been laughed out of the room.

JA

[HopperParticipant @hopper]

Pulse jets seemed to be popular with model types back in the 60s. But a whole lot simpler than the above!

[Nigel Graham 2Participant @nigelgraham2]

Magnificent!

[Mike CrossfieldParticipant @mikecrossfield92481]

Very impressive. Superb workmanship, and model engineering of the highest quality.

[KWILParticipant @kwil]

For those really interested in these machines search

**LINK**

[KWILParticipant @kwil]

[KWILParticipant @kwil]

[Andy_GParticipant @andy_g]

Posted by JA on 01/07/2022 10:29:27:

Have you made the jet pipe yet?

I've made the tail cone, but it only appears in the first video – I want to confirm that the exit temperature is under control before running the engine up with it in place. I think that people who fly these things sometimes use an internal exhaust duct that they call the jet pipe – I don't have any plans to put this in a plane, so I haven't made one of them.

Thanks to all for the kind comments.

[Brian JohnParticipant @brianjohn93961]

That is quite stunning ! How long did it take you to make the turbine wheel ?

[Andy_GParticipant @andy_g]

Posted by Brian John on 02/07/2022 13:44:29:

That is quite stunning ! How long did it take you to make the turbine wheel ?

Thank you!

The turbine wheel didn't take as long as I thought it would – it was split over several sessions, so it didn't seem too bad:

• Cutting the blank and turning the profile;
• Slitting the disc into blades;
• Putting the initial twist into the blades;
• Cleaning out between the blades and the initial shaping (with an angle grinder);
• The first go at smoothing and shaping the blades;
• Second go at shaping, and carving the concave faces with a dremel.

Each of those took an afternoon, pretty much (some afternoons were longer than others!)

More details of the process I followed here:

Turbine wheel blank

Forming the blades

[John PParticipant @johnp77052]

Some useful download plans can be seen here from Gerald Rutten (zip files)
http://www.gerald-rutten.nl/turbines.htm

They use the same gas container as the early Shreckling engines ,the most thrust obtained from the engine that i made was about 6 lb ,i think the GR 180 in the plans above produces about 36 lb.

———————

https://www.turbomaster.info/eng/applications/compressor.php

shows the sizes of nearly all made compressor wheels and is a
useful reference.

———————————–
The 2 compressor wheels here (1st photo) were from Aliexpress ,the one on the left
is a K27 wheel 47.3 dia inlet and 73.9 dia od 14 blade
the one on the right is a TO4B 45.8 inlet and 70 mm dia od 16 blade.

————————————
The 2 compressor wheels shown here (2nd photo) , on the left milled from
2014 t6 aluminium 68 mm od for KJ 66 engine , the one on the right
is a KKK 5326 123 2038 cast wheel also for a KJ 66 engine.

—————————————
The turbine wheel seen here (3rd photo) is for Shreckling FD 3 /64 turbine engine
milled from 718 inconel 20 years ago, perched on top of the remaining 17 inch
of 2 3/4 inch dia inconel 718 bar .

It is perhaps not worth making a turbine wheel from solid these days
unless you already have the material and the means to mill them ,back then
ready made wheels were only just appearing from the GTBA when they had a
batch made for members of the organisation.

http://www.jetmax.ch sell ready made wheels from about 66 to 82 mm dia from
about 165 Euros which suit the KJ 66 engines and also the Gerald Rutten
turbines.

John

[BufferParticipant @buffer]

That's really good and I love the details like the engine mount, that really makes it stand out from the others.

Did you make your own spot welder too. If so which plans did you use or was it the Gas Turbine Builders Association spot welder made from a microwave.

Thanks

[Andy_GParticipant @andy_g]

Posted by Buffer on 02/07/2022 19:37:26:

That's really good and I love the details like the engine mount, that really makes it stand out from the others.

Did you make your own spot welder too. If so which plans did you use or was it the Gas Turbine Builders Association spot welder made from a microwave.

Thanks

Thank you!

Yes, I did end up making a spot welder, after trying and failing to TIG everything – I didn’t follow any specific plans, just used a larger than usual microwave transformer (from a very old commercial microwave) and replaced the secondary with the heaviest cable I could fit in there. It’s controlled by a 555 timer IC and a solid state relay. It packs quite a punch and welds 0.5mm stainless in less than 0.1 seconds.

 

A little more info

Edited By Andy_G on 02/07/2022 22:59:59

[Neil LickfoldParticipant @neillickfold44316]

Great stuff. Thanks for taking the time to post and take pictures etc.

[Andy_GParticipant @andy_g]

Posted by John P on 02/07/2022 17:26:35:

It is perhaps not worth making a turbine wheel from solid these days
unless you already have the material and the means to mill them ,back then
ready made wheels were only just appearing from the GTBA when they had a
batch made for members of the organisation.

http://www.jetmax.ch sell ready made wheels from about 66 to 82 mm dia from
about 165 Euros which suit the KJ 66 engines and also the Gerald Rutten
turbines.

If there are any aspirations towards high performance, then a commercially cast inconel turbine is a necessity. Unfortunately, they are probably less available now that they were ~15-20 years ago, as the co-operative DIY efforts have morphed into commercial entities, and the supply of parts to hobby builders has dried up. (There is nothing available via the GTBA – I am a member.)

About the only non-Chinese source is Jetmax, as you say, but taxes and shipping pretty much double the advertised 230 euro cost of a 66mm turbine wheel (and you'd probably want the matching inconel NGV which would cost the same again.).

There are cast turbine wheels advertised on Alibaba and other Chinese sites which are about half the cost of the Jetmax ones.

In any case, I thought that was too much money to sink into a project for me (I didn't want a jet engine, particularly: I wanted to *try to build* a jet engine) – the Kamps design is one of the few still available that will tolerate a home made turbine (even a stainless one), albeit ar reduced performance, which is why I chose that design – I was very tempted to try one of the original FD3 variants (since this is what had sparked my interest, back in the 1990s) but the Kamps is a much better design.

If you just want a jet engine, the answer is to buy one! 😀

There is a GTBA project engine coming to fruition that uses a radial inflow turbine (rather than an axial turbine as used in most of the model jet engines) that would allow turbocharger turbines to be used.

[John PParticipant @johnp77052]

Posted by Andy_G 03/07/2022 21:26:15

(There is nothing available via the GTBA – I am a member.)

About the only non-Chinese source is Jetmax, as you say, but taxes and shipping
pretty much double the advertised 230 euro cost of a 66mm turbine wheel
(and you'd probably want the matching inconel NGV which would cost the same again.).

There are cast turbine wheels advertised on Alibaba and other Chinese sites
which are about half the cost of the Jetmax ones.

In any case, I thought that was too much money to sink into a project for me
(I didn't want a jet engine, particularly: I wanted to *try to build* a jet engine) – the
Kamps design is one of the few still available that will tolerate a home made turbine
(even a stainless one), albeit ar reduced performance, which is why I chose that design
– I was very tempted to try one of the original FD3 variants (since this is what had sparked
my interest, back in the 1990s) but the Kamps is a much better design.

If you just want a jet engine, the answer is to buy one! 😀

There is a GTBA project engine coming to fruition that uses a radial inflow turbine
(rather than an axial turbine as used in most of the model jet engines) that would
allow turbocharger turbines to be used.

————————————————————————————

First of all you have made an impressive job on this Kamps engine design ,the EGT
is very low ,did you find out the top end speed and have you done any thrust measurements?

I used to be a member of the GTBA but let it lapse when they went on line only
as back then i had no internet connection , i still have one of the original GTBA
commissioned turbine wheels seen here in the photo along with a Wren
MW 54 wheel also there is a 66 mm wheel and stainless cast NGV
also from Wren. Since they disappeared these parts i guess have gone.
Some of these parts are seen here ,on the left Some Wren mw 54 parts
a bought turbine wheel , milled NGV centre from 316 ss , compressor wheel a
free-be from a collection of them, 3 off part machined diffusors.
Towards the centre top some milled 718 turbine wheels and the GTBA and
Wren wheels ,on the right some FD 3/64 parts , in the lower half a nearly
reclaimed disc of inconel most probably 713 from a scrap radial
inflow wheel.

I seem to remember that before the availability of cast turbine wheels
inconel slices about 6 mm wide were around the £35 mark ,that was over
20 years ago , by buying a length of inconel bar brought that price down to about
£8 to £10 ,of course you still have to slice it up by whatever means and the mill
the blades.

That is why that i said it would be a better option to buy a ready made wheel
as the real cost is only the difference from buying the material and the tooling
and the time minus the cost from the ready made item.

With that in mind the home made compressor wheel milled from the solid
seen here and in previous photo's is a similar situation the aluminium blank
probably about £5 or £6 plus all the work to get to finished job when you can buy
a new cast wheel for £14 + vat and free shipping does not make it really
worth while.Although i have to say that you do learn a lot in doing something like this
also as i wanted a reverse rotation wheel it is a simple matter to change
some of the axis polarities to be able to do this ,in the photo here is a wax
test cut reverse rotation wheel alongside the aluminium one.

Seeing the last part that you had written about the GTBA radial inflow project
is not really surprising as a complete rotor set is only about £35 for an engine
similar to the original JPX type engine .

The last photo here shows the much modified Shreckling FD 3/64 engine
installed in an airframe ,you can just see parts of the fuel tank in front of the
engine ,its bigger than the engine,the model has never been flown.
Most of the parts seen here were made 10 to 15 years ago.

John

[Andy_GParticipant @andy_g]

Posted by John P on 05/07/2022 15:35:50:

First of all you have made an impressive job on this Kamps engine design ,the EGT
is very low ,did you find out the top end speed and have you done any thrust measurements?

[…]

I seem to remember that before the availability of cast turbine wheels
inconel slices about 6 mm wide were around the £35 mark ,that was over
20 years ago ,

Thank you very much – That's an impressive collection you've got there.

I don't believe my EGT readings: I think the TC was waving about in the breze a bit too much to be credible. I will drill the NGV / tailcone to hold the TC nearer the turbine exit to get a more trustworthy reading.

I want to get the EGT and a reliable RPM reading before I run it again. I've got a hall effect sensor working, but am waiting for a suitable magnet to arrive from China before I can try it out on the engine. The intention is then to measure the thrust and run it up to 100,000 RPM. (After that, it'll probably sit gathering dust !)

I did try and buy an Inconel disc – it's difficult stuff to get hold off. I was quoted £75 for a 15mm length of 2.75" dia 718 (+£18 carriage + VAT). – that was the shortest I could get. I did have the offer of a couple of slices of a 6xx Inconel, but after the donor had killed two bandsaw blades without making much progress on cutting the bar, the offer was politely withdrawn.

Thanks for the interest,

[JAParticipant @ja]

Andy

I have follow this with interested and tried to restrain myself from making comments.

Unlike a big engine, which will have a pressure ratio greater than 4:1 (very much more on large modern engines), your little engine will, does, happily run without a jet pipe and rear nozzle. However when it comes to measuring thrust you will need these.

Fitting the tail cone would probably reduce the temperature of the turbine disc. Without it the disc is exposed to the exhaust gas temperure.

The thermocouple should be rigidly mounted. The one thing to remember with a thermocouple is that you are measuring the bead temperature, nothing else. How close it is to the gas temperature is a heat transfer problem (think conduction along the wires, radiation from the bead to the outside, etc). Even the big boys were happy with a reading within 1 K (they think in Kelvin). Running without a jet pipe would lower the bead temperature since it would be radiating to colder surrounds.

JA

The price of the Inconel disc seems reasonable to me (I feel have just paid nearly as much for a piece of Phosphor Bronze). Generally stockholders will keep very little of the stuff since big, important, orders have acceptable long lead times.

Have fun

Edited By JA on 09/07/2022 12:24:08

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