- Thread starter Misterg
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Misterg
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Misterg
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Probably before mine!
Misterg
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Nice spun intake
I've just weighed all the bits of mine and it is over 1.2kg without fasteners. (I know I have built some parts heavy, as I haven't been concerned with flying it), but <1kg is a tall order.
Misterg
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Tail cone is finished!
The tail cone is supposedly increases the thrust of the engine by managing the gasses coming through the turbine blades. The engine will run without it (sometimes better than with it) but I wanted to get it made so I could call the engine finished. It's the sort of thing that people tune and play with to get the best performance from the engine, but knowing very little, and wanting to start somewhere, I've gone with the one in the book.
I took the inner cone that I'd made before, put it back on the mandrel in the lathe and very gingerly used a 1mm diameter end-mill to cut the three slots for the support vanes. (The cone is being pressed onto the mandrel by the length of copper pipe over the tailstock centre.)
The outer cone is made to match the ID of the NGV, so there's a step between the NGV and the outside of the cone. I used a bearing tool to swage the mounting ring down at an angle until it matched the shape of the outer cone.
For better or worse, I followed the book's suggestion to fit the support vanes into slots in the outer cone and weld them on the outside. After cutting the slots (1mm end mill again) the outer cone and mounting ring were spot welded together (the tips need a clean!)
The support vanes are 0.9mm 316 stainless with tabs on the inside ends for spot welding to the inner cone
I modified the wooden mandrel I'd made to form the outer cone to hold everything concentric for welding together. I'd hoped that by cutting the wood away local to the welds and covering the remaining wood in foil that it would survive long enough to get a few tacks in place, at least.
It just about did, but I had to take it off the former to weld... Which was really tricky! The vane is 0.9mm, and the cone is 0.5mm. I thought I would be able to melt the excess length of the vane into the cone. It's lucky I had a practice first, because I burned the cone away big-style whenever I tried that. The only thing that worked for me was to try and make a tiny fillet weld between the cone and each side of the excess length of vane. I ended up using pulsed DC at 33A, 30% background, 30 Hz and 30% duty per one of Jody's videos.
This is as good as it got (the gas lens is to purge the inside of the cone - it worked very well, again.):
I scraped most of the ugly off, very, very carefully in the lathe.
Part way through, I found that one side of one of the welds wasn't properly fused, so I put it back on the welding bench to touch it up, and promptly blew a hole through it! I must be improving, because I managed to fill it in again without creating too much mess.
It was nicely concentric with the turbine wheel, but had pulled out of shape around the welds - putting it back on the mandrel shows that it was the ends near the welds that have sprung out; the main curved parts are still OK. I can't see it being of very much consequence, but we'll see... If there is a 'next time' I would make up an aluminium mandrel (instead of the wooden one) that could be used as a backer when welding.
I made some fiddly little mounting brackets to pick up the NGV securing screws:
They were bolted temporarily to the rear of the casing to line them up while they were spot welded to the mounting ring (tape for a bit of clearance).
Done!
What a fiddly, nerve racking part!
(Dunno why I polished it - it'll be a blackened mess the first time I try and light the engine...
)
Thanks for reading!
The tail cone is supposedly increases the thrust of the engine by managing the gasses coming through the turbine blades. The engine will run without it (sometimes better than with it) but I wanted to get it made so I could call the engine finished. It's the sort of thing that people tune and play with to get the best performance from the engine, but knowing very little, and wanting to start somewhere, I've gone with the one in the book.
I took the inner cone that I'd made before, put it back on the mandrel in the lathe and very gingerly used a 1mm diameter end-mill to cut the three slots for the support vanes. (The cone is being pressed onto the mandrel by the length of copper pipe over the tailstock centre.)
The outer cone is made to match the ID of the NGV, so there's a step between the NGV and the outside of the cone. I used a bearing tool to swage the mounting ring down at an angle until it matched the shape of the outer cone.
For better or worse, I followed the book's suggestion to fit the support vanes into slots in the outer cone and weld them on the outside. After cutting the slots (1mm end mill again) the outer cone and mounting ring were spot welded together (the tips need a clean!)
The support vanes are 0.9mm 316 stainless with tabs on the inside ends for spot welding to the inner cone
I modified the wooden mandrel I'd made to form the outer cone to hold everything concentric for welding together. I'd hoped that by cutting the wood away local to the welds and covering the remaining wood in foil that it would survive long enough to get a few tacks in place, at least.
It just about did, but I had to take it off the former to weld... Which was really tricky! The vane is 0.9mm, and the cone is 0.5mm. I thought I would be able to melt the excess length of the vane into the cone. It's lucky I had a practice first, because I burned the cone away big-style whenever I tried that. The only thing that worked for me was to try and make a tiny fillet weld between the cone and each side of the excess length of vane. I ended up using pulsed DC at 33A, 30% background, 30 Hz and 30% duty per one of Jody's videos.
This is as good as it got (the gas lens is to purge the inside of the cone - it worked very well, again.):
I scraped most of the ugly off, very, very carefully in the lathe.
Part way through, I found that one side of one of the welds wasn't properly fused, so I put it back on the welding bench to touch it up, and promptly blew a hole through it! I must be improving, because I managed to fill it in again without creating too much mess.
It was nicely concentric with the turbine wheel, but had pulled out of shape around the welds - putting it back on the mandrel shows that it was the ends near the welds that have sprung out; the main curved parts are still OK. I can't see it being of very much consequence, but we'll see... If there is a 'next time' I would make up an aluminium mandrel (instead of the wooden one) that could be used as a backer when welding.
I made some fiddly little mounting brackets to pick up the NGV securing screws:
They were bolted temporarily to the rear of the casing to line them up while they were spot welded to the mounting ring (tape for a bit of clearance).
Done!
What a fiddly, nerve racking part!
(Dunno why I polished it - it'll be a blackened mess the first time I try and light the engine...
)Thanks for reading!
Misterg
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Making a stand.... (Not against anything, just a stand.)
If Youtube is anything to go by, a lot of people seem to fasten their engines to a piece of 2 x 4 with some builder's band or hose-clips for testing. I wanted to try for something a little more elegant and 'jet engine-ey'.
Plan A was an aluminium support with lugs riveted to the outer casing. I abused my little wood bandsaw again to cut out some 2mm 1050 aluminium sheet:
Bent it round and welded the ends together:
Tacked it to a base plate:
And fillet welded it all around (using 1050 filler).
I haven't reached instagram standard yet, so I had to hide my shame by dressing the weld back to a smooth fillet. It was easy enough to take the lumps off with a round file, but after messing around with abrasive paper to smooth it out, I bit the bullet and got a soft wheel for my angle grinder (a Norton Rapid Blend fine / medium refining disk ). Not cheap, but it worked very, very well. Didn't clog on the (very) soft ally and didn't gouge or dig in either.
You'll notice that the lugs have gone - I went off the idea of riveting to the casing, and didn't want to use nuts and bolts through it. Instead, I made a doubler out of 0.5mm stainless sheet with some nuts welded to it that, in turn, could be spot welded to the casing and used to hold the engine onto the stand.
The first time I tried to make it, I welded the nuts on before bending the sheet - it went all shapes! It was a lot better bending the sheet first, but it still needed a few taps to straighten it out again afterwards. (I clamped a curved piece of copper under the nuts when welding them on.)
I eventually got it laying reasonably well against the casing, and, as far as I can tell, square.
Spot welded in place and buffed up.
I'd hoped to anodise the stand and leave it natural colour - it was a bit of an experiment as to how the welds would look compared to the sheet. I checked it straight out of the anodising bath and wasn't really happy with it - There is a little bit of difference between the welds and the sheet, but again there are mottled and grey areas (most obvious on the flat area bottom right). I don't know why this seems to happen with the 1050 grade
(maybe I need to try a de-smutting bath, but I don't see why pure Al should need that ?)
So, as before, I decided to give it a little colour to disguise the unevenness. I thought a neutral grey colour would be best, so thought I'd try my black dye cold (I've only ever used the black dye hot before to get a solid black). After two minutes it took on a great 'gunmetal grey' colour that I thought would be perfect. Colours normally bleed out a little during sealing, and I didn't want this any paler so gave it another couple of minutes.
To my disappointment, it didn't really bleed at all, and after sealing it came out very dark. Not an unattractive colour, but not what I was aiming for - there's a sort of blue-ish tinge to it in some lights.
Cosmetics aside, I'm sure it'll be OK.
It fits where it touches
Overall, happy with that.
It's also the last piece in the jigsaw - Meccano time next:
If Youtube is anything to go by, a lot of people seem to fasten their engines to a piece of 2 x 4 with some builder's band or hose-clips for testing. I wanted to try for something a little more elegant and 'jet engine-ey'.
Plan A was an aluminium support with lugs riveted to the outer casing. I abused my little wood bandsaw again to cut out some 2mm 1050 aluminium sheet:
Bent it round and welded the ends together:
Tacked it to a base plate:
And fillet welded it all around (using 1050 filler).
I haven't reached instagram standard yet, so I had to hide my shame by dressing the weld back to a smooth fillet. It was easy enough to take the lumps off with a round file, but after messing around with abrasive paper to smooth it out, I bit the bullet and got a soft wheel for my angle grinder (a Norton Rapid Blend fine / medium refining disk ). Not cheap, but it worked very, very well. Didn't clog on the (very) soft ally and didn't gouge or dig in either.
You'll notice that the lugs have gone - I went off the idea of riveting to the casing, and didn't want to use nuts and bolts through it. Instead, I made a doubler out of 0.5mm stainless sheet with some nuts welded to it that, in turn, could be spot welded to the casing and used to hold the engine onto the stand.
The first time I tried to make it, I welded the nuts on before bending the sheet - it went all shapes! It was a lot better bending the sheet first, but it still needed a few taps to straighten it out again afterwards. (I clamped a curved piece of copper under the nuts when welding them on.)
I eventually got it laying reasonably well against the casing, and, as far as I can tell, square.
Spot welded in place and buffed up.
I'd hoped to anodise the stand and leave it natural colour - it was a bit of an experiment as to how the welds would look compared to the sheet. I checked it straight out of the anodising bath and wasn't really happy with it - There is a little bit of difference between the welds and the sheet, but again there are mottled and grey areas (most obvious on the flat area bottom right). I don't know why this seems to happen with the 1050 grade
(maybe I need to try a de-smutting bath, but I don't see why pure Al should need that ?)So, as before, I decided to give it a little colour to disguise the unevenness. I thought a neutral grey colour would be best, so thought I'd try my black dye cold (I've only ever used the black dye hot before to get a solid black). After two minutes it took on a great 'gunmetal grey' colour that I thought would be perfect. Colours normally bleed out a little during sealing, and I didn't want this any paler so gave it another couple of minutes.
To my disappointment, it didn't really bleed at all, and after sealing it came out very dark. Not an unattractive colour, but not what I was aiming for - there's a sort of blue-ish tinge to it in some lights.
Cosmetics aside, I'm sure it'll be OK.
It fits where it touches
Overall, happy with that.
It's also the last piece in the jigsaw - Meccano time next:
Last edited:
My Old Landy
Engineering Mayhem
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Wow, just wow!!
Misterg
Member
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Thank you *very* much - I don’t think I’ve got much of either, but if I get an idea in my head, I’ve got to get it out!
Dr.Al
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I can't imagine there's anyone who's mind isn't blown by this thread.This is just awesome...the skill of some of you lads has me reading with my jaw dropped
Absolutely stunning.
Misterg
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Thank you! That mans a lot from someone who has built one of these. The artwork is woth nothing unless it runs though
We’ll find out soon!
Misterg
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I took advantage of the break in the weather yesterday to take it outside and set fire to it.
(If you don't want to watch the video, keep reading below)
It runs!
I was absolutely made-up. It started up pretty much straight away (no doubt helped by me leaving the gas canister on its side, so there was an 'ample sufficiency' of gas for starting. I'm just using propane at the moment to see if it will actually work - for it to develop any real power, it'll need to go on to liquid fuel (kerosene, etc.).
I was stunned by how smoothly it runs - I balanced the turbine & shaft assembly using the 'rocking' method to start with (the shaft and turbine on its bearings are placed in a loose fitting tube which is then rocked gently from side to side and see where the heavy spot settles, then grind a bit off). I'd got as far as I could with that, and thought I was done, but then I tried the method mentioned by @kappi above where you hold the rear bearing in your fingers and spin the shaft/turbine up with compressed air to feel for vibrations -you then add a small piece of tape to the turbine and see if it makes things better or worse. I found the second method more sensitive - I was surprised! What I noticed was the *absence* of vibration when things were right, rather than the vibration itself (if that makes any sense!).
There are issues with the oil supply in the video (in the first test, I think the connection on the casing for the oil jar was leaking, even before it fell off!) but this oil supply is only a temporary arrangement for running on gas - it will be fed by a bleed off the main fuel line when on liquid fuel.
I'm waiting on a few bits for the kerosene supply, but I can't wait to get it set up!
Thanks to everyone for the very kind comments and encouragement through this thread, and thanks for reading
I'll be back...
...with kero!
(If you don't want to watch the video, keep reading below)
It runs!
I was absolutely made-up. It started up pretty much straight away (no doubt helped by me leaving the gas canister on its side, so there was an 'ample sufficiency' of gas for starting. I'm just using propane at the moment to see if it will actually work - for it to develop any real power, it'll need to go on to liquid fuel (kerosene, etc.).
I was stunned by how smoothly it runs - I balanced the turbine & shaft assembly using the 'rocking' method to start with (the shaft and turbine on its bearings are placed in a loose fitting tube which is then rocked gently from side to side and see where the heavy spot settles, then grind a bit off). I'd got as far as I could with that, and thought I was done, but then I tried the method mentioned by @kappi above where you hold the rear bearing in your fingers and spin the shaft/turbine up with compressed air to feel for vibrations -you then add a small piece of tape to the turbine and see if it makes things better or worse. I found the second method more sensitive - I was surprised! What I noticed was the *absence* of vibration when things were right, rather than the vibration itself (if that makes any sense!).
There are issues with the oil supply in the video (in the first test, I think the connection on the casing for the oil jar was leaking, even before it fell off!) but this oil supply is only a temporary arrangement for running on gas - it will be fed by a bleed off the main fuel line when on liquid fuel.
I'm waiting on a few bits for the kerosene supply, but I can't wait to get it set up!
Thanks to everyone for the very kind comments and encouragement through this thread, and thanks for reading
I'll be back...
...with kero!
Last edited:
Prajna
Fixing things for the love of it
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I took advantage of the break in the weather yesterday to take it outside and set fire to it.
(If you don't want to watch the video, keep reading below)
It runs!
I was absolutely made-up. It started up pretty much straight away (no doubt helped by me leaving the gas canister on its side, so there was an 'ample sufficiency' of gas for starting. I'm just using propane at the moment to see if it will actually work - for it to develop any real power, it'll need to go on to liquid fuel (kerosene, etc.).
I was stunned by how smoothly it runs - I balanced the turbine & shaft assembly using the 'rocking' method to start with (the shaft and turbine on its bearings are placed in a loose fitting tube which is then rocked gently from side to side and see where the heavy spot settles, then grind a bit off). I'd got as far as I could with that, and thought I was done, but then I tried the method mentioned by @kappi above where you hold the rear bearing in your fingers and spin the shaft/turbine up with compressed air to feel for vibrations -you then add a small piece of tape to the turbine and see if it makes things better or worse. I found the second method more sensitive - I was surprised! What I noticed was the *absence* of vibration when things were right, rather than the vibration itself (if that makes any sense!).
There are issues with the oil supply in the video (in the first test, I think the connection on the casing for the oil jar was leaking, even before it fell off!) but this oil supply is only a temporary arrangement for running on gas - it will be fed by a bleed off the main fuel line when on liquid fuel.
I'm waiting on a few bits for the kerosene supply, but I can't wait to get it set up!
Thanks to everyone for the very kind comments and encouragement through this thread, and thanks for reading
I'll be back...
...with kero!
Just stunning and gorgeous, Andy. Looking forward to the kero.
