reedy
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Post by reedy on Feb 23, 2022 13:22:35 GMT -5
www.youtube.com/shorts/7V1Uj-fjcIII don't know the guy he has a Jm50 running on YouTube he has a couple of other videos with it running ,combustor is no good and diffusor worse. this engine comes with cast NGV Turbine wheel and cast car compressor.
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reedy
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Post by reedy on Feb 20, 2018 10:19:59 GMT -5
Hi Jeff Glad to hear your well again. I got off my Arse and got my KJ66 going again on the test stand made about 3.1kg at 0.8 bar at 300c check it out on my YouTube channel reedy93. Not easy filming and running an engine had to keep resetting the scales every time they froze.
Regards Chris
P.s also been working on electric starter using a trigger(£2.50 off eBay from china) for a 24v electric drill so i can start it slow.
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reedy
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Post by reedy on Jan 25, 2018 9:04:53 GMT -5
Hi Jeff
Excellent work as usual,you said you are basically copying the x2 engine just that you have deviated slightly and it has caused problems,if you look at your combustor and his the inner cone is more tapered on his as per the book then he has added finger flaps on the NGV to seal the cone at the back.
Looks like you opened the cone (less of a taper) to fit the kamps style NGV that does only make it tighter at the front but not by much but it is already very tight.
X2 engine build thread say's he reduced the size of the big main holes and also some of the smaller holes at the very front to offset the extra air from the u tubes.
On a lot of combustors the orientation of the inner and outer raps must be so and the stick straight or u shaped must align/avoid holes.
The 8 sticks cause problems as they align /block some of the 10 large holes,you can see in the middle picture of three (jan 21)
If you could have put 10 shorter u sticks and 10 holes as per x2 jet engine and aligned the cross over v shape in the sticks to the 10 holes . 10 Straight sticks from the back would have been my option or the updated design PT35 combustor design.
Kurt fitted 3 u sticks to the original combustor just to try them knowing it was not enough he then redesigned the combustor with a straight inner and outer at 95mm and six u sticks at the front this is the first combustor I made to fit the fd3/64 but later fitted the hobbyjets 631/ PT35 combustor which was better.
Kurt did not put any holes in the outer combuster (99mm dia) but found out at one of the GTBA meetings ( think it was Mick Murphy wren turbines or Mark Drake 631 hobbyjets) that you need a certain distance between the outer combuster and the casing or the air is restricted and does it go through the holes,Kurt mentions this in his book on the TK50 made from a thermos flask he used the inner part to make the outer combustor gave him the right air gap.
Basically the outer combustor 99mm dia on the FD3/64 is too big a diameter to have holes that would work.
Hey-ho, it is what it is now, suck it and see at least you are moving forward with the build not sat on your arse typing these words of wisdom /tripe ( delete whichever you think is appropriate] the combustor can easily be modded or replaced later when you have the engine running.
ATB Chris.
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reedy
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Post by reedy on Jan 21, 2018 8:14:33 GMT -5
Hi Jeff I agree with John about the metal thickness 0.016 (I used 20 thou 304 spot welded)is getting too thin unless you have gone with something more heat resistant than stainless,only saving grace is the burn in the FD3 is not as intense as a KJ. I try not to fully weld up a combustor until I am happy with it,I weld the inner to the front combustor and the outer to the back then use 0.020 stainless welding wire and wire it together at the front outer corner drilling 1mm holes in about 4 to 6 places. The 10 large holes near the front are going to blow deep into the flame and with 8 sticks will cause uneven stick temp on some sticks unless your sticks don't go in that far ? My standard size FD3 used 8 sticks. I tried changing the flaps to 6mm holes, seemed to work better,I would not do louvers as it needs to stop the flame coming out louvers will make the cooling air more of a skin cooling . Link to kingtech k-80 F sticks lot of work and welding, good design medium size holes on outer can to blow across ends of sticks ,can't find a picture of inner hole pattern. No skin cooling holes on outer can at the back in fact not many small holes on outer can. shulmanaviation.com/product_info.php?cPath=56_73&products_id=2571Chris
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reedy
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Post by reedy on Jan 16, 2018 7:12:52 GMT -5
Pictures of GT2000 and detail about Brazed inner NGV,he say's just temporary to be able to M/c outside NGV blades to dia not sure if he welded outside or just left it. Pictures of my spun KJ66 burner can end in my hand / fd3/64 alloy front spun / fly pressed outer NGV area for FD3/64 out of stainless tube/ spare combustor for KJ66 / /inner combustor for FD3/64/ and a front combustor pressing for FD3/64 done under a very high pressure press. Sorry for mucking you build thread up can't send pictures on private messaging.
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reedy
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Post by reedy on Jan 15, 2018 19:03:49 GMT -5
Hi Jeff I used easyflow number 2 (25% cadmium not safe)which melts at 608 - 6012 easy to do with normal butane blowtorch,I used 1/32 silver solder wire and when soldering the stainless needles into brass tube I set up with making small rings of the silver solder which i placed on the needles then fluxed around the joint before applying any heat. I applied the flame only to the brass tube either side of the needle if you heat the needle it overheats and goes black and will not solder. It say's 660-740c for the sil 45 still not hot enough for a NGV. Hi Ron I had to do same twin - touch and a hearth set up made of fire bricks from a electric storage heater when soldering copper boilers for model boats. I've gone from the steam age to the jet age! seen people use tig for Brazing. www.youtube.com/watch?v=wf-Cq5eQmt0what I know about Brazing you can write on the back of a stamp,just made it work for me but you quickly need a lot of heat with bigger jobs or higher temp braze. Chris
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reedy
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Post by reedy on Jan 13, 2018 4:28:45 GMT -5
Hi Jeff
The stainless pressing look good no need for spinning if you can press them .
It's worth thinking about using tubes from the back,I did not do it as it was like the original design ,no back to the combustor just pushed against the outer can with 3 springs.
Straight sticks from the back mean no fuel pooling in the sticks and hotter air entering the sticks to help vaporization when starting.
There are 10 large holes in the inner combustor, tube would be better to have ten sticks between the holes to avoid cooling of the sticks.
Don't know how many flaps on the outer combustor but that would be better at 10, reduce the size/area to match the area if you have less.
On one of the talks at the GTBA meeting by Kurt he said he did the flaps to swirl the flow and make some way of varying the flow if needed but found the gas flow just went straight out as it's in a rush to get out. I could see on mine it did not swirl,the flaps on original size where open 2.50mm this works out to 6mm dia hole which i did on later ones and tested it by cutting the flaps off and spot welding plates over the square hole with 6mm hole in ,it's a lot quicker drilling than doing the flaps and never liked them always felt the could vibrate, fracture and fall off into the turbine.
Again 10 sticks would be better, my normal size FD3 engine uses 8 sticks.
Just food for thought.(think I am repeating myself with some info)
Chris
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reedy
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Post by reedy on Jan 12, 2018 17:19:53 GMT -5
Hi Jeff
Your stainless pressings and NGV look good,are you doing straight sticks from the back or hockey sticks at the front. How many sticks did you do on the mark 1 .
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reedy
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Post by reedy on Jan 5, 2018 19:47:35 GMT -5
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reedy
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Post by reedy on Jan 5, 2018 6:14:07 GMT -5
Hi Shannon, I've never seen a spring putting pressure on the outer race of the front bearing, only the rear. I have seen plans where a wave washer is used on the front bearing to apply bearing preload. Are your plans correct? Nice work so far. Regards Jeff Yes I do intend to have the preload spring pushing the front bearing, There isn't really any difference in the force between using a spring or a wave washer, Although it is somewhat easier to fit a spring in between the shaft and housing. Wave washer tend to be a smaller inner diameter and often there isn't space. The AMT Olympus uses what looks like a pair of conical washers at the front but the shaft has to be turned down just behind the bearing to fit them in. With the spring I can also have the sliding bush in front of it to keep the bearing (hopefully) square to the housing. There are pro's and con's as to whether the preload pushes forward or back, what they are I can't remember off the top of my head . Part of my reasoning for having it forwards is that the front runs cooler and is less likely to overheat the oil in that area, hopefully making it less likely for things to get gummed up and stick. I was considering using O-rings for bearing damping, but apparently they can also get sticky, with the consequence that the preload goes away. I am sure you can imagine what happens next.... There was an interesting discussion I was reading about how the air pressure on the backside of the compressor wheel helps offset the combustion exhaust pressure against the turbine blades and balances out the fore and aft forces on the bearings somewhat. Shannon. Hi Shannon There was a lot of talk,problems early on in the GTBA with lube to front bearing and which way to preload ,it's not an easy problem to fix or calculate people ended up making setups then they could preload at either end and see which worked. If you do have front bearing failures make sure the compressor wheel is balanced at both ends before being balanced as a whole you can get whirling problems unseating the front bearing. The compressor wheel can create a low pressure area on the backside of the wheel,some of the fix's to the KJ66 where to drill a hole in the diffuser to pressurize the area behind the wheel and fit the oil supply needle to the front of the front bearing and have the front bearing area open Tried to post pictures of Kurt Schreckling design of his TK50 which is front preloaded with a spring the engine is designed for max fuel efficiency using 50mm o/d wheels and a large outer can of 98mm o/d to increase efficiency. All to reduce his wing loading of his models as he felt the power and fuel weight was too much of the KJ66 . Not sure of you combustor design tin can shape seems to dominate as it works and easiest to do and you can spot weld the flanged fuel sticks on the rear wall,with the angle you show it will need to be tig welded,for thin sheet spot welding is better with less distortion. do not use silver solder on the combustor only welding is good enough. with your first engine leave the front cover inlet parallel on the outside for re chucking and as i said try to design the bearing tube with sleeves front and back.make your wedges 1mm higher(see G Rutten build thread) than the outflow of the compressor as it seems to help and can give you the option of a higher tip wheel .make the inlet piece separate it makes it easier to get the clearance correct. Trying to be constructive as time spent designing can save a lot of scrap as a caveat I have never designed a engine from scratch, question and read up on anything I say . If the pictures do not come through will try to re post. Chris
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reedy
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Post by reedy on Dec 30, 2017 6:26:29 GMT -5
Hi Shannon I worked in the aerospace industry now retired our firm made the typhoon, the canards are made of titanium which was hot bonded and superplastic formed the tools were heated to orange colour about 650 to 700c wikipedia say's 900c for the titanium superplastic forming, I was not involved with the process but the tools took a lot of damage developing cracks and impressions where it crushed the titanium to hold it round the edges as it was blown to shape. Titanium is good but at 650 to 700c exhaust temp I would not use it. www.baesystems.com/en/feature/even-pilots-think-superplastic-is-fantastic#Chris
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reedy
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Post by reedy on Dec 30, 2017 5:02:52 GMT -5
Hi Shannon
I've been quiet all summer,mainly stuck to commenting on Jeff's heineken build,just want to comment on a safety concern,try to stick to the normal metals, aluminium alloy steel and stainless, the titanium nut on the turbine end is a bad idea as we were warned off it in the GTBA. It can break down with heat and on the hot side of the turbine it will get no cooling. I tended to use the same material as the shaft, a 12.9 cap head bolt or 316 stainless which you can buy in hexagonal section. Stay away from hollow shafts you will get balance problems no small production engine does it as far as I know. The best way of reducing weight is to stay as small and short as you can on the engine and push the revs and case pressure up as per production engines but this does require a professionally produced cast turbine wheel and a good designed combuster. On the bearing tube material wren power systems went to stainless for stability but aluminium alloy does work.
Chris.
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reedy
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Post by reedy on Apr 25, 2017 13:20:50 GMT -5
Hi Jeff Sorry was speed reading 5 thou is too much but still worth trying to balance it, another learning curve. May be try the heat shrink method,make sure to turn the end features all in one go using left and right hand lathe tools.
Chris
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reedy
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Post by reedy on Apr 24, 2017 5:27:42 GMT -5
Hi Jeff Read the PT35 construction manual page 6 on making hollow shafts you will not build one perfect ,there will always be some vibration,have a go at balancing it using the method in the manual and blue tac,only grind away when you are sure your balancing method is working and then only at each end of the shaft. I was a toolmaker for 40 years and never got anything perfect, you need to give yourself a tolerance.
leave perfection for people that never finish anything.
Chris
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reedy
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Post by reedy on Apr 22, 2017 14:59:13 GMT -5
Hi Jeff youtube vid on coatings and gluing by Dan Gelbart. worth watching the whole series. www.youtube.com/watch?v=x7onZGqrYyYChris PS corrected temp on last post mixed up in F-C
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