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Post by Johansson on Apr 10, 2016 0:45:35 GMT -5
Looking good Jeff!
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Post by jetjeff on Apr 12, 2016 2:38:19 GMT -5
Thanks!! Here are some pics of the compressor diffuser. I milled notches in each blade to interlock with the inner disk. A small lip was left on the disk, enabling just a small tack weld to firmly anchor each blade. Every other blade is shorter, in an attempt to prevent surging. Jeff
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Post by jetjeff on Apr 12, 2016 23:54:27 GMT -5
The turbine blades were twisted to 37 degrees last night. The turbine is 347 stainless .125" thick. Jeff
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Post by jetjeff on Apr 15, 2016 2:49:28 GMT -5
I made an angle template from thin aluminum sheet to check the angle of the blades, some were off so I had to tweak them. All blades are pretty close now, runs true when spun on the lathe. Next is profiling them, uggh my favorite job,,,lol. Jeff
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Post by jetjeff on Apr 18, 2016 3:32:16 GMT -5
More progress was made. I was able to mill the 3 cooling ducts and drill the 3 attachment holes in the diffuser. The inner ring will be milled off, once I'm sure I don't need to chuck it in the lathe. Since, if the turbine works, it will be used for flight (too big to fit inside any model, I could envision it on top of a delta), I'm making every effort to shave weight as much as possible. Jeff
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Post by jetjeff on Apr 22, 2016 0:33:21 GMT -5
The almost finished NGV assembly was checked for concentricity. I'm about .009" off in spots. Welding distorts the stainless more than you think. I'll have to make a mandrel, sized for the shaft tunnel hole and true it up some on the lathe. The outer mounting ring will need to be bent forward slightly, as the top of the mini keg has a bevel to it. Jeff
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Post by jetjeff on Apr 24, 2016 0:53:19 GMT -5
The front cover was machined, from black Delrin. I indexed the head of my Bridgeport to 25 degrees to provide clearance for the compressor. I'll have to spin an aluminum trumpet to complete it. Jeff
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Post by jetjeff on Apr 28, 2016 23:16:36 GMT -5
Well,,,after about two dozen failed attempts, I'm pretty confident I won't be leading any adult ed classes on how to spin aluminum, lol. They make it look so easy in the YouTube videos. The one piece that did come out respectable, wasn't completely against the wooden former I made, I'll just machine the trumpet from solid. Jeff
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Post by Johansson on May 1, 2016 1:22:37 GMT -5
Spinning metal is an art form, those who master it make it look really easy but I assume they have a big pile of scrap pieces behind the workshop.
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Post by jetjeff on May 1, 2016 1:53:35 GMT -5
Hi Anders LOL,,,I think the trick with spinning aluminum is you have to use soft grades or anneal it to get it soft. I started profiling the turbine blades, currently 1/16" at the top of the airfoil and 1/32" at the exit, still might be too thick. My inherited Dumore grinder decided to give up the ghost (why do your tools fail just when you need them most??), so I made a trip to Production Tool to buy a new one. 764.00 dollars lighter (ouch!!), the new one is 1/4 h.p. vs 1/10 h.p. for the older unit. I did make a jig to use the hand grinder as a tool post grinder, light duty, but it does work. Sorry, I can't get a real decent picture of the profiled turbine blades. Jeff
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Post by Johansson on May 1, 2016 5:05:16 GMT -5
Yup, multiple annealing passes is a must when spinning aluminum.
I seem to remember that in one of the GTBA newsletters there is a description of a very clever jig for grinding turbine blades, the guy used a miniature belt sander belt and made a jig for his lathe with a small motor and a belt pulley of the same diameter he wanted the turbine blade curve to be.
He simply ground the untwisted blades to shape by pushing the pulley (with belt on it of course) against the blade, twisted them and had only some minor hand grinding to do before the turbine wheel was finished, much less work than hand grinding everything and you get identical radiuses on all of the blades.
Cheers! /Anders
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dieselguy86
Veteran Member
Joined: September 2014
Posts: 186
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Post by dieselguy86 on May 1, 2016 6:01:03 GMT -5
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Post by jetjeff on May 4, 2016 22:35:04 GMT -5
I've finished the compressor, just need to epoxy in the hub. Started work on the shaft tunnel. It's starting to look like a turbine, especially if you drink enough Heineken,,LOL. Jeff
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Post by Johansson on May 5, 2016 0:00:53 GMT -5
Not really, but that is a very clever way of doing it since you can have any profile on the "spoon". Nice work on the compressor Jeff!
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Post by jetjeff on May 9, 2016 2:26:29 GMT -5
Hi all, The shaft tunnel was finished over the weekend. Next comes the shaft and burner can. I also made a gasket for the NGV to outer case surface, something that isn't mentioned in the Kamps book. Jeff
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