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Old Mar 12, 2006, 10:07 PM
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Columbus, Indiana
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It's not that hard Dalbert...If you have some machining knowledge and plenty of time you can do it. I've seen some amazing stuff come off a sherline. I go to model engineering shows and they are everywhere. They may be small, but you would be surprised what can be done on one. Also the largest part you'd probably be turning would be the front end and that should end up (depending on the compressor size) aroud 4-5 inches. That should be no problem for a sherline. Later...
Martin
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Old Mar 17, 2006, 01:23 AM
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Columbus, Indiana
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Here's some video

Hopefully this will work. This is my first try at posting a vid...


http://media.putfile.com/turbin

Later...
Martin

CAUTION>>>>>>I tried to view this video on 6-2-09 it goes to a video site and tries to download some malware crap...


PM me if you want to see the video.
Thanks,
Martin
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Old Mar 17, 2006, 09:15 AM
K4UAV
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Miami, FL
Joined Jul 2003
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Thanks Martin. Great video! One question, where/how do you learn to maching the compressor blades? I am just not smart enough to figure out how to make those compound curves. Any pics or notes on the setup?
Thanks again,
-dave
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Old Mar 17, 2006, 08:16 PM
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The actual compressor is just like what all the production turbines use. They are what comes out of a small turbo charger. If you look at the sixth and seventh pics in my first pic post you will see the compressor along with the compressor diffuser. Mine came out of a Audi I think. If you're talking about machining the compressor diffuser that is pretty easy to do. **Overly simplistic instructions** Turn a blank, slot on bandsaw to radii needed, form small fins that fit tightly into slots, weld the back side. Turn fins to match profile of front end housing and height of compressor edge plus some clearance (about .015") behind compressor. Hole in middle to clear shaft and bearing fit to backside. Easy right... Actually if you saw the piece you'd know a lot more of what I was talking about. It's hard to tell in words.
Don't despair, they aren't as hard as people tell you they are. By the way, the people who tell you they are hard to make haven't made one.

I forgot to say about the video, it's only running at an idle of about 40,000rpm. Canister pressure of three psi. I tried to show the rear end while it was running, but since it's daylight you can't see the blue inside the combustion chamber. I'll put some more soon of it running up to speed.
As always keep the questions rolling
Later...
Martin
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Old Mar 17, 2006, 09:52 PM
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Hmm, maybe I am pole vaulting over mole hills, but these are the parts I am most confused about. I'd love to see more videos/pics, whatever you got!
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Old Mar 17, 2006, 10:52 PM
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Columbus, Indiana
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Aha,

The top pic is the compressor, use it just like it is. It should be dual plane balanced and ready to go. The middle pic is the turbine wheel, you have to bore the center out to fit the shaft diameter and possibly fuzzcut the outer diameter of the fins to fit the NGV (bottom pic). DON'T FORGET TO BALANCE THE TURBINE WHEEL!!! I can show you my balancer and it worked very well. Are these pics of your own castings you are going to use or just pics of the parts from another source? If you are using these, you just saved a lot of work fo yourself... I made my own turbine wheel and NGV. Both are fairly easy, but I wouldn't tell anyone to make their own turbine wheel. I did make my own turbine wheel (twice actually) and they are actually a lot easier than you think. The NGV is more work but I can tell you how if you need machining/setup details. I can try to get some more pics soon, I need to disassemble and show you all the parts up close.
Later...

Martin
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Old Mar 19, 2006, 07:25 PM
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Got any pictures or discription of your milling setup? How you made the NGV and the diffuser specifically?
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Old Mar 19, 2006, 10:59 PM
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Ecoliburger,

The rear end NGV is actually two pieces. Well, two pieces plus the vanes. First you make the innner ring which attaches to bearing tube. Careful if you make the bearing tube from aluminum and NGV from stainless. The aluminum will swell with heat if the fit is too tight and will cause damage upon disassembly. Anyway, the inner ring was first turned on a lathe to what I wanted and then put in a rotary table set up vertically on a mill. I then used a hole saw (bi-metal) in a tool holder I made to cut the radial slots for the vanes. THis step takes some experimentation to get the correct angle. Once you find the correct place to cut the radial grooves, cut one then rotate the rotary table for however many vanes you plan on using. The easiest way to form the vanes is to use tubing that is the same size as the hole saw you used to cut the grooves. Cut the vanes out of the tubing on a bandsaw or cut them out with a die grinder. Careful you don't lose the radius of the tubing. Once you have all vanes cut out and de-burred you can weld them into the center piece. Preferably use a tig welder, you really need to control the weld here. After that, chuck the center piece again into the lathe with the vanes out and cut them to match the outer piece. I actually put a little step on the end of the vanes on the OD to fit into slots in the outer piece. **You have to cut the matching slots in the outer piece by hand to fit the center piece with vanes. If you only weld three vanes to the outer housing you should be good. Don't weld all of them as this piece needs to move around with the heat and if it's held by all vanes being welded you risk cracking something. Hopefully you can picture what I did. If not I can take some pics. Here is a sad sad drawing (done by hand) of a cross section of the back end. I'll have to see if I still have my prints laying around and could post them. They may shed some light on this a little more..


The front end diffuser is pretty easy, first turn the backplate center hole to clear shaft, bearing tube fit on back, front side center must be undercut to clear back side of compressor. Take that piece and saw radial grooves ( you can see them well in the third pic on post #6). Then get some aluminum and cut out the vanes oversized, they must be radiused to match slots. I used a slip roll to form mine. Then insert them in the slots and tack weld the back side. Again with tig welder. The next step is tricky. You must turn a blank to fit the bearing tube location diameter on the back side of the diffuser. Don't take it out of the lathe. I used a very low melting pt (~150 degrees F.) bismuth alloy. You can get it at plumbing stores, Mc-master carr, MSC etc. Beware it is not cheap. anyway, melt that and pour it around the vanes so you have a solid block. Then put some foil down on the lathe to catch that stuff, again it's expensive. Turn the OD of the fins to fit both the front end and the canister. You need to match the radius on the back of the front housing to the top of the fins. Then remove from lathe and melt the alloy out. Voila you have a diffuser. Then you need to put some holes in there for the bearing tube to bolt to, and for the front end to bolt to. Again check pic three on post 6. Sounds very easy right....Actually it is a lot easier to do if you could see the part in your hand. It sounds discouraging, but it's not that hard. You could do the diffuser like the one that's on the big turbine on pic 4 post 9. That's a little bit different setup but I can tell you about that if you want. Either way will work. The one in the big turbine needs a lot more machining skill to be done correctly. All the holes you see go through to the front end and three of them are pins that locate the diffuser to the front end. Anyway, if you want I can detail that setup...
Man my fingers are tired....
Hope this helps.
Later...
Martin
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Old Mar 19, 2006, 11:13 PM
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Oops I forgot to attach my crappy pic.
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Old Mar 22, 2006, 06:45 PM
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what do you use for FADEC or ecu? What did you use for figuring out sizing of the turbine wheel, etc? Did you take measurements from some other turbine or did you do your own calcs?
Thanks
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Old Mar 23, 2006, 03:21 PM
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Ecoli,
I don't use a fadec , I Know what canister pressure I get for a given throttle stick movement, so I just run the fuel pump off a small brushed esc. I know this isn't what the production guys would recommend, but I know that at full throttle my turbine will run all day long as it's not running near the edge. If you check the bearings often and do plenty of bench running you can get by without the rpm and egt sensors. Also, you have to start by hand, I know that's almost unheard of anymore. That's not to say I wouldn't have one if I could...just a matter of money. Just know you can run reliably and fly just fine without a $400 ECU.
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Old Mar 27, 2006, 09:02 PM
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Thanks for the info. Do you have a web site or more pics somewhere?
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Old Mar 27, 2006, 11:30 PM
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Sorry Ecoli,
I don't have a website, but I can take any pics you want to see. Let me know...
Later...
Martin
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Old Mar 29, 2006, 12:07 AM
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What did you use for the outer case?
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Old Mar 29, 2006, 04:07 PM
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Thats what I'm having trouble with at the moment.
I totally screwed up b/c it is way better to build around the compressor once you have it.
So I have to trash this case and start over.
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