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Post by jetjeff on Jul 19, 2016 2:24:53 GMT -5
Hi Mark,
I'm going to look at the engine today, after talking it over with the boss (wife),,,lol. The owner is out of the country, but did text me that the engine has an unknown number of starts. I'm not familiar withe the hydraulic start feature. I have some info on this engine including a cut away drawing of it, but to be honest, I wouldn't know if it's missing parts or not. Is this engine still supported by Garret?, I mean can you still get parts for it?
Thanks
Jeff
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Post by pitciblackscotland on Jul 19, 2016 3:42:02 GMT -5
Hi Jeff, Ok get some photos as well, what are your plans for this turbine? I can sell you a copy of the JFS manual if you need it? with the hydraulic start feature you would need a high pressure pump plus hydraulic oil tank,ect,ect. Better to get a 18 L scuba air tank and set it up like i did. As for parts it will come down to what you need Tim Arfon may still have some parts www.akronturbinegroup.com/arfons.php Also Avon Aero Supply Inc may have parts CALL BRUCE AT 317-727-5874 Also make sure it has a air impingement port. Cheers, Mark.
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Post by jetjeff on Jul 19, 2016 12:38:09 GMT -5
Hi Mark, I just got home from looking at the JFS-100-13A. The lowest the seller will go is 2,000.00. There doesn't appear to be an air impingement port. There also seems to be a very slight flaw in one of the compressor blades, not sure if you can see it in the pic. The turbine looks OK, but I'd like to see how the NGV's look. I've sort of ruled out buying this engine, it would be one thing if it were a running engine, but this engine is definitely a project. Seems like it would turn out to be a money pit. The compressor blade in question is in roughly the 4 o'clock position. I've also read online, that if you convert this engine to a thrust engine, you must install an oil cooler. This engine didn't shows signs of any oil cooler. Jeff
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Post by pitciblackscotland on Jul 19, 2016 20:28:41 GMT -5
Hi Jeff, Thanks for the pics. Mmmm no air impingement port,yeah I can see the slight flaw on the compressor blade that would be good if you can remove the exhaust cone and then the NGV there are 8 cap screws holding it in place then you can inspect the turbine wheel. There must be a air impingement port as the units with eclectic start have them for back up. If you are looking for a running JFS turbine it will cost you $4,000 plus, the one i got from Tim Arfon cost me $4.500 USD it was complete with low starts and the free power gerbox, The second JFS was $1,100 USD with out free power gearbox but that was missing a lot of parts all comes down to how much you want to spend,as you know owning a turbine is a expensive hobby. I had conversations with Dino from www.turbokart.com about the oil cooling system you will need to spend a bit of money on the right oil pump and oil cooler and fan. He told he ran the kart for a hour no problems that was with the thrust version and free power unit. Cheers, Mark.
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Post by jetjeff on Jul 30, 2016 12:13:37 GMT -5
Hi All, Back at turbine building after a short camping trip. I had to machine some tooling to bend the flange on the NGV to match the bevel on the Heineken mini keg (the 1/4" thick ring about a 1/2" wide was used to hold the tolerance of the turbine shroud during the bending process). I will use a BBQ ignitor for ignition. I had to remake the metal piece that holds the ceramic ignitor as it wasn't made out of stainless. Side note: That JFS 100-13a is still for sale on Craigslist, I'm tempted to offer him 1,500.00 for it. Jeff
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Post by jetjeff on Aug 7, 2016 13:05:38 GMT -5
Hi All, I pop riveted the engine mounts to the mini keg using 3 (for each mount) 5/32" S.S. pop rivets. The NGV was also pop riveted using 1/8" S.S. rivets. I can now accurately locate the holes for the main fuel manifold, the starter gas injector and pressure ports for measuring case pressure and a port for pressurizing the oil reservoir. I've also been working on a decent test stand, it's the main reason for me not trying to run the previous engine I made. Jeff
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Post by racket on Aug 7, 2016 22:58:24 GMT -5
Hi Jeff
Thats looking really nice :-)
Cheers John
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Post by jetjeff on Aug 8, 2016 0:56:47 GMT -5
Hi John,
Thanks. Shouldn't be too much longer before I have two engines to test.
Jeff
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Post by jetjeff on Aug 10, 2016 3:21:28 GMT -5
Hi All, Here is a pic of inside the engine showing the backup washers used with the pop rivets. Larger fender type washers were used for the engine mounts and smaller ones for the N.G.V. Jeff
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Post by jetjeff on Aug 10, 2016 17:50:53 GMT -5
Hi All, I installed the starting gas injector. It's 1/8" stainless steel tubing, kinda big, but a bigger engine needs more propane than a standard sized Schreckling engine. Jeff
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Post by jetjeff on Aug 14, 2016 15:46:12 GMT -5
Hi All, I didn't get as much done on the turbine as I had hoped this weekend. I did press the rear bearing on the shaft. The interferance fit was about .0014". I put the shaft in the freezer for several hours and heated up the bearing. I pressed it on with my Bridgeport. As soon as I press the front bearing on, I can balance the rotor. Jeff
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gtbph
Veteran Member
Joined: August 2013
Posts: 101
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Post by gtbph on Aug 18, 2016 18:02:30 GMT -5
Hi Jeff, I'm not sure because I've never built an engine, but from what I've read I believe it would be better to use a (tight) sliding fit for the bearings. Schrecklings book recommends this, and JetCat engines seem to use it too: www.youtube.com/watch?v=I3jE-PXV-68In the video you can see him push the bearing onto the shaft with his hands at 2:40. Cheers, Alain
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Post by jetjeff on Aug 19, 2016 0:41:53 GMT -5
Hi Alain,
Yeah,,,I've seen that video and thanks for posting the link. The assembly tech does push the front bearing on with little effort. In fact, he pushes the whole shaft into the engine with little effort. I kind of went by what Thomas Kamps suggested on page 76 of his book (3rd edition), "the ball-race at the compressor end should be a good press-fit in the bearing seating". The rear bearing must be a sliding fit as Schreckling recommends, but the shaft tunnel expands as it gets hot, so you probably don't want any axial play at that point. I'll heat the shaft tunnel with a propane torch to see how much it expands. The way I constructed my engine will allow for expansion of the shaft during the hot cycle, I'll explain further, later.
I wish I had the balancer shown in that video,,,lol.
Jeff
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Post by jetjeff on Aug 19, 2016 4:05:29 GMT -5
Hi Alain,
I checked the shaft tunnel cold, it is 1.249 (O.D.)", after heating with a propane torch it is 1.255". I machined the tunnel (at the rear bearing) to have a .003" (O.D.) interferance fit, so at operating temp there should be .002 - .003" clearance. If the clearance was a sliding hand press fit cold, you'd have .005" to .006" of axial play hot, too much IMO. You might say the NGV would keep the shaft tunnel from expanding that much, not 100% sure.
Bearing manufactures offer tons of data and formulas on calculating fit clearances,,,too much for my two brain cells for sure. Considering the tortuous environment turbine bearings operate in, it's surprising they last as long as they do.
Jeff
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gtbph
Veteran Member
Joined: August 2013
Posts: 101
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Post by gtbph on Aug 19, 2016 17:50:29 GMT -5
Hi Jeff, Me too, the manufacturers informations make me even more confused than I already am. When I made my shaft I simply followed Schrecklings advice without looking much further, because his concern that a press fit could lock the bearing in a slightly tilted position and/or deform the race convinced me. Then shortly after that you wrote the post about the press fit and I panicked a bit! I searched for more information and found contradicting advices: The bearing manufacturers say the fit should be tighter the more loaded the bearing is, but then I found the video, and wanted to post it to see what you think about it. What you say about the thermal expansion and the bearing tunnel design makes much sense to me, the only thing is maybe I would have used a sliding fit on the shaft/inner race. I think the outer race must be held more tightly because it has a "vibration" load in all directions, but the inner race has a point load in one direction, so it should not creep too much. On the other hand, I've not seen any "tilting or race deformation" concerns anywhere else than in Schreckligns book. Yes the JetCat guys have nice machines indeed, maybe we could visit them, if you take the balancer, I'll have the mill! Alain
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