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Post by racket on Feb 18, 2016 3:58:44 GMT -5
Hi Mark
Yep , All the others were fine to remove but as soon as I took the tension off that last screw the can slid backwards a tad and jammed onto the screw thread , it wasn't much of a move as theres very little clearance around the screw , the whole process turned out much better than expected, a bit nerve wracking doing that last weld as theres a lot of time and effort bound up in making the can to that point, and I didn't want to have to start all over again .
Cheers John
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Post by racket on Feb 18, 2016 4:04:54 GMT -5
Hi Anders
LOL, I just copied the idea from the Solar T62 engine which has a large V band clamp to hold its outer can in place and a slipjoint around the turb exhaust , it unloads all the internals from any axial forces from the air pressure as well as any axial expansionary changes due to the various temperatures of parts during operation , they can just "float" around and take up the position they need to.
Cheers John
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Post by madpatty on Feb 18, 2016 8:48:13 GMT -5
Hi Racket,
What about the leakages through that slip-joint when metal heats up and expands.
Doesnt that slip joint leaks air when the metal expands because we dont need much radial clearance for leakage.
But nice work there removing any axial force from all the internal components especially the hot NGVs.
Cheers.
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Post by smithy1 on Feb 18, 2016 15:26:55 GMT -5
Hi Racket, What about the leakages through that slip-joint when metal heats up and expands. Doesnt that slip joint leaks air when the metal expands because we dont need much radial clearance for leakage. But nice work there removing any axial force from all the internal components especially the hot NGVs. Cheers. With the metals being similar composition, they should expand and contract at quite similar rates...keeping the tolerances reasonably well....John has thought of everything required.....we're not talking about any Joe Bloggs here...we're talking about a very clever man..! Smithy.
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Post by racket on Feb 18, 2016 16:03:41 GMT -5
Hi Patty
The inner wall in slipjoints is always designed as the hottest wall, this way the clearance is taken up .
The NGV stub in my application will always run hotter than the outer can that is only exposed to T2 temps .
Lets do the maths .............the slip joint is 140 mm - 5.5" dia, with 0.1 mm - 0.004" clearance , enough for easy assembly/dis-assembly
The NGV stub will have exhaust gases heating it , stainless steel has a "high" coefficient of expansion of ~0.00002 per degree centigrade , so lets assume the stub heats up to 400 C degrees during running, it'll expand ~1.1 mm - 0.044 " , suddenly our clearance has gone and the NGV stub is in contact with the outer slip joint wall in the concave rear wall , the heat from the NGV stub will begin to heat the other wall and it'll expand "away" from the stub until an equilibrium is achieved were there is virtually a sealed joint .
When cold , that 0.1mm diametric clearance represents a total area of ~22 sq mms , quite a substantial area , but the slipjoint is 20 mm wide representing a surface area of ~8,800 sq mms , air finds it hard to squeeze through with so much surface friction , there is some leakage at startup even with low P2s and a good layer of antisieze on both slip joint surfaces , but it soon stops once the NGV stub warms by 40 degrees C .......not long :-)
Cheers John
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Post by racket on Feb 21, 2016 1:06:23 GMT -5
Hi Guys Been spending a bit of time getting the sparkplug mounted in the engine , and a drain plug fitting for those wet starts . Plug boss ready to be silver soldered into the outer can wall , because the distance between can and flametube is a tad large for a conventional 18 mm long threaded plug I had to find something bigger and NGK make one with a 26.5 mm long 14 mm thread , its a LFR5A-11 . Plug fitting was silver soldered ( 45% silver content) on the can inside This left the can outside looking pretty clean, just a bit of "colour" After a bit of a polish up , it was time to check the plug still screwed in OK With that taken care of it was time to fit the drain fitting at the far back bottom of the can , fortunately I already had a stainless 1/4" BSP fitting , so after a bit of lathe work on it, it was ready to be silver soldered in place Then it was time to drill the hole in the flametube outer wall for the plug snout to recess into , so the flametube was assembled onto the engine and the whole lot fitted to the outer can and the hole position marked , then disassembled and the hole drilled to almost the right size before reassembling the engine again to check concentricity of the plug fitting and the flametube hole . They were a tad offset so the necessary corrections were scribed onto the flametube and the engine disassembled and the hole hand filed to the correct size . Engine reassembled and the plug screwed home nicely Time to clean up all the parts and do a trial assembly to see whats left to do Cheers John
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Post by racket on Feb 23, 2016 23:03:36 GMT -5
Hi Guys Before doing a trial assembly I decided to mount the engine on the test stand , much easier to do using just an empty outer can than a complete engine. Brackets made up from offcuts from machining the flametube end caps out of 2 mm stainless sheet LOL, now I can do the trial assembly Cheers John
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jettoymaker
Junior Member
Joined: September 2010
Posts: 55
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Post by jettoymaker on Feb 24, 2016 18:48:21 GMT -5
Hi John, Finally got into the site after a long time. Beautiful work as usual I see It will be interesting to see it fire up as there should be no doubt of that. You have had a perfect track record to date for the engines you set out to get running and after all the years you have been gathering data and experience, I can't see that it won't run. You have a natural affinity for these things and how they should behave as it is. The 10/98 and 9/94 have been reliable performers and with the tweaks that have been developed they will just go on and on. I've been pushing the 10/98 hard with B1 and have had little to no issues with the design you did. Pretty bloody good for a first original iteration! This current engine is a refinement of that so all good as far as I can see. I also feel after all these years and all that we have done together, that I can say on behalf of all the members on the site that you have given us purpose, entertainment, guidance, enlightenment and hope that we will succeed in our field of interest. In fact I seriously doubt that the home build jet/rocket field would be as far down that track without the handful of backyard geniuses that occupy and steer this site. I hope that this is not going to be your swan song engine and that your fertile and exceptional mind will take you and us to the next level of home spun power in a can. I seem to remember you and I discussing a high bypass engine at one point... Regards, Andrew
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Post by racket on Feb 24, 2016 23:46:12 GMT -5
Hi Andrew Good to see you back again High bypass engine ...............LOL, stop it , .............this has gotta be my last engine ............. Mmmm , but FM-1 is still without a purpose ...............maybe just an add on, not a complete engine . Yep , the 12/118 is getting close to being finished , I should have her fired up before Easter, if only this summer weather would hurry up and leave us , it'd be even sooner . Cheers John
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Post by smithy1 on Feb 25, 2016 17:50:28 GMT -5
Hi Andrew Good to see you back again High bypass engine ...............LOL, stop it , .............this has gotta be my last engine ............. Mmmm , but FM-1 is still without a purpose ...............maybe just an add on, not a complete engine . Yep , the 12/118 is getting close to being finished , I should have her fired up before Easter, if only this summer weather would hurry up and leave us , it'd be even sooner . Cheers John Summer ends next week John....you should have it done the following weekend!! You must be getting close to making some noise then..! I'm excited.. I've got another local-ish car show this weekend....I hope to take some video if I can remember to set the bloody camera up....I always forget then I smack my forehead afterwards.. Must be that old age thing catching up with me......now...where's my spoon..? Cheers, Smithy.
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Post by racket on Feb 25, 2016 18:01:02 GMT -5
Hi Smithy
LOL, beware , Senior's moments get more frequent ;-)
Yep , this morning I might start washing up parts and getting them dry in the sunshine , then do an "assembly" of the rotor into the shaft tunnel and NGV so that I can do an "insitu" weld on of the exducer shroud to V band flange.
Once thats done its only a case of making a couple of fitting for the TOT thermocouples and P4t pitot and I think thats about it as far as construction goes , I'll think about jet nozzles after she's fired up and running "coolly" .
Video please .
Cheers John
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Post by smithy1 on Feb 25, 2016 18:22:46 GMT -5
My whole life revolves around "senior moments"...I guess that's what happens on the wrong side of 50!!
Just make sure you don't weld the V-band/shroud to the turb wheel...we don't want to see you cry like a little girl..!
Does your rotor assy need balancing?? Happy to do it for you..!
What sort of dry thrust do you think you'll have..!?? I'm guessing ~180-190lbs. After that we can pretty much add ~30% for wet..!
Cheers, Smithy.
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Post by racket on Feb 25, 2016 18:43:02 GMT -5
Hi Smithy
Theoretically ~210 lbs dry and close to 300 lbs wet .
Rotor balanced by the nice guys at the local earthmoving machinery companies own turbo workshop .....http://www.expressway.com.au/ , they've taken your advice and got it down to minimal numbers for me .
LOL...........yep , I'll be careful with placement of the earthing during the weld ;-)
Cheers John
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Post by smithy1 on Feb 25, 2016 19:09:39 GMT -5
Damn....300lbs.. ....that'd go well in the "Beast"...would be close to 1:1 power/weight ratio..! And a lot smaller total assembly than the GT6041 setup with it's external CC 'n all. Great work Sir. Smithy.
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Post by racket on Feb 25, 2016 21:26:32 GMT -5
Hi Smithy
Sure would , but think how 250 SHP would go
Cheers John
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