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Post by stoffe64 on Apr 12, 2016 0:57:58 GMT -5
Can it be so that The engine is too drastic from what they use to be?
Try more voltage and really thick wiring to handle the amps
Good luck John!
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Post by racket on Apr 12, 2016 1:57:48 GMT -5
Hi Stephan
Yeh , Maybe I took a step too far with the modifications to the turbine wheel , its certainly testing me , but I won't give up too easily , still lotsa things to try :-)
Cheers
John
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Post by smithy1 on Apr 12, 2016 2:08:27 GMT -5
Hmmmm....I would've thought she would be happy at 21k for sure...!  You may be right with the "undersized" turbine wheel not having the balls at low rpm....Do you have access to a decent sized blower...!! All being equal, 36v may be the answer to get over that elusive hump, maybe the drag of the gear overdrive is a bit much for the starter??....Even from that short video it was accelerating quite well till the starter ran out of legs. You may need to pinch the battery out of the old Falcon mate..! Do you know if the blower you have there makes enough air to get her going?? I suspect not, but sillier things have happened... If you haven't had any luck by the time I get up there...we'll get the "old faithful" super blower onto it, no rpm restrictions with that old girl blowing..! Don't be dis-heartened mate...it's just a "teething problem". Cheers, Smithy. |
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Post by Johansson on Apr 12, 2016 2:14:05 GMT -5
Hi Anders LOL, I have thought of maybe fitting a sleeve into the inlet , but might leave it a tad longer before getting that desperate . It was very close , there were several seconds of running that I thought were idling , but then rpm slowly decayed and flames appeared out of the turbine wheel and I had to shut her down . I'm still not sure the starter motor is functioning to its best as that ~21,000 rpm didn't change even when more fuel was added , I'd have expected rpm to have gone higher, a bit more static testing required I feel . Yep , I'm feeling a tad deflated after the test , but not ready yet to turn the engine into a coffee table ;-) Cheers John I thought more like a removable blank that can be pulled away when the engine is running, not sure how that would affect the pressure buildup inside the compressor wheel though. |
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Post by stoffe64 on Apr 12, 2016 3:42:25 GMT -5
This engine is So big so it is difficult to start,maybe airstart like Jet kick has?
High pressure air or a large blower??
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Post by pitciblackscotland on Apr 12, 2016 3:57:50 GMT -5
Hi Smithy youtu.be/nlwsiHk6lRkUnsuccessful again :-( 21,500 rpm , 900-1,000 C TOT , nearly there , but rpm slowly decayed once the starter removed. Video is only ~20 seconds long as the camera battery went flat .................some days it doesn't pay to get outa bed . One thing that I can improve on is the earth cable back from the starter , it melted its coating , need a bigger cable to handle more amps .............maybe go to 36 volts as well. I feel the comp efficiency at low rpm is just too poor , requiring more horsepower from the "undersized" turb wheel than it can supply , maybe with more rpm things will come into balance ................LOL, dream on John ;-) Cheers John Hi John, Yeah pump up the Volts, remember Andrew has plenty of spare starters  Bloody hell she a big girl now that i see the vid  Keep at it John you will get her running  Cheers, Mark. |
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Post by jetjeff on Apr 12, 2016 5:26:14 GMT -5
Hmmm, just thinking out loud,,,from the video, I assume you're running it on Kero/Diesel, not propane? Have you thought about adding a small percentage of gasoline to the Kero?
Keep at it, you'll succeed.
Jeff
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Post by racket on Apr 12, 2016 16:21:43 GMT -5
Hi Jeff
Yep , running on kero , I don't think its a combustion problem though as the flame retreated back "inside" once the rpm climbed as it would normally do , I feel its still not enough rpm being produced by the starter to get over the hump of self sustain , it was nearly there for several seconds .
Cheers
John
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Post by racket on Apr 12, 2016 16:29:05 GMT -5
Hi Smithy
Nope , the blower won't cut it , not enough power .
I'll try 36 volts , then if no success, I'll go for high pressure air impingement , or a combination of both , I won't give up until I can produce at least 30,000 rpm (50% N1) during a spoolup attempt.
LOL, its a new day , time to get back into it :-)
Cheers
John
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Post by racket on Apr 12, 2016 17:32:57 GMT -5
Hi Guys Forgot the pic of the engine prior to the test  I'll do a test of the starter motor this morning whilst disconnected from the engine and running on 12V to get the "terminal" rpm on the output shaft as well as have a feel of it running to see if theres any issues with it . Cheers John |
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Post by smithy1 on Apr 12, 2016 19:32:46 GMT -5
That's the spirit..! Back into it indeed.! LOL...Love the "safety restraint system" you're using there John..! Looks like a neat trolley setup....I'm sure I've seen the same unit in person before?? But with a different engine of course..! If you feel the starter doesn't come up to scratch, it might pay to check the brushes, give the commutator a quick spin on the lathe to clean it up and clear the commutator slots etc... Is there a lot of rotor drag with the 70psi oil pressure?? If so, is it possible to bleed/by-pass some oil back to tank to lower the oil pressure a tad, down to say 30-35psi during spool-up?.... might help a little. then when she's up to idle you can close off the by-pass to get the full supply back again....just thinking out loud....which is a miracle for my lonely brain cell.. Keep at it young man...I have confidence in you..! Be sure to take frequent breaks for a nice cup of tea though..! Say G'day to your better half for me..! Smithy. |
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Post by racket on Apr 12, 2016 19:57:07 GMT -5
Hi Smithy
LOL, yep , she's tied to a tree in the yard , just in case ...........heh heh , you remember the time FM-1 started to "lift off " ;-)
I've done some testing of the starter with a freshly charged 12V battery , so ~13 volts , and with the starter held firmly in one hand and the tach in the other the output shaft only registered ~19,500 rpm , that equates to only ~6,750 rpm on the armature , a bit slow for a completely unloaded starter motor , not much vibration so my coupling must be reasonably "balanced"
Had a look in the gearbox and alls well there , the ouput shaft spins very freely in its ball bearings , so no undue drag there and the gears are nicely greased .
With the gearbox together its fairly easy to spin the armature by turning the coupling on the output shaft even with the 2.88 :1 disadvantage .
Motor might be "tired", I'll have a look inside and maybe replace it before going further with anything .
Theres not a lot of drag from the oil pressure , its possible to flick the comp around a few turns, not enough drag to be concerned with .
The better half is looking forward to saying hello :-)
Cheers
John
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Post by racket on Apr 12, 2016 21:41:25 GMT -5
Hi Smithy
Think I found the culprit , I put the armature in the lathe and got the dial indicator onto the commutator , theres considerable differences in height , up to 0.007" with one , the brushes were probably bouncing off it and losing contact once up to several thousand rpm , the insulation at the end of that high commutator segment is showing signs of "heat" whereas the rest aren't , so it looks like more Amps were going through it .
It might be why yesterday the rpm suddenly stopped accelerating during the spoolup .
Andrew is sending me some new bits for the starter so that I can give things another try before making major changes .
Cheers
John
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Post by stoffe64 on Apr 13, 2016 0:31:41 GMT -5
Fantastic News John, there is hope, othervise you up The voltage,dont give up my friend!!
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Post by smithy1 on Apr 13, 2016 3:45:41 GMT -5
Hi Smithy Think I found the culprit , I put the armature in the lathe and got the dial indicator onto the commutator , theres considerable differences in height , up to 0.007" with one , the brushes were probably bouncing off it and losing contact once up to several thousand rpm , the insulation at the end of that high commutator segment is showing signs of "heat" whereas the rest aren't , so it looks like more Amps were going through it . It might be why yesterday the rpm suddenly stopped accelerating during the spoolup . Andrew is sending me some new bits for the starter so that I can give things another try before making major changes . Cheers John Sounds promising at least...hopefully it will cure the "humping" issue for you..! If there's anything I can do/send you....just let me know..! Cheers, Smithy. |
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You may be right with the "undersized" turbine wheel not having the balls at low rpm....Do you have access to a decent sized blower...!! 
Bloody hell she a big girl now that i see the vid 
Keep at it John you will get her running 
