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Flywheel bolt snapped saga

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Flywheel bolt snapped saga

Postby Garyo » Wed Dec 23, 2015 6:13 pm

Decided to do my flywheel bolts as weather bad, last done 18 months ago
All seemed to break the 620 easily and the last 1 fell out in my hand when I turned it.
After strip down the bolt has sheered were it goes into the crank right across the face so no chance of getting a purchase on it, it will have to be drilled and removed with an extractor

Could of been worse in flight, these engines are Lots of poo poo
Deano is machining a drill guide, so hopefully it will work
In the pics you can see with the timing gear backed off the sheered bolt, reason gear not fully off is it locked itself in that position when trying to remove it.

The old bolt against a new bolt in the other pic.
Tomorrow I will go to hanger and inspect all the parts
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Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
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Re: Flywheel bolt snapped saga

Postby Kai Lyche » Thu Dec 24, 2015 8:51 am

So, Garyo, my man-

Clearly not the best of x-mas occurrences!

But, lesson learned: with these motors, what you don't see, you still have to worry about :-)

With the kind of fretting the pics show, something has been seriously under tensioned. Prop bolts? Prop flange? Flywheel bolt heads digging into the soft aluminium flywheel boss? Maybe some kind of ignition discrepancy? Or perhaps just the prop just over pitched?

Experience has shown the possibilities are almost endless. Do yourself a favour, eliminate at least one of them by installing the now LAA approved flywheel attachment modification. It will ease your mind a bit.

Good luck, and merry x-mas!

Kai
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Re: Flywheel bolt snapped saga

Postby diablo » Fri Dec 25, 2015 4:23 pm

When attempting to drill out a broken bolt, by far the biggest problem is ensuring that drill bit is centered on broken stud. I have machined a 2.5 mm and a 5.0 mm jig that fits on vacuum pump drive adapter t ensure that bit is centered. A very good drill bit is a must. Nothing but the best is adequate.

IMG_4679.JPG
Drill bit centering mini Jig (5.0mm)
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Sent from my "Electronic Numerical Integrator And Calculator" E-N-I-A-C
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Re: Flywheel bolt snapped saga

Postby Garyo » Fri Dec 25, 2015 7:32 pm

Going to get some cobolt drill bits and a cobolt burr, use the burr first to go through the jagged bit to provide a base for the drill. I think using my vac drive wont work as the drill chuck will be hitting the end of the drive
Now need a plan 2
Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
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Garyo
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Re: Flywheel bolt snapped saga

Postby Kai Lyche » Mon Dec 28, 2015 4:07 pm

Way to go!

You are now reaping all the blessings from the manufacturers use of Locktite 620. However, with your approach I feel confident you will get the studs out.

Have you already decided in what way you will assemble this again? Manufacturer original? N-Z mod? Something else?

Kai
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Re: Flywheel bolt snapped saga

Postby Garyo » Mon Dec 28, 2015 4:17 pm

I will prob go with nords, not sure. I cannot do the full mod as it will clash, i dont think the full mod or nords would of prevented the stud from snapping as its gone on the crank face, still confused as to why it went, i must have a vibration frequency some were, aircraft has always been smooth no vibs.
Will check the prop end though. There was fretting marks but all surfaces smooth.
Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
User avatar
Garyo
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Posts: 323
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Re: Flywheel bolt snapped saga

Postby diablo » Mon Dec 28, 2015 5:33 pm

Gary,

My view is that there was movement and quite a bit going by the thread marks on your vacuum drive adapter and fretting. I would not be comfortable with the vacuum drive adapter being stuck on the flywheel as it could well be an indication of something not quite right there !

If you are unable to dislodge the vacuum drive adapter how are you going to be sure that the assembly is torqued up correctly and what's to stop it all coming loose after hours of use? If the parts are jammed together, you have no idea if they are correctly seated and as we all know, it does not take much for it to all go tits up! I tolerances in that area are very tight. Flywheel and vacuum pump faces should be withing 1-2 thou (0.02mm) ! I would Twit it and check it.

I would do what I have to to separate the vacuum drive adapter from flywheel and inspect surfaces. I would also ensure that there is no fretting between the flywheel and vacuum pump adapter. My honest opinion is that you would be better off with nordlocks (no compression ring) which will give you the advantage of not having to use 620 but as Clive mentioned, probably a good idea to use a drop!

Bits are in the post. There are two mini jigs and a machined vacuum pump adapter (minus protruding adapter). Mini jigs for ensuring bits drills through center of bolt) are:

1 x 2.50mm aly
1 x 5.00mm brass

I would have used steel but I was in a rush and could not find any 10mm steel rods to machine down to 5/16". Make sure you grease jig (minimize wear and dont worry about mangling them as I do not expect to have to use them again and they are easy enough to make.

You are welcome to fit the modified vacuum drive adapter if you like. Just send me your old one and I can modify it (I like to keep one handy).
Sent from my "Electronic Numerical Integrator And Calculator" E-N-I-A-C
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Re: Flywheel bolt snapped saga

Postby Garyo » Mon Dec 28, 2015 5:43 pm

Also had a blonde moment today, decided to clean out the timing cover screw holes, sprayed the top one and used an instrument cotton bud, got some mess out then the cotton disapeared, so got my pics out and tried to pic out the cotton top, the hole is not blind so I found out, the cotton top exited the hole from the rear and dropped onto the top of the crankshaft. Sorted I thought, with the wrong specs on I went to it with the pic and then.................it disapeared!!!

So after 20 mins searching it was deemed inside the sump as it must of dropped behind the timing gears direct to the sump, so the next thing is do I leave it in, do I drop the oil and hope its in there

I then spent a further 10 mins with the pic poking, i could not see fully behind the gears so i poked about and to my amazement i seen something drop, it was the cotton tip, it must of stuck to the gear, it now landed right on the flange at the bottom, so I carefully went to it with long nosed pliers and managed to get hold of it, phew, I wiped the tears away, put the cowl back on and went flying in the C42

Lesson learned, ensure all open engine areas are covered for dropped objects. If this went in the oil systen it could quite easily work its way round to the head oil feed pipe and bloke it.
There is a jab engined twister in the uk that was rebuilt and a bit of rag left in the engine, the engine destructed shortly after.
Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
User avatar
Garyo
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Posts: 323
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Re: Flywheel bolt snapped saga

Postby Garyo » Mon Dec 28, 2015 5:48 pm

We must of been posting at the same time..
Agree on the flywheel, I am not comfortable with it still on, but I cannot shift it and cannot shift the magnets. Will see about getting an allen key soket to see if I can move the screws in the magnet ring and get that off. I dont want to belt it with the magnets in place, also have the same issue with the mag magnets, this is a pain
Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
User avatar
Garyo
Site Admin
Site Admin
 
Posts: 323
Images: 4
Joined: Fri Feb 06, 2015 7:52 pm

Re: Flywheel bolt snapped saga

Postby Garyo » Tue Jan 05, 2016 9:30 pm

Its out!!
Started at 3mm and worked to 4.5mm, 5mm is too big and could damage the threads. Cobolt drills ran at a slow speed went through the ht steel like butter, never even got hot, did not use any coolant.
Heated the crank, then used a number 3 easy out, little pressure on it then it started to move, got it out, all ok, chucked the cover back on and went home.
Thanks for the loan of the spacer Deano, CJ thanks for the loan of the drill.
Dean what is your addy to send the part back, CJ will catch you hopefully at the wend, see pics
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image.jpeg (231.54 KiB) Viewed 5748 times
Former Owner of
G-OMER
Jabiru 450 UL
Engine serial 1041
1 CHT sensor on No 4 under plug
No Exhaust temp sensors
No glass panel
No xponder
Microair radio
No bells and whistles
User avatar
Garyo
Site Admin
Site Admin
 
Posts: 323
Images: 4
Joined: Fri Feb 06, 2015 7:52 pm

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