Hirth Crank Case Cracks in Flight

[NoWingsAttached]

See attached photo. I was already setting up a landing, so it wasn't exactly a forced landing...sorta. I always thought the little bit oil showing up from the exhaust port area was coming from a leaky gasket. I wiped it clean after every flight so i could see any increased leaking, and never noticed any difference. Now I see it was a crack that never got bigger..until today.

[NoWingsAttached]

I was actually getting ready for my first cross country of the season, over Lake Tara and doing a simulated engine-out on our dam. I drained the seat tank (changing oil brands from Blue Marble to Quicksilver) and put in a fresh 5 gal. I decided to stay close to home for a while to see if there were any burps before I went the 15 miles to the lake, and on up to the granite quarry.

[NoWingsAttached]

Headed upwind for 10 minutes, up to 800 ft, and turned back to the airport. Plan was to land, top up the tank and head out downwind to the house for a neighborhood fly over. Some new neighbors haven't seen gyro fly yet and wanted to go out on the lake in their boats and hang out til I showed up. A tractor, "Poppa" was flying in and out of CJT from the NW for fresh loads of whatever he was dusting with. A shiney new LSA was moving from her hangar base to the taxi way. A yellow Champ was doing touch and goes. The Petes were still on the ground, one in front of the EAA hangar.

I felt some strange vibrations, and throttled back smoothly. It felt like a prop vibration. I brought back the power and felt the vibration throughout the power range, so nope, It must either be the engine or the gearbox.

I called out "Crossing the RW midfield at 600 ft from the west", and saw the neighbor's Citation rolling down our apron to the RW 17 approach for takeoff against the active 35 at the north end of the strip. Dang, that's right where I want to land dead into the 5-25 mph 270* winds. With plenty of altitude I throttled way back and circled around, dropping to 300 AGL while the jet took off. I called out a helicopter approach and landing for the fictional RW "26", but I had too much altitude on the first attempt, the wind didn't do what it was supposed to, and I decided to it was easier to call out a second attempt, this time alerting ground that I was in some trouble with unknown vibrations and needed the air space to do a tight circle back for another lineup for 26. With a lot of rubber necking I came back around into the wind and dropped her perfectly where I wanted. But the vibrations were definitely getting worse, it seemed like the throttle response was way down when I was trying to keep up AS and do my go around.

All's well that ends well, but this engine is kaputski, Demetri. I is repairable, but not before Bensen Days. Anyone got Hirth 65hp bottom end case?

[jcarleto]

Bummer, Gerg!

I'm glad you made it down OK though. Good job.

[MrGrey]

Recreational Powersports in Ohio is your only bet to find something for that engine. a 2705 is like a 2706 but not identical. Keep in mind that it is a discontinued engine. They might be able to set you up with a 2706 case but no guarantees. For the cost you could prob get a nice used rotax 582 to replace that hirth and eliminate some worries. It may not just be the case... crank could be outta whack, bearings shot, ran lean on a cylinder from the air leak...etc. It may have been damage sustained from your roll over at Bensen Days and the consequential prop strike.

[scottessex]

Gerg, Greg, Dude.... I have a 2706 crankcase and crank, not sure what the difference is, less than 200 hours.
You might be able to still fly at Bensen days...

[Earthboundmisft]

Greg, the crack appears to originate from the bolt hole. What does that bolt hold in place?

[scottessex]

That holds the cooling shroud.

[MrGrey]

Gerg, Greg, Dude.... I have a 2706 crankcase and crank, not sure what the difference is, less than 200 hours.
You might be able to still fly at Bensen days...

http://www.recpower.com/

This is the site for the info you need regarding that crank. Give em a call.

[NoWingsAttached]

Recreational Powersports in Ohio is your only bet to find something for that engine. a 2705 is like a 2706 but not identical. Keep in mind that it is a discontinued engine. They might be able to set you up with a 2706 case but no guarantees. For the cost you could prob get a nice used rotax 582 to replace that hirth and eliminate some worries. It may not just be the case... crank could be outta whack, bearings shot, ran lean on a cylinder from the air leak...etc. It may have been damage sustained from your roll over at Bensen Days and the consequential prop strike.

Thanks Matt, good thinking, it is a pretty good possibility. But I've flown a lot of hours since the prop strike, I would have expected failure to have occured a lot quicker than this if related to the prop strike. I think it was seeping prior to the roll over. And this is a pretty strange place to show wear from a prop strike, after all. This engine has GOT to have a lot of hours on it, judging by the year it was built, how much fun you and I pulled out of her. Hey, I'm going to blame it on the change to Quicksilver oil, LOL!

Interestingly I was marvelling at how smooth the motor idled while I was warming up for this flight session!

[NoWingsAttached]

Gerg, Greg, Dude.... I have a 2706 crankcase and crank, not sure what the difference is, less than 200 hours.
You might be able to still fly at Bensen days...

Let's get together and compare parts when I pull it apart. PM coming your way to plan a meeting at your place next.

[automan1223]

Why are you messing with hirth. Take it off, throw it away.

Your life is worth more than a crappy hirth P.O.S.

J

[Brian]

how about a used 503

[NoWingsAttached]

...Your life is worth more than a crappy hirth P.O.S.

J

John

The jury is still out on that, LOL!

[NoWingsAttached]

how about a used 503

Brian, are you selling? Send me a PM with price and what comes with it. Hours on it?

[MrGrey]

Go to Barnstormers.com, search Rotax, Buy Engine, Mount Engine, Go To Bensen Days

[Brian]

greg no I dont have one or we could make adeal just thinking. If mine quit i would be out for a long time sorry i cant help brian

[NoWingsAttached]

Go to Barnstormers.com, search Rotax, Buy Engine, Mount Engine, Go To Bensen Days

Looking I am, ebay and the barn

[NoWingsAttached]

Go to Barnstormers.com, search Rotax, Buy Engine, Mount Engine, Go To Bensen Days

Thanks for your ultra-secret formula. I am trying to follow it to the the letter. How does this sound? Found it on Barnstormers, just posted for sale yesterday 3/17. I called. It was already sold when I talked to the guy! But he said he hadn't any received money yet, and would let me know Monday one way or the other if the buyer came through or not.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~

ROTAX 503 REDRIVE AND PROP • $1,500 • AVAILABLE FOR IMMEDIATE SALE • Rotax 503 si dc 55 hrs tt magnum redrive and ultra prop 3 blade com and get it • Contact Rich - located Orfordville , WI USA

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~

Rich just called me back this morning. The buyer's wife nixed the deal. My turn. His friend is Hooker, the guy who makes seatbelt harnesses for aircraft, and Hooker is heading to Sun n Fun 3/23 to set up his booth early. I could interecpt him on I-75 and grab the motor, gearbox and prop out of his van, so no shipping fees. Wow. Alternatively, Rich's father is a trucker, and he is heading to Florida Sunday, and will be rolling through ATL Monday. I told Rich I'll buy his dad lunch or dinner or whatever for his time pulling over to let me pick up what falls off the back of his truck, lol.

No shipping charges?!?!?! Delivery in ONE business day!?!?!?! $1500.00 all-in!?!?!?!?!

Is this a dream? Is this divine intervention? Does God want me to switch to a Rotax? Will I meet you guys in Wauchula with a flying Gyro? (I won't be able to leave the airspace however, but with all the flat, wide open pasture land there I'm not too worried.)

Yes, yes, yes, maybe, could be, perhaps, and...YES!

[scottessex]

That is a OLD points single ignition, with a belt redrive, Make sure it is what you want, the prop and prerotator will turn the opposite direction. I think that grant has the same engine for the same price listed on here somewhere. I think he even has the prerotator setup on the engine..

[NoWingsAttached]

Jon Carletto told me the same thing, but I can't find the listing here. That would be better yet, and i can drive over and pick it up right away. I had his phone number around here from WRENS last fall, but now I can't find it. ANyone have his phone? PM me if you do.

[NoWingsAttached]

Grant already sold his drive train. Tell you the truth, I feel a little silly. I trailered Blue Bee home last evening, and took off the cooling shroud this morning. Yuk, what a mess. I started right in with the kero cleaning. Um...the crack is not a crack. See blue circle in second photo. It's just the first time I let the gyro get this dirty, and oily slime goo with dirt got into a little nook and highlighted a flaw in the casting. When I wiped it down, it looked, felt, and fooled me into thinking it was a crack.

I still couldn't be certain after closer inspection, so I sanded with emory cloth. That wasn't aggressive enough, so I used a fine wire brish to smooth out the casting flaw. Sure enough, ain't no crack.

So what gave me the notion in the first place, since it REALLY looked like a crack?

See the broken exhaust mount circled in red, below. As soon as I put a wrench on it during the first stage of tear down I found it, like the fourth or fifth bolt I removed.

Can I get a "Yeah, come on!"? Giddy-yap!

And with that, the Wiley X Lone Ranger slowly rides off into the sunset.

[scottessex]

I guess you found your vibration.........Looks like you'll make Bensen Days with a gyro after all. :D

[automan1223]

I would still take the hirth off and use it as a door stop or a boat anchor.

Get a rotax !

[NoWingsAttached]

Well, if it ain't broke, I ain't fixin it. It don't matter WHAT kind of 2-cycle you fly, you'd better have a landing spot all picked out and ready. I just hope Bensen Days is FUN! This is a huge relief. I love flyin, and I am one grumpy old fart when I can't do it.

[NoWingsAttached]

I guess you found your vibration.........Looks like you'll make Bensen Days with a gyro after all. :D

Yeppir zee doodle!

[NoWingsAttached]

I got the new exhaust gaskets, plugs, EGT probe, Jon Carleton sent me a new plug boot. The motor is back together and ready to ground test. The exhaust bracket is replaced, and i added a bit of rubber to soften the vibration, though it could arguably do with more shock absorbing material.

Decided to go through every nut and bolt. Took the mains off completely, and got the wheels all lined up for the first time ever. The tread wear was terrible, the ground handling obnoxious. I still need to bend the right axle back a degree or two, then everything should be perfect.

Been cleaning everything up with kerosene and then purple polish. New fuel lines are finished.

I have always disliked the tail. It looks nice, but it handles poorly. Flying in a cross wind, and landing, you have limited control against a strong weather vane effect. When you throttle up to take off, nose up, you can wind up heading into the grass in even light cross winds from the right.

So i am earnestly working on a full-height tail, set much closer to the prop. If I can't finish it before B-Days i will re-mount the original blue tail in the picture. Some of you may recall my thread about experimenting with heavy aluminized mylar bonded to foam, to make air foils. I bought a plain laminated door, and set up a foam cuttin table this weekend. Got some promising results running a few test pieces through it. I guess all that's left is to cut the jig from some plate aluminum, or even wood.

I got my bandsaw running again, and when I installed a new bi-metal blade ( I long ago installed a step-down pulley to slow the blade speed way down) it wouldn't cut!

The band was shipped rolled inside oUT!!! First time THAT ever happened. I had put it on with the teeth pointing up - backwards! It never occured to me to carefully inspect the blade first to be sure they shipped it inside-out or correctly. Jeez. Very strange. Ever had that happen with your new bandsaw blades?

[Passin' Thru]

The band was shipped rolled inside oUT!!! First time THAT ever happened. I had put it on with the teeth pointing up - backwards! It never occured to me to carefully inspect the blade first to be sure they shipped it inside-out or correctly. Jeez. Very strange. Ever had that happen with your new bandsaw blades?

Dude, Dude, Dude! You do have a serious problem, but it ain't yo' bandsaw blade!
There is no inside or outside of a band. Just lay the band on the table with the teeth up, grasp 2 opposing sides and flip it inside out. Now the teeth are pointed down. Now turn it over and the teeth are up and hooked in the right direction. :drama::yo:

[C. Beaty]

How about just turning the bandsaw upside down?

[NoWingsAttached]

Dude, Dude, Dude! You do have a serious problem, but it ain't yo' bandsaw blade!
There is no inside or outside of a band. Just lay the band on the table with the teeth up, grasp 2 opposing sides and flip it inside out. Now the teeth are pointed down. Now turn it over and the teeth are up and hooked in the right direction. :drama::yo:

Duh, yeah, but Dude, I've bought I dont' know how many blades over the years, and never have I received a new one that was flipped. I've accidentally flipped skinny blades, but you have to be determined to flip a 1/2" blade like this one. Someone's idea of a practical joke is my suspicion. Bored S/H guy on the dock. AND, unlike a wood blade, the teeth are pretty small on a bimetal one, so I would have to have gotten out my reading glasses first to see it, or feel the snag with my thumb. Like i said, it never occurred to me before ! LOL, have fun pokin fun at me tho, I do deserve it!

I mean really, a cracked block that was just dirt in a casting blemish? Backwards saw blades? What next? I must be gettin old.

[NoWingsAttached]

How about just turning the bandsaw upside down?

Yeah, tried that too, it still didn't work, LOL!

Also tried loading the material from the back. No luck. hehe.

[Passin' Thru]

Seriously Gerg, I have 3 metal cutting band saws, 2 vertical and 1 horozontal. I purchase various widths and pitch in 100 ft. rolls and cut to length and weld. I always flip them inside out when flush grinding the welds before tempering the joint. My widest ones are 1" wide. It's easy!

[C. Beaty]

Pete, I don’t know whether you remember Gary Yanson or not; he was the guy that for a grand finale would go to 1,000 ft, switch off the engine, flutter down, land within 20 ft of his trailer and back up to his loading ramps.

Anyhow, I once had to saw a 10” hole in a steel plate and as you know, this is done by threading the proper length of bandsaw blade through a pilot hole and welding the ends together.

Gary happened to stop by just after I had removed the blade from the saw with it still running through the 10” hole in the plate.

Gary said; “How in the world did you get that saw blade through that hole?”

I picked an old band saw blade and showed Gary how it could be turned inside out and twisted into multiple loops. I said; “You twist it a certain way and it’ll snap right in the hole.” Gary played with that thing for an hour without ever catching on.

He was much better flying gyros than solving monkey puzzles.

[Passin' Thru]

Yes, I remember Gary very well. He could really make a gyro "walk and talk"!
He would also go to 1,000 feet and set up a flat spin to see how many revolutions he could make before "tree top level". I think we all learned that you could wind it up tight enough the gyroscoplc forces would break the prop shaft.