Extracting broken crankshaft stud from Jett 426 engine
Posted: Wed Jul 19, 2023 8:03 am
I get to the Nat's and first thing I do is put together one of my quickies just to get an early evening engine run. I go to tighten the prop and snap! Within about 30 minutes of my arrival at the 2023 AMA pylon racing Nat's I've busted the threaded stud in the crankshaft of my #1 plane. Next thing I know all the usual suspects (Trey Witte, Mike De Neve, Terry Frazer, Adam Oswald) lend their tools and assistance to help me extract the stud, but nothin' doin'. We tried various types of drills in various sizes, a hammer and a few different screw drivers, but nothing would work. I have two other engines on two other backup planes, but Trey loaned me the crankshaft from one of his Jett engines configured for 424 which had already finished. I get my engine back together with Trey's crank and all is well and I have a pretty good 426 Nat's.
I was pretty sure Dub must have seen this before (more likely from a crash rather than gorilla hands), or I was wondering if I was going to be the first guy with a stuck crankshaft stud. If he'd seen it I was sure he'd say "oh, yea, that's easy to fix..."
Sure enough, when I showed it do Dub he said all you do is take a Dremel cutoff wheel - the stone kind, not the reinforced one, grind a slot into the stud and screw it out. You'll end up grinding a slot in the front of the crank, but that doesn't hurt anything. A few days later back home in my shop, I found a stone cutoff wheel, ground a slot, and voila, the stud screwed right out! It took all of about 60 seconds - literally! That would have saved me and my friends a lot of time and grief at the field.
So if something like this ever happens to you, just whip out your Dremel, or come see me - I always have a Dremel and cutoff wheels in my tools. Then you can get back in the air right away.
Nobody I've talked to has ever seen this before - a crank stud breaking not from a crash. I have to guess the stud in my engine must have already been compromised from a crash or some other incident. The QM engine uses the same stud. For the QM engine, Dub admonishes to change the stud
regularly, like every race event (this could be possibly 10 - 20 flights I assume depending upon whether it is a one or two-day event I suppose). I keep a record of when I change the stud in my QM engines, though I usually go an event and a half or two before I change the stud (not that I'm an authority). Dub also says to change the stud in the QM engine any time you have a prop strike while the engine is running - such as on takeoff. Finally, still for the QM engine, never leave the prop tightened overnight.
Dub didn't say of often to change the stud in the Quickie engine, but I would have to imagine once or twice a year, or whenever the stud experiences any kind of impact.
Tim
I was pretty sure Dub must have seen this before (more likely from a crash rather than gorilla hands), or I was wondering if I was going to be the first guy with a stuck crankshaft stud. If he'd seen it I was sure he'd say "oh, yea, that's easy to fix..."
Sure enough, when I showed it do Dub he said all you do is take a Dremel cutoff wheel - the stone kind, not the reinforced one, grind a slot into the stud and screw it out. You'll end up grinding a slot in the front of the crank, but that doesn't hurt anything. A few days later back home in my shop, I found a stone cutoff wheel, ground a slot, and voila, the stud screwed right out! It took all of about 60 seconds - literally! That would have saved me and my friends a lot of time and grief at the field.
So if something like this ever happens to you, just whip out your Dremel, or come see me - I always have a Dremel and cutoff wheels in my tools. Then you can get back in the air right away.
Nobody I've talked to has ever seen this before - a crank stud breaking not from a crash. I have to guess the stud in my engine must have already been compromised from a crash or some other incident. The QM engine uses the same stud. For the QM engine, Dub admonishes to change the stud
regularly, like every race event (this could be possibly 10 - 20 flights I assume depending upon whether it is a one or two-day event I suppose). I keep a record of when I change the stud in my QM engines, though I usually go an event and a half or two before I change the stud (not that I'm an authority). Dub also says to change the stud in the QM engine any time you have a prop strike while the engine is running - such as on takeoff. Finally, still for the QM engine, never leave the prop tightened overnight.
Dub didn't say of often to change the stud in the Quickie engine, but I would have to imagine once or twice a year, or whenever the stud experiences any kind of impact.
Tim
