Extracting broken crankshaft stud from Jett 426 engine

[KRProton]

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

[cpaine]

Excellent! Dub to the rescue!
I have also done this many times at work with pretty good success. Another trick i do, is to grind the stone wheel on a piece of steel (wearing it down) to give it a smaller diameter, helps minimize the size of the cut (damage to the exterior) and helps get at smaller screws if needed.

Cheers
Cory

[Greg Doe]

Left hand drill bit in a reversible drill will usually back them out. You have to let the drill get a good "bite" which requires more force then you usually use when doing normal drilling. McMaster Carr is a good source.

[rocket]

Cool tip, don't screw the stud all the way in.
Cooler tip Ala grunkemeyer. Cut a 1/4" piece of fuel line and drop it in the hole before you screw in the stud. This will keep it from bottoming out and binding up. In the event you need to remove it.
Even Cooler tip. Look at the pointed end of the stud. If it has a grind mark it's the hardened stud for QM. No grind mark its its the softer 426 stud.

[airplanescotty]

Upon my Apopka Florida return to Pylon I was introduced, By Rocket ,,, to Mr. Dennis O'Brien!

I needed everything so immediately became Dennis's best customer, spent WAY tooo much time in his garage

When we got to the Engine education portion of my Pylon re-entry, Dennis told me, made a big deal of it, insisted that I follow his dictate,,,,,,,,, the following::

Cut off a 1/4 inch piece of fuel tubing, insert it into the Crank hole, then screw in the Stud until it makes contact with the fuel tubing! This keeps the Stud from bottoming out against metal and becoming tight,, then when it brakes, there is minimal pressure on the stud thread and it just unscrews

Lastly,,,,, when I get my motors back from Dubb, I noticed he ALWAYS,,, always,,, puts a new Stud in the crank!!!

Scotty

[T.Doe]

Wish I would have known, I had a tap out with me along with all my drill bits. And my dremel

[KRProton]

Wish I would have known, I had a tap out with me along with all my drill bits. And my dremel

A tap. Nothin' doin'. Couldn't even drill a hole. The point is, forget about drilling. Just cut a slot with a Dremel and you're on your way. I always have my Dremel and attachments, including a cutoff wheel. Would I have known, I could have fixed it right away.

Live and learn.

Tim

[airplanescotty]

My first lesson with the Dremel Tool,,,, With it,,,, one can conquer the world!


Scotty