After a year, and dozens of satisfactory flights, yesterday the 41 on my TFGS Mustang broke.. The front shaft broke just in front of the flywheel, the keyway is still there?, the flywheel, prop extension, 5" spinner, and an 18-12 prop departed thru the front of the cowl.....immediately tail heavy, it shot straight up, and only a topnotch pilot saved major damage by pancaking into a cornfield... YES! The prop and spinner were carefully balanced, and have been on the engine since day one.
Has anyone else experienced this breakage...If there was a flaw in the shaft metal it wouldn't have last this long....This was a sweet running engine, but now it's post-mortem time...any comments?

Howard,
Suprised to hear about this happening. Were you able to find the hub, prop, and spinner? Wonder if the 12 pitch prop might have been too much for it?
Mike

No, noone really knew where it was when it left the scene.....After we had looked for nearly an hour, Myra said we were looking in the wrong place? Really like to have found it, as it will take about 75$ to replace.. I just saw the plane pitch violently straight up, then straight down..( with 2# off the nose, what else) Somehow.....Bob got the nose up, and lunging like a porpoise, got it to the corn to the east of the field..1/8th mi. How he kept the wings level? I dont know, as I was expecting the tip stall and a pile of kindling..
The 18-10 or the 18-12 is recommended, and it was turning it around 7200rpm. I'll be in the shop this aft. doing a post mortem..

Eugene,
You are a lucky man. If it had happen to me, the plane would be in a pile scraps. At least the US/Quadra cranks are easy to replace, since the rod slips over the front journal.

Dave

Dave,...
I'm at a loss as to what could have caused it. The front end hasn't been disturbed for a year, would have taken a pretty violent event to shear the shaft..I'll call B&B tomorrow.and see what can be done......
Patched a couple holes in the wing( cornstalks) and the cowl front....and it's ready for an engine.... Lucky?? I'm buying a Powerball ticket this week....

Almost impossible for the crank itself to break off, most likely thing is the threads broke off flush with the end of the crank...
It's an easy fix except for the 11 little rollers that the rod slips over....

RCIGN.. You got it.. close inspection shows right at the last thread, and it is the front of the crank.....Any thoughts on the cause? Little sucker has ran beautifully for over a year, never touched the needles...straight and level and WHAM!

I dunno, Ralph. I know of at least one engine where breaking the shaft on the crank is a fairly frequent occurrance, and prior ground strikes are never a possibility. However, the US engine line is not the one. There are some outside influences that help the process along, but by themselves are not enough to be the full cause.

Haven't seen one in a while, seems like they fixed THAT problem...

All engines are born with a predetermined, but undefined, number of "R's". Yours arrived at that point.

my manual has in it that I need to make sure that it is tight. If it comes loose it will brake the crank. I check mine every spring

Spring?? Everywhere I go it seems to always be summer anymore, or at least seem like. I'd be in a world of hurt if I waited for my next spring Then again, at my age the word spring isn't associated all that often with anything anyway. More like plod...

Eugene,
I think that tellspin hit right on the head. The hub came loose as soon as it had a small gap,then flight forces allowed it to focus stress on the thread groove next to the flywheel. I seen bolts that where streached, due to over torquing before they broke in other applications. Goodluck in the Power Ball.

Dave

Dave,
Well, I guess this aint my week.. I lost an engine, the Powerball ticket was a loser, I picked up a prostitute, and she had a headache... I think I'll take up golf.....

Doing some golf might be a good idea as at least your balls will be out of all danger

Karol

Not the way I play golf!

Bedford