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beberle

Active Member
I've seen mention of two other occurrences of broken dip sticks on the forum, but no details. My dip stick cap came off yesterday with no stick attached. Stress fracture at the split pin retention hole. Luckily, it only dropped about 3" into the tube and I was able to retrieve it w/ needle nose. Clean break, so no concern of metal fragments in the oil.
So here's the question... Is there any issue with me replacing the aluminum rod w/ stainless? It's 3/16" and I've already fabricated the replacement. Thoughts?

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Until last weekend when a friend with an almost new Diamond Star DA40 had the exact same failure with it's LYC I0-360's dip stick I had never heard of this type of failure
 
Stainless steel comes in a wide variety of grades. If it is annealed 301-304, 321 and 347 stainless, its yield strength is lower than that of aluminum's, and would not be a particularly good choice. A better choice would be at least 1/4 hard.

I'd think that 4130 normalized, might also work.

Dave
 
Perhaps a dynamic prop balance is in order. Only you know how many hours might be on that dipstick.
 
This happened to me too

This happened to me several years ago.
I have no idea how old my dip stick was, engine came out of an old Mooney years ago.

As a repair, I just turned the aluminum rod around, match-drilled a new pin hole, tapped it into the yellow cap and pinned it.
Guess what. It broke at that end in a few months. Strange since no way the free end could have accumulated any past fatigue damage.

Then, I bit the bullet and bought a replacement dip stick. If you try to buy one from Lycoming, the price is ridiculous. But I found one at about half price from a supply house. Still kind of expensive for what it is, but oh well.

Your idea of a stainless one is good. Even though the yield strength of soft austenitic stainless is rather low, it has tremendous elongation to failure and fracture toughness. It will NEVER break.

You will have to do the oil level calibration of course, or just transfer over from your old one.

Oh, and by the way, the suggestion of needing a dynamic prop balance is a good one, although it was done in my case since engine was installed. But vibration will make the dip stick oscillate if it is near the natural frequency of the dip stick (pretty low) and can fatigue the rod.
 
I had to fabricate a new dipstick last summer. I used aluminum rod that I cut to length, drilled, and pinned in cap. The one other thing I did was use JB Weld when assembling. No problem so far. Dan from Reno
 
Superior XP-360 with less than 500hrs snew. Dynamic balanced last year. I was surprised that Spruce doesn't carry replacements and couldn't even find one on Ebay! ;-)
I'm a little surprised that this sounds like a not uncommon occurrence. I do routinely fly gentleman's acro and formation flight on a fixed pitch prop. Maybe that has some effect.
$5 for 2ft of stainless 3/16" rod. It was pretty easy to transfer marks. I'll give it a go.
 
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