Banker

My Feedback: (10)

Has anyone had issues with a 3w-106 throwing a prop lately? I have used this set-up for several years and recently I have thrown several props. This is getting expensive.

JohnVH

My Feedback: (38)

Check them after every flight for a while, they are probably loosening up and then chucking them.

tailskid

My Feedback: (34)

Watch the size of bolts you are using...I believe they are metric and VERY close to an SAE thread - but not quite. I used a set of SAE's and sure enough, it threw the CARBON FIBER prop and of course chipped it

Jerry

Banker

My Feedback: (10)

These were all 5MMx50MM bolts. Exactly as furnished by 3w.

sillyness

My Feedback: (25)

Is it wood prop? Has it compressed to the point where the bolts are bottoming out?

Diablo-RCU

My Feedback: (1)

I have two seasons on a 3W-106, maybe 450 flights. Never threw a prop or broke a prop bolt on any engine. Using mostly Mejzlik props with an odd use of either Menz-S or Biela. Loose bolts break from fatigue. Tight bolts don't break.

Banker

My Feedback: (10)

They have all been CF props (Biela). Maybe they bottomed out. I was not using a spinner.

bhanley

Hope you work this out before one of these things hits someone.....

rmh

Do yourself a favor - remove the prop and screw in the bolts -such that they touch bottom of the holes
measure shank exposed length.
Now measure thickness of props used and washer on front.
Ideally --- you want the bolts to thread into the hub about 3/8" to 1/2" maybe more .
The total thickness of prop/washers is referred to as "stack height".
It is common that this distance will change with different prop brands types and prop spinner hubs --- over 1/2" .
Simply go to a bolt supply and buy a set or two of 5mm bolts in lengths aprox 5mm different in length --then use appropriate sets for the various combos .
The bolts -from a reputable house will cost 25 cents each or a bit more .
These are metric and should be equivilant to about grade 7-8 whatever . hard but not the hardest.
Some import metrics are soft and varied in grade .
These easily distort in the hex socket ,allowing the key to slip.

3D ONdaEDGE

On a Grade 8 bolt you want the thread depth to be the same as the diameter of the threads. For example, if you are using a 5mm bolt you want 5mm thread engagement. This is for a Grade 8 coarse thread bolt, but if you can get 5mm of thread grabbing in the hole then you are fine. Mine engage about 1/2" so if you can between 1/4 and 1/2 it will be fine.

PlaneInsane

My Feedback: (5)

Banker, I went through this last year when I switched to a carbon prop. Kept breaking bolts every flight. The solution was to dial in the prop stud that holds the front hub on. Put a dial indicator on the tip of the prop stud and see how far out it is. Tap it into square. This stud isn't a precision fit and the backside of it is conical in shape which allows it be centered by tapping. You won't bend it so don't worry about that. You might also want to retighten and then recheck a few times.

RTK

My Feedback: (1)

Kinda of topic, but if you need to by bolts, fasteners, etc try Mc Masters-carr. You can usually buy 50 for the price of 5 from the dealers. Items can be hard to find on there web site, so call them and they will help.
http://www.mcmaster.com/