ShoestringRacer

Wow, this is all news to me. I am glad I made this post! I had no idea this stuff happens and how much force it all shows.

I am guessing the use of threadlock on the prop shaft/nut would not help very much.

What about making the nut really, really tight?

Hobbsy

My Feedback: (102)

Throwing props is not limited to fourstrokes, one of my Fox Eagle .74s threw its prop but did not stop running, it made a sound I will never forget, not unlike an Indy car. I was totally surprised that it didn't throw the rod, but I put the prop back on and it ran fine. I had a Mac's tuned pipe, a Perry pump carb and a Perry regulating pump and got it a little lean.

rcplane-RCU

My Feedback: (7)

Hey showstringracer, I started the thread about the backfire on my OS Surpass II a few days ago and never got this much information! I have read this all today but Before reading this today I took my plane to the field and leaned the high end a bit from information given to me from my post and it did NOT backfire although all the while not trusting it at any time. My first backfire with this motor sent an APC prop and spinner flying, the prop hit a steel post behind the plane breaking it in two sending one piece at a fellow modeler hitting him in the hat/head just above the bill about 1/2" cutting him but luckly not badly, The hat saved him from a worse cut I am sure. But even though my motor did not backfire I traided it to another modeler before leaving the field. I personally think this OS Surpass II with Pump(oldversion of unknown date)should make a fine paper weight!
The information learned from everyone here I appricate and will use it on other 4-strokes but never will I own that one again. Thank you all for your answers and your help. Mike

Ladyflyer

My Feedback: (2)

Like the guy said ,two strokes will toss them too !
Many fliers fail to double nut when using spinner adapters . Even with the double nut the spinner can get loose and take an unexpected high velocity trip and it has no concern for what ever is in it's path.
It is a good idea to minimize your exposure ESPECIALLY when running up the throttle or adjusting the needle valve. Again this applies to all engines .

CLBetten

My Feedback: (16)

This subject has been pretty well driven home on this thread but I can't resist saying it again. I was at the field today and an older member with probably 40 years of experience was tuning the high needle on his fairly new 150. He had likely gone more to the lean side than you should but I would hesitate to say he had even peaked the r.p.m. He had removed the jam nuts and was only using the washer and a threaded spinner nut. It backfired with no warning so violently that it tossed the propeller at least 60 feet forward and to the right of the plane. It missed his head by probably 4 inches. He was saved by blind luck. I would bet if it had hit him even in the torso and flat he would have been on his way to the E.R. I will NEVER stand by a running prop. without FULLY EXPECTING that it is coming off. I have been an automotive and heavy equip. mechanic for 22 years and I've seen some spectacular mechanic failures, but I learned a lot of respect for these little glow motors today. Take care, Cliff

David Smith

My Feedback: (1)

When I was about 12 years old I saw a 2.5cc diesel throw a prop blae. Never stood in front of a running engine at speed since that! You never forget it once you've seen it.

Phil Heller

My Feedback: (9)

The worst engine I ever had for prop slinging was an O.S. 120 - the old style, pre "Surpass"! I don't know what the Comp. ratio was but there are several 16-6 props all over Northern California that "took off" while the engine was breaking in on the bench in my back yard. It took about 3 gallons before it stopped that nasty habit. Also had an OS61fx shed a prop in flight - had a Mac's tuned pipe and sounded like an air raid siren! (For those who can remember!) I also have an OS 130Twin and an 182Twin
Enya 80, 90, 120R and 155R, none of which ever slung a prop!

Keep slightly rich and double nut or locknut. Play it safe and always adjust from the rear (except in the case of a pusher!)

Phil