Shattering experience

[Keith Spriggs]

As you all know I am just getting back in to CL after 35 years. I have two Fox .35  and one .29 that hadn't been run in all that time. I got them freed up and decided to see if they would run. I had bought some new 10-6 props, but I had painted the tips and they were not quite dry and they hadn't been balanced. I had some old nylon 10-6 but I was a little leery about using them. I found a wood 10-6 that had never been used but it was as old as the rest. I thought that it would be safer than the nylon ones. I got both of the 35's to run and run them from rich in to 2 cycle several times. I had a little more trouble getting the .29 to start but it finally started and ran for a few seconds at a rich 4 cycle. I felt something lightly brush my arm and then the engine began to vibrate badly. I pulled the fuel line off immediately. When I looked about 2 inches of one blade of the prop was missing. It had broke pretty much square across. Too close for comfort.

[Leester]

Better get some APC's or Master Air Screw props. Don't forget to use 10-28 or 10-29 fuel in them Foxes don't run that R/C Kool-Aid.

[Ron King]

Keith,

First of all, I am glad you are okay. I always wear safety glasses when I'm working at the test stand because I'm always hovering around the engine, tweaking needle valves, etc. and I'm afraid something like this could happen to me.

This is very unusual. Could you please provide more info? Did you use an electric starter, your finger, or a chicken stick? Could you have nicked the prop while starting? Could you have cracked it slightly while tightening it onto the shaft? I've never seen a Fox stunt engine develop enough power to simply shed a blade.

Old age is not a problem as a rule. I have some props in my basement that are 40 years old and they are still in great condition. In fact, I think the wood and the grain structure are better than the new ones.

Thanks,

Ron

[Darrell Mims]

   Speaking of Props , What kind of wood is BY&O props made of ?  They have some strainge wood grain in some of the ones I've had

[Mike Spiess]

Some old freeflight props where made out of Palona wood. I think thats how you spell it. It was really hard strange grain look somewhat like popular.

[Tom Niebuhr]

Nylon gets very brittle with age. I suspect you had the oldTop Flight nylon props... The safest bet it to just buy new props.

[Keith Spriggs]

Here is a couple of pictures of the broken prop. I see it was a 10-8 instead of a 10-6 like I stated earlier. It appears that it may be made out of maple, but I am no expert on idintifing woods. I don't see any nicks on the edge and I was starting the engine with my finger.

PS Note the price

[Bob Reeves]

Glad to hear the prop missed everything vital..

One thing you need to check on thoes old engines is to be sure the wrist pin is free on the rod. I have seen several old gunked up engines ran with the wristpin frozen to the rod and the resulting runed pistons.

[Ron King]

Here is a couple of pictures of the broken prop. I see it was a 10-8 instead of a 10-6 like I stated earlier. It appears that it may be made out of maple, but I am no expert on identifying woods. I don't see any nicks on the edge and I was starting the engine with my finger.

PS Note the price

Keith,

Excellent photos. You can see the split line along the grain. Thanks.

I would be willing to bet that was the blade you were holding when you tightened the prop nut on the crankshaft. This is all conjecture on my part, but I have had a couple props split while I was tightening them up.  It's a "feel" thing and it happens.

I have a few Top Flite props here in the basement with similar prices. I don't think these are maple. Top Flite identified those with the "Super M" label.  Too bad we cannot replace them for the same price. 

Again, the important news is you are okay.

Ron
PAMPA Stunt News Safety Editor

[Keith Spriggs]

One thing you need to check on thoes old engines is to be sure the wrist pin is free on the rod. I have seen several old gunked up engines ran with the wristpin frozen to the rod and the resulting runed pistons.

Thanks for the tip

[Richard Grogan]

Thanks for the tip

Thank God you didn't get the "tip" in that picture!!


That was a close one!!  

[Steve Helmick]

I believe the old TF's were made from Gum. It got really pricey, when Black Walnut became a trendy furniture wood. Gum, properly stained, is a dead ringer for Black Walnut, so the price of Gum was soon almost as high. Steve

[Keith Spriggs]

Better get some APC's or Master Air Screw props. Don't forget to use 10-28 or 10-29 fuel in them Foxes don't run that R/C Kool-Aid.

Went down to Fox, last week, and picked some of each kind of props that you mentioned and also some 29% Castor fuel.

[Bill Little]

I still have some 25 cent Top Flite paddle blades.  They have worked fine, but I never bought any that had the grain lines running like the one in your picture that broke.  I guess seeing people breaking wooden bats in baseball made me aware of "grain" and what's not good.

I snapped a B-Y&O 10-4 in half on Aaron's OS 32, once.   The engine wasn't flooded, it was turning over fine.  I just turned it to compression and flipped.  I did not even *hit* the prop!

We all must be aware of the saftey concerns when running our engines.

[Shultzie]

MY GOOD LORDY!!! A BROKEN COLLECTOR ITEM.. "A TF 10/8?

[Phil Coopy]

We have a broken 3 blade Master Airscrew prop hanging up at the field that broke in flight. Close inspection revealed a large air bubble at the root of the blade. The resulting vibration ripped the Homelite 25cc gas burner right off the plane.  It would ahve been very dangerous if it had happened on the ground. I always emphasize to beginners never to get in line with the plane of a rotating propeller because these accidents are truly unpredictable but very possible.

Phil