air-madness

Prior to writing this new thread/post I was flying at our local club. Well, my two year old Megatech/Tower/GMS/Leo .46 has just bit the dust. I was doing a low pass when I heard the...pop...bang...click....click....click...... Ultimately, this is what happens when the connecting rod fails. This is a more serious example.

bluestratos

I had a 70 OS 4 stroke lose a connecting rod and blew the cylinder head off, taking with it the crank, prop and half of the cowl. The plane was immediately tail heavy but I managed to land it as it roller coastered to the runway. I timed the high-low osculations just right and set it down. The engine had about 3 hours total run time, never found the parts to do a post mortum.

Randy

Mr67Stang

You rock! I only wish I could have been there to hear that thing detonate. Do you think there where any contributing factors to the failure, ie. lean run, rich run, felt funny starting up today???? TEACH us.

air-madness

Well, I had it dialed in as I normally would - the appropiate way. Upon inspection after the incident (oh, I did land the plane without incident; the engine remained together except for a piece approx 1/2" x 1/2" on the side of the case) I noticed that the little hole on the bottom of the connecting rod was not alligned with the hole in the bronze bushing. I theorize that the bottom end was not getting lubed properly which led to overheating, then, which led to component failure. Basically, the rod got so hot that the temp exceeded what the metal was capable of handling. The rod bottm actually looks melted really.

When I took a look at the engine directly after landing there were gaping cracks all over it. When I unbolted the engine it literally fell to pieces! I did get this on video. I can try to post it, which will require editing first due to the nature of my words. All in good fun, not anger.

daveopam

My Feedback: (9)

This is the crash & "REBUILD" forum. So get out the JB Weld.

David

jetmech05

Hmmmm when I was running trucks I bought a megatech .16, failed the same way.
The only other engine failure I've seen was a helo driver running too lean. Actually blew a hole in the piston the diameter of the glow plug.

rcdivot

Buy some CA glue.

Geistware

My Feedback: (16)

I would say the engine was run slightly lean.
I would run your engines richer in the future.
THis is just my opinion.

air-madness

Nope, wasn't too lean at all. I actually diagnosed the problem: the bottom bronze bearing oil hole on the rod was out of alighment with the oil hole in the rod (the bearing had slipped). This led to failure directly above the hole itself (it seperated at this location). I have many, many engines that I have tried to destroy, both plane and car, but have never had this problem arise -- ever. Actually, I have a Tower brand (exact same engine as one pictured above, just a different name) that I ran a mix of 40:1 oil/gas mix through (with added nitro for ignition timing) to see what would happen. You know what? Nothing at all happened, it ran very well. I did this to experiment for a buddy and to see about other alternatives for fuel.

For you guys with the Megatech M.46: Tower Hobbies piston and sleeve will work (exact same thing); connecting rod; crank (the crank will work, but is designed exactly like the GMS brand); carb fits as original, etc, etc.

Hobbico brand will also swap parts.

I contacted the manufacturer (Leo Engines LTD, China (family affiliate of Thunder Tiger) and they specifically stated to me, via e-mail, what engines they make and what will work on what.

jetmech05

Nope Geistware. Not this time, now I wasnt there, but when my 1.6 failed I wasnt too lean
A catostrophic engine failure doesnt always happen cause of the mixture. Imagine the forces involved when the connecting rod let go.