fytrjok

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I just wanted to alert anyone using the RCG 26 gas engine to a failure I experienced yesterday at the field. The engine is mounted in a CMP 109 and I use 30% dino oil as the engine has less than a dozen flights on it. I've been running a 17x8 prop at 150-200rpm below peak. I was standing behind the aircraft and after letting her warm up for a bit began to slowly advance the throttle. at about 1/3 throttle the crank broke and the prop/spinner assy flew forward about 20 feet. Luckily no one was in its way so there were no injuries. This engine has only a dozen or so runs on it so I regard it as "new". The crank failed right where the threads begin. I know this was a cheap engine but really? Really? Buy cheap, buy twice! And by the way, if you run one of these, make sure to do any run-ups well away from anyone![:@]

irocbsa

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Is this the RCG 26 from Hobby King?

http://www.hobbyking.com/hobbyking/s...HP_1_95kw.html

Or is is the new beam mount RCGF from BP Hobbies?

http://www.bphobbies.com/view.asp?id...0&pid=H1564641

fytrjok

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Hobby King.

4*60

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30% oil might have something to do with it! 

karolh

That explains it

earlwb

Was that the prop stub shaft that broke off or the crankshaft portion under the drive washer?
That location where the threads end is a common spot where  stress risers can occur. Sometimes improperly hardened crankshafts can be at fault. But the prop stud could have a defect in where they drilled the inside threaded hole to deep, weakening the stub shaft.

But overtighening a propeller could lead to the failure as well, as it stretches and stresses the metal right there at that spot. I have seen people break off the end of a crankshaft before on different brands of engines, not just gas but glow too, when overtightening the prop nut. Sometimes it snaps off on the ground and in other cases it fails in the air or during a engine runup on the ground. When a engine has the extra prop locking screws, they should use them and go more gentle on the main prop nut to avoid such a situation.

irocbsa

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There is another member on here that had an identical failure. A quick search might find that thread.

RCVFR

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I had an identical failure, and mine occurred in flight. MIne was several years ago, an RCGF 26 bought from a reputable US dealer with good warranty service, but it was past warranty when this happened. It's not the dealer/distributor or the oil or anything else other than a shabby product. You don't always get what you pay for. I paid for several shipping charges for warranty service on the failed ignition, problem carb and even sent the engine back for examination and evaluation, and of course the repair of the failed prop driver. I replaced it with a Zenoah 20, which had a higher initial price than the RCGF, but I spent more $ on the "cheap" engine.

fytrjok

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The failed portion is at the beginning of the threads on the end of the crank. The drive extension fits over the crank and is held in place by a key. The actual prop shaft threads onto the end of the crank. I'll search for that other thread. Thanks!

bcchi

Idon't think it's 30% oil but probably 30 to 1 oil.
BCCHI

1320Fastback

I was looking at the 16cc and 20cc versions of this engine for my NOS Hangar 9 Cub.
I was more concerned about weight but believe I read that they use a similar drilled shaft.

I went with a low time used Saito .62 that actually cost a little more but now I can sleep.

irocbsa

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This thread highlights yet another reason to avoid the garbage RCG/RCGF 26 like the plague. There is a reason for the $140 price tag. Barely functional carburetor, poor materials, junk spark plug..... The list keeps growing.

fytrjok

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Here's a couple pics of the point of failure. You can see the flaw in the casting. Reminds me of the defect in the fan hub of that DC10 that crashed in Sioux City years ago.