ORIGINAL: tsyssa

18x8 would not have caused the key to shear. You are correct. No prop size should cause the key to shear.

The only thing that should cause the key to shear would be a hard prop strike. I say hard as I have had a few during testing that broke props and the key never sheared.

We will find out what it is.

There are only a few things that you should have to do with your engine. Set the needles for your air density is one. Fly it is the second.

ORIGINAL: mglavin

Rob,

It's plausible the problem (broken crank/hub key) is simply related to needle settings and the results thereof; pinging-detonation-knocking. Your video depicts erratic engine operation IMO, possibly you were a might lean on the needle(s). The engine is very crisp indicating same, again IMO and remeber the engine can and will run lean at partial throttle settings not just WOT. And it matters little how cool the engine runs on the ground, as the prop advancing or screwing through the air is a whole other consideration.

What is or was your procedure for properly setting the needles?

ORIGINAL: mglavin

Rob,

Oil residue or spent hydro-carbons and fuel-oil byproducts of a two-stroke in of itself does not tell us the engine was running lean or not, there are many variables.

Do you info on the recommended fuel?

ORIGINAL: Scooterpilot

Another great day here and five more flights on the motor. Tork rolls are between 1/3 and 1/2 throttle. Most of the flights are under 1/2 throttle. Finally, the motor has burned a gallon. It takes a long time as the motor just sips the fuel. I have the timer set for 10 minutes. The timer does not go on until the model is in the air. So, start, warm up, run up, idle, taxi out, turn on timer and then fly until the timer goes off. Do a couple of patterns and then land. I'm just below 1/2 a tank and it's a 12 oz tank.

For starting, I close the choke, rock the blade 5 times, open the choke, turn on the ignition and it fires. Very consistent starting motor. Unlike my DA's 50 where I close the choke, start the engine with the choke on, engine starts then motor dies; then, open the choke and then start the motor. This is one less item on the start up list.

Motor is well worth the cost compared to the overseas motors. Like the old saying, ''You get what you pay for.''

Regards,

Chuck

ORIGINAL: mglavin

TSP provided a manual, Thanks.

Manual suggests unleaded 87-89 octane fuel. Rob noted he used 87 octane which is more likely than not the better choice for the thinner air at 2100' ASL.

FWIW:
The resulting forces of an engine that ignites a fuel charge prematurely will try to turn the crankshaft in the reverse direction, stress on rotating components is massive, hence the broken crank/hub key. So Detonation or Pre-ignition can potentially cause and affect the broken crank/hub key phenomenon realized herein.

One might ponder:

Improper ignition timing, fuel-air mixture and/or low octane fuel can cause detonation. That said; rich needle settings, early ignition timing and low octane fuel may lead to pre-ignition resultant behavior. Other factors cause pre-ignition too, however they are unlikely with a new engine me thinks.

Pre-ignition and Detonation are two distinctively different occurrences and one can lead to the other. Again the two are completely different and abnormal phenomenon.

Detonation is the spontaneous combustion of end-gasses in the chamber and it always occurs after normal combustion is initiated by the spark plug.

End gasses = remaining fuel/air mixture in the combustion chamber after primary combustion occurs

Pre-ignition is the ignition of the mixture prior to the spark plug firing. Anything that causes the fuel-air mixture in the chamber to ignite prior to the ignition pulse is classified as pre-ignition.

ORIGINAL: Joystick TX

MsgtRob,
I stand by my advice to ground the plug on the engine when testing it to see if it has a spark. Not grounding the plug may be okay for your ignition system but not all ignition modules are built the same. This is a general forum, at least as far as ignition modules are concerned, and the advice given should be general in nature and not cause problems for others.

Here is a quote from an ignition module manufacturer: *Make sure the engine has spark. Test the spark plug by removing it and hold it firmly to the engine head (thus grounding it) and turn the propeller to see the spark. NOTE: the plug MUST be grounded or it WILL blow the ignition pickup sensor.

Like my hero said: Do you feel lucky …?

It is not just a matter of will it work; it is a matter of how it was designed to work. The plug may fire without being grounded to the engine, but there also may be degradation of the components, that you aren’t aware of, due to the high voltages developed inside the module. As a designer, I never depended upon an RFI/EMI shield, such as those found on many spark plug wires, to carry return current, I always used a ground wire or structure.

My 2 cents: Sheared keys on two out of about 500 engines this early in the production cycle is significant. Since most of the SAP-180 users have had previous experience with gas engines, I suspect the ball is in Todd’s court.

Hopefully, Todd can find the root-cause of the key shearing problem pretty quickly. It could be as simple as the key material being too soft, or not per the original spec., or the factory timing was not set correctly. Stuff happens. See Murphy.

I know the key can be replaced by some engine owners or they may know someone who can, but right now Todd needs to see the problem to help with the solution. As painful as it will be, if I shear a key, my engine will be sent back for analysis and repair. Murphy stay away from me.

Hope Todd can do a quick turn on your engine!

ORIGINAL: mglavin

TSP provided a manual, Thanks.

Manual suggests unleaded 87-89 octane fuel. Rob noted he used 87 octane which is more likely than not the better choice for the thinner air at 2100' ASL.

FWIW:
The resulting forces of an engine that ignites a fuel charge prematurely will try to turn the crankshaft in the reverse direction, stress on rotating components is massive, hence the broken crank/hub key. So Detonation or Pre-ignition can potentially cause and affect the broken crank/hub key phenomenon realized herein.

One might ponder:

Improper ignition timing, fuel-air mixture and/or low octane fuel can cause detonation. That said; rich needle settings, early ignition timing and low octane fuel may lead to pre-ignition resultant behavior. Other factors cause pre-ignition too, however they are unlikely with a new engine me thinks.

Pre-ignition and Detonation are two distinctively different occurrences and one can lead to the other. Again the two are completely different and abnormal phenomenon.

Detonation is the spontaneous combustion of end-gasses in the chamber and it always occurs after normal combustion is initiated by the spark plug.

End gasses = remaining fuel/air mixture in the combustion chamber after primary combustion occurs

Pre-ignition is the ignition of the mixture prior to the spark plug firing. Anything that causes the fuel-air mixture in the chamber to ignite prior to the ignition pulse is classified as pre-ignition.