Oil Pump Prime...Revisited...

[6643]

So is 5 sec or so normal for our little motors, or am I at the beginning of an issue?

Yes, normal. The connection for the oil pressure gauge is at the far end of the oil galleries.

Welding magnesium: what could possibly go wrong?

[2066]

John wrote: "Welding magnesium: what could possibly go wrong? "

Amen! Both the welding and the machining bring all sorts of risks...no wonder there aren't a lot of shops jumping at the "opportunity"? Glad this one can/will & hoping it works out (for them and for me ). Mac

[2066]

RE starting without pressure, most of us cringe if (when?) we don't see pressure within a few seconds. I have no knowledge or opinion if this (below) is fact, but saw this related comment regarding "what happens" if no oil is being pumped for "minutes" after start-up:

"cessna150pilot questions: ↑I'm not about to run it for 3 minutes without oil pressure, does this not cause damage ?
'Expert'(??) answer: Not really, not so long as you aren't making significant power/heat. The bearings self lubricate against polished steel as long as the temperature stays below the critical temp for the bearings and they start to smear. The main purpose of oil is carry away heat. At idle power-900rpm, there really isn't that much heat being produced and your risk of getting a good bearing to go bad are pretty minimal.

[6643]

The Continental Service manual says max 30 seconds on a pre-oiled engine, first start after overhaul. The Cessna 120/140 operation Manual says the same thing for any start. I think 30 seconds is reasonable, and it will seem like an awful long time if you are waiting for the gauge to move!

[2066]

The Continental Service manual says max 30 seconds on a pre-oiled engine, first start after overhaul. The Cessna 120/140 operation Manual says the same thing for any start. I think 30 seconds is reasonable, and it will seem like an awful long time if you are waiting for the gauge to move!

Yep -- plenty of time to sweat, thump on gauge, "hope", increase heart rate...then "stop engine and investigate" . And, I do believe Cessna's additional ops manual warning that "Lack of oil pressure may cause serious engine damage". Mac

[6597]

Maybe not as hard as we thought to weld magnesium, just a few things to pay attention to...

https://www.youtube.com/watch?v=tausy8soPzU

https://www.youtube.com/watch?v=weqTWwaaL0g

[a64pilot]

The Continental Service manual says max 30 seconds on a pre-oiled engine, first start after overhaul. The Cessna 120/140 operation Manual says the same thing for any start. I think 30 seconds is reasonable, and it will seem like an awful long time if you are waiting for the gauge to move!

I think a lot of that may come from back in the days of single weight oil, 40W in winter may take quite awhile to begin to flow?

[2066]

Maybe not as hard as we thought to weld magnesium, just a few things to pay attention to...

https://www.youtube.com/watch?v=tausy8soPzU

https://www.youtube.com/watch?v=weqTWwaaL0g

Good (...reassuring) videos -- thanks for the links, Dave! The unique fire hazard from mag debris is a risk than can be managed, no doubt. It sure seems that the advent & perfecting of TIG in the hands of true experts makes "repair" & return to service practical. With my own "expertise" very limited to welding 4130 with oxy-acetylene I'm amazed at what some true experienced professionals can accomplish with different metals. (The first few seconds of the #2 video showed an ad with 'Jake from State Farm' -- I thought briefly that he was going to be the welder .) Mac

[6643]

40W in winter may take quite awhile to begin to flow?

It's not as bad as it sounds. Aviation W40 is equivalent to SAE 20W. My rule of thumb is to never try a start without preheat if the engine core temp in Fahrenheit is less than the SAE W-rating of the oil. (Or, were you referring to W80, which is in fact 40W). The Operations Manual calls for SAE40 only above 70 degrees F.

[a64pilot]

I think the temp break point is 40f, but no matter, back in the day you dumped the oil if it was cold and heated the oil up and put it back in and started.
Some of course used oil dilution, I’m not sure when pre-heating started.
But I never intend to live in the cold, much less fly in it.