posted on Aug, 17 2016 @ 09:13 AM
a reply to: Zaphod58
That's a radial engine for you. At idle they have to run rich so you get some post cylinder detonations when the exhaust gets to a point where there
is enough oxygen for the unburned fuel to detonate.
The reason for much of the vibration is the way that the radial engine is designed. There is a vibration dampening system, but, it is only effective
at a higher RPM range.
If you think a B-25 is bad, you should have been around one of the Navy's C-1A Traders. They were being phased out when I went in, but, several were
still around. One of my Chiefs had worked on them, so when one landed at NAS Jax he got called over to look at it and took me along. My first time
around a radial, scared the hell out of me until the Chief explained what was going on and why.
One thing to remember about a radial engine, they tend to throw oil when they start. It is usually in a circle that is concentric with the prop arc,
just behind it, as wide as the cylinder bank and out to about 30 feet.
Several years ago I worked at a local County airport. We had an old Howard that had been in a hanger for about 40 years. Finally a guy bought the
plane and I helped him get it ready for a ferry flight. Word of the flight got out and one of the local television reporters wanted to do a report
about it. The County was always looking for good publicity, so it was approved. The day of the flight, there were several people and several
politicians there mugging for the camera. We are just getting ready to start the engines, when I notice the Mayor of a nearby town standing in the
area that I mentioned. I warned her to move, but, I got the old "Do you know who I am?" bit. I looked at the pilot and shrugged my shoulders, he
shrugged his and gave the signal that he was starting the engine. The started turned the prop, the engine coughed and then fired up. I looked at the
Mayor and almost hurt myself choking back the laughter. She had on a pale blue pants suit, now it was pale blue with black and brown spots. She
glared at me and stormed off. It took the pilot ten minutes to compose himself enough to taxi the aircraft and take off. I asked the camera guy if
he got that and he laughed.