Since my OP last April, http://www.vansairforce.com/community/showthread.php?t=170636 I've additional info. Ideas, anyone?
The weirdness: a vibration suddenly kicks in at an IAS between 90 and 110 mph during the first of the day's take-offs. Nothing subsequent.
The Whirl Wind 74RV spinner has broken - thrown out a chunk - twice within 700 hours, and the third is showing damage. The spinner bulkhead is chafed on on only one side, and after a few hours the screws can again be snugged down because enough material has eroded away from spinner and bulkhead.
What on earth would cause an engine to break spinners!
I've heard of vernatherm, governor, pressure spring, sticky valve guide notions that seem to address the obvious link between oil and under cowl temperatures with the vibration; some sort of resonance interior to the engine that excites the prop/spinner combo. But, my goodness, all seem like a stretch. My gut still says engine vibration isolators are not doing their job (They are the Lord mounts with the secondary internal cone limiting start-up motion.)
A 200RV prop Whirl Wind loaned to me hasn't altered the vibration phenomemon. Curiously, Whirl Wind has stepped away from stroker 360s (and anything else with greater than 9.6:1). From their website: "(I)0-370/375 NOT SUPPORTED"
So much would seem to implicate the airframe, but I've dismissed that mainly over the temperature issue - first takeoff only, and sometimes not at all if temps are already elevated - and magnitude is linked to power.
Any further ideas, brain trust?
John Siebold
Boise, ID
The weirdness: a vibration suddenly kicks in at an IAS between 90 and 110 mph during the first of the day's take-offs. Nothing subsequent.
The Whirl Wind 74RV spinner has broken - thrown out a chunk - twice within 700 hours, and the third is showing damage. The spinner bulkhead is chafed on on only one side, and after a few hours the screws can again be snugged down because enough material has eroded away from spinner and bulkhead.
What on earth would cause an engine to break spinners!
I've heard of vernatherm, governor, pressure spring, sticky valve guide notions that seem to address the obvious link between oil and under cowl temperatures with the vibration; some sort of resonance interior to the engine that excites the prop/spinner combo. But, my goodness, all seem like a stretch. My gut still says engine vibration isolators are not doing their job (They are the Lord mounts with the secondary internal cone limiting start-up motion.)
A 200RV prop Whirl Wind loaned to me hasn't altered the vibration phenomemon. Curiously, Whirl Wind has stepped away from stroker 360s (and anything else with greater than 9.6:1). From their website: "(I)0-370/375 NOT SUPPORTED"
So much would seem to implicate the airframe, but I've dismissed that mainly over the temperature issue - first takeoff only, and sometimes not at all if temps are already elevated - and magnitude is linked to power.
Any further ideas, brain trust?
John Siebold
Boise, ID
Last edited: