| Hi Colyn,
It is almost always(almost?) possible to find a more expensive better sounding component when talking relays and solenoids as well as most electronics.
I am not aware of an unreasonable failure rate with the Lancair recommended stuff but have obviously not been around the Lancair community as long as others. The problem with condemning a component without knowing all the factors leading up to the failure is that introducing a different component may cloud the real issue or cause a new one. If a particular aircraft has failed a Lancair suggested relay, covering up the issue with a more robust relay may lead to a more serious failure later... or maybe not. Getting the highest reliability can only be accomplished by getting to the real root cause of each failure.
If there has been a consistent pattern of failure of the Lancair master solenoids activating the gear pump then I am all in finding the cause and a different or added component which has been proven in at least twenty or so installations throughly tested across the four seasons. If there is no failure pattern then putting in a seemingly better part is lose-breakeven poker.
My vote is to keep the fleet as uniform as possible so real reliability issues can be isolated. If there is no consistent component usage, identifying real problems and achieving real quality will be impossible. Dreaming up fancy designs is fun. Real reliability is very hard to achieve and much less/no fun. We Americans are an innovative lot. That is why Japan kicked our butt in the 70's and 80's.
Sorry to be a quality zealot but I was part of the problem back then and learned the hard way along with everyone else.
Jack Morgan On Nov 30, 2013, at 6:00 AM, Lancair Mailing List wrote: Subject: Re: [LML] Motor locked current
Date: November 29, 2013 9:46:41 PM EST
Jack, I was with you until you got to "The solenoid Lancair recommends".See the reply to Giff I just posted where Bob Nuckolls argues to the contrary. On Nov 29, 2013, at 6:53 PM, Jack Morgan wrote: Hi John,
A good rule of thumb on dc motors is 4 to 1 so your measurement seems good. Your readings are also consistent with the 35 amp breaker which I understand is typical for the pump.
Inductive loads like the motor are easiest to turn on for relays since the contacts are made before the current reaches the locked value. Incandescent lamps are the worst case turn on load..... 10 to 1 is the rule of thumb (no kidding) for the inrush into a cold lamp. With only the inductance of the connecting wires the relay really sees an inrush while it is making contact in lamp circuits.
If a normally sized relay were to break with the pump rotor locked it would be highly stressed, maybe even fail. Most designers rely on the breaker to trip to protect the wiring, motor, and relay and ignore the unlikely possibility of the relay being turned off during the short time it takes the breaker to trip with a locked motor. The solenoid Lancair recommends is capable of surviving turning off the starter for awhile so won't be damaged in any case. Nothing like belt and suspenders.
Jack Morgan
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