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Expensive
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That's the beauty of building an RV. Everyone gets to choose what to buy and install. Have fun. Buy reliable parts from respected vendors, and be happy with your selection. It's your airplane. You only have to please yourself. |
I heard 'lectric Bob speak at Oshkosh a few year ago about exactly this. He advocated using inexpensive, off the shelf parts like B&C sells and then replacing the switches after 10-15 years. For $100, you can replace all the switches in a typical homebuilt periodically and achieve system reliability that likely exceeds that of expensive mil-spec switches.
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Use whatever you want, quality stuff usually costs more, but to me (and most of my customers will agree) it's worth it. 8 years, 1300+ hrs, 100% Dispatch reliability. |
Lectric Bob..... also explained why push on connectors were a superior electric connection.
I purchased all of my switches from Granger rated for AC. I used these switches in my propane truck. This switch was cycled over 40 times a day, five days a week for fifteen years. And NOT one failure. This was an AC rated switch on a DC load. Part # 4X849 about $6 each. |
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I look at switches the same way as any instrumentation - it needs to work. If it doesn't matter if it works or not, you probably don't need it and should consider getting rid of it. TODR |
Getting back to the original question:
Both push on and screw on terminals work fine and do not often fail. I use both on my aircraft. Both work!. When do I use screw on .. when I have a linear group of switches or circuit brakers that are all tied together by a copper bus. You drill holes, then use screws though the bus (with lock washers). If you use pushons you will have many more connections that could fail.Also, not as clean looking. Just my 0.02 cents. |
Forces and spec sheets....
The 1/4 inch Faston PIDG terminals are great, but some care needs to be taken installing and removing the terminal from tabs.
For 22g wire the minimum commercial crimp "pull out" force is 8 pounds, while the maximum "pull the terminal off the tab" force can be as high as 18 pounds for the first use. So... don't pull on the wire to remove a terminal from a tab....:) Numbers here - http://www1.futureelectronics.com/do...CS/42067-1.pdf |
Component reliability, system reliability, and dispatch reliability
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All switches can fail. Not necessarily at the same rate, nor for the same reasons, but they all can and will eventually fail (though most will outlive your airplane). System reliability is a function of the reliability of the individual components under their respective operating conditions, but also the design of the system to prevent single component failures from taking down the system or large portions thereof. That's a whole topic in itself that I won't get into here. But the point I wanted to make is the following. Even if you assume for the sake of discussion that the commercial grade switches from B&C are equally as reliable as the milspec switches (doubtful, but assume it for the sake of discussion), the milspec switches still have the advantage of ubiquity as I described above (post #7). Walt hit the nail on the head in referencing the objective of achieving good dispatch reliability. Part of that is reducing the failure rate by various means, including use of good quality of components. But another less obvious part is ensuring serviceability and minimizing down time when failures do occur, both at home and away, both at present time and in the future for the lifetime of the airplane. When you experience a failure 10 years from now and 1000 miles away from home (away from your personal stash of spare parts), the local mechanic or avionics shop is likely to have the standard milspec switches on hand, not the B&C flavor of the day from ten years prior. That's when that extra $100 spent upfront to use milspec switches in your panel (a drop in the bucket on a ~$100K airplane I might add) will have more than paid for itself, in getting you back on your way with minimum delay. P.S. There was recently a thread discussing standard external power connectors versus Piper-style connectors and other possibly effective but non-standard contrivances, where I advocated using the standard connector for essentially the same reasons I'm advocating the milspec switches here. Dispatch reliability. When the s*** hits the fan at the most inconvenient time and place, consider what resources will be most likely available to get you back on your way. |
Thank you for all your inputs which I do value?. In the interest of fairness, I plan to use half screw on and half Faston. I also intend to complete the rest of my airplane without priming any more.
I?m now schizophrenic and so am I |
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I pulled about 30 of them off the forest of tabs by pulling on the wire. Not a single one of them pulled the wire out of the connector. Some had to be pulled very hard to get em to come off. Sold me on good connectors, good crimp tools and Faston connections. |
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