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  #1  
Old 02-20-2021, 10:03 PM
mfleming's Avatar
mfleming mfleming is offline
 
Join Date: Sep 2016
Location: Joseph, Oregon
Posts: 674
Default B&C Voltage Regulator Screw Security

-7 wiring in progress

Following the B&C manual for mounting the LR3D regulator, mines on the pilot side of the firewall. All the wires were ready to attach to the regulator when I noticed that the screws are very short and do not come with a lock washer. There is a sort of ridged landing pad that might act as a locking device when all is snugged down.

My question is for those who have gone before me: Did you use what B&C supplied and called it good, or did you do something different?

Here's a photo just for grins.
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RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017
Started on QB fuselage 01/2018
Sliding canopy mostly completed 10/2020
Wiring completed
Avionics harness build in progress
Donated for 2021 and so should you

Last edited by mfleming : 02-20-2021 at 10:04 PM. Reason: typo
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  #2  
Old 02-20-2021, 11:25 PM
Kiwi flyer Kiwi flyer is offline
 
Join Date: Jul 2017
Location: Pell city, al
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I used lock washers and had no problems so far. 60 hrs on plane. Hope this helps.
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  #3  
Old 02-21-2021, 07:09 AM
abuura abuura is offline
 
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1300+ hours, no problems using the supplied fittings.
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  #4  
Old 02-21-2021, 07:11 AM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
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MS35333-37 (Type A), Available from Spruce and others.

And use TE PIDG Ring Terminals for the wire terminations...
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Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
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  #5  
Old 02-21-2021, 08:17 AM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Southwest
Posts: 1,417
Default Dont understand why

I dont understand the need to use lock washers on these terminals. Lock washers keep the threads engaged during vibration when parts may “gap”. With these terminals, there is little mass to cause gapping; the terminals should stay tight under the most severe vibration.

However if the wires tend to move a little, or the threads are lubricated, then the screws can loosen. There are two other solutions: one is to stake the screw heads with ec2216, or use locktite.

It is important to secure the wires close to the terminals for many reasons.

Removing these screws to add lockwashers is fine if the screws are long enough still for full engagement of the threads and the part is outside the airplane. But if the terminal screws are short, or the part is already inside the airplane, it is fraught with problem trying to remove to add lock washers.

A way to check full thread engagement is to back out the screw until it is not screwing out anymore. Then turn the screw in. It should turn in 4 turns. Or conversely from tight should back out four turns before it is free.
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

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Last edited by PilotjohnS : 02-21-2021 at 08:37 AM.
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  #6  
Old 02-21-2021, 08:27 AM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
Posts: 350
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Any single sided fastener (if you canít torque for either side) must have a locking feature or safety installed. This screw would qualify as/need such unless you put a nut on the back side. If not specified, then it is good practice and cheap insurance.
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  #7  
Old 02-21-2021, 09:27 AM
Lars Lars is offline
 
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Location: Davis, CA
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I've worked on dozens of aircraft that had terminal strips installed for various wiring functions, B&C regulators included. I've never found one loose. I'm only one mechanic, so take that for what it's worth. The problem I've found is overtightening, leading to broken screws when I try to remove them.

Terminal strip designs, which usually included a serrated surface and/or a serrated screw, tend to be very secure. My own RV-7 also has several, and two B&C regulators. Never had a loosening problem in over 1000 hours.
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  #8  
Old 02-21-2021, 09:51 AM
vic syracuse vic syracuse is offline
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I've never seen these come loose. I don't think there is a need for a lockwasher.

Vic
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  #9  
Old 02-21-2021, 11:11 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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can't speak to issues with these screws, but I can say that lock washers don't always work in this situation. I chased an over voltage issue for several weeks until I finally found a loose connection on the alt field breaker. These breakers all had lock washers on the screws and ALL of them were loose enough to require re-tightening. The loose screw was creating resistance and lower the sensed voltage for the regulator, raising the output voltage.

Larry
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  #10  
Old 02-21-2021, 11:36 AM
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bjdecker bjdecker is offline
 
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Quote:
Originally Posted by vic syracuse View Post
I've never seen these come loose. I don't think there is a need for a lockwasher.

Vic
I put lock washers on screws that aren't held in place with a nylock nut, MS21043 nut, nut plate, or similar retention device.

Klixon 7277 CBs have split lock washers, and they are installed in the same environment -- good enough for them...
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Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
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