Fusible Link Demonstration

DanH · #1 03-20-2017, 07:37 AM

Well, sometimes it happens...get a little clumsy with a tool and short a power lead to ground. In this case the wire was protected at the source with a fusible link, which did its duty.

This one is an 18 ga wire, so the link is the usual 4 sizes smaller, i.e. 22 ga. The fiberglass tube sheath is from a B&C kit. I make mine with bare crimp terminals, so the assembly is more compact than one made with red AMP splices.

The tube shows only a small burn mark...

...but the trusty Fluke says it's open, so let's do some surgery for the curious. The crimp splices add mass to the ends of the 22 ga, so as we might predict, it burns open right in the middle:

rv7charlie · #2 03-20-2017, 08:55 AM

Thanks for sharing. I'm using homemade links in a few places in my project, as well.

The 'kits' of fiberglass sheathing are a bit pricey for my taste, so I tried a different technique. Bought a batch of various sized silicone tubing on ebay, & used that instead of the silicone impregnated fiberglass. I did run a test by making a test sample & 'blowing' it using a 12V starting battery. The tubing I used is a bit thicker than the fiberglass, and I assume that's why the only effect was staining by the vaporized wire. No damage to the tubing at all.

I simply soldered my links inline, because of the (hopefully) rare need to replace, and I felt that reliability would be enhanced (several of my past lives involved making reliable solder joints on a daily basis).

Charlie

ERushing · #3 03-20-2017, 09:58 AM

Any places to look for hints on building fusible links?

MarkW · #4 03-20-2017, 10:06 AM

http://www.aeroelectric.com/articles.../fuselink.html

If you haven't yet the AeroElecric Connection by Bob K. is an excellent source for all things electric.

rv7charlie · #5 03-20-2017, 10:08 AM

Get the aeroelectric connection book. You can buy a printed copy, or download the pdf for free.
http://www.aeroelectric.com/Downloads.html

If you're not an electrical engineer (or even if you are), you're doing yourself a disservice if you're wiring a plane without this document as reference.

You'd also be doing yourself a favor by signing up for the aeroelectric mailing list. To be blunt, peer review there is of significantly higher quality *on a consistent basis* there, than here. There are some really smart people here, but they might not see every post related to electrical issues. Not much gets past the group on that list, primarily because Bob Nuckolls is the 'graybeard' looking over everyone's shoulders.

Charlie