Die, a rheostat

Good god, that sender tried it's damnedest to recover.  That little guy and I got really close during it's last days, and I'm always going to try to remember the things I learned while working with it.

For instance, in my efforts to repair the wiper arm, I found myself having to try to build an entirely new arm.  The original one work hardened and then broke very quickly (it'd actually be more accurate to say that it caught on fire in spots where it was more fatigued than I thought).   Not too much of a surprise, since it's a really thin brass strip.  The part is fine for the electrical functions it's supposed to perform, but the qualities that make it a good electronic component makes it a weak mechanical component after 40 years of service have had their chance to show weak points.

Regardless, while trying to figure out what to make the replacement arm from, I thought about the roles assigned to that little brass strip.  First and foremost, it's a rheostat wiper contact.  Further, it's from the path of conductance from the contact to ground.  The mechanical aspects of the part are equally simple: act as arm for wiper contact and conductor that rotates across the span of the resistor strip, and do duties as a spring that keeps tension on the float arm and rheostat contact point.  I had a ton of different materials that would do those jobs.  Hell, sheet steel would work just fine.  Thing is, I noticed a pretty significant difference in wear of the wiper an the resistance wire when I first opened the sender pod - the wiper was a worn down nub.  The wires were pulled out of place from getting snagged, but were still in good shape as far as abrasive wear is concerned.

Thinking about it some led me to believe that the wiper was intended to be the sacrificial component, based mostly on the kind of material used.  I don't really keep brass strips on hand, at least not that thin.  After a few minutes, I pulled out an old electric choke spring and snipped off a couple inches of that.

Since it's a bimetallic strip, I checked both sides with the meter and got a resistance read of about 5 Ohms/in from one side, 0 on the other.  I wondered how far the conductive side could get worn before the metal with the higher resistance began to take over, so started hitting the resistor side with emory cloth.  I was pretty surprised to find out the resistance side was only about as thick as the enamel insulation on magnet wire.  Scrubbed it off, got 0 Ohms on both sides, as well as with my meter probes contacting opposite surfaces.

Popped a couple holes for the float arm in the strip, shaped it, rolled it over into the spring "U", and set that aside to focus on the other areas needing attention.  That brings me to the next thing I learned:

I learned that, at some point, I finally figured out how the hell to braze things.  This is an extension brazed to the pickup tube to compensate for the reach lost when the sock crumbled. Should work just fine.

I also learned that I'm going to have to buy an aftermarket sender and graft it on the original pickup.  Once the pickup was brazed, I set out to re-wind the resistor.

I think I did an alright job at wrapping wire semi-evenly, but I did a piss poor job of winding a functional electrical component.  I tested it with the meter and got a few bad values at the halfway-ish point, which was something I could deal with.  I want happy that the resistance would read as high as 219 Ohms near the 80% point, but the next and subsequent winds all read open.  Combining those details with the kinks and bends in the wire, I figured that I hadn't really improved the overall condition or longevity of the sender.

Aside from that, I finished up some brackets, and have been doing some big things in exhaust town.  We'll see more about that soon.  I also got the trans lines to damn-near levels of finished.  Just need to flare a line and they're finally, FINALLY taken care of.  I'll share some details and an interesting discovery from that after the last couple things are done.