Headlight switch problem- 1978 280z

[SteveJ]

3 minutes ago, Zed Head said:

For a one off an Exacto knife and a pierce of plastic rod would probably do it.  It's not really a high precision piece.  Look at how long it lasted while it was melting.

p.s. if you add a relay you don't have to worry as much about the heat.  Except for the running lights right next to it.  I also ended up putting a relay on my running light circuit.  That was tougher though because Nissan buried that wire way up under the dash.  My original problem was the solder joints breaking.

Easy solution for the parking lights - LEDs all around (gauges, front markers, rear markers, and side markers)! It might even keep the connector at the steering wheel from melting.

[Captain Obvious]

gotham22,  If you want to send me a good part to use as a guide, I'll see if I can make a replacement?

And no... I'm not going into the replacement headlight nubbin business unless someone presents me with a credible business case.

[gotham22]

@Captain Obvious Ha! Nubbin business! I will message you directly. I am also talking to a machine shop today to see what they can do

 

[SteveJ]

I should get some acrylic rods to experiment with tomorrow to see if I can develop some techniques with what I have on hand.

I know that I encounter melted nubs when I help people with the switches.

[Zed Head]

Acrylic will probably abrade and wear pretty quickly.  Nylon and polyacetal (Delrin) have what's known as "natural lubricity".  And acrylics are more difficult to machine, they tend to be brittle.

Since the part is plastic it will machine pretty easily compared to metal.  A lathe will offer accuracy and precision, but, for what it is, a drill press and some handiwork with sharp objects should get the job done easily.

I guess I'm saying don't make it overly complicated.  It's not an engine part.

Here's an in-depth article about plastics and friction.   If you want to test the original material you can stick a red hot wire in it, or touch it with a torch flame, and take a whiff of the vapors.  If it smells like burnt hair it's nylon.  If it smells like formaldehyde it's polyacetal.  The smell test is an actual test method from the past.  Probably not allowed anymore though.  Odds are it's nylon.

https://www.machinedesign.com/archive/article/21816534/plastics-that-dont-wear-out-their-welcome

"

The most important semicrystalline polymers for friction and wear include:

Acetal (POM) which is rigid and strong with good creep resistance. It has a low coefficient of friction, remains stable at high temperatures, and offers good resistance to hot water.

Nylon (PA) absorbs more moisture than most polymers, affecting processability, dimensional stability, and physical properties. However, nylon's impact strength and general energy absorbing qualities improve as it absorbs moisture. Nylons also have a low coefficient of friction, good electrical properties, and resist chemicals.

High-temperature nylon (HTN) and polyphthalamide (PPA) extend the nylon family through improved temperature resistance and lower moisture absorption. They ....

Edited August 18, 2022 by Zed Head
apostrophes, commas and periods

[SteveJ]

5 minutes ago, Zed Head said:

Acrylic will probably abrade and wear pretty quickly.  Nylon and polyacetal (Delrin) have what's known as "natural lubricity".  And acrylics are more difficult to machine, they tend to be brittle.

Since the part is plastic it will machine pretty easily compared to metal.  A lathe will offer accuracy and precision, but, for what it is, a drill press and some handiwork with sharp objects should get the job done easily.

I guess I'm saying don't make it overly complicated.  It's not an engine part.

I have some ABS rod on order, too. The first materials are just to get my technique going, such as drilling out the rod for the spring.

As for the lathe, I was planning on using the drill press.   It's the cutting tools that I need to figure out.

[Captain Obvious]

12 hours ago, gotham22 said:

Ha! Nubbin business! I will message you directly. 

Got your message and sent one back.

[Captain Obvious]

9 hours ago, SteveJ said:

I have some ABS rod on order, too.

I would not consider either ABS or acrylic to be a good choice in the long term. Certainly usable for proof of concept and testing a procedure. Careful with the acrylic as it can be brittle and shatter if you push it too hard. Don't hurt yourself and wear eye protection!   

This could be done in a drill press, but it's really not the tool for the job. For the spring hole, you want the hole in the center and it probably has a flat bottom. The rounded tip is actually the easy part here... Just use a file while the part is spinning. Heck, since I don't consider it to be a high precision job, that's what I would do on the lathe. Use a file and eyeball the radius.

[cgsheen1]

The "pin" is electrically isolated, so it doesn't necessarily need to be plastic. Brass?

[gotham22]

I just sent over pics and dimensions to a machine shop.  Do you think brass is the best metal to use?  

For reference here are measurements.

 

[SteveJ]

Brass certainly won't be brittle, and it won't melt easily. I don't know about friction, though.

[Zed Head]

I see a brass tube with a plastic knob inserted.  That is an injection molded part.  Those thin walls will be difficult to replicate.

The cost of machining is in the tolerances, not the dimensions.