Sun Aug 16 2020

Seatbelt bushings and fuel vent line fittings

Well, I've not come up with a replacement fillister head screw for my lathe chuck. McMaster has them, but it's impossible to get something shipped from them for less than ~$6 in shipping. I'm not going to pay $6 shipping for a 25 cent screw. So, I decided to just modify another style of screw. On the right is an unmodified screw. In the middle is the modified one. And, of course, the original, bent screw is on the left.

I used some sharpie and the tips of my calipers to mark the parting line.

Here are all the finished bushings. The two furthest left are .330 long. They are used for the crotch strap attachment. All the rest are .200 long.

My friend, Shane, from Ohio was nice enough to machine these little airfoils for making the new vent line fittings. They look awesome and are going to save me a ton of work. He was nice enough to send me an extra set in case I screwed up on the first ones. Thanks, Shane!

While I didn't do this on the last set of vent line fittings I fabricated, I wanted to include a tiny hole on the back of the fitting to prevent the tanks from experiencing suction if ice or debris were to block the main port of these vent fittings. This approach is recommended by an old NACA document I read years ago. So, I carefully measured, center punched, and drilled a 1/16" hole through what will be the back side of these fittings.

I turned the first fitting on the lathe. It'll be a .002 press fit in the reamed hole of the little airfoils. Unfortunately, you can see that I drilled my little hole in the wrong spot. That hole should have only been halfway machined away. Apparently when I laid it out .093 from the side surface of the hex part of the fitting, I measured from the wrong side surface. Arg. :-( No big deal...I can compensate for this little screw up.

Reaming the center holes to .250 diameter. Shane's shop doesn't have imperial sized tooling, so he drilled these slightly undersized so I could ream them.

OK, here's my fix for the incorrectly positioned little hole. I just used the cutting disc to cut a little passage for air to flow into that little hole should the main port become blocked.

I used my press to press the fittings into the airfoils.

Then it was time to liberate these little guys from the stock block they were machined from. A few minutes with a hacksaw...

Ready for sanding the ends and polishing. I'll do that tomorrow. By this time in the day it was 107 F outside, and the garage was probably a few degrees warmer. Time to quit for the day.