Tue Aug 11 2020

Roll forming LED joggle strip and seat belt bushings

This morning, I made a couple side plates for the roll former to better guide the strip through the roll former.

Here's how they fit.

While cutting a strip of material to run through the roll former, I thought I would take a photo and make mention of how to use snips to yield, a nice, flat part with clean edges. There are two fundamental tips to get this result:

  1. When cutting your part out of the stock sheet, it's important to make your first cut about 3/8" away from your finished line. It's almost inevitable that you'll get some edge deformation on this first cut, and you want to be sure that is far enough away from the finished part boundary that you can cut it away.
  2. Make a second cut about 1/8 or 3/16 away from the finished line. The reason for this is to leave only a thin strip of material to cut away on your final cut. You want to leave enough that you don't have to worry about the edge rolling over on the final cut, but narrow enough that all the deformation from the final cut goes into the scrap you're cutting away, rather than your finished piece.
  3. When you make the final cut (right on your line), be sure that whichever blade is over (or under) your part is held flat to the surface of the finished part. This will protect your part from getting deformed. Of course, the other blade will be at quite an angle to the bit you're cutting away, and that will result in a nice, curl as shown here.
  4. BONUS: get a good pair of snips. The offset Wiss snips that I use frequently are good, but they have little serrations on the blades that get transferred to the edge of the part. I like these Robin snips. They are of the bypass variety, but but have no serrations. Also, the blades are longer than the Wiss snips.

After cutting that strip of .025 thick material, I ran it through the roll former. I was able to achieve the desired offset, but because the springback is more, I had to clamp the rollers tightly enough that the strip contacted the axels causing a bit of reverse bend. I didn't care for that, so decided to revert to .032 thick material.

Here's the .032 joggled strip, all trimmed up. You can see how the stackup will work...on the bottom is the cover plate (with holes through which the LEDs will shine), then the LED strip, and lastly the joggle strip. A row of rivets will be off to one side.

Drilled and dimpled. All that's needed now is to prime this part and paint the cover. The cover will be painted satin black just like the rest of the interior components. I definitely want to paint the cover before riveting this all together so I don't have to mask off 18 LEDs.

With that done, I was going to move on to fabricating the little bushings for the seat belts. However, I remembered that my Crow harnesses have different dimensions for the end attachment fittings.

I dug out one of the boxes with my harnesses and measured the hole. Looks like a .460 diameter bushing should work well. Bushing length needs to be .200 for the lap belts and .330 for the crotch strap.

So, I turned down a piece of 1/2" bar stock to the correct diameter.

Fits! I'll drill out the centers and cut these to length tomorrow.