Saturday, July 19, 2008

Rear Trunk Battery Rack

Today was busy, so you should see a few posts. This first one is all the work I did installing the rear trunk battery rack base. As I mentioned before some of this will be verbose as I'm trying not to lose all the finer details.

A few posts ago, I cut some 1.5"x1.5" square tubing 18" long (1/8" wall) and drilled a 3/8" hole in each end, 5/8" from the end. After laying these down in the trunk where I wanted to put them, I realized that there is a manufacturing "bump" on either side of the trunk. I got out my handy sledge hammer and flattened out the inner edge of the bump (under the head of the hammer in the picture above) to remove the interference.

Here is my attempt at finding a good place to drill a 3/8" hole to install the square pipe. My first attempt missed going through and ended up inside a support beam. The second attempt (upper hole was much more successful. This picture shows the passenger side of the trunk right up at the front just behind the rear seat, which is folded down.

There's a plastic plug to help us find a good place. I drew a horizontal line from the center of the plastic plug to the side of the car. I measured 1.25" toward the rear of the car and put another horizontal line. I then drew a line that "connected the dots" of the spot welds for the main support. After that, I drew a parallel line to that 3/16" towards the center of the car. The intersection of the second parallel line and the horizontal line 1.25" rear of the plastic plug is where you want to put the hole.

As I've mentioned before, start with a center punch, then drill a small hole (around 1/8") and then go for the larger 3/8" hole to prevent the drill from skidding around.

Here is the hole that I drilled in the previous picture from below. It goes through two pieces of metal so it should hold well.

I dropped a 3/8"-16 by 2.5" bolt down through the square tube and into the hole. To get the 3/8" nylock nut (and washer) to grab on the bottom, I needed to dangle a box wrench on the bolt head above. If you have two people this isn't an issue because one person can hold the bolt on top while the other person tightens it from the bottom. I still have to powdercoat the metal pieces, so I didn't actually tighten down the nuts, but let the bolt sit in the hole so I could drill an accurate hole at the other end.

The next step was to "connect-the-dots" again for the spot welds just under the rear end of the square tube. I drew a second line, parallel to the "connect-the-dots" line 3/16" towards the center of the car. I centered the hole in the rear end of the square tube on this second line and drew a circle with a pen through the hole. After rotating the rear end of the square tube away, I could then drill a 3/8" hole after center-punching the circle and drilling a 1/8" pilot hole.

Here's the driver-side front measurements being done. Again, the hole point is 1.25" rearward of the center of the plastic plug and 3/16" toward the center of the car from the "connect-the-dots" line from the spot welds.

This hole was a little less successful since I hit the edge of the double layers of metal that were spot welded together. I don't think this will be an issue, but I'll make sure to put an extra large washer underneath the car on the 3/8" bolt to spread the load out.

I drilled a hole for the rear end of the driver-side square tube the same way I did for the passenger side. Align the rear hole up with a line 3/16" inside of the "connect-the-dots" line for the spot welds.

After installing the two square pipes, I installed the two pieces of 1.5" (1/8" thick) angle iron to support the front and rear edges of the batteries. Both pieces of 1.5" angle iron are 36" long. The front piece has 3/8" holes drilled in it 3 3/8" from each end, centered between the longer edges (that is 3/4" from each edge). The rear piece has 3/8" holes drilled in it 2 1/2" from each end, again centered between the long edges.

This picture shows how to align the inside vertical edge of the front bar with the seam on the chassis in front of the shock tower. After trying several places with the foam-core batteries, this seemed like a reasonable place that keeps the batteries far enough forward but still gives a bit of breathing room behind the rear seat.

With the front bar aligned, I drew two circles onto the square tubes through the 3/8" holes. After removing the front bar, I center-punched, pilot-drilled and then drilled two 3/8" holes in the square tubes to match those on the front bar.

Here is the front bar in place with two 3/8"-16 by 3/4" long bolts. Since I still have to powder-coat everything, I haven't added the nylock nuts. The nylock nuts will have to be added by taping them inside a box wrench and inserting the box wrench end into the square tube to line up with the bolt being inserted from above. I'll have pictures of this later.

With the front bar in place, we now align the rear bar so that the inside edges of the vertical metal are 13 1/8" apart to allow for the batteries and a bit of expansion. After the rear bar is placed and centered right-to-left, I drew circles in the 3/8" holes I had drilled earlier in the rear bar (2.5" from the ends) onto the square tubing. I drilled 3/8" holes in the square tubing (again, center-punch, pilot-hole, final drill) and dropped 3/8-16 by 3/4" bolts into the holes to complete the base of the rear trunk battery rack.

Things that still need to be done for the rear rack are adding the 3/4" angle iron for the hold-downs, drilling all the needed holes for the hold-downs and powder-coating everything to protect it from rust and battery acid fumes.

Next up: The firewall battery rack

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