Wednesday, November 19, 2008

Hacking the Final Hold-downs

I installed the remaining hold-downs for the 12V auxiliary battery and the extra battery in the rear trunk this evening. I hadn't designed these hold-downs before I sent all the pieces off to powder-coat, so I'll have to paint them with POR-15 protectant before I finish.

Here's a picture of the 12V aux battery hold-down. The battery is a smaller motorcycle battery. The bar across the top is held down by a 3" piece of 5/16" all-thread with 1 5/16" spacing between the bar and the hold-down for the traction battery next to it. It turns out this is five nuts and a 1/16" thick washer.

Looking the other direction, the other end of the hold-down bar is simply held down with a piece of 5/16" all-thread going down to a hole we drilled in the last post (see third picture down in the last post).

This is a view underneath the passenger side of the car looking up at the 12V aux battery (which looks scratched up alrady). The nylock nut in the center right caps off the 5/16" all-thread above and holds it in place.

Here's where the extra battery in the trunk sits on the passenger side. I cut a 15" long piece of 1" wide steel bar (1/8" thick) and drilled a 5/16" hole in each end 1/2" from the end. I laid this piece down where the battery sits and marked through the 5/16" holes. The rear-most hole sits right on top of rear-most structural bulge. The front hole sits just in front of the forward-most bulge.

After marking the holes, I drilled them with a 11/32" bit so the holes would be a bit larger to allow a bit of inaccurate drilling.

Here are two pieces of 11 3/4" long 5/16" all-thread. I used regular nuts with washers on the top side.

Here is the underside of the car with the two pieces of all-thread through the holes in the 1" bar we laid out earlier and capped off with nylock nuts.

With the all-thread in, I added a piece of 3/4" angle iron with 11/32" holes drilled in it through the angle-iron corner at each end. It's held down with a washer and wing-nut. Drilling the holes in the corner of the angle-iron was rather tricky; I had to use four progressively larger drills to get the final hole size without the drill corner binding on the inside faces of the angle-iron.

I think I'm finally done with the vast majority of the mechanical design. I'm tired of designing mechanical things and just want to wire this puppy together. Let's see what we can do tomorrow.


Unknown said...

I'm not sure that the motorcycle battery as your aux 12v battery will last very long. A motorcycle battery just like a traditional car starter battery exists merely to provide high amperage for a short period of time to start the vehicle, then recharges. A deep cycle load of headlights and radio won't allow very many charge/discharge cycles on the motorcycle battery. I suspect you will need to move to a deep cycle battery unless you have a DC to DC converter and merely use the motorcycle battery as a buffer. My apologies in advance if that is what you have planned already.

TimK said...

The charging unit has a built-in 50 amp DC-DC converter that will handle this. The "motorcycle" battery is actually a deep-cycle sealed AGM battery (30 Ahr). I think having the DC-DC takes care of a lot of issues.