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Adventures in installing a lightweight battery, part 2.25
For all 2 of you who remember this little project, when we last left off I had the battery installed with a carbon fiber hold down, but the bolts holding it down left a bit to be desired. In particular the back J-bolt at the firewall was WAAAAY too long.
Well, if you are going off the deep end with a project, you can't turn back after you have already jumped! Since I couldn't find a 6mm J-bolt, I determined that I needed to make my own. I thought about buying a piece of mild steel rod, then bending and threading it, but steel has to be pretty darn hot to form to this degree. Aluminum is easier to form at lower temperatures, doesn't really make for good long lasting bolts. Fun fact: Chinese made titanium bolts are pretty cheap on eBay. Grade 1 titanium forms at lower temperatures than steel, doesn't corrode, and should be about the same strength as mild steel. So, here we go:
As it turns out, it was quite easy to form. The propane torch is obviously the heat source, the bolt in the vise gives a radius to form around rather than a hard edge, and the spacer protects the threads. Note that the bolt has that nifty blue-purple tinge to it in the area that was heated.
After a bit more work, it looks like this. The bend radius isn't exactly the same as the stock bolt, but it works just fine. Note how much shorter than the stock bolt it is.
Installed and topped off with (of course) a titanium nut. Notice it could be cut off a bit more.
For the next installment I'll be doing something with the "bolt" on the front of the tray, and that should involve something crazy with a titanium bolt and maybe some more carbon fiber as well.
Well, as far as the weight savings from the latest mod with the titanium bolt, hell no, that wasn't worth the weight savings of 1oz. But I couldn't leave the super-tall-spacer-hack job that was in there before, and I'm the kind of nut-job who enjoys building stuff. So parts 3.5 and 4.0 of this adventure will have me spending more $$ and many more hours to tidy it up further and "save" another couple of ounces.
The battery itself was 16.8lbs lighter than my OEM battery, on my scale.
Another small update, we'll call this update 2.5...
After finishing the rear hold down from above, I still wasn't terribly happy with it. 1st of all the whole thing was threaded. I know this is nit-picky but I didn't like the hook being threaded where it attached to the car. 2nd of all it was made of grade 1 titanium, which isn't all that strong (strong enough, but still...) So now that I knew exactly how long the hook needed to be, I ordered some more titanium bolts (partially threaded grade 5 this time), and went to work again. I'm happy with this, finally, so no more changes here. So here is the new rear hook, compared to the old hook:
Compared to the OEM hook:
And finally installed:
It was a bit of a learning curve again bending grade 5 titanium. I ordered 4 bolts and ended up with two good hooks:
For the front hold down I was absolutely not happy with what I had. The OEM front hook is unique, not threaded, with a strange welded hook holding it on the battery tray. I ended up getting a battery tray and hold down from ebay so I could spend some time figuring something out without taking the tray out of the car for an extended period of time. Basically the way the stock hook works is it is more or less a standard hook, welded to a formed sheet metal "hook" that hooks to the plastic tray. Replicating the formed sheet metal hook part would have been more work than it is worth, even for me But with the whole thing in tension the weld holding the sheet metal part to the hook isn't really structural. Mostly the weld is there to make the part one piece so it will stand on its own when installed in the battery tray. So I took a stock hook and drilled out the weld. This left me with the sheet metal "hook" by itself:
Then I ordered a piece of 6mm diameter grade 5 titanium, threaded one end (threading titanium isn't too difficult with a good sharp high speed steel die), and then bent the other end into a hook:
I took the new hook and epoxied it to the sheet metal hook:
Finally I installed both of the new hold downs (both with titanium nuts, of course ):
This is the way it should be; nuts front and back so I can adjust the front to back clamping pressure. The front hook is a bit long still, but better too long than too short, I'll probably cut it down a bit in the next couple of weeks.
Last of all I started on a carbon panel that will replace the tray that holds the battery, when finished this will have some structure to hold the battery in place side to side:
Love the dedication you've put into this! I read part 1 and 2 first when I came across this thread. Tinkering is fun and isn't always about performance. Gives it a unique touch; your unique touch! Good job!
09-26-15, 08:55 AM
Adventures in installing a lightweight battery, part 2.25
But I couldn't leave the super-tall-spacer-hack job that was in there before, and I'm the kind of nut-job who enjoys building stuff. So parts 3.5 and 4.0 of this adventure will have me spending more $$ and many more hours to tidy it up further and "save" another couple of ounces.
So here is the new rear hook, compared to the old hook:
But with the whole thing in tension the weld holding the sheet metal part to the hook isn't really structural. Mostly the weld is there to make the part one piece so it will stand on its own when installed in the battery tray. So I took a stock hook and drilled out the weld. This left me with the sheet metal "hook" by itself:
):
