August 25, 2012
Most of our early Locost design efforts included lots of sketches in PowerPoint, not because PowerPoint is such a versatile design tool, but because we have to use it every day at work and we're pretty good with the shapes palette. It worked okay for us, though, and over the past year we've actually been shocked by how accurate PowerPoint sketches can be, having taken many measurements off the drawings and found them to match exactly to the actual build.
But we've gotten a little tired of the limitations of PowerPoint. It totally lacks 3D graphics, unless you count the shadow feature, which makes the pictures look pretty but doesn't really help us figure out stuff like whether or not things are going to fit. We still use PowerPoint occasionally to verify measurements, but it's not our first choice anymore for engineering work. We have the actual car now, or most of it, and that's a lot better test bed for our designs. Case in point is our latest chassis bracket, the support bearing mount for the steering shaft connector.
We've been anxious to get this bracket built and welded to the frame, because it's holding up our rolling chassis schedule. Unfortunately we had to toss our Summit Racing steering shaft connector last week because of a big spline count mess, and the new connector hasn't arrived yet, so to keep things moving we made a connector out of wood. For this we used a piece of doweling salvaged from the old mock-up frame, which is still out on the side of the house, slowly disintegrating but still valiantly supporting the build effort wherever it can.
We installed the wooden steering shaft connector in the car, along with a new steering shaft support bearing that actually looked to us like a giant Heim joint, but was sold as a steering shaft support bearing and priced accordingly. In our original PowerPoint design for the bracket, the support bearing would hang from a big steel plate welded on top of big steel strip welded to the frame. To see exactly how this would look, we cut a fake bracket piece out of cardboard and clamped it to the frame. The results were disappointing. The bracket looked like would do the job, but it also looked like it took up half the engine bay. Clearly PowerPoint had let us down.
We sat and stared at the wood connector, and the cheap support bearing hanging from it, for quite a while, waiting for some kind of inspiration to occur. We're not sure exactly how long it takes for that kind of inspiration to occur, but we can at least confirm that it's longer than half an hour, because half an hour later we were still staring at the wood connector, and we still didn't have a clue. But it was a nice day, the ballgame was on the radio, and we enjoyed all the warm sunlight streaming into the garage.
We were about to give up and start cutting metal for the monster bracket, but as we started taking off the cheap support bearing, we noticed that the threaded end of the bearing, when rotated to the side, almost reached all the way to the upper frame rail. It was only about 1/4" away. That looked like something. Could we use it? What if we didn't hang the bearing? What if we attached it from the side? Would that work? The bearing shaft was 3/4" in diameter, as big as the steering shaft. It seemed unlikely that it would bend. With that spark of an idea, we went to work on a new design.
We decided on a plain square tube, welded below the upper frame rail, with a 3/4" hole on the inboard side for the support bearing. The design started out with a 2-1/2" square tube, but by the time we were done working out all the details we had it down to a 2" by 1-1/2" tube, because that would make the support bracket lighter and smaller, and also because we didn't have any 2-1/2" square tubing on hand, but we did have a short length of 2" by 1-1/2" tubing kicking around in the spare metal bin.
So we made the bracket, and it worked perfectly, at least on the wooden prototype which was of course good enough for us. And that meant one more step toward a rolling chassis, and the last of the brackets, except for the spare tire carrier, which we're still not entirely convinced is essential for a rolling chassis. Also the rear shock brackets, which we haven't made yet. So I guess not really the last of the brackets. But we're not going to worry about that now because we have a big huge sheet of 16 gauge steel about to arrive, which we're going to turn into the Locost floor.
To weld the floor in place we're going to have to completeley disassemble the Locost, down to the bare frame. This is another task we've been avoiding for a while, not because it's especially difficult but only because the garage is pretty full right now and we're not sure where all the parts are going to go. I guess we'll figure something out.
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