07.17.08
Hard Points
While I’m growing new fingertips, I decided to put a bit of work into figuring out how to mount the seat buckets to the seat sliders today. In the original Bradley design, left and right sliders were bolted directly to the seat bucket. In the car I purchased, a previous owner had modified the design by attaching the sliders to the buckets with a set of custom brackets (see the photo of the seat slider in yesterday’s post).
When I removed the foam and fabric from my seats and discovered how the sliders had been mounted, I knew that I wanted to do something different. The idea of having bolts protruding thru the seat buckets in the vicinity of my posterior didn’t exactly thrill me. Granted, there is roughly 2 inches of foam padding that overlies the bolts, but it just seemed like there ought to be a better way.
In the fourth photo, you can see a pair of metal strips. Each strip has two bolts tack welded to it. The nearer one shows the bolt threads and is just thrown in the bucket; it is positioned in a set of holes that are in the lower right corner of the photo. The far one is properly positioned so that it can be attached to the rear two brackets on the sliders. A bolt was run thru the center hole in each strip and fastened to the seat bucket with a nut. In this way, the strip was held in position and wouldn’t go flopping around (under the upholstery) if the two outside nuts were loosened. Also note the wallowed-out holes for the bolts that secure the rear brackets to the seat sliders. How would you like to sit on one of those? Ouch!
In the third photo, you can see how the bolts welded to the strip protrude thru the seat bucket and attach to the rear-most slider brackets. The second photo shows how the bolts in the second strap are supposed to attach to the front two slider brackets.
I decided to try a different approach — one that would result in no hardware contained inside the seat buckets and under the upholstery. I made a set of 8 hard points out of 1/2-inch mild steel plate. The hard points are 1-1/2-inches square and are drilled and tapped for a 5/16-18 bolt. The parts were cut from steel plate on a band saw, trued up on a small mill-drill, drilled on the mill-drill and then tapped by hand. Four of these will be attached to the bottom of each seat bucket.
If you’re familiar with Moldless Composite Construction, the hard points are just floxed in position and glassed over. If that’s Greek to you, they’re held in position with a material called flox, which is a mixture of pure epoxy and flocked cotton fibers. Flox is a structural adhesive — meaning that it can accomodate loads. When it cures, it has the hardness of concrete. Many of Burt Rutan’s airplanes are held together with flox joints and some of them have been flying for over 30 years now. Once the hard points are floxed into position, I’ll lay 12 plies of bidirectional fiberglass over them and then peel-ply the glass for a smooth transition onto the surrounding seat pans. I’ll have more to say about flox when I do the lay-ups and, by then, we will already be familiar with the different types of fiberglass and epoxies from having done some simple lay-ups. I’ll post pictures when the job is actually undertaken. Until then, this should tweak your curiosity on some of the techniques that we’ll be learning here.
It took about 6 hours to make the hard points but the end result should be worth it — rock-hard mounting points for the seat buckets where all of the hardware can be accessed from the outside of the bucket.
