Playing with Plastic: Building A Dedicated Ignition Mounting Board
Wayne Scraba
Mounting an ignition should be simple, right? Maybe not. Sure you see ignition boxes bolted to the firewall on countless cars at countless events, but there are a couple of problems with that: First is the fact some ignition boxes might be water resistant, but they’re not water proof. The firewall is a hot place in any car. An electronic ignition system can make enough heat on its own. They “prefer” a cool mount location. There are definitely better options:
So what’s the solution? Simple. Mount the ignition system elsewhere inside the car. On applications with dash glove boxes, it’s easy to fill the glove box with ignition parts – particularly if you remove the glove box liner and build a “shelf” to mount the bits and pieces (the photos lay out that exact process). It’s also possible to mount the ignition box under or even behind a passenger seat (this is particularly appealing in a dedicated drag car because it provides all sorts of access). Most ignition manufacturers offer extension harnesses, and honestly, the electricity doesn’t care how far it has to run in the car.
So far so good, but ignition and electrical components mandate mounting tactics that differ a wee bit from other hardware. Wayward electrical shorts aren’t the most pleasant things to deal with, and it’s something racers have known that forever. Because of this quite a few pro racers mount ignition and critical electrical components on non-conducting material. That means a metal mount is out of the question. Something like a sheet of thin plywood will work, but to make something that look good and lasts, consider plastic.
Obviously, when it comes to plastics, you have a lot of choices available. One of my favorites for use as an ignition board is Delrin. Delrin is called a “homopolymer acetal”. It’s very easy to machine. It is a very strong, rigid material that offers high mechanical properties. That’s why it’s regularly used to manufacture suspension bushings. It’s easy to come by and is available in a wide range of thicknesses, but keep in mind there are likely dozens of other rigid plastic sheet types out there that will do the job. For an ignition board, you’ll need something strong enough to support something like the weight of a coil and an ignition system. Keep in mind that some of today’s coils are considerably larger than their predecessors. In simple terms, they’re big and heavy. So are full feature ignition systems. Because of this, it’s a good idea to cut ignition boards from ¼-inch thick board.
In my formative years, I was a big fan of going directly from dream to concept when it came to building something. I learned over time that was a pretty big mistake! It’s must more effective to make a pattern from paper first. The truth is, it’s a whole bunch easier to erase a pencil line on a piece of paper than it is to fix something carved out of metal or even plastic. Using a pattern simply allows you to check fit before actually building a specific component. And it also gives you something to carefully follow (like a blueprint) when you’re cutting, filing and drilling.
I use heavy stock paper (smooth Bristol paper) for patterns. Artists use it, and magazine types like me often use it as a neutral background for shooting photos. In my world, once too dirty for photo purposes, it’s recycled as pattern making paper. You’ll find this stuff is cheap and every office supply store in the continent stocks it. You’ll need a good old-fashioned lead pencil; a carpenter’s square and an 18-inch drafting ruler come in handy too. Ditto with a good caliper.
When the time comes to draw the pattern, you’ll either need the part(s) you’re mounting or a scale (or better yet, a full size) drawing of the component mounting surface. First, lay the part out on the pattern and then figure how big the outside of the piece needs to be. When calculating the overall size of the piece you’re building, you have to take into account the sizes of the fasteners you’re using as well as the total number of fasteners required for mounting. Why is that important? See the sidebar on edge margins. You’ll need to calculate them. When figuring edge margins, I usually give myself some extra room. The fudge-factor allows for things like rounded corners. And when discussing corners, you’ll note (in the accompany photos), I never included them in the patterns I made. Some applications need them rounded for clearance. Some don’t. Some people like the appearance of liberally rounded corners. Others don’t. You’ll also see I simply marked locations for a hole with an “X”. The reason is pretty simple: To transfer the hole location from paper to aluminum, I use a center punch. The “X” makes it a bunch easier to accomplish. Once I’m satisfied with the pattern, I cut it out with scissors.
As mentioned earlier, I regularly test fit the pattern. Sometimes I fit the thing more than once too. The reason is it’s just way easier to test fit (and of course, fix) something made from paper than it is to build fresh parts. Honestly, I’ve managed to engineer some pretty cool parts on paper, only to find they were completely useless in the real world. That’s why test fitting is so important.
Once you’re satisfied with the fit, you can transfer the pattern to the Delrin. Although there are a number of ways to do this, for my purposes (and likely yours too), simply attach the pattern directly to the plastic sheet. Here are some photos of how I do it:
As pointed out in the text, when it comes time to make patterns, the place to begin is with a pencil and paper. Make a rough sketch of what you’re trying to build first. Next, using the sketch as your guide, you can begin to layout the pattern.
I didn’t keep the pattern for the ignition board, but here’s a pattern I made for a doubler plate. This one was designed for support a large, heavy aftermarket fuel filter. It sure isn’t fancy, but it works.
Once the pattern is tested for fit, lay it out on the sheet of plastic. I usually run a line of masking tape (on the plastic) where the pattern edges show. The reason is you can make your mark on tape instead of trying to see a black line drawn on something like a black board.
In order to make clean cuts I setup a little home made fixture out of scrap 1X4’s and/or 2X4’s to clamp the plastic in place while the various cuts and holes are made.
In order to cut plastic, I use a relatively fine tooth (12-21 tooth) saw blade in a jigsaw. Then I cut out the pattern in the plastic.
These photos show the “almost” finished piece. At this point, the holes for the component mounts weren’t finished.
This photo shows it installed in the glove box of a Buick Regal I built a dozen years ago. It was a simple part that worked out well. And from my perspective, simple is good!
