An M.G. Locost Build
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September 20, 2013
Front Fenders

We got our new ignition switch installed. It was as scary as we imagined, but after removing a couple of the gauges and disconnecting switches and stretching the choke cable beyond any realistic expectations of flexibility, we got it all reassembled and everything still seems to work, although we might've taken some of the life out of a component or two in the bargain. So far though it's all good, and we shouldn't have to go through that mess ever again, or at least until the turn signal or headlight dimmer switch dies.

  Scary dashboard removal process
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We wanted to get the windshield installed this week, but our new windshield kit didn't include one key component, the rubber strip that goes between the glass and the frame. This strip, called setting tape, is available for sale in very few places, and generally not in lengths shorter than 100 feet. We did find an online rubber store that would sell us just 20 feet of tape, which is only about four times what we need, and only $15, although no telling when it'll arrive. So the windshield is on hold, and next up on our agenda is the front fenders.

Attaching front fenders to a Locost is not a job for wimps. Most Locost front fender stays fail after a few hundred miles due to an inherent weakness in the structure, and constant flexing as the car rumbles and bounces down the road. Although most first-time builders are aware of this weakness, they're reluctant to do anything about it because it hasn't happened to them. So most builders end up making two sets of fender stays, one set that breaks and a second set that looks like a support structure for a freeway overpass. That sounded good to us, so we started building the set that'll break, because first of all they'll be easier to make, and second of all we have the luxury of believing that ours will be the first set of book-style fender stays in the history of Locost builds that won't break.

Unbreakable fender stay parts  
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To make stays, it's important to know how big your fenders are. Oddly enough, even though we're having our fenders custom made, we don't. It turns out that when you order fenders, you can't specify a radius or diameter, and you can't specify tire coverage in angles or degrees. All the fender people want to know is how long the fenders are supposed to be as measured around the circumference, and the straight-line distance between the front and back ends of the fender. That's it. You also get to specify a width, but only from a couple of choices.

We went with a 9" width, because the next smaller size was 7", which wouldn't quite cover our massive 185-section tires. For the other two measurements we came up with a circumference of 29" and a distance of 24" between fender ends as the crow flies. We tried calculating the fender people's measurements based on a 26" diameter and 135 degrees of wheel coverage, which is what we originally wanted, but somewhere between Euclidean geometry and solving simultaneous equations for multiple variables we found a hole in our mathematical knowledge base. Of course it's not like we couldn't have figured it out if we'd stuck with it, because we totally could, but it turned out to be much easier to just print out our PowerPoint design and measure everything with a ruler. Hope it works.

According to our best information, the fender people will take these measurements and cut a 29" strip of aluminum from pre-formed 9" fender material, and then roll it back and forth in a bender until the ends are 24" apart. And then they're done. They never measure the radius, don't need to, and wouldn't be able to tell you what it was if you asked. By the way, since we're only interacting with the fender people via email, we're not sure where they lie on the friendliness spectrum between driveshaft people and glass people. They seemed helpful enough.

  Locost Book fender stay design
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The fenders haven't arrived yet, but as you know we don't let little details like that get in the way of building things. Although we probably should. But the Locost book has detailed plans for the front stays, so that helps, although we pretty much have to ignore the book plans because our front spindles are completely different than book spindles. Our stays will bolt directly to the steering arm, which will allow them to rotate as the wheels turn, which is the generally desired configuration. Although not the only one.

The weak link in the book design is the area where the stay flattens out and bends over the tire. The flat part, specified in the book as only 1/8" thick steel, is bolted to the fender, which then flaps in the breeze, work-hardening the bend and eventually cracking it. Obviously the best way to eliminate cracking at the bend is to eliminate the bend. At least it's obvious to us. So we're going to extend our stay tubes all the way into the fender, where they'll then be welded to unbent pieces of 3/16" thick steel.

Prototype M.G. Locost fender stay  
click to enlarge

We're not 100% sure our design is going to work any better. Our stays could crack at the welds. But to do that they'd have to go through an awful lot of filler material, based on our usual welding technique of melting everything in sight and leaving giant weld beads behind. Anyway, we like our design because the stays will be easy to make, so we went ahead and cut out all of our flat 3/16" pieces and four stay tubes, and even welded up a prototype, which didn't start out as a prototype, but then we fit it to the wheel hub and found out it was too short.

So we cut four new stay tubes and made them all a couple of inches longer, but then decided to forego any further cutting or welding until the fenders arrive, when we can determine the actual radius of the fenders, which should allow us to trim the stays more accurately, although as usual no guarantees. Anyway, despite this minor setback we think we're still on schedule for a mid-October completion date for the car. Although a lot of that will depend on when our shocks arrive.

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