An M.G. Locost Build

November 30, 2011

This Locost build is just chock full of surprises. The latest involves the suspension bushings. These are purportedly made for a Triumph Spitfire, a British car from the 1960s, only about one decade removed from the last of the Whitworth hardware, and still a generation or more away from anything Metric. So when we got the bushings and sized them up, the 3/8” holes in the middle seemed appropriate enough. All of the other dimensions, length and diameter, matched the book specs exactly.

  3/8" bolt bad, metric 10 mm good
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But last night we were playing around with a bushing and a 3/8” bolt, and we noticed that something wasn't quite right. The bolt seemed a little too loose inside the bushing. That shouldn’t happen. The bolt needs to be an exact fit so the suspension doesn’t knock it around and loosen everything up. On a hunch we tried inserting a 10 mm bolt, and surprise! A perfect fit. Which left us thinking, how is that possible? Some kind of bizarre time warp? Could Triumph actually have used metric-sized bushings fifty years ago? That seems so unlikely.

Much more likely these bushings were manufactured by some foreign (and by “foreign” we mean cheap, no offense) company that never heard of British Standard, and made them in a length and diameter specified by some Triumph aftermarket people in fractions of millimeters. And since they didn’t have any bushing tubes with a 9.525 mm inside diameter lying around, they must’ve figured 10 mm was close enough. And the Triumph aftermarket people were apparently okay with that, or possibly didn't know any better.

So now all of our plans for close-tolerance AN suspension hardware are out the window, and we need to figure out lengths and grade strengths in a whole new language. And we’ll need to remember to use a 14 mm wrench on the suspension, although I think a 9/16” wrench will work in a pinch. But maybe before we go through all of that, and before we drill out all of our new suspension brackets to 10 mm, we’ll try another source for Triumph suspension bushings. Maybe something other than eBay this time.

Frame tubes labeled and covered in Saran Wrap  
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Earlier in the day we took inventory on our frame tubing. We’ve been ordering sheet metal and round tubing for the suspension pieces from time to time, and in most of the orders we included a few lengths of 1” square tubes, since we knew we’d eventually need it. It turns out we went a little overboard and we now have more than enough 1” square tubing to finish the whole frame. Although not enough for a whole frame and a steel build table. We're not actually looking forward to making a build table, but we suppose it has to be done. Although not necessarily in steel.

We might go with the simple MDF-on-sawhorses design. Except we don’t have any sawhorses. We used to, but over the years we cannibalized the wood for other projects, and now we only have a few left-over sawhorse brackets. Building an actual solid table from scratch is another way to go, but big heavy wooden tables take up a lot of room, and they tend to stay where they're built for a long time. We'd prefer something that we could take apart in minutes and burn for firewood when we're done.

  Laying out the wood frame way back in 2006
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We didn’t need a build table for the mock-up frame. We just laid out the wooden tubes on the living room floor, with duct tape marking the dimensions, and fit everything together. But that was glue, and this is welding, and so the living room is probably out of play on this one. Still, it’s kind of interesting to note that in order to build a Locost frame you only need a flat surface twice, once to lay out the dozen bottom tubes, and once to line up the rear overhang. Everything else is attached to the frame itself, and it doesn’t matter what the frame is sitting on.

A proper size 3/4" W1 in the mock-up frame  
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Also interesting is how the Locost book sometimes contradicts itself. The cut list, for example, has the W tubes made out of 3/4" square tubing. But the text says to cut them out of 1” square tubing. For most of these discrepancies, we’ll go with the bigger and stronger example, but in this instance we think it makes more sense to go with the smaller W tubes. They intersect the Y and O tubes at about a 45-degree angle at either end, so they’ll fit better. Plus, we already cut the W tubes out of 3/4" tubing a couple of months ago. So there's that.

Moving forward, we still have another sixty feet or so of 1" tubing to cut for the basic frame, then another thirty or so for the transmission tunnel. And maybe a couple of brackets. Just a couple of days. A month at most. Then it’ll be time to weld.


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