An M.G. Locost Build
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May 26, 2012
Chassis Details

  Seat belt brackets holding the frame together
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More bits and pieces have been added to our Locost frame. Seat belt brackets and suspension pickups are the latest additions. Welding on the seat belt brackets used up a lot of filler wire, with triple-padded beads on the inside and full beads on the outside. They may not be pretty, but at least they won't be going anywhere in an accident. I'm not even sure they need to be quite that strong. I don't think I'd want to be in the car during any maneuver that would tear them loose.

Ready for the rear suspension  
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The chassis is getting pretty heavy now. I'd estimate around 150 lbs. I can barely move the thing from the table to the floor by myself anymore. Yes, I'm a weakling, but it's not only heavy, it's big, too. However, with most of the attachments out of the way it's starting to feel like most of the welding is behind us, and the era of frame building is drawing to a close. So we're spending more time now with the donor parts, making sure everything is going to fit. So far so good, although there isn't a lot of room to spare.

Without any body or interior panels in place, the car seems really small. It's the same sort of impression you get when you walk through a wood-framed house. The rooms feel small and too close together. It's not until the walls go up that the house starts to feel spacious. Same with the Locost, I think. The transmission is right there next to your leg, the engine's just in front of your feet, and the nose of the differential is directly below your resting elbow.

  Drilling holes in semi-painted A-arms
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We finally drilled the front suspension shock plates and shock brackets, a job we'd been putting off since January because it looked like it might be beyond our well-documented fabrication skills. However we measured the brackets as precisely as we could, and after drilling 1/4" pilot holes we only had to work with a round file for an hour or so to actually get the holes centered. Makeshift jigs (our favorite kind) were then used to transfer the holes to the shock plates, and the brackets are now bolted to the semi-painted A-arms.

Semi-adjustable shock bracket  
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Originally we'd thought that bolting on the front shock brackets would be a cool idea, because it would allow us to tinker with the motion ratio by moving the shocks back and forth on the A-arms. However, now that we've done it, that sounds like too much work. I think they'll be fine where they are. Of course they're a little heavier than they would've been if we'd stuck with the book design and just welded them on, but again we have to ask ourselves, how good would that look?

  Just like a real Locost
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Attaching the front suspension to the frame for the first time was pretty exciting. We've been working on a design to adapt the MGB front suspension to a Locost for years, starting way back in '06 with the A-arms we built for the mock up frame. Back then we didn't realize that caster had to be built into the design, and we more or less went with the book suspension. Over the years we've refined the design into what you see here, however until last week we weren't 100% positive everything was going to work the way it's supposed to.

The fact is, as we've proven on many occasions, anything could've gone wrong. Any one of our measurements could've been miscalculated. Any part could've been built incorrectly. The design itself could've been flawed. So when we bolted the spindle to the A-arms and fed the assembly into the pickups, it was great to see the bushing tubes line up with the brackets, and excellent to see the bolts go in so easily. But the coolest result was when we lifted up the bottom A-arm, and everything rotated freely and easily through a wide range of bump and droop. And just like that, another miracle.

Suspension pickup needs welding and gussets  
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One thing we did late in the game was modify the lower rear brackets in the front suspension. Brackets like this are supposed to have enough flexibility that tightening the nut and bolt will clamp the bushing so it can't rotate and wear against the bolt. Book brackets are designed to do that, but our lower rear brackets aren't book brackets.   So we decided not to weld the rear arm of these brackets, and shaved 1/16" off the bottom face of those arms so they don't rub against the frame when the suspension flexes. We hope it works.

The next hurdle in our little project is the rear suspension. We basically have to take the rear axle apart, cut and grind away the old brackets, and weld on new ones. We're not too worried about welding on the new brackets, but we're a little concerned about welding the trailing links and Panhard rod. Not that they wouldn't be strong enough if we welded them ourselves, but you know, they have to look good too. So I solicited my old TIG-welding chum, and hope to borrow on his expertise again in the near future.

  May actually all fit some day
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Once we confirm the rear suspension is going to work, I think we'll start building the engine bay shelf. It's an important piece to get just right, since it's going to locate the pedals and steering column. And it's another part of the car that we've been designing for a long time. Our latest iteration is based on measurements taken from various cars that range from a 1997 Miata to a 2002 Miata. If the math is right and our luck holds, we'll expect the pedals and steering to work at least as well as the front suspension.


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posted May 28, 2018 at 08:05:05  
I'll third that. What a great blog. Really entertaining. My son and I are busy with a Locost at the moment (Nissan 180sx donor). Home stretch now and I can so relate. Thanks.  
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