An M.G. Locost Build
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July 12, 2012
More Chassis Details

We've been finishing up a few chassis details this week, which means of course we're stalling again on all the things we need to do to get the car rolling. But we did at least complete the steering rack mount, and welded in a mount for the spare tire, and also built an aluminum spacer for the handbrake, which are all things that needed to be done eventually. So it's not like we're slacking. Okay it is, but I'm sure we'll start on the rear suspension real soon. Any day now.

  Surprisingly lengthy steering rack
click to enlarge

To complete the steering rack mount, we cut two 4" lengths of channel out of 1/8" wall 1"x2" tubing, drilled a pair of holes in each, and welded on blind nuts underneath. We bolted these channels to the steering rack, and then, using the rack as a jig, welded the channels to our massive steering subframe-slash-bridge abutment. This worked pretty well, although welding nuts to the channels generated so much heat that we distorted the threads, and had to chase them with a tap. But we're good now, and the blind nuts should make the rack really easy to remove and install, should we ever need to do that.

We hate to admit this, but we never got the steering rack shortened. This wasn't because we were too lazy, although we'd have been okay with that. It was because we couldn't figure out how a shortened rack would fit in our Locost. The steering column is attached to the rack at a fixed angle, so shortening the rack 4" would've moved the column 2" inboard, where it would have run directly through the engine mount. We could've shortened the rack 2" and still had enough clearance, but chopping 2" out of the rack hardly seemed worth the effort.

So we went with the recommendation in the book, which says nothing about shortening racks and only says to make sure that the steering arms are level at static ride height. In theory this keeps the arms from shortening much on bumps, hopefully no more than the A-arms. We tried to test this out by bolting on the suspension and raising and lowering it with the steering arm attached, but we only have the stub axle on there now and we couldn't really tell if it moved. If it did, it wasn't much, and in any case we still have to extend the rods an inch, which we think will help even more.

Handbrake with giant aluminum spacer  
click to enlarge

In typical British fashion, the backing plate on the MGB handbrake is outboard of the ratchet mechanism, which precludes the brake from operating if you mount it flush to the transmission tunnel. To deal with this, the folks at Abingdon added a bulge to the tunnel. We made a spacer. If we'd stuck with our traditional method of using the heaviest possible components we can find for any given application, we'd have used a giant chunk of 1/4" steel for this. Oddly, we went with aluminum. It's mostly hidden by the handbrake so we're okay with it.

  Visualize spare tire attached
click to enlarge

We weren't sure exactly where to mount the spare tire. We wanted it centered over the rear panel of course, but we weren't sure just how high to place it. Oddly enough, you can't find this kind of information anywhere on the Internet, at least if you limit your search options to Google. Jeeves might've known, but we weren't sure we could trust him with something this important, so we didn't ask. Luckily, Google has pictures of everything, although surprisingly not a lot of Caterhams from the rear.

But the two pictures we did find were enough to confirm that the spare tire should sit flush with the bottom of the frame, with the top sticking up about 4 to 6" above the trunk. So we drilled two 1/2" holes 4-1/2" apart in a 2" strip of 1/8" steel, and welded the strip between the two vertical support tubes, with the holes exactly 11-1/2" above the bottom of the frame. We expect this structure to be strong enough to support a 40-lb. wheel and tire, but just in case the spare falls off one day and rolls into a ditch, we'll also carry a can of fix-a-flat. Although we may need to think about a mount for the can of fix-a-flat. Probably not hanging off the back of the car.

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