An M.G. Locost Build
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November 12, 2012
Wiring Ideas

We thought things would get exciting once we pulled the engine out of the car, and they might yet, but we've got to get the frame finished up, and most of that work has been boring so far. For example, capping all of the open tube ends. You can't have open tube ends on your Locost collecting mud and rust and other debris, so you have to weld a cap on each one. There were a total of 18 open ends, and each cap had to be cut and fit individually because we were too lazy to make all 18 at the same time.

  Custom-fitted end cap, before welding
click to enlarge

The job took 10 hours, about four of which were spent fishing caps out of tubes after they fell in. We cleaned up some of the caps after welding with our trusty Harbor Freight angle grinder, which seems to be running better lately, probably due to the cooler weather. Tube end caps at the back of the car had to be sanded down flush, because the aluminum bodywork will have to fit over them somehow. The other caps didn't merit any special attention, but we thought they at least ought to look nice.

End cap welded and ground flat  
click to enlarge

With the task of routing the wiring harness looming (possibly clever pun for our British readers), we decided to weld on a few more tabs to the frame, because we don't think we've made enough tabs yet. These tabs will allow us to attach cable clamps (P-clips) at strategic locations, thereby reducing the number of holes we have to drill into frame members, and the number of sheet metal screws we'll need to use. Nothing against sheet metal screws, but we just don't like them.

  More tabs to weld to the frame
click to enlarge

We made the tabs out of 16 gauge sheet metal, and welded on 10-32 blind nuts so we'll only have to deal with screws and not nuts when we're attaching P-clips. The tabs look a lot like our usual flat tabs that we used to make out of 1/8" steel, except thinner. We're a little more impressed these days with the strength of 16 gauge steel, especially after working with all that 18 and 20 gauge sheet metal for the paneling, and it seems like maybe we could've made a lot of our earlier heavy-duty 1/8" brackets out of 16 gauge. Oh, well, too late now.

May look better after the frame is painted  
click to enlarge

The only downside to welding on tabs for the wiring is that we don't yet have a super accurate idea of exactly where the harness will go. As an exercise, we tried attaching the rear part of the donor harness to the frame with masking tape, but after fiddling with it for half an hour we realized it wasn't going to fit because it was about four feet too long. Not necessarily a show-stopper, but clearly something we need to deal with, and since it has to do with electricity, we have a limited number of options.

  Stock MGB wiring harness almost fits
click to enlarge

Our first option was shortening the harness. Luckily we were able to immediately dismiss that because it would involve cutting and reconnecting wires, something we want to avoid if we expect to have any success at all wiring the car. Besides, we think it's a good idea in general to not mess with parts from the donor, or to modify them in any way, so you can buy new parts off the shelf when, for example, you hook up something wrong and accidentally burn up a wiring harness and need to replace it.

Our second option was to loop the harness behind the passenger seat bulkhead. We tried this and it looked okay, and it'll be well hidden in any case, so long as it doesn't set up some kind of weird magnetic field every time we hit the brakes. With everyone more or less in agreement with this arrangement, and no other viable options anyway, we went ahead and welded five tabs inside the transmission tunnel, and three more to the round tube in back. We hope we get to use them.

We'll have to do the same sort of thing for the fuel and brake lines. These lines will run along the other side of tunnel, where they'll be out of harm's way when the wiring harness bursts into flames. We shouldn't need much more than the five tabs in the transmission tunnel, since the fuel and brake lines don't really go any farther than that. Once all the tabs are done we should be able to start welding sheet metal. Although no guarantees we won't find something else we have to do first.

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Comments:  
posted April 25, 2017 at 02:11:52  
Thanks so much for the blog article. Much obliged.