Thought I would add my two cents worth, as I used to build race car
looms and am in the middle of building a set of Spitfire looms.
The major problem with soldering is that the joint becomes very
brittle. In aerospace applications (and hence race cars as well) solder is NOT
used. Vibration from the road and engine are considered harsh enough that a
soldered joint, no matter how well supported, will not have the longitivity and
reliability that the application requires. The MilSpec components that we use
are all the 4 or 8 indent crimp type. Load carrying for each circuit ranges
from 7.5A to 25A.
Road car manufacturers tend to use large gage wire, certainly much
larger than is required. Mostly, this is to allow for unsecured/unsupported
installations, abrasion resistance at low cost, and cost savings in wire.
For my two spitfires and my friend's project spit (a 71 with a 14"
wider chassis and a LS400 V8 stuffed in) I plan to use 14AWG wire for the large
power carrying circuits, 18AWG for everything else. The looms will be built in
sections, the main chassis loom being split into three separate parts, and
minor looms going between the main looms and the car. The main sections will
be bracket mounted to the chassis and the minor branches used to connect to the
car systems. The advantage of the modular system is that the main section can
be treated as permanent, and the minor sections (which generally are the
sections to get damaged) can be easily and properly fixed or replaced if
damaged.
Connectors used are Circular Plastic Connector Series 1 & 3 (CPC) by
Amp. Pins are crimp type, and each signal pin has a current carrying capacity
of 13A. Wire used is surplus Teflon coated MS stranded wire. Heat shrink will
be used to cover the wire bundles and provide abrasion resistance. In some
portions we may need to provide an inner metal braid to be used as further
protection. The looms will be secured to the chassis both with brackets at the
connectors and tie wraps every foot or so using the clever little T&B blocks
epoxied to the chassis.
The engine loom will be completely sealed, and we are considering using
the metal shelled connectors there. The only problem is cost- the metal shell
connectors cost anywhere between $10 and $50 per side depending on number of
pins, size of shell, etc, whereas the CPC's are between $1 and $7. We will be
using heat shrink boots on the back of the connectors in the engine bay. These
run about $7 apiece, and provide sealing to the back of the connector as well
as strain relief to the wire bundle. And a very clean appearance.
The main and rear looms are inside the car, and therefore protected
from the elements. More than likely we will save some money and use standard
backshell strain reliefs. They will not be sealed the same level (maybe for my
rally car they will be) for cost reasons.
The wiring plan right now has 27 connectors, 16 fuses, 6 relays and
850' of wiring. Material costs alone are around $500. Yes, it seems
excessive, but when it's done, it will be right. Considering that the Painless
wiring products are in the $350 range for the full 18 circuit version, and it's
not a terribly big jump over going to the boneyard and getting a harness from,
say, a Corolla to put into your car. (not that there is anything wrong with
going this route, it's just not custom fitted and doesn't look particularly
great)
Sorry for the long winded post, it's a project of mine that I've had
intense interest in and have been spending way too much time thinking about.
Scott
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