Dave Bailey
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| posted on 6/2/08 at 03:34 PM |
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Earth points
What is the general opinion about grounding....
1. Run grounds back to a central point
2. Ground lights etc locally
also ground points have people welded studs or drilled the chassis tapped holes and fitted threaded studs?
thanks
Dave B
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JoelP
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| posted on 6/2/08 at 03:37 PM |
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id vote local, with a welded stud/bolt.
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RazMan
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| posted on 6/2/08 at 03:43 PM |
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Best to run an earth loop around the loom, running from each device and on to the next one. That way you can always tap into it if you add a device
later.
You can then weld a bolt to the chassis and terminate the cable to this. I have two main earth studs on my chassis, front and rear. The engine will
need to be earthed too so don't forget (many do) or it can be very confusing, especially if your engine is on rubber mounts. Keep it a simple
as possible - earth faults can be a bugger to find sometimes.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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worX
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| posted on 6/2/08 at 03:44 PM |
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You can never have too many Earth points!
Steve
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02GF74
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| posted on 6/2/08 at 03:45 PM |
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I'd vote run wire back to central point.
Steel is not as goods a conductor as copper and depending on how good your welding ist, there may be higher resistance at welds. Also it rusts so a
self tapper is not gonna be a top idea.
with higher currents e.g. head lamps you may loose power so get dimmer lamps.
With copper you take all that out or the equation - production cars use earth runs and you'd think they know what they are doing.
Having said that, you'll probably get away with grounding locally.
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nick205
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| posted on 6/2/08 at 04:15 PM |
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Welderman - do you concur? 
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dan__wright
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| posted on 6/2/08 at 04:22 PM |
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i have two earth point, one for my front light and then main chassis earth that everything else including battery connect too, the front earth was to
keep the size of the front loom down so it isnt too visible and it doesnt draw that much.
FREE THE ROADSTER ONE…!!
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David Jenkins
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| posted on 6/2/08 at 04:38 PM |
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I have a mixture, a bit like Dan.
One hefty great stud welded in next to the battery and starter solenoid. This takes the battery -ve, engine block earth strap and so on. It's
also the common point for anything close by, such as the ignition system.
I then have 2 points up front, one for each light, and one at the back.
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Bob C
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| posted on 6/2/08 at 04:46 PM |
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I welded 3 M6 bolts to the chassis for earth points (after it was painted - DOH), one by the front lights, one near the scuttle and one at the
back.
Don't worry about the resistance of steel, you have a whole chassis worth of cross sectional area - each tube is 160mm^2 - that's
equivalent to a copper conductor about 13mm diameter. (assume 6 chassis tubes)
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Mole
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| posted on 6/2/08 at 05:10 PM |
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I'd have thought the surafce area would make up for the reduced conductivity of steel as well.
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dhutch
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| posted on 6/2/08 at 06:09 PM |
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On (steel) boats its commonly accepted the best option is to use a fully two-wire system. With the parts carefully isolated from the hull (usally).
Rather than using the hull/chassis as return. And then have one earth point on the hull, near the engine/prop, for the domestic, engine, and mains
voltage systems.
- Thus removing any corrosion issues relating to having current flowing in the hull.
However in cars its quite common to use the chassis as the return path. Which also works fine, as long as the earth points are made well.
- In the aero industry its all single wire too, simple for the sake of weight saving.
- Coppers heavy, and planes are aluminum anyway.
On a kit car, i dont know what i would do, or what the norm is however.
Certainly if i was making an earth point anywhere, i would do it as a welded stud, with plenty of grease over the place.
Daniel
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Hellfire
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| posted on 6/2/08 at 06:44 PM |
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On planes wihch use aluminium as the conductor - aluminium is 65% as conductive as Copper (100%)
Steel is only (at best) 15% conductive. If it's good enough for the manufacturers its good enough for me.
Steve
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Bob C
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| posted on 6/2/08 at 06:59 PM |
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yep Cu resistivity is 1.7 u ohm cm
mild steel is 15
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Peteff
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| posted on 6/2/08 at 07:37 PM |
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The area of the steel in a chassis is much greater than the area of a piece of battery cable though so the resistance is only going to be at the
connection point.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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