Uncommon Grounds

[MisterCinders]

Every now and then I flirt with building a new harness to clean up my crappy one. As I gaze longingly at the wiring diagram, I wonder . . .

Why do we run all that black/white ground wire through the harness? So long as the grounds make it to a solid frame point, it seems like you could use multiple "local" grounds on the frame in proximity to the relevant device.

In the front, you could ground the horn, front signals, head-light, etc. Then you could ground the rear signals, brake light, etc. The long runs of black/white wiring could be eliminated in favor of local frame grounds.

Or am I just dumb and missing a fundamental reason that we consolidate the grounds to central frame point?

 

[posplayr]

I wote this in response to another poster, but it seems applicable to your question as well.

http://www.thegsresources.com/_forum/showthread.php?t=194107


There is further discussion in the "GS Charging System Health".
GS Charging Health

The 550 Bobber schematic follows the guidlines I have outlined and would readily apply to your bike as well.

This is the minimum wiring requirement for a GS (in my opinion)

http://www.thegsresources.com/_forum/showthread.php?t=153727&highlight=550+bobber

 

[MisterCinders]

If I understand this properly, all the grounds must ultimately trace back to the source (i.e., R/R and battery). Even a frame ground does this because the frame itself ties in to the R/R and battery ground.

As a voltage path for the grounding leg, is the frame better or worse than a long wire run? I am guessing steel tubes provide more resistance than a dedicated ground wire. Is that correct?

 

[rustybronco]

As a voltage path for the grounding leg, is the frame better or worse than a long wire run? I am guessing steel tubes provide more resistance than a dedicated ground wire.

It depends on the diameter of the wire and the material the wire is made from. Resistance lowers as the diameter of the conductor increases. Resistance also depends on the composition of the material.

One thing to consider, you wouldn't want the current to flow through the headstock bearings. It's not not good for their longevity.

 

[posplayr]

If I understand this properly, all the grounds must ultimately trace back to the source (i.e., R/R and battery). Even a frame ground does this because the frame itself ties in to the R/R and battery ground.

As a voltage path for the grounding leg, is the frame better or worse than a long wire run? I am guessing steel tubes provide more resistance than a dedicated ground wire. Is that correct?

unless a wire is seriously undersized the primary consideration is the elimination of contacts, connections, switches.....etc that have much more resistance that base wire.

The only two places where a GS electrical/harness is generally under sized is in the power and ground wires on the R/R(-).

On the R/R(+) side the harness goes imediately to a "T" splitting between ignition switch and battery. So that is not so bad.

On the R/R(-) side if you keep it short and do a single point ground then there is current sharing amoung the three sources and so the small size is not really an issue there either.

 

[jesustheplumber]

i agree with rustybronco. being a plumber i know that dissimilar metals corrode much faster when you pass a current through them (most piping systems are bonded to the electrical systems in a house.) given that bikes don't have copper touching galvanized metal, i imagine that using the frame as one huge ground could speed the decay of the bike. though i have seen odd contraptions that used electric frequencies to stop rust.

 

[MisterCinders]

i agree with rustybronco. being a plumber i know that dissimilar metals corrode much faster when you pass a current through them (most piping systems are bonded to the electrical systems in a house.) given that bikes don't have copper touching galvanized metal, i imagine that using the frame as one huge ground could speed the decay of the bike. though i have seen odd contraptions that used electric frequencies to stop rust.

But I'd think the frame/ground is not the same as a pipe/ground.

In a house, the pipes can be a suitable separate ground path (not a return path) because they ultimately enter the earth for sewage, water service, etc. So running a ground through a copper pipe into the ground or through copper wire to a long copper rod into the ground may be "6-in-one-half-dozen-in-other." As I understand it, those ground paths through the pipes or a third ground leg are to manage surges, not to complete a circuit with the power source.

On the bike, the frame isn't "grounded" (because of those pesky rubber tires), but the frame tubes can provide the negative return to complete a circuit in place of wire if the frame is linked to the battery's negative terminal. That's why I wondered if wire>frame as a "ground" return path to the battery.

If I follow posplayer's guides, the ground path for us needs to (a) complete the relevant circuit and make stuff work; and (b) provide accurate voltage and current to the R/R to manage battery drain and charging.

COuntdown before posplayer drops in to school me on where I am wrong . . .

 

[jesustheplumber]

but the power plant is grounded to the earth just as the battery and charging circut are grounded to the frame.... yet both have a dedicated wire.... posplayr?

 

[MisterCinders]

but the power plant is grounded to the earth just as the battery and charging circut are grounded to the frame.... yet both have a dedicated wire.... posplayr?

The battery is not grounded to the frame. The connection between the battery and the frame is to "ground" the frame to the battery.

In houses, the ground wire is separate from the return wire (e.g., the third plug on an outlet). This wire (usually green) runs along the return path of a circuit but then ties into a grounding system like pipes or some other metal path that reaches into the Earth. Hence the name "ground."

The ground path is there to provide a surge or short with a faster route to the Earth than the return path to close the circuit. Strictly speaking, your household power would function without the ground wire, and many light appliances do so (hint, they only have two-pronged plugs).

Our bikes do not (and cannot) provide an independent ground path, because they are insulated from the Earth at virtually all relevant times - by the rubber tires. If your bike was running while on the kickstand or center stand, it would be grounded. More often the only ground path from your frame to the Earth is the rider's leg (if he doesn't have rubber soled shoes).

So the "ground" path on our diagrams is really just a return path to close a circuit, and not the "ground" leg of a home wiring system.

 

[jesustheplumber]

The battery is not grounded to the frame. The connection between the battery and the frame is to "ground" the frame to the battery.

my battery is grounded to the frame. in my bike and my truck. i was pointing out that the bikes use the frame as a secondary "ground" even when they have a "nuetral" wire, just as the wiring in our houses use the earth as a secondary ground even though they have a neutral wire.

In houses, the ground wire is separate from the return wire (e.g., the third plug on an outlet). This wire (usually green) runs along the return path of a circuit but then ties into a grounding system like pipes or some other metal path that reaches into the Earth. Hence the name "ground."

The ground path is there to provide a surge or short with a faster route to the Earth than the return path to close the circuit. Strictly speaking, your household power would function without the ground wire, and many light appliances do so (hint, they only have two-pronged plugs).

i realize theres two wires. i have ran wires through many peoples homes. but the ground wire and the neutral wire go to the same place(just like the frame and neutral wire on my bike). check your breaker box.

More often the only ground path from your frame to the Earth is the rider's leg (if he doesn't have rubber soled shoes).

human skin is actually a great insulator and 12v wont pass through it. go touch both terminals on your battery

 

[MisterCinders]

i realize theres two wires. i have ran wires through many peoples homes. but the ground wire and the neutral wire go to the same place(just like the frame and neutral wire on my bike). check your breaker box.

Any ground wire running to a pipe, does not tie back to the breaker. In a structure with one panel the ground connection is generally close to the main panel. If you run power from the main to a sub panel beyond a certain distance or in a detached structure (like a shop or garage) you have run a new ground rod to avoid the risks of long ground runs that don't protect the system.

I have seen no wire diagram that includes a ground wire or path other than the return - i.e., a third wire to soak current surges and send them to Earth.

Sometimes that return is through the frame, becaus the frame provides a return through the link to the R/R and battery. The link between the battery and frame does not ground the battery. No current runs from the battery to be absorbed by the frame. Current returning to the frame is just going back to the battery.

 

[rustybronco]

Two points.

First, Human skin is a conductor of electricity or else you could not get electrocuted.
Second, Although the resistance may be high, tires do conduct electricity as do radiator hoses.

 

[Wizard]

MisterCinders original question is valid and shows good inquisitive thinking.:-k
Many problems can occur with multiple Grounds.
The frame metal at the device would have to be cleaned of paint and scum for a good connection. Then it would rust there and cause problems.
I've seen some places where the metal spot is Chromed with a heavy nickel chrome to prevent rust. Then the spot needs to be coated with wax or Vaseline to prevent Oxidation.
Rust would create a resistive connection, and you'd have lots of them. Lots of problems.
Even though the large metal area of a frame would seem to provide a low resistance, there is still a small voltage potential between one end and t'odder.
Take these small differences into the frequency equations and you get Loop Currents,,..High Frequency Noise.:-s
Older bike with Points shouldn't have issues, but if you have a GPS,,.. Stereo, MP3 player,,.. or how about a CDI running the sparks?,,..
The worst MainFrame problems I've had to fix were often Bad Grounds.
The problems manifest as all kinds of weird symptoms.
Good Electrical Engineering insists on a Single Point Ground.
Often that's not possible and there are protocols for that.
Single Point GND uses up more wire, but less pulled out hair.
Hope this makes sense,,..

 

[posplayr]

The attached diagram shows a simplified wiring diagram with a single point ground. The very effective method of implementing a single point ground is to collect all of the ground wires shown and attached to the R/R(-) return line.

1. Stacked ring lugs with dielectric grease or
2. just soldering them all together

would be very effective.
The single point could also be bolted together at the frame as long as you minimize teh wire between R/R(-) and frame single point.

Here is a simplified diagram showing the connections for a 6 wire R/R. Just omit the Brown wire for a 5 wire R/R. The R/R has doubled up wires for both (+) and (-) so it is actually an 8 wire as shown.

The main benefit of this approach is that the R/R is wired directly across the battery (except for an inline fuse) and the only currents between the battery and R/R are the BATTERY charging currents.

 

[MisterCinders]

What do the "77777" labels mean in that diagram?

 

[posplayr]

What do the "77777" labels mean in that diagram?

I kept looking and could not figure out what you were talking about............


Then it dawned on me; that is the "pitch fork" symbol for a "frame ground"

 

[MisterCinders]

I kept looking and could not figure out what you were talking about............


Then it dawned on me; that is the "pitch fork" symbol for a "frame ground"

Why does the frame have one then? Or is that to indicate where the other pitchforks link to it?

IOW, the battery has a fork because it's connected to the frame. The load has a fork because it is connected to the frame. The frame has a fork as well, to show where paths that end in the other two forks pick back up.

 

[posplayr]

Why does the frame have one then? Or is that to indicate where the other pitchforks link to it?

IOW, the battery has a fork because it's connected to the frame. The load has a fork because it is connected to the frame. The frame has a fork as well, to show where paths that end in the other two forks pick back up.

The way you interpret it is that anything with a pitch fork is connected together via the common "frame ground".

So normally the frame pitch fork would be understood(not shown), I just wanted to be able to explicity create the current path for all return currents. Because it is normally not shown, this maybe where a lot of people get the idea that the current is absorbed into the frame. Reality is that it has to get back to the source.

 

[Normk]

Motorcycle manufacturers switched to a common harness ground about 3 decades ago mainly because it made for quicker assembly. Automobiles continue to use multiple frame grounds because of the longer runs required. The easy answer to your grounding question is that, generally, motorcycles tend to have excessive voltage drops in the common ground circuit due to the headlight load.

A quick voltage drop check between the headlight bulb ground terminal (left side of the bulb's three terminals) to battery negative with engine running and headlight on high will indicate the loss in the ground circuit. If showing more than 0.2 volts, I usually install an additional ground between the headlight ground terminal in the headlight plug and a frame bolt near the front.

The additional ground serves several purposes since it removes the headlight load almost completely from the common ground circuit, other loads which remain dependent on the common ground are at a higher voltage. In addition, the ground path is shorter for many components which ground "forward" through the additional frame ground rather than to the original common ground point.

It can be quite illuminating to monitor the direction and degree of current flow in the ground circuits of some bikes before and after adding additional ground(s).

A separate but similar subject is that of voltage drop in the insulated/positive side of the harness. Some machines exhibit quite high voltage drops in this area also but the way to reveal is to do a series of voltage drop tests in order to measure the degree and to locate the drops.

One of the most ignored means of reducing voltage drops/losses is to reduce circuit loads by use of LED or HID.

Use your voltmeter to detect and locate voltage drops in areas such as connectors before attempting to correct imagined issues through blind cleaning. Once you have a reference and location for a poor connection, revealled by a high voltage drop, the correction can be verified by rechecking voltage drop in order to determine whether the issue has been resolved.

 

[daturat100r]

The term ground prob came into use in days before motorcycles existed.Always wondered as a kid why they only had one wire going to the old milking shed before it burnt down.With reference to the bikes electrical system the frame is ground and any resistances is not good so using an extra earth harness along with change to negative earth greatly helped reliability.Positive earth systems actually promote corrosion of steels with the current flow in same direction as the oxidation reaction whereas negative earth inhibits further corrosion even though steel to copper connections are common.
Electrolytic corrosion protection is commonly used with steel in boats, structures pipelines etc