[Bulletman]

I recently purchased a Tombstone Taillight from Amazon: follows the link
http://www.amazon.com/gp/product/B000GZJYZG/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1.
This tombstone light has only 2 wires protruding from the back one is red and the other black.     The OEM brake light has 3 wires.
I was wondering how the tombstone would be attached via 2 wires only?
Do i have to modify the new Tombstone light in any way?
your help is appreciated.
Cheers

[The_Rigger]

The OEM tail light has a ground wire, a brake light hot wire, and a running light hot wire, since it mounts to the non-conductive plastic "doghouse." Your new tombstone light is designed to bolt direcly to the steel fender and ground through the mounting bolts, rather than through a wire.

You'll need to use a DC voltmeter or a test light to determine which of the bike's hot wires is which. As long as you've got a good metal-to-metal mechanical connection between the fender and the bike frame and mount the new lamp housing to the fender, you won't need a ground wire.

[Bulletman]

Thank you Rigger.
I recently also picked up 4  of the Turn signals ("retro" kind)  from Nfg and they only had one wire, as they grounded to the frame, I guess I have to make sure that I tape up the "extra" ground wire and tuck it away safely?

[barenekd]

If a loose ground wire touches something, other than a hot wire, it's not going to hurt anything. You don't have to be too careful with them.
Bare

[Arizoni]

The fender (mud guard) may work OK for a ground but just to be on the safe side I would do what I did when I mounted my metal bullet turn signals.
I got a couple of steel washers that fit the mounting stud/bolt and soldered a length of wire to it.
With the modified washer clamped with the mounting nut/bolt it serves as a good ground and can be attached to the original grounding wire from the harness.

[no bs]

let's not get old school and say "positive ground". how about "assured ground connection"? just sayin'.

[Blairio]

Perhaps a dumb question, but here goes anyway....

My old '54 Francis Barnett has a +ve earth electrical system, while my 2012 Enfield has -ve earth. Why would you have one rather than the other, and bearing in mind that everything these days (cars & Bikes) seems to be -ve earth, what is the advantage?

[Arizoni]

You make a good point no bs.
I changed my post so no one can get the idea that somehow the polarity became different.

I'll leave it to the electrically minded people to tell us if there is any advantage to a negative ground vs a positive ground.  IMO, it really doesn't matter except to say that if there is a DC motor anywhere in the system it is wound for whatever polarity the system was designed to.
If a DC motor is wound for a positive ground and someone later reverses the battery to a negative ground, the motor will run backwards.

My friends 1954 Packard was designed for a positive ground so he can't change it.  It's working fine but it is causing him all sorts of wiring problems for the new solid state goodies he has installed.  They are all built for the negative ground that all new cars are using.

[Jack Leis]

How about your starter motor. You wouldnt want THAT running backwards !

[Bulletman]

Thank you
@Rigger @ Bare @Arizoni.. Its been a busy day for me... I Just finished the final prep work for the tombstone Tail Light and Also the prep work for the turn signals. all works as intended, tomorrow first thing I will complete the electricals and then Finish the Swingarm Project and take her out for a ride.... I'm keeping my fingers crossed That Mattsz also had success with his Swingarm

[Ice]

Perhaps a dumb question, but here goes anyway....

My old '54 Francis Barnett has a +ve earth electrical system, while my 2012 Enfield has -ve earth. Why would you have one rather than the other, and bearing in mind that everything these days (cars & Bikes) seems to be -ve earth, what is the advantage?

 Positive earth vehicles are less prone to rusting.

[mattsz]

Positive earth vehicles are less prone to rusting.

Wait... what?  Could this be true?  Or are you pulling our leg, Ice?

Bulletman - so far so good... stay tuned!

[no bs]

the major advantage to negative ground is it's a standard everyone now uses. anyone who has worked on a positive earth vehicle has probably seen a sticker warning of polarity(and hopefuuly not ignored it!).

[The_Rigger]

Positive earth vehicles are less prone to rusting.

...Because they often catch fire first. 

[Ice]

Wait... what?  Could this be true?  Or are you pulling our leg, Ice?

Bulletman - so far so good... stay tuned!

No joke.

 Kind of hard for positively charged iron molecules to rust.

http://www.howstuffworks.com/question445.htm

 In positive earth electrical systems the charged electrons flow through the metal bits (insulated by paint) to the appliance be it a coil, headlamp or whatever and the discharged electrons flow back to the source through the rubbery insulated wires.

 In the current ( pun intended ) negative earth system on nick in the paint and the "insulation" is compromised, the metal exposed and the process of corrosion begins.

 Big ships use some sort of electrickery to positively charge some ship bits to slow the inevitable of metal parts in maritime conditions.

 As a kid growing up in the rust belt I was not alone in noticing that old cars did not rust like newer cars did and the antique cars rusted the least or not at all.

 FWIW,  today it still easier to find a rust free '32 model A than rust free '67 mustang.

 

[no bs]

the coast guard cutter i served on had a sacrificial zinc plate attached to the hull, kind of a corrosion magnet. it was something to behold in drydock.

[Blairio]

This reminds me of High School Chemistry classes, and the idea of Sacrificial Oxidation.  If you wrap (more reactive) zinc wire round a (less reactive) mild steel nail and suspend it in water, the zinc oxides, rather than the (less reactive) iron nail. So the zinc 'sacrifices' itself. I think it is the same idea with Galvanising. Even if the galvanised surface is breached, the steel underneath it should not rust.

[Arizoni]

Stirring the pot a bit, here's what the 1978 Rolls Royce Technical Manual said about the negative battery terminal being connected to the frame:

"...RREC 1978 Technical Manual:

    "...it has been found that cars wired positive earth tend to suffer from chassis and body corrosion more readily than those wired negative earth. The reason is perfectly simple, since metallic corrosion is an electrolytic process where the anode or positive electrode corrodes sacrificially to the cathode...."

http://rroc.org.au/wiki/index.php?title=Technical:Polarity

 

[Ice]

Nah,,,no pot stirring mate,,,we are talking technical not political.

 Interesting page from the owners club.   The single most notable technical point there is the importance of grounds.
 The same car with the same bad grounds as alluded to in the club quote is going to suffer corrosion at the same places regardless of the polarity of the electrical system.
From the same article
“All Rolls-Royce cars built prior to the 1940 war, had the negative pole of the battery connected to the frame with black wire connections (plural)throughout to the frame. It is also called negative earth. For some reason, of which I am not aware, the company reversed this procedure when they resumed production after the war”
  So in other words pre war Rolls had the negative wire go from the appliance and to the frame instead of through the body to the frame like modern cars.

[Bulletman]

 
Thank you guys..I got a lesson in Electricity as well...Where else can you find a awesome forum like this one....

[heloego]

So have you mounted it? The pic at Amazon looks good, but I'm wondering about the quality and fit.

helo

[Bulletman]

So have you mounted it? The pic at Amazon looks good, but I'm wondering about the quality and fit.

helo

Hi Helo,
Yes I did mount it, I'm attaching a picture of the fender. I will attach another pic tomorrow, (the fender is now back on..I was having wobblingb issues, which are now resolved)
Cheers.

[heloego]

Thanks, bro. Looks pretty sharp! A little mass, but not as massive as the OEM doghouse.

I've also considered the NFG Tombstone model.

   http://nfieldgear.com/enfield-store/led-tombstone-tail-light.html

I definitely like the look, and can do the internal electrical mod myself, but it seems a bit expensive.
Anyone here had any experience with that unit?

helo