[Stephenscity]

OK I'm confused nothing new. Was giving the N a goingover and noticed that instead of being positive ground battery was hooked up neg ground. every thing seems to be working fine Gen putting out 11 volts reg stepping it to about 6.3-6.4 everything seems ok but confused. Why would someone reverse the system? and how??Since someone did this is there anything I need to be aware of?
Cris if you can help remember I need it simple :lol: :lol: :lol:

 

[soundguy]

here are a few issues I see.

1, if it is a side mount 8n, which I believe it was, you can actually hook it up as vegative ground and be ok as you can also set the coil to the correct polarity. the front mounts aren't as easy to do this with.

change of polarity is as easy as repoalrizing the generator, and then swapping wires at the battery and ammeter to make it read the correct direction.

the reg uses a field controled output.

there is NO WAY the gen is putting out 11v and teh reg is 'stepping it down' to 6v.

the reg is not an output device with limiter capability. it provides field current to the generator in order to make the genny make the proper voltage..

now.. that said. in an old system with a vibrating regulator the breakers in the reg and brushes in a genny usually plays havoc with a cheaper consumer grade meter.. especially one with a slow sampling rate. reason for this is it is an averaging system. reg has a field contact and a field resistor. when contacts are open, field current for genny goes thru field resistor and it is barely enough for the genny to make any current / votlage at all.. just enough to keep it from swinging negative. when contacts are closed, field current is at max, and voltage goes up.... when this happens, the vreg then opens the field contact once voltage is above cut in and current is up. it does thins many many times a minute.. that's why it is called a vibrating or mechanical regulator. it goes from sub bat voltage to max many many times producing an averaging effect. during times of high demand on the battery, the field contact moves slower thus delivering more average current. during times of low demand, the field contact may be open more.. etc.

in any event.. consumer grade meters have a pretty slow sampling window .. especially auto range meters. what they are doing is taking a voltage reading every now and then. sampling rate may be slower than ever second.. might be faster. what usually happens is the meter happens to sample during that split second when the field contact is close dmaking max charge... in the end.. battery sees the 'average' not the peak..thus the reading from the consumer grade slow sample metter is misleading at best.

 

[Stephenscity]

THANKS got it. Is there any advantage or disadvantage to either way other than politically correct?

 

[soundguy]

on a theoretical scale.. yes. on a practical scale, maybee, IF a front mount. on a side mount.. very little practical difference.

here's the deal.

positive ground.. center electrode in the spark plug is negative.

electron current flows negative to positive ( electrons have less mass than protons! )

that means the spark actually jumps from the center electrode tot he positive outter ring and / or lil feeler on the tip of the plug.

now.. a little electrical phenomenon called thermionic emission ( google edison effect ) means that it is easier to 'boil' electrons off a hot surface vs a cold surface.. thus it's easier, on a theoretical scale, to boil electrons off that hot center electrode as it is insulated from the head sink of the block via the insulator.. heat range of the plug will be determined by insulator, and plays a roll. also easier to get he spark to jut from the flatedge at the side of the angle.

all this means is that positive ground throws sparks off the center electrode a hair easier than negative.

that said.. a good negative ground setup will be fine. by the time HEI came out.. the small theoretical micor percentage difference in positive or negative ground was meaningless.

one more issue.. coil polarity. there is a low ohm primary.. say 1-3.25 ohms.. and a high ohm secondary.. say 4k ohms

when wired with incorrect polarity you have the issue of a large resistance plus a small resistance in the circuit.. again.. it's a REALLY SMALL difference.

front mount coils , due to their physical structure, cannot be reversed to run at correct polarity for negative ground. round coils can. thus on a front mount that was 6v.. I'd run it positive ground for 'best' results. best spark.. best arangement of secondary on coil.. etc.. etc.

that clear it up any

ps.. you know you are in trouble when you ask an engineer to explain something

 

[Guest]

that clear it up any

ps.. you know you are in trouble when you ask an engineer to explain something

Yep, thats for sure. Thats why I always ask for your help in 3rd grade terms :lol: :lol: :lol:
Either way you always manage to get us going and its greatly appreciated.........

 

[soundguy]

and the hyds help you have given me has always been right on mark as well!

every tiome i drive my ford 4600 that had the leaking hyd fitting and line on the power steering I remeber the help and parts you sent asap to get her back mowing again.. and of course.. they fit and worked perfectly, even though I installed them..

that's half the battle.. just knowing who to ask

 

[Stephenscity]

HUH?????? Just kidding Yea a little scarey but I think I got it I just couldn't understand why someone would go to the trouble to switch it but from what I found switching it wasn't really that hard. Think I'll just leave it alone since it is working so well.Again Thanks!!!

 

[Guest]

that's half the battle.. just knowing who to ask

As in todays loader scenerio ??????????????? So true

 

[Stephenscity]

Another quick question. Been a lot of years can't remember what a 6 volt system battery voltage should be at?I'm at 6.3 is that about normal and when I replace the pully should I concider the same size or one a little smaller?

 

[soundguy]

6.3 is nominal volts for a fully charged 6v batter. .. 1266 is nominal for a 12v bat.. etc.. etc.. 2.1v per cell. fully charged.

since work rpm is brisk.. oem pulley is fine.. could go smaller.. but no need to. get too much smaller and you stress the belt on that tight angle

 

[Stephenscity]

Thanks Cris!!! That helps alot!!!!

 

[Jason1Pa]

This has been a interesting topic

 

[soundguy]

postback

 

[Stephenscity]

Don't know if this is relevant or not but maybe the old guy that reversed the pos grd knew something practical. Have had a number of the old 6V pos grounds over the years and we all know how they seem to crank hard in winters cold. Well now having come through a pretty cold winter here want to tell ya I have never had a 6V turn this well. It has cranked all winter almost like a 12v.and have had vertually no voltage loss out of the battery. My first time at this but got me to thinking if this is making the difference oh it still has the straight weight 30 oil in her too.Just thought I'd pass this along.

 

[soundguy]

6v has a small help on the 'spark' side.. but that's about it.

it's called thermionic emission. essentially it's easier to boil electrons off a hot surfce than a cold one.

on positive ground, the theory was it was easier to generate a spark ( hotter spark anyway ).. etc.

also known as the edison effect.

by the time 12v ignitions came along.. adequate voltage for good spark potential wasn't a problem.

keep in mind the old 6v systems likethe front mount fords used.. the coil wsn't even a 6v coil.. but rather about a 4 or so volt coil.