TR2/3/3A Rebuild generator or go w/ alternator for TR3a

[tomshobby]

My TR4 and GT6 had generators. I never had any trouble with them. I ran them both hard and the GT6 saw red line a lot. I never had the voltage fluctuations with them like I have with the TR6 when the headlights are on.

 

[Twosheds]

Once upon a time when all there were only generator we did not think there was anything wrong when the engine RPM's slowed and the lights went dim because the voltage output dropped.
When more and more demands were put on the electrical system it became more problematic. One big difference is that at idle a generator voltage output will drop enough that the battery will be discharging until the RPM's are increased again.
With an alternator, if all accessories are off, it will charge at an idle because it will have full voltage. At least that is the theory and not how my Lucas alternator seems to work although my GM alternators did.

Since you're interested in this stuff, Tom, this is what I read somewhere about why alternators can produce their rated voltage at idle and generators can't:

The max RPM a generator can take without failure is limited by the commutator/brush set-up. The brushes bounce along the rough segments of the commutator, so they put a large diameter pulley on generators to keep them from rotating too fast when the engine is at redline. Of course, this means that the generator RPM at engine idle is low, below generator come-in speed, and the reverse-current relay in the regulator opens the circuit and the battery runs the loads.

Alternator brushes ride on smooth slip rings because the rectification is done by the diode circuit, so an alternator can run at high RPM without problems. Also the alternator brushes don't carry the output current like generator brushes do, they carry only the small field current. They put a smaller pulley on alternators and the alternator RPM at idle is high enough for it to produce its rated voltage.

I've never looked at a car alternator pulley and generator pulley to compare diameters, but it's evident on airplanes.

I see I've put some of you to sleep. Wake up!

 

[prb51]

I like originality but fall on the side of practicality. I like to really 'see' at night and the old generator lights have that nice warm yellow glow reminding me of yesteryear but can't see a [censored] thing.
I have an alt. with halogen lights (advance auto wire headlight kit) with a shunt on the original gauge and it is literally like night/day. Tail lights are brighter, dash lights are brighter etc. etc.

 

[prb51]

p.s.
I wired the alt. to the regulator for looks. The regulator is gutted/grounded and the removable top where the innards use to be makes a nice place to store points and the carb mixture wrench.

 

[Andrew Mace]

I currently am running a "cheap substitute" generator from Moss in my TR4. So far I'm not having any issues, but would be <u>really</u> interested in hearing the kinds of problems people have had with these generators.

I've yet to hear details of problems with these units. On the other hand, I wonder if they'll be rebuildable 40 or 50 years from now.

The original (date code 11 61) generator in my Herald gave up around 2005. Had it rebuilt and it's been just fine ever since...even at night, in the rain, with the heater, H4s and AM/FM radio doing their best to tax the old C40! /bcforum/images/%%GRAEMLIN_URL%%/laugh.gif