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TR2/3/3A TR3A Alternator

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CaptRoy

Jedi Hopeful
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I know this has been posted many times...But I'm ready to start the conversion. What is the best way to go for an alternater on a TR3A. How do you install the wiring and is there a decent kit available. Do I have to give the amp gauge, if so is there a replacement such as a clock to fill the hole in the dash...
Thanks guys

Capt Roy
1961 Tr3A TS71469L
 
Hi Capt Roy,

No, you don't have to give up your amp gauge. You do need to convert your car to negative ground, which simply means reversing the connections at the battery (when it comes time to hook it bakc up) and on the amp gauge and at the coil. Unless you have a positive ground radio installed, everything else should work fine and your headlights will actually be bright enough to drive at night! /ubbthreads/images/graemlins/driving.gif

Here's a website that shows installation on a TR3 https://triumph.daveola.com/Album/Alternator_Conversion/
He also describes a kit he bought and where he got it (I have no personal knowledge of that vendor).

If you are a member of the Vintage Triumph Register (www.vtr.org) there are good instructions at their website, in "members only" area.

I installed a Delco 7127-3 in my TR4, bought locally, and it wasn't difficult, but I do have some fabricating and welding skills that came in handy. There are some photos of my installation at the link below, by my signature.

The 7127-3 is a "three wire" alternator that allows using the amp gauge, if you wish. A "one wire" alternator might be a little easier in some respects, but the amp gauge won't work and they generally aren't recommended, I forget the details why, but it made sense at the time I heard it.

Hopefully this will get you started.

Hey, I think we need to put an alternator conversion article in the BCF's Knowledge Base! What with all the handy folks here on this site, I'm sure we could put together something really instructive and helpful.

/ubbthreads/images/graemlins/cheers.gif
 
Thanks Alan,

I don't think I will have a problem mounting the alternator it's the wiring that concerns me as I'm just not a great electrician. I may need to get a little help for this. If I had a wiring diagram it would not be a problem.

I will go with a three wire and I read about yours. You did mention it could be a little tight for a TR3 but I will work with that. I'm going to go with the same as yours with small belt.

I have already converted to negative ground.

I think this would be a great thing for the knowledge base also. I plan to take pictures and document the modifications I make.

Thanks and if anyone can make a basic wiring diagram for the three wire alternator I would appreciate it.

Capt Roy
1961 Tr3A TS71469L
 
Forget the 7127, it's too big and need to be cut to fit correctly. Most use the Delco 10si because it's smaller and can be had in the both 1 and 3 wire hookup to preserve your amp gauge. It's also important that you get the connectors on the housing a "3 oclock" this puts them where the TR expects them. The 10si is also "self excited" so it will put out juice at low rpms.

The easiest hookup is a 1-wire unit; all you do is hook up the one wire to your battery (+) terminal. But you lose the alternator. Good if you can find a matching volt gauge though.

Mechanically a litttle fussy but not much. 3/4" wide pulleys are available from the alternator source/ebay for around $15. The belt you need is gates/napa/carquest #24379 for a 3/4" pulley.
 
[ QUOTE ]
Forget the 7127, it's too big and need to be cut to fit correctly. Most use the Delco 10si because it's smaller and can be had in the both 1 and 3 wire hookup to preserve your amp gauge. It's also important that you get the connectors on the housing a "3 oclock" this puts them where the TR expects them. The 10si is also "self excited" so it will put out juice at low rpms.

The easiest hookup is a 1-wire unit; all you do is hook up the one wire to your battery (+) terminal. But you lose the alternator. Good if you can find a matching volt gauge though.

Mechanically a litttle fussy but not much. 3/4" wide pulleys are available from the alternator source/ebay for around $15. The belt you need is gates/napa/carquest #24379 for a 3/4" pulley.

[/ QUOTE ]

A 7127 alternator IS a Delco 10 SI, so I don't know what you're trying to say here. As far as the one wire units go, they are self exciting alternators that rely on the residual magnetism of the rotor to get energized. This takes initially about 2000 rpms of engine speed to initially get things going. Also, if the alternator sits too long, the residual magnetism in the alternator will dissipate and the unit will have to be externally excited by grounding one of the brushes through the "D" shaped hole in the back of the alternator while the engine is running.

The wiring for the three wire unit is essentially is no more complicated then the original generator (actually easier), and retains all of the original ignition light and ammeter functions.

One other item that I feel is important in hooking up the three wire unit. Many instructions say to hook a jumper from the positive post on the back of the alternator to the sense terminal of the regulator plug. I forget which one of the two it is offhand. This will work, but the sense terminal is designed to sense the voltage actually getting back to the battery, and not what's coming out of the back of the alternator. There is always some resistance along the way, so the regulator really wants to know what's happening at the battery. /ubbthreads/images/graemlins/driving.gif
 
I somehow read the model wrong as 7271 which is a 12si (bigger) 78Amp unit that some have used. The 7127 is a 10si 63Amp unit That I have for my 4A.

Good point on the idiot light and ampmeter connections but, I was just trying to point out that a 1-wire is the easiest way to hookup an alternator and have it work.
 
Well, the 12SI is physically the same size as the 10SI. It is designed to put out more current. The rectifier assembly has larger capacity diodes, and the rotor and stator have more windings. Also the fan is a plastic enclosed affair that pushes more air through the assembly. Not until the 15SI series do the units actually get physically larger.

BTW, I only know all this stuff because I work for a large electrical remanufacturer. /ubbthreads/images/graemlins/cheers.gif
 
[ QUOTE ]
BTW, I only know all this stuff because I work for a large electrical remanufacturer. /ubbthreads/images/graemlins/cheers.gif

[/ QUOTE ]

Hi,

Since that's the case, can you suggest a smaller/lighter alternator that has about the same mounting dimensions? The 7127-3 (or whatever we call it) *is* pretty large and heavy. I'd guess it's about the same weight as the original generator, and although it's not long, it's larger diameter. Since the Delco is so common, surely someone makes a smaller/lighter replacement that puts out between 45-65 amps. Any suggestions?

/ubbthreads/images/graemlins/cheers.gif
 
Capt Roy,

Here's your wiring diagram.

Alan,

The reasons for not using a one-wire are: It cost more, it doesn't work as well, and it is not one bit easier to install in a TR than the three-wire.

If you are building a car from scratch, it might be helpful, but you already have the wires needed for the three-wire. If you know enough to remove them, then you know enough to go ahead and hook them up, and it is just as easy to use them as it is not to.
 

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Thanks for the diagram. I have printed it and saved it to dish. Revington uses a 45 amp RAC002 for their kits, but they are pricy...

Thanks again...

Capt Roy
 
If I may chime in..There is a web site for "mad electrical" that explains the 1 wire vs 3 wire difference. It all boils down to a 1 wire will not compensate for voltage drop in the harness, as it senses voltage at the back of the alt. a 3 wire will sense voltage wherever the sensing wire is attached and the alt will put out enough volts to get 14.2[about] at that point..
 
Thats a good summary Bfitz. /ubbthreads/images/graemlins/thumbsup.gif---Keoke
 
I have converted my LBCs to alternators mainly for higher reliability. I've retained all the old parts and left the wiring harness intact so future owners can put things back to the original configuration if they want originality.

To achieve this you may wish to consider using an old regulator control box as a junction. Basically you gut the insides of a dead one and make all the appropriate wire connections inside the old control box thus leaving your wiring harness intact and the appearance under the bonnet "correct" (apart from the alternator itself).

I'm not a big fan of ammeters. These were OK when you had a 22 Amp generator putting a nominal amount of current through the wires. Once you convert to an alternator you'll (probably) have the potential of 63 Amps going through those 40+ year old wires behind the dash and through the firewall. A volt meter can give you as much information as the ammeter and is significantly safer. However, it's your car, do what seems right to you.

I believer that if you Google you'll find several possible alternate alternators for LBCs. Some fit better than others. The Delco 10si is probably the most common and it's what I have on the GT6. I have a Motorola on the Mini and this is equivalent to a Bosch model. I've also seen certain Triumph pages where Mitsubishi alternators were used. If you have room though... it's hard to beat the Delco as they are available EVERYWHERE and can usually be bought rebuilt with a lifetime warranty for under $50.

In closing... I have a project in the back of my mind to build/repackage an alternator in the Lucas C40 generator housing. There is a product in the U.K. that already does this but it's WAY too expensive for most of us. See:
https://www.racemettleltd.co.uk/dyn.html
You can order this through Moss Europe but I believe that with shipping and accounting for the exchange rate the current price is around $700.
 
[ QUOTE ]
...I have a project in the back of my mind to build/repackage an alternator in the Lucas C40 generator housing...

[/ QUOTE ]

That would tempt even me to think about switching. I'm not obessive about originality but since the only big advantage to an alternator in my situation is reliability (I guess) then I have prefered to keep the original look (and carry a spare on long trips).

As for voltmeters -- certainly seem more useful than an ammeter in this instance. As I recall Jags of the 70s had Smiths voltmeters, probably others too.
 
I recently acquired a Smiths voltmeter. I was very surprised how it operates. Other (modern) volt meter manufacturers have a fast response movement. The Smiths volt meter is a bimetallic unit like the temperature and fuel gauges they made after 1964. I guess it was cheaper for them to make them operate that way but it's still a bit surprising.

I'm open to suggestions on my alternator project. The problem has been finding a suitable donor alternator with a stator smaller than 4" in diameter. Almost everything I've come across with decent output has used stators about 4-1/4" in diameter and that's too large to fit inside the C40 housing (even bored out). I've considered motorcycle alternators but most are integrated in such a way to the engine that they'd be hard to use. Most have too little power also. Those that meet the requirements are too expensive (even used) to cut up for this project.
 
[ QUOTE ]
[ QUOTE ]
BTW, I only know all this stuff because I work for a large electrical remanufacturer. /ubbthreads/images/graemlins/cheers.gif

[/ QUOTE ]

Hi,

Since that's the case, can you suggest a smaller/lighter alternator that has about the same mounting dimensions? The 7127-3 (or whatever we call it) *is* pretty large and heavy. I'd guess it's about the same weight as the original generator, and although it's not long, it's larger diameter. Since the Delco is so common, surely someone makes a smaller/lighter replacement that puts out between 45-65 amps. Any suggestions?

/ubbthreads/images/graemlins/cheers.gif

[/ QUOTE ]

OK, this sounds like something to pursue. Fortunately, I have a spare TR3 generator sitting here I can use for reference. I'll try to come up with something that will fill some of the below parameters.

1. Smaller diameter then Delco 10SI.
2. Easier mounting. Try to use as much of the original hardware as possible with little modification. Some will be necessary.
3. Minimum 45 amps. I would prefer 55-65.
4. Possibly one with 15mm shaft so the original wide pulley can be fitted without modification.
5. A unit with a good history of few problems.
6. Wiring that is compatible with the TR system as the Delco 10SI is.
7. Readily available at a reasonable price.

If there is anything I missed, let me know. As far as I can see, it will most likely be a Japanese unit (Nippendenso or Hitachi) from a a common Japanese car such as a Honda or Toyota. I'd like to stay away from the Bosch units, as they are harder to procure for a reasonable price and are generally less available. /ubbthreads/images/graemlins/thirsty.gif
 
Sorry - displaying my ignorance here - How does it compare in size to a TR6 unit? I just bought a monster alternator on ebay (96A) that's the same size as my stock one. It was $85, and the guy has more.

NFI, but it was really cheap...
 
Martx-5, out of curiosity... is the shaft really 15mm or is it 19/32"? I've never mic-ed the bearings in a Lucas generator so I certainly don't know. I just remember the pulley nut is tapped for an odd size and that I didn't have the correct lock washer among my collection when I broke the Lucas one.
 
Yes, the shaft is 15mm. I measured it at .590. 19/32" would be .59375. I'll go and measure the threads, but I suspect that they are similar to the threads on the Delco and Ford 17mm shaft where they measure 17mm, but have 20 threads to the inch. It's really mixing metric with English. When we get dies for chasing the threads, we have to order .669 x 20...not exactly a size you'll find at Home Depot.

Edit: OK, I checked the size of threads on the end of the shaft on the TR3 Lucas generator I have. They step it down from 15mm (.590) to 7/16"-20. Not exactly a common size for nuts and washers, but they are available at McMaster. A good hardware store might have them also. One has to ask why Lucas didn't go to 1/2"-20?? /ubbthreads/images/graemlins/hammer.gif
 
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