Re-building a Lucas ACR18 Alternator

[awemawson]

I recently replaced the alternator on my 1979 Ford 4600 tractor that I use for hedge cutting. I don't  think it's ever charged while I've owned which is since 2014 - I just top it up using a mains charger. Well in a fit of enthusiasm having finished this years hedging I decided to 'sort it'

Originally this tractor had an alternator with a separate regulator, and had been re-wired for the Lucas ACR18 and the lack of charging was due not only to a faulty alternator but also problems with this re-wiring and also a genuine fault in the fuse box. One of the 'Lucar' 1/4" spade lugs had completely corroded off and the live wire was floating about  Fault finding wasn't really aided by the Ford 4600 wiring diagram which shows a single fuse whereas there actually are twelve 

Anyway once the wiring and fuse issues were sorted I decided for expediency to fit a new alternator however as the same unit fits both my Ford tractors I'm going to re-furbish the dead one as a shelf spare.

The bearings sound and feel like gravel, and no doubt the various electrical bits are either  blown or not in the best of condition, but so long as the rotating field coil and static 3 phase stater were both continuous and not shorting to ground it could be brought back to life (hopefully!)

So this morning I removed it's end cap and made some basic measurements to convince myself it was worth buying the bits to re-build it. Happily both coils 'seem' fine so I have ordered:

New Bearings,
New Commutator,
New Brushes,
New Internal Regulator,

Fortunately all this is available as a kit on eBay including various links for the princely sum of £23 - or about 1/3rd the price of a new alternator.

So this is the state of play so far - I won't dismantle any further until the bits arrive so watch this space !

[vtsteam]

Looking forward to this one. 

[John Rudd]

Andrew,
Are you giving it the full works? Shot blast the casings etc?

I have one that I started, got as far as stripping down…ran out of cash…

[awemawson]

Yes that's the plan John 

[vintageandclassicrepairs]

Hi All
This brings me back to the Eighties where not a week went by at work when somebody would bring in one of those
alternators into the electrical workshop for repair 
The Ford factory was next door but one from the power station where I worked, (Dunlop tyres between) so a high proportion of workers drove Ford models
The usual problem was regulator failure,
There was a large crate in one corner of the workshop under the stairs full of donor Lucas alternators and starter parts (mostly junk !!)

John

[awemawson]

At long last the rebuild parts have arrived so having checked that they seem to be the right bits I committed to further dismantling.

Many pictures I'm afraid as I wanted to document the order bits came off and the position of various links and soldered joints. So firstly off came the pulley and fan noting that there is a woodruff key and a recessed spacer behind the pulley pressing on the bearing. Then it was a case of removing the regulator, rectifier and brush assembly along with all the associated links.

Once the 'back end' was disassembled I was able to part the front and rear covers and attack the bearings.

[awemawson]

I ended up having to press to he rotor shaft out using the 60 ton press and once out I could tackle the bearing retainer. I always find those spring clip retainers a pain !

Once apart I was able to grit blast the end frames - they came up well but are not perfect -there is some remarkably tough paint (or baked oil more likely) in some of the nooks and crannies.

Starting to re-assemble the end frames and rotor I was getting rubbing between the rotor and stator which proved to be minute burrs that I'd raised holding it in the vice to remove the slip ring. A smooth file soon sorted it out but it just shows how small the clearance is between these parts.

[awemawson]

The nylon brush holder was extremely grubby so it got a light grit blasting and has come up well.

I've yet to refit the rectifier (has to be soldered) the regulator, brushes and all the links but I've had enough for today and don't want to make mistakes.

Play will resume tomorrow !

[RotarySMP]

Why do the British like warm beer?

Because Lucas also made refrigerators 

[awemawson]

A misconception.

We don't like warm beer, we just don't like beer so cold that you can't taste it !

Now lager as opposed to proper beer (bitter) CAN be cold and is what many 'not of these shores' think of as beer, but it isn't. The temperature that a decent draught bitter is served is extremely important. My favorite (Harvey's Best) is what is called a 'live' beer - it continues to ferment in the cask - so not only is the temperature of serving important but so is the cellar temperature for storage. You would be amazed at the difference between pints served at different watering holes despite having been brewed by the same brewery, and all that differs is the cellar !

[Spurry]

Notwithstanding the beer discussion, a very useful and informative description of the alternator rebuild. 

[awemawson]

So this morning I soldered in the rectifier, installed the new brushes and set all the links connecting them to the regulator and brushes. Checked, double checked and was sure that there were no errors.

Then I set up a simple bench test - small 12 volt battery from an old UPS, 3 watt bulb from +12 v via a switch to 'Ind' terminal, with the obvious main + and - leads from the alternator output to the battery. Clamp ammeter round the alternator output lead, Fluke DVM across the battery - 'ready to test'

With my Milwaukee impact driver with a 22 mm socket I set it spinning. Did we charge NO  The battery volts were going down not up - argh what have I done wrong 

Some time looking at photographs that I taken, and from on line resources particularly this one:

https://www.lrsoc.com/forum/forum_files/Lucas%20Manual%20A1-5.pdf

But I could find nothing wrong with what I'd done - I was about to re-install the old regulator when I thought hang on it's not the battery is it. Oh yes - another ex UPS battery - (even smaller this time !) hooked up and guess what - we start charging and the volts top off at 14.6 as they should.

Funny how you always doubt what you've done then it turns out to be something else 

So when I can find a big enough battery in a reasonable state that I can drag onto the bench I'll give it a full test - the alternator is rated at 45 amps but it only took 500 milliamps to raise the  7AH UPS battery to 14.6 so a very modest load.

Then no doubt it will be sealed in a poly bag and sit on a shelf until my descendants put it in a skip 

**** Later Note ****

I managed to scrounge a battery recently removed from a friends Motorhome that he keeps here - quite a sizeable battery. Lashing it up, initially it measured 12.6 under no load so by no means discharged. Setting the alternator spinning it started charging at about 15 amps rapidly dropping to about 4.5 with the volts at about 14.25 and slowly rising so I'm confident that the alternator is fixed and working and controlling it's charging rate.

[tom osselton]

Why do the British like warm beer?

Because Lucas also made refrigerators 

Come on!
 Nobody likes a Chilly Willie!

[tom osselton]

Nice to see you fixed it.    (not warm)
It looks like the rectifier off a Brit motorcycle but they had a zener diode.

[WeldingRod]

Whew!  For a minute there I thought you had a Selenium stack rectifier from the dark ages!  Geeze those things stink when they die...

Sent from my SM-G715A using Tapatalk

[awemawson]

This alternator dates from the early 1970's so although they are silicon diodes in the three phase bridge they pre-date the later style that press into an interference hole in a heat sink mounted on the rear on the alternator.

I know what you mean about selenium rectifiers  - frequently used in 405 line TVs deriving HT rails directly from the mains - so late 50's early 60's. They had the advantage that you could rebuild them on a longer bit of studding with more 'selenium washers' to increase the voltage rating. How we didn't kill ourselves in the Radio Club at school still remains a mystery 

[vtsteam]

I remember those rectifiers. We used to get junked TVs from the dump and strip them for parts. We particularly like Zeniths because they were hand wired point to point -- longer useful leads and lots of terminal strips. And I remember tube (valve) testers in drug stores, with little boxed tubes in the cabinet beneath.

[ddmckee54]

Careful there guys, you are REALLY dating yourselves with those remarks.  Next thing you'll be trying to tell us you remember using the shoe fitting x-ray machines.

[awemawson]

The inbuilt solid state regulators of Lucas alternators have always been a bit of a mystery to me. I understand the basic method - switching rotor current on and off to control the output voltages - but the subtilties evade me until I found this interesting article on the web:

  http://www.worldphaco.com/uploads/HISTORICAL_LUCAS_ALTERNATOR_REGULATOR.pdf

[John Rudd]

Interesting read that article on Lucas regs….