Spent some time over the past month rebuilding the dynamo in my '62 Mk2. Engine and head are at machine shop so I figured I'd tend to a few other needy items. Ended up replacing the field coils and brushes but everything else checked out. Replaced the massive Philips screws holding the field magnets with some stainless hex head bolts. They needed some machining to make fit correctly but sure make tightening the field coils a lot easier.

It's on my test jig for some run-in then I'll put some power to it to test. Came out looking nice... sure hope it works :-)

Tom

 

Very neat work!

 

That is nice- let us know how it works! I like your test stand too.

 

I have one from a 1964 S type 3.8 liter in case you decide to open for business rebuilding these things.

 

I have 2 more, maybe a little expensive to ship mind you.

You could get quite a thriving business doing this.

 

I think I'll keep the day job for now. I'd have to charge a fortune to make it a viable business. Took me over a month (chipping away at it) including an attempt to wind the field coils myself. Just a bunch of wire, right? Careful measurement and research I was convinced I could do it myself but failed to realize how little margin there is between the coils and the armature. Precisely laying the wire next to the other is the key to that, not something I could do by hand (as I learned the expensive way). Also painted the case twice due to likely poor prep on my part on first go-round. Did evaluate going to an alternator or even one of the disguised alternators to look like a generator but that starts a whole series of potential tweaks in a car with power steering driven off the generator. I don't plan a lot of additional electrical loads and will be moving as much lighting to LED as possible. Largest draw will be my electric radiator fan, so a 35A generator should suffice.

 

Wow, you were brave, you tried to wind the field coil by hand ! ?
That would have been done by a machine originally.
All though I am sure it would have been possible, doing that by hand would have been an almost impossible task.
I tip my hat at you for trying.

Did it need rewinding or you wanted it to look new ?
When I first saw your photos, I knew it was redone _ probably the armature too ?
I say that because when one of those is rebuilt, I've never seen one soldered, they fuse the wire to the commutator now and that's what it appears to be.
It's kind if hard to tell, it may be soldered.

 

Brave or foolish, it's a fine line. I'm stubborn when it comes to these kinds of things. The field coils are 375 ft of 19 gauge wire to get 3 ohms resistance per coil (x2 gets the 6 that you would measure for the entire generator). Given that I could buy 375 ft spools of 19 gauge magnet wire on eBay I figured the measurement of the wire length was a non-issue as the whole spool would equal one coil. All that is good and logical but as I said before I failed to realize that each strand of wire had to be laid perfectly next to the other else the whole coil was too big.

As to why I replaced them -- my power steering pump apparently had a leak and saturated the coils with oil. When I took them out the tape crumbled off and showed, in addition to being wet with oil, that one of the coils had quite a bit of missing insulation on the wires. When I tested my generator I was getting a reading of about 5 ohms, which implied that there may have been a short somewhere. I originally tried cleaning off the oil and using some insulating varnish on the missing insulation, but when I re-taped the reworked original coils I could not get them to fit compactly enough. As I tried to squeeze these into place I shorted some wires and ended up scrapping that attempt.

I didn't do any soldering on the commutator only machined down the copper a bit and carved out the spaces between the copper contacts as per the Jaguar shop manual. I also painted some insulating varnish on the wires just for good measure. Electrically the commutator checked out okay.

 

I thought you had the armature rewind too.
If you don't mind me asking, what was the cost to get the field coils redone ?
Just curious ???
At any rate, it looks bran new now !

 

coils were $150 from Star Auto Electric in California. They do not wind them themselves but happened to have them in stock.

 

Star auto electric, I am familiar with them. Excellent business.

 

That's not that bad.
I think a custom rewind job would be at least double that.
I rebuilt a Porter Cable commercial belt sander in high school _ the armature was toast.
It was not inexpensive to have it done, but the machine itself was gem.

Porter Cable 503 locomotive heavy duty belt sander 3" x 24" | eBay

 

I'm pleased to report that it works, but not without some additional fiddling. Polarized the generator then tried to get voltage out of it, initial reading was zero. Trying the test to make it turn like a motor showed that it worked and was wired correctly but still couldn't get any voltage. Turns out the springs for the brushes need to have more preload than I had. Shop manual calls for 28 ounces of force to pull back the springs and mine were in single digits. Had the take the generator apart again and give the springs an additional turn to create more pressure on the brushes and viola, worked like a charm. Had fears of having to have the armature reworked, but I'd checked it and tests I could do showed it was okay. Glad to have this behind me :-)

 

 

Hi, the earth is obvious, then the larger terminal is the Armature output, and the smaller connector is the field coil, these connect to D and F on the regulator where F is the field connection.

Hope that helps, what are you wiring it up to ?

You also need to ensure polarity is correct if you have taken it off something else or are changing from positive earth to negative earth.

 

 

That's correct Ross, you will need to apply 12V positive to the armature to run it as a motor for a second or 2 to polarise the dynamo, then just connect it up.

 

 

I love people that apply this sort of attention to detail to things that cannot be ultimately seen. Kindred spirits. They are the true restorers. Not just make it look pretty on the outside & the rest be damned.

 

I'm also using a Clover Systems DRM for the voltage regulator. My Mk2 is still in process but have the dynamo on the engine with the DRM running on my test stand. All works like it should. I believe the solid state voltage regulator will be a nice upgrade overall.

Tom