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TR2/3/3A Generator postmortem

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TexasKnucklehead

Jedi Knight
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To recap my generator failure, some may remember my trip west this summer in the TR3. It was hot. I left Houston as the sun was setting and drove through the night to El Paso. We slept the day away and waited for the temperature to drop below 100 before heading through the night again, making it into Los Angeles in time for morning traffic. By dark, we were on our way to San Fransisco and stayed a whole day attending a wedding before heading up highway 1 into Oregon by early morning. The next afternoon we drove to Lake Bay Washington (Home), just outside Seattle. As we were within a dozen miles of our destination, I heard noises I assumed to be the generator. They seemed worse at idle, and switched on and off with purpose as if synchronized to the charging of the battery. Since we planned to stay 2 nights, I took the time to swap out the generator with the one I had in the boot. I noticed flakes of busing material and a little play, but was glad it didn't seem to have any serious damage. We made the return trip without incident, driving at night and during the day, often hotter and sometimes in the rain. -Since then I've put another thousand or so miles without trouble, all along having my "barely defective" generator in the boot. I wrote off the failure as a combination of heat, over use, and perhaps a belt too tight.

Today I finally got around to taking apart the generator, expecting to replace the bushing and having it function like new. It appears the armature has lightly rubbed against the magnet at some point. I removed the brushes, and cannot push hard enough on the pulley to make it rub anywhere -it always spins free. The rubbing is on the lower, outside magnet, as would be expected if there were excessive wear in the bearing/bush. The armature appears burned, with missing insulation, and one of the field windings is bare. Obviously, the generator failed. I would expect whatever caused the failure, to cause the same failure on the replacement, except I now run the belt much more loose. It looks like I'm going to have to make a new spare from the units I have in a milk crate. I don't think I trust trying to reuse any of my "barely defective" spare.

So why did so little play allow it to rub? Is the rub responsible for the burned wires? How long can I expect a generator to last?
 
Just a semi-theoretical guess, but I'll bet the problem was the heat and continuous use. Most metal expands when heated, but not all metals expand the same percentage.

Tom
 
I don't know anything about the old generators.
but my hats off to you for making such a long trek in your 59 3A!
that was just Bold.
 
What is the condition of the rear bearing? I have had that one fail on a long hot drive. Not sure if wear back there would be obvious by wiggling the pulley.

That rear bearing lives in a hostile environment - right up against the exhaust manifold - hence the provision to easily oil it.
 
I have always had some type of generator problem will TR3s. I figure being right next to the exhaust shortens the life. One thing I have been looking into is the geometry of the 3 pulleys that are on the belt. Every tr3 I have had and looked at, the generator is not on the same plane as the water pump and the crank perhaps by about 3/16 to and 1/8. The cockeye angle might pull different and shorten the life.

I probably got 10K on my last rebuild and when I took that apart the armature was bent. That generator was collection of parts and something I have been rebuilding on and off for years. After seeing the bend in the amatory, this last rebuild was more cautious and that generator is in my driver with about 2K, time will tell.
The new engine I built lines up real nice after I did some adjusting with washers, but that car is not on the road.

I have been working on modified bracket for the generator to put on my driver, but have not done it yet. I once bought a new Generator from Moss and in about 5K the rear bearing was wearing out. That was one of those new ones built in India. At the end of day, if you get more than 10K from a tr3 generator you are ahead of me.
 
You had a bearing bushing to wear out and it allowed the armature to rub the fields. The rubbing of course caused heat which broke the insulation down. How long does a generator last? Like a car, some maintence and it will last a long time. If you look at the outside of the generator housing underneath where LUCAS in engraved, there are some other numbers. Out to the right will be two digits. That is the year the generator was made. Hopefully that number will be around that date your car was built. You generator could be rebuilt but probably will cost more than new replacement.

Marv
 
I'm guessing an original part. As bearing loose lubrication, wear sets in. Just as engine bearings go crank starts to shift. Generators are a magnet in motion, so any play in bearings will cause mainshaft to shift and rub. How long will a generator last? Depends on use and care. Yours has been around awhile. Rebuild to original specs, new bearings, brushes and clean the center mass with a good cutting, should last as long as original.
 
I don't think your armature rubbed. It looks like the 50 year old "epoxy" insulation between the armature poles failed, and as that slung out it ground between the field magnet, field coils and spinning armature. It took out the fragile cotton field coil wrapping as it worked its way out of the end of the housing.

Now, why the 50 year old epoxy failed...? Maybe because any plastic is past it's life span at 50 years? I dunno....
 
John,
Get your glasses on (lol), look at the pictures again. Shiney armature iron, shiney field iron. Definitely metal contact. Cotton/paper insulation yes, bet the gen had a glow going at one time.
Marv
 
The geometry of the 3 pulleys is pretty close. I remember adjusting the water pump pulley and checking it all together. I agree that the rear bearing wear is difficult to observe by wiggling the pulley on the front. I like to remove the rear brush plate, remove the springs and brushes and place the plate with bushing onto an old armature shaft and wiggle the two. The previous worn out bushing -where I saw the flecks of bushing all over the inside of the engine bay, but no armature to magnet contact, shows a lot of wiggle. The 'Seattle worn' bushing shows a little wear, but not so much that I can see any oval in the bush, or a brighter, shinny side, inside the bush. I also see some flecks of bushing inside the housing, but nowhere near as many as when the previous bush failed.

I too see the shinny armature and field and it is obvious where much of the epoxy is missing, but I'm not sure it was metal to metal contact. Both surfaces are smooth as if polished, while I would expect metal to metal contact from a worn bushing to be rough and irregular. I would imagine it was very hot at some point.

This failed LUCAS generator was rebuilt from a collection of parts. The date code on the housing is not readable except for an 8 -which doesn't narrow it down much. I put it together with a new bearing up front (drilled out the rivets and bolted back together). I used a brush plate that had a bushing with very little wear. It was oiled when rebuilt, and again before I left on my trip. I did exactly the same thing for the spare that was in the boot -now on the car. The 'boot spare' was used for a month or so to be sure I trusted it as a spare before putting on the other. One generator made it to Seattle, the other made it back and beyond. -But I am a little worried that it is soon to follow the others fate.

My collection of C40 parts include several complete units, some with the usual failure of the soft metal around the mounting holes where bolts came loose. Date codes are as late as 67. I swore that the first sign of generator failure was going to have me looking at an alternator, but I just can't stop rebuilding when I have so many spare parts that nobody seems to want. I'm sure I'll manage another 'spare' but I am unsure of how long anything 50+ years might last. -And more importantly, where I might be when it fails.

I do appreciate all the differing opinions and input to my failure -though I don't think it was "my" failure. If I failed in some way during the rebuild, I'd like to correct it while the car is in the comfort of my garage, instead of half way across the country.

Jer
 
"That rear bearing lives in a hostile environment - right up against the exhaust manifold - hence the provision to easily oil"
The rear of my generator is almost touching one of the header pipes.Eventually the heat melted the solder just enough at one of the wire connectors that the red dash light would stay on.
I found a heat shield "wrap" at a speed shop that is used to proect starters on hot rods. It wraps the whole generator and is held on by Velcro. Wasn't cheap though at $80 but the generator might last a lot longer:eagerness:
 
TexasKnucklehead said:
This failed LUCAS generator was rebuilt from a collection of parts. The date code on the housing is not readable except for an 8 -which doesn't narrow it down much. I put it together with a new bearing up front (drilled out the rivets and bolted back together). I used a brush plate that had a bushing with very little wear. It was oiled when rebuilt, and again before I left on my trip. I did exactly the same thing for the spare that was in the boot -now on the car. The 'boot spare' was used for a month or so to be sure I trusted it as a spare before putting on the other. One generator made it to Seattle, the other made it back and beyond. -But I am a little worried that it is soon to follow the others fate.
Click to expand...

Jer,

Once I finally learned to rebuild my own generator including installing a new rear bushing, I had over 65,000 miles on it as a daily driver back in the mid to late 1980's. I would have replaced the rear bush with a new one rather than reusing an existing one no matter how good it looked. I also insured that it was pre-oiled by placing it in heated oil and then let it soak for 24 hours before installing.

Scott
 
Even with my glasses...still looks like the insulation let loose and polished the poles and fields as the pieces worked their way out.
 
Tex what kinda shape was the cotton wrapping in when you started? My theory is that the excess heat of that hot summer coupled with the long trip shortened the life. Plus the variable of the age of the unit and perhaps many rebuilds does not help the life span either. The shellac or plastic or whatever that stuff is on those armatures and the cotton wrapping is going break down at some point. I have rewrapped many of those fields on starters and generators with good results, but at some point the armature itself needs replacing. I see them on eBay once and awhile new and perhaps I will buy one and see if can get more life out of generator. I just like the stock look. This last one I rebuilt I have high hopes to perhaps go 50K because I replaced almost everything and used my best old stuff.
 
sp53 said:
Tex what kinda shape was the cotton wrapping in when you started?
Click to expand...

The wrapping is still OK on the other end, and I don't recall a problem when I put it together. Like you, I use the best parts I have lying around when putting one together. Before my last decent drive of the year, I scavenged parts and made a 'new' working spare. One thing I do while testing a generator, is to connect the Field and Armature together with the unit grounded, apply 12v and expect the generator to run as a motor (I measure the current draw and compare it to the others I have lying around). It should start itself, and run smoothly. I tried to use the rear plate of the recently failed armature, and it would not allow my new generator to run. It runs fine with a rear plate containing a better bushing. But then I took off the bearing retainer/front plate of the failed generator and found another more significant issue. The bearing is still tight on the shaft, but it is very loose in the front (aluminum) bearing plate. I don't think the bearing spun inside the plate, but it is obviously loose. I think the failure is due to the wear in the rear bushing, as well as the deformation of the recess that should have held the bearing in place. It's so worn, that when I try to run it as a motor, the magnets pull so hard that I cannot rotate the armature. I still have enough parts to cobble together another unit or two, but if the failures continue, I will be looking into a alternator. The one on the car now has lasted the longest so far, at about 5,000 miles.

Last week we took a short drive starting in Houston at 9am, heading to Onalaska, over to Louisiana, down to Iberia, through Orange and back home by 11:30pm. At least 600 miles. I felt better knowing I have a working spare generator in the boot. We also found that my fuel gauge reads slightly above the E when the tank is bone dry and holds exactly 14 gallons of gas. And I was truly impressed at how far a TR3 can coast after it runs out of gas at 75mph on the interstate. My wife never got out of the car, pushed or stopped laughing.
 
I think that two things you just have to find out at some point in car ownership are how far you can drive on just the battery and what the fuel gauge says when the tank is bone dry.
 
I think it's pretty common for the front plate bearing holder to wallow out. Out of the 6 generators I worked on last summer, 4 had signs that a prior rebuilder had attempted to retain the bearing better by "peening" around the bearing with a center punch.

I have also mentioned before...the rear bushings being supplied by the big 3 now days are unusable. In all 6 generators, not one was worn to a size larger than the big 3 provide as a new replacement! I wound up re-using the best bushings, as none of them were excessively sloppy. Also of note...with my TR3A, I rebuilt that generator using a new "loose from the factory" rear bushing, and that generator sparked and made a racket right off the bat. This year I was finally able to check the windings of that failed generator with my new fangled 100 year old growler, and both the field and armature were fine. It appears these generators are susceptable to loose bearings...although I am not sure why.
 
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