TR2/3/3A Failure in the bush

[TexasKnucklehead]

I had over 4,000 nearly trouble free miles on the TR3 when I pulled the apron to have a crack in the radiator repaired. I noticed the belt was loose and tightened it so that I could deflect the belt about 1" on the longest run between pulleys. Everything was ready in time for a club ride. After about an 80 mile polar bear drive last weekend, I saw flakes of copper or brass inside the engine compartment. Closer investigation led me to believe they were coming from the generator. Removal and disassembling made me sure it was the generator bushing coming apart (picture attached).

Discussions with fellow club members made me doubt my original assessment; the fault was from over tightening the belt. Other conclusions are 1) too little oil on the bushing 2) bent, out of round or misaligned shaft. Another attached picture is from a Lucas Generator Service manual, and shows what some think is too loose a belt. Mine is that loose now, and doesn't seem to be slipping, but it has been suggested that once the belt wears a little, and glazes over, it will slip -and nobody should believe those manuals.

How tight is your generator belt, and have you ever had a bearing or bushing failure?

 

[TimK1955tr2]

Hi, I had a similar problem with my generator and also wore out a water pump pulley, probably with close to the same mileage as you. I came to the following conclusions...

1. The original-type belts have almost no stretch compared to more modern belts.
2. The amount of mating surface area on the original-style belts and pulleys allow for much less belt tension to be used then what modern-style belts may need.

I am now putting the minimum of tension on my belt, I think that original picture you posted is closer to correct. I would question how many miles people with the "high tension" adjustment are putting on their cars. I was able to get a few good seasons of driving in before problems showed up. I could see how show cars or light drivers could almost never having a problem.

Hope this helps... Tim

 

[Brinkerhoff]

That's the same generator that MGA and MGB use . I've never seen a bronze bushing fail like that unless it dried out and overheated . I agree , I don't think the belt was too tight. If the generator was overcharging and running hot that may have gotten the armature hot .

 

[HerronScott]

What's the history on the generator? Is it possible the oilite bush was not soaked in oil when it was last rebuilt?

Scott

 

[Brinkerhoff]

I usually put a dab of grease in the bush when assembling. Not a lot . I've never had one fail like this.

 

[Tinkerman]

Gadzooks! I never even thought about throwing a generator bushing. I hate do-overs so I guess I better check the tension on the belt tomorrow. I don't remember a problem of that type back when every car I drove had generators. In the shop that I worked at we used the old "1/2" of play on the longest run of belt" standard. Hmmmm, best look it up.
Thanks Jer.
Dick

 

[dklawson]

That's the same generator that MGA and MGB use . I've never seen a bronze bushing fail like that unless it dried out and overheated .

The first British car I worked on was a '64 MGB. Its generator bush failed from excess belt tension and I'm sure the bushing was probably somewhat dry also. In '64 the MGB generator pulley was of riveted construction and in the case of the car I was working on, when the generator bush failed things locked up AND the pulley split in two. One half of the pulley sailed up and dented the bonnet from the inside. Wonderful. Ever since then I've been very careful with belt tension and when rebuilding generators I soak the bushings in 30W oil before final reassembly.

 

[TR3driver]

That rear bearing leads a hard life. Not only is it just inches from the exhaust manifold (which can be 1000F or more), but the generator fan actually pulls hot air from the manifold around the bearing. Also, 1" is too loose, the factory spec is actually 1/2" to 3/4". So my guess is that it was dry, rather than the belt being too tight.

Note that the maintenance schedule calls for adding several drops of oil every 6000 miles; plus disassembly to repack the front bearing every 20,000 to 30,000 miles. If the bearing has been replaced, it may be a shielded design that cannot be repacked, but it's still a good idea to disassemble for cleaning & inspection. If the bushing or bearing are worn, replace them.

To remove the old bushing, use a tap that will just bite into it (sorry, I forget the size offhand), plus a nut to fit the tap and a short length of pipe that will just fit over the bushing. Turn the tap into the bushing until it grabs solidly, then add the spacer & nut and tighten the nut to pull the bushing into the spacer. It slides right out.

 

[dklawson]

Excellent extraction technique Randall. Thanks for that!

 

[TexasKnucklehead]

The idea of the bushing being too dry makes sense, but it seems odd that I had no signs of failure until after I tightened the belt. Within 80 miles, there was tiny specs of the bushing all over the engine bay. If I hadn't noticed, the armature would have dug into the field in the very near future.

This generator was one of the first things I 'finished' during the 6 year restoration. I honestly don't remember if I soaked the bush over night or not. I do know that I added a few drops of oil via a tube on the end of a small oil bottle, shortly after I got back from my Pa trip. That oil hole is not easily accessible, especially with my heat shield in the way. Knowing 3 drops got in there is little more than a prayer. It also makes me wonder about the soaking procedure. For now, I used the rear plate of another generator, complete with bush, just to get the unit back together and running. But I didn't soak it (the bush was already installed). I have no idea how long that generator has been sitting around in how many different spare parts boxes. Nor do I know how long my first generator sat around (soaked or not) before it was actually used.

So, if the bush soaks up oil in 24hrs, how long might it be able to sit around, before it dries back out? I have another used rear plate with bushing (but with springs/brushes etc removed) soaking in oil for another complete replacement generator, and wonder if a few drops every 6 thousand miles is adequate. If I use the generator in there as a back-up, how often should I top up the bush oil?

It also seems that another fan plate could be used that would allow air to be driven from the front to the rear.

 

[HerronScott]

Not sure if it was the right way or wrong way but in the early to mid-80's when my wife and I only had Triumphs as our daily drivers (both with generators), I had issues with generator failures when rebuilt by the local auto electric shops. I finally decided to do the rebuild myself and somewhere I got the information (pre-Internet) to heat the bush in oil and then let it soak 24-hours. I also used a tap to extract the old bush (again don't know who told me about that trick) but in my case the bushing pulled out when the tap bottomed out so no nut or spacer. Adding the nut and spacer sounds like a better method (thanks Randall!).

My ongoing generator failure issue stopped once I rebuilt both of our generators and I know I got at least 70,000 miles on the one in the TR4A.

Scott

 

[ekamm]

I had the same failure on what appeared to be an original bushing, or at least rather old. I too had noticed the belt being loose and the pivot bolt was very loose due to a missing nut. I repaired it and set the belt a bit tighter, but still fairly loose. It wasn't long before the bush failed on the side that would indicated that it was from being pulled sideways. I have to add that I hadn't oiled it and it may well have been worn out and my tightening finished it off. I did soak it and will oiling it regularly.

 

[angelfj1]

Jerry, take a look at this.

https://www.britishcarforum.com/bcf...cas-Dynamo-rebuild-Moss-armature-does-not-fit

You may not want to go through the trouble of machining the back plate, but it worked great for us!

Frank

 

[TR3driver]

The idea of the bushing being too dry makes sense, but it seems odd that I had no signs of failure until after I tightened the belt.

It could easily have been a combination of the two. Lubrication is a lot less important for a lightly loaded bushing; in effect the oil increases the load carrying ability. So a lightly loaded bushing is better able to survive without oil. They do also tend to fail suddenly; there is a positive feedback effect. As the bearing heats up, the friction goes up, which increases the heat and increases the friction.

I don't know how long that bush could be stored after soaking; probably depends on the quality of the oil. Easy solution IMO would be to stand the replacement generator up on it's pulley and fill the cavity with oil, let sit for a few minutes and then install.

Good point about the heat shield, I haven't tried to lube that bearing since installing the shield. But I'm guessing that all I'll need to do is bend my long oil spout a bit, to work around the shield. Sorry I've forgotten where it came from, but I've got an oil can with a 24" spout that works well for such things.

Good luck with redesigning that fan. It's tough to make an effective fan that fights centrifugal force instead of using it, especially one that works over a 10:1 rpm range.

 

[Tinkerman]

So I have my backup bushing in the oil , how long should I leave it in to soak?

Thanks, Tinkerman

 

[Geo Hahn]

I usually soak it 24 hours -- having the oil warmed may help too.

Before any long drive I oil that guy with several squirts from a little oiler I have just for that job:

A friend gave it to me... patent date is April '05 which, since I've had it 10 years, means it dates from 1905. A perfect size for soaking that felt pad in the rear of the dynamo.

 

[TR3driver]

A friend gave it to me... patent date is April '05 which, since I've had it 10 years, means it dates from 1905.

Interesting. I wonder what they found to patent in 1905. Similar cans were in use well before that. Maybe the "pucker" area being on the side instead of on the bottom?

Here's a catalog published in 1895, showing a wide variety of oilers available:
https://books.google.com/books?id=TAfiAAAAMAAJ&pg=PA291

 

[mrv8q]

That oil hole is not easily accessible, especially with my heat shield in the way. Knowing 3 drops got in there is little more than a prayer.

Thought I would resurrect this thread; I've been thinking about that hard working little bearing, as the heat shield makes it hard to access the oil hole. On the 'bay, I picked up a little oiler called a Zoom Spout, five dollars. It has a long flexible tube oiler, which allows just the right length to get to that hole. Took all of 30 seconds...

Hate to think how long I neglected that critical area...

 

[dklawson]

I had to Google "Zoom Spout" after Kevin's post. It sounded familiar. We have one or two of those in our prototype shop (test lab) at work. They are very handy for getting oil to hard to reach spots.

https://www.laco.com/lubricants/zoom-spout-oiler/