Bleedin'n - piece of sh*t, dynamo

[angelfj]

This is not supposed to happen!

 

Go here for background:http://www.tr-register.co.uk/forums/index.php?/topic/40709-complete-charging-system-failure/?hl=%20generator%20%20dynamo%20%20failure

 

Very busy weekend had us at two shows. I said I would drive this car and I'm trying my best to do so.

 

Up until this weekend, the new (rebuilt) dynamo had been in service for less than 100 miles. So, driving back from Maryland yesterday with approximately 100 miles to go, the ignition lamp went red. Having been through this before, I immediately reduced the electrical load to only the essentials which meant off with the headlights. I always drive night and day with the headlights on and these had to be turned off. The resulting electrical load , ignition, overdrive solenoid, fuel gauge was perhaps 5 amps total load on the battery - more than enough to provide high voltage for sparking plugs for the drive home.

 

Got home , showered and went to bed. I was tired of that red light staring at me. I was also very pissed off. The timing is real bad since the Triumph Register of America convention is next week in Kentucky, an 1800 mile round trip. I must have a reliable car.

 

Like I said, I've been through this before. This morning I did some quick tests, but its obvious from the screeching sound that the dynamo is making that a failure similar to the first one has occurred. Oh, and we did check and lubricate the replacement dynamo. So, the only thing that I am aware of is a too tight belt, and I have to tell you the belt tension is per the book.

 

You may be thinking this, but no, thank you very much, I am not interested in an alternator. I know several sidescreen TR owners who together must have a few hundred thousand miles on their original dynamos. I didn't get 400 miles on this one!

 

Am I missing something?

 

Disgruntled, Frank

 

[AlanT]

Is this a mechanical failure like is broken and wont turn or electical like you just get no output?

 

I have the original Lucas service manual and will email if you PM me with your address.

[foster461]

Frank, what kind of fan belt are you using ?. I was just researching fan belt options for my project and I saw a reference that the more modern ribbed belts put less strain on the bearings than the original flat belts as well as being easier to install and remove.

 

Your earlier generator failure was due to a a failed bearing, did the replacement fail in the same way ?

 

Stan

[EdwinTiben]

Hi,

 

Are the pully's aligned correctly? To avoid any pressure on the bearings.

[Bob Smith]

Frank, I have the original wide belt with dynamo and always have the belt quite slack - looser than the workshop manual suggests. No problems with the belt staying on the pulleys & I still get a healthy charge and my dynamo lasts & lasts!

[angelfj]

Thank you for all of these good suggestions. I'll report on exactly what we find soon, but to answer a few questions that I am able:

 

There is no current being produced by the dynamo, thus the red light.

 

I am using the cogged version of the wide belt.

 

From what I can gather from the workshop manual, our belt tension seems normal.

 

Pulley alignment seems to be very good.

 

The front ball bearing and rear bush are original.

 

I did find something interesting on a British website. This guy rebuilt a Lucas C40 dynamo and substituted a ball bearing for the normal rear bronze bush. We may try this. Read about it here: http://landcrabs.proboards.com/index.cgi?board=tech&action=display&thread=22

[AlanT]

Clearly this has an electrical fault. Something wrong with the brushes or the connection to the field coil.

 

Or the regulator isn't feeding the field winding. Find an auto electrician before messing with ball-bearings.

[john martin]

Hello Frank,

 

Some time ago I simultaneously fitted a re-built dynamo and a new toothed belt to my TR4. Within short order a very loud squeeking, similar to the belt slipping but continuous, was noticed. The belt was kept looser than the book recommeneds and the three pulleys seemed to line up very well. I always had a healthy charge from the dynamo.

 

Trying to eliminate this squeek, i reverted to a non toothed fat belt; problem solved but I have no explanation, sorry! ( Belt tension was kept the same)

 

Regards

 

John

 

PS I have seen this mentioned before on the Forum.

[Graham Harris]

Frank, i think you will find the belt is too tight, that rear bush is the only brass bush in the fan belt sercuit. I would try a looser fit just enough so the pully will grip the belt and not slip when charging.

[TR24178]

Why would the dynamo fail to produce power just because of a dry or failing bearing? Unless it was almost seized! Does it turn by hand OK? does it still make a noise with the engine running and the wires disconnected?

 

Its quite a coincidence that both dynamos failed like this, I suspect a wiring or control box fault.

[TR 2100]

Very easy to overtighten the fanbelt

but -

while that may lead to a failed bearing (with the

inevitable screeching) I can't see it leading to the

loss of charge.

 

I think you have just been unlucky, Frank, and got

a duff unit.

 

AlanR

[vivdownunder]

Frank, for peace of mind on the long journey to TRA, why not spend $99.94 at TRF for a brand new generator and pop it on until you sort out the faulty one. It might have spade terminals though.

 

My spare generator is a 20 amp Ferguson Tractor version - Seems good quality for just $86.00 at the time with a rubber dust cap over the rear bush, but it came with spade terminals.

 

Are you sure it was polarized before fitting ?. TRF site says they can be hard to polarize after a few rebuilds.

 

Squeals are often the front bearing, but you usually get plenty of warning before they give up the ghost completely. Rear bush failure could be to do with the porosity of the material - not holding lubrication. The rear bush may have come loose in the housing. Sometimes the solder in the armature lets go or a wire breaks loose. I've seen a brush wire come away and sometimes a brush retainer spring breaks. The field coils on the casing are fairly reliable. A cracked fanbelt will give sometimes give metallic sounds.

 

I guess all will become clear when you strip it down.

 

Regards,

 

Viv.

[stuart]

I hate to say this Frank but I would revert to a standard control box/Dynamo setup. I have driven thousands of miles with them and never had any problems on the scale of yours.

Stuart.

[Ashley James]

I hate to say this Frank but I would revert to a standard control box/Dynamo setup. I have driven thousands of miles with them and never had any problems on the scale of yours.

Stuart.

Agreed, and for fifty years this year.

[angelfj]

The dynamo has been completely rebuilt.

 

We replaced the armature, field coils, front and rear bearings, basically a new dynamo. We did all of this work to retain the correct and original case with proper date code.

 

some notes:

 

The armature available from Moss USA is metric. It has a key way narrower than the pulley and fan. This required a special key which had to be milled. In addition, the nut which secures the fan and pulley is metric, so the original nut will not fit. It would have been helpful for Moss to indicate the differences between this replacement armature and the original Lucas unit.

 

The front open cage ball bearing was replaced with a sealed, lifetime lubricated unit, model 6201, German made (INA). http://www.mcmaster.com/#6201-ball-bearings/=n4pzny

 

The rear oilite bronze bushing was replaced with a needle bearing. (model number later). The needle bearing has a lubrication grove. We were careful to retain the original felt which we will keep oiled and it should feed lubrication to the new bearing.

 

The new dynamo spins very freely with no noticeable radial or lateral deviation.

 

I am currently using an original Lucas, electromechanical control box. I believe there is an intermittent fault in the solid state unit I had been using, perhaps one of the electronic components is breaking down.

 

For long trips I intend to travel with a spare dynamo and control box.

 

Additional detail later as I gain experience.

 

Cheers,

 

Frank

 

 

 

 

[angelfj]

Photos showing how we did this.

The old bronze bushing had to be removed to install the new needle bearing. This required a special fixture to hold the rear dynamo plate in the lathe chuck.

 

 

Rear dynamo plate in fixture /lathe using boring bar to remove old bushing.

 

Needle bearing reading for pressing into rear plate.

 

New needle bearing in place.

[tthomson]

Hi Frank,

Sorry to hear of the dynamo failure.

 

If my memory serves me properly, the rear bearing takes a much larger axial load than the front, because the front bearing is acting as a pivot. the moment of the force exerted by the fan belt tension is larger at the rear bearing because the distance from the front bearing to the rear bearing is larger than between the pulley and the front bearing. The front bearing tends to be a larger bearing so is less prone to failure, but a sintered bronze bearing in the rear is likely to last longer than a needle bearing, because the stresses are less concentrated.

 

This does not resolve the problem with output though.

 

There are only a few of ways that the output can be compromised.

 

1. Field coil failure

2. Armature coil failure

3. Brush failure

4. Wiring failure

5. Control box failure

 

Testing on a bench will eliminate wiring faults (Use a power drill to spin it)

 

Spinning it around 2000 rev/min without the field coil energised should give about 3 Volts out.

Energising the field coil with 12 Volts should give more than 14 Volts out at 2000 rev/min

 

If the first is not there - Armature/ brushes are suspect

If the second not there - Field coil suspect

 

If both are present, wiring or control box is faulty.

 

Control boxes are far more robust than people think. They are more likely to be configured incorrectly than failed.

 

Good luck

 

TT

[AlanT]

Send a PM with an email address to me and I will send you a Lucas Maintenance Manual for the control-box and dyno.

[Ashley James]

I paid £27 + Vat for and exchange dynamo at my local factors and it's working well, but it's a worry to read of all these problems.

[Graham Harris]

I would have thought the reason for failure to charge given the wear in the rear bush would be the armature polling. This would add to the squeeling noise as well

Graham

[angelfj]

I would have thought the reason for failure to charge given the wear in the rear bush would be the armature polling. This would add to the squeeling noise as well

Graham

Graham: I'm not familiar with the term, "armature polling". Can you explain? Thanks!

[angelfj]

I do admit that the needle bearing decision was debated. One problem is that we had no idea of the armature shaft hardness at the bearing journals. Needles can be very rough on softer metals. Generally speaking, the proper approach would be to calculate the bearing PV and then match up the PV with suitable bearings.

[Graham Harris]

Hi Frank, it was a term we used more in relation to an electric motor, if the bearings are shot the clearence for the armature to the field coil magnet is reduced to the point where they can come in contact with each other or are drawn together by magnetism which creats a buzing vibration that we called polling.I don't know if there is any correctness in this asumption but i do know that if it was a motor it would not rotate ,it would just lock up. I have no background in electrics i'm just a fidler and Mr fixit, i work on the theory that if a man made it i should be able to take it apart fix it and put it back together, i've got away with it so far, mind you there are a few things i hav't tackled yet.

Graham

[angelfj]

Thanks Graham! I try to learn something every day!

[AlanT]

I am really impressed by the care and attention to detail you have put into this.