Two different R27 problems!

[boatdoc]

Hi Kurt,

I did a thorough cleaning such that it looks like Alan's picture. Good idea on the resistance checks, I will do that (fourth time taking out the field coil plate!).

I also found on the 6V VW forum a check for the generator output. You basically disconnect the generator from the regulator and run the generator separately. Theoretically without the regulator it should read about 17V. It turns out that a bad regulator can keep the voltage too low by restricting the current. The VW forum showed a drawing of their Bosch regulator and it looks a lot like the R27's. They do mention that the electronic regulators may solve that problem as they can correct a wider range of voltage/current issues.

Now that the seat is off I will lift the tank off to clean the regulator contacts first and check that wiring for continuity. Sounds like enough to keep my evenings busy this week!

I will also get a chance to replace the aluminum trim around the seat.

Thanks again for your help!

Cheers,
Paul

 

[ragtoplvr]

In general terms, since I do not know R27

The best way to test a generator is to run it as a motor. If a generator will not motor, it will not generate.

To do this you need to apply 6V and ground to the case, and then you have the fields to excite. There are 3 common fields. A circuit, where the field connects to ground, B cir suit where the field connects to 6V and isolated, where you have to connect the fields outside. Polarity is critical.
The generator with the fields connected will motor at a slow speed, if you remove the field connection it will briefly speed up then stop.

The mechanical regulator can be changed with as little as a 1 foot drop. You have to let one run for 15 minutes with the cover on before checking the voltage, as these have bi metal strips and copper wire, all of which change with temp.

Normally to adjust the voltage you bend the spring seat up or down to change the voltage.

These time consuming steps are often omitted in today's hurried world.

Rod

 

[boatdoc]

Hi Rod,

Neat idea! I will try to figure out how to do that!

Cheers,
Paul

 

[169993]

Generator testing

The armature can easily be checked with an ohmmeter. Any given commutater segment should have continuity with the segment that is 180 degrees away. There should be no continuity between any segment and any other part of the armature, nor should there be any continuity between any segment and any other segment that is NOT 180 degrees away from the segment in question. There are only two possibilities with an armature winding as far as failure goes... They will either fail open, or in other words have a broken winding, or they will fail by shorting the winding or segment to the armature body

Weak brush soprings will allow the brushes to bounce on the commutator and allow arcing. This is seen by the black streaks on the copper. An out of true armature will also cause the bouncing as will worn out bushings.

Any good starter/ alternator/ generator shop can rewind an armature, or if needed repair the commutator. It might not be all that cheap to do, but depending on how scarce this generator is the cost could be justified.

One last thing.... On a high mileage generator it is common to have a densely packed build-up of carbon between the segments of the commutator, and there can also be copper dust there also... either will short the segments out and cause failure... When a commutator is turned down during a rebuild, the insulating material between the segments must be undercut to inhibit the ability of copper buildup across the segments as well as preventing arcing bewteen segments during normal operation. Again, this is an easy thing to do for a properly equipped shop. The average Joe can do it by very carefully using a thin hacksaw blade.

 

[boatdoc]

The entire armature/commutator is very clean and there is no grease or build ups. The gap between the commutator parts is clean and the insulation between the stainless parts of the armature is clean. The commutator is shiny copper.

But, every one of the armature stainless plates has continuity to every other part. Also, every segment of the commutator has continuity to every other segment. There is no continuity between any of the commutator plates and any of the armature plates.

 

[44006]

Cooked Armature

"11-19-2010, 08:18 AM
- while riding down the freeway last night the red light came on. Over the next 15 miles home the lights got dimmer and dimmer and were barely lit for the last 5 miles. The bike ran fine otherwise. I've been having to add water to the battery most every time I ride it."

Above sounds like generator was overcharging to the point the armature windings got hot enough internally to melt the lacquer or other coating on the windings and short them together resulting in the following:

"03-06-2011, 06:46 PM
every segment of the commutator has continuity to every other segment"

This was a common occurance with Harley Sprint 1965-1972+- which was guaranteed to cook its generator with sustained interstate 70mph operation.
The generator of the sprint is very like the generator in my R26 BMW and maybe same or very close to same Bosh armature

A fellow I used to ride with who rode BMW R26 in the late 1960's would not sustain speed over 60mph for any length of time - not because of electrics - but because he swore it always would lead to conrod big end failure - he had rebuilt several times.

 

[boatdoc]

Could be overcooking. I thought that would be controlled by the voltage regulator but after replacing it to no effect and after talking with Benchmarks and Motorad Electric it might be an internal armature short. Interestingly, on my last check I was getting 4.9-5 v consistently from the generator. As the voltage is a function of the current and the windings, a short in the windings would cause the lower voltage.

Apparently a good test can be done with a growler, which I don't have. Bob's does however, so I took it over there today. We'll see!

If it is a bad armature the options seem to be:
new armature for $440
new generator for $1063
switch to a 12v system for $575

Any opinions?!

Thanks,
Paul

 

[20774]

I would want to stay 6v but sometimes finances needs to be factored in.

 

[ccolwell]

I think the only reason to keep it a 6v is originality. That might make a difference in resale value, but I doubt much. I'd go with 12v, but then I like triple disk brakes.

 

[44006]

"Could be overcooking. I thought that would be controlled by the voltage regulator but after replacing it to no effect .........."

Quite likely bad regulator system at first produced the overcharge/overload which burnt the armature up before you replaced the regulator. If one of these old relecs was cranking out
enough charge current to boil out the battery repeatedly it almost certainly toasted itself. I
have never been blessed with such an excess of charge current on any vintage machine.

If you have the person with a growler and he knows how to use it that will probably tell the tale.

If the 12 volt system you mention is like the 200 watt alternator that is sold for /2 it is wonderful
simple and easy to install and will run quality h4 light and electric vest. Expensive headlight
reflector conversion though and if stand on the rear brake in traffic too long will melt tail light
lense.

When I was buying these armatures (bosh) for HD Sprints in the late 1960,s they were $35
from a BMW dealer and $60 from a Harley dealer.

 

[boatdoc]

The latest update...!
Took it to Bob's for testing on the growler. Came through that test fine. They then traced the wires and found nothing. On a hunch that the problem may only show up when spinning they borrowed another R27 armature (thank you whoever that was!), put it in my bike and it charged fine!
They have now ordered an armature. Fingers crossed.

 

[boatdoc]

Good news - bad news

The Good - The new armature showed up from Germany after only two months. It went in fine and all seemed great...!

The Bad - 250 miles later,oOn the way back from the Classic British and European Bikes rally in Clarksburg today the charge light came on, went off, came on, went off, ..., stayed on. Got it back home, put the voltmeter on the battery and got 4.6 volts with the engine running at about 1500 rpm and 5.7 volts with the engine off.

So, going back to the beginning, there were two symptoms. The dry battery and the charge light. Is something causing the armature and battery to go bad? I did put in a new voltage regulator early in the attempts to remedy.

 

[20774]

Ho boy...back to the beginning. The Rinckes book doesn't seem to cover something like this. You really must have something basically wrong or something is ruining things when you get new parts. Kind of beyond my DC circuit expertise...my next call would be to Vech.

 

[boatdoc]

Hi,

What I'm hoping is the final post on the problem!

Not wanting to void the new armature's warranty, I took it back to Bob's. They confirmed the problem and put the armature back on the growler, no problems seen.

Dave checked through the various electrical parts and found that the wire to one of the brushes had fatigued and was actually broken, although it looked connected. Due to its stiffness and construction it would connect when at rest, but would move apart when the bike was moving. Since it was new, it was under warranty.

Fingers crossed, the bike runs great again. Hit 70 mph on the way home!

Cheers,
Paul

 

[boatdoc]

Another update; the problem is not yet resolved. The joy of an old bike. So, the new brushes lasted about 15 miles and the red light was back on. The service guys and I brainstormed to no avail.

Off I went to the MOA Rally and visits to the Vintage area and Airhead tents. 30 seconds of listening at the Airhead tent and Bill suggested it was probably armature out of roundness due to crankshaft wobble. Sure enough, I got home, borrowed a dial gauge and found the armature was 15 thousands out of round while the BMW spec was 4. Some guys are just really good! Off the crankshaft the armature was only 3 out of round. It took a few months before I had the time, but I set the bike up with the gage in place and filed the stainless strips until I got the out of roundness to 5. Unfortunately I couldn't get it closer with the set up I had.

I reassembled the bike, rolled it outside, found the battery was at 6.3V and started it up. The red light was still on! I then checked the voltage and found that one brush was not getting a contact. I lightly pushed the brush down and bingo, the red light went out! Woo hoo!

No problems for about thirteen miles. The red light stayed off, the bike ran and I was feeling good. Then the bike shuddered like it was low on electricity. I quickly flipped the lights out, it perked up and I rode home. The voltmeter showed 5.1 V.

I figured I really needed to see what was going on electrically so I bought and installed a WattsUp at the battery. It tells me voltage, current and power. With the engine off and the lights on there is a draw of about 43 watts from the battery. With the engine running at about 1500 rpm with the lights on, the red light is out, the voltage is 7.1 and the draw is about 38 watts. So, it seems the "50 Watt" generator is putting out the voltage but not more than 5-10 watts.

Any thoughts from the collective?! Try again to get it under 4 thousands?

Thanks in advance!

Cheers,
Paul

 

[20774]

Paul -

Sorry, but I'm really at a loss on this. But you went from 15 thou to 5 thou with basically no improvements, right? You still lost power or battery charging in about 15 minutes. So going to 4 thou doesn't seem like it's going to really result in any improvement.

You must live close to Bloomsburg? Do you live in PA? I know Tom Cutter doesn't work on these bikes. Todd Byrum is the Airhead Airmarshall...he might have some ideas. The Airheads site has a file showing Airhead friendly shops around the country. Maybe someone on that list has some experience with pre '70 6-volt electronics.

 

[69zeff65]

How old is your wiring harness

Give your entire wiring harness a once or twice over. Check for kinks, pinches and potential breaks or partial breaks in your charging system wires especially. A simple continuity test with an ohm meter may or may not show problems so a really really good visual and finger manipulation check may reveal the culprit, a couple pinched or broken strands can really make a difference with old wires and components. Make sure you have excellent grounds and connections in the entire system also. I had an R 26 that did the same thing but it was the Harley shop rebuilt(not trued up very well) crank shaft that caused that problem so long ago, so you may have already found the problem but don't know it. You may also consider taking your charging components and putting them an the test bike

 

[44006]

"With the engine off and the lights on there is a draw of about 43 watts from the battery. With the engine running at about 1500 rpm with the lights on, the red light is out, the voltage is 7.1 and the draw is about 38 watts. So, it seems the "50 Watt" generator is putting out the voltage but not more than 5-10 watts."
=====================================
I think your conclusion is wrong - if voltage is up to 7.1 when running at speed the 6v battery is being charged. There is no other way to view this. You are not understanding your measuring gadget.

You need to connect a needle type voltage meter to the battery(not anywhere else in the harness) and get it up to the handlebars or tank bag so you can see what the voltage does when you actually ride.
Make sure the voltmeter is reading voltage and not vibration when you are running.

If your battery is going dead while riding there will be a significant period of time where the volt meter is showing significantly less than 6v or showing wild fluctuations in voltage.

You mention you had to push one of the brushes down to get charge current started(red light go out) - you may need to sand off some of the brush thickness or width so it freely rises and falls within the brush holder to compensate for the out of round condition of the armature.

Another thought - is there any evidence that the outside of the armature is rubbing the field shoes? - this would heat things up and kill the charge current.

Just to be sure we are all understanding each other:

Armature is the entire unit affixed to the end of the crankshaft
Commutator is the segmented ring of contacts upon which the brushes ride

The armature can be out of round relative to the crank quite a bit and still work so long as it does not rub on the field shoes.
Filing down the outside of an armature that does not touch the field shoes will just reduce the magnetic field and therefor the ultimate output.
The commutator needs to be nearly true relative to the brushes so the brushes do not bounce - back in the day of auto generators we used to sometimes spin the generator and turn down the commutator so the brushes would not bounce and then undercut the grooves between the segments - it would not matter whether the shaft was true or bent so long as the commutator end was true

Report back

 

[boatdoc]

Hi,

My bad, I was using the term armature and commutator incorrectly. There may be some armature rubbing on the field coils as one shows a bit of brightness compared to the others. The out-of-round-measurements were for the commutator. If there is rubbing on the field coil, do I file down the stainless piece?

Regarding current versus voltage, the WattsUp reports Volts, Amps, Watts, Peak Amp, Peak Watt, Amp-hr and Watt-hr. The way I have it rigged up is that the meter is taped to the handlebar crossbar and it is in the electrical system right next to the battery. No error on the amount of current flowing to/from the battery.

I do believe that filing the commutator down did make some improvement as the red light now stays off (since I pushed the brush down). I will file the brush to make sure it slides more easily - it did feel a bit sticky.

Thanks again!
Paul

 

[44006]

The armature must not rub on the field coil shoes - I think the way to solve this is not to file on the armature but to loosen the bolts holding the field assembly SLIGHTLY and tap this assembly with a plastic mallet or piece of wood till is does not rub and then re tighten - you can trial and error this with a smear of thin paint or other material and see if it rubs off or not and then know which way to knock the assembly to improve the situation. Whatever you do - do not run this thing rubbing against the field you will destroy the new very expensive armature.

As for your measuring gadget I am not familiar with it but voltage at the battery while running is the only thing you need to look at and sometimes digital meters are not good at detecting fluctuating voltage - some do not read at all and some seem to average things out and not clue you into an irregular fluctuating voltage like an old fashioned needle voltmeter does. I don't know what the WattsUp is but if it is digital it may not be useful for this problem.

The voltmeter you use does not need to be accurate but just indicate that the voltage while running is reasonably more than the voltage of the charged battery at rest.

A cheap needle type voltmeter will usually show if the problem is wild fluctuations in voltage caused by jumping brushes and will also show when the voltage regulator changes the field current by its switching resistance - you can usually see this cutoff and determine if it is reasonable.

I am making a rather wild guess here but I suspect if you are starting out as you have previously said with a charged battery and an initial good charge rate from the generator and then end up down the road with a dead boiled out battery the following is happening:

1) on starting out the system is working properly
2) on running for some time the jumping and sticking brushes are fooling the regulator into always switching for max charge rate and overcharge battery
3) rubbing armature on pole shoes overheats the field and armature and or the brushes stick and charge rate declines from heat or no field current from brushes
4) then you are running on battery alone till it is discharged


Do not loose sight of the logic that must apply here

You cannot "boil/dry out" the battery without applying an excessive charge rate/voltage - there is no other way - so the generator will charge and do the job but is being prevented from doing so in a smooth and regulated way probably by mechanical problems with the brushes or regulator or a buildup of heat sufficient to degrade the electrical efficiency of the unit

file or sand down BOTH brushes till they work easily and smoothly up and down the brush guides