Lucas E3NL0 low voltage output

[Davidvb4]

Hello,

First of all, I am new here to this forum. My name is David Bouwmeester and i'm from Zwolle, the Netherlands.
I am the proud owner of a '49 matchless g3l from the Dutch army. I've been working on restoring the bike in its original condition. At the moment I am having problems with the lucas E3NL0 dynamo. The voltage output is about max 0,2 - 0,3V. I've done resistance checks on both the fieldcoil and armature but these seem fine. It is able to motor when applying a 6V battery to it. I've tried flashing the dynamo but it didn't help. I decided to replace the fieldcoil and the armature but still same voltage output. Does anyone know what the problem could be?
Best regards David Bouwmeester

[Andy51]

Have you read http://www.archives.jampot.dk/technical ... nical_tips (I would put a link here but I don't know how! I think I have done it (Clive - moderator)). There's plenty on dynamos there. Andy

[Groily]

Did it motor in the direction it should turn on the machine David? If not, then the rotation is wrong and you need to reverse it. E3Ns should have a voltage control box (and two brushes) - so swapping either the brushes or the field coil connections will reverse the rotation. (It's easy to hook up the field coil in the wrong sense when replacing it.) Flashing it will have confirmed the polarity, but won't affect direction. If the polarity were 'wrong' you'd see negative volts when you want positive, or vice-versa, depending on what earth you have chosen.
Sometimes it helps to give the brushes a light squeeze when it's spinning, if the contact isn't that good (or a squirt of electrical contact cleaner). And the spinning speed matters too - I'd reckon you want to be able to spin it at 1500rpm+ for it to cut in if it's going to and also show you some decent voltage as rpm rise further. A battery-powered drill might not go fast enough, and many small lathes are pushed to go fast enough too.
Also might be worth checking how the field coil is wired. Lucas was 'one lead to earth and the other to the F terminal' but for some modern voltage regulators (JG units and one or two others) the field is connected across F and D as the regulation is done on the live side. The regime for testing them on the bench is different.
Most 'continental' systems (and the likes of Miller) worked on 'live side' regulation, Lucas connected the field to earth.
Good luck!

[Davidvb4]

It motors in the correct direction (anti-clockwise). I tried to reverse the fieldcoil connections to be sure, which caused it to motor in a clockwise direction. The output was the same, except it being negative.
The brushes seem to make good contact; squeezing them doesn't affect the output. When I pull 1 brush during spinning, the voltage output on the meter reads 0 in stead of 0,2-0,3V which is logical. Currently i'm spinning the dynamo with a battery powered drill, which runs approximately 1000Rpm. Although I understand that, at this rpm, the dynamo doesn't produce enough voltage to charge the battery, I would at least expect several volts of output (lets say in the range of 3-8V in stead of the 0,2-0,3V I'm getting now).
This dynamo has a separate mechanical voltage regulator, currently not connected during testing on the bench. The fieldcoil is directly connected to "F" and the other side to earth. The brushes are (1) connected to earth and (2) to "D". I have cleaned and checked the connections.
Since I already swapped the fieldcoil ánd the armature for new ones, and getting the same readings as before, I would expect these to not be the problem. Maybe I'm measuring the wrong way? Or could there be some other short which limits the voltage output?

[clive]

How are you measuring? with the dynamo disconnected from the regulator the normal method is to start by joining the field and drive terminals with a wire. Then run your tester from there to earth on the body. At just a little over normal bike tickover revs you ought to get 10 or so volts. Don't increase the revs too much.

This website has pretty good advice in one place https://matchlessclueless.com/electrica ... as-dynamo/

[Davidvb4]

Hello Clive,

that's the way I've measured the dynamo. I read a lot of info on this site too but still can't seem to pinpoint the problem

[Groily]

I still suspect you need more rpm David, to get it to kick in after its non-use. Or, at least, I certainly wouldn't condemn it as faulty without having spun it a fair bit faster.

Unless there is a short circuit on the D brush wire or terminal with the cover fitted, or some other wiring problem, with the new parts it should work fine if it motors smoothly the right way.

The dynamo won't produce a voltage close to or exceeding the battery's until it's spinning faster than 1000 rpm (remember it's geared up compared to the crankshaft when on the engine) - and to excite it for the first time it may well need a bit more. They often do. Volts/revs isn't a 'linear' thing at speeds below where the dynamo has self-excited - it has to get itself going (the 'avalanche' phase) first, which often needs a kick when the residual magnetism in the body (which is what sets it off) is low after disuse.

So I'd give it a faster blast to see before despairing.

[aobp11]

The output was the same, except it being negative.

This is not what it should be. The output should be 0 V. A suggestion for another check: feed the field coil straight forward from a 6 V battery, say with battery + to F and battery - to Earth. Rotate the dynamo in ccw direction. The voltage at D (w.r.t. Earth) should increase rapidly with rpm, much faster than when the dynamo is self-exiting and almost linear with rpm. The D voltage should go + . When you reverse rotation to cw, the D voltage should go - .
Remember to connect F afterwards for a second in the polarity which is used at the bike (when that polarity is different from the one in the test).
If the test fails then check that about 2 A current is flowing through the field coil.
I saw that you are a member of the Dutch club. You can phone me if you like, my data are in the Special Issue.
Success,
Albert (Otten)

[Davidvb4]

Yesterday I performed the test Albert suggested and measured an increasing voltage up to approximately 4,5V. This gave me a little bit more confidence about the condition of the dynamo. I assembled the dynamo on the bike to be able to test it with higher rpm. First measurements still gave 0,2-0,3V at fast tickover. Then I tried to speed up the engine and suddenly the meter showed 10V. After that the voltage dropped to about 4V at slow tickover! Speeding up the revs a little gave a nice 7+ V It seems that the dynamo suddenly woke up.
Thank you all for your advise

[aobp11]

David, I found some old notes of my measurements with E3N and E3AR. When feeding F from the battery, the D output rises to about 6 V at about 1000 rpm. Self-energizing, D = F, requires higher rpm. The output voltage drop is about 2 V when D has to feed F (at 6-7 V). An E3N gave 4 V at 1200 rpm, 6 V at 1450 rpm, 7 V at 1600 rpm. Apparently somewhat lower output than specified since cut-in at 7 V should occur between 1250 and 1500 rpm.
I think (with Groily) that your drill simply didn't have enough power for the job!
Albert