Author Topic: Lucas E3L Dynamo Query  (Read 735 times)

Offline PatM20

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Lucas E3L Dynamo Query
« on: 12.04. 2018 13:02 »
I understand that one wire from the field coil goes directly to F on the regulator and one to the earthed brush.

However, I presume that it doesn't matter which one goes where. Reason for asking is that I have two black wires coming from the field coil and cannot remember which ones goes where.

Just thought of another question, if it doesn't matter which field wire goes where, then does it matter which brush goes where i.e. can the earthed brush be fitted any side of the commutator and vice-versa the output brush that is wired to D.

I need to get this right as I have a positive earth solid state regulator and so will be running positive earthed electrics.

Regards

Pat

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Re: Lucas E3L Dynamo Query
« Reply #1 on: 12.04. 2018 14:07 »
One wire goes to earth the other to the field terminal on end cap. Motor the dynamo and it should turn in the same direction it does on the bike, if it turns in the wrong direction, reverse just the two wires (leave the brush wires as they were). When motoring the dynamo, be sure to use the same battery polarity as on the bike to create the right residual magnetism in the body.
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Offline PatM20

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Re: Lucas E3L Dynamo Query
« Reply #2 on: 13.04. 2018 10:01 »
I have just had a good look at BSA Service Sheets 808 and 808A (808 is for a negative earth wiring diagram and 808A for a positive earth one).

Both dynamos turn anticlockwise at the drive end and clockwise at the commutator end.

My understanding is that both dynamos can be flashed/polarized to positive or negative earth systems without re-positioning the brushes.

The interesting thing for me, which demonstrates huge holes in my understanding of how dynamos work, is the positioning of the earthed brush in that they seem to be positioned differently for positive and negative earthed systems. I have in the past and quite recently changed the polarity of dynamos through flashing and not altered the positioning of the brushes; Lucas Dynamo Re-polarization Instruction Leaflets make no mention of swapping the brushes round. This must mean that it doesn't matter which way round the earthed brush goes (that statement was a big leap of faith by me).

Which leads me back to the field coil wires. My understanding (which could be wrong) is that this winding is one long wire that is wound round lots of times and its beginning and end stick out. One end I know needs to be connected to F on the regulator and the other end to the earthed brush/earthed. I just cannot get my mind round why it matters which wire goes to F and which wire is earthed. Throw in changing the polarity into the mix and I get even more lost.

Help!




Online groily

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Re: Lucas E3L Dynamo Query
« Reply #3 on: 13.04. 2018 18:15 »
There are some things you just have to take as articles of faith!

Polarity - not a problem, and easily swapped by 'flashing' as you say. All that does is 'sensitize' the thing to work according your choice of earth. No changes to the dynamo to swap it, just a question of 'educating' it that one side or t'other is the earth side.

 If it turns the 'wrong' way for the bike (50/50 chance if starting from 'no idea')  . . . it's the field coil and brush connections that control this. The arrow on the body may or may not agree, but it doesn't matter - you can have either rotation, on any dynamo.
You can reverse it either by swapping the field coil ends over, as stated previously - OR you can swap the connections of the wires coming off the brushes. Same effect. But don't swap both lots or you end up where you started because you've swapped it twice, once by each method.

Boring extra things to worry about in some circs:
1.  Some dynamos - not E3Ls - have one brush holder that is insulated and one that is earthed by design  - and you have to respect that.
2. Some regulators don't work like Lucas regulators, and you have to respect this too, with any dynamo including an E3L. The field is not wired the same  . . .

 . . . if you just happened to be using a modern JG voltage regulator (there are lots of them about), or maybe some foreign device, then you'd need to alter the wiring at the dynamo (their instructions should explain it clearly). Lucas did it it their way, but most others, including Miller, and all continental European and most American makers, did things differently, with the field coil connected between F (same as Lucas) and D (not to earth, so different - and so are the basic testing routines).

99% of E3Ls have one field wire to F, t'other to earth along with one brush tail, and the other brush goes to D. Which goes to where depends on rotation required and on what's easiest in terms of length of wires and of safe routing inside the end cover (to avoid any shorts from F or from D to the body, the cover, or each other).
Bill

Offline PatM20

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Re: Lucas E3L Dynamo Query
« Reply #4 on: 15.04. 2018 10:07 »
Hi Groily,

I am still trying to get my head round this.

My understanding is that "flashing" a dynamo can be used in two situations. First, it can be used to restore residual magnetism for a dynamo that has not been used for some time and second, to polarize the dynamo to suit a positive or negative wiring system.

If polarizing the dynamo is used to convert the polarity of the field coil from positive to negative or vice-versa is this not the same as swapping the field coil wires around?

So, if the field coil wires were the correct way round say, for positive earth and you flashed it for positive earth, then everything would stay the same and not change. If the field coil wires were the wrong way round, then flashing the dynamo for positive earth would would convert the polarity back to the one you required.

Am I being thick?

Regards

Pat

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Re: Lucas E3L Dynamo Query
« Reply #5 on: 15.04. 2018 10:42 »
Hi Groily,

I am still trying to get my head round this.

My understanding is that "flashing" a dynamo can be used in two situations. First, it can be used to restore residual magnetism for a dynamo that has not been used for some time and second, to polarize the dynamo to suit a positive or negative wiring system.

If polarizing the dynamo is used to convert the polarity of the field coil from positive to negative or vice-versa is this not the same as swapping the field coil wires around?

So, if the field coil wires were the correct way round say, for positive earth and you flashed it for positive earth, then everything would stay the same and not change. If the field coil wires were the wrong way round, then flashing the dynamo for positive earth would would convert the polarity back to the one you required.

Am I being thick?

Regards

Pat

The way I look at this....is that the armature powers the field coil at start up (not the battery). The polarity of the residual magnetism in the field coil will therefore determine the start up polarity of the dynamo (e.g armature connector).

If the dynamo starts up the “wrong” way then there cannot be any charging of the battery. “Wrong” here, means the opposite polarity to the way the battery is installed.

So, to do the polarity swap, swap the polarity of the battery, and flash the dynamo to suit the new polarity, and it should all work. If an electronic reg is installed then that will need to be “reversed” e.g. re-wired (or replaced, if not reversible type) as well as the battery.

 The mechanical reg works negative or positive without re-wiring (tho I’ve never tried this myself).

Hope I’ve got this right!







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Re: Lucas E3L Dynamo Query
« Reply #6 on: 15.04. 2018 11:24 »

  Hey PatoM- I'm a bit like you and know enough about this to be more dangerous that the average UXB, but I did reverse my polarity because I tired of blowing stuff up, like batteries and stuff....seemed to work ok so far but don't recall exactly what I did but straightforward..I've attached a item I found on the netsss a while ago, which may help, but also have a Lucas regulator doc that I downloaded but is too big to post here (1.9Mb), but if you do a search for "Lucas05 Generator Output Control (27 Pages)", it may come up...I found it helpful in understanding the darkness... (kinda like the mechanical regs in a fu**ed up kinda way)
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Offline PatM20

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Re: Lucas E3L Dynamo Query
« Reply #7 on: 15.04. 2018 11:43 »
Hi Dutch

Yes, I read this. My problem is that the two wires from the field coil are both black, the same length and no way of knowing which one goes to F and which one goes to D.

Regards

Pat

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Re: Lucas E3L Dynamo Query
« Reply #8 on: 15.04. 2018 11:58 »
Neither field wire is connected to D. One to earth the other to F. Doesn't matter which might just mean it would turn wrong way. If wrong , change them around.
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Offline PatM20

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Re: Lucas E3L Dynamo Query
« Reply #9 on: 15.04. 2018 12:09 »
Hi BSAReg

Sorry, meant earth.

Regards

Pat

Online groily

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Re: Lucas E3L Dynamo Query
« Reply #10 on: 15.04. 2018 18:14 »
'Articles of faith' again Pat!

The easiest way to see how it all operates is if you have the dynamo on a bench, a battery handy, and a meter and / or bulb and some play time. A dynamo works like a motor in reverse, and can be made to behave like a motor.  An inefficient motor, because the design isn't for it to BE a motor, but the principles are much the same. (Is there a fridges and aircon parallel . . . dunno!). Anyway -

Dyning:
If it is a working dynamo, then you can bridge your F and D leads, stuff a meter and/or bulb (12v, say 21W brake light bulb, is easiest because the filament will light up more easily due to its being thinner to heat up than on a 6v, which needs more current/amps) between the bridged wires and the body (earth), and spin the dynamo fast in the direction you reckon it should go. Battery-powered drills are no good at all, you'll need way over 1000 rpm often to get the thing to excite and kick in, especially 'first-time'.

If it deigns to start up, you'll see volts, rapidly rising, on the meter. Starts with far less than a volt, using the 'residual magnetism' so-called, which is the magnetic trace left in the iron pole the field coil wraps round on the inside since it last operated; then it builds up with speed once it's got going (what's called the 'avalanche' stage). The volts you'll see will be either positive or negative on the meter. With revs, an E3L will shoot up to maybe 20v or so depending on how fast you go, but it's not a great plan to leave them running like that for any length of time.
The reason the magic happens is because the residual magnetism is sufficient to get the armature, turning in this very weak magnetic field, to produce a really small output - this output is fed directly back into the field coil from D, and when that happens, the output shoots up because there is now a proper strong electro-magnet instead of a few miserable traces of residual magnetism. Under the influence of this new magnetic mojo the armature creates a feeding frenzy by supplying the field coil with as much as there is by way of output because F and D are connected.

On the Other Hand  . . . If it doesn't do anything - and it might well not! - try turning  it the other way . . .  it might go. If it did, you could see, again, whether the volts are + or -.

If you want to see how rotation is affected by the wiring of the field coil or by the brushes, you can play, swapping them around. Whereupon you will find that it works one direction with the field wires connected one way, and the other way if you swap 'em. Or swap the brushes - comes to the same thing. Swap both, and you're back to where you started. 

Motoring:
If you want to see from another perspective how the thing is affected by swapping wires and brushes, then you can play with the battery, and use it to drive the dynamo as a motor. Bridging F and D again, and putting battery live (your choice)  to the bridge and the battery earth to the body, it'll run in one direction or the other.
If you want to change just the polarity, swap the battery connections to the bridge and to earth, and it will be repolarised to run the other earth - but it will definitely go in the same direction. You have just, effectively, 'flashed the field'. But if you want to change the direction, swap the field wires (or the brushes) and seemingly miraculously it will run the other way. Lots of (very basic) reversible electric motors do their reversing exactly like this - by switching the field coil wires over.

The thing can run either way, with either polarity. Rotation requires intervention to reverse it, but polarity can be swapped just by telling the field which polarity you want it to have. Which is why you can swap from pos to neg earth in a heartbeat by flashing the field, as long as you have a regulator that works with the chosen earth (diodes and all that modern malarkey). But you have to do some fettling if you want things to go the other way.

The point I made before about some regulators needing different connections is quite a serious one though - I get a lot of bikes in for checks that 'don't charge' - but they do when the field is connected for a regulator designed to work what I call the 'Miller Way' - ie between F and D, with a brush to D and a brush to earth. Lucas were pretty much alone in connecting the field from the F terminal to E in fact, and it confuses anyone used to dealing with Bosch and other equipment, which follows well-established standards. And the number of people outside the UK and the Empire (ha!) who run Positive Earth is pretty small too. It's rare in France where I am to be asked to set a system up Positive Earth for anyone, although my own bikes are because it's what I grew up with.
Bill

Offline PatM20

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Re: Lucas E3L Dynamo Query
« Reply #11 on: 16.04. 2018 06:51 »
Thanks Groily.

I think I get. Assuming there is sufficient residual magnetism in the field coil, polarizing it (one way or the other) is like swapping a horseshoe magnet around in a simple electric motor. Swapping the field coil wires produces the same effect.

Swapping the brushes around is like swapping a battery around, again in a simple electric motor.

The latter will change the direction of the spin of the motor.

Very, very last question (promise), will swapping the polarity of the field coil (either through flashing or by swapping the field coil wires around) have any effect of the direction of rotation when worked as a motor?

Regards

Pat

Offline PatM20

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Re: Lucas E3L Dynamo Query
« Reply #12 on: 16.04. 2018 07:45 »
Sorry Groily for my last post. You have already answered my question.

Regards

Pat