The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: ybocalandro on 07.03. 2011 14:24
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Please, I need some help with my Lucas E3L Dynamo. I rewound it to 12volt and it wasn't work.
I followed every step as trev said in a forum and and the output voltage was very low
I really appreciate any answer or contact to trevinoz
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Hello,
Welcome to the forum. I'm not the one to give you advice on your dynamo rewind, but I'm quite certain Trev, Groily and a few others will soon be online with the help you need. I believe you are our first Cuban member. To me, this is great, and a testimony to our fearless leader's (Erling's) original idea. I'm wondering, have BSAs been kept in working order in some large numbers there in Cuba, much like old Chevys and Fords?
Regards,
Richard L.
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Don't know about BSAs on Cuba, but I know there are some nice Matchlesses there, as there was a great article a year or so back in the owners' club mag, the Jampot. A real tribute to the owners that they ran at all, let alone looking pretty decent. Made me realise how lucky we are in some other countries as far as parts are concerned!
On the dynamo conversion, best let trev comment as I can't off-hand recall what his preferred route was, from the options available, and don't want to cause confusion. Very happy to add 2 cents' worth as the thread goes along though as I'm sure will many others.
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thanks for your answers, and you are right, is really really difficult to keep my BSA cause we haven't spare parts and the way to get its, so we have to improvise every day, in my case my A10 isn't an antique, it is my means of transportation, that's the reason of my hurry to put my dynamo back to work
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Hi ybocalandro, [that's a mouth full]
If you have wound a new field coil and it is OK for continuity and is not earthed internally to the pole shoe, that part should be right.
When you rewound the armature, did you connect the coil ends to the correct commutator segments?
Did you motor test the generator after you reassembled it?
If so, did it rotate in the correct direction?
Did you test the armature for short circuit to earth? This can happen due to shorted commutator segments or windings.
It's a good idea to drive the generator with the "D" & "F" terminals joined, connect a voltmeter between the terminals and earth and see what you get.
Trev.
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Hi Trev bocalandro is my surname, Is read your post about your E3L specifications and i rewound the armature with 20 turns per coil of 0.7 wire and 450 turns of two wires of 0.3mm in parallel cause i haven't 0.6, the resistance was the same aprox 5.6ohms
I did a bank test with a drill about 2000rpm and i got 8volt and 25A with a 12v 7A battery
I reassembled it and it rotated in the correct direction and I'm sure is not earthed because there is not continuity between the commutator and the armature.
Trev i was trying to ask someone how many segment have the commutator, mine is 24, it is right?
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What is your first name? Much easier that way.
Commutator has 12 segments but each segment is actually 2 pieces in parallel.
If you haven't connected the armature windings to the correct segments, say one away, you will get a low voltage output.
Are you sure that you got 25Amps output? That seems extremely high!
You should be able to exceed 20V when testing as I described.
Trev.
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Please send me a email to [email protected] to send you picts of my dynamo
and then you will give me your considerations
thanks a lot
That's my home email I'm working right now
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Hi I am a new member to this forum and very interested in the dynamo rewind to 12v possibilities. I have rewound an old cooked armature with more turns and thinner wire as one of the older posts but I think I have connected the windings to the commutator incorrectly as I get next to nothing out. I tried to see where they were before I stripped it but it was too burnt to get an accurate assesment. Can anyone explain the connection of the leads from the winding to the commutator that is easy to understand - please *sad2*
Many thanks in advance for any help Peter
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Brave man HondaPete or do you have skills and knowledge in the generator field (pun intended)
As your new to the forum maybe you don't know about flashing the dynamo search for "Flashing" or "dynamo polarity" and you should get some info
meanwhile this from forum member Sparx
The field coil pole piece retains a small magnetic field when the dynamo is at rest just like those nails did when you made electromagnets as a kid. It's called the "residual flux". Depending on if the earth polarity is positive or negative it's either north/south or south/north.
The dynamo uses this residual magnetic flux to build up the field current when starting from rest. If the flux polarity is wrong the voltage on the "D" lead will be the wrong polarity. The cut-out contacts in the control box will still switch in, but will probably be destroyed by what is more or less a short circuit current flow.
To prevent that from happening you quite simply disconnect the "F" terminal on the dynamo and feed the field coil(s) directly from the battery for a second or so before starting the machine after changing or reconditioning the dynamo.
You don't get quite the same problem with a solid state regulator, the diode that isolates the dynamo from the battery when the dynamo output is below battery voltage won't allow the short circuit current to flow, but because the switching circuits are connected to the dynamo output they see a reverse polarity and can get fried.
I'd best stop there. My eyes are starting to glaze over.....
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Thanks for the info, I had re-magnetised the field yoke but to no avail. I know a fair bit about windings but little about dynamo armatures and I think I have screwed up the connections to the commutator.
Still its all a learning expierience, nothing vetured nothing gained.
Peter
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Pete,
If you know a bit about winding, try the following.
The pitch is 1-6.
The start of a coil is connected to the comm segment directly forward of slot 6 and the finish is connected to the next one to the right, coil being wound clockwise.
The start of the next coil is connected to the finish of the previous one, therefore the coil 2-7 starts from the segment in front of slot 7 where the finish of coil 1-6 will be connected.
Work your way around the armature and the final coil's finish will connect with the start of the first coil.
An easy way to wind is to do it it one go without cutting the wire between coils and leaving a loop at the end of each coil long enough to reach the comm.
That way all you have to do is connect each loop to the segment one to the right of the finish end slot.
This will not work if you wind, like I do, a "balanced winding" but will work for the original method.
Clear as mud?
Good luck.
Trev.
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Many Thanks Trev I will have a look at what I did and see where I went wrong *smile*
Peter
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Hi Trev I have removed the windings as they were wrong and sketched out what I think you mean in the attached pic.
Also what is the "balanced winding" method ?
Peter
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Peter,
Your diagram looks good to me.
To wind "balanced", you wind the first coil 1-6, second 6-11, third 11-4 etc.
This gives a better weight distribution of copper around the armature compared to the original "progressive' winding.
However, you can't wind this way without cutting the conductor at the end of each coil.
To avoid confusion between "starts" and "finishes", I tie a knot in the end of each "finish".
Back to work, Peter!
Trev.
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Many thanks Trev, I know what I will be doing this coming week
Peter
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It won't take a week, Peter.
You should be able to wind it in less than an hour and the soldering maybe 1-2 hours, string band - 5 minutes, test - 5 minutes.
Dip in varnish and cook for an hour or so, let it cool and test again and back into the generator!
I can take a stripped and cleaned armature with slot insulation pre-cut and have it ready to go in about 4 hours if I am in a hurry.
But I am an Aussie so enough said.
Trev.
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Trev,
Been following this thread and you've truly given the master class in dynamo coil winding. I was wondering about a few things:
1. You say to dip the armature in varnish and cook it. I know that, sometimes, when varnishing coils is called for, it occurs in a vacuum to be sure the varnish permeates. I believe this is to secure the all the internal windings. I bet most guys here could come up with a jury-rigged tank they could attach their vacuum cleaner to. Do you thin this is needed?
2. Is it a case of "varnish is varnish," or is there some special type that should be used?
3. What temperature should be used for cooking the armature?
4. What vacation spot should the wife be sent to so that the armature can be cooked in the house?
Richard L.
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Richard,
1.I don't believe that dynamo armatures need to be vacuum impregnated with varnish, in fact, I had never heard of such a thing in my apprentice days.
The bloke that I know who is rewinding magnetos does, however, vacuum varnish his armatures. Probably a good idea as magy windings are much more tightly packed than dynamo ones.
I dip the armature in the varnish until the air bubbles stop and then do the cooking.
2. The varnish is a special insulating product. I am using the last known tin of Hymeg that I know of.
I also have Isopron [clear] which the manufacturers say is an air drying type and should not be baked but I bake it anyhow with no problems.
3. The temperature required is 135F.
4. There is no place on earth to which you could send your wife while you cook an armature in the house! Divorce is the best option. This also applies to crankcases, bearings etc but the varnish is worse.
I have an old stove in the shed which is used for all of these tasks but every time the oven is heated all that can be smelt is varnish.
My wife won't enter the shed while ever the oven is heating. Maybe this is a good thing but I make sure that the oven is cold come beer o'clock!
Trev.
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Peter,
A few pictures of armatures.
1. Progressive wound on the left with balance wound, right.
2. Balance wound.
3. Balance wound.
4. Progressive wound.
5. Balance wound.
Trev.
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Hi Trev
It seems this thread has created some interest, I have wound the armature at work in between jobs and am ready to solder and test.
You are obviously expert at this and the pics are great, if you were nearer I would have dropped it on your doorstep *smile*
Many thanks for the help and advice
By the way I have done a couple of mags and that is a nightmare.
Peter
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Good on ya, Peter.
Did you make a new field coil while you were at it?
How do you test? I "drop" test and megger to ensure that I haven't got the dreaded earth on a coil.
The badly burnt armatures usually have the end insulation beyond saving so I use longer slot insulation with slivers of thicker paper between slots.
This is not always successful as I have been known to have failures.
You are a brave man rewinding magneto armatures!
It is not too difficult if you have the right equipment, which I haven't.
Let us know how it all went.
Trev.
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Hi Trev
I reassembled the dynamo last night and it motors fine now, I ran it up in my lathe, which is too slow really, and it has output. I have not rewound the field coil yet so that is the next thing to do and then test properly. I bound the windings and varnished it today now I know that it works.
Yes I meggar the windings I also have a "Growler" I expect you know what that is, for testing for shorted turns. Dad had it in his shed for about 50 years so its mine now.
Again thanks for the help.
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G'day Peter,
Thing's are looking up!
You will get better output results if you make an adapter for a socket and drive the generator with a drill.
I have a pistol drill which supposedly runs at 2500 rpm variable.
I load test generators after completion by connecting a regulator and battery with a headlight.
This saves fitting to a bike and having to remove it again if it doesn't come up to scratch.
I haven't used a growler since my tech college days, in fact where I served my time didn't have one so I didn't get much experience with them.
Trev.
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Trev
I made a former and rewound the field coil today, taped it with cloth tape and formed it to shape around the pole piece and it actually fits into the yoke, so nearly there.
Peter
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Hi all,
Dynamo all finished and works a treat many thanks for all the help.
Regards Peter *smile*
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That's good news, Peter.
Hopefully Yuniel will get his going as well.
Trev.
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Hi all, just to say I'm amazed at the depth of knowledge shown by you guy's no currying of future favours but I've only been on this forum for a couple of weeks and i'm seeing you doing things I wouldn't contemplate . Winding a dynamo ....a black art!! done in a shed? mind boggling when I wanted mine changed to 12v I asked sean hawker Hawker electricals as was , to do it as i'm obviously a wimp! they did a great job bit I've got another one that is duff and i think I'm goner have a look instead of selling it to that DUNN guy for peanuts. hope you don't mind some really daft questions as I can feel 'em coming already ,best wishes Bob.
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Ah yes Bob there are some really skilled members on this forum, however a lot of us learn from them but still need to farm stuff out at times, the secret is not overstepping your abilities (too often that is)
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That is all very interesting to me as I am attempting to rewind a E3N (6volt). I reckon that each loop has 18 turns and am wondering how to fit the 36 wires I think are required into the slot!
Can someone confirm that it is indeed 18 turns per loop? Looks like "mission impossible" to my untrained eyes.
Cheers
Roger
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Roger,
I can't speak to the issue of turns on the dynamo armature, but I can offer you a quiet welcome to the forum.
ROGER,
WELCOME TO THE ONE AND ONLY BSA A7/A10 FORUM!!!
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Roger,
There are indeed 18 turns per coil in an E3N armature.
As long as you are not using too large a conductor, they fit easily.
I quite often wind them with20 turns per coil with no issues.
Trev.
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Thanks you two gentlemen for the welcome and reply..........Trev thanks for that, I will persevere with the rewind then, it's just that there seems hardly enough room for 36 wires in that small channel! I guess I will have think hard about how to lay them. The old wire appears to be about 0.75 mm.
Regards
Roger
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Roger,
Without going to the shed to confirm, 0.7mm is the conductor size.
As you wind, keep it tight and push the conductors into the slots with a piece of insulating board or a piece of Laminex, which is what I use.
Trev.
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Thanks Trev............I can only get 0.8mm here or 0.65 mm for some reason, so have gone for the 0.8mm. Have done 6 windings tonight as am awaiting more wire! It's a tight fit. I wonder if 0.65mm would be too small to carry the current safely? It would be a better fit....
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Steve,
Use a piece of insulation or whatever which is a snug fit in the slot between the insulation and tap down with a small hammer, I use an 8oz ball pein.
The windings should compact OK.
I just went to the shed and had a look in the scrap bag for original windings and found that the old cotton covered conductors are 0.024" and the enamelled are 0.028".
The 0.65mm should be alright.
Trev.
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Trev
Thanks very much for that. I am using the 0.8mm presently and have done six coils and am now awaiting another batch of wire from local supplier as they only had one unit in stock. I modified a plastic paint stirrer and that is doing a good job geting the windings in place. Though it is pretty tight in there, but tests out okay with the meter.
I guess I am not very confident as I have put an AD in the local club mag for a E3N !
Cheers
Roger
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Well I have done the re-wind but...................... I am geting only 150 mv out of the B....y thing when driven with my electric drill (at about 800 rpm I think). It motors well with 12Volts on it and in the correct direction too. But will not drive a 6volt 21watt lamp, which is no surprise with 150mv out.
The Field coil reads 3 ohms, armature is infinite to earth and all adjacent com segments are connected and the highest reading between furthest segments is about 0.6 ohm. I would appreciate any informed comments please!
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Roger,
800 rpm is a bit slow to test, I use a drill which runs around 2500 rpm.
But, the question is, have you connected the coils to the correct segments?
Connecting just one out will cause very low output. [Don't ask how I know.]
Testing resistance between segments is not much use.
I find that "drop testing" between segments is best as I don't own a growler.
Another problem can be a reversed coil, i.e. one that is connected wrong way round. This will be picked up with a drop test but not with a resistance test.
Trev.
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Trev thanks for your reply. I think I under estimated the revs on my drill. I have got it going now there was an intermittant earth fault on one coil. So I had to rewind four coils to clear it! It will light the 21 Watt bulb now and gives 7.8 volts on load.Wonderful!