Yet more E3N dynamo questions

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Re: Yet more E3N dynamo questions

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Group Leader wrote: 1) To power the field coil from the battery, load on the dynamo output, isolated from the field, and run the engine and see whether that will kick it into life
Well that worked :) so the obvious step to follow was to remove the battery from the field, short the field to the dynamo output in the normal manner and see if it would now spring back into life having had a couple of minutes running and hopefully re-magnetising the pole piece.

Sadly no such luck and the bulb remained stubbonly unilluminated. It would appear therefore that either the residual magnetism isn't up to it, for whatever reason, or the field coil is only hanging on by the skin of its teeth (again for whatever reason) and will only work if driven hard.

Still, it's a kind of progress and on the brightside I have to say the beast starts beautifully now - I was just trying to get it gently up to compression before kicking it and it roared into life . Lovely :)

Further ideas and views would still be most welcome.

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
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Re: Yet more E3N dynamo questions

Post by Pharisee »

Please forgive my ignorance (of most things electrical).... If you connect the dynamo to a battery as a motor... i.e. battery ground to dynamo body (positive in my case) and battery live to both D and F terminals, the dynamo should 'motor'... ok?
Should it motor in the direction that it would normally be driven or the opposite direction?
If necessary, what would I need to do to change the direction?

Thanks
John
I'm from the Fens.... Gimme six.
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Re: Yet more E3N dynamo questions

Post by aobp11 »

Further ideas and views would still be most welcome.
Alan, you gave the suggestion yourself in action 2): check motoring is in the correct direction. Alternative: feed F from the battery, run the engine, and check with a multimeter that D has the same polarity (w.r.t. earth) as F. When the motoring direction is not the same as when in use as dynamo then the output will be completely zero.
Note that with D and F connected (self-energising) and loaded with a bulb, you need considerable higher revs to light the bulb (as compared to F fed by the battery). Once lighted you can drop revs substantially before the light goes out. This is because the still cold bulb filament has low resistance and takes away a lot of current.

John, just reread the message by Groily.

Albert
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Re: Yet more E3N dynamo questions

Post by Groily »

Exactly as Albert says.

I usually connect a meter (using a suitable - eg 20 volts - scale) between the bridged F&D wires and earth first; then spin it to see if under (almost) no load it starts to produce. When/if it does start up, I hook a bulb on as well. It will light now more easily than if it had been connected from the beginning for the reason Albert makes clear.
(Maybe worth noting because of how confusing this subject can be, that although it's not relevant in this particular case the bridging of F&D only applies to 'standard' Lucas practice. Where, for example, a JG electronic regulator or other unit requiring the field coil to be wired between F & D instead of F and earth is fitted, the test is different.)

Depending on the wattage of the bulbs available, if you wanted to, you could see from connecting more than one (or a single big one) whether the dynamo is capable of supporting somewhere around its rated load. Around, say, 2500 dynamo rpm it should light loads of up to 40+ watts brightly while showing a voltage on the meter somewhat in excess of 7v (otherwise there would be nothing for the voltage regulator to regulate/maintain the battery were everything connected up as for normal running).

I've edited my previous comment re motoring to make it explicitly clear that the direction in which it motors must be the same as when it is being driven as a generator - as Albert also made clear.
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Re: Yet more E3N dynamo questions

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We have light! :)

After re-reading Groily's and Albert's advice I was champing at the bit to get home and check the sense of the dynamo output on the bike when the field was energised with the battery. Sure enough it was inverted (i.e. -7 volts ish not + 7 volts ish) when measured with respect to the field voltage. A quick swap of the brush connections (it was easier to do the brushes than the field coil with the dyno on the bike) and another test showed the correct +7 volts this time.

Armed with this success the next test was to connect the bulb. At first there was no luck but then, remembering yet more of those wise words, I gave it some more revs and Hey Presto! there was light, and all without the aid of my nice new field coil - never mind it will keep!

So, many thanks to you all for your input and particularly so to Groily and Albert.

On to the next fettle then which will be to get the electronic voltage reg working and to see that ammeter moving in both directions at last.

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
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Re: Yet more E3N dynamo questions

Post by aobp11 »

Congratulations Alan!
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Re: Yet more E3N dynamo questions

Post by Groily »

That is GOOD NEWS.
Also, I reckon it's quite good news not to have had to replace that field coil, as new ones can sometimes be a bit of a so-and-so to fit.
Fingers crossed for the next stage . . . .
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Re: Yet more E3N dynamo questions

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Well that's that then!
Small Amps.jpg
I've had my first go at sealing the chaincase today (it's still dry on the outside!) so I might take a look at the Jampots next.

Thanks once again gents.

Alan
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1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
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Re: Yet more E3N dynamo questions

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Dynamo update ......

After just over 5000 (joyous) miles in about 20 months on the AJ I noticed that it had stopped charging. Investigation into the brushes reveled that they were OK (barely consumed in fact) but the brush housing was full of metallic "grit" and, oh yes, the commutator bearing seemed to only have one ball in it!
Oh Dear Small.JPG
Nothing for it other than some Open Dynamo surgery which revealed total interior carnage resulting no doubt from only having one working bearing.
Not a pretty sight ....
Not Good Small.jpg
Poorly field coil.jpg
Time for another new armature, bearings, field coil ....
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Last edited by Group Leader on Sun Apr 14, 2019 5:41 pm, edited 1 time in total.
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
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Re: Yet more E3N dynamo questions

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You might recall that when I re-built the dynamo the first time I had a lot of trouble getting the main bearing on. Freezing and heating the armature and bearing respectively didn't help and I was concerned about the amount of force (applied with the aid of a large "persuader") that was necessary to drive the bearing home.

Subsequent investigation revealed the bearing probably still didn't quite make it home as you can see the witness of the inner race stops somewhat short of the armature step. Of course the trouble is the bearing is hidden by the end plate when you assemble it so you can never be sure!
Bearing small.jpg
I can only conclude that the ~1.5mm discrepency caused the commutator bearing to be side loaded which it didn't take too kindly to and after a grim battle during those 5000 miles gave up the ghost. :cry:

Anyway, after a thourough clean up of the body, end plates, brush housing etc and the purchase of the necessary new bits re-assembly commenced. Fortunately it turned out that a friend of a friend has the required pole expander and lever screwdriver to change the field coil, so he did and many thanks to him! :)

The new main bearing was a better but still too tight fit on the new armature and in the end (after some proper engineering sense having returned before I got the hammer out) I took a very light skim off of the bearing surface to make the bearing a good, tight but manual push fit and ensured that it was sure to go right up to the step on assembly before putting the end plate in position.
Armature Fettling Small.jpg
After studying the Lucas catalogue it became clear that the dynamo was originally missing not only the bearing retaining plate (mentioned in a previous installment) but also the bearing retention nut which comes in two forms, half and full. The need for this wasn't realised first time around because that bearing wasn't going to move on the shaft anyway! Of course now, with a more correctly fitting bearing, the need for it became more obvious. I don't know what thread it is but its ~15mm over the threads at 18tpi.

By yet more luck, my neighbour just happened to have a full nut (great neighbour!) but of course (and according to somebody's Law) in this application the half nut version is required. No problem, I'll just turn the nut thickness down to suit and all will be fine. Having done so, I used the old armature thread to clean the thread up so that it was a nice, smooth fit on the thread.

Unfortunately, the thread on the new armature had not been cut deeply enough and the nut refused to go very far onto the thread. Sadly, my neighbour didn't have a suitable die to run down the armature thread ...........

...... but he did have an 18tpi thread file which after a bout of manual fettling allowed the nut to do its job.

Having done that, re-assembly was completed and the dynamo was motored on the bench to check that it did and that it motored in the correct direction (see, I'm learning!)
All Done Small.jpg
It was then installed back on the bike and after a bit of fiddling, powering the field off of a battery and putting a bulb on the output the addition of many RPM caused the bulb to light.

Last job then was to re-wire back onto the bike and give it a test. Well, it sort of worked :?

No charge was produced unless the bike was travelling at more than 30mph or so and then, current delivered was proportional to speed. :? :? :?

I concluded that maybe, in the previous dynamo's death throws it had blown up the DV2 regulator so I ordered a replacement. Having done that, I thought I'd take the old one out in readiness which is when I noticed that the (positive) earth wire had parted company with its soldered on bullet. In for a penny and all that, I re-made the conection and gave it a try. It works perfectly :D

Looks like I'll have to get another bike to go around the new DV2 regulator when it arrives!

So, lessons learned:

1) Very rarely should you need a big hammer, if you do, there maybe a very good reason!
2) Modern replacement parts seem to be more of a "Starting point" rather than an "End Product" in some cases so keep your wits about you (anyone seen an oil filter?)
3) The DV2 regulator seemed to handle the abuse of one of its wires dropping off in its stride with hopefully no long term ill effects

Alan
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