Dynamo Rebuild

itma · Post by **itma** » Sat Feb 24, 2007 12:59 pm

Be kind to old folks Laurence and keep the text in a colour I can read

bjork · Post by **bjork** » Sat Feb 24, 2007 1:07 pm

Biscuit, my understanding of dynamos is the same as yours. I still sent mine to a specialist for repair-Paul Dunn, at Stoke on trent. He advertises in OBM. It reads; Dynamos Dynamos Dynamos over and over, and that's all he does.-I normally have ago at my own dynamos, they usually work after a good clean up and new brushes etc, but this one was a bit odd and needed a bit of extra fettle. It worked out quicker and more economical to have him do it. It came back looking better than I would have bothered to make it too. Anyway my point eventually,is; He said that I had been overloading mine too. So I went back to the lower load for a while, but decided I needed to see more in the dark as I was still commuting with that bike at the time. So now it is back to the previous set up, and seems to be coping. I still use it at night but not so much as before-maybe it'll last another decade or two?

Rikki White · Post by **Rikki White** » Sat Feb 24, 2007 9:56 pm

Many thanks to everyone for all your advice, now armed with a down loaded Lucas instruction sheet I’ve decide to have a go myself and keep my fingers crossed (and away from any hammers). I’ve now removed the dynamo from my bike (1959 model 31) and examined it more closely before diving in.

The body is marked 51 (1951?) but has what I think is a later brush mounting plate. The mounting plate has fractured near one of it’s mounting screws which allows one of the brushes to move about a bit but more worryingly it takes a great deal of effort to rotate the armature via the drive gear by hand (terminology courtesy of the date sheet!!). I’m hoping that it’s just a seized bearing but I’m not so sure and I’m a bit puzzled about the damage to the brush mounting plate, I’m hoping the dynamo hasn’t been dropped and something’s been bent or distorted. Fortunately I’ve access to a lathe at work so I can check the run out on the armature easily to be on the safe side.

I hope to be able to start dismantling it over the next couple of days family permitting and will let you know how I get on.

Many thanks again….

Rikki

Don Madden · Post by **Don Madden** » Sun Feb 25, 2007 2:45 am

HI, Rikki. You have a good start. If you run into something you don't want to deal with, you can put it back together & send it to a specialist.

If you pull the commutator side bearing use caution. The circlip is dicey to remove & likes to fly across the room. The bearing is a very close fit & will require persuation.

Broken brush holder plates are common. A new one is best but if you fit a used one be sure the rivets securing the brushes are tight.

Cheers, Don.

Biscuit · Post by **Biscuit** » Sun Feb 25, 2007 9:58 am

What circlip is that then Don?

TommoT · Post by **TommoT** » Sun Feb 25, 2007 12:37 pm

quote:
What circlip is that then Don?

Alan, it's the one from the piston, he has the cylinder off at the same time ! Edited by - TommoT on 25 Feb 2007 12:38:24 PM

laxy · Post by **laxy** » Sun Feb 25, 2007 10:10 pm

HI Rikki, Im following your post with intrest as Ihave a dynamo to rebuild from my 1960 model 31 which I think will be the same model as yours,Lucas K2F?
Mine stopped charging on the way back from last years international and when I dismantled it I made careful note of which field wire and which brush was earthed.But of course Ive lost the bit of paper now. Also I dont remember coming across any circlips.
Do let us know how you get on.
Regards Keith.

lawrence · Post by **lawrence** » Sun Feb 25, 2007 10:25 pm

I don't know what I was thinking of trying to dissuade Rikki, I must have had a brainstorm. It goes against everything I believe regarding classic bikes, that you should do all possible yourself.

I was told that overloading the dynamo is similar to connecting a wire direct across the terminals of a battery. Don't know whether that is right, I would have thought that the battery would just go flat as Alan says.

My '61 31csr has an E3L dynamo.

Good luck Rikki and keep the forum informed.Edited by - lawrence on 25 Feb 2007 10:27:58 PM

Biscuit · Post by **Biscuit** » Sun Feb 25, 2007 11:48 pm

Er............. K2F is a magneto.

If you shorted a dynamo, yes it would overload, burn up and smell like old socks. BUT YOU ARE NOT SHORTING IT OUT, The potential is controlled by the regulator and the battery controls the current. anything else is crap. I started my G3 this afternoon, which has a flat battery, however high I revved it, the ammeter never went to full deflection BECAUSE THE CURRENT IS CONTROLLED BY THE RESISTANCE OF THE BATTERY.Edited by - Biscuit on 25 Feb 2007 11:58:02 PM

Don Madden · Post by **Don Madden** » Mon Feb 26, 2007 2:23 am

To TommoT: No, the piston circlip fell down into the sump!

While the Lucas Service sheet shows a bolt retaining the commutator end bearing, all the many E3L dynos I have repaired had a small circular wire circlip retaining this bearing, There is little space to get a tool in to pry it out & it distorts easily.

To Alan. Yes, the control unit is designed to limit current to a safe level but a short can occur in the circuit between the dyno output & the control box. I had one such when the rivets holding the output brush loosend allowing the holder to touch the brushplate screw.

The instructions cover adjusting the voltage & cut-out point but do not mention adjusting the maximum current so I presume it is fixed.

I did have a failure once when I left on a run at night not realizing that my battery was flat. The double load of the lamps & charging a flat battery apparently overloaded the dyno, which on theory, should not have happened.

Don't forget, Joe Lucas invented the short circuit & the day-time only lighting system.

Cheers, Don.