Removing Dynamo Nut.

[Chief]

I have an old dynamo lying around (so not in a car) that I was going to try re-building (new brushes etc.).

I was wondering what was the recommended way of getting the pulley not to spin for releasing the nut?

If it were on the car I presume I could squash the fan belt to stop it spinning, however nothing I've tried to lock it has worked (and I managed to bend a couple of the fins slightly).

So before I risk damaging it further I just wondered what others might suggest?

I don't have a vice capable of holding it, nor do I have an air gun (both methods I've seen online for getting the nut off).

I had soaked the nut in plusgas overnight even before trying to remove it though I have not tried fire to heat it with fire as I believe it's currently more of an issue with the assembly turning than with any corrosion.

Thanks

[svenedin]

Without a vice to hold the body of the dynamo this is tricky but I have managed it without.

Put an old fan belt around the pulley and pinch it tight to prevent the pulley rotating. Then try to undo the nut. If this fails, get an assistant to help.

Once the nut is off it is still difficult to get the pulley off. You will need a puller. Make sure the puller goes behind the pulley and not in the V of it or you will destroy the pulley. Don't try to lever off the pulley; it won't work and you'll damage the pulley.

Stephen

[philthehill]

Hold the body of the dynamo in the jaws of a vice. Fit a ring spanner over the pulley nut. Give the outer end of the spanner a smart smack and the nut should come undone. You may have to smack the end of the spanner more than once but it will eventually come undone.
To remove the pulley - fit the nut on by a couple of threads - hold the dynamo by the pulley and smack the nut and the pulley should start to move on the shaft - make sure that you do not allow the dynamo to fall from the pulley so alleviating any damage.
Good luck.

[les]

Using a ring spanner, with it fully on the nut, then give the spanner a sharp hit with a hammer, a hard rubber one preferably. The sudden shock might shift it.

[les]

Opps, Phil just posted, similar !

[philthehill]

Great minds think alike

[les]

[svenedin]

Trouble is the OP has said he doesn’t have a vice….

Stephen

[les]

The shock is sometimes enough on its own.

[geoberni]

If you're looking to overhaul it, have you got a copy of the relevant Lucas workshop manual section?

The Landy Series I Club has a good technical library.
https://www.lrsoc.com/web/portfolio-ite ... op-manual/

Section A6 - Dynamos.
At the beginning of the part on Dismantling it actually states:

Dynamo.JPG (18.87 KiB) Viewed 79434 times

..before going on to explain how to press it out, but they clearly felt it was not something to be routinely attempted.

I've got a couple of spare Dynamos I picked up last year, but I've not had a good look at them yet.

[Bill_qaz]

Try using a chain wrench in the pulley groove to stop it turning, then spanner and hammer as suggested to shock the nut loose.

Screenshot_20251205-215544_Google.jpg (29.8 KiB) Viewed 79418 times

[Chief]

Thanks for the replies.

I'd not thought of trying with a chain wrench, though I'm not sure if mine is large enough, it's a three-chain oil cannister removal one and unlike your picture above, the chains are fixed to the handle, not separate at the ends.

I do have a rubber version of the chain wrench (again sold as being for oil cannister removal) which does have the rubber strap as adjustable/removable though the last time I saw the kind I have for sale, it was now being sold as a jam jar lid removal tool, which makes sense as they (two pack small and large) were always pretty useless when it came to oil cannisters (smooth, polished rubber with no grip).

As to the vice, the one I have isn't large enough to take the dynamo securely or I'd have used it, and as to old fan belts, I don't have one.

I did previously try shocking the nut yesterday (including with a rubber mallet - if I'd found my 4lb lump hammer I'd have been tempted to try it) though I was using a socket/ratchet rather than a spanner, but even with the plus gas the whole assembly moves so definitely need to get it to stop moving. A spanner would probably be more effective since it might not fall off as easily as the ratchet when hit.

[serowman]

Never hit a RATCHET

[MM1949]

Did that nut get removed!..

[Chief]

As of yet, no, due to on-going health issues, and to add to the hilarity I've now caught a cold .