Monday, 22 November 2010

Dynohub (GH-6)

This is a Sturmey Archer GH-6 dynohub from 1956. It was rescued from a skip by my dad and although we really have no use for it, it’s nice to clean it up, take it apart and have a look.

It was in its original moss-ridden rod brake rim with a lot of broken spokes.
The bolt cutters made light work of those.

Before crud removal

After crud removal.

Dynohub logo.  The text ' Do not remove magnet without keeper' is a bit cryptic, it means dont seperate the magnet from the armature unless you have a big iron plug called a keeper. This maintains the magnetic field in the magnet. Best to just not seperate them.

Date stamp. (September 1956)

Removing the magnet fixing screws after undoing the locknuts (tiny little bolts and washers on these)

The magnet & armature removed. These should be kept together, if they are separated then the magnet will lose half of its power in an instant.

Inside the shell – filthy.

All cleaned up.

Back together and giving it a test. It works perfectly even after 54 years. I’m not planning on using it for anything as it’s basically redundant compared to modern dynamo hubs. But it’s a nice piece of historic kit and doesn’t deserve to be in the skip.


  1. I have an old AWG 3 speed hub which I have been intending to use for something, possibly a Twenty. Need to test it still works first though, pleasingly enough the gears are good to go. I wouldn't expect any less.

  2. There's not really much to go wrong with them. I think the magnet does lose some of its power over the years though and if someone in it's past has removed it from the armature then there's no way you can get that power back without using somekind of terrifying machine of death to do it.

  3. Wat great bits of kit these are. I have an AG3 dynohub and whilst it's not connected to any lights it keeps my bike zipping around London some 55 years after it was built. I'd like to see a piece of modern equipment that will still be around in 2064! Great pics, thanks for sharing.

    (PS Having had your fun dismantling it you could probably get good money selling this on eBay, they are quite desirable!)

  4. Who made this dynohub, please? It is not visible on the fifth picture from above.

  5. My GH6 seems to run my Edelux just fine surprisingly enough. I might have to onsell my sondelux if I dont need it!

  6. I recently acquired one of these and fitted it to a BSA 'Twenty' previously having a 'bottle' type dynamo. In the absence of more info, I would advise not separating the magnet and armature. The lights were somewhat dim compared to previously but I think the 'Dynohub' is 1.8W as opposed to most 'bottle' type dynamos which are 3W. The former is a bit 'olde-worlde' though has the benefit of less drag and no wear on the tyre side-walls. Not sure whether the lights would be legal but fitting 6V .15A bulbs front and rear should load the unit correctly. If the magnets are indeed weak, how to re-magnetise we might leave to another day.