I have no idea whether this will be of an use or interest to you, Steve … but we did have a go at understanding the contraption a while ago:

https://www.model-engineer.co.uk/forums/topic/stuart-dynamo-rotation/

MichaelG.

Ah, just read the old link – its an A/C dynamo but still, applying a few volts should make the armature flick to a stable position ??

A thin layer of non-magnetic metal over a pole piece probably won’t do much for it’s efficiency…

I agree with JH that the mom magnetic coating to the pole piece won’t be helping, at the very least it will increase the effective air gap in the magnetic circuit. The OP mentions that the magnet seems weak. Is it an old alnico type that has got tired? The link MG provided mentioned not removing the rotor without fitting a keeper, which you wouldn’t need with a modern magnet. Not sure how you test a magnet, but someone here will know. There was an article way back in around 2005 in ME about making a remagnetiser, but finding a modern magnet that would fit would be a lot easier. I wonder if a motor reeinder would have a remagnetiser?

Purely for convenient reference … I am re-posting the Stuart advertisement dated 1965

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MichaelG.

IMPORTANT EDIT:

Please also see here:

http://www.stuartturnersteam.com/Machines/Bottone/Bottone.html

This is a different one ^^^

A sanity-check please: What exactly is being built ??

New worry from me after reading Michael’s screen clip of the Stuart advert, which Neil Wyatt noted in #525915

The Note says ‘On no account remove the Armature without first bridging the field magnet poles with a piece if iron.‘, and Neil said ‘I think it’s worth drawing attention to the warning not to disassemble the ‘device’ without bridging the magnet pole pieces first.‘

This may be because the magnet is of the self-destruct variety.   Magnetic chuck instructions used to warn users not to dismantle the unit.  I believe the problem is that designing Alnico magnets for maximum pull requires the poles be positioned in a way that causes the magnet to eat itself if the flux has to jump a large gap.  These magnets are OK when fitted inside a machine that limits the gap, but the magnetic circuit has to be bridged if the magnet is removed.  How quickly the magnet eats itself depends on the pole design:  anything from rather slowly on an ordinary horseshoe magnet to almost instantly on a high-performance set-up.

I believe this self-destruct behaviour is peculiar to Alnico alloys, and modern super-magnets just keep going.

Steve mentions his magnet being “very weak”. Is it possible it was left for some time without a keeper before being fitted?   If so, replace it.

🙁

Dave

Leaving aside switching the meter to AC   and the magnet strength the location of the pole pieces in the gunmetal casting is very poor and certainly not helping things.
A multimeter alone is not a good test because it provides no load on the generator (Dynamo is a imprecise term). Use a small torch bulb if you can find one or connect a resistor of about 100 ohms in parallel with your meter.

It does sound like a combination of all three things. A DC meter will give no meaningful reading. A weak magnet will also produce very low output.
I’d be looking at getting a modern rare earth magnet for a trial at least. Make up a couple of iron or mild steel pole pieces to make it fit across the cast in pole pieces. A cyindrical one with a diameter similar to the width of the existing Alinco one would do. Make sure it has poles on opposite faces and isn’t a holding type with poles across the face.
Was the kit a recent purchase from Stuarts or old stock from somewhere? If a recent purchase I’d be asking them for a new casting based on the poorly located pole pieces.

Robert.

Great progress, Steve !

“ One small step for Man … etc. “

MichaelG.

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Please forgive me for mentioning it, but that casting looks disgraceful
… they should be ashamed.

You mention street lights (plural) so instead of a bridge rectifier you could have 2 leds in parallel but opposed polarity, each with a single diode. This will save you 0.6 of a volt and I doubt you will see any flickering as the frequency is quite high. If the generator peak voltage never exceeded 5v you could manage without the diodes, but I hope you’ll do better than that

Were the magnets really cast in-situ?  They look like ferrite to me.