Righty everyone, there are some good brains on here so I come with a question I hope you can help with.

I have here a big turny thing that looks like an electric motor. However I am told it is a dynamo off a big Paxman locomotive engine. It doesn't say much on it, just 24v, "slow rotation" and "counter clockwise" and "CAV".

It's fluffing heavy, I reckon on about 60-70kg.

I thought it would make a good mate for my Lister 6.5hp engine so I could generate lots of DC.

But I can't figure out how to wire it.

It has four terminals that look like this:

[photo]118029[/photo]

Two big ones, red and black, and two small ones, just brass.

If you put 24v from a battery to the two big terminals, it spins up like a motor, rather fast. Either polarity, it spins the same way which is weird.

If you put a volt meter over the big terminals and spin it from an engine (belt drive), you get a few volts between them, around 3-4 volts, no more, even when really spinning.

Nothing comes out the small ones.

If you connect a 12v battery to the small ones whilst the engine turns the alternator, you get a quick blast of volts over the big terminals but only for an instant then it's back down to 3-4 volts again.

If you connect each of the big terminals to each of the small ones whilst the lister spins it, you get about 125VDC between the big terminals. I discovered this the hard way, as I was holding both at the time. That hurt.

Using a wire instead of my body this time, shorting the big terminals obviously causes a massive breaking effect as the lister struggles to maintain RPM and it moves to stall.
It's clearly making big amps when I do this but those amps are not going through the wire I am using to short it, I'm only using a thin bit, it's not even getting warm. But it does arc on connection.

I dunno people, how the heck does one wire this up to get power from it? DC, AC, 24v, 120v, I don't care I'll use it for something if I know how it is supposed to be wired.

Any ideas? :confused:

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Wild guess, possibly off a BR Class 14, aka D9500? You might get some help by pursuing that avenue online, poss with some pics of said dynamo. You might also find it's worth more to them as something quite specific, than it is to you as just a general generatory thing.

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Errr well I couldn't tell you what loco it is off, it might not even be off a loco at all, maybe a big genset. The guy said it was definitely a big Paxman engine anyway and it's certainly a large dynamo.

I don't really know many loco buffs, if you know anyone who might find it interesting then please pass the photo on.

Further to my last post I've rerun it on the Lister, with each little terminal connected to a big one and sure enough you get 125vdc (ish) across the big terminals. I wired it up to a 500w site-light (a 110v halogen thing) and it lit up nice and bright, so there is certainly juice there.

The body of the dynamo really does get quite warm though, after maybe 10 mins running it's almost too hot to touch.

Not sure if that's normal or not...

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Would it be around 7 inches diameter and 15 inches long?

The red/black are the output terminals and the smaller brass studs are the field connections. Suggest there was something like a car type voltage regulator to control the field voltage.

Looks like it may need an external regulator. Hint from:-
https://www.bowersautomotive.co.uk/Cat_Heavy-Industrial-Marine-Standby-Generator-Pump-Engine-Equipment.pdf 
(search within page for d07x24/2)

If correct then output should be 25 amp at 24 volt and should probably run nice and cool.

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Would it be around 7 inches diameter and 15 inches long?

The red/black are the output terminals and the smaller brass studs are the field connections. Suggest there was something like a car type voltage regulator to control the field voltage.

Yes that's about the size. I figured the little ones will be to energise the electromagnets. Not much happens when supplied from separate DC, but when supplied from the big terminals the voltage shoots right up. I can get it to reach 200vdc if I open the throttle on the Lister a little! It only runs at 600rpm as its governed standard.

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In case it's useful information ...

https://www.bowersautomotive.co.uk/Cat_Bus-Coach.pdf  list a

CAV Control board for D07X24 Low Speed Dynamo.

Use only with battery. 18 Cell Acid or 18 Cell Nife. Capacity 60-220 A.H.

Max lamp load 25 amps at 24 volts.

Dave

If finding a regulator is a problem you could probably control the onload output with a suitable rheostat but loss of load whilst running would be a problem. Should be ideal for a string of lamps but more issues if you want to charge a battery.

(This may be bollocks as I've not worked on this sort of kit for around 50 years)

So far as I can make out it's a split field DC generator, normally each set of field coils would be fed via its own regulator circuit, thus allowing more current to be generated at low revs than would otherwise be generated if all the field coils were connected in series and fed via one regulator circuit.

Generating voltages higher than it was designed to do might compromise the generators electrical insulation, which from the looks of it is likely to be old.

Lozz.

I would say the small terminals are the field, and it's getting hot because with no regulator you're putting the full output (from your lamp experiment probably over 100v with no regulator) across a 24v field winding.
Adding resistance in series with the field will get a relatively sensible, but un regulated output, but it will need to be quite high power resistors.
Motoring it with no field current will produce high speed, but low torque, as you are just using the residual magnetism. On a D.C. motor you decrease field current to increase speed. I might be able to dig out a circuit for a solid state regulator that will work. I used it on a dynastart on a small tractor a few years ago. It isn't complicated.
On another subject, we are in the process of rebuilding 'monty' with a new galvanised chassis. Just had a load of bits, including bulkhead dipped at a local galvy, and are very pleased with the results.

This part may work, unfortunately it does not specify for a 'dynamo'.

https://www.ebay.co.uk/itm/Land-Rover-LUCAS-CAV-24-VOLT-REGULATOR-PART-No-1861A524-STC516/332287520682?hash=item4d5de12faa:g:q9MAAOSwqu9VLSYh 

Thanks so much everyone for your brilliant responses! Particularly impressed that some of you even found a supplier for the regulator that's supposed to go with this dynamo. I've sent them an email to see if they still have stock, I hope so, and hopefully the regulator will be 20 quid not 2000 quid.

Worth getting it all hooked up right, it looks like it would work forever and when paired with two big 12v SLA batteries and a big 24v inverter that would make a nice setup to go with the Lister B. I'll need a new pulley though as belting off the flywheel is clearly too fast!

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I would say the small terminals are the field, and it's getting hot because with no regulator you're putting the full output (from your lamp experiment probably over 100v with no regulator) across a 24v field winding.
Adding resistance in series with the field will get a relatively sensible, but un regulated output, but it will need to be quite high power resistors.
Motoring it with no field current will produce high speed, but low torque, as you are just using the residual magnetism. On a D.C. motor you decrease field current to increase speed. I might be able to dig out a circuit for a solid state regulator that will work. I used it on a dynastart on a small tractor a few years ago. It isn't complicated.
On another subject, we are in the process of rebuilding 'monty' with a new galvanised chassis. Just had a load of bits, including bulkhead dipped at a local galvy, and are very pleased with the results.

Nice one I'd love to see the end result!

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https://www.blocklayer.com/pulley-belt.aspx 


Lister HA2 loaded at 600 Watts normally charges a 660 Amp/Hour battery bank.

Thank you for that! Nice machine, looks like it's on a narrowboat.

My Lister is a petrol hit-and-miss job, hopper cooled and twin flywheel. Lovely old engine but will just run forever.

I've made a short video of myself restoring a Petter generator here:



You can see the Lister in the background on a number of the shots if you are so inclined.

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Yep, drives a 60 foot narrowboat.

Very nice restoration on the Petter.
Lister 'B' series are pretty solid lumps, last forever.

Edit: Is the Petter the one that's difficult to start?

Okay, well I got an email back from Bowers and they do have those regulators in stock but the sticking part is that they want 834 pounds for one. So that's not happening.

I have found something else on eBay, it's a 16 amp one made by CAV for a low speed dynamo, they want 122 quid or best offer:

https://ebay.us/rtdbbg 

I'd be prepared to offer them 100 quid for it, that's about the limit of what it's worth to me to get this dynamo doing something useful.

But do you think it would work? Are they easy to wire up?

Thanks again everyone for your help

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I'd be prepared to offer them 100 quid for it, that's about the limit of what it's worth to me to get this dynamo doing something useful.

Plan B: Visit scrap yard, get alternator and regulator from rear end crash low mileage car. Also get caravan type inverter. Note size of car pulleys - set yours so that its doing about the same rpm as it would have been in the car at about 2000 engine rpm. Result 240AC at whatever wattage inverter is rated for. Part finance it by selling the CAV.

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"Lister is a petrol hit-and-miss job", driving a car alternator is close to 'Heresy' to old Lister fans, lol.

It's your boat, do what the f**k you like with it!