CAV dynamo

I came by a massive CAV dynamo last evening. Over a foot long & about 8" across, it is a two handed grunt to lift it & it came complete with its regulator. It lacks a pulley, but the input shaft is an inch thick. The massive double brushes are disposed at 90o to each other & there are only two sets.

It is 12 Volts & is "low speed" according to the plate. The regulator speaks of "batteries" and 25 amps.

It sits in two neat cast iron cradle brackets and is strapped to them by two flat hold down steel straps. Although rather automotive in appearance, I'd say it was not used in that context - aside from anything else like mountings, it lacks any oilyness! I wonder what its original application was?

How do I figure out what "Low speed" is? If I motor it & check the speed with a tachometer, will that be accurate enough?

It is an ideal bit of kit for an engine to drive, but can its output be only

25 amps considering its bulk?


Kim Siddorn

Reply to
Kim Siddorn
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It's an early bus or truck dynamo by the sound of it.

If you can get the details off the plate, I'll look through my CAV service manuals and see what I have for it. There are about 10 dynamo sheets IIRC.

We have a 60A 28V alternator sitting on the bench outside my office, AC203 CAV, made to fit onto a Gardner bus engine and fully waterproofed.


-- Peter A Forbes Prepair Ltd, Rushden, UK

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Reply to
Peter A Forbes

Sounds like something from a bus or marine engine, except that 24V would be more likely in that context and for that size. I've seen CAV 'low speed' dynamos before, but can't really help on what it means. Serial/type number?


Reply to
Tim Leech

There were some large vehicles with lower voltage electrical systems made. Mostly a long time ago. Caterpillar made a D8 crawler with a 6 V system at one point:

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Best wishes,


Reply to
Christopher Tidy

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