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MG TD TF 1500 - Lucas Generator Test Speed

I'm switching back from a Dynamator to a Generator.
It's part of a test, I may leave the Dynamator in place. I'm installing a used generator from Abingdon Spares along with a used Voltage Regulator. I dug out my copy of "Lucas Generator and Control Box Tests" and put it use.

All of a sudden I've run into a snag.
Attached is a copy of Page 3 of the Lucas document. Notice the text under the 'voltmeter CONNECTION TEST 1' column:
...Start engine and raise speed until generator is running at approx. 3,000 rev/min.

Similar language is used throughout the document. The question is, "Do they mean the revolution speed of the generator, or the engine?" A number of tests are run at '(approx. 3,000 rev/min)'.
In regulator settings I find a very hairy tweak at about 2500 engine rpm.

I found a Chicagoland MG Club document, "What Generators Do and Regulators Ought To" by Michael Grant of Moss Motors. In it he writes, "...(about 1000 generator RPM or 750 engine RPM).., so 3000 generator might be ~2250 engine.

Bud

Anybody happen to know the ratio between the circumference of the crankshaft pulley and the generator pulley?

Bud



Bud Krueger

Bud,

You don't need to worry about the circumference of the pulleys, the ratio of the diameters gives the same value. It just means that you remove "PI" from the equation. The pulley dimensions are:

crank dia = 95mm
generator dia = 83mm

So to find the engine speed for 3000 rpm generator speed, the equation is:

83/95 X 3000 = 2684

The document uses the word "approximately" this indicates the speed does not need to be accurate, so we can ignore the inaccuracy of the rev counter

John








J Scragg

And just for my information, are there different size generator pulleys for Lucas generators so I might be able to get a bit more speed at idle?
John Quilter (TD8986)

John, I'm not surprised to have you catch me on the diameter*pi issue. I wish that it were so simple. The greatest problem is the use of that word 'approximately'. In the vicinity of the regulator adjustment a variation of 100 rpm can readily result in a difference of 17 volts versus 16 volts.
The standard value for the diameter of the dynamo pulley is 3.22 inches (81.8mm). The crankshaft pulley standard is 3.75 inches (95.25mm), a ratio of 0.859. 3000 rpm * .859= 2577 rpm. Your 83/95 ratio would give 2621 rpm. Looks as if an
engine speed to use is 2600 rpm.
The adjusting screw is very touchy around that speed.
I'll have to dig out my StroboTach and see what shows up.

I'm beginning to give serious thought to using the setting procedure from Page N.12 of the WSM.
Bud
Bud Krueger

John Q, check the 2009 archive entitled "10deg BTDC". There's a discussion along that line in there. Bud
Bud Krueger

FYI, the Reproduction Generator Pulley from Abingdon Spares measures 3.22 inches in diameter. Bud
Bud Krueger

This thread was discussed between 21/11/2021 and 27/11/2021

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