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No. 2 Mk 2 Generator wanted


jim fl4

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  • 1 month later...

Niels as you know you can easily test the Generator No.1 either running it as a motor or energising the field winding then spinning it & observing the voltage output.

 

Of course neither option exists on the Generator No.2 because of the gear box. With the pulley it weighs in at just over 25kg so is not a lot of fun changing it especially getting that blasted lower oil pipe connected!

 

It would be possible to energise the field winding & rotate the pulley to test for an output. Fitting up some sort of jig with a drive source of sufficient torque to rotate the pulley would be a pain & it would rule out an in the field test.

 

You cannot spin the pulley, the best I can manage is to sharply turn the pulley through 180 degrees. But I thought this should be sufficient to give some sort of output to assess if it was a useable generator or not.

 

Using a variable voltage bench power supply I energised the field winding to get only a modest current flow. I found that at 7.0 volts it drew 3.14 amps. After a few minutes of warming up it settled down to 3.09 amps, by Ohms Law this gave a warm resistance of 2.26 ohms.

 

This is spot on as the Inspection Standard quotes 2.02 - 2.48 ohms. Although no temperature is quoted, manufacturing standards would probably give a more precise tolerance, it may be that the range quoted also gives a tolerance for extremes of temperature.

 

Measuring low resistances with a multimeter is notoriously difficult to do as the scale is limited & there is the resistance of the leads & integrity of the plugs & the contact you make on the item being tested. So drawing a current & measuring the voltage is a good way to measure low resistance.

 

So to energise the field I connected:

 

Pin C 7v +ve

Pin B -ve

 

Pin A to voltmeter +ve

Pin B to voltmeter -ve

 

By steadying the generator with one hand & sharply turning the pulley with the other, I was able to produce one volt output. I tried this several times on two generators but one volt was the most I could achieve. This seems to be a satisfactory outcome as both generators provide good 28v or so output.

 

Not the most elegant of tests but I like it because it is a "bloke in the shed" style of test that hopefully can be easily repeated be it in the shed or when going to view a take-off generator.

 

DSC00209a.jpg

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