Need help with generator tester

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Model T Ford Forum: Forum 2016: Need help with generator tester
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Eaton on Thursday, December 01, 2016 - 10:04 pm:

Hi everyone. I thought I would build a generator tester and I did however I think it doesn't work. Need advice on how it should work. At present Wooden cradle with brass connector for ground sits on lathe bed and geared to lathe on high speed. Power from
6 v battery positive terminal wired to ammeter. From there to post on generator then from ground back to battery. What have I done wrong


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker, Ramona, CA on Friday, December 02, 2016 - 01:15 am:

Sounds like a ground problem. The case must connect to the battery negative, I didn't really understand how you wired the ground.
Try an analog voltmeter. Connect the -ve to the battery negative then check 0 to the generator case, 6 volts at the battery +V and slightly more at the generator output...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker, Ramona, CA on Friday, December 02, 2016 - 01:18 am:

One other thought, the generator runs 50% faster than the motor, so at 1000rpm on the engine, the generator runs at 1500. I use a standard electric motor running at 1750 and it works fine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Eaton on Friday, December 02, 2016 - 08:11 am:

Thanks Tony, The ground could be questionable. It's that brass strap on the right that the starter rests on (The strap goes all the way around under the gen body). May not be good enough. Also I have the lathe turned up to the top but that may not be fast enough yet. Back to the drawing board. Thanks again, John


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Eaton on Friday, December 02, 2016 - 10:07 am:

I guess I have another question Do I have to zap or short the generator or anything to activate the field coils?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker, Ramona, CA on Friday, December 02, 2016 - 10:55 am:

If it is newly rebuilt, the residual magnetism may not be sufficient to start generating current. The solution is to apply battery voltage to the generator terminal, bypassing the cutout, for about three seconds.
I didn't mention it earlier as I couldn't see a cutout in your setup.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Friday, December 02, 2016 - 11:22 am:

I would put the cutout on, add a battery and better ground. Running at best lathe speed even under what the top engine RPM will be should put you in the ball park. 1200 RPM on the lathe would = about 20MPH (about 800RPM engine speed) on the car. Did the generator motor when voltage was put to it? Did you set the null point on the brush plate? The point where it does not want to motor ether directions but wants to rotate clockwise. Flashing it as stated above would not hurt.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Eaton on Friday, December 02, 2016 - 11:52 am:

Newly rebuilt (but still learning) Set armature to null. This tester will then allow me to do a preliminary set on third brush before installation. Didn't think I would need regulator to do a quick test so did not include one in circuit. Using a standard 6 volt battery not shown. Will play some more this afternoon. Thanks, John


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Friday, December 02, 2016 - 12:40 pm:

Hook it up just like it would be if installed in the car.

If you don't have a cutout installed you are applying battery voltage to the generator full time so it's trying to motor at the same time it's trying to generate.
The cutout is a one way switch, allowing voltage to travel from the gen to bat not the other way. When the cutout is open carries the generator output to ground thru a very fine shunt wire or other means.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Eaton on Friday, December 02, 2016 - 02:05 pm:

I will add a cutout and try as soon as I repair off shore jumper cables


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen, South Texas on Friday, December 02, 2016 - 02:23 pm:

What ever you do, don't disconnect the battery while the lathe is turning or that generator will spin right out of your wooden cradle, or try to. I would make an effort to improve the hold-down method. The generator will produce significant drag (load torque) depending on the current output.

(Message edited by kskopsky on December 02, 2016)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Friday, December 02, 2016 - 04:21 pm:

John
Neat set up.
I suggest using a FunProjects dash ammeter for a 1919-1925 Model T. They have a high quality movement and are exactly calibrated. Reproduction improved Model T cutouts are notorious for their poor quality/accuracy.
I suggest a diode cutout. When you need to polarize the pole shoes or motor the generator you can simply connect the generator wire to the generator output terminal.
A good ground to the generator case is important.
As suggested add some form of generator case hold down. The Model T generator draws 1/3 HP under normal operating conditions and much more if allowed run with no load.
1750 RPM is approximately 28 MPH which is ideal for testing or setting the Model T generator.
I do not recommend a FunProjects Voltage Regulator for a generator bench tester. The VR assumes the generator is working as designed and newly rebuilt generators units are usually not correctly set up or working properly.
I built my own generator tester so if you run into trouble testing generators give me a call.
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Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Friday, December 02, 2016 - 04:23 pm:

Here is a photo of the generator case holding fixture.
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Top of pagePrevious messageNext messageBottom of page Link to this message  By John Eaton on Sunday, December 04, 2016 - 04:07 pm:

Neat tester. Thanks
. I will tweek some more/ There are still self generated bugs and gremlins in the whole system. Time to try another generator to make sure I have a benchmark before I go much further. I have however added a new diode cutout. Still a problem. Will also add better ground and safety clamp. Regards, John


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Monday, December 05, 2016 - 08:12 am:

Here is a cheapy home built that works well.

A pulley replaces the gear for a rebuilt generator test.

This arrangement works fine to check or adjust a generator output.

Generator


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