Cut out question

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Model T Ford Forum: Forum 2012: Cut out question
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Housego (United Kingdom) on Tuesday, September 11, 2012 - 04:24 am:

I am looking to convert my old cut out to a diode version as shown in the MTFCA electrical book. I can only see advantages to this over the conventional contact type cut out unless anyone knows better? The diode recommended IN2129 is long unavailable now, can anyone recommend a suitable replacement diode please? I know replacement cut outs are available and I have one of Johns excellent VR cut outs. I am simply doing this as a back up with my old faulty cut out. Thanks in advance. John


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer on Tuesday, September 11, 2012 - 07:13 am:

John; I always use ;Bosch diode # 0 270 101 418
0682
Toon


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Tuesday, September 11, 2012 - 07:25 am:

A solid state cutout would be a reliability improvement over the mechanical one, but still leaves the probability of over- or undercharging the battery.

I can't answer your question, but it just occurred to me it might be possible to make a manual voltage regulator for third brush generators, where the driver could adjust the gen output on the fly? Without thinking about it too much, it seems a rheostat and and maybe an accurate voltmeter would be all you need.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Stitt-Southern Oregon on Tuesday, September 11, 2012 - 10:55 am:

It you were local and walked into my shop I'd just give you one. Check in at an alternator/starter shop.
Ralph I never looked into it but later Ford generators had a screw on the back that moved the third brush. It is on a little rack. Might work on a model A. Never compared the two.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob McDonald-Federal Way, Wa. on Tuesday, September 11, 2012 - 11:08 am:

Does it bolt directly to the gen or is there insulating washers between them, I have one of each one must be incorrect. Thanks

Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cameron Whitaker on Tuesday, September 11, 2012 - 11:12 am:

There are LOTS of diodes on the market that will work. I'd say just make sure that you use one rated for at least 40 amps and 100 volts. Going too big on a diode won't hurt anything!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cameron Whitaker on Tuesday, September 11, 2012 - 11:15 am:

Come to think of it, I made my cutout out of a full-wave bridge rectifier that I bought from Radio Shack. I only use two of the diodes in it that I connected in parallel. The other two don't do anything. I've never had a problem with it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Housego (United Kingdom) on Tuesday, September 11, 2012 - 03:16 pm:

Thanks chaps, as usual all usfull and informative comments.

Toon that's a real neat job you made of that cut out,the diode fits in nicely, Im assuming its the press fit type that are used in modern alternators but I have not found that particular Bosh part number.

John


Top of pagePrevious messageNext messageBottom of page Link to this message  By JohnH on Tuesday, September 11, 2012 - 09:33 pm:

The ideal type to use is a dual Schottky diode (as used in computer power supplies) because of lower voltage drop across it (about 400mV), as compared to a typical silicon type, which results in less heat dissipation. Being in a T0220 package also means easy mounting without having to make any brackets. This is what is used in the FP VR. A typical type would be MBR30H100CT, rated at 30A and 100V.


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