Diode

[FlatheadTed]

This might be a Model question but I have used the Diode available from Snyder's on the Model a Generators, but have found they heat up .If you fit the covers on there's no cooling and can burn out , any one experience this ,Ted

[JM 35 Sedan]

Are you talking about using them inside of a cut-out on top of the generator?

[FlatheadTed]

Yes Jim ! Thanks ,Ted

[JM 35 Sedan]

I guess they could run hot if there is a heavy current demand on the electrical system, and third brush is set to max. I had purchased some diode kits to use in the cutouts on my 35's, but once I found out about the Fun Projects electronic regulators, I use those on all my cars.
Maybe you could mount your diodes on larger heat sinks that would still fit inside the cutout can, but do a better job of soaking the heat from the diode.

[Kurt in NJ]

I just used a diode out of a junk delco alternator, gutted the windings out, drilled ahole in the reley frame, pressed the diode in ---never measured the temperature, but it had been working at 18 amp for awhile, now 14 amp----untouched over 30years, so if it is getting hot it is within design allowances

[Mike V. Florida]

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Take a block of aluminum. Drill the hole for the diode. Mount the heat sink to where the instructions say to mount the diode.

[flatheadmurre]

Tumb rule for heatsinking semiconductors...if you can touch it and count to 10 it´s ok.
And that is fairly hot...

[Paul Bennett]

Silicon power diodes have a voltage drop of 0.7v. So with 20 amps current the power dissipated by the junction would be approx 14w. Removing the heat into a heat sink depends upon how the diode is made elsewise the temperature will soon destroy the diode junction.

For a power application best NOT use an axial diode but one with metal tab which has a hole to mount to a heat sink, or which has a stud to screw into a heat sink.

[FlatheadTed]

Thanks for the replies' .Here's a couple of shots .I drilled a air vent in one ,if the battery is fully charged and you are running at say 8 to 15 Amps maybe that's were the excessive heat comes in Ted

[Karl]

Ted I ran one on my first Model A-Did 12 ,000 miles and no overheating I sold it to a guy in Napier who I am still in touch with and he uses it as his daily driver and has done for the last 5 years with no problems. From memory was mounted pretty much as yours is -Karl

[Kurt in NJ]

That is not original cutout, the metal frame the diode is mounted on has less mass and is mounted on a thicker insulating block. -- try modifying an original cutout

[FlatheadTed]

Thanks for all the replies ,I like the idea because its a $2 item ,I have only burnt one out ,I think I will run two one as a back up ,Ted