High revs kills alternators?

[Sam_Q]

In my car I have had one 4age 20V silvertop engine after another with all sharing the same 8600 rev cut which they used to see pretty often. When I got around to taking apart a bad alternator I had I found that instead of the usual bad brushes or regulator the windings in the armature itself has burned through in one section.

Now for quite a long time I ran only a lowly 30A fuse on the output so it wasn't even being used to half it's rated capacity. Also it has a decent gap from the extractors so it shouldn't get too hot. The bearings where in good condition still.

Could the extended high revs cause such a thing? Too much induced voltage causing insulation break down? I calculated that at peak revs it's spinning at 20,000! Doesn't seem to be likely explanation to me, so perhaps just long term use/fatigue?

Luckily for me I found the spare 7AFE alternator I had laying around had the same internals.

[xero]

no idea sam, but ive had the same alternator for must getting on 6 years now. for the last 3 its been seeing 9000+rpm regularly with no issues. only difference between mine and yours is i have a larger pulley on the alternator which would slow it down some. been through 5 starter motors though...
i can take i a pic if you want.

[ctrain]

well alternators only handle up to 20k rpm, anything higher would probably burn the regulators/rectifier out. Chuck a bigger pulley and see how that goes, yes it will go slower but wont make a difference to output.

[LittleRedSpirit]

Yes if the bearings were failing that says one thing, but if the electronics are what fails then Id say this sounds like a great plan.

[Willofan]

Alternator is charging at its optimum from about 2,500 engine rpm, so slowing it down won't hurt it. My 4AGE group A runs a 100mm crank pulley which drives a 100mm alternator pulley (1:1) and it revs to 9,200 before engine cut kicks in.

I have seen armatures falling apart with centrifugal forces and heat self destructing within themselves. Brushes and bearings just aren't up to continuous high revs either.

[allencr]

What's a centimeterand/or milligram of their wire weigh if ya wanna run them at 10 > 20 thousand RPM?
A kilogram or close on that little wire?

[Sam_Q]

I was planning on making an oversized alternator pulley that was about double the size, I was curious about this though.

xero: what kills those starters? any idea? do you have solid engine mounts?

[trdee]

his headers sit right up next to the starter. probably doesnt help..

[Sam_Q]

If that's the case I might have a solution for that real soon. I am working on a drop in 1.2kw gear reduction starter that fits right up to a T50 and sits closer to a 4A / 7A than any OEM option. Well I hope it works out as I want one for my own car!

Do you guys have any suggestions for a good size of alternator pulley to go for? if double good? As I said earlier I have very little load but it would still be a road going car. Just curious is there a power difference slowing down an alternator?

[trdee]

If that's the case I might have a solution for that real soon. I am working on a drop in 1.2kw gear reduction starter that fits right up to a T50 and sits closer to a 4A / 7A than any OEM option. Well I hope it works out as I want one for my own car!

Do you guys have any suggestions for a good size of alternator pulley to go for? if double good? As I said earlier I have very little load but it would still be a road going car. Just curious is there a power difference slowing down an alternator?

yeah he's seen your facebook posts on it

[Billzilla]

Do you guys have any suggestions for a good size of alternator pulley to go for? if double good? As I said earlier I have very little load but it would still be a road going car. Just curious is there a power difference slowing down an alternator?

As long as the alternator puts out enough volts/amps at idle, it's enough.
I tried running the alternator at a little below engine speed on my last 4AG and it was just enough to keep on top of the power demand at the 1050 rpm idle with all the lights, fans, etc, on.

[xero]

his headers sit right up next to the starter. probably doesnt help..

If that's the case I might have a solution for that real soon. I am working on a drop in 1.2kw gear reduction starter that fits right up to a T50 and sits closer to a 4A / 7A than any OEM option. Well I hope it works out as I want one for my own car!

Do you guys have any suggestions for a good size of alternator pulley to go for? if double good? As I said earlier I have very little load but it would still be a road going car. Just curious is there a power difference slowing down an alternator?

that and compression.
ill send you a PM Sam.

[trdee]

T3 do underdrive pulleys.