discomikey Posted December 12, 2012 Share Posted December 12, 2012 this morning, i had to jump start my mates P-Thirty-Crate diesel, as usual... and something strange happened. when i revved my engine, the axuiliary belt (rear crank pulley one) started melting off the crank pulley. normally on a disco engine, this supplies the A/C pump, which when on creates a fair bit of resistance, but on my conversion, it only supplies the alternator, and a seperate belt off the front crank pulley groove supplies the water pump. (series coversion) so in theorey, the alternator must have been creating the resistance to make the bottom belt pulley slip. and start to melt the belt and fill my engine bay with smoke. this is unusual, because alternators spin relatively freely. whats more unusual, is that after 10 minutes it stopped. any ideas. P.S. it would have been around 0<5 degrees when it happened. cheers Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted December 12, 2012 Share Posted December 12, 2012 Your belts lose or worn I would think. Alts take alot more to spin when there producing oooomph. Quote Link to comment Share on other sites More sharing options...
discomikey Posted December 12, 2012 Author Share Posted December 12, 2012 it wasnt flapping about as to suggest it would be loose but ill check the tension when i decide its warm enough to go outside. being at uni i dont have my nice warm workshop and it is in need of some TLC. (not had a spanner on it for an extremely long time for a land rover) Quote Link to comment Share on other sites More sharing options...
ejparrott Posted December 13, 2012 Share Posted December 13, 2012 It'll be the load created on the alternator. Alts don't spin that freely when you ask them to supply 100 amps, connect one up to a test rig and try it! Haven't spannered my 88 in months, she's running fine Quote Link to comment Share on other sites More sharing options...
Tanuki Posted December 13, 2012 Share Posted December 13, 2012 If the alternator's dishing out 100 amps at 12 volts (because you've drained the battery for whatever reason) then that's 1.2 Kilowatts - assuming the alternator is 100% efficient. In practice it's probably more like 70% efficient - so to get 100A@12V out you'll need more like 1.5 to 2 Kilowatts of power put in via the pulley. That's a hell of alot of grunt to transmit via an old-style V-belt. It's one of the reasons the auto-industry swapped to the serpentine poly-vee belts a couple of decades back. (other reasons being longer life and less noise). Quote Link to comment Share on other sites More sharing options...
discomikey Posted December 13, 2012 Author Share Posted December 13, 2012 It'll be the load created on the alternator. Alts don't spin that freely when you ask them to supply 100 amps, connect one up to a test rig and try it! Haven't spannered my 88 in months, she's running fine dont get me wrong, mines running fine after so long with no spannering. its more things i have to do to it like extended breathers and snorkel (fed up of filling everything with water and nearly drowning freshly rebuilt engine!) Quote Link to comment Share on other sites More sharing options...
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