afrooster Posted November 1, 2009 Share Posted November 1, 2009 obviously the tach generator is self powered, but does it generate an AC current to power the dial or does it possibly use DC. My pubs don't really address it. The brush plate interaction on the pickup is normally a DC characteristic, but i can't help but say it's AC. thanks for any help. Quote Link to comment Share on other sites More sharing options...
RZHill Posted November 2, 2009 Share Posted November 2, 2009 A/C. voltage. Quote Link to comment Share on other sites More sharing options...
pjvr99 Posted November 2, 2009 Share Posted November 2, 2009 AC signal of around 20volts. 70Hz = 100% Quote Link to comment Share on other sites More sharing options...
tinyclark Posted November 2, 2009 Share Posted November 2, 2009 3.6.3 Voltage output. The output voltages shall be 21 ± 0.5 when operated at a drive shaft speed of 4,200 rpm and connected to a load consisting of three 40-ohm, Y-connected resistances. None of the output voltages shall be less than 3.5 when operated at a drive shaft speed of 1,000 rpm and connected to a load consisting of three 20-ohm, Y connected resistances. Frequency is directly proportional to turning speed. Quote Link to comment Share on other sites More sharing options...
GACFaja Posted November 2, 2009 Share Posted November 2, 2009 3.6.3 Voltage output. The output voltages shall be 21 ± 0.5 when operated at a drive shaft speed of 4,200 rpm and connected to a load consisting of three 40-ohm, Y-connected resistances. None of the output voltages shall be less than 3.5 when operated at a drive shaft speed of 1,000 rpm and connected to a load consisting of three 20-ohm, Y connected resistances. Frequency is directly proportional to turning speed. That's some handy info--and info that we can't get hold of any more on the line. Do you have something like this for TIT or Fuel Flow? I remember on C-141's, we had a synchro tester that we could use to check out fuel flow and another tester that we could use for EGT. Just a matter of putting in the right settings. On the 130, we have to do an engine run to op check them. Quote Link to comment Share on other sites More sharing options...
ArcticFox Posted November 2, 2009 Share Posted November 2, 2009 there is a 4:1 ratio between frequency of the AC gen and Tach. 100% RPM = 400 Hz. Quote Link to comment Share on other sites More sharing options...
bischoffm Posted November 3, 2009 Share Posted November 3, 2009 Go to this web site and type the mil spec NUMBER (only) in the document number block and you will get all kinds of info on your gauges. Mil-I-27552 for TIT and Mil-I-25324 Fuel Flow http://assist.daps.dla.mil/quicksearch/ good luck Quote Link to comment Share on other sites More sharing options...
Steve1300 Posted November 3, 2009 Share Posted November 3, 2009 there is a 4:1 ratio between frequency of the AC gen and Tach. 100% RPM = 400 Hz. I think you will find that technically, 100% RPM is 398 hz. Quote Link to comment Share on other sites More sharing options...
tinyclark Posted November 3, 2009 Share Posted November 3, 2009 398 is good enough for government work. Quote Link to comment Share on other sites More sharing options...
ArcticFox Posted November 3, 2009 Share Posted November 3, 2009 Can you explain the 2hz difference?? Is it a matter of just real world vs theoretical? Quote Link to comment Share on other sites More sharing options...
bischoffm Posted November 4, 2009 Share Posted November 4, 2009 Theroretically real world!! I challange the freq meter on the Herk to find those missing 2 HZ's they could be anywhere!!! Like Tiny, said good enough for govment work! Quote Link to comment Share on other sites More sharing options...
GACFaja Posted November 5, 2009 Share Posted November 5, 2009 Go to this web site and type the mil spec NUMBER (only) in the document number block and you will get all kinds of info on your gauges. Mil-I-27552 for TIT and Mil-I-25324 Fuel Flow http://assist.daps.dla.mil/quicksearch/ good luck That's awesome! Thanks! Quote Link to comment Share on other sites More sharing options...
victorp1 Posted November 6, 2009 Share Posted November 6, 2009 Engine generator frequency is determined as follows: T56 series III engine generator speed = 5,965 RPM Engine generator poles = 8 The constant 60 is used to convert RPM to revolutions per second (RPS) and each pole has two ends (60 x 2). (No. of poles x rpm) / (60 x 2) = Frequency (8 x 5,965) / 120 = 397.66 Frequency This should let you know what happened to the other 2 hertz. I have a hard time seeing 2 hertz on that meter. Vic OAE Quote Link to comment Share on other sites More sharing options...
ArcticFox Posted November 6, 2009 Share Posted November 6, 2009 Vic - you rock. Also - I think I've seen that penguin before...somewhere. Quote Link to comment Share on other sites More sharing options...
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