| Author | Message | ||
| Jerry Liebler (Jerry_liebler)
Rating: |
I just installed a Stewart Warner tach and found that the information I got off of this board was incorect. The 50 DN alternator is aparently a 4 pole device, not 6 poles as an old post says. Since my alternator is gear driven with a 2.93 speed up ratio 11.7 pulses per revolution is corect. Regards Jerry 4107 1120 | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Rating: N/A |
Hi Jerry I believe it was I who posted the 50DN pulse info here's a copy of the info I posted "For Detroit Diesel Delco gear driven 50DN 270 Amp 24 volt alternators "R" terminal hookup (2.93 gears x 3 pole stator x 2 (full wave rectified) = 17.58 pulses/rev) - The "R" terminal output is 12 volt" HMMMMMMM Open - up a 50DN or look in the maintainence manual - there are SIX diodes on the back plate - logically then only 6 pulse per rev ????????? perhaps you can verify your tach by---> using 12 volt A/C transformer with an unfiltered full wave rectifier to test - 60 cycles via a full wave bridge=120 pules/sec. a tach set at 11.7 pulses / rev should read 615 rpms - (120pps X 60sec / 11.7ppr = 615 rpms) I would sure like to get to the bottom of this - and understand and/or correct the info Pete RTS/Daytona | ||
| mel 4104 Rating: N/A |
jerry most of us up here have changed out the SW tack. for the ISSPRO which is made in portland Or. and is far better than the SW. they have great back up to their tacks where as SW never seemed to care once you bought their gauge. i have an SW that has less than 500 miles of use on it before it went haywire which was the second one that i got in 6 months but never again.the isspro is very easy to install and has been trouble free for 8 years. | ||
| Jerry Liebler (Jerry_liebler)
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Pete, There are six diodes because it is a 3 phase machine. Only one of the phases is, however, connected to the 'r' terminal. The output on the 'r' terminal is a half wave rectified sinusoid (also called a haversine) from one phase. I verified the tach's operation with the dip switches set for 17.6 pulses/rev., using a pulse generator and counter, before installing it. However it only showed about 1500 RPM at the governor and I know from the speeds I travel and my gear ratios that my gov. is set near 2300. I reset the dip switches for 11.7 pulses/rev. (the value for a 4 pole machine) and rechecked with the pulse generator/counter then reinstalled. It now works like it's supposed to. Regards Jerry 4107 1120 | ||
| Steve Zona (Highwayrunner)
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Hi all. reading this post, immediately brings to mind the question. can the r terminal "12volt" be used to charge a twelve volt bank of house batts while going down the road? and how much current would be available? not exactly on topic , but really would like to know. any input appreciated. and thanks to all who have already helped in the past , our bus is coming along really well. Steve and Cindi 82mc9 | ||
| Jerry Liebler (Jerry_liebler)
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Steve, Using the 'r' terminal on a 24 volt alternator to charge a 12 volt battery is a very BAD idea. What is present on that terminal is, as I said previously, is a haversine that spends half the time about 0.7 volt negative while the other half is 1/2 of a sine wave with a peak level of about 0.7 volt more positive than the battery voltage. While it's technically DC with an average value of about 12 volts, it's peak voltage is a diode drop more positive than the 24 volt battery. This would seriously overcharge a 12 volt battery. Best to forget the 'r' terminal and get an equalizer or 2 to charge the 12 house battery from the alternator. The other option is add a 12 volt alternator. Regards Jerry 4107 1120 | ||
| Jerry Liebler (Jerry_liebler)
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Pete, I just checked my 4107 maint manual & it says the alternator drive ratio is 2.29-1 this makes my setup wrong again as I used your 2.93. I now think the 50 DN is a 12 pole alternator as this seems to give the correct reading. Pulses/rev = drive ratio X # of poles/2 = 13.7. I had to know for sure so I contacted the company that I got the stator for my alternator from (Faulkner electric of Portland Or.) and they were kind enough to verify that the 50 DN has indeed a 12 pole rotor. So the gospel is 2.29 X 12/2= 13.74 pulses/rev. Regards Jerry 4107 1120 | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
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Jerry My RTS manual shows 2.93 gear ratio ????? Pete | ||
| Jerry Liebler (Jerry_liebler)
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Pete, Is it an 8v71?, the ratio may be different for the 6v92. In any event the 50 DN is a 12 pole machine which produces 6 pulses per revolution on the 'r' terminal. Regards Jerry 4107 1120 | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
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I have a 6V92TA DDEC 2 what is your engine ?? | ||
| Jerry Liebler (Jerry_liebler)
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Pete, I think we've found the difference. My engine is an 8v71n. But I'm far from sure that all gear driven alternators on 8v71s have the same ratio. Regards Jerry 4107 1120 | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
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seems it may even get worse 2.94 vs 2.75 vs 2.29 see--> http://extranet.detroitdiesel.com/public/sibs/sibs/3-92-99.pdf Pete RTS/daytona | ||
| Craig (Ceieio)
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Back in my farming days, we would set up our combines using shaft tachometers. This was a hand held tach that you pushed against the center of a shaft and read the RPM directly. I wonder if one can be rented affordably and used on a DD. This way the actual crank RPM at idle could be read and used to dial in the tach. These buses have had many hands give them loving care over the years, so who knows what really is going to be found. In my case, my bus as an air tensioned triple belted drive on the alternator, so I can at least figure ratios from the pulley sizes (I think!!). Craig - MC7 Oregon | ||
| Jerry Liebler (Jerry_liebler)
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Pete, Interesting that the 6v92 can have different alternator drive ratios. I just checked my parts manual for the 4107 & it shows the alternator drive gears as 55 tooth (on the camshaft) and 24 tooth (on the alternator. 55/24 = 2.291666 So I do believe I have a 2.29 ratio. Regards Jerry 4107 1120 | ||
| Stan Rating: N/A |
Craig: The Stewart Warner hand tach is still available for about $65.00. Sales have probably gone to near zero since the electronic (non contact) tachs came on the market for about $80.00. But your suggestion is a good one. It is easier to adjust the tach to the engine speed than counting teeth on internal gears. My only experience with a tach with DIP switches was a Motorola and the switches were just a binary counter, so easy to adjust to the actual engine speed. Other tachs that I have worked on used a trim pot in the analog output to the meter head. | ||
| Sammy (Sammy)
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12volt and 24 volt 50 DN Altenators have different drive gears.Hope this might help. | ||
| t gojenola
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The great thing about the ISSPRO alternator tach is that it doesn't care what your drive ratios are. It has a buit in potentiometer to make any adjustments. Beg, borrow, or steal a laser or infrared tach, take a crankshaft reading and adjust the isspro to match. On my 4106 this took one adjustment only at about 1200 rpm and the readings were then identical at any rpm I chose to check it. Simple, and took about 5 minutes. tg tg |
