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Tach generator question
https://www.warbirdinformationexchange.org/phpBB3/viewtopic.php?f=26&t=47128		 Page 1 of 1
Author:  duncan [ Thu Sep 13, 2012 9:52 am ]
Post subject:  Tach generator question
Just purchased a "clock -style" tach for our TBM Avenger paneal restoration project. This has separate hands for RPMx100 and RPMx1000 and would replace our current single hand tachometer. Both are electrical with a compatible three prong plug. The question is whether there are different tach generators out there, or does "one size fit all"? I am afraid of connecting the new tach and burning out the current tach generator, and causing the airplane to be grounded! No ID numbers are to be found on the "clock style" tachometer.
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Author:  jdankos [ Fri Sep 14, 2012 8:15 am ]
Post subject:  Re: Tach generator question
The tach you have should work fine. I have both types in my plane. I assume it has 3 pins.
Author:  duncan [ Fri Sep 14, 2012 11:17 am ]
Post subject:  Re: Tach generator question
Jdankos - thanks for the reply. I note that you own a T-6/SNJ. I have seen similar tachs installed in these. I am not 100% sure the tach-generator setup for the T-6 w/ PW R1340 is the same as for the TBM Avenger w/ CW R2600. That is why I asked this group. Sure, the plug matches, and I can quickly check its operation by plugging it in, but on electrical matters I can just as quickly destroy something (tach) which is required for legal flight, besides safety. I'd rather have some documentation or assurances that it will work before I go just plugging it in.
Author:  gschwartz [ Fri Sep 14, 2012 5:23 pm ]
Post subject:  Re: Tach generator question
I'm not an instrument expert however, reviewing a G. E. DC Selsyn Remote-Indicating Aircraft Instrument product guide dated August 1942, the pictured instrument is a Type DJ-13 indicator. The guide further states the following:
"The Type DJ-13 indicator is available in either the sensitive two-pointer type or the non-sensitive single-pointer type. The Type CM-5 generator can be supplied for pad mounting or for screw mounting, the screw mounting being integral with the end shield. The Type CM-7 generator has the same electrical characteristics as the Type CM-5, but is provided with a screw mounting of the swivel-nut type.
Any of the generators can be used to operate any of the indicators and, in all cases, two indicators can be operated in parallel from a single gernerator."

Your choice but this seems like a safe bet if you have GE equipment. I can fax this to you if you wish.
Author:  duncan [ Sat Sep 15, 2012 8:52 am ]
Post subject:  Re: Tach generator question
Thank you Schwartz! I feel much more comfortable now. My private fax number is 970-921-3456 and I'd like to have a copy of that guide.

I just downloaded an $8 iPhone app called "Engine RPM". It is a digital tachometer which senses cylinder firing sound to determine RPM. It can handle the 14 cylinders, and also has ability to factor in the 16:9 reduction gearing for the prop. I am going to try this out and will report back its accuracy as compared to an optical tach as I check the newly acquired "clock-style" tach for its accuracy and usability. Then there will be my "pilot brain re-training" which might prove more difficult than swapping the two tachometers! :D
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