Can cable drive tachs be re-calibrated???

Alex Clark

Registered User

Life Long Alaskan

• Feb 1, 2017

• #1

My mechanical tach reads low. ( which explains why one previous owner kept goofing around with different prop pitches. )

It reads 200rpm low at lower power settings and 165-170 rpm low above 2,000 rpm. I have tested it against two electronic tachs.

Is there a way to re-calibrate the mechanical tach ?

 

N

N86250

Registered User

Elizabeth, WV

• Feb 1, 2017

• #2

Long ago before I learned only instrument shops were supposed to work on instruments, I opened a tach. On that one there was a lever that adusted the tension on a spring. It was similar to the little lever on a wind up alarm clock that adusts faster-slower only the tach was much bigger. Of course I moved the lever and then realized I had no idea where it belonged. A machinist friend helped me set it right with his instruments and a drill press. The tach indicated twice the speed of the drill shaft. jrh

 

mike mcs repair

Registered User

chugiak AK

• Feb 1, 2017

• #3

We had a mechanic that lost his license for redoing compass gaskets and fluid. Best to send it to instrument shop.

 

Alex Clark

Registered User

Life Long Alaskan

• Feb 1, 2017

• #4

Now the question is, which is less expensive, ,,, sending it in for re-calibration or just buying a yellow tagged tach???
I suppose a correction card next to the tach would be a wee bit tacky...

 

KJC

FRIEND

Clear Lake, MN

• Feb 1, 2017

• #5

I have one that needs to go in. Any suggestions for a shop to send it to?

 

P

PIPER J5.5

FRIEND

corvallis,or

• Feb 1, 2017

• #6

Keystone Instruments
507-748-7083 ask for ken

 

skywagon8a

MEMBER

SE Mass MA6

• Feb 2, 2017

• #7

mike mcs repair said:

We had a mechanic that lost his license for redoing compass gaskets and fluid. Best to send it to instrument shop.

Click to expand...

Mike that mechanic must have done something else to annoy the inspector besides just changing compass gaskets. When I went to A&P school we were taught how to do it and it is something that was regularly done in shops where I worked.

 

WhiskeyMike

MEMBER

West Boxford MA

• Feb 2, 2017

• #8

Rudy Instruments in Rudy Arkansas has been very good to me. Quick turn around and moderate prices. I haven't sent them a tach but Im going to. Found I was turning 2,700 with an MT 210 and rattling the windows, while it indicated 2,600. Fiddled with governor adjustments and wasted a load of time and effort to fix a non- problem.

 

B

bob turner

Registered User

• Feb 2, 2017

• #9

San Diego Speedo-Tach used to do them, supplying a calibration card and resetting the total hours to whatever we wanted. Wish they were still here.