Tach cable. Long turn or no long turn.

Alex Clark

Registered User

Life Long Alaskan

• Aug 2, 2011

• #1

I had my tach cable go out last week while I was in the middle of doing a float rating... Bad news. But we managed to get it up and going after a day.

Now I have a fairly long cable that makes a big sweeping turn under the panel and enters the tach via a 90 degree angle drive unit.
One AI told me that I should have the long sweeping turn and another told me that I should get a shorter cable and try to go as direct as possible.
Which is correct?

 

NimpoCub

Registered User

Nimpo Lake, BC . . . AKA "the Floatplane Capital o

• Aug 2, 2011

• #2

I'd go with "Another" ... Ask "One" why he likes a too-long cable.

 

P

Paul Heinrich

PARTNER

Illinois & Wisconsin

• Aug 2, 2011

• #3

Ditch the cable and get an electronic unit.

 

behindpropellers

Registered User

NE Ohio

• Aug 2, 2011

• #4

The 90 degree turn adapter reverses the direction of the cable, so it is essential. Sweeping turns are good, really doesn't matter on the length as long as it works correctly.

Tim

 

M

Mush

FRIEND

• Aug 2, 2011

• #5

It's not a bad idea to shoot the prop with an optical RPM sensor as well. I have seen where a small bend can cause as much as a 100rpm reduction. They had the cable shortened so it was straight as possible and the reading was dead on.

 

mike mcs repair

Registered User

chugiak AK

• Aug 2, 2011

• #6

Mush said:

.....I have seen where a small bend can cause as much as a 100rpm reduction. They had the cable shortened so it was straight as possible and the reading was dead on.

Click to expand...

how can that be true?????? unless it was slipping/spinning in fitting on engine end????

or pushing at the tach and and somehow fuxing with the magic in it???

 

Last edited: Aug 2, 2011

mike mcs repair

Registered User

chugiak AK

• Aug 2, 2011

• #7

Alex Clark said:

One AI told me that I should have the long sweeping turn and another told me that I should get a shorter cable and try to go as direct as possible.
Which is correct?

Click to expand...

I always have reeve make them custom to the proper length when doing a panel/rebuild...... but no good reason other than doing the job and gonna do the best I can...

anyway, most all go to the EI electric tach now at rebuild.....

 

T

tempdoug

PATRON

nd

• Aug 2, 2011

• #8

I think Alex has a continental 4 banger in his craft.

 

Alex Clark

Registered User

Life Long Alaskan

• Aug 4, 2011

• #9

Yeap C-90-8

And for those who do not think it makes a difference, you can goof with the tach reading by moving around an unsecured cable while it is running. Strange but true.
The cable is woven in a directional manner and will bind and release in litle spurts while rubbing against the cable housing.
And those 90 degree drive units can either reverse the cable direction or keep it the same. You just pull out the little end unit and install it backwards top make the change.
They are built that way.