Tach needle spinning
- Thread starter barbergreg
- Start date
My b8200 is not gray market an cable drive
Sent from my SAMSUNG-SM-G890A using Tapatalk
Both my M9 and my 105X are also cable drive and my tach's on both have always jumped a bit. I ignore it.
Have very little electrical / electronic stuff on either and that is fine with me. Been my experience that that stuff tends to fail at the worst times.
Had a jumpy cable or tachometer head on my IH this summer, so BOTH were replaced. After 38 years owning this tractor, it is weird to look at the tach and see five operating hours.
There was no way to advance the clock to reflect the 1285 true hours. Parts were OEM and new tech is identical to original. Believe, tongue in cheek, a tach , gear type w/ Gear hour meter, should last at least 40 years.
There was no way to advance the clock to reflect the 1285 true hours. Parts were OEM and new tech is identical to original. Believe, tongue in cheek, a tach , gear type w/ Gear hour meter, should last at least 40 years.
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Mechanical tachs are "eddy current" drive. A cup surrounding a spinning magnet or vice versa. The clearances are small. Rust can bind up the mechanism effectively coupling the two moving parts. Unfortunately, the resisting clock spring is always destroyed when this happens. Just about un repairable without specialized parts, equipment and knowledge.
Buy a new tachometer display unit.
Oh, the hour meter is a separate device that may be FUBAR as well.
Buy a new tachometer display unit.
Oh, the hour meter is a separate device that may be FUBAR as well.
rbargeron
Well-known member
Lifetime Member
Equipment
L5450, L48, L3250, L345 never enough attachments
In mechanical tachs, the cable drives a spinning magnet. The needle has a driven disk, air gap, and a spiral return spring. As the cable spins, the magnet rotates the needle against the spring.
If the spring breaks, the needle just spins with the cable/magnet. A clockmaker can fit a new spring but a replacement unit is cheaper.
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Never knew how they worked. Interesting. I'm old but still learning new stuff.
Why do mine both jump a little when the engines are idling but smooth out as the RPM increase ??
Why do mine both jump a little when the engines are idling but smooth out as the RPM increase ??
rbargeron
Well-known member
Lifetime Member
Equipment
L5450, L48, L3250, L345 never enough attachments
At low rpm the angular speed of the flex shaft at the meter end may oscillate a bit. As rpm goes up, the tiny differences within each revolution tend to damp out. In all rotating balanced mechanisms, the true zero state is illusive.