Hour meter question

[Cliff_Johns]

There are two types of hour meter (that I know of). One simply shows the number of hours the tractor engine is operating. The second shows some percentage of the actual time, based on some calculation related to the engine speed required to run the PTO at the full 540 (or what ever the standard is for that tractor.)

Question 1: Which one is considered a HOBBS(sp?) meter.

Question 2: What is the calculation required to translate hours shown on the tractor to hours of engine use for the second type of meter? Is it a linear, that is a direct, relationship to the engine speed percentage of PTO speed? something like (Actual RPM/PTO RPM) * clock time? I could also imagine a calculation like ( (Actual - slow idle) / (PTO - slow idle) ) * clock time or something like that.

Just wondering how many hours my tractor has actually run since it's pretty clear that my JD has the second type of meter.

Cliff

 

[KennyV]

Hobbs meter is an hour meter, have it on 60 minuets it will show an increase of 1 Hr....

Most tractor hours are like you stated; at a rated speed.

If your engine needs to run at 2800 rpm to provide 540 pto speed, you would have to let it idle 4 hours at 700 rpm for the hr meter to show 1 hr additional time. KennyV.

 

[OrangeGuy]

I believe the Hobbs hourmeters are all electric. They are either on or off. It doesn't matter what the engine speed is. They simply add hours based on the clock.

Old tractors like my Allis Chalmers D14 have a cable driven hourmeter run off the distributor. Lowering the engine speed will slow down the hourmeter. Less hours at lower engine speeds.

OrangeGuy

 

[MMM]

Mu hour meter is run from tach (magnetic pickup)and get it's info from engine rpms and is prportional to engine speed.

 

[texastomtom]

hobbs = actual operating time

tach hours = number hours at given (rated) rpm
in effect the tach hours actually is a count of the number of revolutions of the engine....

we have both on aircraft in most cases


the hobbs is usually actuated by any oil pressure switch being on.....


the airframe hobbs meter is generally higher than the count on any one of the engines...


same goes for tractor

 

[BB_TX]

For the hour meters based on running at rated PTO speed, there is no way to translate that into actual engine hours. That type meter is basically the same as an odometer, the faster you go, the faster the meter turns. If a car had 10,000 miles on it, the actual engine hours would be much different if it had been driven 20 mph vs 70 mph. Same with the tractor hour meter. If you had owned the tractor since new and knew how you operated it, you could guess an average engine speed, translate that to a % rated PTO speed, and work up an approximate engine hour number. Except when mowing, I run mine at considerably less than rated PTO most of the time.

 

[Cliff_Johns]

</font><font color="blue" class="small">( If you had owned the tractor since new and knew how you operated it, you could guess an average engine speed, translate that to a % rated PTO speed, and work up an approximate engine hour number.)</font>

This is what I planned to do. I just wanted to make sure it made sense.

Thanks for the info everyone.

Cliff

 

[markct]

why are you concerned about it anyhow?

 

[Cliff_Johns]

</font><font color="blue" class="small">( why are you concerned about it anyhow? )</font>

Not concerned, just curious. It's not a big deal, but I wondered about how many hours of tractor time it took to do the work I did this summer. Nothing more.

Cliff

 

[755inNY]

Hobbs is a brand name not a type of meter. Hobbs makes hours meters (both DC and AC) as well as key switches, pressure switches, lighting and controls.

Jeff