View Full Version : Engine Hours vs. clock hours ???

08-11-2000, 08:20 PM
Okay may be a foolish question but here goes:

I got into an arguement today with a buddy trying to convince him that equipment running hours are different than just an hour on a clock of run time. I think I'm right, pretty damn sure at least, but why, and how??

He'll believe me once I can back it up with some real explanation. I figure it has something to do with what RPM's your running at, and maybe counts hours my the firing pattern?? Thanks in Advance guys!!

08-11-2000, 08:31 PM
Guido, you need a war to fight.:)

08-11-2000, 08:40 PM
Charles I know, we're a bunch of construction workers getting antsy (spelling) sitting around the shop doing equipment maintenance. It came up while we were arguing about why he didn't change the oil in a bobcat after I told him to do it for a week now. He used it as an excuse, but I'm curious now so I can back it up if it ever comes up again. I don't know if we need another war, but I guess we can go take over a small country or something, I don't know just something to do!! Just kidding!!

08-11-2000, 10:47 PM
An hour is an hour, doesnt matter to the equipment whether its at full governor stop or at idle. The clock starts when the ignition is on (or the magneto becomes energized) and stops when the key is off. Unless you happen to be from Springfield IL and have a custom Ferris ;)

08-11-2000, 10:55 PM
TLG- You beat me to it. That brought back some memories.

08-12-2000, 12:46 AM
guido--I'm betting on you but give us the other guys point of view! hey, einstein might have been wrong!


08-12-2000, 01:16 AM

I tend to agree with the others. A hour is an hour. Not dependent on RPM's. I do see where you are coming from though. A person might think that as an engine runs slower, the hourmeter runs slower. And that the faster it runs, the faster the clock.
When I used to be a farmer, I kept time by the hourmeter. Never wore a watch. And it always checked out against the clock in the pickup when the day was done.
As a sidenote, some equipment have two hourmeters. For example combines always have two meters. One for engine time, the other for the threshing machine.

08-12-2000, 01:54 AM
Guido, this is unusual but I disagree with you this time. The same hour meter is on both my mower and the ambulances at work. The meter moves at the same speed idling or driving 75 mph (the truck), it's based on the time the engine is running, not work load or RPMs. If not it would be spinning when we are driving fast!

08-12-2000, 01:59 AM
Not the rpm's (like the electric meter on your house) BUT.... The voltage (through the regulator) CAN affect the hour meter slightly! This happens the same way a tape deck MIGHT play a little bit faster in your CAR than in your neighbor's house or your house, etc. It sounds crazy, but true.

08-12-2000, 09:16 PM
But I still swear that someone told me that when I was a little tyke, and it stuck with me. When I go back to work next week, I'm going to try it on our street sweeper. It has regular milage to track the truck, but an hour meter for the aux. engine. I could swear equip hours were'nt as fast, but I guess I'm wrong. I got an e-mail this morning though from someone here that agrees with me, but is trying to find something in writing. We'll get to the bottom of this!!

08-13-2000, 12:09 AM
I think I know where this might be comming from. in SOME cases there is (or was) an Hr meter that was run off the tach. it showed aprox engine hrs but would run fast at high engine rpm and slow at idle. Most hr meters are clocks and show true hrs that 12 volts is applyed to them.
PS, The hr meter on my Ferris only runs when the pto is on!

08-13-2000, 03:02 AM

I own two Ferris mowers and that's how they are set up from the factory. The amount of running time on and off the trailer is insignificant.

lawrence stone
08-13-2000, 08:39 AM
Not to offend you Ferris guys but that wiring setup is plain piss poor automotive engineering.

I canít believe they would hook up a delicate instrument to a min. of a 3-amp circuit.

Any member of the Society of Automotive Engineers would find this practice unacceptable.

02-16-2001, 02:16 PM
The engine hours would be slower than clock hours only on a mechanical hour meter. My 1960 JD 430 has a mechanical hour meter on the tach that will speed up with engine RPMs. It really makes sense this way as the engine is working harder at high RPMs than if it was idling. Besides, how many of us really leave our equipment idling for hours on end? At the price of fuel, who could afford that? We might end up with a half dozen or so idle hours over the course of a season, that's pretty insignificant.

Regarding Mr. Stone's comment, if the hourmeter is mechanical, then it makes perfect sense that it is only running when the PTO is engaged. As an engineer, I do not find a $30 hour meter near as delicate as a $10,000 hydraulic servo valve. And, wiring an hour meter in parallel to a electric PTO clutch is perfectly okay and does not violate any codes of engineering standards. Sorry Stone, you were reaching with that one. Why are you so bitter anyway?


Eric ELM
02-16-2001, 02:29 PM

You mentioned that you have a 1960 430 JD. I had no idea they made them for 30 years. What engine is in that 1960, the same as my 1990, a Yanmar?

Richard Martin
02-16-2001, 03:08 PM
Runner wrote

! This happens the same way a tape deck MIGHT play a little bit faster in your CAR than in your neighbor's house or your house, etc. It sounds crazy, but true.

It is crazy particularly concerning AC. The rotating speed of any given AC motor (like in the wall clock or your Mix Master) can only be regulated by the cycles (hertz). If voltage controlled rotating speed of AC motors then your wall clock would keep terrible time since AC voltage is constantly going up and down. The voltage and available amperage can control the amount of power a given AC motor has. A AC motor can be wired so that it will rotate at different speeds (like a ceiling fan) but only because the motor is wired (wound) different ways to change the way the cycles are used.

This is the main reason that devices used in Europe (50htz) cannot be used in the U.S.. There is also that little issue of voltage.

02-16-2001, 03:13 PM
Eric, his JD 430 is an old two lunger(2 cylinder) farm tractor. They made a 430, 530, 630, 730, and an 830. These were produced until the mid 60's I think. Thanks, Lynn

02-16-2001, 03:43 PM
Gorrell is right, my tractor is a 2 cylinder, 25hp, utility farm tractor. It was the last year for the 2 cylinders when Deere jumped into the modern era overnight of 4 and 6 cylinders. It has a really unique sound but not the pop -pop of the horizontal Johnnys.


John DiMartino
02-16-2001, 04:05 PM
our Ford 1910 registers hours from cable operated tachometer.an operating hour is only accurate on it when its running at pto speed,which is 2500RPM's.I usually run it at 1800-2000about 9 months of the year,the other 3 months(leaf blower and backhoe)it runs at 2500,so although it says 2600 hrs on the meter,it is more like 35-3800 hrs.I timed an hr mowing with gangs at 1750 rpm's,and it read .6 on the meter,big difference.

02-16-2001, 06:30 PM
The only comment I have on this subject is
thatI dont believe idling an engine is easier
on it than at operational rpm.

02-16-2001, 07:29 PM
i once took a lunch break with a hour meter on a ray-go roller it was a slow day owner of the company dont care on slow days they just want me to get 8 hrs in .
it turned out to be 1 hr for a 1/2 hr break the roller was at a ideal.