BX25 hour meter question

[yawning dog]

Hi folks, this is mostly idle curiousity but I thought I would ask anyway as I didn't see it discussed (sorry if I missed it). On my B21, the hour meter is mechanical, driven by a cable with a rotating core. I don't know for sure, but it seems that the core rotation frequency would be directly influenced by the RPMs of the engine, thereby causing the hour meter to be a function not only of time operating but also RPMs. My guess is that the hour meter therefore is accurate for some specific engine RPM- say 2500. Lower average RPMs for an hour would therefore show less than an hour on the hour meter and higher average RPMs would show more than an hour-elapsed time.

Is this how it works, and if so, does it work this way on newer BX tractors as well? My BX25 has a digital hour meter display so I was wondering if it (a) still worked off a mechanical cable (I don't see one) and (b) if it compensates for engine RPM. Thoughts? Thanks!

 

[GreensvilleJay]

my understanding is that 'old skool' meters are NOT directly coupled, rather the cable spins a magnet that then 'magnetically' spins a disk that drives the 'actual hours counter'. Someone has figured out the correct magnet and inertia mass of the disk to get fairly accurate time.
I could go grab the spare /67 Stang cluster and look, but I have to put a tube in a tire on a rider......

 

[Roadworthy]

My limited experience tells me your observation is correct - on older tractors lower rpm use would result in lower hour meter indication as well as a lower tachometer reading. Newer hour meters seem to run whenever the key is on and do not depend on engine speed. Of course if that's the case they will record hours if the key is left on even if the engine is not running.

 

[yawning dog]

GreensvilleJay, interesting I didn't know that. I don't think that's how the B21 works only because I had to replace the cable and I was able to manually spin the odometer by hand and with a drill prior to doing that to confirm that the meter actually worked. I guess it's possible that there was still a magnet in there but it seemed purely mechanical.

Roadworthy, yes that's exactly why I was wondering and you have a good point- I could just leave the tractor key in the on position for 6 minutes without it running and see if the hour meter advances by 0.1. Maybe I'll try that and see what happens.

I was basically wondering this because it seems that my BX hour meter advances faster than my B21. Without getting into Einstein's relatively (ha ha), I started to think that the BX works doesn't take RPMs into account. From my perspective the B21 techniques (based on RPMs) is a more accurate indication of actual tractor use than just key on, but what do I know. Thanks for your replies!

 

[William1]

Cable driven tachs have a escapement mechanism, like a regular watch. That is what drives the counter. The spinning cable, 'tries' to rotate a disk (much like one in a speedo) that acts like a mainspring but that force is managed by the escapement. So while the disk does rotate, its' speed is managed and no matter the force applied, it rotates as a function of time instead.
Electric 'Hobbs meters' (like on the BX25) usually run when the key is on, engine running or not. Some run only when the vibration of the engine is detected. Mechanical ones run only when the engine is on.

 

[fried1765]

My limited experience tells me your observation is correct - on older tractors lower rpm use would result in lower hour meter indication as well as a lower tachometer reading. Newer hour meters seem to run whenever the key is on and do not depend on engine speed. Of course if that's the case they will record hours if the key is left on even if the engine is not running.

"they will record hours if they key is left on even if the engine is not running"
Exactly what happened with my SCAG zero turn.
I left the key on overnight, and clocked 24 additional "running" hours.

 

[85Hokie]

I bought a boat with a honda engine ........ the hour meter said like 4000 hours or more (cannot remember)

I was under the dash and I kept hearing a ticking ........... the hour meter was hooked STRAIGHT to hot.

that meter ran and probably tripped over that meters lifespan!!!

 

[yawning dog]

85Hokie, maybe they just wanted to let you know how many hours it's been since they installed the hour meter.

 

[whitetiger]

I was basically wondering this because it seems that my BX hour meter advances faster than my B21.

The hour meter on all BX series tractors is excited from the alternator so it only clocks hours when the engine is running.

 

[fried1765]

The hour meter on all BX series tractors is excited from the alternator so it only clocks hours when the engine is running.

Dats good !!!!

 

[Henro]

The hour meter on all BX series tractors is excited from the alternator so it only clocks hours when the engine is running.

I don't mean to dispute your knowledge which is extensive whitetiger , but I seem to remember people saying they forgot the key being on with at least some BX Kubota tractors, and that the hour meter accumulated hours until they turned the key off...

Could be my memory is totally wrong...

Edit: I guess my question would be, how does the hour meter know where the voltage is coming from when the key is on? Don't think there is a switch in the system to tell the hour meter that the alternator/dynamo is turning...again, could be totally off base here...

 

[whitetiger]

I don't mean to dispute your knowledge which is extensive whitetiger , but I seem to remember people saying they forgot the key being on with at least some BX Kubota tractors, and that the hour meter accumulated hours until they turned the key off...

Could be my memory is totally wrong...

Edit: I guess my question would be, how does the hour meter know where the voltage is coming from when the key is on? Don't think there is a switch in the system to tell the hour meter that the alternator/dynamo is turning...again, could be totally off base here...

Think about how a Charge light knows when to illuminate and when to stay off. Leaving the Key Switch in the ON position on a BX series will not clock hours. Having said that, I am not sure if a failure of the regulator could clock hours without the engine running, I have never come across that scenario.

A damaged wiring harness could logically cause the scenario.

 

[GeoHorn]

Tachometers which are cable-driven have horometers which are usually accurate only at one specific RPM. Low RPM equates to lower time recorded….and also resembles the lower wear-rates associated with that lower work….so ”no harm, no foul”. An engine run at higher than normal operating RPMS will suffer greater wear at those higher RPMS…so slightly more time is recorded. The actual error, however, is small.

 

[Henro]

Think about how a Charge light knows when to illuminate and when to stay off. Leaving the Key Switch in the ON position on a BX series will not clock hours. Having said that, I am not sure if a failure of the regulator could clock hours without the engine running, I have never come across that scenario.

A damaged wiring harness could logically cause the scenario.

Well, my brothers name is Thomas, but still I’m a doubting Thomas sometimes and decided to go down and see what my BX2200 does with the key on and the engine not running.

I took a picture of the hour meter before I turned the key on, and I took another picture of the hour meter after six minutes went by. Wouldn’t you know the hour meter incremented 0.1 hours.

So at least some BX tractors do accumulate hours when the key is turned to the on position and the engine is not running.

Just wanted to be sure the record was set straight in case somebody comes upon this thread at a later date.

 

[yawning dog]

Thanks, Henro. I was thinking of trying the same thing. The only other question is then whether the BX compensates for the RPMs. I looked at the WSM and it says the following in relation to the dual function hour meter RPM gauge on the 1st gen BX25:

The IC regulator sends a signal of the engine revolution to the meter. The meter calculates the signal. It changes and indicates the signal to the engine revolution in cooperation with the voltage.

My guess is that this is reference to the RPM function. If I really get motivated, I'll try the 6 min test at idle and 2500 RPM and see if the hour meter has any difference.

 

[whitetiger]

So at least some BX tractors do accumulate hours when the key is turned to the on position and the engine is not running.

I just went out and turned the key switch to ON on my BX2370, leaving it on for 8 minutes. The 1/10s did not advance.
I will have to check some of the earlier BXs as they come in for service.
I was under the impression they would not clock any hours without the engine running which is why the hour meter is powered from the regulator.
The Tachometer is powered from the regulator separately to monitor engine RPMs.

 

[whitetiger]

My guess is that this is reference to the RPM function. If I really get motivated, I'll try the 6 min test at idle and 2500 RPM and see if the hour meter has any difference

The engine hours will clock the same at an idle as it does at WOT.
Older units with a cable drive are only accurate at PTO speed.

 

[Henro]

The Tachometer is powered from the regulator separately to monitor engine RPMs.

On the BX2200 the hour meter is electrically hooked in parallel with the fuel pump, so when the pump is clicking the hour meter is turning.

I bet later models were modified so that an operator forgetting to turn the key fully off would not accumulate phantom operating hours. (Not sure how someone could leave the key on, but I remember reports of some doing this somehow)

 

[whitetiger]

On the BX2200 the hour meter is electrically hooked in parallel with the fuel pump, so when the pump is clicking the hour meter is turning.

I bet later models were modified so that an operator forgetting to turn the key fully off would not accumulate phantom operating hours. (Not sure how someone could leave the key on, but I remember reports of some doing this somehow)

I guess I had not noticed that the early BX tractors were wired so the hour meter was powered from the ACC circuit. I did a quick check and found that it was changed starting with the BX50 series and the BX24.